Testing the use of bulk organic δ13C, δ15N, and Corg:Ntot ratios to estimate subsidence during the 1964 great Alaska earthquake

USGS Publications Warehouse

Bender, Adrian M.; Witter, Robert C.; Rogers, Matthew

2015-01-01

During the Mw 9.2 1964 great Alaska earthquake, Turnagain Arm near Girdwood, Alaska subsided 1.7 ± 0.1 m based on pre- and postearthquake leveling. The coseismic subsidence in 1964 caused equivalent sudden relative sea-level (RSL) rise that is stratigraphically preserved as mud-over-peat contacts where intertidal silt buried peaty marsh surfaces. Changes in intertidal microfossil assemblages across these contacts have been used to estimate subsidence in 1964 by applying quantitative microfossil transfer functions to reconstruct corresponding RSL rise. Here, we review the use of organic stable C and N isotope values and Corg:Ntot ratios as alternative proxies for reconstructing coseismic RSL changes, and report independent estimates of subsidence in 1964 by using δ13C values from intertidal sediment to assess RSL change caused by the earthquake. We observe that surface sediment δ13C values systematically decrease by ∼4‰ over the ∼2.5 m increase in elevation along three 60- to 100-m-long transects extending from intertidal mud flat to upland environments. We use a straightforward linear regression to quantify the relationship between modern sediment δ13C values and elevation (n = 84, R2 = 0.56). The linear regression provides a slope–intercept equation used to reconstruct the paleoelevation of the site before and after the earthquake based on δ13C values in sandy silt above and herbaceous peat below the 1964 contact. The regression standard error (average = ±0.59‰) reflects the modern isotopic variability at sites of similar surface elevation, and is equivalent to an uncertainty of ±0.4 m elevation with respect to Mean Higher High Water. To reduce potential errors in paleoelevation and subsidence estimates, we analyzed multiple sediment δ13C values in nine cores on a shore-perpendicular transect at Bird Point. Our method estimates 1.3 ± 0.4 m of coseismic RSL rise across the 1964 contact by taking the arithmetic mean of the differences (n = 9) between reconstructed elevations for sediment above and below the 1964 earthquake subsidence contact. This estimate compares well with independent subsidence estimates derived from post-earthquake leveling in Turnagain Arm, and from microfossil transfer functions at Girdwood (1.50 ± 0.32 m). While our results support the use of bulk organic δ13C for reconstructing RSL change in southern Alaska, the variability of stable isotope values in modern and buried intertidal sediment required the analysis of multiple samples to reduce error.

Vertical migration of fine-grained sediments from interior to surface of seabed driven by seepage flows-`sub-bottom sediment pump action'

NASA Astrophysics Data System (ADS)

Zhang, Shaotong; Jia, Yonggang; Wen, Mingzheng; Wang, Zhenhao; Zhang, Yaqi; Zhu, Chaoqi; Li, Bowen; Liu, Xiaolei

2017-02-01

A scientific hypothesis is proposed and preliminarily verified in this paper: under the driving of seepage flows, there might be a vertical migration of fine-grained soil particles from interior to surface of seabed, which is defined as `sub-bottom sediment pump action' in this paper. Field experiments were performed twice on the intertidal flat of the Yellow River delta to study this process via both trapping the pumped materials and recording the pore pressures in the substrate. Experimental results are quite interesting as we did observe yellow slurry which is mainly composed of fine-grained soil particles appearing on the seabed surface; seepage gradients were also detected in the intertidal flat, under the action of tides and small wind waves. Preliminary conclusions are that `sediment pump' occurs when seepage force exceeds a certain threshold: firstly, it is big enough to disconnect the soil particles from the soil skeleton; secondly, the degree of seabed fluidization or bioturbation is big enough to provide preferred paths for the detached materials to migrate upwards. Then they would be firstly pumped from interior to the surface of seabed and then easily re-suspended into overlying water column. Influential factors of `sediment pump' are determined as hydrodynamics (wave energy), degree of consolidation, index of bioturbation (permeability) and content of fine-grained materials (sedimentary age). This new perspective of `sediment pump' may provide some implications for the mechanism interpretation of several unclear geological phenomena in the Yellow River delta area.

A regression approach to the mapping of bio-physical characteristics of surface sediment using in situ and airborne hyperspectral acquisitions

NASA Astrophysics Data System (ADS)

Ibrahim, Elsy; Kim, Wonkook; Crawford, Melba; Monbaliu, Jaak

2017-02-01

Remote sensing has been successfully utilized to distinguish and quantify sediment properties in the intertidal environment. Classification approaches of imagery are popular and powerful yet can lead to site- and case-specific results. Such specificity creates challenges for temporal studies. Thus, this paper investigates the use of regression models to quantify sediment properties instead of classifying them. Two regression approaches, namely multiple regression (MR) and support vector regression (SVR), are used in this study for the retrieval of bio-physical variables of intertidal surface sediment of the IJzermonding, a Belgian nature reserve. In the regression analysis, mud content, chlorophyll a concentration, organic matter content, and soil moisture are estimated using radiometric variables of two airborne sensors, namely airborne hyperspectral sensor (AHS) and airborne prism experiment (APEX) and and using field hyperspectral acquisitions by analytical spectral device (ASD). The performance of the two regression approaches is best for the estimation of moisture content. SVR attains the highest accuracy without feature reduction while MR achieves good results when feature reduction is carried out. Sediment property maps are successfully obtained using the models and hyperspectral imagery where SVR used with all bands achieves the best performance. The study also involves the extraction of weights identifying the contribution of each band of the images in the quantification of each sediment property when MR and principal component analysis are used.

Biogeochemistry of the coupled manganese-iron-sulfur cycles of intertidal surface sediments

NASA Astrophysics Data System (ADS)

Bosselmann, K.; Boettcher, M. E.; Billerbeck, M.; Walpersdorf, E.; Debeer, D.; Brumsack, H.-J.; Huettel, M.; Joergensen, B. B.

2003-04-01

The biogeochemistry of the coupled iron-manganese-sulfur-carbon cycles was studied in temperate intertidal surface sediments of the German Wadden Sea (North Sea). Coastal sampling sites include sand, mixed and mud flats with different organic matter and metal contents and permeability reflecting different hydrodynamic regimes. The field study focusses on the influence of temperature, organic matter load, and sediment types on the dynamics of biogeochemical reactions on different time scales (season, day-night, tidal cycles). One of the main interests was related to the cycling of metals (Mn, Fe) in relation to the activity of sulfate-reducing bacteria. Pore water profiles were investigated by sediment sectioning and high resolution gel sampling techniques. Microbial sulfate reduction rates were measured using radiolabeled sulfate with the whole core incubation technique and the spatial distribution of bacterial activity was visualised by using "2D-photoemulsion-monitoring technique". The biogeochemical sulfur cycle was additionally characterised by the stable isotope ratios (S,O) of different sulfur species (e.g., SO_4, AVS, pyrite). Element transfers (metals, nutrients) across the sediment-water interface were additionally quantified by the application of benthic flux chambers. Microbial sulfate reduction was generally highest in the suboxic zone of the surface sediments indicating its potential importance for the mobilization of iron and manganese. In organic matter poor permeable sediments tidal effects additionally influence the spatial and temporal distribution of dissolved redox-sensitive metals. In organic matter-rich silty and muddy sediments, temperature controlled the microbial sulfate reduction rates. Depth-integrated sulfate reduction rates in sandy sediments were much lower and controlled by both temperature and organic matter. Formation of anoxic sediment surfaces due to local enhanced organic matter load (so-called "black spots") may create windows of an increase flux of metals, nutrients and hydrogen sulfide. Acknowledgements: The study was supported by German Science Foundation within the DFG-research group "BioGeoChemistry of the Waddensea" and Max Planck Society.

The Research of Correlation of Water Surface Spectral and Sediment Parameters

NASA Astrophysics Data System (ADS)

Li, J.; Gong, G.; Fang, W.; Sun, W.

2018-04-01

In the method of survey underwater topography using remote sensing, and the water surface spectral reflectance R, which remote sensing inversion results were closely related to affects by the water and underwater sediment and other aspects, especially in shallow nearshore coastal waters, different sediment types significantly affected the reflectance changes. Therefore, it was of great significance of improving retrieval accuracy to explore the relation of sediment and water surface spectral reflectance. In this study, in order to explore relationship, we used intertidal sediment sand samples in Sheyang estuary, and in the laboratory measured and calculated the chroma indicators, and the water surface spectral reflectance. We found that water surface spectral reflectance had a high correlation with the chroma indicators; research result stated that the color of the sediment had an very important impact on the water surface spectral, especially in Red-Green chroma a*. Also, the research determined the sensitive spectrum bands of the Red-Green chroma a*, which were 636-617 nm, 716-747 nm and 770-792 nm.

Comparison of the evolution of the sediment dynamics of a bay and an estuary in the East coast of the English Channel: the case of the Bay of Somme and the Seine estuary (France)

NASA Astrophysics Data System (ADS)

Cuvilliez, A.; Le Bot, S.; Michel, C.; Cuvilliez, C.

2017-12-01

The economical roles and the ecological importance of the intertidal zones of mouth the Seine estuary (25 Km²) and of the Bay of Somme (70 Km²), both located on the East coast of the English Channel (Fig. 1A and Fig. 1B), have led to numerous studies on sediment dynamics since the beginning of the 19th century. Since 1995, the high resolution remote sensing (8 cm per side of pixel) allowed an exhaustive study of these intertidal surfaces. Altimetric surveys using radials, notably with ALTUS altimeters, then with LiDAR, were carried out in order to estimate more accurately the volumes and the nature of the sediments that infill these areas. The study of sedimentary facies further improved our understanding of the roles of the environmental forcing which controls sedimentation dynamics. Indeed, it allows foreseeing hydraulic circulation issues which damage these coastal ecosystems, and which can thus be prevented. Subsequently, for more than a decade, these two macrotidal zones, which have a tidal range equal to or greater than 8.5 m, show a decrease in their settling surface size which fosters mud deposition, and an acceleration of their sand infilling. Since 2005, year that marks the completion of the work of the so-called "Port 2000" harbour, the Seine estuary has increased its intertidal areas by almost 45% (<+7.5 m) (Fig.1C), of which 69% are occupied by sandy or silty sediments brought by the flood tides. In the Bay of Somme, only the low-lying intertidal areas (<+ 3.5m) are infilled with sandy sediments, representing 88% of the total deposits (Fig. 1D). In this case, the study of the sedimentary facies reveals that the littoral drift and the action of the waves linked to the tide are mainly responsible of the infill. If sedimentary infilling is a widespread characteristic of estuaries and bays which started with the Holocene transgression, this phenomenon is accentuated with the sea level rise and is greatly amplified with port developments that tend to limit the action of the river flow.

Transport processes in intertidal sand flats

NASA Astrophysics Data System (ADS)

Wu, Christy

2010-05-01

Methane rich sulfate depleted seeps are observed along the low water line of the intertidal sand flat Janssand in the Wadden Sea. It is unclear where in the flat the methane is formed, and how it is transported to the edge of the sand flat where the sulfidic water seeps out. Methane and sulfate distributions in pore water were determined along transects from low water line toward the central area of the sand flat. The resulting profiles showed a zone of methane-rich and sulfate-depleted pore water below 2 m sediment depth. Methane production and sulfate reduction are monitored over time for surface sediments collected from the upper flat and seeping area. Both activities were at 22 C twice as high as at 15 C. The rates in sediments from the central area were higher than in sediments from the methane seeps. Methanogenesis occurred in the presence of sulfate, and was not significantly accelerated when sulfate was depleted. The observations show a rapid anaerobic degradation of organic matter in the Janssand. The methane rich pore water is obviously transported with a unidirectional flow from the central area of the intertidal sand flat toward the low water line. This pore water flow is driven by the pressure head caused by elevation of the pore water relative to the sea surface at low tide (Billerbeck et al. 2006a). The high methane concentration at the low water line accumulates due to a continuous outflow of pore water at the seepage site that prevents penetration of electron acceptors such as oxygen and sulfate to reoxidize the reduced products of anaerobic degradation (de Beer et al. 2006). It is, however, not clear why no methane accumulates or sulfate is depleted in the upper 2 m of the flats.

Burrowing inhibition by fine textured beach fill: Implications for recovery of beach ecosystems

NASA Astrophysics Data System (ADS)

Viola, Sloane M.; Hubbard, David M.; Dugan, Jenifer E.; Schooler, Nicholas K.

2014-10-01

Beach nourishment is often considered the most environmentally sound method of maintaining eroding shorelines. However, the ecological consequences are poorly understood. Fill activities cause intense disturbance and high mortality and have the potential to alter the diversity, abundance, and distribution of intertidal macroinvertebrates for months to years. Ecological recovery following fill activities depends on successful recolonization and recruitment of the entire sandy intertidal community. The use of incompatible sediments as fill material can strongly affect ecosystem recovery. We hypothesized that burrowing inhibition of intertidal animals by incompatible fine fill sediments contributes to ecological impacts and limits recovery in beach ecosystems. We experimentally investigated the influence of intertidal zone and burrowing mode on responses of beach invertebrates to altered sediment texture (28-38% fines), and ultimately the potential for colonization and recovery of beaches disturbed by beach filling. Using experimental trials in fill material and natural beach sand, we found that the mismatched fine fill sediments significantly inhibited burrowing of characteristic species from all intertidal zones, including sand crabs, clams, polychaetes, isopods, and talitrid amphipods. Burrowing performance of all five species we tested was consistently reduced in the fill material and burrowing was completely inhibited for several species. The threshold for burrowing inhibition by fine sediment content in middle and lower beach macroinvertebrates varied by species, with highest sensitivity for the polychaete (4% fines, below the USA regulatory limit of 10% fines), followed by sand crabs and clams (20% fines). These results suggest broader investigation of thresholds for burrowing inhibition in fine fill material is needed for beach animals. Burrowing inhibition caused by mismatched fill sediments exposes beach macroinvertebrates to stresses, which could depress recruitment and survival at all intertidal zones. Our results suggest use of incompatible fine fill sediments from dredging projects creates unsuitable intertidal habitat that excludes burrowing macroinvertebrates and could delay beach ecosystem recovery. Through effects on beach invertebrates that are prey for shorebirds and fish, the ecological impacts of filling with mismatched fine sediments could influence higher trophic levels and extend beyond the beach itself.

Yaquina Bay, Oregon, Intertidal Sediment Temperature Database, 1998 - 2006.

EPA Science Inventory

Detailed, long term sediment temperature records were obtained and compiled in a database to determine the influence of daily, monthly, seasonal and annual temperature variation on eelgrass distribution across the intertidal habitat in Yaquina Bay, Oregon. Both currently and hi...

Methylmercury production and export from a restored tidal marsh: Crissy Field, Golden Gate National Recreation Area, San Francisco, CA

NASA Astrophysics Data System (ADS)

Windham-Myers, L.; Ward, K.; Marvin-Dipasquale, M. C.; Agee, J.; Kieu, L.; Kakouros, E.

2009-12-01

Well-mixed surface water in the restored salt marsh at Crissy Field, Golden Gate National Recreation Area, was found to have high aqueous methylmercury (MeHg) concentrations (>1 ng MeHg / L), despite its sandy substrate and low sediment total mercury (THg) concentrations. We sought to determine a) the extent to which the marsh was a source or a sink of MeHg to San Francisco Bay, b) where and when MeHg is produced within the marsh, and c) the extent to which MeHg concentrations in sediment and water varied with extended multi-week flooding events, impoundments caused by periodic sediment accumulation in the narrow inlet. Because Crissy Marsh is small in size, has a single inlet slough channel, and has a tidally-dominated water budget, we had a unique opportunity to construct a THg and MeHg flux budget for this single well-constrained wetland. A 24-hour sampling event was conducted over a full diurnal tidal cycle during August 2008. Particulate and filter-passing (0.45μm) THg and MeHg concentrations were assessed, in addition to concentrations of chlorophyll-a and total suspended solids. These measurements were coupled to water flux calculations from a USGS-derived hydrodynamic model based on tidal prism relationships at this site. The resulting Hg load calculations demonstrated that for this 24-hour period, the marsh was a net source of dissolved MeHg to the bay and a net sink of particulate THg from the bay. To determine where and when Hg was being methylated within the marsh environment, sediment percent (%) MeHg (a surrogate measure of MeHg production efficiency) was examined for 2 years along 8 transects, seasonally and across three marsh elevations (subtidal, low-intertidal, and high-intertidal). The low-intertidal zone (cordgrass-dominated) had higher sediment %MeHg than the other two elevations. Sediment %MeHg was also higher during summer than during winter, highest at the sediment surface (0-2cm), correlated with sediment organic content, and elevated during closure events at some intertidal sites, suggesting enhanced MeHg production during impoundment. However, aqueous MeHg concentrations (both filtered and unfiltered) fell during inlet closure events. Additional data suggest that increased algal production and decreased suspended solids (increased water clarity) may remove MeHg from the water column during closure events, either through settling of mineral and algal components or via photodemethylation. We conclude that MeHg production is most active in the low intertidal sediments of Crissy Marsh, and that this spatial trend is driven by both wetting/drying cycles and the comparatively elevated organic matter concentrations in this zone. We further conclude that the mercury present in Crissy Marsh, whether due to historic contamination, atmospheric deposition or tidal loads, is subject to methylation and export as MeHg. At only 18 acres, Hg fluxes between Crissy Marsh and the larger Bay may be small, but the flux dynamics demonstrated here may be representative of semi-enclosed salt marshes elsewhere in San Francisco Bay.

Environmental assessment of polycyclic aromatic hydrocarbons (PAHs) in surface sediments of the Santander Bay, Northern Spain.

PubMed

Viguri, J; Verde, J; Irabien, A

2002-07-01

Samples of intertidal surface sediments (0-2 cm) were collected in 17 stations of the Santander Bay, Cantabric Sea, Northern Spain. The concentrations of polycyclic aromatic hydrocarbons (PAHs), 16, were analysed by HPLC and MS detection. Surface sediments show a good linear correlation among the parameters of the experimental organic matter evaluation, where total carbon (TC) and loss on ignition (LOI) are approximately 2.5 and 5 times total organic carbon (TOC). A wide range of TOC from 0.08% to 4.1%, and a broad distribution of the sum of sigma16PAHs, from 0.02 to 344.6 microg/g d.w., which can be correlated by an exponential equation to the TOC, has been identified. A qualitative relationship may be established between the industrial input along the rivers and the concentration of sigma6PAHs in the sediments of the estuaries: Boo estuary (8404-4631 microg/g OC), Solia-San Salvador estuaries (305-113 microg/g OC) and Cubas estuary (31-32 microg/g OC). This work shows a dramatic change in the spatial distribution in the concentration of PAHs of intertidal surface sediments. The left edge of the Bay has the main traffic around the city and the major source of PAHs is from combustion processes and estuarine inputs, leading to medium values of PAHs in the sediments; the right edge of the Bay has much lesser anthropogenic activities leading to lower values of PAHs in sediments. The distribution of individual PAHs in sediments varies widely depending on their structure and molecular weight; the 4-6 ring aromatics predominate in polluted sediments due to their higher persistence. The isomer ratio does not allow any clear identification of the PAHs origin. Environmental evaluation according to Dutch guidelines and consensus sediment quality guidelines based on ecotoxicological data leads to the same conclusion, sediments in the Santander Bay show a very different environmental quality depending on the spatial position from heavily polluted/medium effects to non-polluted/below threshold effects. These results indicate that local sources of PAHs, especially estuary discharges, lead to very different qualities of sediments in coastal zones, where traffic and industrial activities take place.

Residues of organochlorine pesticides in intertidal flat surface sediments from coastal zone of Jiangsu Province, China

NASA Astrophysics Data System (ADS)

Han, Xiumei; Zheng, Rong; Zhao, Jiale; Ma, Chao; Gao, Xiaojiang

2014-09-01

Sixteen surface sediment samples were collected and analysed to evaluate the residues of organochlorine pesticides (OCPs) from intertidal flat in Jiangsu Province. Overall, 22 OCPs were detected with total concentrations of OCPs ranging widely from 0.96 to 12.14 ng/g (dry wt). Total hexachlorocyclohexane (HCH) and total dichlorodiphenyltrichloroethane (DDT) levels varied from <0.01 to 0.67 ng/g and from 0.23 to 4.85 ng/g, respectively. DDTs were the predominant compounds. The dominance of β-HCH indicated a history of HCH pollution. According to the ratios of ( p, p'-DDD+ p, p'-DDE)/ p, p'-DDT and o,p'-DDT/ p, p'-DDT, new input of DDTs did not occur in most sites, and the main sources were historical usage of technical DDTs. OCPs such as dieldrin, endrin, p, p'-DDD, and p, p'-DDT exceeded the effects range low, showing adverse biological effects that would occasionally occur at some sites of the study area.

Estuarine intertidal sediment temperature variability in Zoster marina and Z. japonica habitats in Yaquina Bay, Oregon

EPA Science Inventory

Physical characterization of intertidal estuarine plant habitats over time may reveal distribution-limiting thresholds. Temperature data from loggers embedded in sediment in transects crossing Zostera marina and Z. japonica habitats in lower Yaquina Bay, Oregon display signific...

Microalgal mediation of ripple mobility.

PubMed

Friend, P L; Lucas, C H; Holligan, P M; Collins, M B

2008-01-01

The interaction between physical and biological factors responsible for the cessation of ripple migration on a sandy intertidal flat was examined during a microalgal bloom period in late winter/early spring, as part of a wider study into the biostabilisation of intertidal sediments. Ripple positions and ripple geometry were monitored, and surface sediment was sampled, at weekly intervals over a 5-week period. Ripples remained in the same position for at least 4 weeks, during which time there was a progressive reduction in bedform height (smoothing) and deposition of some 1.5 cm sediment, mainly in the ripple troughs (surface levelling). The mean chlorophyll a (chl a) sediment content was 6.0 microg gDW(-1) (DW: dry weight) (0-1 mm depth fraction), with a maximum value of 7.4 microg gDW(-1) half way through the bloom. Mean colloidal-S carbohydrate (S: saline extraction) content was 131 microg GE gDW(-1) (GE: glucose equivalent) (0-1 mm), with a maximum of 261 microg GE gDW(-1 )towards the end of the bloom. Important accessory pigments were peridinin (indicative of dinophytes) and fucoxanthin (diatoms). Stepwise multiple regression showed that peridinin was the best predictor of chl a. For the first time, in situ evidence for the mediation of (wave) ripple migration by microalgae is provided. Results indicate that diatoms, and quite possibly dinophytes, can have a significant effect on intertidal flat ripple mobility on a temporal scale of weeks. In addition, microalgal effects appear capable of effecting a reduction in bed roughness on a spatial scale of up to 10(-2 )m, with a subsequent reduction in bottom stress and bed erodability. It is suggested that a unique combination of environmental conditions, in conjunction with the microalgal bloom(s), promoted the initial cessation of ripple movement, and that stationary-phase, diatom-derived extracellular polymeric substances (EPS) (and possibly dinophyte-derived EPS) may have prolonged the condition. It is reasonable to suppose that ripple stabilisation by similar processes may have contributed to ripple mark preservation in the geological record. A conceptual model of sandy intertidal flat processes is presented, illustrating two conditions: (i) a low EPS/microalgae sediment content with low ripple stabilisation and preservation potential; and (ii) a high EPS/microalgae content with higher preservation potential.

[Laboratory simulation study on the influence of resuspension on the release of mercury from Yangtze estuarine tidal flat].

PubMed

Li, Meng; Bi, Chun-Juan; Zhang, Jing-Jing; Lü, Jin-Gang; Chen, Zhen-Lou

2011-11-01

Using a Particle Environment Simulator, laboratory simulation experiment on the influence of resuspension on the release of mercury from sediments collected from medium tidal flat and low tidal flat in Chongming Dongtan was conducted. Results indicated that the conditions of overlying water changed significantly during resuspension. The concentrations of HgD and HgP were mainly in the rang of 0.152-2.657 microg x L(-1), 0.080-2.722 microg x L(-1) separately. In the resuspension processes, mercury was released from the medium intertidal sediments under the salinity condition of 4.1 per thousand, 8.0 per thousand, 10.0 per thousand, 13.0 per thousand, and from the low intertidal sediments under the salinity condition of 13.0 per thousand. However, the release of mercury from the medium intertidal sediments is not significant under the salinity condition of 4.1 per thousand, 8.0 per thousand, 10.0 per thousand. The salinity of overlying water had an important effect on resuspension. In different salinity condition, the release of mercury was different. And the release of mercury from medium tidal flat and low tidal flat was different during the resuspension periods, the release of mercury from the medium intertidal sediment was significantly higher than the release from the low intertidal sediment. When the rotate speed was (210 +/- 5) r x min(-1), the desorption of mercury significantly increased, thereby the rotate speed had an effect on the release of mercury.

NUTRIENT FLUXES IN THE MICROALGAL-DOMINATED INTERTIDAL REGIONS OF THE LOWER YAQUINA ESTUARY, OREGON (USA)

EPA Science Inventory

The effects of benthic microalgae on sediment nutrient fluxes were investigated at three sites across the intertidal zone of lower Yaquina Bay. Study sites were selected where microalgae were present but where seagrass and mud shrimp were absent. Sediment columns were collected...

Destabilization of Cohesive Intertidal Sediments by Infauna

NASA Astrophysics Data System (ADS)

de Deckere, E. M. G. T.; Tolhurst, T. J.; de Brouwer, J. F. C.

2001-11-01

Bioturbation activity was reduced in four plots on an intertidal mudflat in the Humber estuary (UK) during 4 days, by spraying the sediment with an insecticide, namely vydate. Macrofaunal, especially Nereis diversicolor and oligochaeta, and meiofaunal densities decreased, while the diatom biomass did not change. This resulted in a 300% increase in sediment stability, caused by a reduction in bioturbation and grazing pressure and a decrease in the water content.

Sedimentary Environments Mapping in the Yellow Sea Using TanDEM-X and Optic Satellites

NASA Astrophysics Data System (ADS)

Ryu, J. H.; Lee, Y. K.; Kim, S. W.

2017-12-01

Due to land reclamation and dredging, 57% of China's coastal wetlands have disappeared since the 1950s, and the total area of tidal flats in South Korea decreased from approximately 2,800km2 in 1990 to 2392km2 in 2005(Qiu, 2011 and MLTM, 2010). Intertidal DEM and sedimentary facies are useful for understanding intertidal functions and monitoring their response to natural and anthropogenic actions. Highly accurate intertidal DEMs with 5-m resolution were generated based on the TanDEM-X interferometric SAR (InSAR) technique because TanDEM-X allows the acquisition of the coherent InSAR pairs with no time lag or approximately 10-second temporal baseline between master and slave SAR image. We successfully generated intertidal zone DEMs with 5-7-m spatial resolutions and interferometric height accuracies better than 0.15 m for three representative tidal flats on the west coast of the Korean Peninsula and one site of chinese coastal region in the Yellow Sea. Surface sediment classification based on remotely sensed data must circumspectly consider an effective critical grain size, water content, local topography, and intertidal structures. The earlier studies have some limitation that the classification map is not considered to analysis various environmental conditions. Therefore, the purpose of this study was minutely to mapping the surface sedimentary facies by analyzing the tidal channel, topography with multi-sensor remotely sensed data and in-situ data.

Diatom-sedimentation feedback generates a self-organized geomorphic landscape on intertidal mudflats (Invited)

NASA Astrophysics Data System (ADS)

van de Koppel, J.; Weerman, E.; Herman, P.

2010-12-01

During spring, intertidal flats can exhibit strikingly regular spatial patterns of diatom-covered hummocks alternating with almost bare, water-filled hollows. We hypothesize that 1) the formation of this geomorphic landscape is caused by a strong interaction between benthic diatoms and sediment dynamics, inducing spatial self-organization, and 2) that self-organization affects ecosystem functioning by increasing the net average sedimentation on the tidal flat. We present a combined empirical and mathematical study to test the first hypothesis. We determined how the sediment erosion threshold varied with diatom cover and elevation. Our results were incorporated into a mathematical model to investigate whether the proposed mechanism could explain the formation of the observed patterns. Our mathematical model confirmed that the interaction between sedimentation, diatom growth and water redistribution could induce the formation of regular patterns on the intertidal mudflat. The model predicts that areas exhibiting spatially-self-organized patterns have increased sediment accretion and diatom biomass compared with areas lacking spatial patterns. We tested this prediction by following the sediment elevation during the season on both patterned and unpatterned parts of the mudflat. The results of our study confirmed our model prediction, as more sediment was found to accumulate in patterned parts of the mudflat, revealing how self-organization affected the functioning of mudflat ecosystems. Our study on intertidal mudflats provides a simple but clear-cut example of how the interaction between biological and geomorphological processes, through the process of self-organization, induces a self-organized geomorphic landscape.

RESPONSE OF GHOST SHRIMP (NEOTRYPAEA CALIFORNIENSIS) BIOTURBATION TO ORGANIC MATTER ENRICHMENT OF ESTUARINE INTERTIDAL SEDIMENTS

EPA Science Inventory

Populations of burrowing shrimp (Neotrypaea californiensis and Upogebia p;ugettensis) are the dominant invertebrate fauna on Pacific estuarine tide flats, occupying >80% of intertidal area in some estuaries. Burrowing shrimp are renowned for their bioturbation of intertidal sedi...

Microbial biofilms in intertidal systems: an overview

NASA Astrophysics Data System (ADS)

Decho, Alan W.

2000-07-01

Intertidal marine systems are highly dynamic systems which are characterized by periodic fluctuations in environmental parameters. Microbial processes play critical roles in the remineralization of nutrients and primary production in intertidal systems. Many of the geochemical and biological processes which are mediated by microorganisms occur within microenvironments which can be measured over micrometer spatial scales. These processes are localized by cells within a matrix of extracellular polymeric secretions (EPS), collectively called a "microbial biofilm". Recent examinations of intertidal systems by a range of investigators using new approaches show an abundance of biofilm communities. The purpose of this overview is to examine recent information concerning the roles of microbial biofilms in intertidal systems. The microbial biofilm is a common adaptation of natural bacteria and other microorganisms. In the fluctuating environments of intertidal systems, biofilms form protective microenvironments and may structure a range of microbial processes. The EPS matrix of biofilm forms sticky coatings on individual sediment particles and detrital surfaces, which act as a stabilizing anchor to buffer cells and their extracellular processes during the frequent physical stresses (e.g., changes in salinity and temperature, UV irradiation, dessication). EPS is an operational definition designed to encompass a range of large microbially-secreted molecules having widely varying physical and chemical properties, and a range of biological roles. Examinations of EPS using Raman and Fourier-transform infared spectroscopy, and atomic-force microscopy suggest that some EPS gels possess physical and chemical properties which may hasten the development of sharp geochemical gradients, and contribute a protective effect to cells. Biofilm polymers act as a sorptive sponge which binds and concentrates organic molecules and ions close to cells. Concurrently, the EPS appear to localize extracellular enzyme activities of bacteria, and hence contribute to the efficient biomineralization of organics. At larger spatial scales, the copious secretion of specific types of EPS by diatoms on the surfaces of intertidal mudflats may stabilize sediments against resuspension. Biofilms exert important roles in environmental- and public health processes occurring within intertidal systems. The sorptive properties of EPS effectively chelate toxic metals and other contaminants, which then act as an efficient trophic-transfer vehicle for the entry of contaminants into food webs. In the water column, biofilm microenvironments in suspended flocs may form a stabilizing refugia that enhances the survival and propagation of pathogenic (i.e., disease-causing) bacteria entering coastal waters from terrestrial and freshwater sources. The EPS matrix affords microbial cells a tremendous potential for resiliency during periods of stress, and may enhance the overall physiological activities of bacteria. It is emphasized here that the influences of small-scale microbial biofilms must be addressed in understanding larger-scale processes within intertidal systems.

Swept Away: Resuspension of Bacterial Mats Regulates Benthic-Pelagic Exchange of Sulfur

NASA Astrophysics Data System (ADS)

Grant, Jonathan; Bathmann, Ulrich V.

1987-06-01

Filaments and extracellular material from colorless sulfur bacteria (Beggiatoa spp.) form extensive white sulfur mats on surface sediments of coastal, oceanic, and even deep-sea environments. These chemoautotrophic bacteria oxidize soluble reduced sulfur compounds and deposit elemental sulfur, enriching the sulfur content of surface sediment fivefold over that of deeper sediments. Laboratory flume experiments with Beggiatoa mats from an intertidal sandflat (Nova Scotia) demonstrated that even slight erosion of sediment causes a flux of 160 millimoles of sulfur per square meter per hour, two orders of magnitude greater than the flux produced by sulfur transformations involving either sulfate reduction or sulfide oxidation by benthic bacteria. These experiments indicate that resuspension of sulfur bacterial mats by waves and currents is a rapid mechanism by which sediment sulfur is recycled to the water column. Benthic communities thus lose an important storage intermediate for reduced sulfur as well as a high-quality bacterial food source for benthic grazers.

Use of Clostridium perfringens as a fecal indicator to detect intertidal disposal at backcountry marine campsites in Prince William Sound, Alaska

Treesearch

Gino Graziano; Paul Twardock; Rusty Myers; Roman Dial; David Scheel

2007-01-01

Human waste disposal is a health concern in many backcountry areas. This study measured Clostridium perfringens in beach sediments of Prince William Sound, Alaska, to detect fecal contamination resulting from intertidal disposal. Analysis involved holding times that exceeded eight hours. In repeatedly sampled stored sediments, C. perfringens...

Mussel beds are biological power stations on intertidal flats

NASA Astrophysics Data System (ADS)

Engel, Friederike G.; Alegria, Javier; Andriana, Rosyta; Donadi, Serena; Gusmao, Joao B.; van Leeuwe, Maria A.; Matthiessen, Birte; Eriksson, Britas Klemens

2017-05-01

Intertidal flats are highly productive areas that support large numbers of invertebrates, fish, and birds. Benthic diatoms are essential for the function of tidal flats. They fuel the benthic food web by forming a thin photosynthesizing compartment in the top-layer of the sediment that stretches over the vast sediment flats during low tide. However, the abundance and function of the diatom film is not homogenously distributed. Recently, we have realized the importance of bivalve reefs for structuring intertidal ecosystems; by creating structures on the intertidal flats they provide habitat, reduce hydrodynamic stress and modify the surrounding sediment conditions, which promote the abundance of associated organisms. Accordingly, field studies show that high chlorophyll a concentration in the sediment co-vary with the presence of mussel beds. Here we present conclusive evidence by a manipulative experiment that mussels increase the local biomass of benthic microalgae; and relate this to increasing biomass of microalgae as well as productivity of the biofilm across a nearby mussel bed. Our results show that the ecosystem engineering properties of mussel beds transform them into hot spots for primary production on tidal flats, highlighting the importance of biological control of sedimentary systems.

Measuring the role of seagrasses in regulating sediment surface elevation

USGS Publications Warehouse

Potouroglou, Maria; Bull, James C.; Krauss, Ken W.; Kennedy, Hilary A.; Fusi, Marco; Daffonchio, Daniele; Mangora, Mwita M.; Githaiga, Michael N.; Diele, Karen; Huxham, Mark

2017-01-01

Seagrass meadows provide numerous ecosystem services and their rapid global loss may reduce human welfare as well as ecological integrity. In common with the other ‘blue carbon’ habitats (mangroves and tidal marshes) seagrasses are thought to provide coastal defence and encourage sediment stabilisation and surface elevation. A sophisticated understanding of sediment elevation dynamics in mangroves and tidal marshes has been gained by monitoring a wide range of different sites, located in varying hydrogeomorphological conditions over long periods. In contrast, similar evidence for seagrasses is sparse; the present study is a contribution towards filling this gap. Surface elevation change pins were deployed in four locations, Scotland, Kenya, Tanzania and Saudi Arabia, in both seagrass and unvegetated control plots in the low intertidal and shallow subtidal zone. The presence of seagrass had a highly significant, positive impact on surface elevation at all sites. Combined data from the current work and the literature show an average difference of 31 mm per year in elevation rates between vegetated and unvegetated areas, which emphasizes the important contribution of seagrass in facilitating sediment surface elevation and reducing erosion. This paper presents the first multi-site study for sediment surface elevation in seagrasses in different settings and species.

Measuring the role of seagrasses in regulating sediment surface elevation.

PubMed

Potouroglou, Maria; Bull, James C; Krauss, Ken W; Kennedy, Hilary A; Fusi, Marco; Daffonchio, Daniele; Mangora, Mwita M; Githaiga, Michael N; Diele, Karen; Huxham, Mark

2017-09-20

Seagrass meadows provide numerous ecosystem services and their rapid global loss may reduce human welfare as well as ecological integrity. In common with the other 'blue carbon' habitats (mangroves and tidal marshes) seagrasses are thought to provide coastal defence and encourage sediment stabilisation and surface elevation. A sophisticated understanding of sediment elevation dynamics in mangroves and tidal marshes has been gained by monitoring a wide range of different sites, located in varying hydrogeomorphological conditions over long periods. In contrast, similar evidence for seagrasses is sparse; the present study is a contribution towards filling this gap. Surface elevation change pins were deployed in four locations, Scotland, Kenya, Tanzania and Saudi Arabia, in both seagrass and unvegetated control plots in the low intertidal and shallow subtidal zone. The presence of seagrass had a highly significant, positive impact on surface elevation at all sites. Combined data from the current work and the literature show an average difference of 31 mm per year in elevation rates between vegetated and unvegetated areas, which emphasizes the important contribution of seagrass in facilitating sediment surface elevation and reducing erosion. This paper presents the first multi-site study for sediment surface elevation in seagrasses in different settings and species.

Plastic and other microfibers in sediments, macroinvertebrates and shorebirds from three intertidal wetlands of southern Europe and west Africa.

PubMed

Lourenço, Pedro M; Serra-Gonçalves, Catarina; Ferreira, Joana Lia; Catry, Teresa; Granadeiro, José P

2017-12-01

Microplastics are widespread in aquatic environments and can be ingested by a wide range of organisms. They can also be transferred along food webs. Estuaries and other tidal wetlands may be particularly prone to this type of pollution due to their particular hydrological characteristics and sewage input, but few studies have compared wetlands with different anthropogenic pressure. Furthermore, there is no information on microplastic transfer to secondary intertidal consumers such as shorebirds. We analysed intertidal sediments, macroinvertebrates and shorebirds, from three important wetlands along the Eastern Atlantic (Tejo estuary, Portugal; Banc d'Arguin, Mauritania and Bijagós archipelago, Guinea-Bissau), in order to evaluate the prevalence and transfer of microplastics along the intertidal food web. We further investigated variables that could explain the distribution of microplastics within the intertidal areas of the Tejo estuary. Microfibers were recorded in a large proportion of sediment samples (91%), macroinvertebrates (60%) and shorebird faeces (49%). μ-FTIR analysis indicated only 52% of these microfibers were composed of synthetic polymers (i.e. plastics). Microfiber concentrations were generally higher in the Tejo and lower in the Bijagós, with intermediate values for Banc d'Arguin, thus following a latitudinal gradient. Heavier anthropogenic pressure in the Tejo explains this pattern, but the relatively high concentrations in a pristine site like the Banc d'Arguin demonstrate the spread of pollution in the oceans. Similar microfiber concentrations in faeces of shorebirds with different foraging behaviour and similar composition of fibres collected from invertebrate and faeces suggest shorebirds mainly ingest microfibers through their prey, confirming microfiber transfer along intertidal food webs. Within the Tejo estuary, concentration of microfibers in the sediment and bivalves were positively related with the percentage of fine sediments and with the population size of the closest township, suggesting that hydrodynamics and local domestic sewage are the main factors influencing the distribution of microfibers. Copyright © 2017 Elsevier Ltd. All rights reserved.

The effect of sediment mixing on mercury dynamics in two intertidal mudflats at Great Bay Estuary, New Hampshire, USA

PubMed Central

Brown, Lauren E.; Chen, Celia Y.; Voytek, Mary A.; Amirbahman, Aria

2016-01-01

Estuarine sediments store particulate contaminants including mercury (Hg). We studied Hg sediment dynamics in two intertidal mudflats at Great Bay estuary, NH, over multiple years. Sediments at both mudflats were physically mixed down to ~10 cm, as determined by 7Be measurements, albeit via different mechanisms. Portsmouth mudflat (PT) sediments were subject to bioturbation by infaunal organisms and Squamscott mudflat (SQ) sediments were subject to erosion and redeposition. The presence of higher concentrations of fresh Fe(III) hydroxide at PT suggested bioirrigation by the polychaetes (Nereis virens). At depths where infaunal bioirrigation was observed, pore-water inorganic Hg (Hgi) and methylmercury (MeHg) were lower potentially due to their interaction with Fe(III) hydroxide. Methylmercury concentrations increased immediately below this zone in some samples, suggesting that the observed increase in material flux in bioirrigated sediments may initiate from lower depths. Pore water in sediment at PT also had higher fractions of more protein-like and labile DOC than those at SQ that can lead to increased MeHg production in PT, especially at depths where Hgi is not removed from solution by Fe(III) hydroxide. Where sediment erosion and redeposition were observed at SQ, Hg species distribution was extended deeper into the sediment column. Moreover, methyl coenzyme M reductase (MCR) and mercury reductase (mer-A) genes were higher at SQ than PT suggesting differences in conditions for Hg cycling. Results showed that the near-surface region of high MeHg concentrations commonly observed in unmixed sediments does not exist in physically mixed sediments that are common in many estuarine environments. PMID:26924879

The effect of sediment mixing on mercury dynamics in two intertidal mudflats at Great Bay Estuary, New Hampshire, USA.

PubMed

Brown, Lauren E; Chen, Celia Y; Voytek, Mary A; Amirbahman, Aria

2015-12-01

Estuarine sediments store particulate contaminants including mercury (Hg). We studied Hg sediment dynamics in two intertidal mudflats at Great Bay estuary, NH, over multiple years. Sediments at both mudflats were physically mixed down to ~10 cm, as determined by 7 Be measurements, albeit via different mechanisms. Portsmouth mudflat (PT) sediments were subject to bioturbation by infaunal organisms and Squamscott mudflat (SQ) sediments were subject to erosion and redeposition. The presence of higher concentrations of fresh Fe(III) hydroxide at PT suggested bioirrigation by the polychaetes ( Nereis virens ). At depths where infaunal bioirrigation was observed, pore-water inorganic Hg (Hg i ) and methylmercury (MeHg) were lower potentially due to their interaction with Fe(III) hydroxide. Methylmercury concentrations increased immediately below this zone in some samples, suggesting that the observed increase in material flux in bioirrigated sediments may initiate from lower depths. Pore water in sediment at PT also had higher fractions of more protein-like and labile DOC than those at SQ that can lead to increased MeHg production in PT, especially at depths where Hg i is not removed from solution by Fe(III) hydroxide. Where sediment erosion and redeposition were observed at SQ, Hg species distribution was extended deeper into the sediment column. Moreover, methyl coenzyme M reductase (MCR) and mercury reductase ( mer -A) genes were higher at SQ than PT suggesting differences in conditions for Hg cycling. Results showed that the near-surface region of high MeHg concentrations commonly observed in unmixed sediments does not exist in physically mixed sediments that are common in many estuarine environments.

Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL

USGS Publications Warehouse

Klerks, P.L.; Felder, D.L.; Strasser, K.; Swarzenski, P.W.

2007-01-01

This study investigated the effects that ghost shrimp have on the distribution of metals in sediment. We measured levels of HNO3-extractable zinc and cadmium in surface sediment, in ghost shrimp burrow walls and in sediment ejected by the ghost shrimp from their burrows, at five sandy intertidal sites in Tampa Bay. Ghost shrimp densities and their rate of sediment ejection were also quantified, as were sediment organic content and silt + clay content. Densities of ghost shrimp (Sergio trilobata and Lepidophthalmus louisianensis) averaged 33/m2 at our sites, and they ejected sediment at an average rate of 28 g/burrow/day. Levels of both Zn and Cd were significantly higher in burrow walls than in surface sediments. Sediment ejected by the shrimp from their burrows had elevated levels of Zn (relative to surface sediments) at one of the sites. Sediment organic content and silt + clay content were higher in burrow-wall sediments than in ejected sediment, which in turn tended to have values above those of surface sediments. Differences in levels of HNO3-extractable Zn and Cd among sediment types may be a consequence of these sediments differing in other physiochemical characteristics, though the differences in metal levels remained statistically significant for some sites after correcting for differences in organic content and silt + clay content. We conclude that the presence of ghost shrimp burrows contributes to spatial heterogeneity of sedimentary metal levels, while the ghost shrimp bioturbation results in a significant flux of metals to the sediment surface and is expected to decrease heterogeneity of metal levels in sedimentary depth profiles.

Microplastic in two South Carolina Estuaries: Occurrence, distribution, and composition.

PubMed

Gray, Austin D; Wertz, Hope; Leads, Rachel R; Weinstein, John E

2018-03-01

Here we report on the distribution of microplastic contamination in two developed estuaries in the Southeastern United States. Average concentration in intertidal sediments of Charleston Harbor and Winyah Bay, both located in South Carolina, U.S.A., was 413.8 ± 76.7 and 221.0 ± 25.6 particles/m 2 , respectively. Average concentration in the sea surface microlayer of Charleston Harbor and Winyah Bay was 6.6 ± 1.3 and 30.8 ± 12.1 particles/L, respectively. Concentration in intertidal sediments of the two estuaries was not significantly different (p = 0.58), however, Winyah Bay contained significantly more microplastics in the sea surface microlayer (p = 0.02). While microplastic concentration in these estuaries was comparable to that reported for other estuaries worldwide, Charleston Harbor contained a high abundance of black microplastic fragments believed to be tire wear particles. Our research is the first to survey microplastic contamination in Southeastern U.S. estuaries and to provide insight on the nature and extent of contamination in these habitats. Copyright © 2018 Elsevier Ltd. All rights reserved.

Application of the Coastal and Marine Ecological Classification Standard Using Satellite-Derived and Modeled Data Products for Pelagic Habitats in the Northern Gulf of Mexico

DTIC Science & Technology

2013-12-10

intertidal vegetation . Comments from resource managers requested products incor- porating bathymetry and sediment data. To further build on the...and availability of intertidal vegetation are other key factors in successful movement into the estuary for brown shrimp, both of these data were...distribution of intertidal vegetation . The NWI classes EEM1 and EEM2 are the two classes into which intertidal vegeta- tion falls in Galveston. On the ground

Characterisation of the hydrology of an estuarine wetland

NASA Astrophysics Data System (ADS)

Hughes, Catherine E.; Binning, Philip; Willgoose, Garry R.

1998-11-01

The intertidal zone of estuarine wetlands is characterised by a transition from a saline marine environment to a freshwater environment with increasing distance from tidal streams. An experimental site has been established in an area of mangrove and salt marsh wetland in the Hunter River estuary, Australia, to characterise and provide data for a model of intertidal zone hydrology. The experimental site is designed to monitor water fluxes at a small scale (36 m). A weather station and groundwater monitoring wells have been installed and hydraulic head and tidal levels are monitored over a 10-week period along a short one-dimensional transect covering the transition between the tidal and freshwater systems. Soil properties have been determined in the laboratory and the field. A two-dimensional finite element model of the site was developed using SEEP/W to analyse saturated and unsaturated pore water movement. Modification of the water retention function to model crab hole macropores was found necessary to reproduce the observed aquifer response. Groundwater response to tidal fluctuations was observed to be almost uniform beyond the intertidal zone, due to the presence of highly permeable subsurface sediments below the less permeable surface sediments. Over the 36 m transect, tidal forcing was found to generate incoming fluxes in the order of 0.22 m 3/day per metre width of creek bank during dry periods, partially balanced by evaporative fluxes of about 0.13 m 3/day per metre width. During heavy rainfall periods, rainfall fluxes were about 0.61 m 3/day per metre width, dominating the water balance. Evapotranspiration rates were greater for the salt marsh dominated intertidal zone than the non-tidal zone. Hypersalinity and salt encrustation observed show that evapotranspiration fluxes are very important during non-rainfall periods and are believed to significantly influence salt concentration both in the surface soil matrix and the underlying aquifer.

Sedimentary facies and Holocene progradation rates of the Changjiang (Yangtze) delta, China

NASA Astrophysics Data System (ADS)

Hori, Kazuaki; Saito, Yoshiki; Zhao, Quanhong; Cheng, Xinrong; Wang, Pinxian; Sato, Yoshio; Li, Congxian

2001-11-01

The Changjiang (Yangtze) River, one of the largest rivers in the world, has formed a broad tide-dominated delta at its mouth during the Holocene sea-level highstand. Three boreholes (CM97, JS98, and HQ98) were obtained from the Changjiang delta plain in 1997-1998 to clarify the characteristics of tide-dominated delta sediments and architecture. Based on sediment composition and texture, and faunal content, core sediments were divided into six depositional units. In ascending order, they were interpreted as tidal sand ridge, prodelta, delta-front, subtidal to lower intertidal flat, upper intertidal flat, and surface soil deposits. The deltaic sequence from the prodelta deposits to the delta front deposits showed an upward-coarsening succession, overlain by an upward-fining succession from the uppermost part of the delta front deposits to the surface soil. Thinly interlaminated to thinly interbedded sand and mud (sand-mud couplets), and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of Changjiang deltaic facies. Sediment facies and their succession combined with AMS 14C dating revealed that isochron lines cross unit boundaries clearly, and delta progradation has occurred since about 6000 to 7000 years BP, when the rising sea level neared or reached its present position. The average progradation rate of the delta front was approximately 50 km/kyear over the last 5000 years. The progradation rate, however, increased abruptly ca. 2000 years BP, going from 38 to 80 km/kyear. The possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and/or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid-Holocene.

Documenting a modern day transgressive surface in a carbonate ramp setting

NASA Astrophysics Data System (ADS)

Lokier, Stephen; Paul, Andreas

2017-04-01

The low-angle carbonate ramp geometry of the Abu Dhabi coastline provides an ideal site for studying the effects of marine transgression in a setting analogous to Mesozoic epeiric seas. Supratidal sabkha evaporite precipitation passes offshore, through a broad and complex carbonate-evaporite intertidal environment, into a subtidal carbonate depositional setting. The coast of the mainland is locally isolated from open-marine conditions by a number of peninsulas and islands associated with the east-west trending Great Pearl Bank. This study combined 12 years of fieldwork observations with historical satellite imagery in order to establish multiple lines of evidence for active retrogradation over a 15 km length of coastline in the Abu Dhabi sabkha. Surveyed transects of the sabkha yield an average slope angle of 0.02°. Employing a current estimate of global sea level rise of 3.3 mm/yr, we calculate an expected present-day marine transgression of 7.9 m/yr. The landward and seaward boundaries of the microbial mat facies belt are strongly controlled by the location of the intertidal zone. The seaward limit of the Recent microbial mat belt in the Abu Dhabi Sabkha is currently being buried beneath retrograding lower-intertidal sediments whilst the landward side is simultaneously backstepping over previously-supratidal gypsum-dominated facies. The landward migration of spits and beach ridges was monitored at several locations with rates of retrogradation of up to 28 m per year being recorded locally. The study also identified numerous erosive features that are consistent with an increase in energy regimes. There has been a significant increase in denudation of the microbial mat, causing underlying sediment to be increasingly susceptible to erosion. In the lowermost intertidal zone, erosion of the hardground and other facies is observed. Clasts from the hardground are transported landward onto the surface of the sabkha where they are incorporated within other facies. This study provides definitive evidence that the current sedimentary regime of the Abu Dhabi coastline has entered a retrogradational phase associated with marine transgression. From a sequence stratigraphic perspective, the current system would be identified as a flooding (transgressive) surface.

The persistence and character of stranded oil on coarse-sediment beaches.

PubMed

Owens, Edward H; Taylor, Elliott; Humphrey, Blair

2008-01-01

Small amounts of oil that can persist for decades in the intertidal zone of coarse-sediment beaches have been documented in a few well-studied cases. Oil that survives attenuation over the short-term (weeks to months) will persist until there is a change in the environmental conditions, as might occur where there is a seasonal storm-wave climate or as a beach undergoes long-term (erosional) changes. Oil residues can persist on the beach surface as tar mats, asphalt-like pavements, or as veneers on sediment particles or hard surfaces. Subsurface oil residues can persist in similar forms or as fill or partial fill of the pore spaces between coarse-sediment particles. Oil penetrates until it reaches fine-grained sediment, the water table, bedrock, or other penetration-limiting layers. Amounts of persistent oil are very small fractions of the volumes that were originally stranded and these protected residues can continue to biodegrade as they become thinner and more discontinuous.

Effects of mud sedimentation on lugworm ecosystem engineering

NASA Astrophysics Data System (ADS)

Montserrat, F.; Suykerbuyk, W.; Al-Busaidi, R.; Bouma, T. J.; van der Wal, D.; Herman, P. M. J.

2011-01-01

Benthic ecosystem engineering organisms attenuate hydrodynamic or biogeochemical stress to ameliorate living conditions. Bioturbating infauna, like the lugworm Arenicola marina, determine intertidal process dynamics by maintaining the sediment oxygenated and sandy. Maintaining the permeability of the surrounding sediment enables them to pump water through the interstitial spaces, greatly increasing the oxygen availability. In a field experiment, both lugworm presence and siltation regime were manipulated to investigate to what extent lugworms are able to cope with sedimentation of increasing mud percentage and how this would affect its ecosystem engineering. Fluorescent tracers were added to experimentally deposited mud to visualise bioturbation effects on fine sediment fractions. Lugworm densities were not affected by an increasing mud percentage in experimentally deposited sediment. Negative effects are expected to occur under deposition with significantly higher mud percentages. Surface chlorophyll a content was a function of experimental mud percentage, with no effect of lugworm bioturbation. Surface roughness and sediment permeability clearly increased by lugworm presence, whereas sediment erosion threshold was not significantly affected by lugworms. The general idea that A. marina removes fine sediment fractions from the bed could not be confirmed. Rather, the main ecosystem engineering effect of A. marina is hydraulic destabilisation of the sediment matrix.

Intertidal biofilm distribution underpins differential tide-following behavior of two sandpiper species (Calidris mauri and Calidris alpina) during northward migration

NASA Astrophysics Data System (ADS)

Jiménez, Ariam; Elner, Robert W.; Favaro, Corinna; Rickards, Karen; Ydenberg, Ronald C.

2015-03-01

The discovery that some shorebird species graze heavily on biofilm adds importance to elucidating coastal processes controlling biofilm, as well as impetus to better understand patterns of shorebird use of intertidal flats. Western sandpipers (Calidris mauri) and dunlin (Calidris alpina) stopover in the hundreds of thousands on the Fraser River estuary, British Columbia, Canada, during northward migration to breeding areas. Western sandpipers show greater modification of tongue and bill morphology for biofilm feeding than dunlin, and their diet includes more biofilm. Therefore, we hypothesized that these congeners differentially use the intertidal area. A tide following index (TFI) was used to describe their distributions in the upper intertidal during ebbing tides. Also, we assessed sediment grain size, biofilm (= microphytobenthic or MPB) biomass and invertebrate abundance. Foraging dunlin closely followed the ebbing tide line, exploiting the upper intertidal only as the tide retreated through this area. In contrast, western sandpipers were less prone to follow the tide, and spent more time in the upper intertidal. Microphytobenthic biomass and sediment water content were highest in the upper intertidal, indicating greater biofilm availability for shorebirds in the first 350 m from shore. Invertebrate density did not differ between sections of the upper intertidal. Overall, western sandpiper behaviour and distribution more closely matched MPB biofilm availability than invertebrate availability. Conservation of sandpipers should consider physical processes, such as tides and currents, which maintain the availability of biofilm, a critical food source during global migration.

Defining the ecogeomorphic succession of land building for freshwater, intertidal wetlands in Wax Lake Delta, Louisiana

NASA Astrophysics Data System (ADS)

Olliver, Elizabeth A.; Edmonds, Douglas A.

2017-09-01

Land building in deltaic environments occurs when sediment discharged from a river mouth is deposited subaqueously and transitions to subaerial land. The transition from subaqueous deposition to subaerial land is a critical process that marks the creation of relatively stable land, yet it is unclear what controls the speed and style of this transition. We define how this transition, herein termed the land building succession, varies in time and space for the freshwater, intertidal wetlands in Wax Lake Delta, LA. Using remote sensing and field data we classify land cover into sediment, water, or vegetation classes at maximum and minimum biomass. We see two succession patterns within Wax Lake Delta. Deltaic islands near the apex are initially covered by sediment and open water. Through time, open water and sediment coverage decreases as vegetation coverage increases. On the other hand, distal islands show little sediment exposure through time. In both cases, all deltaic islands become covered with vegetation by 2015. As vegetation colonizes the island, the topography organizes into two platforms vertically separated by ∼0.35 m. The lower, intertidal platform occurs in the island interiors and is commonly inundated by water and dominated by subaqueous or floating vegetation. The upper, subaerial platform occurs along island edges and is dominated by a variety of vegetation species including Salix nigra, Colocasia esculenta, and Polygonum punctatum. It takes an average of ∼10 years for the intertidal platform to transition to the subaerial platform. These two platforms are separated by the tidal range measured in Atchafalaya Bay, and the different vegetation communities occupying each platform suggest they are a manifestation of multiple stable states and arise due to vegetation and sedimentation feedbacks.

Dissolved gaseous mercury formation and mercury volatilization in intertidal sediments.

PubMed

Cesário, Rute; Poissant, Laurier; Pilote, Martin; O'Driscoll, Nelson J; Mota, Ana M; Canário, João

2017-12-15

Intertidal sediments of Tagus estuary regularly experiences complex redistribution due to tidal forcing, which affects the cycling of mercury (Hg) between sediments and the water column. This study quantifies total mercury (Hg) and methylmercury (MMHg) concentrations and fluxes in a flooded mudflat as well as the effects on water-level fluctuations on the air-surface exchange of mercury. A fast increase in dissolved Hg and MMHg concentrations was observed in overlying water in the first 10min of inundation and corresponded to a decrease in pore waters, suggesting a rapid export of Hg and MMHg from sediments to the water column. Estimations of daily advective transport exceeded the predicted diffusive fluxes by 5 orders of magnitude. A fast increase in dissolved gaseous mercury (DGM) concentration was also observed in the first 20-30min of inundation (maximum of 40pg L -1 ). Suspended particulate matter (SPM) concentrations were inversely correlated with DGM concentrations. Dissolved Hg variation suggested that biotic DGM production in pore waters is a significant factor in addition to the photochemical reduction of Hg. Mercury volatilization (ranged from 1.1 to 3.3ngm -2 h -1 ; average of 2.1ngm -2 h -1 ) and DGM production exhibited the same pattern with no significant time-lag suggesting a fast release of the produced DGM. These results indicate that Hg sediment/water exchanges in the physical dominated estuaries can be underestimated when the tidal effect is not considered. Copyright © 2017 Elsevier B.V. All rights reserved.

Persistence and biodegradation of kerosene in high-arctic intertidal sediment.

PubMed

Røberg, Stian; Stormo, Svein Kristian; Landfald, Bjarne

2007-10-01

A kerosene type hydrocarbon fraction (equivalent to 7 L m(-2)) was added to enclosures in the surface layer of high-arctic intertidal beach sediment. The experimental spill was repeated in two consecutive years in the period July-September. The rate and extent of hydrocarbon removal and the accompanying bacterial response were monitored for 79 days (2002) and 78 days (2003). The bulk of added kerosene, i.e. 94-98%, was lost from the upper 5 cm layer by putatively abiotic processes within 2 days and a residual fraction in the range 0.6-1.2mg per g dry sediment was stably retained. Concomitant addition of oleophilic fertilizer led to higher initial retention, as 24% of the kerosene remained after 2 days in the presence of a modified, cold-climate adapted version of the well-known Inipol EAP 22 bioremediation agent. In these enclosures, which showed an increase in hydrocarbon-degrader counts from 6.5 x 10(3) to 4.1 x 10(7) per g dry sediment within 8 days, a 17% contribution by biodegradation to subsequent hydrocarbon removal was estimated. Stimulation in hydrocarbon-degrader counts in fertilizer-alone control enclosures was indistinguishable from the stimulation observed with both kerosene and fertilizer present, suggesting that the dynamics in numbers of hydrocarbon-degrading bacteria was primarily impacted by the bioremediation agent.

Microscale Characterization and Trace Element Distribution in Bacteriogenic Ferromanganese Coatings on Sand Grains from an Intertidal Zone of the East China Sea

PubMed Central

Yuan, Linxi; Sun, Liguang; Fortin, Danielle; Wang, Yuhong; Yin, Xuebin

2015-01-01

An ancient wood layer dated at about 5600 yr BP by accelerator mass spectrometry (AMS) 14C was discovered in an intertidal zone of the East China Sea. Extensive and horizontally stratified sediments with black color on the top and yellowish-red at the bottom, and some nodule-cemented concretions with brown surface and black inclusions occurred in this intertidal zone. Microscale analysis methods were employed to study the microscale characterization and trace element distribution in the stratified sediments and concretions. Light microscopy, scanning electron microscopy (SEM) and backscattered electron imaging (BSE) revealed the presence of different coatings on the sand grains. The main mineral compositions of the coatings were ferrihydrite and goethite in the yellowish-red parts, and birnessite in the black parts using X-ray powder diffraction (XRD). SEM observations showed that bacteriogenic products and bacterial remnants extensively occurred in the coatings, indicating that bacteria likely played an important role in the formation of ferromanganese coatings. Post-Archean Australian Shale (PAAS)-normalized middle rare earth element (MREE) enrichment patterns of the coatings indicated that they were caused by two sub-sequential processes: (1) preferentially release of Fe-Mn from the beach rocks by fermentation of ancient woods and colloidal flocculation in the mixing water zone and (2) preferential adsorption of MREE by Fe-Mn oxyhydroxides from the seawater. The chemical results indicated that the coatings were enriched with Sc, V, Cr, Co, Ni, Cu, Zn, Ba, especially with respect to Co, Ni. The findings of the present study provide an insight in the microscale features of ferromanganese coatings and the Fe-Mn biogeochemical cycling during the degradation of buried organic matter in intertidal zones or shallow coasts. PMID:25786213

Seagrass impact on sediment exchange between tidal flats and salt Marsh, and the sediment budget of shallow bays

USGS Publications Warehouse

Donatelli, Carmine; Ganju, Neil Kamal; Fagherazzi, Sergio; Leonardi, Nicoletta

2018-01-01

surroundings and are therefore frequently referred to as ecological engineers. The effect of seagrasses on coastal bay resilience and sediment transport dynamics is understudied. Here we use six historical maps of seagrass distribution in Barnegat Bay, USA, to investigate the role of these vegetated surfaces on the sediment storage capacity of shallow bays. Analyses are carried out by means of the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) numerical modeling framework. Results show that a decline in the extent of seagrass meadows reduces the sediment mass potentially stored within bay systems. The presence of seagrass reduces shear stress values across the entire bay, including unvegetated areas, and promotes sediment deposition on tidal flats. On the other hand, the presence of seagrasses decreases suspended sediment concentrations, which in turn reduces the delivery of sediment to marsh platforms. Results highlight the relevance of seagrasses for the long-term survival of coastal ecosystems, and the complex dynamics regulating the interaction between subtidal and intertidal landscapes.

Intertidal Sandbar Welding as a Primary Source of Sediment for Dune Growth: Evidence from a Large Scale Field Experiment

NASA Astrophysics Data System (ADS)

Cohn, N.; Ruggiero, P.; de Vries, S.

2016-12-01

Dunes provide the first line of defense from elevated water levels in low-lying coastal systems, limiting potentially major flooding, economic damages, and loss of livelihood. Despite the well documented importance of healthy dunes, our predictive ability of dune growth, particularly following erosive storm events, remains poor - resulting in part from traditionally studying the wet and dry beach as separate entities. In fact, however, dune recovery and growth is closely tied to the subtidal morphology and the nearshore hydrodynamic conditions, necessitating treating the entire coastal zone from the shoreface to the backshore as an integrated system. In this context, to further improve our understanding of the physical processes allowing for beach and dune growth during fair weather conditions, a large field experiment, the Sandbar-aEolian Dune EXchange EXperiment, was performed in summer 2016 in southwestern Washington, USA. Measurements of nearshore and atmospheric hydrodynamics, in-situ sediment transport, and morphology change provide insight into the time and space scales of nearshore-beach-dune exchanges along a rapidly prograding stretch of coast over a 6 week period. As part of this experiment, the hypothesis that dune growth is limited by the welding of intertidal sandbars to the shoreline (Houser, 2009) was tested. Using laser particle counters, bed elevation sensors (sonar altimeters and Microsoft Kinect), continuously logging sediment traps, RGB and IR cameras, and repeat morphology surveys (terrestrial lidar, kite based structure from motion, and RTK GPS), spatial and temporal trends in aeolian sediment transport were assessed in relation to the synoptic onshore migration and welding of intertidal sandbars. Observations from this experiment demonstrate that (1) the intertidal zone is the primary source of sediment to the dunes during non-storm conditions, (2) rates of saltation increase during later stages of bar welding but equivalent wind conditions, and (3) alongshore variability in rates of backshore fluxes appear to be related to alongshore variability in intertidal morphology. These observations quantitatively support the Houser (2009) bar welding hypothesis and provide valuable new insights on nearshore-beach-dune sediment exchanges

Trace metal contamination in surface sediments of intertidal zone from Qinhuangdao, China, revealed by geochemical and magnetic approaches: Distribution, sources, and health risk assessment.

PubMed

Zhu, Zongmin; Xue, Junhui; Deng, Yuzhen; Chen, Lin; Liu, Jiangfeng

2016-04-15

Based on geochemical and magnetic approaches, the distribution, sources, and health risk of trace metals in surface sediments from a seashore tourist city were investigated. A significant correlation was found between magnetic susceptibility (χ) and trace metals, which suggested that levels of trace metals in the sediments can be effectively depicted by the magnetic approach. The spatial distribution of χ and trace metals matched well with the city layout with relatively higher values being found in the port and busy tourist areas. This result, together with enrichment factors (EFs) and Tomlinson pollution load index (PLI) of metals, suggested that the influence of human activities on the coastal environment was noticeable. Principal component analysis (PCA) indicated that trace metals in the sediments were derived from both anthropogenic and natural sources. Noncarcinogenic risk assessment showed that there was no potential health risk of exposure to metals by means of ingestion or inhalation. Copyright © 2016 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

O`Clair, C.E.; Short, J.W.; Rice, S.D.

Sediments were collected at ten locations in Prince William Sound in July 1993 to determine the geographical and bathymetric distribution of oil from the Exxon Valdez oil spill in the low intertidal zone and subtidal region. The authors sampled sediments at mean lower low water (0 m) and at five subtidal depths from 3 to 100 m. No Exxon Valdez oil was found in sediments at 0 m where the greatest mean intertidal concentration of total polynuclear aromatic hydrocarbons excluding perylene (54 ng/g) was observed at Moose Lips Bay. Subtidal sediments showed polynuclear aromatic hydrocarbon composition patterns similar to Exxonmore » Valdez oil at three sites, Herring Bay, Northwest Bay and Sleepy Bay. Contamination of sediments by Exxon Valdez oil reached a depth of 20 m at Northwest Bay and Sleepy Bay. In deep sediments (> or = 40 m) the authors found no evidence of weathered Exxon Valdez oil.« less

Utilization Patterns of Intertidal Habitats by Birds in Yaquina Estuary, Oregon

EPA Science Inventory

Bird utilization patterns were assessed in five types of intertidal soft sediment and low marsh habitat in the Yaquina estuary, Oregon. Censuses were designed to determine the spatial and seasonal utilization patterns of birds in Zostera marina (eelgrass), Upogebia (mud shrimp)/...

Macrofauna on flood delta shoals in the Wadden Sea with an underground association between the lugworm Arenicola marina and the amphipod Urothoe poseidonis

NASA Astrophysics Data System (ADS)

Lackschewitz, D.; Reise, K.

1998-06-01

Living conditions for macrofauna on flood delta shoals are determined by surf, strong currents and sediment mobility. Thus, a unique assemblage of invertebrate species colonize these far off-shore, low intertidal flats. We here describe the macrobenthic fauna of emerging shoals in the Wadden Sea between the islands of Römö and Sylt. Besides ubiquitous macroinvertebrates of the intertidal zone and species which attain their main distribution in the subtidal zone, the flood delta shoals are characterized by organisms adapted to live in these highly unstable sediments, like the polychaetes Spio martinensis, Streptosyllis websteri, Magelona mirabilis, Psammodrilus balanoglossoides, the pericarid crustaceans Cumopsis goodsiri, Tanaissus lilljeborgi, Bathyporeia sarsi and a few others. Average abundance (1440 m-2 of ind >1 mm) and biomass (12.9 g AFDW m-2) were low compared to other intertidal habitats in the Wadden Sea. Biomass was dominated by largesized individuals of the lugworm Arenicola marina. The U-shaped burrows of these polychaetes were inhabited by high numbers of Urothoe poseidonis. Maximum densities of these amphipods occurred in the deepest parts of the burrows. Sampling at approximately montly intervals revealed no apparent seasonality of U. poseidonis abundance. Together with small Capitella capitata, these amphipods constitute a deep-dwelling component of the macrofauna associated with lugworms, which is separated from all other macrofauna living at the sediment surface. As a response to rising sea level and increasing tidal ranges, we expect the unstable sandy shoals, inhabited by numerous Spio martinensis and Urothoe poseidonis, to expand within the Wadden Sea at the cost of stable sandy flats with abundant macrofauna.

Impact of the Phaeocystis globosa spring bloom on the intertidal benthic compartment in the eastern English Channel: a synthesis.

PubMed

Spilmont, Nicolas; Denis, Lionel; Artigas, Luis Felipe; Caloin, Frédéric; Courcot, Lucie; Créach, Anne; Desroy, Nicolas; Gevaert, François; Hacquebart, Pascal; Hubas, Cédric; Janquin, Marie-Andrée; Lemoine, Yves; Luczak, Christophe; Migné, Aline; Rauch, Mathieu; Davoult, Dominique

2009-01-01

From 1999 to 2005, studies carried out in the frame of regional and national French programs aimed to determine whether the Phaeocystis globosa bloom affected the intertidal benthic communities of the French coast of the eastern English Channel in terms of composition and/or functioning. Study sites were chosen to cover most of the typical shore types encountered on this coast (a rocky shore, an exposed sandy beach and a small estuary). Both the presence of active Phaeocystis cells and their degradation product (foam) did have a significant impact on the studied shores. The primary production and growth rates of the kelp Saccharina latissima decreased during the bloom because of a shortage of light and nutrient for the macroalgae. On sandy sediments, the benthic metabolism (community respiration and community primary production), as well as the nitrification rate, were enhanced during foam deposits, in relation with the presence of bacteria and active pelagic cells within the decaying colonies. In estuarine sediments, the most impressive impact was the formation of a crust at the sediment surface due to drying foam. This led to anoxic conditions in the surface sediment and resulted in a high mortality among the benthic community. Some organisms also tended to migrate upward and were then directly accessible to the higher trophic level represented by birds. Phaeocystis then created a shortcut in the estuarine trophic network. Most of these modifications lasted shortly and all the systems considered came back to their regular properties and activities a few weeks after the end of the bloom, except for the most impacted estuarine area.

The Effect of Source Suspended Sediment Concentration on the Sediment Dynamics of a Macrotidal Creek and Salt Marsh

NASA Astrophysics Data System (ADS)

Poirier, E.; van Proosdij, D.; Milligan, T. G.

2017-12-01

Seasonal variability in the sediment dynamics of a Bay of Fundy tidal creek and salt marsh system was analyzed to better understand the ecomorphodynamics of a high suspended sediment concentration intertidal habitat. Data were collected over 62 tides for velocity, suspended sediment concentration, deposition, and grain size at four stations from the creek thalweg to the marsh surface. Five topographic surveys were also conducted throughout the 14-month study. Deposition rates per tide varied spatially from 56.4 g·m-2 at the creek thalweg to 15.3 g·m-2 at the marsh surface. Seasonal variations in deposition in the creek and marsh surface were from 38.0 g·m-2 to 97.7 g·m-2 and from 12.2 g·m-2 to 19.6 g·m-2 respectively. Deposition and erosion were greatest in late fall and winter. This seasonal change, led by higher suspended sediment concentrations, was observed in the creek and at the marsh bank but notably absent from the marsh edge and marsh surface. Sediments were predominantly deposited in floc form (76-83%). Because of high floc content, higher suspended sediment concentrations led to more rapid loss of sediment from suspension. With increasing sediment concentration, deposition increased in the tidal creek and at the marsh bank but not at the marsh edge or marsh surface. This suggests that in highly flocculated environments the water column clears fast enough that very little sediment remains in suspension when the water reaches the marsh and that the sediment concentration during marsh inundation is independent of the initial concentration in the creek.

The effect of source suspended sediment concentration on the sediment dynamics of a macrotidal creek and salt marsh

NASA Astrophysics Data System (ADS)

Poirier, Emma; van Proosdij, Danika; Milligan, Timothy G.

2017-09-01

Seasonal variability in the sediment dynamics of a Bay of Fundy tidal creek and salt marsh system was analyzed to better understand the ecomorphodynamics of a high suspended sediment concentration intertidal habitat. Data were collected over 62 tides for velocity, suspended sediment concentration, deposition, and grain size at four stations from the creek thalweg to the marsh surface. Five topographic surveys were also conducted throughout the 14-month study. Deposition rates per tide varied spatially from 56.4 g m-2 at the creek thalweg to 15.3 g m-2 at the marsh surface. Seasonal variations in deposition in the creek and marsh surface were from 38.0 g m-2 to 97.7 g m-2 and from 12.2 g m-2 to 19.6 g m-2 respectively. Deposition and erosion were greatest in late fall and winter. This seasonal change, led by higher suspended sediment concentrations, was observed in the creek and at the marsh bank but notably absent from the marsh edge and marsh surface. Sediments were predominantly deposited in floc form (76-83%). Because of high floc content, higher suspended sediment concentrations led to more rapid loss of sediment from suspension. With increasing sediment concentration, deposition increased in the tidal creek and at the marsh bank but not at the marsh edge or marsh surface. This suggests that in highly flocculated environments the water column clears fast enough that very little sediment remains in suspension when the water reaches the marsh and that the sediment concentration during marsh inundation is independent of the initial concentration in the creek.

Bacterial community structure in response to environmental impacts in the intertidal sediments along the Yangtze Estuary, China.

PubMed

Guo, Xing-Pan; Lu, Da-Pei; Niu, Zuo-Shun; Feng, Jing-Nan; Chen, Yu-Ru; Tou, Fei-Yun; Liu, Min; Yang, Yi

2018-01-01

This study was designed to investigate the characteristics of bacterial communities in intertidal sediments along the Yangtze Estuary and their responses to environmental factors. The results showed that bacterial abundance was significantly correlated with salinity, SO 4 2- and total organic carbon, while bacterial diversity was significantly correlated with SO 4 2- and total nitrogen. At different taxonomic levels, both the dominant taxa and their abundances varied among the eight samples, with Proteobacteria being the most dominant phylum in general. Cluster analysis revealed that the bacterial community structure was influenced by river runoff and sewerage discharge. Moreover, SO 4 2- , salinity and total phosphorus were the vital environmental factors that influenced the bacterial community structure. Quantitative PCR and sequencing of sulphate-reducing bacteria indicated that the sulphate reduction process occurs frequently in intertidal sediments. These findings are important to understand the microbial ecology and biogeochemical cycles in estuarine environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ecological evaluation of an experimental beneficial use scheme for dredged sediment disposal in shallow tidal waters.

PubMed

van der Wal, Daphne; Forster, Rodney M; Rossi, Francesca; Hummel, Herman; Ysebaert, Tom; Roose, Frederik; Herman, Peter M J

2011-01-01

An experiment was performed to test an alternative dredging strategy for the Westerschelde estuary. Clean sand dredged from the navigation channel was disposed seawards of an eroding intertidal flat in order to modify morphology and hydrodynamics, improving the multi-channel system with ecologically productive shallow water habitat. Five years of intensive monitoring revealed that part of the disposed sediment moved slowly towards the flat, increasing the very shallow subtidal and intertidal area, as planned. The sand in the impact zone became gradually finer after disposal, possibly due to reduced current velocities. Nevertheless, no changes in macrobenthic biomass, density, species richness and composition were detected in the subtidal zone, also demonstrating rapid macrobenthic recovery. In the intertidal zone, no ecological effects could be revealed superimposed on trends associated with long-term sediment fining. Thus, despite morphological success and absence of detected negative ecological impacts of the experiment, new beneficial habitat was not created. Copyright © 2010 Elsevier Ltd. All rights reserved.

Velocity and sediment surge: What do we see at times of very shallow water on intertidal mudflats?

NASA Astrophysics Data System (ADS)

Zhang, Qian; Gong, Zheng; Zhang, Changkuan; Townend, Ian; Jin, Chuang; Li, Huan

2016-02-01

A self-designed "bottom boundary layer hydrodynamic and suspended sediment concentration (SSC) measuring system" was built to observe the hydrodynamic and the SSC processes over the intertidal mudflats at the middle part of the Jiangsu coast during August 8-10, 2013. Velocity profiles within 10 cm of the mudflat surface were obtained with a vertical resolution as fine as 1 mm. An ADCP was used to extend the profile over the full water depth with a resolution of 10 cm and the vertical SSC profile was measured at intervals using Optical Backscatter Sensors (OBS). At the same time, water levels and wave conditions were measured with a Tide and Wave Recorder. Measured data suggested that the vertical structure of velocity profiles within 10 cm above the bed maintains a logarithmic distribution during the whole tidal cycle except the slack-water periods. Shallow flows during both the early-flood period and the later-ebb period are characterized by a relatively large vertical velocity gradient and a "surge" feature. We conclude that the very shallow water stages are transient and may not contribute much to the whole water and sediment transport, while they can play a significant role in the formation and evolution of micro-topographies on tidal flats.

Temporal fluctuations in grain size, organic materials and iron concentrations in intertidal surface sediment of San Francisco Bay

USGS Publications Warehouse

Thomson-Becker, E. A.; Luoma, S.N.

1985-01-01

The physical and chemical characteristics of the oxidized surface sediment in an estuary fluctuate temporally in response to physical forces and apparently-fluctuating inputs. These characteristics, which include grain size and concentrations of organic materials and iron, will influence both trace-metal geochemistry and bioavailability. Temporal trends in the abundance of fine particles, total organic carbon content (TOC), absorbance of extractable organic material (EOM), and concentration of extractable iron in the sediment of San Francisco Bay were assessed using data sets containing approximately monthly samples for periods of two to seven years. Changes in wind velocity and runoff result in monthly changes in the abundance of fine particles in the intertidal zone. Fine-grained particles are most abundant in the late fall/early winter when runoff is elevated and wind velocities are low; particles are coarser in the summer when runoff is low and wind velocities are consistently high. Throughout the bay, TOC is linearly related to fine particle abundance (r = 0.61). Temporal variability occurs in this relationship, as particles are poor in TOC relative to percent of fine particles in the early rainy season. Iron-poor particles also appear to enter the estuary during high runoff periods; while iron is enriched on particle surfaces in the summer. Concentrations of extractable iron and absorbance of EOM vary strongly from year to year. Highest absorbances of EOM occurred in the first year following the drought in 1976-77, and in 1982 and 1983 when river discharge was unusually high. Extractable-iron concentrations were also highest in 1976-77, but were very low in 1982 and 1983. ?? 1985 Dr W. Junk Publishers.

Nitrogen fluxes across hydrogeomorphic zones in coastal deltaic floodplain using flow-through technique

NASA Astrophysics Data System (ADS)

Li, S.; Twilley, R.; Christensen, A.

2017-12-01

Coastal floodplain deltas are the region of continental margins of major river basins that can remove excess nitrogen before entering the coastal ocean. We propose that the processing of nitrogen in active deltaic wetlands varies with soil organic content in response to different hydrogeomorphic zones. Continuous flow-through core system was used to incubate sediment cores from supratidal, intertidal, and subtidal hydrogeomorphic zones along a chronosequence in Wax Lake Delta during summer of 2017. Ambient water from Wax Lake Outlet was continuously pumped through sealed cores to estimate fluxes of inorganic nitrogen and phosphorus across the sediment-water interface by calculating the difference between inflow and outflow concentrations. The average respiration rate of sediment cores from intertidal zone was about 1.5 g m-2 d-1 while the rate in supratidal zone was more than doubled to 3.7 g m-2 d-1. Under the constant inflow concentration of nitrate (about 107.1 umol/L), sediment cores in supratidal zone exhibited greater NO3- uptake (1329.7 umol m-2 h-1) and N2 release (499.0 umol N m-2 h-1) than that in intertidal zone (421.5 umol m-2 h-1 of NO3- uptake and 67.6 umol N m-2 h-1 of N2 flux respectively). These results indicate greater rate of net denitrification in supratidal zone than intertidal zone in the older chronosequence of the active delta (which formed approximately in 1980). Also, lower NH4 flux (mean 70.0 umol m-2 h-1) from sediment to water column in supratidal zone together with higher NO2- flux (mean 94.2 umol m-2 h-1) illustrated strong signal of nitrification. In conclusion, sediment cores at the intertidal zone helped to remove 12% of NO3- from the water column while cores at supratidal zone removed 35% of NO3-. Based on the correlation between NO3- and N2 fluxes, about 60% of NO3- removed could be converted to N2 under sediment organic concentrations of about 12%. Comparisons of NO3 removal and conversion to N2 by denitrification will be compared along the chronosequence to test the effects of shifts from mineral to organic soils as active deltas develop at the mouths of major river basins.

Mangrove sedimentation and response to relative sea-level rise

USGS Publications Warehouse

Woodroffe, CD; Rogers, K.; Mckee, Karen L.; Lovelock, CE; Mendelssohn, IA; Saintilan, N.

2016-01-01

Mangroves occur on upper intertidal shorelines in the tropics and subtropics. Complex hydrodynamic and salinity conditions influence mangrove distributions, primarily related to elevation and hydroperiod; this review considers how these adjust through time. Accumulation rates of allochthonous and autochthonous sediment, both inorganic and organic, vary between and within different settings. Abundant terrigenous sediment can form dynamic mudbanks; tides redistribute sediment, contrasting with mangrove peat in sediment-starved carbonate settings. Sediments underlying mangroves sequester carbon, but also contain paleoenvironmental records of adjustments to past sea-level changes. Radiometric dating indicates long-term sedimentation, whereas Surface Elevation Table-Marker Horizon measurements (SET-MH) provide shorter perspectives, indicating shallow subsurface processes of root growth and substrate autocompaction. Many tropical deltas also experience deep subsidence, which augments relative sea-level rise. The persistence of mangroves implies an ability to cope with moderately high rates of relative sea-level rise. However, many human pressures threaten mangroves, resulting in continuing decline in their extent throughout the tropics.

Intertidal Concentrations of Microplastics and Their Influence on Ammonium Cycling as Related to the Shellfish Industry.

PubMed

Cluzard, Melanie; Kazmiruk, Tamara N; Kazmiruk, Vasily D; Bendell, L I

2015-10-01

Microplastics are ubiquitous within the marine environment. The last 10 years have seen research directed at understanding the fate and effect of microplastics within the marine environment; however, no studies have yet addressed how concentrations of these particles could affect sedimentary processes such as nutrient cycling. Herein we first determine the concentration and spatial distribution of microplastics within Baynes Sound, a key shellfish-growing area within coastal British Columbia (BC). We also determined sediment grain size and % organic matter (OM) such that we could relate spatial patterns in sediment microplastic concentrations to sedimentary processes that determine zones of accretion and erosion. Using field-determined concentrations of microplastics, we applied laboratory microcosms studies, which manipulated sediment concentrations of microplastics, OM, and bivalves to determine the influence of sediment microplastics on ammonium cycling within intertidal sediments. Concentrations of microplastics determined within the intertidal sediment varied spatially and were similar to those found in other coastal regions of high urban use. Concentrations were independent of grain size and OM suggesting that physical processes other than those that govern natural sediment components determine the fate of microplastics within sediments. Under laboratory conditions, concentrations of ammonium were significantly greater in the overlying water of treatments with microplastics, clams, and OM compared with treatments without microplastics. These preliminary studies suggest that high concentrations of microplastics have the potential to alter key sedimentary processes such as ammonium flux. This could have serious implications, for example, contributing to eutrophication events in regions of the coast that are highly urbanized.

Relationships between microbial communities and environmental parameters at sites impacted by mining of volcanogenic massive sulfide deposits, Prince William Sound, Alaska

USGS Publications Warehouse

Foster, A.L.; Munk, L.; Koski, R.A.; Shanks, Wayne C.; Stillings, L.L.

2008-01-01

The relations among geochemical parameters and sediment microbial communities were examined at three shoreline sites in the Prince William Sound, Alaska, which display varying degrees of impact by acid-rock drainage (ARD) associated with historic mining of volcanogenic massive sulfide deposits. Microbial communities were examined using total fatty acid methyl esters (FAMEs), a class of compounds derived from lipids produced by eukaryotes and prokaryotes (bacteria and Archaea); standard extraction techniques detect FAMEs from both living (viable) and dead (non-viable) biomass, but do not detect Archaeal FAMEs. Biomass and diversity (as estimated by FAMEs) varied strongly as a function of position in the tidal zone, not by study site; subtidal muds, Fe oxyhydroxide undergoing biogenic reductive dissolution, and peat-rich intertidal sediment had the highest values. These estimates were lowest in acid-generating, intertidal zone sediment; if valid, the estimates suggest that only one or two bacterial species predominate in these communities, and/or that Archeal species are important members of the microbial community in this sediment. All samples were dominated by bacterial FAMEs (median value >90%). Samples with the highest absolute abundance of eukaryotic FAMEs were biogenic Fe oxyhydroxides from shallow freshwater pools (fungi) and subtidal muds (diatoms). Eukaryotic FAMEs were practically absent from low-pH, sulfide-rich intertidal zone sediments. The relative abundance of general microbial functional groups such as aerobes/anaerobes and gram(+)/gram(-) was not estimated due to severe inconsistency among the results obtained using several metrics reported in the literature. Principal component analyses (PCAs) were performed to investigate the relationship among samples as separate functions of water, sediment, and FAMEs data. PCAs based on water chemistry and FAMEs data resulted in similar relations among samples, whereas the PCA based on sediment chemistry produced a very different sample arrangement. Specifically, the sediment parameter PCA grouped samples with high bulk trace metal concentration regardless of whether the metals were incorporated into secondary precipitates or primary sulfides. The water chemistry PCA and FAMEs PCA appear to be less prone to this type of artifact. Signature lipids in sulfide-rich sediments could indicate the presence of acid-tolerant and/or acidophilic members of the genus Thiobacillus or they could indicate the presence of SO4-reducing bacteria. The microbial community documented in subtidal and offshore sediments is rich in SRB and/or facultative anaerobes of the Cytophaga-Flavobacterium group; both could reasonably be expected in PWS coastal environments. The results of this study provide evidence for substantial feedback between local (meter to centimeter-scale) geochemical variations, and sediment microbial community composition, and show that microbial community signatures in the intertidal zone are significantly altered at sites where ARD drainage is present relative to sites where it is not, even if the sediment geochemistry indicates net accumulation of ARD-generated trace metals in the intertidal zone. ?? 2007 Elsevier Ltd. All rights reserved.

Sediment transport and deposition on a river-dominated tidal flat: An idealized model study

USGS Publications Warehouse

Sherwood, Christopher R.; Chen, Shih-Nan; Geyer, W. Rockwell; Ralston, David K.

2010-01-01

A 3-D hydrodynamic model is used to investigate how different size classes of river-derived sediment are transported, exported and trapped on an idealized, river-dominated tidal flat. The model is composed of a river channel flanked by sloping tidal flats, a configuration motivated by the intertidal region of the Skagit River mouth in Washington State, United States. It is forced by mixed tides and a pulse of freshwater and sediment with various settling velocities. In this system, the river not only influences stratification but also contributes a significant cross-shore transport. As a result, the bottom stress is strongly ebb-dominated in the channel because of the seaward advance of strong river flow as the tidal flats drain during ebbs. Sediment deposition patterns and mass budgets are sensitive to settling velocity. The lateral sediment spreading scales with an advective distance (settling time multiplied by lateral flow speed), thereby confining the fast settling sediment classes in the channel. Residual sediment transport is landward on the flats, because of settling lag, but is strongly seaward in the channel. The seaward transport mainly occurs during big ebbs and is controlled by a length scale ratio Ld/XWL, where Ld is a cross-shore advective distance (settling time multiplied by river outlet velocity), and XWL is the immersed cross-shore length of the intertidal zone. Sediment trapping requires Ld/XWL < 1, leading to more trapping for the faster settling classes. Sensitivity studies show that including stratification and reducing tidal range both favor sediment trapping, whereas varying channel geometries and asymmetry of tides has relatively small impacts. Implications of the modeling results on the south Skagit intertidal region are discussed.

The Fate of Nitrate in Intertidal Permeable Sediments

PubMed Central

Marchant, Hannah K.; Lavik, Gaute; Holtappels, Moritz; Kuypers, Marcel M. M.

2014-01-01

Coastal zones act as a sink for riverine and atmospheric nitrogen inputs and thereby buffer the open ocean from the effects of anthropogenic activity. Recently, microbial activity in sandy permeable sediments has been identified as a dominant source of N-loss in coastal zones, namely through denitrification. Some of the highest coastal denitrification rates measured so far occur within the intertidal permeable sediments of the eutrophied Wadden Sea. Still, denitrification alone can often account for only half of the substantial nitrate (NO3 −) consumption. Therefore, to investigate alternative NO3 − sinks such as dissimilatory nitrate reduction to ammonium (DNRA), intracellular nitrate storage by eukaryotes and isotope equilibration effects we carried out 15NO3 − amendment experiments. By considering all of these sinks in combination, we could quantify the fate of the 15NO3 − added to the sediment. Denitrification was the dominant nitrate sink (50–75%), while DNRA, which recycles N to the environment accounted for 10–20% of NO3 − consumption. Intriguingly, we also observed that between 20 and 40% of 15NO3 − added to the incubations entered an intracellular pool of NO3 − and was subsequently respired when nitrate became limiting. Eukaryotes were responsible for a large proportion of intracellular nitrate storage, and it could be shown through inhibition experiments that at least a third of the stored nitrate was subsequently also respired by eukaryotes. The environmental significance of the intracellular nitrate pool was confirmed by in situ measurements which revealed that intracellular storage can accumulate nitrate at concentrations six fold higher than the surrounding porewater. This intracellular pool is so far not considered when modeling N-loss from intertidal permeable sediments; however it can act as a reservoir for nitrate during low tide. Consequently, nitrate respiration supported by intracellular nitrate storage can add an additional 20% to previous nitrate reduction estimates in intertidal sediments, further increasing their contribution to N-loss. PMID:25127459

The fate of nitrate in intertidal permeable sediments.

PubMed

Marchant, Hannah K; Lavik, Gaute; Holtappels, Moritz; Kuypers, Marcel M M

2014-01-01

Coastal zones act as a sink for riverine and atmospheric nitrogen inputs and thereby buffer the open ocean from the effects of anthropogenic activity. Recently, microbial activity in sandy permeable sediments has been identified as a dominant source of N-loss in coastal zones, namely through denitrification. Some of the highest coastal denitrification rates measured so far occur within the intertidal permeable sediments of the eutrophied Wadden Sea. Still, denitrification alone can often account for only half of the substantial nitrate (NO3-) consumption. Therefore, to investigate alternative NO3- sinks such as dissimilatory nitrate reduction to ammonium (DNRA), intracellular nitrate storage by eukaryotes and isotope equilibration effects we carried out 15NO3- amendment experiments. By considering all of these sinks in combination, we could quantify the fate of the 15NO3- added to the sediment. Denitrification was the dominant nitrate sink (50-75%), while DNRA, which recycles N to the environment accounted for 10-20% of NO3- consumption. Intriguingly, we also observed that between 20 and 40% of 15NO3- added to the incubations entered an intracellular pool of NO3- and was subsequently respired when nitrate became limiting. Eukaryotes were responsible for a large proportion of intracellular nitrate storage, and it could be shown through inhibition experiments that at least a third of the stored nitrate was subsequently also respired by eukaryotes. The environmental significance of the intracellular nitrate pool was confirmed by in situ measurements which revealed that intracellular storage can accumulate nitrate at concentrations six fold higher than the surrounding porewater. This intracellular pool is so far not considered when modeling N-loss from intertidal permeable sediments; however it can act as a reservoir for nitrate during low tide. Consequently, nitrate respiration supported by intracellular nitrate storage can add an additional 20% to previous nitrate reduction estimates in intertidal sediments, further increasing their contribution to N-loss.

Sediment balance of intertidal mudflats in a macrotidal estuary

NASA Astrophysics Data System (ADS)

lafite, R.; Deloffre, J.; Lemoine, M.

2012-12-01

Intertidal area contributes widely to fine-grained sediment balance in estuarine environments. Their sedimentary dynamics is controlled by several forcing parameters including tidal range, river flow and swell, affected by human activities such as dredging, construction or vessels traffic leading to modify sediment transport pattern. Although the estuarine hydrodynamics is well documented, the link between forcing parameters and these sedimentary processes is weakly understood. One of the main reasons is the difficulty to integrate spatial (from the fluvial to the estuary mouth) and temporal (from swell in seconds to pluriannual river flow variability) patterns. This study achieved on intertidal mudflats distributed along the macrotidal Seine estuary (France) aims (i) to quantify the impact of forcing parameters on each intertidal area respect to its longitudinal position in the estuarine system and (ii) to assess the fine-grained sediment budget at estuarine scale. The Seine estuary is a macrotidal estuary developed over 160 km up the upstream limit of tidal wave penetration. With an average river flow of 450m3.s-1, 80% of the Suspended Particles Matter (SPM) annual flux is discharged during the flood period. In the downstream part, the Seine estuary Turbidity Maximum (TM) is the SPM stock located near the mouth. During their transfer toward the sea, the fine particles can be trapped in (i) the intertidal mudflats; preferential areas characterized by low hydrodynamics and generally sheltered of the tidal dominant flow, the main tidal current the Seine River and (ii) the TM. The Seine estuary is an anthropic estuary in order to secure navigation: one consequence of these developments is the tidal bore disappearance. Along the macrotidal Seine estuary hydrodynamics features and sedimentary fluxes were followed during at least 1 year using respectively Acoustic Doppler Velocimeter, Optical BackScatter and altimeter. Results in the fluvial estuary enhance the role of hydrological cycle that lead to (i) an increased mean water level and (ii) provide SPM from the continental area. This feature leads to significant accretion over intertidal area. In the middle and marine estuary the TM is the main SPM supplier. In these parts of the estuary deposition over these intertidal area is driven by (i) tidal cycle in particular fortnightly cycle link to maximum TM resuspension during (strongest) spring tide and (ii) TM location controlled by river inflow that varies following an annual and inter-annual variability. Outside sedimentation period, the erosion is driven by the combination of (i) progressive erosion driven by fortnightly cycle and (ii) sudden erosion controlled either by wave or boat generated waves respectively at the mouth and in the middle/upper estuary. This last is reinforced by the rheological characteristics of deposit that correspond to fluid/low consolidated mud. During most of the year, the Seine estuary mudflats record an erosion pattern. Significant and intensive sedimentation only occurs few days per year. This pattern is linked to highly variable hydrodynamics conditions (bottom shear stress ranging from 0.5 to 5 N.m-2) that control the sediment supply availability. In this infilling macrotidal anthropized system mudflats are close to equilibrium with an annual rate ranging between +/- 5cm.yrs-1: they act as temporal storage area of fined-grained sediments.

Size-dependent distribution and feeding habits of Terebralia palustris in mangrove habitats of Gazi Bay, Kenya

NASA Astrophysics Data System (ADS)

Pape, Ellen; Muthumbi, Agnes; Kamanu, Chomba Peter; Vanreusel, Ann

2008-03-01

The gastropod Terebralia palustris often dominates the surface of muddy to sandy substrates of intertidal mudflats and mangrove forests, where they clearly destabilize the sediment. In the present study, it was investigated whether and to what extent the behaviour of juvenile and adult snails differs among habitats (mudflat vs. mangrove stand) in a Sonneratia alba mangal at Gazi Bay, Kenya. For this purpose we: (1) examined their distribution along three land-sea transects; and (2) applied stable isotope analysis to determine the feeding patterns of different-sized snails from the mangrove and mudflat habitats. Additionally, we investigated if these gastropods exert an impact on microphytobenthic (diatom) biomass, and whether this is size-dependent. The latter objective was met by either enclosing or excluding different-sized snails from experimental cages on the intertidal mudflat and the subsequent assessment of a change in pigment concentration of the sediment surface. In agreement with several previous studies conducted in other mangroves and geographical locations, a spatial segregation was demonstrated between juveniles (more common on the mudflat) and adults (more common in the mangrove forest). On the intertidal mudflat juveniles avoided sediment patches characterized by highly saline water in intertidal pools and a high mud content, while adults tended to dwell on substrates covered by a high amount of leaf litter. Stable carbon isotope analysis of the foot tissue of snails sampled from the S. alba stand and the mudflat indicated a transition in food source when a shell length of 51 mm is reached. Considering the δ13C value of juveniles, it seems they might be selecting for microphytobenthos, which might explain their preference for the mudflat. The diet of size classes found in both habitats did not differ significantly, although juveniles inhabiting the mangrove forest were slightly more depleted in 13C compared to those residing on the mudflat. Assuming juveniles feed on benthic microalgae and considering the lower microalgal biomass inside the mangrove forest, this may be a consequence of a higher contribution of other, more 13C depleted organic carbon sources, like phytoplankton, to their diet. Experimental results indicate a negative, but insignificant, impact on benthic diatom biomass by juveniles (due to grazing) and adults (due to physical disturbance). This finding seems to be in agreement with the results of the stable carbon isotope analysis, strongly suggesting the selective feeding of juvenile T. palustris on benthic diatoms.

The role of surface and subsurface processes in keeping pace with sea level rise in intertidal wetlands of Moreton Bay, Queensland, Australia

USGS Publications Warehouse

Lovelock, Catherine E.; Bennion, Vicki; Grinham, Alistair; Cahoon, Donald R.

2011-01-01

Increases in the elevation of the soil surfaces of mangroves and salt marshes are key to the maintenance of these habitats with accelerating sea level rise. Understanding the processes that give rise to increases in soil surface elevation provides science for management of landscapes for sustainable coastal wetlands. Here, we tested whether the soil surface elevation of mangroves and salt marshes in Moreton Bay is keeping up with local rates of sea level rise (2.358 mm y-1) and whether accretion on the soil surface was the most important process for keeping up with sea level rise. We found variability in surface elevation gains, with sandy areas in the eastern bay having the highest surface elevation gains in both mangrove and salt marsh (5.9 and 1.9 mm y-1) whereas in the muddier western bay rates of surface elevation gain were lower (1.4 and -0.3 mm y-1 in mangrove and salt marsh, respectively). Both sides of the bay had similar rates of surface accretion (~7–9 mm y-1 in the mangrove and 1–3 mm y-1 in the salt marsh), but mangrove soils in the western bay were subsiding at a rate of approximately 8 mm y-1, possibly due to compaction of organic sediments. Over the study surface elevation increments were sensitive to position in the intertidal zone (higher when lower in the intertidal) and also to variation in mean sea level (higher at high sea level). Although surface accretion was the most important process for keeping up with sea level rise in the eastern bay, subsidence largely negated gains made through surface accretion in the western bay indicating a high vulnerability to sea level rise in these forests.

BENTHIC MICROALGAL CONTROL ON THE NUTRIENT FLUX IN INTER-TIDAL FLATS OF THE LOWER YAQUINA ESTUARY, OREGON

EPA Science Inventory

Three sites were selected across the intertidal zone of the lower Yaquina Bay to investigate the role of benthic microalgae in benthic nutrient fluxes. Study sites were selected where microalage were present but without seagrass or mud shrimp. Sediment columns were collected th...

Variation in biogeochemical parameters across intertidal seagrass meadows in the central Great Barrier Reef region.

PubMed

Mellors, Jane; Waycott, Michelle; Marsh, Helene

2005-01-01

This survey provides baseline information on sediment characteristics, porewater, adsorbed and plant tissue nutrients from intertidal coastal seagrass meadows in the central region of the Great Barrier Reef World Heritage Area. Data collected from 11 locations, representative of intertidal coastal seagrass beds across the region, indicated that the chemical environment was typical of other tropical intertidal areas. Results using two different extraction methods highlight the need for caution when choosing an adsorbed phosphate extraction technique, as sediment type affects the analytical outcome. Comparison with published values indicates that the range of nutrient parameters measured is equivalent to those measured across tropical systems globally. However, the nutrient values in seagrass leaves and their molar ratios for Halophila ovalis and Halodule uninervis were much higher than the values from the literature from this and other regions, obtained using the same techniques, suggesting that these species act as nutrient sponges, in contrast with Zostera capricorni. The limited historical data from this region suggest that the nitrogen and phosphorus content of seagrass leaves has increased since the 1970s concomitant with changing land use practice.

Seagrass Impact on Sediment Exchange Between Tidal Flats and Salt Marsh, and The Sediment Budget of Shallow Bays

NASA Astrophysics Data System (ADS)

Donatelli, Carmine; Ganju, Neil Kamal; Fagherazzi, Sergio; Leonardi, Nicoletta

2018-05-01

Seagrasses are marine flowering plants that strongly impact their physical and biological surroundings and are therefore frequently referred to as ecological engineers. The effect of seagrasses on coastal bay resilience and sediment transport dynamics is understudied. Here we use six historical maps of seagrass distribution in Barnegat Bay, USA, to investigate the role of these vegetated surfaces on the sediment storage capacity of shallow bays. Analyses are carried out by means of the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) numerical modeling framework. Results show that a decline in the extent of seagrass meadows reduces the sediment mass potentially stored within bay systems. The presence of seagrass reduces shear stress values across the entire bay, including unvegetated areas, and promotes sediment deposition on tidal flats. On the other hand, the presence of seagrasses decreases suspended sediment concentrations, which in turn reduces the delivery of sediment to marsh platforms. Results highlight the relevance of seagrasses for the long-term survival of coastal ecosystems, and the complex dynamics regulating the interaction between subtidal and intertidal landscapes.

Organic carbon burial in a mangrove forest, margin and intertidal mud flat

NASA Astrophysics Data System (ADS)

Sanders, Christian J.; Smoak, Joseph M.; Naidu, A. Sathy; Sanders, Luciana M.; Patchineelam, Sambasiva R.

2010-12-01

The flux of total organic carbon (TOC) to depositional facies (intertidal mud flat, margin and forest) was quantified for a tropical mangrove forest in Brazil. Results indicate that these mangrove margins and intertidal mudflats are sites of large TOC accumulation, almost four times greater than the global averages for mangrove forests. The TOC burial rates were determined from organic carbon content in sediment cores which were dated using 210Pb. Burial rates were calculated to be 1129, 949, and 353 (g m -2 yr -1), for the mud flat, margin and forest, respectively. Sediment accumulation rates (SAR) were estimated to be 7.3, 5.0 and 2.8 mm yr -1. Sediment characterization (δ 13C, δ 15N, TOC/TN and mud fraction) indicated a representative mangrove system with a record of consistent organic matter flux of up to 100 years. Because of substantial burial of organic carbon in mangrove ecosystems, their role in the global carbon budget must be considered. More importantly, as climate change influences temperature and sea level, mangrove ecosystems will respond to specific climatic conditions.

Experimental Applications of the Modular Acoustic System for the Submersible ALVIN

DTIC Science & Technology

1975-08-01

surface. Data comparlsoIs can be made with results from other on-site instrumental packages, such as rock hammers and drills , and plankton nets...Massachusetts, and Long Island Sound," J. Sedimentary Petrology 33:723-727. Rhoads, D.C. and 1). J. Stanley (1965). "Biogenic Graded Bedding," J...Sedimentary Petrology 35:956-963. Rhoads, D.C. (1967). "Biogenic Reworking of Intertidal and Sub- tidal Sediments in Barnstable Harbor and Buzzards Bay, Massa

The role of cross-shore tidal dynamics in controlling intertidal sediment exchange in mangroves in Cù Lao Dung, Vietnam

NASA Astrophysics Data System (ADS)

Bryan, Karin R.; Nardin, William; Mullarney, Julia C.; Fagherazzi, Sergio

2017-09-01

Mangroves are halophytic plants common in tropical and sub-tropical environments. Their roots and pneumatophores strongly affect intertidal hydrodynamics and related sediment transport. Here, we investigate the role tree and root structures may play in altering tidal currents and the effect of these currents on the development of intertidal landscapes in mangrove-dominated environments. We use a one-dimensional Delft3D model, forced using typical intertidal slopes and vegetation characteristics from two sites with contrasting slope on Cù Lao Dung within the Mekong Delta in Vietnam, to examine the vegetation controls on tidal currents and suspended sediment transport as the tides propagate into the forest. Model results show that vegetation characteristics at the seaward fringe determine the shape of the cross-shore bottom profile, with sparse vegetation leading to profiles that are close to linear, whereas with dense vegetation resulting in a convex intertidal topography. Examples showing different profile developments are provided from a variety of published studies, ranging from linear profiles in sandier sites, and distinctive convex profiles in muddier sites. As expected, profile differences in the model are caused by increased dissipation due to enhanced drag caused by vegetation; however, the reduction of flow shoreward in sparsely vegetated or non-vegetated cases was similar, indicating that shallowing of the profile and slope effects play a dominant role in dissipation. Here, tidal velocities are measured in the field using transects of Acoustic Doppler Current Profilers, and confirm that cross-shore tidal currents diminish quickly as they move over the fringe of the forest; they then stay fairly consistent within the outer few 100 m of the forest, indicating that the fringing environment is likely a region of deposition. An understanding of how vegetation controls the development of topography is critical to predicting the resilience of these sensitive intertidal areas to changes in inundation caused by sea-level rise.

Heavy metal accumulation during the last 30 years in the Karnaphuli River estuary, Chittagong, Bangladesh.

PubMed

Wang, Ai-Jun; Kawser, Ahmed; Xu, Yong-Hang; Ye, Xiang; Rani, Seema; Chen, Ke-Liang

2016-01-01

Heavy metal contamination of aquatic environment has attracted global attention owing to its abundance, persistence, and environmental toxicity, especially in developing countries like Bangladesh. Five heavy metals, namely chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) were investigated in surface and core sediments of the Karnaphuli River (KR) estuary in Chittagong, Bangladesh, in order to reveal the heavy metal contamination history in estuarine sediments and its response to catastrophic events and human activities. The surface sediment was predominantly composed of silt and sand, and the surface sediment was contaminated with Cr and Pb. Based on the 210 Pb chronology, the sedimentation rate in the inter-tidal zone of KR estuary was 1.02 cm/a before 2007, and 1.14 cm/a after 2008. The core sediment collected from 8 to 20 cm below the surface mainly originated from terrestrial materials induced by catastrophic events such as cyclone, heavy rainfall and landslides in 2007 and 2008. The values of contamination factor ( CF ) showed that the sediment became moderately contaminated with Cr and Pb in the last 30 years. The variation and accumulation of heavy metals in core sediment before 2000 was mainly related to natural variations in sediment sources; however, in subsequent years, the anthropogenic inputs of heavy metals have increased due to rapid physical growth of urban and industrial areas in the Chittagong city. In general, the accumulation pattern of heavy metals after normalization to Aluminum in sediments of KR estuary indicated an accelerated rate of urbanization and industrialization in the last 30 years, and also suggested the influence of natural catastrophic event on estuarine environment.

Interaction between shallow groundwater, saline surface water and contaminant discharge at a seasonally and tidally forced estuarine boundary

NASA Astrophysics Data System (ADS)

Westbrook, S. J.; Rayner, J. L.; Davis, G. B.; Clement, T. P.; Bjerg, P. L.; Fisher, S. J.

2005-02-01

This paper presents findings from a 2-year field investigation of a dissolved hydrocarbon groundwater plume flowing towards a tidally and seasonally forced estuarine river system in Perth, Western Australia. Samples collected from transects of multiport wells along the riverbank and into the river, enabled mapping of the fine scale (0.5 m) vertical definition of the hydrocarbon plume and its longitudinal extent. Spear probing beneath the river sediments and water table, and transient monitoring of multiport wells (electrical conductivity) was also carried out to define the zone of mixing between river water and groundwater (the hyporheic zone) and its variability. The results showed that groundwater seepage into the estuarine surface sediments occurred in a zone less than 10 m from the high tide mark, and that this distance and the hyporheic transition zone were influenced by tidal fluctuations and infiltration of river water into the sediments. The dissolved BTEXN (benzene, toluene, ethylbenzene, the xylene isomers and naphthalene) distributions indicated the behaviour of the hydrocarbon plume at the groundwater/surface water transition zone to be strongly influenced by edge-focussed discharge. Monitoring programs and risk assessment studies at similar contaminated sites should therefore focus efforts within the intertidal zone where contaminants are likely to impact the surface water and shallow sediment environments.

Measurements of gaseous mercury exchanges at the sediment-water, water-atmosphere and sediment-atmosphere interfaces of a tidal environment (Arcachon Bay, France).

PubMed

Bouchet, Sylvain; Tessier, Emmanuel; Monperrus, Mathilde; Bridou, Romain; Clavier, Jacques; Thouzeau, Gerard; Amouroux, David

2011-05-01

The elemental mercury evasion from non-impacted natural areas is of significant importance in the global Hg cycle due to their large spatial coverage. Intertidal areas represent a dynamic environment promoting the transformations of Hg species and their subsequent redistribution. A major challenge remains in providing reliable data on Hg species variability and fluxes under typical transient tidal conditions found in such environment. Field experiments were thus carried out to allow the assessment and comparison of the magnitude of the gaseous Hg fluxes at the three interfaces, sediment-water, sediment-atmosphere and water-atmosphere of a mesotidal temperate lagoon (Arcachon Bay, Aquitaine, France) over three distinct seasonal conditions. The fluxes between the sediment-water and the sediment-atmosphere interfaces were directly evaluated with field flux chambers, respectively static or dynamic. Water-atmosphere fluxes were evaluated from ambient concentrations using a gas exchange model. The fluxes at the sediment-water interface ranged from -5.0 to 5.1 ng m(-2) h(-1) and appeared mainly controlled by diffusion. The occurrence of macrophytic covers (i.e.Zostera noltii sp.) enhanced the fluxes under light radiations. The first direct measurements of sediment-atmosphere fluxes are reported here. The exchanges were more intense and variable than the two other interfaces, ranging between -78 and 40 ng m(-2) h(-1) and were mostly driven by the overlying atmospheric Hg concentrations and superficial sediment temperature. The exchanges between the water column and the atmosphere, computed as a function of wind speed and gaseous mercury saturation ranged from 0.4 to 14.5 ng m(-2) h(-1). The flux intensities recorded over the intertidal sediments periodically exposed to the atmosphere were roughly 2 to 3 times higher than the fluxes of the other interfaces. The evasion of elemental mercury from emerged intertidal sediments is probably a significant pathway for Hg evasion in such tidal environments exhibiting background contamination level.

Population structure, density and food sources of Terebralia palustris (Potamididae: Gastropoda) in a low intertidal Avicennia marina mangrove stand (Inhaca Island, Mozambique)

NASA Astrophysics Data System (ADS)

Penha-Lopes, Gil; Bouillon, Steven; Mangion, Perrine; Macia, Adriano; Paula, José

2009-09-01

Population structure and distribution of Terebralia palustris were compared with the environmental parameters within microhabitats in a monospecific stand of Avicennia marina in southern Mozambique. Stable carbon and nitrogen isotope analyses of T. palustris and potential food sources (leaves, pneumatophore epiphytes, and surface sediments) were examined to establish the feeding preferences of T. palustris. Stable isotope signatures of individuals of different size classes and from different microhabitats were compared with local food sources. Samples of surface sediments 2.5-10 m apart showed some variation (-21.2‰ to -23.0‰) in δ13C, probably due to different contributions from seagrasses, microalgae and mangrove leaves, while δ15N values varied between 8.7‰ and 15.8‰, indicating that there is a very high variability within a small-scale microcosm. Stable isotope signatures differed significantly between the T. palustris size classes and between individuals of the same size class, collected in different microhabitats. Results also suggested that smaller individuals feed on sediment, selecting mainly benthic microalgae, while larger individuals feed on sediment, epiphytes and mangrove leaves. Correlations were found between environmental parameters and gastropod population structure and distribution vs. the feeding preferences of individuals of different size classes and in different microhabitats. While organic content and the abundance of leaves were parameters that correlated best with the total density of gastropods (>85%), the abundance of pneumatophores and leaves, as well as grain size, correlated better with the gastropod size distribution (>65%). Young individuals (height < 3 cm) occur predominantly in microhabitats characterized by a low density of leaf litter and pneumatophores, reduced organic matter and larger grain size, these being characteristic of lower intertidal open areas that favour benthic microalgal growth. With increasing shell height, T. palustris individuals start occupying microhabitats nearer the mangrove trees characterized by large densities of pneumatophores and litter, as well as sediments of smaller grain size, leading to higher organic matter availability in the sediment.

Patterns and Processes in Marine Microeukaryotic Community Biogeography from Xiamen Coastal Waters and Intertidal Sediments, Southeast China

PubMed Central

Chen, Weidong; Pan, Yongbo; Yu, Lingyu; Yang, Jun; Zhang, Wenjing

2017-01-01

Microeukaryotes play key roles in the structure and functioning of marine ecosystems. Little is known about the relative importance of the processes that drive planktonic and benthic microeukaryotic biogeography in subtropical offshore areas. This study compares the microeukaryotic community compositions (MCCs) from offshore waters (n = 12) and intertidal sediments (n = 12) around Xiamen Island, southern China, using high-throughput sequencing of 18S rDNA. This work further quantifies the relative contributions of spatial and environmental variables on the distribution of marine MCCs (including total, dominant, rare and conditionally rare taxa). Our results showed that planktonic and benthic MCCs were significantly different, and the benthic richness (6627 OTUs) was much higher than that for plankton (4044 OTUs) with the same sequencing effort. Further, we found that benthic MCCs exhibited a significant distance-decay relationship, whereas the planktonic communities did not. After removing two unique sites (N2 and N3), however, 72% variation in planktonic community was explained well by stochastic processes. More importantly, both the environmental and spatial factors played significant roles in influencing the biogeography of total and dominant planktonic and benthic microeukaryotic communities, although their relative effects on these community variations were different. However, a high proportion of unexplained variation in the rare taxa (78.1–97.4%) and conditionally rare taxa (49.0–81.0%) indicated that more complex mechanisms may influence the assembly of the rare subcommunity. These results demonstrate that patterns and processes in marine microeukaryotic community assembly differ among the different habitats (coastal water vs. intertidal sediment) and different communities (total, dominant, rare and conditionally rare microeukaryotes), and provide novel insight on the microeukaryotic biogeography and ecological mechanisms in coastal waters and intertidal sediments at local scale. PMID:29075237

Isotopic identification of natural vs. anthropogenic lead sources in marine sediments from the inner Ría de Vigo (NW Spain).

PubMed

Álvarez-Iglesias, P; Rubio, B; Millos, J

2012-10-15

San Simón Bay, the inner part of the Ría de Vigo (NW Spain), an area previously identified as highly polluted by Pb, was selected for the application of Pb stable isotope ratios as a fingerprinting tool in subtidal and intertidal sediment cores. Lead isotopic ratios were determined by inductively coupled plasma mass spectrometry on extracts from bulk samples after total acid digestion. Depth-wise profiles of (206)Pb/(207)Pb, (206)Pb/(204)Pb, (207)Pb/(204)Pb, (208)Pb/(204)Pb and (208)Pb/(207)Pb ratios showed, in general, an upward decrease for both intertidal and subtidal sediments as a consequence of the anthropogenic activities over the last century, or centuries. Waste channel samples from a nearby ceramic factory showed characteristic Pb stable isotope ratios different from those typical of coal and petrol. Natural isotope ratios from non-polluted samples were established for the study area, differentiating sediments from granitic or schist-gneiss sources. A binary mixing model employed on the polluted samples allowed estimating the anthropogenic inputs to the bay. These inputs represented between 25 and 98% of Pb inputs in intertidal samples, and 9-84% in subtidal samples, their contributions varying with time. Anthropogenic sources were apportioned according to a three-source model. Coal combustion-related emissions were the main anthropogenic source Pb to the bay (60-70%) before the establishment of the ceramic factory in the area (in the 1970s) which has since constituted the main source (95-100%), followed by petrol-related emissions. The Pb inputs history for the intertidal area was determined for the 20th century, and, for the subtidal area, the 19th and 20th centuries. Copyright © 2012 Elsevier B.V. All rights reserved.

Sediment environment of Port Valdez, Alaska: the effect of oil on this ecosystem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feder, H.M.; Cheek, M.; Flanagan, P.

1976-07-01

The Port Valdez intertidal sediment system was studied for three years. Physical, geological, geochemical, hydrocarbon, and biological features were examined. Sediments were poorly sorted gravels to plastic clays, and had low amounts of organic matter. Bacterial numbers varied from site to site, and decreased in numbers with depth. Meiofauna consisted primarily of nematodes and harpacticoid copepods. Most meiofaunal species were restricted to the upper three centimeters throughout the year. Meiofaunal densities wre typically highest in summer and lowest in winter. Reproductive activities of copepods tended to be seasonal with only one species reproducing throughout the year. Bacterial populations were unaffectedmore » by single applications. It is concluded that oil is removed rapidly by tidal action. Three species of copepods exposed to oil in the field significantly increased in density in experimentally oiled plots. Uptake and release of added oil by intertidal sediments and the clam (Macoma balthica) were examined in the field. Petroleum was not detectable two months after application to sediments.« less

Assessment of trace metal pollution in sediments and intertidal fauna at the coast of Cameroon.

PubMed

Ngeve, Magdalene N; Leermakers, Martine; Elskens, Marc; Kochzius, Marc

2015-06-01

Coastal systems act as a boundary between land and sea. Therefore, assessing pollutant concentrations at the coast will provide information on the impact that land-based anthropogenic activities have on marine ecosystems. Sediment and fauna samples from 13 stations along the whole coast of Cameroon were analyzed to assess the level of trace metal pollution in sediments and intertidal fauna. Sediments showed enrichment of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn. However, pollution of greater concern was observed for Cd, Cr, Cu, Ni, and Zn at the northern stations. Some sites recorded trace metal levels higher than recommended in sediment quality guidelines. Species diversity was low, and high bioaccumulation of trace metals was observed in biological samples. Some edible gastropod species accumulated trace metals above the safety limits of the World Health Organization, European Medicine Agency, and the US Environment Protection Agency. Although industrial pollution is significant along Cameroon's coast, natural pollution from the volcano Mount Cameroon is also of concern.

[Alternative stable states in coastal intertidal wetland ecosystems of Yangtze estuary, China].

PubMed

Li, Hui; Yuan, Lin; Zhang, Li Quan; Li, Wei; Li, Shi Hua; Zhao, Zhi Yuan

2017-01-01

Alternative stable states phenomenon widely exists in a variety of ecosystems and is closely related to ecosystem health and sustainable development. Although alternative stable states research has become the focus and hotspot of the ecology researches, only a few empirical evidences supported its behavior and mechanisms in coastal wetland ecosystems up to now. In our study, ta-king the intertidal wetland ecosystem in Chongming Dongtan Nature Reserve as study area, we aimed to: 1) test the existence of alternative stable states based on judgment conditions (bimodal characteristic and threshold effect) and determine the relative stable state types; 2) explore the formation mechanisms of alternative stable states by monitoring hydrological conditions, sediment accretion dynamics as well as vegetation growth parameters and analyzing the positive feedbacks between saltmarsh vegetation and sedimentary geomorphology. Our results showed that: 1) Normalized difference vegetation index (NDVI) frequentness distribution revealed obvious bimodality at saltmarsh pioneer zone. Propagule biomass threshold limited the establishment of plant patches representing the "saltmarsh" state. The presence of bimodality and biomass threshold demonstrated there are "mudflat" stable state and "saltmarsh" stable state with distinct structure and function in intertidal wetland ecosystem. 2) Current velocities, turbidities and direction perpendicular to the vegetation zone were the most important factors responsible for the sediments rapid accretion at saltmarsh pioneer zone in spring and summer. Sediments accretion significantly promoted the growth of saltmarsh plant. The positive feedbacks between plant growth and sediments accretion resulted in the formation of alternative stable states. 3) The expansion pattern of saltmarshes in the Chongming Dongtan intertidal wetland ecosystem also suggested that increases of sediments accretion could trigger the formation of "mudflat" stable state and "saltmarsh" stable state on landscape scale. The results from this study could enrich regime shift mechanisms researches and provide the scientific supports for coastal zone protection, restoration and comprehensive management, which could have important theoretical and practical meaning.

Coupled Landscape and Channel Dynamics in the Ganges-Brahmaputra Tidal Deltaplain, Southwest Bangladesh

NASA Astrophysics Data System (ADS)

Bomer, J.; Wilson, C.; Hale, R. P.

2017-12-01

In the Ganges-Brahmaputra Delta (GBD) and other tide-dominated systems, periodic flooding of the land surface during the tidal cycle promotes sediment accretion and surface elevation gain over time. However, over the past several decades, anthropogenic modification of the GBD tidal deltaplain through embankment construction has precluded sediment delivery to catchment areas, leading to widespread channel siltation and subsidence in poldered landscapes. Amongst the current discussion on GBD sustainability, the relationship between tidal inundation period and resultant sedimentation in natural and embanked settings remains unclear. Moreover, an evaluation of how riparian sedimentology and stratigraphic architecture changes across the GBD tidal-fluvial spectrum is notably absent, despite its critical importance in assessing geomorphic change in human-impacted transitional environments. To provide local-scale, longitudinal trends of coupled landscape-channel dynamics, an array of surface elevation tables, groundwater piezometers, and sediment traps deployed in natural and embanked settings have been monitored seasonally over a time span of 4 years. This knowledge base will be extended across the GBD tidal-fluvial transition by collecting sediment cores from carefully selected point bars along the Gorai River. Sediments will be analyzed for lithologic, biostratigraphic, and geochemical properties to provide an integrated framework for discerning depositional zones and associated facies assemblages across this complex transitional environment. Preliminary comparisons of accretion and hydroperiod data suggest that inundation duration strongly governs mass accumulation on the intertidal platform, though other factors such as mass extraction from sediment source and vegetation density may play secondary roles.

The relation of sediment texture to macro- and microplastic abundance in intertidal zone

NASA Astrophysics Data System (ADS)

Wahyuningsih, H.; Bangun, A. P.; Muhtadi, A.

2018-02-01

The intertidal zone is a waters area directly affected by the contamination of plastic debris from land and sea. The aim of this research were to analyze the relation of sediment texture to macro- and micro plastic abundance and also to determine appropriate management strategy. This research was conducted in intertidal zone Jaring Halus Village Langkat Regency North Sumatera Province on February-April 2017. Plastic debris was collected using quadrat transect. Sediment was collected with correct, up to a depth of least 30 cm. Abundance of micro plastic in Station 1 were positively tolerated with clay (0.509), and silt (0.787) and negatively correlations with sand (0.709) Station 2 were positively correlations with sand (0.645) and negatively correlations with clay (0.575), and silt (0.626) Station 3 were positively correlations with clay (0.435), and silt (0.466) and negatively correlations with sand (0.599). The abundance of microplastic was positively correlations with the abundance of microplastic (0.765). Microplastic density is directly proportional to the content of clay and dust. The higher the clay and dust content the higher the micro plastic density.

Assessing the impacts of bait collection on inter-tidal sediment and the associated macrofaunal and bird communities: The importance of appropriate spatial scales.

PubMed

Watson, G J; Murray, J M; Schaefer, M; Bonner, A; Gillingham, M

2017-09-01

Bait collection is a multibillion dollar worldwide activity that is often managed ineffectively. For managers to understand the impacts on protected inter-tidal mudflats and waders at appropriate spatial scales macrofaunal surveys combined with video recordings of birds and bait collectors were undertaken at two UK sites. Dug sediment constituted approximately 8% of the surveyed area at both sites and is less muddy (lower organic content) than undug sediment. This may have significant implications for turbidity. Differences in the macrofaunal community between dug and undug areas if the same shore height is compared as well as changes in the dispersion of the community occurred at one site. Collection also induces a 'temporary loss of habitat' for some birds as bait collector numbers negatively correlate with wader and gull abundance. Bait collection changes the coherence and ecological structure of inter-tidal mudflats as well as directly affecting wading birds. However, as β diversity increased we suggest that management at appropriate hectare/site scales could maximise biodiversity/function whilst still supporting collection. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Dynamics of sediment carbon stocks across intertidal wetland habitats of Moreton Bay, Australia.

PubMed

Hayes, Matthew A; Jesse, Amber; Hawke, Bruce; Baldock, Jeff; Tabet, Basam; Lockington, David; Lovelock, Catherine E

2017-10-01

Coastal wetlands are known for high carbon storage within their sediments, but our understanding of the variation in carbon storage among intertidal habitats, particularly over geomorphological settings and along elevation gradients, is limited. Here, we collected 352 cores from 18 sites across Moreton Bay, Australia. We assessed variation in sediment organic carbon (OC) stocks among different geomorphological settings (wetlands within riverine settings along with those with reduced riverine influence located on tide-dominated sand islands), across elevation gradients, with distance from shore and among habitat and vegetation types. We used mid-infrared (MIR) spectroscopy combined with analytical data and partial least squares regression to quantify the carbon content of ~2500 sediment samples and provide fine-scale spatial coverage of sediment OC stocks to 150 cm depth. We found sites in river deltas had larger OC stocks (175-504 Mg/ha) than those in nonriverine settings (44-271 Mg/ha). Variation in OC stocks among nonriverine sites was high in comparison with riverine and mixed geomorphic settings, with sites closer to riverine outflow from the east and south of Moreton Bay having higher stocks than those located on the sand islands in the northwest of the bay. Sediment OC stocks increased with elevation within nonriverine settings, but not in riverine geomorphic settings. Sediment OC stocks did not differ between mangrove and saltmarsh habitats. OC stocks did, however, differ between dominant species across the research area and within geomorphic settings. At the landscape scale, the coastal wetlands of the South East Queensland catchments (17,792 ha) are comprised of approximately 4,100,000-5,200,000 Mg of sediment OC. Comparatively high variation in OC storage between riverine and nonriverine geomorphic settings indicates that the availability of mineral sediments and terrestrial derived OC may exert a strong influence over OC storage potential across intertidal wetland systems. © 2017 John Wiley & Sons Ltd.

Microplastics in coastal environments of the Arabian Gulf.

PubMed

Abayomi, Oyebamiji Abib; Range, Pedro; Al-Ghouti, Mohammad A; Obbard, Jeffrey Philip; Almeer, Saeed Hashim; Ben-Hamadou, Radhouane

2017-11-15

Eight sandy beaches along the coastline of Qatar and four sea surface stations on the eastern coast, adjacent to Doha Bay, were surveyed between December 2014 and March 2015. Microplastics, mainly low density polyethylene and polypropylene, were found in all samples of sediments and seawater. Blue fibers, ranging between 1 and 5mm, were the dominant type of particle present. Abundances on the sea surface varied between 4.38×10 4 and 1.46×10 6 particles·km -2 , with the highest values being consistently found 10km offshore, suggesting the presence of a convergence zone. No significant temporal variability was detected for sea surface samples. The concentration of microplastics in intertidal sediments varied between 36 and 228particlesm -2 , with no significant differences among the 8 beaches examined. These results show the pervasiveness of microplastic pollution in coastal environments of the Arabian Gulf. Potential local sources and sinks for microplastics are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state

EPA Science Inventory

A mixing model derived from first principles describes the bulk density (BD) of intertidal wetland sediments as a function of loss on ignition (LOI). The model assumes the bulk volume of sediment equates to the sum of self-packing volumes of organic and mineral components or BD =...

Tidal variability in benthic silicic acid fluxes and microphytobenthos uptake in intertidal sediment

NASA Astrophysics Data System (ADS)

Leynaert, Aude; Longphuirt, Sorcha Ní; An, Soonmo; Lim, Jae-Hyun; Claquin, Pascal; Grall, Jacques; Kwon, Bong Oh; Koh, Chul Hwan

2011-11-01

Silicic acid (DSi) benthic fluxes play a major role in the benthic-pelagic coupling of coastal ecosystems. They can sustain microphytobenthos (MPB) development at the water-sediment interface and support pelagic diatoms when river DSi inputs decrease. DSi benthic fluxes have been studied at the seasonal scale but little is known about their dial variations. This study measured the amplitude of such variations in an intertidal area over an entire tidal cycle by following the alteration of DSi pore water concentrations at regular intervals over the flood/ebb period. Furthermore we independently estimated the potential DSi uptake by benthic diatoms and compared it to the variations of DSi pore water concentrations and fluxes. The microphytobenthos DSi demand was estimated from primary production measurements on cells extracted from the sediment. There were large changes in DSi pore water concentration and a prominent effect of tidal pumping: the DSi flushed out from the sediment at rising tide, occurs in a very short period of time, but plays a far more important role in fueling the ecosystem (800 μmol-Si m -2 d -1), than diffusive fluxes occurring throughout the rest of the tidal cycle (2 μmol-Si m -2 d -1). This process is not, to our knowledge, currently considered when describing the DSi cycling of intertidal sediments. Moreover, there was a large potential MPB requirement for DSi (812 μmol-Si m -2 d -1), similar to the advective flow periodically pumped by the incoming tide, and largely exceeded benthic diffusive fluxes. However, this DSi uptake by benthic diatoms is almost undetectable given the variation of DSi concentration profiles within the sediment.

Burrowing Criteria and Burrowing Mode Adjustment in Bivalves to Varying Geoenvironmental Conditions in Intertidal Flats and Beaches

PubMed Central

Sassa, Shinji; Watabe, Yoichi; Yang, Soonbo; Kuwae, Tomohiro

2011-01-01

The response of bivalves to their abiotic environment has been widely studied in relation to hydroenvironmental conditions, sediment types and sediment grain sizes. However, the possible role of varying geoenvironmental conditions in their habitats remains poorly understood. Here, we show that the hardness of the surficial intertidal sediments varies by a factor of 20–50 due to suction development and suction-induced void state changes in the essentially saturated states of intertidal flats and beaches. We investigated the response of two species of bivalves, Ruditapes philippinarum and Donax semigranosus, in the laboratory by simulating such prevailing geoenvironmental conditions in the field. The experimental results demonstrate that the bivalve responses depended strongly on the varying geoenvironmental conditions. Notably, both bivalves consistently shifted their burrowing modes, reducing the burrowing angle and burial depth, in response to increasing hardness, to compensate for the excessive energy required for burrowing, as explained by a proposed conceptual model. This burrowing mode adjustment was accompanied by two burrowing criteria below or above which the bivalves accomplished vertical burrowing or failed to burrow, respectively. The suitable and fatal conditions differed markedly with species and shell lengths. The acute sensitivities of the observed bivalve responses to geoenvironmental changes revealed two distinctive mechanisms accounting for the adult–juvenile spatial distributions of Ruditapes philippinarum and the behavioral adaptation to a rapidly changing geoenvironment of Donax semigranosus. The present results may provide a rational basis by which to understand the ensuing, and to predict future, bivalve responses to geoenvironmental changes in intertidal zones. PMID:21957474

Oyster Saccostrea cucullata as a biomonitor for Hg contamination and the risk to humans on the coast of Qeshm Island, Persian Gulf, Iran.

PubMed

Shirneshan, Golshan; Bakhtiari, Alireza Riyahi; Kazemi, Ali; Mohamadi, Mohsen; Kheirabadi, Nabiallah

2012-06-01

A total of 174 individuals of rocky oysters (Saccostrea cucullata) and 35 surface sediment samples were collected from seven stations off the intertidal zones of Qeshm Island, Persian Gulf, in order to study the concentration of mercury in oysters' tissues, and to investigate whether mercury concentrations in the edible soft tissues are within the permissible limits for public health. The average mercury concentrations were found as 3.44, 50.66 and 2.29 μg kg(-1) dw in the sediments, soft tissues and shells of the oysters, respectively. Results indicated that the levels of mercury in sediment differed significantly between the stations. In addition, results confirmed that the soft tissues of oysters could be a good indicator of mercury in the aquatic system. In comparison with food safety standards, mercury levels in oysters were well within the permissible limits for human consumption.

Microplastic contamination of intertidal sediments of Scapa Flow, Orkney: A first assessment.

PubMed

Blumenröder, J; Sechet, P; Kakkonen, J E; Hartl, M G J

2017-11-15

The concentration of microplastic particles and fibres was determined in the intertidal sediments at selected sites in Scapa Flow, Orkney, using a super-saturated NaCl flotation technique to extract the plastic and FT-IR spectroscopy to determine the polymer types. Mean concentrations were 730 and 2300kg -1 sediment (DW), respectively. Detailed spatial and quantitative analysis revealed that their distribution was a function of proximity to populated areas and associated wastewater effluent, industrial installations, degree of shore exposure and complex tidal flow patterns. Sediment samples from Orkney showed similar levels of microplastic contamination as in two highly populate industrialized mainland UK areas, The Clyde and the Firth of Forth. It was concluded that relative remoteness and a comparative small island population are not predictors of lower microplastic pollution. Furthermore, a larger concerted effort across Scotland and the UK is required to establish a baseline microplastic database for the evaluation of future policy measures. Copyright © 2017 Elsevier Ltd. All rights reserved.

Organic carbon accumulation in Brazilian mangal sediments

NASA Astrophysics Data System (ADS)

Sanders, Christian J.; Smoak, Joseph M.; Sanders, Luciana M.; Sathy Naidu, A.; Patchineelam, Sambasiva R.

2010-12-01

This study reviews the organic carbon (OC) accumulation rates in mangrove forests, margins and intertidal mudflats in geographically distinct areas along the Brazilian coastline (Northeastern to Southern). Our initial results indicate that the mangrove forests in the Northeastern region of Brazil are accumulating more OC (353 g/m 2/y) than in the Southeastern areas (192 g/m 2/y) being that the sediment accumulation rates, 2.8 and 2.5 mm/y, and OC content ˜7.1% and ˜5.8% (dry sediment weight) were contributing factors to the discrepancies between the forests. The intertidal mudflats on the other hand showed substantially greater OC accumulation rates, sedimentation rates and content 1129 g/m 2/y and 234 g/m 2/y; 7.3 and 3.4 mm/y; 10.3% and ˜2.7% (OC of dry sediment weight content), respectively, in the Northeastern compared to the Southeastern region. Mangrove forests in the South-Southeastern regions of Brazil may be more susceptible to the rising sea level, as they are geographically constricted by the vast mountain ranges along the coastline.

Sediment Trapping Pathways and Mechanisms through the Mekong Tidal River and Subaqueous Delta

DTIC Science & Technology

2013-09-30

strive to understand how the delicate balance of ebb and flood sediment fluxes is maintained to create tidal flat and mangrove complexes, and...subaqueous delta on the inner continental shelf, and sediment sinks within vegetated/ mangrove shoreline complexes. Our overall hypothesis is that sediment... Mangrove /Vegetated Intertidal Areas. Along the main stem tidal river and coastal banks may be shorelines lined with vegetation ( mangroves at the

Sea level and turbidity controls on mangrove soil surface elevation change

USGS Publications Warehouse

Lovelock, Catherine E.; Fernanda Adame, Maria; Bennion, Vicki; Hayes, Matthew; Reef, Ruth; Santini, Nadia; Cahoon, Donald R.

2015-01-01

Increases in sea level are a threat to seaward fringing mangrove forests if levels of inundation exceed the physiological tolerance of the trees; however, tidal wetlands can keep pace with sea level rise if soil surface elevations can increase at the same pace as sea level rise. Sediment accretion on the soil surface and belowground production of roots are proposed to increase with increasing sea level, enabling intertidal habitats to maintain their position relative to mean sea level, but there are few tests of these predictions in mangrove forests. Here we used variation in sea level and the availability of sediments caused by seasonal and inter-annual variation in the intensity of La Nina-El Nino to assess the effects of increasing sea level on surface elevation gains and contributing processes (accretion on the surface, subsidence and root growth) in mangrove forests. We found that soil surface elevation increased with mean sea level (which varied over 250 mm during the study) and with turbidity at sites where fine sediment in the water column is abundant. In contrast, where sediments were sandy, rates of surface elevation gain were high, but not significantly related to variation in turbidity, and were likely to be influenced by other factors that deliver sand to the mangrove forest. Root growth was not linked to soil surface elevation gains, although it was associated with reduced shallow subsidence, and therefore may contribute to the capacity of mangroves to keep pace with sea level rise. Our results indicate both surface (sedimentation) and subsurface (root growth) processes can influence mangrove capacity to keep pace with sea level rise within the same geographic location, and that current models of tidal marsh responses to sea level rise capture the major feature of the response of mangroves where fine, but not coarse, sediments are abundant.

The effect of vegetation height and biomass on the sediment budget of a European saltmarsh

NASA Astrophysics Data System (ADS)

Reef, Ruth; Schuerch, Mark; Christie, Elizabeth K.; Möller, Iris; Spencer, Tom

2018-03-01

Sediment retention in saltmarshes is often attributed to the presence of vegetation, which enhances accretion by slowing water flow, reduces erosion by attenuating wave energy and increases surface stability through the presence of organic matter. Saltmarsh vegetation morphology varies considerably on a range of spatial and temporal scales, but the effect of different above ground morphologies on sediment retention is not well characterised. Understanding the biophysical interaction between the canopy and sediment trapping in situ is important for improving numerical shoreline models. In a novel field flume study, we measured the effect of vegetation height and biomass on sediment trapping using a mass balance approach. Suspended sediment profilers were placed at both openings of a field flume built across-shore on the seaward boundary of an intertidal saltmarsh in the Dengie Peninsula, UK. Sequential removal of plant material from within the flume resulted in incremental loss of vegetation height and biomass. The difference between the concentration of suspended sediment measured at each profiler was used to determine the sediment budget within the flume. Deposition of material on the plant/soil surfaces within the flume occurred during flood tides, while ebb flow resulted in erosion (to a lesser degree) from the flume area, with a positive sediment budget of on average 6.5 g m-2 tide-1 with no significant relationship between sediment trapping efficiency and canopy morphology. Deposition (and erosion) rates were positively correlated to maximum inundation depth. Our results suggest that during periods of calm conditions, changes to canopy morphology do not result in significant changes in sediment budgets in marshes.

Natural disturbance shapes benthic intertidal macroinvertebrate communities of high latitude river deltas

USGS Publications Warehouse

Churchwell, Roy T.; Kendall, Steve J.; Blanchard, Amy L.; Dunton, Kenneth H.; Powell, Abby N.

2016-01-01

Unlike lower latitude coastlines, the estuarine nearshore zones of the Alaskan Beaufort Sea are icebound and frozen up to 9 months annually. This annual freezing event represents a dramatic physical disturbance to fauna living within intertidal sediments. The main objectives of this study were to describe the benthic communities of Beaufort Sea deltas, including temporal changes and trophic structure. Understanding benthic invertebrate communities provided a baseline for concurrent research on shorebird foraging ecology at these sites. We found that despite continuous year-to-year episodes of annual freezing, these estuarine deltas are populated by a range of invertebrates that represent both marine and freshwater assemblages. Freshwater organisms like Diptera and Oligochaeta not only survive this extreme event, but a marine invasion of infaunal organisms such as Amphipoda and Polychaeta rapidly recolonizes the delta mudflats following ice ablation. These delta sediments of sand, silt, and clay are fine in structure compared to sediments of other Beaufort Sea coastal intertidal habitats. The relatively depauperate invertebrate community that ultimately develops is composed of marine and freshwater benthic invertebrates. The composition of the infauna also reflects two strategies that make life on Beaufort Sea deltas possible: a migration of marine organisms from deeper lagoons to the intertidal and freshwater biota that survive the 9-month ice-covered period in frozen sediments. Stable isotopic analyses reveal that both infaunal assemblages assimilate marine and terrestrial sources of organic carbon. These results provide some of the first quantitative information on the infaunal food resources of shallow arctic estuarine systems and the long-term persistence of these invertebrate assemblages. Our data help explain the presence of large numbers of shorebirds in these habitats during the brief summer open-water period and their trophic importance to migrating waterfowl and nearshore populations of estuarine fishes that are the basis of subsistence lifestyles by native inhabitants of the Beaufort Sea coast.

Restoring Ecological Function to a Submerged Salt Marsh

USGS Publications Warehouse

Stagg, C.L.; Mendelssohn, I.A.

2010-01-01

Impacts of global climate change, such as sea level rise and severe drought, have altered the hydrology of coastal salt marshes resulting in submergence and subsequent degradation of ecosystem function. A potential method of rehabilitating these systems is the addition of sediment-slurries to increase marsh surface elevation, thus ameliorating effects of excessive inundation. Although this technique is growing in popularity, the restoration of ecological function after sediment addition has received little attention. To determine if sediment subsidized salt marshes are functionally equivalent to natural marshes, we examined above- and belowground primary production in replicated restored marshes receiving four levels of sediment addition (29-42 cm North American Vertical Datum of 1988 [NAVD 88]) and in degraded and natural ambient marshes (4-22 cm NAVD 88). Moderate intensities of sediment-slurry addition, resulting in elevations at the mid to high intertidal zone (29-36 cm NAVD 88), restored ecological function to degraded salt marshes. Sediment additions significantly decreased flood duration and frequency and increased bulk density, resulting in greater soil drainage and redox potential and significantly lower phytotoxic sulfide concentrations. However, ecological function in the restored salt marsh showed a sediment addition threshold that was characterized by a decline in primary productivity in areas of excessive sediment addition and high elevation (>36 cm NAVD 88). Hence, the addition of intermediate levels of sediment to submerging salt marshes increased marsh surface elevation, ameliorated impacts of prolonged inundation, and increased primary productivity. However, too much sediment resulted in diminished ecological function that was equivalent to the submerged or degraded system. ?? 2010 Society for Ecological Restoration International.

Microplastic-associated Bacterial Assemblages in the Intertidal Zone

NASA Astrophysics Data System (ADS)

Jiang, P.; Zhao, S.; Zhu, L.; Li, D.

2017-12-01

Plastic debris is posing a planetary-scale threat. As a zone where terrestrial and marine ecosystems interactions occur, the accumulation of plastic marine debris (PMD) in intertidal environments has been well documented. But the information of plastic-associated microbial community (the "Plastisphere") in the intertidal zone is scanty. Utilizing the high-throughput sequencing, we profiled the bacterial communities attached to microplastic samples from the intertidal locations around Yangtze estuary. The structure and composition of Plastisphere communities in current study varied significantly with geographical stations. The taxonomic composition on microplastic samples implied their sedimental and aquatic origins. Some members of hydrocarbon degrading microorganisms and potential pathogens were detected on microplastic. Overall, our findings fuel the evidence for the occurrence of diverse microbial assemblages on PMD and improving our understanding of Plastisphere ecology, which could support the management action and policy change related to PMD.

Environmental background values of trace elements in sediments from the Jiaozhou Bay catchment, Qingdao, China.

PubMed

Xu, Fangjian; Liu, Zhaoqing; Yuan, Shengqiang; Zhang, Xilin; Sun, Zhilei; Xu, Feng; Jiang, Zuzhou; Li, Anchun; Yin, Xuebo

2017-08-15

Selected trace elements (As, Cr, Zn, Cu, Cd, Co, Pb and Ni) in 76 surface sediment samples collected from the rivers and the intertidal zone of Jiaozhou Bay (JZB) were evaluated to assess their environmental background values in the JZB catchment. Overall, the sediment quality in the area meets the China Marine Sediment Quality criteria. The background values (ranges) of the elements As, Cr, Zn, Cu, Cd, Co, Pb and Ni were, respectively, 8.28 (4.10-12.46), 67.96 (38.40-97.52), 56.80 (16.42-196.51), 19.13 (5.71-64.06), 0.10 (0.02-0.42), 6.51 (2.08-20.40), 17.97 (12.26-55.84) and 20.69 (10.43-30.95)mg/kg. The background values of most of the trace elements were lower than those in Chinese soil, the upper continental crust, global shales and global preindustrial sediments. The results may assist in defining future coastal and river management measures specifically targeted at monitoring trace element contamination in the JZB catchment. Copyright © 2017 Elsevier Ltd. All rights reserved.

ELEVATED DISSOLVED SULFIDES IN SURFICIAL SEDIMENTS OF YAQUINA BAY ESTUARY, OREGON

EPA Science Inventory

Dissolved sulfide concentrations were measured in porewater of surficial sediments collected from two exposed intertidal sites in Yaquina Bay, Oregon. Idaho Pt. (IP) is an area where drift green macroalgae is known to accumulate, and the odor of hydrogen sulfide gas (H2S) on th...

Demethylation and cleavage of dimethylsulfoniopropionate in marine intertidal sediments

USGS Publications Warehouse

Visscher, P.T.; Kiene, R.P.; Taylor, B.F.

1994-01-01

Demethylation and cleavage of dimethylsulfoniopropionate (DMSP) was measured in three different types of,intertidal marine sediments: a cyanobacterial mat, a diatom-covered tidal flat and a carbonate sediment. Consumption rates of added DMSP were highest in cyanobacterial mat slurries (59 ?? mol DMSP l-1 slurry h-1) and lower in slurries from a diatom mat and a carbonate tidal sediment (24 and 9 ??mol DMSP l-1 h-1, respectively). Dimethyl sulfide (DMS) and 3-mercaptopropionate (MPA) were produced simultaneously during DMSP consumption, indicating that cleavage and demethylation occurred at the same time. Viable counts of DMSP-utilizing bacteria revealed a population of 2 x 107 cells cm-3 sediment (90% of these cleaved DMSP to DMS, 10% demethylated DMSP to MPA) in the cyanobacterial mat, 7 x 105 cells cm-3 in the diatom mat (23% cleavers, 77% demethylators), and 9 x 104 cells cm-3 (20% cleavers and 80% demethylators) in the carbonate sediment. In slurries of the diatom mat, the rate of MPA production from added 3-methiolpropionate (MMPA) was 50% of the rate of MPA formation from DMSP. The presence of a large population of demethylating bacteria and the production of MPA from DMSP suggest that the demethylation pathway, in addition to cleavage, contributes significantly to DMSP consumption in coastal sediments.

A High-Level Fungal Diversity in the Intertidal Sediment of Chinese Seas Presents the Spatial Variation of Community Composition.

PubMed

Li, Wei; Wang, Mengmeng; Bian, Xiaomeng; Guo, Jiajia; Cai, Lei

2016-01-01

The intertidal region is one of the most dynamic environments in the biosphere, which potentially supports vast biodiversity. Fungi have been found to play important roles in marine ecosystems, e.g., as parasites or symbionts of plants and animals, and as decomposers of organic materials. The fungal diversity in intertidal region, however, remains poorly understood. In this study, sediment samples from various intertidal habitats of Chinese seas were collected and investigated for determination of fungal community and spatial distribution. Through ribosomal RNA internal transcribed spacer-2 (ITS2) metabarcoding, a high-level fungal diversity was revealed, as represented by 6,013 OTUs that spanned six phyla, 23 classes, 84 orders and 526 genera. The presence of typical decomposers (e.g., Corollospora in Ascomycota and Lepiota in Basidiomycota) and pathogens (e.g., Olpidium in Chytriomycota, Actinomucor in Zygomycota and unidentified Rozellomycota spp.), and even mycorrhizal fungi (e.g., Glomus in Glomeromycota) indicated a complicated origin of intertidal fungi. Interestingly, a small proportion of sequences were classified to obligate marine fungi (e.g., Corollospora, Lignincola, Remispora, Sigmoidea ). Our data also showed that the East China Sea significantly differed from other regions in terms of species richness and community composition, indicating a profound effect of the huge discharge of the Yangtze River. No significant difference in fungal communities was detected, however, among habitat types (i.e., aquaculture, dock, plant, river mouth and tourism). These observations raise further questions on adaptation of these members to environments and the ecological functions they probably perform.

A High-Level Fungal Diversity in the Intertidal Sediment of Chinese Seas Presents the Spatial Variation of Community Composition

PubMed Central

Li, Wei; Wang, Mengmeng; Bian, Xiaomeng; Guo, Jiajia; Cai, Lei

2016-01-01

The intertidal region is one of the most dynamic environments in the biosphere, which potentially supports vast biodiversity. Fungi have been found to play important roles in marine ecosystems, e.g., as parasites or symbionts of plants and animals, and as decomposers of organic materials. The fungal diversity in intertidal region, however, remains poorly understood. In this study, sediment samples from various intertidal habitats of Chinese seas were collected and investigated for determination of fungal community and spatial distribution. Through ribosomal RNA internal transcribed spacer-2 (ITS2) metabarcoding, a high-level fungal diversity was revealed, as represented by 6,013 OTUs that spanned six phyla, 23 classes, 84 orders and 526 genera. The presence of typical decomposers (e.g., Corollospora in Ascomycota and Lepiota in Basidiomycota) and pathogens (e.g., Olpidium in Chytriomycota, Actinomucor in Zygomycota and unidentified Rozellomycota spp.), and even mycorrhizal fungi (e.g., Glomus in Glomeromycota) indicated a complicated origin of intertidal fungi. Interestingly, a small proportion of sequences were classified to obligate marine fungi (e.g., Corollospora, Lignincola, Remispora, Sigmoidea). Our data also showed that the East China Sea significantly differed from other regions in terms of species richness and community composition, indicating a profound effect of the huge discharge of the Yangtze River. No significant difference in fungal communities was detected, however, among habitat types (i.e., aquaculture, dock, plant, river mouth and tourism). These observations raise further questions on adaptation of these members to environments and the ecological functions they probably perform. PMID:28066402

Trace metals, PCBs, and PAHs in benthic (epipelic) diatoms from intertidal sediments; a pilot study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stronkhorst, J.; Misdorp, R.; Vos, P.C.

1994-06-01

Intertidal sediments in many estuaries around the world have a history of contamination resulting from long term discharges of industrial, agricultural and domestic waste effluents. These contaminated sediments are now regarded as a major source of toxicants for bottom-related organisms which, in turn, may pass on certain contaminants (e.g. methylmercury, polychlorinated biphenyls (PCBs)) to organisms higher in the foodchain. Many studies have been conducted on the contamination of benthic macrofauna, estuarine fish and birds, but to our knowledge no research has yet been carried out on benthic diatoms which form the lowest trophic level of an intertidal ecosystem. Research onmore » the effects of micro-contaminants on primary producers in marine ecosystems is mainly performed with phytoplankton. In the estuaries of temperate regions, benthic diatoms make a significant contribution to primary production in the ecosystem and are predated especially by deposit feeding Polychaete and Mollusca. Knowledge of the level of contamination in benthic diatoms is of major importance to recognize possible effects on growth rate and species composition of the benthic diatom populations and to understand the accumulation of toxicants into the foodchain. For chemical analysis it is difficult to obtain [open quote]pure[close quote] samples of benthic diatoms because they form part of the sediment. A similar problem occurs with the sampling of phytoplankton in turbid estuarine waters. The aim of this pilot study was (a) to improve a trap technique to collect pure samples of benthic diatoms of at least 2 gram dry weight for analysis of trace metals, PCBs and polyaromatic hydrocarbons (PAHs) and (b) to compare the concentrations in benthic diatoms with levels in sediment and some bottom-related organisms. 16 refs., 2 figs., 2 tabs.« less

Appendix D: Use of wave scenarios to assess potential submerged oil mat (SOM) formation along the coast of Florida and Alabama

USGS Publications Warehouse

Dalyander, P. Soupy; Long, Joseph W.; Plant, Nathaniel G.; Thompson, David M.

2013-01-01

During the Deepwater Horizon oil spill, oil in the surf zone mixed with sediment in the surf zone to form heavier-than-water sediment oil agglomerates of various size, ranging from small (cm-scale) pieces (surface residual balls, SRBs) to large mats (100-m scale, surface residue mats, SR mats). Once SR mats formed in the nearshore or in the intertidal zone, they may have become buried by sand moving onshore or alongshore. To assist in locating possible sites of buried oil, wave scenarios previously developed by the U.S. Geological Survey (USGS) were used to determine the depths at which surface oil had the potential to mix with suspended sediment. For sediment to mix with floating oil and form an agglomerate of sufficient density to sink to the seafloor, either the water must be very shallow (e.g., within the swash zone) or sediment must be suspended to the water surface in sufficient concentrations to create a denser-than-sea water agglomerate. The focus of this study is to analyze suspended sediment mixing with surface oil in depths beyond the swash zone, in order to define the seaward limit of mat formation. A theoretical investigation of sediment dynamics in the nearshore zone revealed that non-breaking waves do not suspend enough sediment to the surface to form sinking sand/oil agglomerates. For this study, it was assumed that the cross-shore distribution of potential agglomerate formation is associated with the primary breaker line, and the presence of plunging breakers, over the time frame of oiling. The potential locations of submerged oil mats (SOMs) are sites where (1) possible agglomerate formation occurred, where (2) sediment accreted post-oiling and buried the SOM, and where (3) the bathymetry has not subsequently eroded to re-expose any mat that may have formed at that site. To facilitate identification of these locations, the range of water level variation over the time frame of oiling was also prescribed, which combined with the wave-breaking depth analysis and pre-oiling bathymetry would identify the potential geographic locations of SOMs.

Physical properties of muddy sediments from French Guiana

NASA Astrophysics Data System (ADS)

Caillaud, J.; Lesourd, L.; Philippe, S.; Gontharet, S.; Sarrazin, M.; Gardel, A.

2017-01-01

The North West migration of long and discontinuous mud banks along the French Guiana coast has been extensively studied during the past years, in particular with a large-scale vision, which consequently has integrated morpho and hydrodynamic data. The aims of the present paper were to use intrinsic sediment properties (grain-size, mineralogy, concentration, and cohesion) to (1) highlight the sedimentary conditions during the consolidation processes from fluid deposit to vegetation development, and (2) verify the apparent homogeneously derived sedimentary facies. Two intertidal transects, Macouria and Cayenne, were compared from the coast to offshore. Their altitude averages of 1 m and 2.8 m above mean sea level, respectively, were different enough to compare the influence of the hydrodynamic impact and emersion time on their sediment properties. The latter, i.e. grain size distribution, mineralogical content, mud concentration, and shear strength (cohesion), were determined from sampled surface sediments (first cm) and along sediment cores (20-30 cm depth) from each transect. A specific X-ray technique was applied to the whole core to differentiate clearly its thin layers. On both intertidal sites, the grain size dominated by the fine silt fraction (2-20 μm) and the bulk mineralogy characterized by five major minerals (quartz, feldspars, chlorite, illite, and kaolinite) appeared homogeneous along both transects and cores. In spite of this apparent uniformity of particle size and mineralogical parameters, as well as for visual observation along the core, high precision X-rays still showed a cyclic sedimentation at a micro-scale level. This cyclicity with intercalation of fine layers was related to distinct dynamic deposits marked by both tidal processes and hydrodynamic factors (swell propagation). The cohesion and concentration results were dependent on the topography, where high topography was characterized by sediments with high cohesion and concentration values, and vice versa. A comparison between these two parameters was done to define critical limits between soft and stiff muds, as well as unvegetated and colonized muds. The favorable intrinsic sedimentary properties for consolidation and colonization were also discussed according to the field observations and bibliographic data.

Facies analysis of Lofer cycles (Upper Triassic), in the Argolis Peninsula (Greece)

NASA Astrophysics Data System (ADS)

Pomoni-Papaioannou, F.

The Upper Triassic carbonate sediments of Argolis Peninsula are part of the Upper Triassic-Lower Jurassic extensive and thick neritic carbonate formations (Pantokrator facies) that formed at the passive Pelagonian margin and are considered as Dachstein-type platform carbonates. Facies analysis of the Upper Triassic "Lofer-type" lagoonal-peritidal cycles in the Dhidimi area, proved that cycles, although mostly incomplete, were regressive shallowing-upward. The ideal elementary cyclothems are meter-scale in thickness and begin with a subtidal bed (Member C), represented by a peloidal dolostone with megalodonts (wackestone or packstone), being followed by a stromatolitic intertidal dolomitic mudstone and/or fenestral intertidal dolomitic mudstone (Member B) that is overlain by dolocrete (terrestrial stromatolites or pisoidic dolomite) or a supratidal "soil conglomerate" in red micritic matrix (Member A). Lofer-cycle boundaries are defined at the erosional surfaces and accordingly the Lofer cyclothems are unconformity-bounded units. Due to common post-depositional truncation of the subtidal and intertidal facies, the supratidal members prevail, being developed, in places, directly upon subaerial exposure surfaces (erosionally reduced cyclothems). Peritidal layers are characterized by a well-expressed lamination, sheet cracks, tepee structures, fenestral pores and karst dissolution cavities. The studied lagoonal-peritidal cycles are considered to have been deposited in a tidal-flat setting (inner platform), repeatedly exposed under subaerial conditions, in the context of a broader tropical rimmed platform. Although the studied area was tectonically active due to rift-activity and the autocyclic processes should also be taken in consideration, the great lateral correlatability of cycles, the facies shifting and the widespread erosion that resulted in superposition of supratidal-pedogenic facies directly upon subtidal members (subaerial erosional unconformity), indicating a sea-level drop, reflect allocyclic control via high-frequency eustatic sea-level oscillation (orbital forcing). Sediment deposition occurred during low-stand system tract (LST), that probably continued also in the transgressive system tract (TST) and reflects an overall sea-level fall. Under these conditions dissolution and cement precipitation episodes, as well development of paleosols and karsts, were triggered, during a relatively less arid interval.

Zonation and structuring factors of meiofauna communities in a tropical seagrass bed (Gazi Bay, Kenya)

NASA Astrophysics Data System (ADS)

De Troch, Marleen; Gurdebeke, Shirley; Fiers, Frank; Vincx, Magda

2001-02-01

This study deals with the relation between tropical meiofauna and environmental variables by comparing the 'benthic' (i.e. in the bare sediment adjacent to seagrass plants) and the 'epiphytic' (i.e. in samples including seagrass plants) meiofauna associated with five seagrass species from the high intertidal to the high subtidal zone in Gazi Bay (Kenya). Ordination and variance analysis revealed three distinct 'benthic' and two 'epiphytic' meiofauna assemblages. These assemblages corresponded entirely with those identified for the seagrass species: a high intertidal pioneer association ( Halophila ovalis/ Halodule wrightii), an intertidal climax assemblage ( Thalassia hemprichii) and a high subtidal pioneer association ( Halophila stipulacea/ Syringodium isoetifolium). These data support the hypothesis that meiofaunal communities correspond to the characteristic zonation of the seagrass vegetation in Gazi Bay. In beds of the pioneer seagrass species, the close relationship between sediment characteristics and both 'benthic' and 'epiphytic' meiofauna communities suggests that these pioneer communities were mainly driven by physical factors. The 'benthic' communities adjacent to the climax seagrass species T. hemprichii were more structured by biogenic factors, e.g. % TOM, chlorophyll a and c, fucoxanthin, habitat complexity and growth form of the seagrass species. For its associated 'epiphytic' meiofauna the latter conclusion was even more striking. These data corroborate the importance of physical factors in disturbed environments (intertidal zone, near pioneer seagrasses) and of biotic factors in more stable conditions (subtidal zone, near climax seagrasses).

Reoxidation of estuarine sediments during simulated resuspension events: Effects on nutrient and trace metal mobilisation

NASA Astrophysics Data System (ADS)

Vidal-Durà, Andrea; Burke, Ian T.; Stewart, Douglas I.; Mortimer, Robert J. G.

2018-07-01

Estuarine environments are considered to be nutrient buffer systems as they regulate the delivery of nutrients from rivers to the ocean. In the Humber Estuary (UK) seawater and freshwater mixing during tidal cycles leads to the mobilisation of oxic surface sediments (0-1 cm). However, less frequent seasonal events can also mobilise anoxic subsurface (5-10 cm) sediments, which may have further implications for the estuarine geochemistry. A series of batch experiments were carried out on surface and subsurface sediments taken from along the salinity gradient of the Humber Estuary. The aim was to investigate the geochemical processes driving major element (N, Fe, S, and Mn) redox cycling and trace metal behaviour during simulated resuspension events. The magnitude of major nutrient and metal release was significantly greater during the resuspension of outer estuarine sediments rather than from inner estuarine sediments. When comparing resuspension of surface versus subsurface sediment, only the outer estuary experiments showed significant differences in major nutrient behaviour with sediment depth. In general, any ammonium, manganese and trace metals (Cu and Zn) released during the resuspension experiments were rapidly removed from solution as new sorption sites (i.e. Fe/Mn oxyhydroxides) formed. Therefore Humber estuary sediments showed a scavenging capacity for these dissolved species and hence may act as an ultimate sink for these elements. Due to the larger aerial extent of the outer estuary intertidal mudflats in comparison with the inner estuary area, the mobilisation of the outer estuary sediments (more reducing and richer in sulphides and iron) may have a greater impact on the transport and cycling of nutrients and trace metals. Climate change-associated sea level rise combined with an increasing frequency of major storm events in temperate zones, which are more likely to mobilise deeper sediment regions, will impact the nutrient and metal inputs to the coastal waters, and therefore enhance the likelihood of eutrophication in this environment.

An alternative radiometric method for calculating the sedimentation rates: application to an intertidal region (SW of Spain).

PubMed

Ligero, R A; Casas-Ruiz, M; Barrera, M; Barbero, L; Meléndez, M J

2010-09-01

A new method using the inventory determined for the activity of the radionuclide (137)Cs, coming from global radioactive fallout has been utilised to calculate the sedimentation rates. The method has been applied in a wide intertidal region in the Bay of Cádiz Natural Park (SW Spain). The sedimentation rates estimated by the (137)Cs inventory method ranged from 0.26 cm/year to 1.72 cm/year. The average value of the sedimentation rate obtained is 0.59 cm/year, and this rate has been compared with those resulting from the application of the (210)Pb dating technique. A good agreement between the two procedures has been found. From the study carried out, it has been possible for the first time, to draw a map of sedimentation rates for this zone where numerous physico-chemical, oceanographic and ecological studies converge, since it is situated in a region of great environmental interest. This area, which is representative of common environmental coastal scenarios, is particularly sensitive to perturbations related to climate change, and the results of the study will allow to make short and medium term evaluations of this change.

Nitrogen Fixation in the Intertidal Sediments of the Yangtze Estuary: Occurrence and Environmental Implications

NASA Astrophysics Data System (ADS)

Hou, Lijun; Wang, Rong; Yin, Guoyu; Liu, Min; Zheng, Yanling

2018-03-01

Nitrogen fixation is a microbial-mediated process converting atmospheric dinitrogen gas to biologically available ammonia or other molecules, and it plays an important role in regulating nitrogen budgets in coastal marine ecosystems. In this study, nitrogen fixation in the intertidal sediments of the Yangtze Estuary was investigated using nitrogen isotope tracing technique. The abundance of nitrogen fixation functional gene (nifH) was also quantified. The measured rates of sediment nitrogen fixation ranged from 0.37 to 7.91 nmol N g-1 hr-1, while the abundance of nifH gene varied from 2.28 × 106 to 1.28 × 108 copies g-1 in the study area. The benthic nitrogen fixation was correlated closely to the abundance of nifH gene and was affected significantly by salinity, pH, and availability of sediment organic carbon and ammonium. It is estimated that sediment nitrogen fixation contributed approximately 9.3% of the total terrigenous inorganic nitrogen transported annually into the Yangtze estuarine and coastal environment. This result implies that the occurrence of benthic nitrogen fixation acts as an important internal source of reactive nitrogen and to some extent exacerbates nitrogen pollution in this aquatic ecosystem.

Annual and seasonal temperature variance along an inter-tidal sediment transect in Yaquina bay, Oregon, 1999 - 2006

EPA Science Inventory

Sediment temperature was measured using submersible Onset TidbiT® recording thermistor thermometers at eelgrass (Zostera marina, Z. japonica) mid-rhizome root depth (~5 cm) at 6 stations on a transect from ~MLLW (mean lower low water) at the channel edge to near MHHW (mean higher...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfe, D.A.

Three separate papers are represented in this final report; Toxicity of intertidal and subtidal sediments contaminated by the Exxon Valdez oil spill; Comparative toxicities of polar and non-polar organic fractions from sediments affected by the Exxon Valdez oil spill in Prince William Sound, Alaska; and Fate of the oil spilled from the T/V Exxon Valdez in Prince William Sound, Alaska.

Monitoring toxicity of polycyclic aromatic hydrocarbons in intertidal sediments for five years after the Hebei Spirit oil spill in Taean, Republic of Korea.

PubMed

Lee, Chang-Hoon; Lee, Jong-Hyeon; Sung, Chan-Gyoung; Moon, Seong-Dae; Kang, Sin-Kil; Lee, Ji-Hye; Yim, Un Hyuk; Shim, Won Joon; Ha, Sung Yong

2013-11-15

Ecotoxicological monitoring of intertidal sediments was performed for 5 years after the Hebei Spirit oil spill in Taean, Korea. Sediment toxicity was observed on most of the beaches 4 months after the spill and later decreased rapidly to nontoxic levels 8 months after the spill. The concentrations of total polycyclic aromatic hydrocarbons (TPAHs) in the sediments ranged from 2 to 530,000 ng/g during the monitoring. More than half of the samples exhibited significant toxicity 5 years after the Hebei Spirit oil spill. Using a logistic regression model, the median lethal concentration of TPAHs to amphipod Monocorophium uenoi was estimated to be 36,000 ng/g. From the 63 chemistry and toxicity data, the effect range-low, effect range median, threshold effect level, and probable effect level were derived to be 3190, 54,100, 2480, and 29,000 ng/g, respectively. The relative compositions of the PAH groups indicated that the weathering process is still ongoing. Copyright © 2013 Elsevier Ltd. All rights reserved.

Occurrence and behavior of butyltins in intertidal and shallow subtidal surface sediments of an estuarine beach under different sampling conditions

NASA Astrophysics Data System (ADS)

Santos, Dayana Moscardi dos; Sant'Anna, Bruno Sampaio; Sandron, Daniela Corsino; Cardoso de Souza, Sara; Cristale, Joyce; Marchi, Mary Rosa Rodrigues de; Turra, Alexander

2010-07-01

Contamination by butyltin compounds (BTs) has been reported in estuarine environments worldwide, with serious impacts on the biota of these areas. Considering that BTs can be degraded by varying environmental conditions such as incident light and salinity, the short-term variations in such factors may lead to inaccurate estimates of BTs concentrations in nature. Therefore, the present study aimed to evaluate the possibility that measurements of BTs in estuarine sediments are influenced by different sampling conditions, including period of the day (day or night), tidal zone (intertidal or subtidal), and tides (high or low). The study area is located on the Brazilian southeastern coast, São Vicente Estuary, at Pescadores Beach, where BT contamination was previously detected. Three replicate samples of surface sediment were collected randomly in each combination of period of the day, tidal zone, and tide condition, from three subareas along the beach, totaling 72 samples. BTs were analyzed by GC-PFPD using a tin filter and a VF-5 column, by means of a validated method. The concentrations of tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) ranged from undetectable to 161 ng Sn g -1 (d.w.). In most samples (71%), only MBT was quantifiable, whereas TBTs were measured in only 14, suggesting either an old contamination or rapid degradation processes. DBT was found in 27 samples, but could be quantified in only one. MBT concentrations did not differ significantly with time of day, zones, or tide conditions. DBT and TBT could not be compared under all these environmental conditions, because only a few samples were above the quantification limit. Pooled samples of TBT did not reveal any difference between day and night. These results indicated that, in assessing contamination by butyltin compounds, surface-sediment samples can be collected in any environmental conditions. However, the wide variation of BTs concentrations in the study area, i.e., over a very small geographic scale, illustrates the need for representative hierarchical and composite sampling designs that are compatible with the multiscalar temporal and spatial variability common to most marine systems. The use of such sampling designs will be necessary for future attempts to quantitatively evaluate and monitor the occurrence and impact of these compounds in nature.

Flocculation and sediment deposition in a hypertidal creek

NASA Astrophysics Data System (ADS)

O'Laughlin, C.; van Proosdij, D.; Milligan, T. G.

2014-07-01

In the hypertidal Bay of Fundy, environmental impacts in response to commercial-scale tidal power development remain to be fully understood. The extraction of tidal energy may impact sediment dynamics in far-field environments, such as the intertidal zone, through potential alterations to tidal amplitude in the Minas Basin. Tidal conditions (e.g. current velocity, turbulence, suspended sediment concentration) were monitored in a sheltered salt marsh creek over 18 tidal cycles in various stages of the spring-neap cycle. Samples of deposited and suspended sediments were collected and analyzed for grain size using a Beckman Coulter Multisizer III. Results suggest that the flocculated component of both deposited and suspended sediment is consistently high over a wide range of tidal conditions. A routinely high incoming concentration of highly-flocculated material results in large amounts of sediment deposition in tidal creeks in response to individual tidal cycles. Resuspension and removal of newly deposited material is shown to vary with over-marsh, bankfull and channel-restricted tides. Disruption of the tidal regime due to a reduction in Minas Basin tidal amplitude may lessen the cumulative export capacity of tidal channels over time, potentially leading to gradual infilling of tidal creeks. The long-term effects of tidal power development on intertidal areas are generally unknown.

Determination of gamma-emitting radionuclides in the inter-tidal sediments off Balochistan (Pakistan) Coast, Arabian Sea.

PubMed

Akram, M; Qureshi, Riffat M; Ahmad, Nasir; Solaija, Tariq Jamal

2007-01-01

Natural radionuclide contents of 226Ra, 228Ra and (40)K were studied for inter-tidal sediments collected from selected locations off the745 km long Balochistan Coast using HPGe detector based gamma-spectrometry system. The sampling zone extends from the beaches of Sonmiani (near Karachi metropolis) through Jiwani (close to the border of Iran). The natural radioactivity levels detected in various sediment samples range from 14.4 +/- 2.5 to 36.6 +/- 3.8 Bq kg(-1) for 226Ra, 9.8 +/- 1.2 to 35.2 +/- 2.0 Bq kg(-1) for (228)Ra and 144.6 +/- 9.4 to 610.5 +/- 23.9 Bq kg(-1) for (40)K. No artificial radionuclide was detected in any of the marine coastal sediment samples. 137Cs, (60)Co, 106Ru and 144Ce contents in sediment samples were below the limit of detection. The measured radioactivity levels are compared with those reported in the literature for coastal sediments in other parts of the world. The information presented in this paper will serve as the first ever local radioactivity database for the Balochistan/Makran Coastal belt of Pakistan. The presented data will also contribute to the IAEA's, Asia-Pacific Marine Radioactivity Database (ASPAMARD) and the Global Marine Radioactivity Database (GLOMARD).

Characterisation of physical environmental factors on an intertidal sandflat, Manukau Harbour, New Zealand

USGS Publications Warehouse

Bell, R.G.; Hume, T.M.; Dolphin, T.J.; Green, M.O.; Walters, R.A.

1997-01-01

Physical environmental factors, including sediment characteristics, inundation time, tidal currents and wind waves, likely to influence the structure of the benthic community at meso-scales (1-100 m) were characterised for a sandflat off Wiroa Island (Manukau Harbour, New Zealand). In a 500 x 250 m study site, sediment characteristics and bed topography were mostly homogenous apart from patches of low-relief ridges and runnels. Field measurements and hydrodynamic modelling portray a complex picture of sediment or particulate transport on the intertidal flat, involving interactions between the larger scale tidal processes and the smaller scale wave dynamics (1-4 s; 1-15 m). Peak tidal currents in isolation are incapable of eroding bottom sediments, but in combination with near-bed orbital currents generated by only very small wind waves, sediment transport can be initiated. Work done on the bed integrated over an entire tidal cycle by prevailing wind waves is greatest on the elevated and flatter slopes of the study site, where waves shoal over a wider surf zone and water depths remain shallow e enough for wave-orbital currents to disturb the bed. The study also provided physical descriptors quantifying static and hydrodynamic (tidal and wave) factors which were used in companion studies on ecological spatial modelling of bivalve distributions and micro-scale sediment reworking and transport.

Herbicide contamination and the potential impact to seagrass meadows in Hervey Bay, Queensland, Australia.

PubMed

McMahon, Kathryn; Bengtson Nash, Susan; Eaglesham, Geoff; Müller, Jochen F; Duke, Norman C; Winderlich, Steve

2005-01-01

Low concentrations of herbicides (up to 70 ng l(-1)), chiefly diuron (up to 50 ng l(-1)) were detected in surface waters associated with inter-tidal seagrass meadows of Zostera muelleri in Hervey Bay, south-east Queensland, Australia. Diuron and atrazine (up to 1.1 ng g(-1) dry weight of sediment) were detected in the sediments of these seagrass meadows. Concentration of the herbicides diuron, simazine and atrazine increased in surface waters associated with seagrass meadows during moderate river flow events indicating herbicides were washed from the catchment to the marine environment. Maximum herbicide concentration (sum of eight herbicides) in the Mary River during a moderate river flow event was 4260 ng l(-1). No photosynthetic stress was detected in seagrass in this study during low river flow. However, with moderate river flow events, nearshore seagrasses are at risk of being exposed to concentrations of herbicides that are known to inhibit photosynthesis.

Climate change and intertidal wetlands.

PubMed

Ross, Pauline M; Adam, Paul

2013-03-19

Intertidal wetlands are recognised for the provision of a range of valued ecosystem services. The two major categories of intertidal wetlands discussed in this contribution are saltmarshes and mangrove forests. Intertidal wetlands are under threat from a range of anthropogenic causes, some site-specific, others acting globally. Globally acting factors include climate change and its driving cause-the increasing atmospheric concentrations of greenhouse gases. One direct consequence of climate change will be global sea level rise due to thermal expansion of the oceans, and, in the longer term, the melting of ice caps and glaciers. The relative sea level rise experienced at any one locality will be affected by a range of factors, as will the response of intertidal wetlands to the change in sea level. If relative sea level is rising and sedimentation within intertidal wetlands does not keep pace, then there will be loss of intertidal wetlands from the seaward edge, with survival of the ecosystems only possible if they can retreat inland. When retreat is not possible, the wetland area will decline in response to the "squeeze" experienced. Any changes to intertidal wetland vegetation, as a consequence of climate change, will have flow on effects to biota, while changes to biota will affect intertidal vegetation. Wetland biota may respond to climate change by shifting in distribution and abundance landward, evolving or becoming extinct. In addition, impacts from ocean acidification and warming are predicted to affect the fertilisation, larval development, growth and survival of intertidal wetland biota including macroinvertebrates, such as molluscs and crabs, and vertebrates such as fish and potentially birds. The capacity of organisms to move and adapt will depend on their life history characteristics, phenotypic plasticity, genetic variability, inheritability of adaptive characteristics, and the predicted rates of environmental change.

Climate Change and Intertidal Wetlands

PubMed Central

Ross, Pauline M.; Adam, Paul

2013-01-01

Intertidal wetlands are recognised for the provision of a range of valued ecosystem services. The two major categories of intertidal wetlands discussed in this contribution are saltmarshes and mangrove forests. Intertidal wetlands are under threat from a range of anthropogenic causes, some site-specific, others acting globally. Globally acting factors include climate change and its driving cause—the increasing atmospheric concentrations of greenhouse gases. One direct consequence of climate change will be global sea level rise due to thermal expansion of the oceans, and, in the longer term, the melting of ice caps and glaciers. The relative sea level rise experienced at any one locality will be affected by a range of factors, as will the response of intertidal wetlands to the change in sea level. If relative sea level is rising and sedimentation within intertidal wetlands does not keep pace, then there will be loss of intertidal wetlands from the seaward edge, with survival of the ecosystems only possible if they can retreat inland. When retreat is not possible, the wetland area will decline in response to the “squeeze” experienced. Any changes to intertidal wetland vegetation, as a consequence of climate change, will have flow on effects to biota, while changes to biota will affect intertidal vegetation. Wetland biota may respond to climate change by shifting in distribution and abundance landward, evolving or becoming extinct. In addition, impacts from ocean acidification and warming are predicted to affect the fertilisation, larval development, growth and survival of intertidal wetland biota including macroinvertebrates, such as molluscs and crabs, and vertebrates such as fish and potentially birds. The capacity of organisms to move and adapt will depend on their life history characteristics, phenotypic plasticity, genetic variability, inheritability of adaptive characteristics, and the predicted rates of environmental change. PMID:24832670

Variability of intertidal foraminferal assemblages in a salt marsh, Oregon, USA

USGS Publications Warehouse

Milker, Yvonne; Horton, Benjamin P.; Nelson, Alan R.; Engelhart, Simon E.; Witter, Robert C.

2015-01-01

We studied 18 sampling stations along a transect to investigate the similarity between live (rose Bengal stained) foraminiferal populations and dead assemblages, their small-scale spatial variations and the distribution of infaunal foraminifera in a salt marsh (Toms Creek marsh) at the upper end of the South Slough arm of the Coos Bay estuary, Oregon, USA. We aimed to test to what extent taphonomic processes, small-scale variability and infaunal distribution influence the accuracy of sea-level reconstructions based on intertidal foraminifera. Cluster analyses have shown that dead assemblages occur in distinct zones with respect to elevation, a prerequisite for using foraminifera as sea-level indicators. Our nonparametric multivariate analysis of variance showed that small-scale spatial variability has only a small influence on live (rose Bengal stained) populations and dead assemblages. The dissimilarity was higher, however, between live (rose Bengal stained) populations in the middle marsh. We observed early diagenetic dissolution of calcareous tests in the dead assemblages. If comparable post-depositional processes and similar minor spatial variability also characterize fossil assemblages, then dead assemblage are the best modern analogs for paleoenvironmental reconstructions. The Toms Creek tidal flat and low marsh vascular plant zones are dominated by Miliammina fusca, the middle marsh is dominated by Balticammina pseudomacrescens and Trochammina inflata, and the high marsh and upland–marsh transition zone are dominated by Trochamminita irregularis. Analysis of infaunal foraminifera showed that most living specimens are found in the surface sediments and the majority of live (rose Bengal stained) infaunal specimens are restricted to the upper 10 cm, but living individuals are found to depths of 50 cm. The dominant infaunal specimens are similar to those in the corresponding surface samples and no species have been found living solely infaunally. The total numbers of infaunal foraminifera are small compared to the total numbers of dead specimens in the surface samples. This suggests that surface samples adequately represent the modern intertidal environment in Toms Creek.

Effects of vegetation and fecal pellets on the erodibility of cohesive sediments: Ganghwa tidal flat, west coast of Korea.

PubMed

Ha, Ho Kyung; Ha, Hun Jun; Seo, Jun Young; Choi, Sun Min

2018-06-04

Although the Korean tidal flats in the Yellow Sea have been highlighted as a typical macrotidal system, so far, there have been no measurements of the sediment erodibility and critical shear stress for erosion (τ ce ). Using the Gust erosion microcosm system, a series of field experiments has been conducted in the Ganghwa tidal flat to investigate quantitatively the effects of biogenic materials on the erodibility of intertidal cohesive sediments. Four representative sediment cores with different surficial conditions were analyzed to estimate the τ ce and eroded mass. Results show that τ ce of the "free" sediment bed not covered by any biogenic material on the Ganghwa tidal flat was in the range of 0.1-0.2 Pa, whereas the sediment bed partially covered by vegetation (Phragmites communis) or fecal pellets had enhanced τ ce up to 0.45-0.6 Pa. The physical presence of vegetation or fecal pellets contributed to protection of the sediment bed by blocking the turbulent energy. An inverse relationship between the organic matter included in the eroded mass and the applied shear stress was observed. This suggests that the organic matter enriched in a near-bed fluff layer is highly erodible, and the organic matter within the underlying sediment layer becomes depleted and less erodible with depth. Our study underlines the role of biogenic material in stabilizing the benthic sediment bed in the intertidal zone. Copyright © 2018 Elsevier Ltd. All rights reserved.

Estimating areal production of intertidal microphytobenthos based on spatio-temporal community dynamics and laboratory measurements

NASA Astrophysics Data System (ADS)

Du, Guo Ying; Chung, Ik Kyo

2009-12-01

In situ Microphytobenthic community dynamics were combined with laboratory measurement of predominant species by fluorescence methods to estimate the areal primary production. Field investigation of community dynamics of microphytobenthos (MPB) was conducted from August 2006 to August 2007 in intertidal flats of the Nakdong River estuary, Korea. MPB Biomass varied between 0.47 and 16.58 μg cm-3 in the surface 1 cm sediment, with two dominant diatom species, Amphora coffeaeformis and Navicula sp., occupying average 77.2 ± 14.9% of total number of MPB cells. The biomass was higher in the slightly muddy sand sites than that in the sand site, and showed different pattern of seasonal variation. The profile of vertical distribution of biomass was an exponential decrease trend with depth in sediments. The biomass proportions in the uppermost 3 mm were 57.6% and 37.8% with and without the presence of biofilm, respectively. The two dominant species were cultured in laboratory, and their photosynthetic parameters, rETRmax (relative maximum electron transport rate), α (light utilization coefficient) and E k (light saturation parameter) were derived from rETR (relative ETR)-irradiance curves by Imaging- PAM (pulse amplitude modulated) fluorometry. The rETR-irradiance curves showed no significant difference of photosynthetic activities between the two species. The areal potential production ranged from 0.74 to 2.22 g C m-2 d-1.

An Examination of Body Temperature for the Rocky Intertidal Mussel species, Mytilus californianus, Using Remotely Sensed Satellite Observations

NASA Astrophysics Data System (ADS)

Price, J.; Liff, H.; Lakshmi, V.

2012-12-01

Temperature is considered to be one of the most important physical factors in determining organismal distribution and physiological performance of species in rocky intertidal ecosystems, especially the growth and survival of mussels. However, little is known about the spatial and temporal patterns of temperature in intertidal ecosystems or how those patterns affect intertidal mussel species because of limitations in data collection. We collected in situ temperature at Strawberry Hill, Oregon USA using mussel loggers embedded among the intertidal mussel species, Mytilus californianus. Remotely sensed surface temperatures were used in conjunction with in situ weather and ocean data to determine if remotely sensed surface temperatures can be used as a predictor for changes in the body temperature of a rocky intertidal mussel species. The data used in this study was collected between January 2003 and December 2010. The mussel logger temperatures were compared to in situ weather data collected from a local weather station, ocean data collected from a NOAA buoy, and remotely sensed surface temperatures collected from NASA's sun-synchronous Moderate Resolution Imaging Spectroradiometer aboard the Earth Observing System Aqua and EOS Terra satellites. Daily surface temperatures were collected from four pixel locations which included two sea surface temperature (SST) locations and two land surface temperature (LST) locations. One of the land pixels was chosen to represent the intertidal surface temperature (IST) because it was located within the intertidal zone. As expected, all surface temperatures collected via satellite were significantly correlated to each other and the associated in situ temperatures. Examination of temperatures from the off-shore NOAA buoy and the weather station provide evidence that remotely sensed temperatures were similar to in situ temperature data and explain more variability in mussel logger temperatures than the in situ temperatures. Our results suggest that temperatures (surface temperature and air temperature) are similar across larger spatial scales even when the type of data collection is different. Mussel logger temperatures were strongly correlated to SSTs and were not significantly different than SSTs. Sea surface temperature collected during the Aqua overpass explained 67.1% of the variation in mean monthly mussel logger temperature. When SST, LST, and IST were taken into consideration, nearly 73% of the variation in mussel logger temperature was explained. While in situ monthly air temperature and water temperature explained only 28-33% of the variation in mussel logger temperature. Our results suggests that remotely sensed surface temperatures are reliable and important measurements that can be used to better understand the effects temperature may have on intertidal mussel species in Strawberry Hill, Oregon. Remotely sensed surface temperature could act as a relative indicator of change and may be used to predict general habitat trends and drivers that could directly affect organism body temperature.

Microplastic fibers in the intertidal ecosystem surrounding Halifax Harbor, Nova Scotia.

PubMed

Mathalon, Alysse; Hill, Paul

2014-04-15

Humans continue to increase the use and disposal of plastics by producing over 240 million tonnes per year, polluting the oceans with persistent waste. The majority of plastic in the oceans are microplastics (<5 mm). In this study, the contamination of microplastic fibers was quantified in sediments from the intertidal zones of one exposed beach and two protected beaches along Nova Scotia's Eastern Shore. From the two protected beaches, polychaete worm fecal casts and live blue mussels (Mytilus edulis) were analyzed for microplastic content. Store-bought mussels from an aquaculture site were also analyzed. The average microplastic abundance observed from 10 g sediment subsamples was between 20 and 80 fibers, with higher concentrations at the high tide line from the exposed beach and at the low tide line from the protected beaches. Microplastic concentrations from polychaete fecal casts resembled concentrations quantified from low tide sediments. In two separate mussel analyses, significantly more microplastics were enumerated in farmed mussels compared to wild ones. Copyright © 2014 Elsevier Ltd. All rights reserved.

Quantitative distribution and functional groups of intertidal macrofaunal assemblages in Fildes Peninsula, King George Island, South Shetland Islands, Southern Ocean.

PubMed

Liu, Xiaoshou; Wang, Lu; Li, Shuai; Huo, Yuanzi; He, Peimin; Zhang, Zhinan

2015-10-15

To evaluate spatial distribution pattern of intertidal macrofauna, quantitative investigation was performed in January to February, 2013 around Fildes Peninsula, King George Island, South Shetland Islands. A total of 34 species were identified, which were dominated by Mollusca, Annelida and Arthropoda. CLUSTER analysis showed that macrofaunal assemblages at sand-bottom sites belonged to one group, which was dominated by Lumbricillus sp. and Kidderia subquadrata. Macrofaunal assemblages at gravel-bottom sites were divided into three groups while Nacella concinna was the dominant species at most sites. The highest values of biomass and Shannon-Wiener diversity index were found in gravel sediment and the highest value of abundance was in sand sediment of eastern coast. In terms of functional group, detritivorous and planktophagous groups had the highest values of abundance and biomass, respectively. Correlation analysis showed that macrofaunal abundance and biomass had significant positive correlations with contents of sediment chlorophyll a, phaeophorbide and organic matter. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of simulated oil exposure on two intertidal macrozoo benthos: Tympanotonus fuscata (L.) and Uca tangeri (Eydoux, 1935) in a tropical estuarine ecosystem.

PubMed

Ewa-Oboho, I O; Abby-Kalio, N J

1994-08-01

The impacts of simulated Nigerian light crude oil on mud flat periwinkles, Tympanotonus fuscata (L.), and fiddler crabs, Uca tangeri (Eydoux, 1935) was examined through field experiments conducted in the Bonny estuary of the Niger Delta (southern Nigeria). The purpose was to assess the fate and effects of a known quantity of the Nigerian light crude oil on this environment. Drastic changes in the densities of T. fuscata and U. tangeri observed immediately after spills was attributed to the effects of the oil. A large increase in Uca biomass occurred in the affected area. Salinity and temperature in the study area showed little fluctuations throughout the survey. Sediment characteristics were similar for all sites (stations). Grain-size analysis revealed that sediments at the study area were 70% silt. Migration of oil via tidal percolation was observed as much as 11 cm beneath the sediment surface.

Processes Controlling Transfer of Fine-Grained Sediment in Tidal Systems Spanning a Range of Fluvial Influence

DTIC Science & Technology

2012-09-30

understand how the delicate balance of ebb and flood sediment fluxes is maintained to create tidal flat and mangrove complexes, and distributary shoals and...and the subaqueous delta on the inner continental shelf, and sediment sinks within vegetated/ mangrove shoreline complexes. Our overall hypothesis...on Mangrove /Vegetated Intertidal Areas. Along the main stem tidal river and in the offshore banks may be shorelines lined with vegetation ( mangroves

Modern diatom assemblages as tools for paleoenvironmental reconstruction: a case study from estuarine intertidal zones in southern Iberia

NASA Astrophysics Data System (ADS)

Gomes, Ana; Boski, Tomasz; Moura, Delminda; Szkornik, Katie; Witkowski, Andrzej; Connor, Simon; Laut, Lazaro; Sobrinho, Frederico; Oliveira, Sónia

2017-04-01

Diatoms are unicellular algae that live in saline, brackish and freshwater environments, either floating in the water column or associated with various substrates (e.g., muddy and sandy sediments). Diatoms are sensitive to changes in environmental variables such as salinity, sediment texture, nutrient availability, light and temperature. This characteristic, along with their short lifespan, allows diatoms to quickly respond to environmental changes. Since the beginning of the 20th century, diatoms have been widely used to study the Holocene evolution of estuaries worldwide, particularly to reconstruct ecological responses to sea-level and climate changes. However, diatoms have been poorly studied in estuarine intertidal zones, due to the complexity of these environments, which have both fluvial and marine influences. The aim of this study was to understand diatom diversity and spatial distribution in intertidal zones from two geomorphologically and hydrologically distinct estuaries. Sediment samples were collected from within the intertidal zones along the Arade and Guadiana River estuaries in southern Iberia. The sampling points embraced almost all the tidal and salinity gradients of both estuaries, capturing the highest possible environmental variability and hence of diatom assemblages. At each sampling point, the salinity and pH of the sediment interstitial water were measured. The sediment samples were subdivided for diatom identification, textural analysis and organic matter determination. All sampling points were georeferenced by DGPS and the duration of tidal inundation was calculated for each site. Following diatom identification, the data were analysed statistically (i.e. cluster analysis, PCA, DCA and RDA). The present study revealed that there is a great diatom diversity in both estuaries (418 species), with several species new to science. The most important diatom species (with abundances higher or equal to 5%) occur in five ecological groups, which are associated to five distinct environments: lower estuary sandflats, lower estuary mudflats, middle to upper estuary mudflats, lower estuary salt marshes and middle estuary salt marshes. This study allowed us to establish modern analogues that are essential for developing transfer functions (quantitative palaeoenvironmental estimates). These methods will enable more accurate Holocene paleoenvironmental reconstructions on the southern Iberian coast and will improve knowledge about the evolution of estuarine environments globally . The work was supported by the SFRH/BD/62405/2009 fellowship, funded by the Portuguese Foundation for Science and Technology.

An Examination of Intertidal Temperatures Through Remotely Sensed Satellite Observations

NASA Astrophysics Data System (ADS)

Lakshmi, V.

2010-12-01

MODIS Aqua and Terra satellites produce both land surface temperatures and sea surface temperatures using calibrated algorithms. In this study, the land surface temperatures were retrieved during clear-sky (non-cloudy) conditions at a 1 km2 resolution (overpass time at 10:30 am) whereas the sea surface temperatures are also retrieved during clear-sky conditions at approximately 4 km resolution (overpass time at 1:30 pm). The purpose of this research was to examine remotely sensed sea surface (SST), intertidal (IST), and land surface temperatures (LST), in conjunction with observed in situ mussel body temperatures, as well as associated weather and tidal data. In Strawberry Hill, Oregon, it was determined that intertidal surface temperatures are similar to but distinctly different from land surface temperatures although influenced by sea surface temperatures. The air temperature and differential heating throughout the day, as well as location in relation to the shore, can greatly influence the remotely sensed surface temperatures. Therefore, remotely sensed satellite data is a very useful tool in examining intertidal temperatures for regional climatic changes over long time periods and may eventually help researchers forecast expected climate changes and help determine associated biological implications.

Impacts of macro - and microplastic on macrozoobenthos abundance in intertidal zone

NASA Astrophysics Data System (ADS)

Bangun, A. P.; Wahyuningsih, H.; Muhtadi, A.

2018-02-01

Plastics pollution in coastal areas is one of the topics that have received more attention over the past few years. The intertidal zone is a waters area that is directly affected by contamination of plastic waste from land and sea. The purpose of this study was to analyze the types and abundance of plastic waste in the intertidal zone and its impact on macrozoobenthos abundance. This research was conducted at Pesisir Desa Jaring Halus in February-April 2017. Macrozoobenthos and macro - micro plastic were collected by using quadratic transect. Sediments were collected with a core, to a depth of 30 cm. Microplastic and macroplastic abundances were analyzed using separation of sediment density and hand sorting. The dominant micro plastic types were film (52.30%), fiber (24.88%), fragments (22.74%), followed by pellets (0.1%). The total number of microplastics were 326,33 items and macro plastic were 308 items. Macroplastic abundance is positively correlated with microplastic (0.765). The abundance of macrozoobenthos is negatively correlated with microplastic abundance (-0.368) and with macro plastic abundance (-0.633). The management strategies were suggested clean up marine debris, decrease plastic using and built up the station of debris processing.

Spatial and temporal variation of intertidal nematodes in the northern Gulf of Mexico after the Deepwater Horizon oil spill.

PubMed

Brannock, Pamela M; Sharma, Jyotsna; Bik, Holly M; Thomas, W Kelley; Halanych, Kenneth M

2017-09-01

Nematodes are an abundant and diverse interstitial component of sedimentary habitats that have been reported to serve as important bioindicators. Though the 2010 Deepwater Horizon (DWH) disaster occurred 60 km offshore in the Gulf of Mexico (GOM) at a depth of 1525 m, oil rose to the surface and washed ashore, subjecting large segments of coastline in the northern GOM to contamination. Previous metabarcoding work shows intertidal nematode communities were negatively affected by the oil spill. Here we examine the subsequent recovery of nematode community structure at five sites along the Alabama coast over a two-year period. The latter part of the study (July 2011-July 2012) also included an examination of nematode vertical distribution in intertidal sediments. Results showed nematode composition within this region was more influenced by sample locality than time and depth. The five sampling sites were characterized by distinct nematode assemblages that varied by sampling dates. Nematode diversity decreased four months after the oil spill but increased after one year, returning to previous levels at all sites except Bayfront Park (BP). There was no significant difference among nematode assemblages in reference to vertical distribution. Although the composition of nematode assemblages changed, the feeding guilds they represented were not significantly different even though some variation was noted. Data from morphological observations integrated with metabarcoding data indicated similar spatial variation in nematode distribution patterns, indicating the potential of using these faster approaches to examine overall disturbance impact trends within communities. Heterogeneity of microhabitats in the intertidal zone indicates that future sampling and fine-scale studies of nematodes are needed to examine such anthropogenic effects. Copyright © 2017 Elsevier Ltd. All rights reserved.

Tidally driven pore water exchange in offshore intertidal sandbanks: Part I. Field measurements

NASA Astrophysics Data System (ADS)

Gibbes, B.; Robinson, C.; Carey, H.; Li, L.; Lockington, D.

2008-08-01

In recent years blooms of the toxic marine cyanobacteria Lyngbya majuscula have been frequently observed in a system of offshore intertidal sandbanks in Moreton Bay, Australia. Past research suggests that these blooms are linked to the presence of bio-available forms of iron. Using hydraulic and pore water chemistry data collected from a shore normal transect at an offshore bloom site, the role of tidally driven exchange as a potential mechanism for delivery of bio-available iron across the sediment-water interface was examined. Field data revealed a residual pore water flow system in the sandbank, with seawater entering the upper sandbank platform and discharging through the bank edge. Upward flow and elevated near-surface dissolved Fe(II) concentrations (>20 μM Fe(II) at -0.05 m depth) were measured simultaneously in the discharge zones at the sandbank edge. The measured concentrations were more than four times greater than concentrations previously shown to stimulate L. majuscula growth. These results suggest that the tidally driven exchange mechanism might be capable of delivering dissolved Fe(II) to sites within offshore intertidal sandbanks where blooms of L. majuscula have been observed. While the source of the iron was not identified, potential candidates are discussed. These findings have implications for the current conceptual model for L. majuscula blooms in offshore intertidal sandbanks within Moreton Bay. Further investigations are required to fully understand the role of tidally driven exchange in controlling the export of bio-available iron to coastal waters at the field site. In particular there is a need to better assess the link between the pore water flows and the geochemical reactions that might occur along the flow path.

Spatial-temporal evolution of the eastern Nanhui mudflat in the Changjiang (Yangtze River) Estuary under intensified human activities

NASA Astrophysics Data System (ADS)

Zhang, Xiaodong; Zhang, Yexin; Zhu, Longhai; Chi, Wanqing; Yang, Zuosheng; Wang, Biying; Lv, Kai; Wang, Hongmin; Lu, Zhiyong

2018-05-01

The eastern Nanhui mudflat (ENM), located in the southern flank of the Changjiang (Yangtze River) Estuary, plays a key role in storm protection, defense against sea level rise, and land resource provision for Shanghai, China's largest city. Recently, there has been a great deal of concern for its evolutionary fate, since a drastic reduction in the Changjiang sediment discharge rate and an increased number of estuarine enclosures might negatively impact the environmental protection functions that this mudflat provides. In this paper, a novel method, which employed the envelope lines of instantaneous shoreline positions identified in 436 Landsat satellite images from 1975 to 2016, was used to demonstrate the evolution of the mudflat high and low tide lines in a detailed, quantitative way. Our study reveals the southeast progradation rate of the mudflat doubled from 24 m/yr in 713-1974 CE to 49 m/yr in 1975-1995 CE, probably due to the influence of the estuarine turbidity maximum zone shifting to the ENM. Under the ample sediment input directly from the turbidity maximum zone, the spatial evolution of the ENM was governed predominantly by the changing morphology of the South Passage due to the quick progradation of the ENM, which narrowed the South Passage by pushing the South Passage Trumpet southeastward. Therefore, the ENM experienced rapid accretion during 1975-2016. The accretion rate of the high tide line increased 2-13 times due to vegetation and intertidal enclosures, resulting in the rapid reduction of the intertidal area. The area decreased from 97 km2 in 1976 to 66 km2 in 1995, mainly due to vegetation, and continued decreasing to 12 km2 in 2006 due to the intertidal enclosures. In contrast, the accretion rate of the low tide line increased by 25 times due to subtidal enclosures and caused the intertidal area increased to 78 km2 in 2015. The almost disappeared intertidal zones in 2006 reappeared. However, this reappearance might be a temporary transitional state, and once the subtidal enclosures are completed, most of the intertidal zones will be replaced by enclosure land. Our study reveals that the drastic reduction in the Changjiang sediment flow to the sea has not caused a decline in the ENM. In contrast, the ENM has experienced rapid accretion in the past 40 years, resulting in the strengthening of its functional abilities to protect Shanghai, an unexpected outcome.

Non-Linear Interactions Determine the Impact of Sea-Level Rise on Estuarine Benthic Biodiversity and Ecosystem Processes

PubMed Central

Yamanaka, Tsuyuko; Raffaelli, David; White, Piran C. L.

2013-01-01

Sea-level rise induced by climate change may have significant impacts on the ecosystem functions and ecosystem services provided by intertidal sediment ecosystems. Accelerated sea-level rise is expected to lead to steeper beach slopes, coarser particle sizes and increased wave exposure, with consequent impacts on intertidal ecosystems. We examined the relationships between abundance, biomass, and community metabolism of benthic fauna with beach slope, particle size and exposure, using samples across a range of conditions from three different locations in the UK, to determine the significance of sediment particle size beach slope and wave exposure in affecting benthic fauna and ecosystem function in different ecological contexts. Our results show that abundance, biomass and oxygen consumption of intertidal macrofauna and meiofauna are affected significantly by interactions among sediment particle size, beach slope and wave exposure. For macrofauna on less sloping beaches, the effect of these physical constraints is mediated by the local context, although for meiofauna and for macrofauna on intermediate and steeper beaches, the effects of physical constraints dominate. Steeper beach slopes, coarser particle sizes and increased wave exposure generally result in decreases in abundance, biomass and oxygen consumption, but these relationships are complex and non-linear. Sea-level rise is likely to lead to changes in ecosystem structure with generally negative impacts on ecosystem functions and ecosystem services. However, the impacts of sea-level rise will also be affected by local ecological context, especially for less sloping beaches. PMID:23861863

Non-linear interactions determine the impact of sea-level rise on estuarine benthic biodiversity and ecosystem processes.

PubMed

Yamanaka, Tsuyuko; Raffaelli, David; White, Piran C L

2013-01-01

Sea-level rise induced by climate change may have significant impacts on the ecosystem functions and ecosystem services provided by intertidal sediment ecosystems. Accelerated sea-level rise is expected to lead to steeper beach slopes, coarser particle sizes and increased wave exposure, with consequent impacts on intertidal ecosystems. We examined the relationships between abundance, biomass, and community metabolism of benthic fauna with beach slope, particle size and exposure, using samples across a range of conditions from three different locations in the UK, to determine the significance of sediment particle size beach slope and wave exposure in affecting benthic fauna and ecosystem function in different ecological contexts. Our results show that abundance, biomass and oxygen consumption of intertidal macrofauna and meiofauna are affected significantly by interactions among sediment particle size, beach slope and wave exposure. For macrofauna on less sloping beaches, the effect of these physical constraints is mediated by the local context, although for meiofauna and for macrofauna on intermediate and steeper beaches, the effects of physical constraints dominate. Steeper beach slopes, coarser particle sizes and increased wave exposure generally result in decreases in abundance, biomass and oxygen consumption, but these relationships are complex and non-linear. Sea-level rise is likely to lead to changes in ecosystem structure with generally negative impacts on ecosystem functions and ecosystem services. However, the impacts of sea-level rise will also be affected by local ecological context, especially for less sloping beaches.

Stable Carbon Isotope Fractionation during Bacterial Acetylene Fermentation: Potential for Life Detection in Hydrocarbon-Rich Volatiles of Icy Planet(oid)s.

PubMed

Miller, Laurence G; Baesman, Shaun M; Oremland, Ronald S

2015-11-01

We report the first study of stable carbon isotope fractionation during microbial fermentation of acetylene (C2H2) in sediments, sediment enrichments, and bacterial cultures. Kinetic isotope effects (KIEs) averaged 3.7 ± 0.5‰ for slurries prepared with sediment collected at an intertidal mudflat in San Francisco Bay and 2.7 ± 0.2‰ for a pure culture of Pelobacter sp. isolated from these sediments. A similar KIE of 1.8 ± 0.7‰ was obtained for methanogenic enrichments derived from sediment collected at freshwater Searsville Lake, California. However, C2H2 uptake by a highly enriched mixed culture (strain SV7) obtained from Searsville Lake sediments resulted in a larger KIE of 9.0 ± 0.7‰. These are modest KIEs when compared with fractionation observed during oxidation of C1 compounds such as methane and methyl halides but are comparable to results obtained with other C2 compounds. These observations may be useful in distinguishing biologically active processes operating at distant locales in the Solar System where C2H2 is present. These locales include the surface of Saturn's largest moon Titan and the vaporous water- and hydrocarbon-rich jets emanating from Enceladus. Acetylene-Fermentation-Isotope fractionation-Enceladus-Life detection.

Sedimentary Facies Mapping Based on Tidal Channel Network and Topographic Features

NASA Astrophysics Data System (ADS)

Ryu, J. H.; Lee, Y. K.; Kim, K.; Kim, B.

2015-12-01

Tidal flats on the west coast of Korea suffer intensive changes in their surface sedimentary facies as a result of the influence of natural and artificial changes. Spatial relationships between surface sedimentary facies distribution and benthic environments were estimated for the open-type Ganghwa tidal flat and semi closed-type Hwangdo tidal flat, Korea. In this study, we standardized the surface sedimentary facies and tidal channel index of the channel density, distance, thickness and order. To extract tidal channel information, we used remotely sensed data, such as those from the Korea Multi-Purpose Satellite (KOMPSAT)-2, KOMPSAT-3, and aerial photographs. Surface sedimentary facies maps were generated based on field data using an interpolation method.The tidal channels in each sediment facies had relatively constant meandering patterns, but the density and complexity were distinguishable. The second fractal dimension was 1.7-1.8 in the mud flat, about 1.4 in the mixed flat, and about 1.3 in the sand flat. The channel density was 0.03-0.06 m/m2 in the mud flat and less than 0.02 m/m2 in the mixed and sand flat areas of the two test areas. Low values of the tidal channel index, which indicated a simple pattern of tidal channel distribution, were identified at areas having low elevation and coarse-grained sediments. By contrast, high values of the tidal channel index, which indicated a dendritic pattern of tidal channel distribution, were identified at areas having high elevation and fine-grained sediments. Surface sediment classification based on remotely sensed data must circumspectly consider an effective critical grain size, water content, local topography, and intertidal structures.

Intertidal nematode communities in the Mekong estuaries of Vietnam and their potential for biomonitoring.

PubMed

Quang, Ngo Xuan; Chau, Nguyen Ngoc; Smol, Nic; Prozorova, Larisa; Vanreusel, Ann

2016-02-01

Nematode communities in eight Mekong estuaries were investigated during the dry season. The aim of the study was to identify the structure and the diversity of the communities in relation to the main environmental characteristics. In each estuary, three to four intertidal sampling stations were identified at regular distances from the mouth to up to 45 km land inward. The nematode communities showed a strong correlation with sediment composition and to a lesser degree with chlorophyll a concentrations. Multivariate analysis resulted in the identification of four types of communities. We identified two types of Desmodora communities in the sandy mouth stations and two types of Parodontophora communities in the silty sand stations. One of the silt associated communities showed a preference for higher chlorophyll a concentrations, resulting in higher densities and higher diversity, mainly of monhysterid species. Because of the strong association between community structure and sediment composition, nematodes are a meaningful tool for monitoring changes in their environment. In case their community deviates from what is expected based on sediment, it may serve as an early warning for disturbance.

Impact of intertidal area characteristics on estuarine tidal hydrodynamics: A modelling study for the Scheldt Estuary

NASA Astrophysics Data System (ADS)

Stark, J.; Smolders, S.; Meire, P.; Temmerman, S.

2017-11-01

Marsh restoration projects are nowadays being implemented as ecosystem-based strategies to reduce flood risks and to restore intertidal habitat along estuaries. Changes in estuarine tidal hydrodynamics are expected along with such intertidal area changes. A validated hydrodynamic model of the Scheldt Estuary is used to gain fundamental insights in the role of intertidal area characteristics on tidal hydrodynamics and tidal asymmetry in particular through several geomorphological scenarios in which intertidal area elevation and location along the estuary is varied. Model results indicate that the location of intertidal areas and their storage volume relative to the local tidal prism determine the intensity and reach along the estuary over which tidal hydrodynamics are affected. Our model results also suggest that intertidal storage areas that are located within the main estuarine channel system, and hence are part of the flow-carrying part of the estuary, may affect tidal hydrodynamics differently than intertidal areas that are side-basins of the main estuarine channel, and hence only contribute little to the flow-carrying cross-section of the estuary. If tidal flats contribute to the channel cross-section and exert frictional effects on the tidal propagation, the elevation of intertidal flats influences the magnitude and direction of tidal asymmetry along estuarine channels. Ebb-dominance is most strongly enhanced if tidal flats are around mean sea level or slightly above. Conversely, flood-dominance is enhanced if the tidal flats are situated low in the tidal frame. For intertidal storage areas at specific locations besides the main channel, flood-dominance in the estuary channel peaks in the vicinity of those areas and generally reduces upstream and downstream compared to a reference scenario. Finally, the model results indicate an along-estuary varying impact on the tidal prism as a result of adding intertidal storage at a specific location. In addition to known effects of tidal prism decrease upstream and tidal prism increase downstream of additional storage areas, our model results indicate a reduction in tidal prism far downstream of intertidal storage areas as a result of a decreasing tidal range. This study may assist estuarine managers in assessing the impact of marsh restoration and managed shoreline realignment projects, as well as with the morphological management of estuaries through dredging and disposal of sediment on intertidal areas.

Composition and depth distribution of hydrocarbons in Barataria Bay marsh sediments after the Deepwater Horizon oil spill.

PubMed

Dincer Kırman, Zeynep; Sericano, José L; Wade, Terry L; Bianchi, Thomas S; Marcantonio, Franco; Kolker, Alexander S

2016-07-01

In 2010, an estimate 4.1 million barrels of oil were accidentally released into the Gulf of Mexico (GoM) during the Deepwater Horizon (DWH) Oil Spill. One and a half years after this incident, a set of subtidal and intertidal marsh sediment cores were collected from five stations in Barataria Bay, Louisiana, USA, and analyzed to determine the spatial and vertical distributions and source of hydrocarbon residues based on their chemical composition. An archived core, collected before the DWH oil spill from the same area, was also analyzed to assess the pre-spill hydrocarbon distribution in the area. Analyses of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs) and stable carbon isotope showed that the distribution of petroleum hydrocarbons in Barataria Bay was patchy and limited in areal extent. Significant TPH and ΣPAH concentrations (77,399 μg/g and 219,065 ng/g, respectively) were detected in the surface sediments of one core (i.e., core A) to a depth of 9 cm. Based on a sedimentation rate of 0.39 cm yr(-1), determined using (137)Cs, the presence of anthropogenic hydrocarbons in these sediment core deposited ca. 50 to 60 years ago. The historical background hydrocarbon concentrations increased significantly at the sediment surface and can be attributed to recent inputs. Although the oil present in the bay's sediments has undergone moderate weathering, biomarker analyses performed on core A samples likely indicated the presence of hydrocarbons from the DWH oil spill. The effects of oiling events on Barataria Bay and other marsh ecosystems in this region remain uncertain, as oil undergoes weathering changes over time. Copyright © 2016 Elsevier Ltd. All rights reserved.

Long-term effects of the 'Exxon Valdez' oil spill: Sea otter foraging in the intertidal as a pathway of exposure to lingering oil

USGS Publications Warehouse

Bodkin, James L.; Ballachey, Brenda E.; Coletti, Heather A.; Esslinger, George G.; Kloecker, Kimberly A.; Rice, Stanley D.; Reed, John; Monson, Daniel H.

2012-01-01

The protracted recovery of some bird and mammal populations in western Prince William Sound (WPWS), Alaska, and the persistence of spilled 'Exxon Valdez' oil in intertidal sediments, suggests a pathway of exposure to consumers that occupy nearshore habitats. To evaluate the hypothesis that sea otter (Enhydra lutris) foraging allows access to lingering oil, we contrast spatial relations between foraging behavior and documented oil distribution. We recovered archival time-depth recorders implanted in 19 sea otters in WPWS, where lingering oil and delayed ecosystem recovery are well documented. Sea otter foraging dives ranged from +2.7 to -92 m below sea level (MLLW), with intertidal accounting for 5 to 38% of all foraging. On average, female sea otters made 16050 intertidal dives per year and 18% of these dives were at depths above the +0.80 m tidal elevation. Males made 4100 intertidal dives per year and 26% of intertidal foraging took place at depths above the +0.80 m tidal elevation. Estimated annual oil encounter rates ranged from 2 to 24 times yr-1 for females, and 2 to 4 times yr-1 for males. Exposure rates increased in spring when intertidal foraging doubled and females were with small pups. In summer 2008, we found sea otter foraging pits on 13.5 of 24.8 km of intertidal shoreline surveyed. Most pits (82%) were within 0.5 m of the zero tidal elevation and 15% were above 0.5 m, the level above which most (65%) lingering oil remains. In August 2008, we detected oil above background concentrations in 18 of 41 (44%) pits excavated by sea otters on beaches with prior evidence of oiling, with total PAH concentrations up to 56000 ng g−1 dry weight. Our estimates of intertidal foraging, the widespread presence of foraging pits in the intertidal, and the presence of oil in and near sea otter foraging pits documents a pathway of exposure from lingering intertidal oil to sea otters foraging in WPWS.

Carbon and nitrogen dynamics of the intertidal seagrass, Zostera japonica, on the southern coast of the Korean peninsula

NASA Astrophysics Data System (ADS)

Kim, Jong-Hyeob; Kim, Seung Hyeon; Kim, Young Kyun; Lee, Kun-Seop

2016-12-01

Seagrasses require a large amount of nutrient assimilation to support high levels of production, and thus nutrient limitation for growth often occurs in seagrass habitats. Seagrasses can take up nutrients from both the water column and sediments. However, since seagrasses inhabiting in the intertidal zones are exposed to the air during low tide, the intertidal species may exhibit significantly different carbon (C) and nitrogen (N) dynamics compared to the subtidal species. To examine C and N dynamics of the intertidal seagrass, Zostera japonica, C and N content and stable isotope ratios of above- and below-ground tissues were measured monthly at the three intertidal zones in Koje Bay on the southern coast of Korea. The C and N content and stable isotope (δ13C and δ15N) ratios of seagrass tissues exhibited significant seasonal variations. Both leaf and rhizome C content were not significantly correlated with productivity. Leaf δ13C values usually exhibited negative correlations with leaf productivity. These results of tissue C content and δ13C values suggest that photosynthesis of Z. japonica in the study site was not limited by inorganic C supply, and sufficient inorganic C was provided from the atmosphere. The tissue N content usually exhibited negative correlations with leaf productivity except at the upper intertidal zone, suggesting that Z. japonica growth was probably limited by N availability during high growing season. In the upper intertidal zone, no correlations between leaf productivity and tissue elemental content and stable isotope ratios were observed due to the severely suppressed growth caused by strong desiccation stress.

Persistent Reductions in the Bioavailability of PCBs at a Tidally Inundated Phragmites australis Marsh Amended with Activated Carbon.

PubMed

Sanders, James P; Andrade, Natasha A; Menzie, Charles A; Amos, C Bennett; Gilmour, Cynthia C; Henry, Elizabeth A; Brown, Steven S; Ghosh, Upal

2018-06-05

In situ amendment of sediments with highly sorbent materials like activated carbon (AC) is an increasingly viable strategy to reduce the bioavailability of persistent, sediment-associated contaminants to benthic communities. Because in situ sediment remediation is an emerging strategy, much remains to be learned about the field conditions under which amendments can be effective, the resilience of amendment materials toward extreme weather conditions, and the optimal design of engineered applications. Here we report the results of a multi-year, pilot-scale field investigation designed to measure the persistence and efficacy of AC amendments to reduce the bioavailability of polychlorinated biphenyls (PCBs) in an intertidal Phragmites marsh. The amendments tested were granular AC (GAC), GAC with a layer of sand, and a pelletized fine AC. Key metrics presented include vertically-resolved black carbon concentrations in sediment and PCB concentrations in sediment, porewater, and several invertebrate species. The results demonstrate that all three amendments withstood Hurricane Sandy and remained in place for the duration of the study, successfully reducing porewater PCB concentrations by 34-97%. Reductions in invertebrate bioaccumulation were observed in all amendment scenarios, with pelletized fine AC producing the most pronounced effect. Our findings support the use of engineered AC amendments in intertidal marshes, and can be used to inform amendment design, delivery, and monitoring at other contaminated sediment sites. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Comparison of intestinal microbiota and activities of digestive and immune-related enzymes of sea cucumber Apostichopus japonicus in two habitats

NASA Astrophysics Data System (ADS)

Wang, Qi; Zhang, Xiumei; Chen, Muyan; Li, Wentao; Zhang, Peidong

2017-09-01

Sea cucumber Apostichopus japonicus stock enhancement by releasing hatchery-produced seeds is a management tool used to recover its population under natural environmental conditions. To assess the suitability of releasing sites, we examined the microbiota of the gut contents of A. japonicus from two populations (one in sandy-muddy seagrass beds and one in rocky intertidal reefs) and the microbiota in their surrounding sediments. The activities of digestive and immune-related enzymes in the A. japonicus were also examined. The results indicated that higher bacterial richness and Shannon diversity index were observed in all the seagrass-bed samples. There were significant differences in intestinal and sediment microorganisms between the two habitats, with a 2.87 times higher abundance of Firmicutes in the seagrass bed sediments than that in the reefs. Meanwhile, Bacteroidetes and Actinobacteria were significantly higher abundant in the gut content of A. japonicus from seagrass bed than those from the reefs. In addition, the seagrass-bed samples exhibited a relatively higher abundance of potential probiotics. Principal coordinates analysis and heatmap showed the bacterial communities were classified into two groups corresponding to the two habitat types. Moreover, compared to A. japonicus obtained from rocky intertidal habitat, those obtained from the seagrass bed showed higher lysozyme, superoxide dismutase and protease activities. Our results suggest that bacterial communities present in seagrass beds might enhance the digestive function and immunity of A. japonicus. Therefore, compared with the rocky intertidal reef, seagrass bed seems to be more beneficial for the survival of A. japonicus.

Polycyclic Aromatic Hydrocarbons in Sediments and Bivalves on the Pacific Coast of Japan: Influence of Tsunami and Fire

PubMed Central

Onozato, Mayu; Nishigaki, Atsuko; Okoshi, Kenji

2016-01-01

Surface sediments and at least one edible bivalve species (Ruditapes philippinarum, Mytilus galloprovincialis, and Crassostrea gigas) were collected from each of seven intertidal sites in Japan in 2013. The sites had experienced varying levels of tsunami and fire disturbance following the major earthquake of 2011. Eight polycyclic aromatic hydrocarbons (PAHs) were identified and analyzed by gas chromatography–mass spectrometry. Total sediment PAH concentration (CT), the sum of the average concentrations of the eight PAHs, was 21–1447 μg kg-1-dry. Relative to the average level of one type of PAH in sediments collected around Japan in 2002 (benzo[a]pyrene = 21 μg kg-1-dry), five of the seven sites showed concentrations significantly lower than this average in 2013. The CTs for the three bivalves (134–450 μg kg-1-dry) were within the range of the previous reports (2.2–5335 μg kg-1-dry). The data suggest that the natural disaster did not increase PAH concentrations or affect the distribution within sediment or bivalves in Tohoku district. Although PAH concentrations at the sites pose no risk to human health, the findings highlight that the observed PAH levels derive from pre- rather than post-quake processes. PMID:27232189

Effect of Mudflat Trampling on Activity of Intertidal Crabs

NASA Astrophysics Data System (ADS)

Kim, Tae Won; Kim, Sanha; Lee, Jung-Ah

2018-03-01

Many people visit intertidal mudflats to collect bait and seafood, or for eco-tourism and recreation, and as a consequence trample on the mudflats frequently. Trampling would not be life threatening to most animals in the intertidal flats as they have evolved hiding behavior to escape predation. However, what is the effect of trampling on the behavior of intertidal animals? In this study, the effect of mudflat trampling on the activity of crabs (e.g. fiddler crabs, sentinel crabs) living on the mudflat was explored. The number of crabs active on the mudflat surface in experimental plots (1.5 × 1.5 m2) before and after (10 min. and 30 min.) trampling of three different intensities (Heavy trampling = 60 steps; Moderate trampling = 20 steps; and No trampling) was compared in two different mudflat systems. After trampling, the number of crabs active on the surface decreased and was significantly lower than that of control plots. The more intensively trampled the mudflat was, the fewer crabs were active on the mudflat surface. Surprisingly, the number of active crabs did not recover even 30 min. after trampling. The results clearly support the hypothesis that trampling can severely interfere with the behavior of crabs living on intertidal mudflats.

ZOSTERA MARINA IN A PACIFIC NORTHWEST ESTUARY: WHAT FACTORS CONTROL INTERTIDAL DISTRIBUTION?

EPA Science Inventory

The impact of four factors (desiccation, macroalgae, erosion, light) on the distribution of Zostera marina was examined across tidal and bathymetric slope gradients. Data detailing seagrass characteristics, including 1 production, macroalgae biomass and sediment characteristics ...

Interactions between Benthic Copepods, Bacteria and Diatoms Promote Nitrogen Retention in Intertidal Marine Sediments

PubMed Central

Stock, Willem; Heylen, Kim; Sabbe, Koen; Willems, Anne; De Troch, Marleen

2014-01-01

The present study aims at evaluating the impact of diatoms and copepods on microbial processes mediating nitrate removal in fine-grained intertidal sediments. More specifically, we studied the interactions between copepods, diatoms and bacteria in relation to their effects on nitrate reduction and denitrification. Microcosms containing defaunated marine sediments were subjected to different treatments: an excess of nitrate, copepods, diatoms (Navicula sp.), a combination of copepods and diatoms, and spent medium from copepods. The microcosms were incubated for seven and a half days, after which nutrient concentrations and denitrification potential were measured. Ammonium concentrations were highest in the treatments with copepods or their spent medium, whilst denitrification potential was lowest in these treatments, suggesting that copepods enhance dissimilatory nitrate reduction to ammonium over denitrification. We hypothesize that this is an indirect effect, by providing extra carbon for the bacterial community through the copepods' excretion products, thus changing the C/N ratio in favour of dissimilatory nitrate reduction. Diatoms alone had no effect on the nitrogen fluxes, but they did enhance the effect of copepods, possibly by influencing the quantity and quality of the copepods' excretion products. Our results show that small-scale biological interactions between bacteria, copepods and diatoms can have an important impact on denitrification and hence sediment nitrogen fluxes. PMID:25360602

Bioavailability of trace metals in sediments of a recovering freshwater coastal wetland in China's Yellow River Delta, and risk assessment for the macrobenthic community.

PubMed

Yang, Wei; Li, Xiaoxiao; Pei, Jun; Sun, Tao; Shao, Dongdong; Bai, Junhong; Li, Yanxia

2017-12-01

We investigated the speciation of trace metals and their ecological risks to macrobenthic communities in a recovering coastal wetland of China's Yellow River Delta during the freshwater release project. We established 16 sampling sites in three restoration areas and one intertidal reference area, and collected sediments and macrobenthos four times from 2014 to 2015. The instability index for the trace metals showed a moderate risk for Mn and a high risk for Cd. For both Mn and Cd, the carbonate and FeMn-bound fractions appear to contribute mostly to the instability and bioavailability indexes, but for Cd, the exchangeable fraction also have a much higher contribution. The bioavailability index indicated higher bioavailability of trace metals in freshwater restoration areas than that in the intertidal area. The single-factor contamination index indicated that most trace metal concentrations in the macrobenthos were in excess of the national standard. The biota-sediment accumulation factor suggested that the macrobenthos accumulated most As, Cd, and Cu. Redundancy analysis showed clear relationships between the macrobenthos and sediment metal concentrations. Our results will help wetland managers to assess the bioaccumulation risks based on metal speciation, and to improve management of these recovering freshwater wetland ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Maturation, fecundity, and intertidal spawning of Pacific sand lance in the northern Gulf of Alaska

USGS Publications Warehouse

Robards, Martin D.; Piatt, John F.; Rose, G.A.

1999-01-01

Pacific sand lance Ammodytes hexapterus in Kachemak Bay, Alaska, showed no sexual dimorphism in length-to-weight (gonad-free) ratio or length-at-age relationship. Most matured in their second year, males earlier in the season than females, but females (31%) attained a higher gonadosomatic index than males (21%). Sand lance spawned intertidally once each year in late September and October on fine gravel or sandy beaches soon after the seasonal peak in water temperatures. Sand lance in Cook Inlet and Prince William Sound displayed similar maturation schedules. Schools were dominated 2: 1 by males as they approached the intertidal zone at a site where spawning has taken place for decades. Sand lance spawned vigorously in dense formations, leaving scoured pits in beach sediments. Fecundity of females (93–199 mm) was proportional to length, ranging from 1468 to 16 081 ova per female. About half of the overall spawning school fecundity was derived from age group 1 females (55% of the school by number). Spawned eggs were 1·02 mm in diameter, demersal, slightly adhesive, and deposited in the intertidal just below the waterline. Sand lance embryos developed over 67 days through periods of intertidal exposure and sub-freezing air temperatures.

Alkalinity production in intertidal sands intensified by lugworm bioirrigation.

PubMed

Rao, Alexandra M F; Malkin, Sairah Y; Montserrat, Francesc; Meysman, Filip J R

2014-07-05

Porewater profiles and sediment-water fluxes of oxygen, nutrients, pH, calcium, alkalinity, and sulfide were measured in intertidal sandflat sediments from the Oosterschelde mesotidal lagoon (The Netherlands). The influence of bioturbation and bioirrigation by the deep-burrowing polychaete Arenicola marina on the rates and sources of benthic alkalinity generation was examined by comparing measurements in intact and defaunated sediment cores before and after the addition of A. marina in summer and fall 2011. Higher organic matter remineralization rates, shallower O 2 penetration, and greater sediment-water solute fluxes were observed in summer, consistent with higher sediment community metabolic rates at a higher temperature. Lugworm activity stimulated porewater exchange (5.1 × in summer, 1.9 × in fall), organic matter remineralization (6.2 × in summer, 1.9 × in fall), aerobic respiration (2.4 × in summer, 2.1 × in fall), alkalinity release (4.7 × in summer, 4.0 × in fall), nutrient regeneration, and iron cycling. The effects of lugworm activity on net sediment-water fluxes were similar but more pronounced in summer than in fall. Alkalinity release in fall was entirely driven by metabolic carbonate dissolution, while this process explained between 22 and 69% of total alkalinity production in summer, indicating the importance of other processes in this season. By enhancing organic matter remineralization and the reoxidation of reduced metabolites by the sediment microbial community, lugworm activity stimulated the production of dissolved inorganic carbon and metabolic acidity, which in turn enhanced metabolic CaCO 3 dissolution efficiency. In summer, evidence of microbial long distance electron transport (LDET) was observed in defaunated sediment. Thus, alkalinity production by net carbonate dissolution was likely supplemented by anaerobic respiration and LDET in summer.

Stable carbon isotope fractionation during bacterial acetylene fermentation: Potential for life detection in hydrocarbon-rich volatiles of icy planet(oid)s

USGS Publications Warehouse

Miller, Laurence; Baesman, Shaun; Oremland, Ron

2015-01-01

We report the first study of stable carbon isotope fractionation during microbial fermentation of acetylene (C2H2) in sediments, sediment enrichments, and bacterial cultures. Kinetic isotope effects (KIEs) averaged 3.7 ± 0.5‰ for slurries prepared with sediment collected at an intertidal mudflat in San Francisco Bay and 2.7 ± 0.2‰ for a pure culture of Pelobacter sp. isolated from these sediments. A similar KIE of 1.8 ± 0.7‰ was obtained for methanogenic enrichments derived from sediment collected at freshwater Searsville Lake, California. However, C2H2 uptake by a highly enriched mixed culture (strain SV7) obtained from Searsville Lake sediments resulted in a larger KIE of 9.0 ± 0.7‰. These are modest KIEs when compared with fractionation observed during oxidation of C1 compounds such as methane and methyl halides but are comparable to results obtained with other C2compounds. These observations may be useful in distinguishing biologically active processes operating at distant locales in the Solar System where C2H2 is present. These locales include the surface of Saturn's largest moon Titan and the vaporous water- and hydrocarbon-rich jets emanating from Enceladus.

Viral Impact on Prokaryotic and Microalgal Activities in the Microphytobenthic Biofilm of an Intertidal Mudflat (French Atlantic Coast)

PubMed Central

Montanié, Hélène; De Crignis, Margot G.; Lavaud, Johann

2015-01-01

This is the first report on viriobenthos activity within the microbial biofilm located at the top-surface of the intertidal mudflat during emersion in Marennes-Oléron Bay (France). By combining in situ and ex situ approaches, the viral production (VP) was linked to the dynamics of prokaryotes and microphytobenthos (MPB). VP averaged 2–4 × 108 viruses ml−1 h−1. VP correlated positively with the Virus to Prokaryote Ratio, and both were correlated negatively with the water content. The virus-induced mortality of prokaryotes was lower in winter than in summer (6.8 vs. 39.7% of the production) and the C-shunting may supply 2–12% of their Carbon Demand, respectively. VP accounted for 79% of loss in Prokaryotes but the response was delayed compared to the increase in VP suggesting a simultaneous release of viruses of MPB origin. This hypothesis is supported by capsid-sizing of virions by transmission electronic microscopy and bioassays. Harvesting and ex situ maintenance of top-surface sediments was carried out to monitor the dynamics of viruses, prokaryotes and MPB after inoculation with benthic or planktonic viruses. Benthic viruses modified the prokaryotic and MPB dynamics and decreased the photosynthesis efficiency in contrast to planktonic viruses that impacted MPB but not the prokaryotes. PMID:26617575

Theme and variations: amphibious air-breathing intertidal fishes.

PubMed

Martin, K L

2014-03-01

Over 70 species of intertidal fishes from 12 families breathe air while emerging from water. Amphibious intertidal fishes generally have no specialized air-breathing organ but rely on vascularized mucosae and cutaneous surfaces in air to exchange both oxygen and carbon dioxide. They differ from air-breathing freshwater fishes in morphology, physiology, ecology and behaviour. Air breathing and terrestrial activity are present to varying degrees in intertidal fish species, correlated with the tidal height of their habitat. The gradient of amphibious lifestyle includes passive remainers that stay in the intertidal zone as tides ebb, active emergers that deliberately leave water in response to poor aquatic conditions and highly mobile amphibious skipper fishes that may spend more time out of water than in it. Normal terrestrial activity is usually aerobic and metabolic rates in air and water are similar. Anaerobic metabolism may be employed during forced exercise or when exposed to aquatic hypoxia. Adaptations for amphibious life include reductions in gill surface area, increased reliance on the skin for respiration and ion exchange, high affinity of haemoglobin for oxygen and adjustments to ventilation and metabolism while in air. Intertidal fishes remain close to water and do not travel far terrestrially, and are unlikely to migrate or colonize new habitats at present, although in the past this may have happened. Many fish species spawn in the intertidal zone, including some that do not breathe air, as eggs and embryos that develop in the intertidal zone benefit from tidal air emergence. With air breathing, amphibious intertidal fishes survive in a variable habitat with minimal adjustments to existing structures. Closely related species in different microhabitats provide unique opportunities for comparative studies. © 2013 The Fisheries Society of the British Isles.

Gastropod growth and survival as bioindicators of stress associated with high nutrients in the intertidal of a shallow temperate estuary

NASA Astrophysics Data System (ADS)

Marsden, Islay D.; Baharuddin, Nursalwa

2015-04-01

The effects of multiple stressors on estuarine organisms are not well understood. Using cage experiments we measured the survival and growth of the pulmonate gastropod Amphibola crenata at five locations which differed contaminant levels. Water nutrients came from a nearby sewage treatment works and the sediment contained low levels of trace metals. Over 6 weeks of exposure, sediment surface chlorophyll levels varied amongst locations. The Chl a values were positively correlated with sediment N and P and trace metals As, Cd, Cu, Pb and Zn. Pulmonate survival depended on location, highest mortality was from a site close to the treatment plant and mortality rate of large individuals decreased significantly with distance away from it. For four locations, medium A. crenata had higher survival than small (juveniles) or adults. Growth rates of small individuals exceeded those for medium and large A. crenata. The mean length increment/week for medium gastropods ranged between 0.49 and 1.11 mm and was negatively correlated with the amount of Chl a in the surface sediment, suggesting the negative effects of eutrophication on gastropod growth. Growth rate of the pulmonate was not correlated with nutrient concentration or trace metal concentrations in the sediment. The dry weight condition index (CI) did not correlate with the growth rate, and for medium individuals, was unaffected by any of the environmental variables. The CI of small individuals was negatively affected by increasing water nutrient levels and the CI of large individuals negatively affected by increasing sediment nutrients and trace metal concentrations. The results from this study suggest that gastropod growth and survival could be used as tools to monitor the effects of changing nutrient levels and recovery from eutrophication within temperate estuaries.

Mercury accumulation and attenuation at a rapidly forming delta with a point source of mining waste

PubMed Central

Johnson, Bryce E.; Esser, Bradley K.; Whyte, Dyan C.; Ganguli, Priya M.; Austin, Carrie M.; Hunt, James R.

2009-01-01

The Walker Creek intertidal delta of Tomales Bay, California is impacted by a former mercury mine within the watershed. Eleven short sediment cores (10 cm length) collected from the delta found monomethylmercury (MMHg) concentrations ranging from 0.3 to 11.4 ng/g (dry wt.), with lower concentrations occurring at the vegetated marsh and upstream channel locations. Algal mats common to the delta’s sediment surface had MMHg concentrations ranging from 7.5 to 31.5 ng/g, and the top 1 cm of sediment directly under the mats had two times greater MMHg concentrations compared to adjacent locations without algal covering. Spatial trends in resident biota reflect enhanced MMHg uptake at the delta compared to other bay locations. Eighteen sediment cores, 1 to 2 meters deep, collected from the 1.2 km2 delta provide an estimate of a total mercury (Hg) inventory of 2500 ± 500 kg. Sediment Hg concentrations ranged from pre-mining background conditions of approximately 0.1 μg/g to a post-mining maximum of 5 μg/g. Sediment accumulation rates were determined from three sediment cores using measured differences of 137Cs activity. We estimate a pre-mining Hg accumulation of less than 20 kg/yr, and a period of maximum Hg accumulation in the 1970s and 1980s with loading rates greater than 50 kg/yr, corresponding to the failure of a tailings dam at the mine site. At the time of sampling (2003) over 40 kg/yr of Hg was still accumulating at the delta, indicating limited recovery. We attribute observed spatial evolution of elevated Hg levels to ongoing inputs and sediment re-working, and estimate the inventory of the anthropogenic fraction of total Hg to be at least 1500 ± 300 kg. We suggest ongoing sediment inputs and methylation at the deltaic surface support enhanced mercury levels for resident biota and transfer to higher trophic levels throughout the Bay. PMID:19539980

Infilling and flooding of the Mekong River incised valley during deglacial sea-level rise

NASA Astrophysics Data System (ADS)

Tjallingii, Rik; Stattegger, Karl; Wetzel, Andreas; Van Phach, Phung

2010-06-01

The abrupt transition from fluvial to marine deposition of incised-valley-fill sediments retrieved from the southeast Vietnamese shelf, accurately records the postglacial transgression after 14 ka before present (BP). Valley-filling sediments consist of fluvial mud, whereas sedimentation after the transgression is characterized by shallow-marine carbonate sands. This change in sediment composition is accurately marked in high-resolution X-ray fluorescence (XRF) core scanning records. Rapid aggradation of fluvial sediments at the river mouth nearly completely filled the Mekong incised valley prior to flooding. However, accumulation rates strongly reduced in the valley after the river-mouth system flooded and stepped back. This also affected the sediment supply to deeper parts of the southeast Vietnamese shelf. Comparison of the Mekong valley-filling with the East Asian sea-level history of sub- and inter-tidal sediment records shows that the transgressive surface preserved in the incised-valley-fill records is a robust sea-level indicator. The valley was nearly completely filled with fluvial sediments between 13.0 and 9.5 ka BP when sea-level rose rather constantly with approximately 10 mm/yr, as indicated by the East Asian sea-level record. At shallower parts of the shelf, significant sediment reworking and the establishment of estuarine conditions at the final stage of infilling complicates accurate dating of the transgressive surface. Nevertheless, incised-valley-fill records and land-based drill sites indicate a vast and rapid flooding of the shelf from the location of the modern Vietnamese coastline to the Cambodian lowlands between 9.5 ka and 8.5 ka BP. Fast flooding of this part of the shelf is related with the low shelf gradient and a strong acceleration of the East Asian sea-level rise from 34 to 9 meter below modern sea level (mbsl) corresponding to the sea-level jump of melt water pulse (MWP) 1C.

Bedform Dimensions and Suspended Sediment Observations in a Mixed Sand-Mud Intertidal Environment

NASA Astrophysics Data System (ADS)

Lichtman, I. D.; Amoudry, L.; Peter, T.; Jaco, B.

2016-02-01

Small-scale bedforms, such as ripples, can profoundly modify near-bed hydrodynamics, near-bed sediment transport and resuspension, and benthic-pelagic fluxes. Knowledge of their dimensions is important for a number of applications. Fundamentally different processes can occur depending on the dimensions of ripples: for low and long ripples, the bed remains dynamically flat and diffusive processes dominate sediment entrainment; for steep ripples, flow separation occurs above the ripples creating vortices, which are far more efficient at entraining sediment into the water column. Recent laboratory experiments for mixtures of sand and mud have shown that bedform dimensions decrease with increasing sediment mud content. However, these same experiments also showed that mud is selectively taken into suspension when bedforms are created and migrate on the bed, leaving sandy bedforms. This entrainment process, selectively suspending fine sediment, is referred to as winnowing. To improve our understanding of bedform and entrainment dynamics of mixed sediments, in situ observations were made on intertidal flats in the Dee Estuary, United Kingdom. A suite of instruments were deployed collecting co-located measurements of the near-bed hydrodynamics, waves, small-scale bed morphology and suspended sediment. Three sites were occupied consecutively, over a Spring-Neap cycle, collecting data for different bed compositions, tide levels and wind conditions. Bed samples were taken when the flats became exposed at low water and a sediment trap collected suspended load when inundated. This study will combine these measurements to investigate the interactions between small-scale bed morphology, near-bed hydrodynamics and sediment entrainment. We will examine bedform development in the complex hydrodynamic and wave climate of tidal flats, in relation to standard ripple predictors. We will also relate the variability in small-scale bedforms to variation in hydrodynamic and wave conditions, and to suspension and entrainment processes for mixed sediments.

Microbial community structure of sandy intertidal sediments in the North Sea, Sylt-Rømø Basin, Wadden Sea.

PubMed

Musat, Niculina; Werner, Ursula; Knittel, Katrin; Kolb, Steffen; Dodenhof, Tanja; van Beusekom, Justus E E; de Beer, Dirk; Dubilier, Nicole; Amann, Rudolf

2006-06-01

Molecular biological methods were used to investigate the microbial diversity and community structure in intertidal sandy sediments near the island of Sylt (Wadden Sea) at a site which was characterized for transport and mineralization rates in a parallel study (D. de Beer, F. Wenzhöfer, T. Ferdelman, S.E. Boehme, M. Huettel, J.E.E. van Beusekom, M.E. Böttcher, N. Musat, N. Dubilier, Transport and mineralization rates in North Sea sandy intertidal sediments, Sylt-Romo Basin, Wadden Sea, Limnol. Oceanogr. 50 (2005) 113-127). Comparative 16S rRNA sequence analysis revealed a high bacterial diversity. Most sequences retrieved by PCR with a general bacterial primer set were affiliated with Bacteroidetes, Gammaproteobacteria, Deltaproteobacteria and the Pirellula cluster of Planctomycetales. Fluorescence in situ hybridization (FISH) and slot-blot hybridization with group-specific rRNA-targeted oligonucleotide probes were used to characterize the microbial community structure over depth (0-12 cm) and seasons (March, July, October). We found high abundances of bacteria with total cell numbers up to 3 x 10(9) cells ml(-1) and a clear seasonal variation, with higher values in July and October versus March. The microbial community was dominated by members of the Planctomycetes, the Cytophaga/Flavobacterium group, Gammaproteobacteria, and bacteria of the Desulfosarcina/Desulfococcus group. The high abundance (1.5 x 10(7)-1.8 x 10(8) cells ml(-1) accounting for 3-19% of all cells) of presumably aerobic heterotrophic polymer-degrading planctomycetes is in line with the high permeability, deep oxygen penetration, and the high rates of aerobic mineralization of algal biomass measured in the sandy sediments by de Beer et al. (2005). The high and stable abundance of members of the Desulfosarcina/Desulfococcus group, both over depth and season, suggests that these bacteria may play a more important role than previously assumed based on low sulfate reduction rates in parallel cores (de Beer et al., 2005).

Climate change, parasitism and the structure of intertidal ecosystems.

PubMed

Poulin, R; Mouritsen, K N

2006-06-01

Evidence is accumulating rapidly showing that temperature and other climatic variables are driving many ecological processes. At the same time, recent research has highlighted the role of parasitism in the dynamics of animal populations and the structure of animal communities. Here, the likely interactions between climate change and parasitism are discussed in the context of intertidal ecosystems. Firstly, using the soft-sediment intertidal communities of Otago Harbour, New Zealand, as a case study, parasites are shown to be ubiquitous components of intertidal communities, found in practically all major animal species in the system. With the help of specific examples from Otago Harbour, it is demonstrated that parasites can regulate host population density, influence the diversity of the entire benthic community, and affect the structure of the intertidal food web. Secondly, we document the extreme sensitivity of cercarial production in parasitic trematodes to increases in temperature, and discuss how global warming could lead to enhanced trematode infections. Thirdly, the results of a simulation model are used to argue that parasite-mediated local extinctions of intertidal animals are a likely outcome of global warming. Specifically, the model predicts that following a temperature increase of less than 4 degrees C, populations of the amphipod Corophium volutator, a hugely abundant tube-building amphipod on the mudflats of the Danish Wadden Sea, are likely to crash repeatedly due to mortality induced by microphallid trematodes. The available evidence indicates that climate-mediated changes in local parasite abundance will have significant repercussions for intertidal ecosystems. On the bright side, the marked effects of even slight increases in temperature on cercarial production in trematodes could form the basis for monitoring programmes, with these sensitive parasites providing early warning signals of the environmental impacts of global warming.

Sulfide oxidation and distribution of metals near abandoned copper mines in coastal environments, Prince William Sound, Alaska, USA

USGS Publications Warehouse

Koski, R.A.; Munk, L.; Foster, A.L.; Shanks, Wayne C.; Stillings, L.L.

2008-01-01

The oxidation of sulfide-rich rocks, mostly leftover debris from Cu mining in the early 20th century, is contributing to metal contamination of local coastal environments in Prince William Sound, Alaska. Analyses of sulfide, water, sediment, precipitate and biological samples from the Beatson, Ellamar, and Threeman mine sites show that acidic surface waters generated from sulfide weathering are pathways for redistribution of environmentally important elements into and beyond the intertidal zone at each site. Volcanogenic massive sulfide deposits composed of pyrrhotite and (or) pyrite + chalcopyrite + sphalerite with subordinate galena, arsenopyrite, and cobaltite represent potent sources of Cu, Zn, Pb, As, Co, Cd, and Hg. The resistance to oxidation among the major sulfides increases in the order pyrrhotite ??? sphalerite < chalcopyrite ??? pyrite; thus, pyrrhotite-rich rocks are typically more oxidized than those dominated by pyrite. The pervasive alteration of pyrrhotite begins with rim replacement by marcasite followed by replacement of the core by sulfur, Fe sulfate, and Fe-Al sulfate. The oxidation of chalcopyrite and pyrite involves an encroachment by colloform Fe oxyhydroxides at grain margins and along crosscutting cracks that gradually consumes the entire grain. The complete oxidation of sulfide-rich samples results in a porous aggregate of goethite, lepidocrocite and amorphous Fe-oxyhydroxide enclosing hydrothermal and sedimentary silicates. An inverse correlation between pH and metal concentrations is evident in water data from all three sites. Among all waters sampled, pore waters from Ellamar beach gravels have the lowest pH (???3) and highest concentrations of base metals (to ???25,000 ??g/L), which result from oxidation of abundant sulfide-rich debris in the sediment. High levels of dissolved Hg (to 4100 ng/L) in the pore waters probably result from oxidation of sphalerite-rich rocks. The low-pH and high concentrations of dissolved Fe, Al, and SO4 are conducive to precipitation of interstitial jarosite in the intertidal gravels. Although pore waters from the intertidal zone at the Threeman mine site have circumneutral pH values, small amounts of dissolved Fe2+ in the pore waters are oxidized during mixing with seawater, resulting in precipitation of Fe-oxyhydroxide flocs along the beach-seawater interface. At the Beatson site, surface waters funneled through the underground mine workings and discharged across the waste dumps have near-neutral pH (6.7-7.3) and a relatively small base-metal load; however, these streams probably play a role in the physical transport of metalliferous particulates into intertidal and offshore areas during storm events. Somewhat more acidic fluids, to pH 5.3, occur in stagnant seeps and small streams emerging from the Beatson waste dumps. Amorphous Fe precipitates in stagnant waters at Beatson have high Cu (5.2 wt%) and Zn (2.3 wt%) concentrations that probably reflect adsorption onto the extremely high surface area of colloidal particles. Conversely, crystalline precipitates composed of ferrihydrite and schwertmannite that formed in the active flow of small streams have lower metal contents, which are attributed to their smaller surface area and, therefore, fewer reactive sorption sites. Seeps containing precipitates with high metal contents may contribute contaminants to the marine environment during storm-induced periods of high runoff. Preliminary chemical data for mussels (Mytilus edulis) collected from Beatson, Ellamar, and Threeman indicate that bioaccumulation of base metals is occurring in the marine environment at all three sites.

Effects of sediment discharge from Namibian diamond mines on intertidal and subtidal rocky-reef communities and the rock lobster Jasus lalandii

NASA Astrophysics Data System (ADS)

Pulfrich, Andrea; Branch, George M.

2014-10-01

Extensive terrestrial diamond mining occurs on the southern coast of Namibia, and at Elizabeth Bay near Lüderitz sediment tailings totalling about 2 million tons.yr-1, have been discharged onto the beach. We report here on monitoring spanning 2004-2012 to assess (1) the impacts of increased tailings discharges following an expansion of the mine in 2005, and (2) recovery after discharges halted in 2009. Sampling covered three levels of wave exposure, and compared impacted sites with comparable unmined reference sites. Benthic communities were quantified on both intertidal and subtidal reefs, and kelp densities and rock-lobster abundances, lengths and sex ratios on subtidal reefs. Prior to intensification of mining, deposition of tailings significantly influenced intertidal communities only at sheltered localities where wave action was insufficient to disperse them. Following the mine expansion, effects spread to both semi-exposed and exposed sites. After mining was suspended, recovery of the biota was limited, even three years later. Reductions of intertidal diversity and grazers, proliferation of macroalgae, and increased dominance by filter feeders were recorded at the impacted sites and were persistent, but the affects of wave exposure on community composition generally exceeded those of mining discharges. On subtidal reefs, tailings deposition reduced predators and grazers, increased filter feeders and ephemeral green algae, and decreased all other algae, possibly driven by light reduction due to plumes of suspended fine sediments. Increased discharges post-2005 also substantially influenced bathymetry, wave and current regimes, transforming 2 km of previously wave-exposed rocky coastline into a semi-exposed sandy beach. Tailings discharge appeared to influence community composition in four ways: (1) inundation and blanketing; (2) increased suspended particulate materials; (3) indirect top-down ripple effects, and (4) light reduction. Throughout the period 2004-2007, tailings-deposition had no detectable effects on the sex ratio, sizes or density of rock lobsters, but following suspension of mining activities, densities in 2010-2012 at impact sites exceeded those at reference sites. High natural variability in the abundance of rock lobsters may mask mining impacts, but the data strongly indicate an absence of any negative effects on rock lobsters.

Foraminiferal assemblages along the intertidal zone of Itapanhaú River, Bertioga (Brazil)

NASA Astrophysics Data System (ADS)

Passos, Camila Cunha; Kukimodo, Isabela; Semensatto, Décio

2017-11-01

Foraminifera found in intertidal zones have been successfully used in studies examining relative sea level monitoring around the world. For this purpose, it is necessary to establish the typical foraminiferal assemblages of different salinity regimes and sediment sub aerial exposition. In the present work we collected 27 sediment samples from 5 transversal transects in the mangroves of the Itapanhaú River (Bertioga, SP, Brazil). Transects were distributed along salinity and altitudinal gradients in order to study the community structure of recent foraminifera in terms of diversity and species composition. We identified 35 species and described 5 groups of species in different environmental settings, from downstream to upstream and from margin to landward in the mangrove forest, associated with salinity regime and sediment proportional exposure time. These variables seem to primarily control species distribution and community structure in the intertidal zone, although dissolution of calcareous taxa cannot be ruled out. The first group is dominated by Ammonia spp. and Elphidium spp., colonizes the mouth of the river on an unvegetated tidal flat in the lowest portion of the intertidal zone, under a polyhaline regime. This group exhibits the smallest sub aerial exposition (19,3%) as well as comparatively high species diversity. The second group is formed by a sample dominated by Trochammina inflata and Arenoparrella mexicana, obtained in a polyhaline area on the margin of the mangrove. The third group is dominated by Miliammina fusca and Ammotium spp., and colonizes mesohaline mangrove forests, with proportional exposure time of between 50 and 75%, and high species diversity. The fourth group comprises communities dominated by M. fusca and T. inflata, and colonizes the intermediate level in the interior of the mangrove forest, exhibiting high species diversity. The fifth group comprises communities broadly dominated by M. fusca, colonizing oligohaline margins and the highest level of polyhaline mangrove forests. This group exhibits the greatest sub aerial exposition and lowest species diversity of all five groups. Hence, these foraminifera groups may serve as a reference with which to interpret drilling core layers and reconstruct relative sea levels in other similar estuarine systems.

Accumulation of Sellafield-derived radiocarbon ((14)C) in Irish Sea and West of Scotland intertidal shells and sediments.

PubMed

Tierney, Kieran M; Muir, Graham K P; Cook, Gordon T; MacKinnon, Gillian; Howe, John A; Heymans, Johanna J; Xu, Sheng

2016-01-01

The nuclear energy industry produces radioactive waste at various stages of the fuel cycle. In the United Kingdom, spent fuel is reprocessed at the Sellafield facility in Cumbria on the North West coast of England. Waste generated at the site comprises a wide range of radionuclides including radiocarbon ((14)C) which is disposed of in various forms including highly soluble inorganic carbon within the low level liquid radioactive effluent, via pipelines into the Irish Sea. This (14)C is rapidly incorporated into the dissolved inorganic carbon (DIC) reservoir and marine calcifying organisms, e.g. molluscs, readily utilise DIC for shell formation. This study investigated a number of sites located in Irish Sea and West of Scotland intertidal zones. Results indicate (14)C enrichment above ambient background levels in shell material at least as far as Port Appin, 265 km north of Sellafield. Of the commonly found species (blue mussel (Mytilus edulis), common cockle (Cerastoderma edule) and common periwinkle (Littorina littorea)), mussels were found to be the most highly enriched in (14)C due to the surface environment they inhabit and their feeding behaviour. Whole mussel shell activities appear to have been decreasing in response to reduced discharge activities since the early 2000s but in contrast, there is evidence of continuing enrichment of the carbonate sediment component due to in-situ shell erosion, as well as indications of particle transport of fine (14)C-enriched material close to Sellafield. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Tidal pulsing alters nitrous oxide fluxes in a temperate intertidal mudflat.

PubMed

Vieillard, A M; Fulweiler, R W

2014-07-01

Environmental pulses, or sudden, marked changes to the conditions within an ecosystem, can be important drivers of resource availability in many systems. In this study, we investigated the effect of tidal pulsing on the fluxes of nitrous oxide (N2O), a powerful greenhouse gas, from a marine intertidal mudflat on the north shore of Massachusetts, USA. We found these tidal flat sediments to be a sink of N2O at low tide with an average uptake rate of -6.7 +/- 2 micromol x m(-2) x h(-1). Further, this N20 sink increased the longer sediments were tidally exposed. These field measurements, in conjunction with laboratory nutrient additions, revealed that this flux appears to be driven primarily by sediment denitrification. Additionally, N2O uptake was most responsive to dissolved inorganic nitrogen with phosphorus (DIN + DIP) addition, suggesting that the N2O consumption process may be P limited. Furthermore, nutrient addition experiments suggest that dissimilatory nitrate reduction to ammonium (DNRA) releases N20 at the highest levels of nitrate fertilization. Our findings indicate that tidal flats are important sinks of N2O, potentially capable of offsetting the release of this potent greenhouse gas by other, nearby ecosystems.

Between a rock and a soft place: Using optical ages to date ancient clam gardens on the Pacific Northwest

PubMed Central

Neudorf, Christina M.; Smith, Nicole; Lepofsky, Dana; Toniello, Ginevra; Lian, Olav B.

2017-01-01

Rock-walled archaeological features are notoriously hard to date, largely because of the absence of suitable organic material for radiocarbon dating. This study demonstrates the efficacy of dating clam garden wall construction using optical dating, and uses optical ages to determine how sedimentation rates in the intertidal zone are affected by clam garden construction. Clam gardens are rock-walled, intertidal terraces that were constructed and maintained by coastal First Nation peoples to increase bivalve habitat and productivity. These features are evidence of ancient shellfish mariculture on the Pacific Northwest and, based on radiocarbon dating, date to at least the late Holocene. Optical dating exploits the luminescence signals of quartz or feldspar minerals to determine the last time the minerals were exposed to sunlight (i.e., their burial age), and thus does not require the presence of organic material. Optical ages were obtained from three clam garden sites on northern Quadra Island, British Columbia, and their reliability was assessed by comparing them to radiocarbon ages derived from shells underneath the clam garden walls, as well as below the terrace sediments. Our optical and radiocarbon ages suggest that construction of these clam garden walls commenced between ~1000 and ~1700 years ago, and our optical ages suggest that construction of the walls was likely incremental and increased sedimentation rates in the intertidal zone by up to fourfold. Results of this study show that when site characteristics are not amenable to radiocarbon dating, optical dating may be the only viable geochronometer. Furthermore, dating rock-walled marine management features and their geomorphic impact can lead to significant advances in our understanding of the intimate relationships that Indigenous peoples worldwide developed with their seascapes. PMID:28182645

A Review of distribution and quantity of lingering subsurface oil from the Exxon Valdez Oil Spill

NASA Astrophysics Data System (ADS)

Nixon, Zachary; Michel, Jacqueline

2018-01-01

Remaining lingering subsurface oil residues from the Exxon Valdez oil spill (EVOS) are, at present, patchily distributed across the geologically complex and spatially extensive shorelines of Prince William Sound and the Gulf of Alaska. We review and synthesize previous literature describing the causal geomorphic and physical mechanisms for persistence of oil in the intertidal subsurface sediments of these areas. We also summarize previous sampling and modeling efforts, and refine previously presented models with additional data to characterize the present-day linear and areal spatial extent, and quantity of lingering subsurface oil. In the weeks after the spill in March of 1989, approximately 17,750 t of oil were stranded along impacted shorelines, and by October of 1992, only 2% of the mass of spilled oil was estimated to remain in intertidal areas. We estimate that lingering subsurface residues, generally between 5 and 20 cm thick and sequestered below 10-20 cm of clean sediment, are present over 30 ha of intertidal area, along 11.4 km of shoreline, and represent approximately 227 t or 0.6% of the total mass of spilled oil. These residues are typically located in finer-grained sand and gravel sediments, often under an armor of cobble- or boulder-sized clasts, in areas with limited groundwater flow and porosity. Persistence of these residues is correlated with heavy initial oil loading together with localized sheltering from physical disturbance such as wave energy within the beach face. While no longer generally bioavailable and increasingly chemically weathered, present removal rates for these remaining subsurface oil residues have slowed to nearly zero. The only remaining plausible removal mechanisms will operate over time scales of decades.

Variability of O2, H2S, and pH in intertidal sediments measured on a highly resolved spatial and temporal scale

NASA Astrophysics Data System (ADS)

Walpersdorf, E.; Werner, U.; Bird, P.; de Beer, D.

2003-04-01

We investigated the variability of O_2, pH, and H_2S in intertidal sediments to assess the time- and spatial scales of changes in environmental conditions and their effects on bacterial activities. Measurements were performed over the tidal cycle and at different seasons by the use of microsensors attached to an autonomous in-situ measuring device. This study was carried out at a sand- and a mixed flat in the backbarrier area of Spiekeroog (Germany) within the frame of the DFG research group "Biogeochemistry of the Wadden Sea". Results showed that O_2 variability was not pronounced in the coastal mixed flat, where only extreme weather conditions could increase O_2 penetration. In contrast, strong dynamics in O_2 availability, pH and maximum penetration depths of several cm were found at the sandflat. In these highly permeable sediments, we directly observed tidal pumping: at high tide O_2-rich water was forced into the plate and at low tide anoxic porewater drained off the sediment. From the lower part of the plate where organic rich clayey layers were embedded in the sediment anoxic water containing H_2S leaked out during low tide. Thus advective processes, driven by the tidal pump, waves and currents, control O_2 penetration and depth distribution of H_2S and pH. The effects of the resulting porewater exchange on mineralization rates and microbial activities will be discussed.

Long-term environmental and health implications of morphological change and sediment transport with respect to contaminants

NASA Astrophysics Data System (ADS)

Sneddon, Christopher; Copplestone, David; Tyler, Andrew; Hunter, Peter; Smith, Nick

2014-05-01

The EPSRC-funded Adaptation and Resilience of Coastal Energy Supply (ARCoES) project encompasses four research strands, involving 14 institutions and six PhD studentships. ARCoES aims to determine the threats posed to future energy generation and the distribution network by flooding and erosion, changing patterns of coastal sedimentation, water temperature and the distribution of plants and animals in the coastal zone. Whilst this research has direct benefits for the operation of coastal power stations, ARCoES aims to have a wider stakeholder engagement through assessing how the resilience of coastal communities may be altered by five hundred years of coastal evolution. Coastal evolution will have substantial implications for the energy sector of the North West of England as former waste storage sites are eroded and remobilised within the intertidal environment. The current intertidal environmental stores of radioactivity will also experience reworking as ocean chemistry changes and saltmarsh chronologies are reworked in response to rising sea levels. There is a duel requirement to understand mass sediment movement along the North West coast of England as understanding the sediment transport dynamics is key to modelling long term coastal change and understanding how the environmental store of radioactivity will be reworked. The University of Stirling is researching the long-term environmental and health implications of remobilisation and transport of contaminated sediments around the UK coastline. Using a synergy of hyperspectral and topographic information the mobilisation of sediment bound contaminants within the coastal environment will be investigated. Potential hazards posed by contaminants are determined by a set of environmental impact test criteria which evaluate the bio-accessibility and ionising dose of contaminants. These test criteria will be used to comment on the likely environmental impact of modelled sediment transport and anticipated changes in ocean chemistry.

Effects of nourishment on the form and function of an estuarine beach

USGS Publications Warehouse

Jackson, N.L.; Nordstrom, K.F.; Saini, S.; Smith, D.R.

2010-01-01

Beach nourishment programs in estuaries can enhance shore protection, but they decrease habitat suitability by creating higher berms and wider backshores than would occur under natural conditions. Use of sediment sources from outside the area can result in sedimentary characteristics that differ from native sediments on the surface and at depth, altering conditions for both aeolian transport to dunes and interstitial fauna. Field data were gathered on an estuarine beach to determine differences in beach profile change, depth of sediment reworking, and potential for aeolian transport due to nourishment. Data were gathered over a 20-month period 6 months prior to nourishment, 3 days after nourishment, 6 months after nourishment, and 14 months after nourishment when the beach was mechanically graded to eliminate a vertical scarp in the foreshore. The nourishment consisted of 87,900m3 of sediment emplaced to create a 1.34-km-long, 30-m-wide berm 2.3m above mean tide level. Seven percent of the fill was removed from the profile within 6 months after nourishment, accompanied by 7m in horizontal retreat of the artificial berm. The fill on the backshore remained above the zone of wave influence over a winter storm season and was separated from the active foreshore by the scarp. Nourished sediments on the intertidal foreshore were significantly different from native sediments to a depth of 0.20m below the surface. A lag surface of coarse sediment formed by deflation on the backshore, resulting in a rate of aeolian transport <2% of the rate on the wave-reworked foreshore.Nourishing a beach to a level higher than would be created by natural processes can create a profile that compartmentalizes and restricts transport of sediment and movement of fauna between the foreshore and backshore. Mechanical grading can eliminate the scarp, allow for faunal interaction, and reestablish wave reworking of the backshore that will facilitate aeolian transport. Using an initial design to nourish the backshore at a lower elevation and allowing a dune to provide protection against flooding during major storms could prevent a scarp from forming and eliminate the need for follow-up grading. ?? 2010 Elsevier B.V.

Contrasting effects of ecosystem engineering by the cordgrass Spartina maritima and the sandprawn Callianassa kraussi in a marine-dominated lagoon

NASA Astrophysics Data System (ADS)

Pillay, D.; Branch, G. M.; Dawson, J.; Henry, D.

2011-01-01

Ecosystem engineering by plants and animals significantly influences community structure and the physico-chemical characteristics of marine habitats. In this paper we document the contrasting effects of ecosystem engineering by the cordgrass Spartina maritima and the burrowing sandprawn Callianassa kraussi on physico-chemical characteristics, microflora, macrofaunal community structure and morphological attributes in the high shore intertidal sandflats of Langebaan Lagoon, a marine-dominated system on the west coast of South Africa. Comparisons were made at six sites in the lagoon within Spartina and Callianassa beds, and in a "bare zone" of sandflat between these two habitats that lacks both sandprawns and cordgrass. Sediments in Spartina habitats were consolidated by the root-shoot systems of the cordgrass, leading to low sediment penetrability, while sediments in beds of C. kraussi were more penetrable, primarily due to the destabilising effects of sandprawn bioturbation. Sediments in the "bare zone" had intermediate to low values of penetrability. Sediment organic content was lowest in bare zones and greatest in Spartina beds, while sediment chl- a levels were greatest on bare sand, but were progressively reduced in the Spartina and Callianassa beds. These differences among habitats induced by ecosystem engineering in turn affected the macrofauna. Community structure was different between all three habitats sampled, with species richness being surprisingly greater in Callianassa beds than either the bare zone or Spartina beds. In general, the binding of surface sediments by the root systems of Spartina favoured rigid-bodied, surface-dwelling and tube-building species, while the destabilising effect of bioturbation by C. kraussi favoured burrowing species. The contrasting effects of these ecosystem engineers suggest that they play important roles in increasing habitat heterogeneity. Importantly, the role of bioturbation by C. kraussi in enhancing macrofaunal richness was unexpected. By loosening sediments, reducing anoxia and enhancing organic content, C. kraussi may engineer these high shore habitats to ameliorate environmental stresses or increase food availability.

Establishing a sediment budget in the newly created "Kleine Noordwaard" wetland area in the Rhine-Meuse delta

NASA Astrophysics Data System (ADS)

Christien van der Deijl, Eveline; van der Perk, Marcel; Middelkoop, Hans

2018-03-01

Many deltas are threatened by accelerated soil subsidence, sea-level rise, increasing river discharge, and sediment starvation. Effective delta restoration and effective river management require a thorough understanding of the mechanisms of sediment deposition, erosion, and their controls. Sediment dynamics has been studied at floodplains and marshes, but little is known about the sediment dynamics and budget of newly created wetlands. Here we take advantage of a recently opened tidal freshwater system to study both the mechanisms and controls of sediment deposition and erosion in newly created wetlands. We quantified both the magnitude and spatial patterns of sedimentation and erosion in a former polder area in which water and sediment have been reintroduced since 2008. Based on terrestrial and bathymetric elevation data, supplemented with field observations of the location and height of cut banks and the thickness of the newly deposited layer of sediment, we determined the sediment budget of the study area for the period 2008-2015. Deposition primarily took place in channels in the central part of the former polder area, whereas channels near the inlet and outlet of the area experienced considerable erosion. In the intertidal area, sand deposition especially takes place at low-lying locations close to the channels. Mud deposition typically occurs further away from the channels, but sediment is in general uniformly distributed over the intertidal area, due to the presence of topographic irregularities and micro-topographic flow paths. Marsh erosion does not significantly contribute to the total sediment budget, because wind wave formation is limited by the length of the fetch. Consecutive measurements of channel bathymetry show a decrease in erosion and deposition rates over time, but the overall results of this study indicate that the area functions as a sediment trap. The total contemporary sediment budget of the study area amounts to 35.7×103 m3 year-1, which corresponds to a net area-averaged deposition rate of 6.1 mm year-1. This is enough to compensate for the actual rates of sea-level rise and soil subsidence in the Netherlands.

The role of tidal current characteristics on the development of intertidal morphology in tropical and subtropical mangrove forests

NASA Astrophysics Data System (ADS)

Bryan, K. R.; Nardin, W.; Fagherazzi, S.; Mullarney, J. C.; Norris, B. K.; Henderson, S. M.

2016-12-01

Mangroves are a common intertidal species in tropical and sub-tropical environments, with growth forms that vary substantially between species such as the pencil roots in Avicennia, the prop or stilt roots of Rhizophora and the knee roots in Bruguiera. Here we investigate the role root and tree structures may play on the longterm development of intertidal morphology in mangrove-dominated environments. We use a one-dimensional Delft3D numerical simulation in conjunction with a simple model to determine that the dominant controls on the tidally-driven momentum balance are the frictional characteristics of the forest, which delay the propagation of the tide into the forest. Details of the vegetation at the seaward fringe along with sediment grain size determine the shape of the ensuing profile, with sparser vegetation and coarser grainsizes creating more linear profiles whereas denser vegetation and finer grainsizes generating convex intertidal profiles. Examples showing these different profile developments are provided from the Mekong Delta in Vietnam, which tends to a linear profile, and the Firth of Thames in New Zealand, which has a distinctive convex profile. Preliminary validation using current meter measurements from the Mekong Delta show that the currents diminish quickly between the mudflat seaward of the forest and the fringe, then remain fairly constant several hundred meters into the forest indicating that this linear profile has probably developed into an equilibrium shape. Understanding the forces that shape the development of the intertidal profile shape is critical to predicting the resilience of these sensitive intertidal areas to changes in inundation caused by sea level rise.

Influence of macrofaunal assemblages and environmental heterogeneity on microphytobenthic production in experimental systems.

PubMed

Dyson, Kirstie E; Bulling, Mark T; Solan, Martin; Hernandez-Milian, Gema; Raffaelli, David G; White, Piran C L; Paterson, David M

2007-10-22

Despite the complexity of natural systems, heterogeneity caused by the fragmentation of habitats has seldom been considered when investigating ecosystem processes. Empirical approaches that have included the influence of heterogeneity tend to be biased towards terrestrial habitats; yet marine systems offer opportunities by virtue of their relative ease of manipulation, rapid response times and the well-understood effects of macrofauna on sediment processes. Here, the influence of heterogeneity on microphytobenthic production in synthetic estuarine assemblages is examined. Heterogeneity was created by enriching patches of sediment with detrital algae (Enteromorpha intestinalis) to provide a source of allochthonous organic matter. A gradient of species density for four numerically dominant intertidal macrofauna (Hediste diversicolor, Hydrobia ulvae, Corophium volutator, Macoma balthica) was constructed, and microphytobenthic biomass at the sediment surface was measured. Statistical analysis using generalized least squares regression indicated that heterogeneity within our system was a significant driving factor that interacted with macrofaunal density and species identity. Microphytobenthic biomass was highest in enriched patches, suggesting that nutrients were obtained locally from the sediment-water interface and not from the water column. Our findings demonstrate that organic enrichment can cause the development of heterogeneity which influences infaunal bioturbation and consequent nutrient generation, a driver of microphytobenthic production.

Sulfur reduction in sediments of marine and evaporite environments

NASA Technical Reports Server (NTRS)

Klug, M. J.; Boston, P.; Francois, R.; Gyure, R. A.; Javor, B.; Tribble, G.; Vairavamurthy, A.

1985-01-01

Transformations of sulfur in sediments of ponds ranging in salinities from that of normal seawater to those of brines saturated with sodium chloride were examined. The chemistry of the sediment and pore waters were focused on with emphasis on the fate of sulfate reduction. The effects of increasing salinity on both forms of sulfur and microbial activity were determined. A unique set of chemical profiles and sulfate-reducing activity was found for the sediments of each of the sites examined. The quantity of organic matter in the salt pond sediments was significantly greater than that occurring in the adjacent intertidal site. The total quantitative and qualitative distribution of volatile fatty acids was also greater in the salt ponds. Volatile fatty acids increased with salinity.

Patterns of species diversity in estuarine benthic communities along teh US west coast

EPA Science Inventory

Estuaries in the Pacific North West (PNW) were recently classified by whether the estuary is river- or ocean-dominated, the extent of intertidal to subtidal environments, and spatial salinity patterns. We examine whether these characteristics predict patterns of soft-sediment, m...

MACROALGAL-MEDIATED TRANSFERS OF WATER COLUMN NITROGEN TO INTERTIDAL SEDIMENTS AND SALT MARSH PLANTS. (R825381)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

PETROLEUM HYDROCARBONS IN THE NORTHERN PUGET SOUND AREA. A PILOT DESIGN STUDY

EPA Science Inventory

Hydrocarbon baseline data are needed to assess the potential impact of oil contamination from increased tanker traffic in the Strait of Juan de Fuca. Initial studies were directed to intertidal sediments, mussels and snails from two physically similar areas: Port Angeles, WA and ...

Decline of radionuclides in the nearshore environment following nuclear reactor closure: A U.K. case study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cundy, A.B.; Croudace, I.W.; Warwick, P.E.

1999-09-01

Radioactive discharges from nuclear facilities are frequently made into the marine environment and their fate during and after cessation of discharges is a matter of interest and concern. This study examines the decline of the radionuclides {sup 60} and {sup 65}Zn along the southern UK. coast, over the per 1988--1998, following the closure of the steam-generating heavy water (SGHW) reactor at AEA Winfrith, Dorset, UK. {sup 60}Co and {sup 65}Zn (and other activation products such as {sup 63}Ni and {sup 55}Fe) were widely dispersed in the marine environment off the central south coast of England, due to authorized releases frommore » AEA Winfrith. Significant interaction occurred with clay-rich sediments and biota. A general exponential decline in {sup 60}Co activities (and in {sup 65}Zn activity) is found in intertidal mudflat sediments, seaweed and marine fauna in different areas along the south coast following closure of the reactor in 1990. Effective half-lives are determined which vary from 1 to 4 years in surface sediments ({sup 60}Co only), 1--4 years in seaweed and 0.5--2.5 years in crustaceans, bivalves and molluscs. Physical mixing and bioturbation largely control the rate at which {sup 60}Co declines in surface sediments. Both {sup 60}Co and {sup 65}Zn show a relatively slow rate of decline in seaweed and in marine fauna, showing that even after the virtual cessation of discharge from nuclear facilities, contamination of these organisms may persist for a number of years, albeit at reduced activities. Reasons for this persistence are likely to include absorption of radionuclides from sediment, and release and recycling of radionuclides via breakdown of contaminated organic material.« less

Stable Carbon Isotope Fractionation during Bacterial Acetylene Fermentation: Potential for Life Detection in Hydrocarbon-Rich Volatiles of Icy Planet(oid)s

PubMed Central

Baesman, Shaun M.; Oremland, Ronald S.

2015-01-01

Abstract We report the first study of stable carbon isotope fractionation during microbial fermentation of acetylene (C2H2) in sediments, sediment enrichments, and bacterial cultures. Kinetic isotope effects (KIEs) averaged 3.7 ± 0.5‰ for slurries prepared with sediment collected at an intertidal mudflat in San Francisco Bay and 2.7 ± 0.2‰ for a pure culture of Pelobacter sp. isolated from these sediments. A similar KIE of 1.8 ± 0.7‰ was obtained for methanogenic enrichments derived from sediment collected at freshwater Searsville Lake, California. However, C2H2 uptake by a highly enriched mixed culture (strain SV7) obtained from Searsville Lake sediments resulted in a larger KIE of 9.0 ± 0.7‰. These are modest KIEs when compared with fractionation observed during oxidation of C1 compounds such as methane and methyl halides but are comparable to results obtained with other C2 compounds. These observations may be useful in distinguishing biologically active processes operating at distant locales in the Solar System where C2H2 is present. These locales include the surface of Saturn's largest moon Titan and the vaporous water- and hydrocarbon-rich jets emanating from Enceladus. Key Words: Acetylene—Fermentation—Isotope fractionation—Enceladus—Life detection. Astrobiology 15, 977–986. PMID:26539733

Computing Risk to West Coast Intertidal Rocky Habitat due to ...

EPA Pesticide Factsheets

Compared to marshes, little information is available on the potential for rocky intertidal habitats to migrate upward in response to sea level rise (SLR). To address this gap, we utilized topobathy LiDAR digital elevation models (DEMs) downloaded from NOAA’s Digital Coast GIS data repository to estimate percent change in the area of rocky intertidal habitat in 10 cm increments with eustatic sea level rise. The analysis was conducted at the scale of the four Marine Ecoregions of the World (MEOW) ecoregions located along the continental west coast of the United States (CONUS). Environmental Sensitivity Index (ESI) map data were used to identify rocky shoreline. Such stretches of shoreline were extracted for each of the four ecoregions and buffered by 100 m to include the intertidal and evaluate the potential area for upland habitat migration. All available LiDAR topobathy DEMs from Digital Coast were extracted using the resulting polygons and two rasters were synthesized from the results, a 10 cm increment zone raster and a non-planimetric surface area raster for zonal summation. Current rocky intertidal non-planimetric surface areas for each ecoregion were computed between Mean Higher High Water (MHHW) and Mean Lower Low Water (MLLW) levels established from published datum sheets for tidal stations central to each MEOW ecoregion. Percent change in non-planimetric surface area for the same relative ranges were calculated in 10 cm incremental steps of eustatic S

Selenium fractionation and cycling in the intertidal zone of the Carquinez Strait. Annual report, October 1, 1995--December 31,1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zawislanski, P.T.; McGrath, A.E.; Benson, S.M.

1997-10-01

Selenium geochemistry in tidal wetlands is a topic of continuing study at Lawrence Berkeley National Laboratory. The program of studies described in this report was initiated in the fall of 1994 in response to concerns about elevated Se concentrations in waters, sediments, and biota in the Carquinez Strait. Processes by which selenium is introduced and potentially released from the sediment system have been the focus of research in 1996.

Generation of sedimentary fabrics and facies by repetitive excavation and storm infilling of burrow networks Holocene of south Florida and Caicos Platform, B. W. I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tedesco, L.P.; Wanless, H.R.

Excavation of deep, open burrow networks and subsequent infilling with sediment from the surface produces an entirely new sedimentary deposit and results in obliteration to severe diagenetic transformation of precursor depositional facies. Repetitive excavation and infilling is responsible for creating the preserved depositional facies of many marine deposits. Excavating burrowers occur from intertidal to abyssal depths, and are important throughout the Phanerozoic. The repetitive coupling of deep, open burrow excavation with subsequent storm sediment infilling of open burrow networks is a gradual process that ultimately results in the loss of the original deposit and the generation of new lithologies, fabricsmore » and facies. The new lithologies are produced in the subsurface and possess fabrics, textures and skeletal assemblages that are not a direct reflection of either precursor facies or the surficial depositional conditions. Sedimentary facies generated by repetitive burrow excavation and infilling commonly are massively bedded and generally are mottled skeletal packstones. Skeletal grains usually are well-preserved and coarser components are concentrated in burrow networks, pockets and patches. The coarse skeletal components of burrow-generated facies are a mixture of coarse bioclasts from the precursor facies and both the coarse and fine skeletal material introduced from the sediment surface. Many so-called bioturbated or massive facies may, in fact, be primary depositional facies generated in the subsurface and represent severe diagenetic transformation of originally deposited sequences. In addition, mudstones and wackestones mottled with packstone patches may record storm sedimentation.« less

BENTHIC AMPHIPOD COMMUNITY RESPONSE TO STRESS INDUCED BY ALGAL MATS IN A PACIFIC NORTHWEST ESTUARY

EPA Science Inventory

Amphipod, algal biomass and sediment samples were taken at two- to four-week intervals from June through December, 2000 along lines perpendicular to two transects in Yaquina Bay, OR, extending from within the Zostera marina bed at the river channel edge through intertidal burrowi...

AMPHIPOD COMMUNITY RESPONSE TO STRESS INDUCED BY ALGAL MATS IN A PACIFIC NORTHWEST ESTUARY

EPA Science Inventory

Amphipod, algal and sediment samples were taken at two- to four-week intervals from June through December, 2000 along two transects in Yaquina Bay, OR. The transects extended from within the Zostera marina bed at the river channel edge through intertidal burrowing shrimp ...

Depositional facies, environments and sequence stratigraphic interpretation of the Middle Triassic-Lower Cretaceous (pre-Late Albian) succession in Arif El-Naga anticline, northeast Sinai, Egypt

NASA Astrophysics Data System (ADS)

El-Azabi, M. H.; El-Araby, A.

2005-01-01

The Middle Triassic-Lower Cretaceous (pre-Late Albian) succession of Arif El-Naga anticline comprises various distinctive facies and environments that are connected with eustatic relative sea-level changes, local/regional tectonism, variable sediment influx and base-level changes. It displays six unconformity-bounded depositional sequences. The Triassic deposits are divided into a lower clastic facies (early Middle Triassic sequence) and an upper carbonate unit (late Middle- and latest Middle/early Late Triassic sequences). The early Middle Triassic sequence consists of sandstone with shale/mudstone interbeds that formed under variable regimes, ranging from braided fluvial, lower shoreface to beach foreshore. The marine part of this sequence marks retrogradational and progradational parasequences of transgressive- and highstand systems tract deposits respectively. Deposition has taken place under warm semi-arid climate and a steady supply of clastics. The late Middle- and latest Middle/early Late Triassic sequences are carbonate facies developed on an extensive shallow marine shelf under dry-warm climate. The late Middle Triassic sequence includes retrogradational shallow subtidal oyster rudstone and progradational lower intertidal lime-mudstone parasequences that define the transgressive- and highstand systems tracts respectively. It terminates with upper intertidal oncolitic packstone with bored upper surface. The next latest Middle/early Late Triassic sequence is marked by lime-mudstone, packstone/grainstone and algal stromatolitic bindstone with minor shale/mudstone. These lower intertidal/shallow subtidal deposits of a transgressive-systems tract are followed upward by progradational highstand lower intertidal lime-mudstone deposits. The overlying Jurassic deposits encompass two different sequences. The Lower Jurassic sequence is made up of intercalating lower intertidal lime-mudstone and wave-dominated beach foreshore sandstone which formed during a short period of rising sea-level with a relative increase in clastic supply. The Middle-Upper Jurassic sequence is represented by cycles of cross-bedded sandstone topped with thin mudstone that accumulated by northerly flowing braided-streams accompanying regional uplift of the Arabo-Nubian shield. It is succeeded by another regressive fluvial sequence of Early Cretaceous age due to a major eustatic sea-level fall. The Lower Cretaceous sequence is dominated by sandy braided-river deposits with minor overbank fines and basal debris flow conglomerate.

Ancient Clam Gardens Increased Shellfish Production: Adaptive Strategies from the Past Can Inform Food Security Today

PubMed Central

Groesbeck, Amy S.; Rowell, Kirsten; Lepofsky, Dana; Salomon, Anne K.

2014-01-01

Maintaining food production while sustaining productive ecosystems is among the central challenges of our time, yet, it has been for millennia. Ancient clam gardens, intertidal rock-walled terraces constructed by humans during the late Holocene, are thought to have improved the growing conditions for clams. We tested this hypothesis by comparing the beach slope, intertidal height, and biomass and density of bivalves at replicate clam garden and non-walled clam beaches in British Columbia, Canada. We also quantified the variation in growth and survival rates of littleneck clams (Leukoma staminea) we experimentally transplanted across these two beach types. We found that clam gardens had significantly shallower slopes than non-walled beaches and greater densities of L. staminea and Saxidomus giganteus, particularly at smaller size classes. Overall, clam gardens contained 4 times as many butter clams and over twice as many littleneck clams relative to non-walled beaches. As predicted, this relationship varied as a function of intertidal height, whereby clam density and biomass tended to be greater in clam gardens compared to non-walled beaches at relatively higher intertidal heights. Transplanted juvenile L. staminea grew 1.7 times faster and smaller size classes were more likely to survive in clam gardens than non-walled beaches, specifically at the top and bottom of beaches. Consequently, we provide strong evidence that ancient clam gardens likely increased clam productivity by altering the slope of soft-sediment beaches, expanding optimal intertidal clam habitat, thereby enhancing growing conditions for clams. These results reveal how ancient shellfish aquaculture practices may have supported food security strategies in the past and provide insight into tools for the conservation, management, and governance of intertidal seascapes today. PMID:24618748

An evaluation of intertidal feeding habitats from a shorebird perspective: Towards relevant comparisons between temperate and tropical mudflats

NASA Astrophysics Data System (ADS)

Piersma, Theunis; de Goeij, Petra; Tulp, Ingrid

Macrozoobenthic communities of intertidal soft sediments are reviewed worldwide from the perspective of a mollusc-eating shorebird species. Based on 19 sites, total biomass figures varied between 5 and 80 g AFDM per m 2 (average 24 g AFDM per m 2); no latitudinal trends are apparent. The contribution made by bivalves and gastropods varies between 1% and 99%, north-temperate intertidal flats having relatively more molluscs than tropical flats. Intertidal flats in the tropics contain a greater variety of taxa, with brachiopods in Indonesia and echinoderms in northwest Australia contributing significantly to biomass only there. Limits to the occurrence of avian predators of intertidal benthos are set by the harvestable fraction of the biomass on offer and the costs of living at a particular site. No systematic differences in the harvestable fraction of the total mollusc-biomass for a worldwide occurring shorebird species specializing on molluscs (knots Calidris canutus) were apparent between temperate and tropical intertidal areas, in spite of large differences in maintenance metabolism incurred by these birds. The harvestable fractions of bivalves in the two West African areas (Banc d'Arguin, Mauritania and Guinea-Bissau) tended to be high (23-84% of total biomass in six species), they were relatively low (2-52% in five species) in the temperate Wadden Sea and the tropical northwest Australian site. Harvestable biomass determines the intake rate of shorebirds, as illustrated by functional-response curves of knots feeding on two bivalves species. We argue that the collection of information on size-depth relationships along with faunal and biomass surveys at a range of sites is bound to greatly increase our understanding of both the biology of tidal-flat invertebrates and the resource base underpinning the spectacular seasonal migrations of shorebirds.

Spatial distribution of living (Rose Bengal stained) benthic foraminifera in the Loire estuary (western France)

NASA Astrophysics Data System (ADS)

Mojtahid, M.; Geslin, E.; Coynel, A.; Gorse, L.; Vella, C.; Davranche, A.; Zozzolo, L.; Blanchet, L.; Bénéteau, E.; Maillet, G.

2016-12-01

Ninety-seven surface sediment samples were collected in September 2012 from intertidal and subtidal areas along the Loire estuary (western France). The main objective of this work is to study the spatial distributional patterns of living benthic foraminifera and their link to the environmental parameters (distance to sea, elevation, grain size, total organic carbon, trace metals, sedimentary carbonates, and polycyclic aromatic hydrocarbons) in the Loire estuary. Foraminiferal analysis was also extended to the dead assemblages in thirty-three surface samples from the lower inner estuary. The highest absolute densities of living benthic foraminifera are found in the lower inner estuary within the polyhaline domain. This is attributed to the presence of mudflats with abundant food source, i.e. microphytobenthos. The low densities found in the outer estuary (euhaline domain) are attributed partly to the sandy nature of the sediments and the food source inhabiting this substrate. The near absence of foraminifera in the inner estuary (mesohaline and polyhaline domains) is inferred to the physical disturbance resulting from the regular dredging of the navigation channel. The living assemblages are dominated by three typical estuarine species: Ammonia tepida and Haynesina germanica in the intertidal mudflats of the lower inner estuary and Cribroelphidium excavatum in the sandy subtidal sediments of the lower inner and outer estuary. In the Loire estuary, H. germanica has an unusual intermediate geographical distribution along the estuary between A. tepida and C. excavatum while in most temperate estuaries this species is present upstream in the mesohaline domain. This is most likely the result of the regular dredging of the navigation channel damaging its natural habitat. This might be also the explanation for the total absence of agglutinated species usually dominating the oligohaline domain. The canonical correspondence analysis shows that elevation (and its link to time of emersion), distance to sea (and its correspondence with salinity), and organic carbon content appear to be the primary drivers of foraminiferal distribution. The present study provides for the first time ecological and distribution patterns of living benthic foraminiferal communities in the Loire estuary. This baseline knowledge is necessary for the future studies focusing on the use of benthic foraminifera as bio-indicators in the Loire estuary and in transitional environments in general.

Structure and functional characteristics of the meiofauna community in highly unstable intertidal mudbanks in Suriname and French Guiana (North Atlantic coast of South America)

NASA Astrophysics Data System (ADS)

Christine, Dupuy; Hien, Nguyen Thanh; David, Mizrahi; Jérôme, Jourde; Martine, Bréret; Hélène, Agogué; Laureen, Beaugeard; Pierrick, Bocher

2015-11-01

The North Atlantic coast of South America is influenced by the Amazon River. This coast is considered the muddiest in the world due to the enormous suspended sediment input from the Amazon River. The mobility of the sediment imposes a geomorphological dynamic with a rapid change of shoreline and fast alternation of facies types of the sediment. This study first describes the spatial and functional structure of meiofauna communities of highly unstable intertidal flats along coasts of French Guiana and Suriname in relation to environmental variables. Six sampling sites, composed mainly of muddy sediment, were located 700 km (Kourou) to 1200 km (Nickerie) from the mouth of the Amazon River. The granulometry, chlorophyll a biomass, prokaryote abundance, percentage of organic matter, meiofauna abundance and feeding guilds of nematodes in sediment stations were independent of the distance of the Amazon River mouth and likely were more influenced by the local dynamism of migration of mudbanks. Meiofauna was not more abundant when the sediment was dominated by the finest sediment particles and also when chlorophyll a and prokaryotes, potential prey of meiofauna, were greater. However, as a percentage, small nematodes (biomass of 0.07±0.001 μg ind-1), which are mainly epigrowth-feeders, were more abundant in very fluid mud. Local granulometry and organic matter content appeared to be driving factors of the size structure and functional characteristics of nematodes. Despite the high instability of mudflats, chlorophyll a biomass and meiofauna abundance always tended to be higher toward other world areas. No foraminifera among the six stations of the study were found. Very fluid mud with physical instability of sediment caused a large perturbation to the settlement of meiofauna; the least amounts of chlorophyll a biomass and prokaryotic and meiofauna abundances were found there. Thus, the probable mobility of sediment may select for smaller meiobenthic organisms, mainly epigrowth-feeders nematodes, and disturb the larger organisms in the sediment, and, therefore, they would not permit the settlement of the foraminifera. In addition, no non-permanent meiofauna largely was found in the sediment.

Technical Note: The effects of five different defaunation methods on biogeochemical properties of intertidal sediment

NASA Astrophysics Data System (ADS)

Tolhurst, T. J.; Chapman, M. G.; Underwood, A. J.; Cruz, J. J.

2012-09-01

Various methods have been used to remove organisms from sediments to investigate structure and function of faunal assemblages in intertidal habitats. Nevertheless, little is known about how these treatments affect properties of the sediments themselves, although changing these properties may cause changes in the assemblages, independently of other hypotheses being tested. This study assesses the efficacy of defaunation and effect on selected biogeochemical properties of five different methods of defaunating soft muddy sediments in an estuary. The methods were removal and freezing of sediment, removal and oven-heating, freezing in situ with liquid N2, spraying with formalin and spraying with hydrogen peroxide. The first four of these methods have been used in previous studies, whilst the fifth was considered to be a potentially useful defaunator because it does not leave toxic residues. The first two methods required sediment to be brought back to the lab, disrupting the natural structure of the sediment; the last three were done in situ, with much less disturbance. Variables measured to assess effects of the treatments on the sediment were amount of water, grain size, total carbohydrate, suspension index (relative erosion rate), erosion threshold, chlorophyll a and b, colloidal carbohydrate, Fo (minimal fluorescence) and Fv / Fm (photosynthetic yield). There were no significant effects of any treatment on the first four variables. For the others, effects of defaunation varied from treatment to treatment and with time after treatment. Generally, the greatest disturbance was to the microphytobenthos (MPB, measured by chlorophyll and fluorescence) and related variables. For most treatments, recovery was rapid, but the effects of formalin and H2O2 persisted for a few days. Effects on physical properties of the sediment were mostly minor and insignificant. Removal and freezing or heating, however, caused major changes to the sediments because of the disturbances involved. Choosing the appropriate method of defaunation is very important if interpretations are not to be confounded between the effects of defaunation per se and any effects of changes to other biota (such as microphytobenthos) and/or the properties of sediments caused by the method used to defaunate experimental areas.

Oil persistence on beaches in Prince William Sound - a review of SCAT surveys conducted from 1989 to 2002.

PubMed

Taylor, Elliott; Reimer, Doug

2008-03-01

In 2002, 13 years after the Exxon Valdez oil spill (EVOS), 39 selected sites in Prince William Sound (PWS) were re-surveyed following established shoreline cleanup assessment team (SCAT) field observation procedures to document surface and sub-surface oiling conditions in shoreline sediments and to compare results with those from previous Shoreline Cleanup Assessment Team (SCAT) surveys and other surveys in PWS. The selected sites are locations where EVOS oil persisted in 1992, at the time the Federal and State On-Scene Coordinators determined that the cleanup was complete and that further cleanup activities would provide no net environmental benefit. These sites had been included in a 2001 NOAA survey of shoreline oiling conditions and account for 88% of the sub-surface oil residues (SSO) oil documented by that study. The 2002 field survey found isolated occurrences of residual EVOS surface oil residues (SO) in the form of weathered asphalt pavement at 15 of the 39 sites. This residual SO typically consisted of asphalt in mixed sand/gravel substrate, located within a wave shadow effect created by boulders or bedrock in the upper intertidal to supratidal zone. Residual SO, expressed as a continuous oil cover, was less than 200 m(2) within the approximately 111,120 m(2) surveyed. A total of 1182 pits were dug at locations where SSO residues were present in 1992. Six of the 39 sites and 815 (68%) of the pits contained no residual SSO. Eighty-three percent of pits with SSO residues were found primarily in middle to upper intertidal locations. SSO residues commonly occurred in a discontinuous approximately 3 cm thick band 5-10 cm below the boulder/cobble or pebble/gravel veneer. The SO and SSO occurrences in the 2002 survey closely match the locations where they were found in 1992 and earlier surveys; however, in 2002 residual SSO patches are more discontinuous and thinner than they were in the earlier surveys. These sites are biased toward SSO persistence; those that have SSO residues represent less than 0.5% of the originally oiled shorelines in PWS. Despite evidence of continued oil weathering, both at the surface and in the sub-surface, it is clear that the natural cleaning processes at these particular locations are slow. The slow weathering rates are a consequence of the oil residue being incorporated in finer sediments (fine sand, silt, mix) and isolated from active weathering processes as boulders and outcrops, shallow bedrock asperities, or boulder-armoring create wave shadows and limit effective physical action on shorelines.

Sedimentary controls on modern sand grain coat formation

NASA Astrophysics Data System (ADS)

Dowey, Patrick J.; Worden, Richard H.; Utley, James; Hodgson, David M.

2017-05-01

Coated sand grains can influence reservoir quality evolution during sandstone diagenesis. Porosity can be reduced and fluid flow restricted where grain coats encroach into pore space. Conversely pore-lining grain coats can restrict the growth of pore-filling quartz cement in deeply buried sandstones, and thus can result in unusually high porosity in deeply buried sandstones. Being able to predict the distribution of coated sand grains within petroleum reservoirs is thus important to help find good reservoir quality. Here we report a modern analogue study of 12 sediment cores from the Anllóns Estuary, Galicia, NW Spain, collected from a range of sub-environments, to help develop an understanding of the occurrence and distribution of coated grains. The cores were described for grain size, bioturbation and sedimentary structures, and then sub-sampled for electron and light microscopy, laser granulometry, and X-ray diffraction analysis. The Anllóns Estuary is sand-dominated with intertidal sand flats and saltmarsh environments at the margins; there is a shallowing/fining-upwards trend in the estuary-fill succession. Grain coats are present in nearly every sample analysed; they are between 1 μm and 100 μm thick and typically lack internal organisation. The extent of grain coat coverage can exceed 25% in some samples with coverage highest in the top 20 cm of cores. Samples from muddy intertidal flat and the muddy saltmarsh environments, close to the margins of the estuary, have the highest coat coverage (mean coat coverage of 20.2% and 21.3%, respectively). The lowest mean coat coverage occurs in the sandy saltmarsh (10.4%), beyond the upper tidal limit and sandy intertidal flat environments (8.4%), close to the main estuary channel. Mean coat coverage correlates with the concentration of clay fraction. The primary controls on the distribution of fine-grained sediment, and therefore grain coat distribution, are primary sediment transport and deposition processes that concentrate the clay fraction in the sediment towards the margins of the estuary. Bioturbation and clay illuviation/mechanical infiltration are secondary processes that may redistribute fine-grained sediment and produce grain coats. Here we have shown that detrital grain coats are more likely in marginal environments of ancient estuary-fills, which are typically found in the fining-upward part of progradational successions.

Distribution and weathering of crude oil residues on shorelines 18 years after the Exxon Valdez spill.

PubMed

Boehm, Paul D; Page, David S; Brown, John S; Neff, Jerry M; Bragg, James R; Atlas, Ronald M

2008-12-15

In 2007, a systematic study was conducted to evaluate the form and location of residues of oil buried on Prince William Sound (PWS) shorelines, 18 years after the 1989 Exxon Valdez Oil Spill (EVOS). We took 678 sediment samples from 22 sites that were most heavily oiled in 1989 and known to contain the heaviest subsurface oil (SSO) deposits based on multiple studies conducted since 2001. An additional 66 samples were taken from two sites, both heavily oiled in 1989 and known to be active otter foraging sites. All samples were analyzed for total extractable hydrocarbons (TEH), and 25% were also analyzed for saturated and aromatic hydrocarbon weathering parameters. Over 90% of the samples from all sites contained light or no SSO at all. Of samples containing SSO, 81% showed total polycyclic aromatic hydrocarbon (TPAH) losses greater than 70%, relative to cargo oil, with most having >80% loss. Samples with SSO were observed in isolated patches sequestered by surface boulder and cobble armoring. Samples showing lowest TPAH loss correlated strongly with higher elevations in the intertidal zones. Of the 17 atypical, less-weathered samples having less than 70% loss of TPAH (>30% remaining), only two were found sequestered in the lower intertidal zone, both at a single site. Most of the EVOS oil in PWS has been eliminated due to natural weathering. Some isolated SSO residues remain because they are sequestered and only slowly affected by natural weathering processes that normally would bring about their rapid removal. Even where SSO patches remain, most are highly weathered, sporadically distributed at a small number of sites, and widely separated from biologically productive lower intertidal zones where most foraging by wildlife occurs.

Strong tidal modulation of net ecosystem exchange in a salt marsh in North Inlet, South Carolina

NASA Astrophysics Data System (ADS)

O'Halloran, T. L.; Smith, E. M.; Bogoev, I.

2017-12-01

Along the southeastern US, intertidal salt marshes represent a critical habitat at the interface of the terrestrial and marine environments and perform a variety of ecological functions and services that make them of great economic importance for coastal communities They provide essential fish and shellfish habitat, with a majority of all commercially- and recreationally important fish species being dependent on intertidal marsh habitat during some portion of their life cycle. The penaeid shrimp industry, South Carolina's most economically important fishery, would cease to exist without the critical nursery function provided by intertidal salt marshes. Smooth cordgrass (Spartina alterniflora) is a keystone species in the high salinity marshes of the southeastern U.S., and its functioning is essential to the health and survival of salt marshes under rising sea levels. To better quantify and facilitate prediction of future salt marsh productivity, in May of 2017, we established a new integrated eddy covariance tower system to measure the net ecosystem exchange of carbon in a salt marsh in coastal South Carolina. The tower site is co-located with long-term, ongoing measurements as part of the North Inlet-Winyah Bay National Estuarine Research Reserve (NI-WB NERR). Current sampling conducted within the eddy flux footprint includes: annual measures of the vegetation community at the time of peak biomass; bi-monthly measures of sediment elevation at Sediment Elevation Tables (SETs) located at the upper and lower ends of the flux footprint; monthly sediment porewater salinity and nutrient (ammonium, orthophosphate) and sulfide concentrations; and biannual sediment elevation surveys by RTK-GPS. A suite of water quality measurements are made every 15 minutes in the main creek that floods the marsh platform in the flux footprint. Here we present our first six months of observations investigating the abiotic drivers of productivity on daily (intratidal) to monthly timescales as determined by the eddy covariance fluxes. Comparisons with other tidal marsh eddy flux observations across the eastern U.S. are presented for context. Initial results suggest our measured net ecosystem exchange may contain the strongest tidal signal reported to date, which could result from the relatively low elevation of our site.

Effect of salinity and inorganic nitrogen concentrations on nitrification and denitrification rates in intertidal sediments and rocky biofilms of the Douro River estuary, Portugal.

PubMed

Magalhães, Catarina M; Joye, Samantha B; Moreira, Rosa M; Wiebe, William J; Bordalo, Adriano A

2005-05-01

The regulatory effects of salinity and inorganic nitrogen compounds on nitrification and denitrification were studied in intertidal sandy sediments and rocky biofilms in the Douro River estuary, Portugal, over a 12-month period. Nitrification and denitrification rates were measured in slurries of field samples and enrichment experiments using the difluoromethane and the acetylene inhibition techniques, respectively. Salinity did not regulate denitrification in either environment, suggesting that halotolerant bacteria dominated the denitrifier communities. However, nitrification rates were stimulated when salinity increased from 0 to 15 practical salinity units. NO3- addition experiments revealed that NO3- availability stimulates denitrification rates in sandy sediments, but not in rocky biofilms; however, in rocky biofilms a positive and linear relationship was observed between denitrification rates and water column NO3- concentrations (r=0.92) during the monthly surveys. The N2O:N2 ratios increased rapidly when NO3- increased from 63 to 363 microM; however, results from monthly surveys showed that environmental parameters other than NO3- availability may be important in controlling the variation in N2O production via denitrification. Ammonium additions to sandy sediments stimulated nitrification rates by 35% for the 20 microM NH4+ addition, but NH4+ appeared to inhibit nitrification at high concentration addition (200 microM NH4+). In contrast, rocky biofilm nitrification was stimulated by 65% when 200 microM NH4+ was added.

Functional trait responses to sediment deposition reduce macrofauna-mediated ecosystem functioning in an estuarine mudflat

NASA Astrophysics Data System (ADS)

Mestdagh, Sebastiaan; Bagaço, Leila; Braeckman, Ulrike; Ysebaert, Tom; De Smet, Bart; Moens, Tom; Van Colen, Carl

2018-05-01

Human activities, among which dredging and land use change in river basins, are altering estuarine ecosystems. These activities may result in changes in sedimentary processes, affecting biodiversity of sediment macrofauna. As macrofauna controls sediment chemistry and fluxes of energy and matter between water column and sediment, changes in the structure of macrobenthic communities could affect the functioning of an entire ecosystem. We assessed the impact of sediment deposition on intertidal macrobenthic communities and on rates of an important ecosystem function, i.e. sediment community oxygen consumption (SCOC). An experiment was performed with undisturbed sediment samples from the Scheldt river estuary (SW Netherlands). The samples were subjected to four sedimentation regimes: one control and three with a deposited sediment layer of 1, 2 or 5 cm. Oxygen consumption was measured during incubation at ambient temperature. Luminophores applied at the surface, and a seawater-bromide mixture, served as tracers for bioturbation and bio-irrigation, respectively. After incubation, the macrofauna was extracted, identified, and counted and then classified into functional groups based on motility and sediment reworking capacity. Total macrofaunal densities dropped already under the thinnest deposits. The most affected fauna were surficial and low-motility animals, occurring at high densities in the control. Their mortality resulted in a drop in SCOC, which decreased steadily with increasing deposit thickness, while bio-irrigation and bioturbation activity showed increases in the lower sediment deposition regimes but decreases in the more extreme treatments. The initial increased activity likely counteracted the effects of the drop in low-motility, surficial fauna densities, resulting in a steady rather than sudden fall in oxygen consumption. We conclude that the functional identity in terms of motility and sediment reworking can be crucial in our understanding of the regulation of ecosystem functioning and the impact of habitat alterations such as sediment deposition.

Recent benthic foraminifera assemblages from mangrove swamp and channels of Abu Dhabi (UAE)

NASA Astrophysics Data System (ADS)

Fiorini, Flavia; Lokier, Stephen W.; Odeh, Weaam A. S. Al; Paul, Andreas; Song, Jianfeng; Freeman, Mark; Michel, Françoise

2017-04-01

Zonation of Recent mangrove environments can be defined using benthic foraminifera, however, little is known about foraminifera from mangrove environments of the Persian/Arabian Gulf. The objective of this study is to produce a detailed micropaleontological and sedimentological analysis to identify foraminiferal associations from mangrove swamps and channels located on the eastern side of Abu Dhabi Island (UAE). Detailed sediment sampling collection in mangal environments of Eastern Abu Dhabi was carried out to assess the distribution of benthic foraminifera in different sedimentary facies in the mangal and in the surrounding natural environments of the upper and lower intertidal area (mud flats and channels). A 100 m transect across a natural channel in a mangal on the eastern side of Abu Dhabi Island was sampled in detail for sedimentological and foraminiferal analysis. Forty-seven samples were collected at 2 meter intervals along the transect in a number of different sedimentary facies including; fine sediment in areas exposed during low tide and close to mangrove trees (Avicennia marina), fine sediment rich in leaf material, coarse sediment in channels, and coarse sediments with a shell lag. At each sampling location environmental parameters were recorded, including water depth, salinity, temperature and pH. Samples collected for foraminiferal analysis were stained in rose Bengal in order to identify living specimens. Samples collected on the mud flat at the margin of the channel show a living foraminiferal assemblage characterised by abundant foraminifera belonging to the genera Ammonia, Elphidium, Cribroelphidium, Triloculina, Quinqueloculina, Sigmoilinita, Spiroloculina, Peneroplis and Spirolina. Samples collected in the lower (wet) intertidal area close to Avicennia marina roots, presented a low-diversity assemblage mostly comprising small-sized opportunistic foraminifera of the genera Ammonia and Cribroelphidium along with rare Triloculina and Quinqueloculina. Samples from the upper intertidal areas (often dry) close to Avicennia marina roots and leaf material, produced an assemblage exclusively composed of small-sized opportunistic Ammonia and Cribroelphidium, together with abundant specimensof agglutinated foraminifera belonging to the genera Trochammina. The samples collected in the higher energy settings (channels) were rich in foraminiferal tests, rare living forms were found in the coarser grained facies. The more abundant genera of foraminifera in these facies were miliolids belonging to the genera Triloculina, Quinqueloculina, Sigmoilina and epiphytic larger benthic foraminifera belonging to the genera Peneroplis, Spirolina and Sorites. The distribution of Recent benthic foraminifera from the mangrove environments of the Abu Dhabi region present a powerful tool for constructing a zonation of marine coastline environments and can be employed as a modern analogue for interpreting the depositional environment of ancient coastline sediments.

77 FR 32573 - Takes of Marine Mammals Incidental to Specified Activities; Construction and Race Event...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-01

... operations, support space, media operations, hospitality services, sponsored commercial space, and...). Intertidal habitats in the Central Bay, or those that lie between low and high tides, include sandy beaches... sediment and hard substrate habitat. Soft bottom substrate ranges between soft mud with high silt and clay...

The occurrence of microplastic contamination in littoral sediments of the Persian Gulf, Iran.

PubMed

Naji, Abolfazl; Esmaili, Zinat; Mason, Sherri A; Dick Vethaak, A

2017-09-01

Microplastics (MPs; <5 mm) in aquatic environments are an emerging contaminant of concern due to their possible ecological and biological consequences. This study addresses that MP quantification and morphology to assess the abundance, distribution, and polymer types in littoral surface sediments of the Persian Gulf were performed. A two-step method, with precautions taken to avoid possible airborne contamination, was applied to extract MPs from sediments collected at five sites during low tide. MPs were found in 80% of the samples. Across all sites, fiber particles were the most dominate shape (88%), followed by films (11.2%) and fragments (0.8%). There were significant differences in MP particle concentration between sampling sites (p value <0.05). The sediments with the highest numbers of MPs were from sites in the vicinity of highly populated centers and municipal effluent discharges. FTIR analysis showed that polyethylene (PE), nylon, and polyethylene terephthalate (PET) were the most abundant polymer types. More than half of the observed MPs (56%) were in the size category of 1-4.7 mm length, with the remaining particles (44%) being in the size range of 10 μm to <1 mm. Compared to literature data from other regions, intertidal sediments in the Persian Gulf cannot be characterized as a hot spot for MP pollution. The present study could, however, provide useful background information for further investigations and management policies to understand the sources, transport, and potential effects on marine life in the Persian Gulf.

"Recent" macrofossil remains from the Lomonosov Ridge, central Arctic Ocean

NASA Astrophysics Data System (ADS)

Le Duc, Cynthia; de Vernal, Anne; Archambault, Philippe; Brice, Camille; Roberge, Philippe

2016-04-01

The examination of surface sediment samples collected from 17 sites along the Lomonosov Ridge at water depths ranging from 737 to 3339 meters during Polarstern Expedition PS87 in 2014 (Stein, 2015), indicates a rich biogenic content almost exclusively dominated by calcareous remains. Amongst biogenic remains, microfossils (planktic and benthic foraminifers, pteropods, ostracods, etc.) dominate but millimetric to centrimetric macrofossils occurred frequently at the surface of the sediment. The macrofossil remains consist of a large variety of taxa, including gastropods, bivalvia, polychaete tubes, scaphopods, echinoderm plates and spines, and fish otoliths. Among the Bivalvia, the most abundant taxa are Portlandia arctica, Hyalopecten frigidus, Cuspidaria glacilis, Policordia densicostata, Bathyarca spp., and Yoldiella spp. Whereas a few specimens are well preserved and apparently pristine, most mollusk shells displayed extensive alteration features. Moreover, most shells were covered by millimeter scale tubes of the serpulid polychaete Spirorbis sp. suggesting transport from low intertidal or subtidal zone. Both the ecological affinity and known geographic distribution of identified bivalvia as named above support the hypothesis of transportation rather than local development. In addition to mollusk shells, more than a hundred fish otoliths were recovered in surface sediments. The otoliths mostly belong to the Gadidae family. Most of them are well preserved and without serpulid tubes attached to their surface, suggesting a local/regional origin, unlike the shell remains. Although recovered at the surface, the macrofaunal assemblages of the Lomonosov Ridge do not necessarily represent the "modern" environments as they may result from reworking and because their occurrence at the surface of the sediment may also be due to winnowing of finer particles. Although the shells were not dated, we suspect that their actual ages may range from modern to several thousands of years as suggested by the radiocarbon dating of the upper centimeter of the sediment in PS87/030-2 (7792 ± 59 14C years BP), PS87/055-1 (3897 ± 41 14C years BP), and PS87/099-4 (1421 ± 66 14C years BP). Reference Stein, R. (Ed.), 2015. The Expedition PS87 of the Research Vessel Polarstern to the Arctic Ocean in 2014, Reports on Polar and Marine Research 688, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 273 pp (http://epic.awi.de/37728/1/BzPM_0688_2015.pdf).

Toxicity evaluation with the microtox® test to assess the impact of in situ oiled shoreline treatment options: natural attenuation and sediment relocation

USGS Publications Warehouse

Lee, Kenneth; Wohlgeschaffen, Gary; Tremblay, Gilles H.; Johnson, B. Thomas; Sergy, Gary A.; Prince, Roger C.; Guenette, Chantal C.; Owens, Edward H.

2003-01-01

Changes in the toxicity levels of beach sediment, nearshore water, and bottom sediment samples were monitored with the Microtox® Test to evaluate the two in situ oil spill treatment options of natural attenuation (natural recovery––no treatment) and sediment relocation (surf washing). During a series of field trials, IF-30 fuel oil was intentionally sprayed onto the surface of three mixed sediment (pebble and sand) beaches on the island of Spitsbergen, Svalbard, Norway (78°56′ N, 16°45′ E). At a low wave-energy site (Site 1 with a 3-km wind fetch), where oil was stranded within the zone of normal wave action, residual oil concentrations and beach sediment toxicity levels were significantly reduced by both options in less than five days. At Site 3, a higher wave-energy site with a 40-km wind fetch, oil was intentionally stranded on the beach face in the upper intertidal/supratidal zones, above the level of normal wave activity. At this site under these experimental conditions, sediment relocation was effective in accelerating the removal of the oil from the sediments and reducing the Microtox® Test toxicity response to background levels. In the untreated (natural attenuation) plot at this site, the fraction of residual oil remaining within the beach sediments after one year (70%) continued to generate a toxic response. Chemical and toxicological analyses of nearshore sediment and sediment-trap samples at both sites confirmed that oil and suspended mineral fines were effectively dispersed into the surrounding environment by the in situ treatments. In terms of secondary potential detrimental effects from the release of stranded oil from the beaches, the toxicity level (Microtox® Test) of adjacent nearshore sediment samples did not exceed the Canadian regulatory limit for dredged spoils destined for ocean disposal.

The effects of low-tide rainfall on metal content of suspended sediment in the Sacramento-San Joaquin Delta

NASA Astrophysics Data System (ADS)

Moskalski, S. M.; Torres, R.; Bizimis, M.; Bergamaschi, B. A.; Fleck, J.; Goni, M. A.

2012-12-01

Rain falling near low tide is capable of eroding and transporting cohesive sediment from marsh and mudflat surfaces. Given that metals adsorb strongly to silt- and clay-sized particles, it is conceivable that lowtide rainfall may also liberate previously-deposited metals from storage in intertidal sediment. To investigate the potential for rainfall as an agent of remobilization of metals, this study tested the hypothesis of sediment, and therefore metals and nutrients, mobilization during these punctuated low-tide rainfall events. Water samples were collected during low-tide rain events in winter and wind resuspension events in summer from a marsh in central California. The concentrations of suspended sediment, particulate organic carbon and nitrogen, and total adsorbed concentration (mass of metal per volume of filtered water) of most metals were higher during a low tide rainfall event than during wind-only and fair-weather events. Metal contents (mass of metal per mass of sediment) were also greater during the rain event for most metals. Principle components analysis and the relationships between total adsorbed metals and SSC suggest rainfall during low tide can mobilize a different source of sediment than the background sediment available for tidal and wind-wave resuspension. The metal content of bulk sediment samples from around the study area could not be matched satisfactorily to the suspended sediment in any of the events, implying that bulk sediment should not be used to extrapolate to suspended sediment in terms of adsorbed metal content. Some of the adsorbed metals were present during the rain event in amounts that could be toxic, depending on the actual bioavailability of the metals.; Summary plots of measured organic parameters. (A) POC (B) PN (C) C:N (D) total leachable metal concentration, sum of all measured metals. The solid line inside box is the median and the dashed line is the mean.

Nitrous oxide fluxes in estuarine environments: response to global change.

PubMed

Murray, Rachel H; Erler, Dirk V; Eyre, Bradley D

2015-09-01

Nitrous oxide is a powerful, long-lived greenhouse gas, but we know little about the role of estuarine areas in the global N2 O budget. This review summarizes 56 studies of N2 O fluxes and associated biogeochemical controlling factors in estuarine open waters, salt marshes, mangroves, and intertidal sediments. The majority of in situ N2 O production occurs as a result of sediment denitrification, although the water column contributes N2 O through nitrification in suspended particles. The most important factors controlling N2 O fluxes seem to be dissolved inorganic nitrogen (DIN) and oxygen availability, which in turn are affected by tidal cycles, groundwater inputs, and macrophyte density. The heterogeneity of coastal environments leads to a high variability in observations, but on average estuarine open water, intertidal and vegetated environments are sites of a small positive N2 O flux to the atmosphere (range 0.15-0.91; median 0.31; Tg N2 O-N yr(-1) ). Global changes in macrophyte distribution and anthropogenic nitrogen loading are expected to increase N2 O emissions from estuaries. We estimate that a doubling of current median NO3 (-) concentrations would increase the global estuary water-air N2 O flux by about 0.45 Tg N2 O-N yr(-1) or about 190%. A loss of 50% of mangrove habitat, being converted to unvegetated intertidal area, would result in a net decrease in N2 O emissions of 0.002 Tg N2 O-N yr(-1) . In contrast, conversion of 50% of salt marsh to unvegetated area would result in a net increase of 0.001 Tg N2 O-N yr(-1) . Decreased oxygen concentrations may inhibit production of N2 O by nitrification; however, sediment denitrification and the associated ratio of N2 O:N2 is expected to increase. © 2015 John Wiley & Sons Ltd.

Linking macrobenthic communities structure and zonation patterns on sandy shores: Mapping tool toward management and conservation perspectives in Northern France

NASA Astrophysics Data System (ADS)

Rolet, Céline; Spilmont, Nicolas; Dewarumez, Jean-Marie; Luczak, Christophe

2015-05-01

In a context of intensifying anthropogenic pressures on sandy shores, the mapping of benthic habitat appears as an essential first step and a fundamental baseline for marine spatial planning, ecosystem-based management and conservation efforts of soft-sediment intertidal areas. Mapping allows representing intertidal habitats that are basically characterised by abiotic (e.g sediments, exposure to waves…) and biotic factors such as macrobenthic communities. Macrobenthic communities are known to show zonation patterns across sandy beaches and many studies highlighted the existence of three biological zones. We tested this general model of a tripartite biological division of the shore at a geographical scale of policy, conservation and management decisions (i.e. Northern France coastline), using multivariate analyses combined with the Direct Field Observation (DFO) method. From the upper to the lower shores, the majority of the beaches exhibited three macrobenthic communities confirming the existence of the tripartite biological division of the shore. Nevertheless, in some cases, two or four zones were found: (1) two zones when the drying zone located on the upper shore was replaced by littoral rock or engineering constructions and (2) four zones on beaches and estuaries where a muddy-sand community occurred from the drift line to the mid shore. The correspondence between this zonation pattern of macrobenthic communities and the EUNIS habitat classification was investigated and the results were mapped to provide a reference state of intertidal soft-sediment beaches and estuaries. Our results showed evidence of the applicability of this EUNIS typology for the beaches and estuaries at a regional scale (Northern France coastline) with a macroecological approach. In order to fulfil the requirements of the European Directives (WFD and MFSD), this mapping appears as a practical tool for any functional study on these coastal ecosystems, for the monitoring of anthropogenic activities and for the implementation of management plans concerning effective conservation strategies.

Natural occurrence of microbial sulphur oxidation by long-range electron transport in the seafloor

PubMed Central

Malkin, Sairah Y; Rao, Alexandra MF; Seitaj, Dorina; Vasquez-Cardenas, Diana; Zetsche, Eva-Maria; Hidalgo-Martinez, Silvia; Boschker, Henricus TS; Meysman, Filip JR

2014-01-01

Recently, a novel mode of sulphur oxidation was described in marine sediments, in which sulphide oxidation in deeper anoxic layers was electrically coupled to oxygen reduction at the sediment surface. Subsequent experimental evidence identified that long filamentous bacteria belonging to the family Desulfobulbaceae likely mediated the electron transport across the centimetre-scale distances. Such long-range electron transfer challenges some long-held views in microbial ecology and could have profound implications for sulphur cycling in marine sediments. But, so far, this process of electrogenic sulphur oxidation has been documented only in laboratory experiments and so its imprint on the seafloor remains unknown. Here we show that the geochemical signature of electrogenic sulphur oxidation occurs in a variety of coastal sediment environments, including a salt marsh, a seasonally hypoxic basin, and a subtidal coastal mud plain. In all cases, electrogenic sulphur oxidation was detected together with an abundance of Desulfobulbaceae filaments. Complementary laboratory experiments in intertidal sands demonstrated that mechanical disturbance by bioturbating fauna destroys the electrogenic sulphur oxidation signal. A survey of published geochemical data and 16S rRNA gene sequences identified that electrogenic sulphide oxidation is likely present in a variety of marine sediments with high sulphide generation and restricted bioturbation, such as mangrove swamps, aquaculture areas, seasonally hypoxic basins, cold sulphide seeps and possibly hydrothermal vent environments. This study shows for the first time that electrogenic sulphur oxidation occurs in a wide range of marine sediments and that bioturbation may exert a dominant control on its natural distribution. PMID:24671086

Natural occurrence of microbial sulphur oxidation by long-range electron transport in the seafloor.

PubMed

Malkin, Sairah Y; Rao, Alexandra M F; Seitaj, Dorina; Vasquez-Cardenas, Diana; Zetsche, Eva-Maria; Hidalgo-Martinez, Silvia; Boschker, Henricus T S; Meysman, Filip J R

2014-09-01

Recently, a novel mode of sulphur oxidation was described in marine sediments, in which sulphide oxidation in deeper anoxic layers was electrically coupled to oxygen reduction at the sediment surface. Subsequent experimental evidence identified that long filamentous bacteria belonging to the family Desulfobulbaceae likely mediated the electron transport across the centimetre-scale distances. Such long-range electron transfer challenges some long-held views in microbial ecology and could have profound implications for sulphur cycling in marine sediments. But, so far, this process of electrogenic sulphur oxidation has been documented only in laboratory experiments and so its imprint on the seafloor remains unknown. Here we show that the geochemical signature of electrogenic sulphur oxidation occurs in a variety of coastal sediment environments, including a salt marsh, a seasonally hypoxic basin, and a subtidal coastal mud plain. In all cases, electrogenic sulphur oxidation was detected together with an abundance of Desulfobulbaceae filaments. Complementary laboratory experiments in intertidal sands demonstrated that mechanical disturbance by bioturbating fauna destroys the electrogenic sulphur oxidation signal. A survey of published geochemical data and 16S rRNA gene sequences identified that electrogenic sulphide oxidation is likely present in a variety of marine sediments with high sulphide generation and restricted bioturbation, such as mangrove swamps, aquaculture areas, seasonally hypoxic basins, cold sulphide seeps and possibly hydrothermal vent environments. This study shows for the first time that electrogenic sulphur oxidation occurs in a wide range of marine sediments and that bioturbation may exert a dominant control on its natural distribution.

Contrasting sedimentation patterns in two semi-enclosed mesotidal bays along the west and south coasts of Korea controlled by their orientation to the regional monsoon climate

NASA Astrophysics Data System (ADS)

Hong, Seok Hwi; Chun, Seung Soo; Chang, Tae Soo; Jang, Dae Geon

2017-08-01

Sedimentation patterns of tidal flats along the Korean west coast have long been known to be largely controlled by the monsoon climate. On the other hand, much less is known about the effect of the monsoon on sedimentation in coastal embayments with mouths of different geographic orientations. Good examples are Hampyeong and Yeoja bays along the west and south coasts, respectively. Both have narrow entrances, but their mouths open toward the northwest and the south, respectively. With mean tidal ranges of 3.46 and 3.2 m, respectively, the two bays experience similar tidal regimes and are hence excellent candidates to compare the effect of different exposure to the same regional monsoon climate on their respective sediment distribution patterns. The winter monsoon, in particular, is characterized by strong northwesterly winds that directly impact the west coast, but blow offshore along the south coast. For the purpose of this study, surficial sediment samples were collected from intertidal and subtidal flats of the two bays, both in summer and winter. Grain-size analyses were carried out by sieving (sand fraction) and Sedigraph (mud fraction). In the case of Yeoja Bay, the sediments consist mostly of mud (mean grain sizes of 5.4 to 8.8 phi). Seasonal changes are very subtle, the sediments being slightly coarser in summer when silt-dominated sediments are supplied by two streams to the northern parts of the bay in response to heavy rainfall. With the exception of the deeper tidal channels, Yeoja Bay is characterized by a thick mud blanket the year round, which is modulated by processes associated with the summer monsoon that predominantly blows from the east. Textural parameters suggest severely restricted sediment mixing on the subtidal and intertidal flats, the overall low energy situation preventing sands from reaching the tidal flats. The sediments of Hampyeong Bay, by contrast, are characterized by a distinct shoreward fining trend. Mean grain sizes average around -2.2 phi at the mouth and 8.2 phi near the shore of the inner bay. The textural relationships suggest progressive mixing between two hydraulic populations, the overall higher energy situation allowing sands to be transported onto the tidal flats in winter. In addition, a clear seasonal signal indicating deposition in summer and erosion in winter is observed, the latter probably being controlled by waves generated by strong northwesterly winds of the winter monsoon. The contrasting energy regimes controlling sediment distribution in the two bays are particularly well reflected in ternary diagrams of sand/silt/clay ratios and bivariate plots of textural parameters. The results clearly demonstrate that tidal sedimentation along the west coast of Korea is controlled by the more energetic winter monsoon, whereas along the south coast it is modulated by the less energetic summer monsoon. As a consequence, distinct seasonal changes are particularly pronounced along the west coast, whereas these are more subtle along the south coast. The orientation of bay mouths relative to the direction of wind associated with the summer and winter monsoon is thus identified as the main reason for the completely different sedimentation patterns observed on the subtidal and intertidal flats of the two bays.

The Relationship Between Sediment Properties and Sedimentation Patterns on a Macrotidal Gravel Beach over a Semi-lunar Tidal Cycle.

NASA Astrophysics Data System (ADS)

Buscombe, D.; Masselink, G.

2007-12-01

Detailed measurements of profile and sediment dynamics have been obtained from a macrotidal gravel barrier beach in southern England. Surface and sub-surface sediment samples, beach profiles, and disturbance depths were taken from the intertidal zone on consecutive low tides over semi-lunar tidal cycles, along with continuous wave and tide measurements. Results from two separate field surveys are presented, representing 26 and 24 consecutive low tides, respectively. A combination of Canonical Correlation Analysis (CCA) and Empirical Orthogonal Function (EOF) analysis was used to identify a number of consistent relationships in morphological and sedimentological variables not readily apparent using ordinary correlations. The disadvantage of such statistical models is that the relationships obtained cannot be expressed in physically meaningful units, which does limit its utility in physical-numerical modelling. However, the results reveal some interesting relationships between gravel beachface sedimentology and morphological change. For example, beachface morphology and sedimentology are more similar at a given spatial location over time than over space (cross-shore) at any individual time. Subsurface sedimentology over the depth of disturbance indicates that the beach step can be traced through the sediment characteristics. Indeed, the study suggests that gravel beachface sedimentology is 'slaved' to morphological change rather than vice-versa; and that the relationship becomes more evident as secondary morphological features develop on the beachface. The results imply that median sediment size and geometric sorting are suitable parameters for detecting such relationships. Strong hysteresis over space was present in the EOF modes associated with the most variance in the data sets, for both sediment size and sorting. Statistically significant relationships were found between the temporal modes of (absolute) size/sorting and net sedimentation associated with the largest variance in the non-decomposed respective data sets. Finally, significant relationships were found between a suite of measured hydrodynamic time-series and pairs of significantly correlated morpho-sedimentary eigenmodes. The techniques used were thus able to objectively demonstrate linear association between morphological and sedimentological change on a gravel beachface over a semi-lunar tidal cycle; and also that simultaneous changes in each could be linearly correlated to hydrodynamic forcing.

DOCUMENTING THE INTERTIDAL COMPONENT OF EELGRASS DISTRIBUTIONS IN PACIFIC NORTHWEST ESTUARIES USING COLOR INFRARED AERIAL PHOTOGRAPHY

EPA Science Inventory

The objective of this study was to develop and test a rapid, cost-effective method of mapping the intertidal (and surface-visible subtidal) distribution of eelgrass (Zostera marina L.) meadows and patches in the turbid coastal estuaries of the Pacific Northwest (PNW). Initial co...

From smooth to rough, from water to air: the intertidal habitat of Northern clingfish ( Gobiesox maeandricus)

NASA Astrophysics Data System (ADS)

Ditsche, Petra; Hicks, Madeline; Truong, Lisa; Linkem, Christina; Summers, Adam

2017-04-01

The Northern clingfish is a small, Eastern North Pacific fish that can attach to rough, fouled rocks in the intertidal. Their ability to attach to surfaces has been measured previously in the laboratory, and in this study, we show the roughness and fouling of the natural habitat of these fish. We introduce a new method for measuring surface roughness of natural substrates with time-limited accessibility. We expect this method to be broadly applicable in studies of animal/substrate surface interactions in habitats difficult to characterize. Our roughness measurements demonstrate that the fish's ability to attach to very coarse roughness is required in its natural environment. Some of the rocks showed even coarser roughness than the fish could attach to in the lab setting. We also characterized the clingfish's preference for other habitat descriptors such as the size of the rocks, biofilm, and Aufwuchs (macroalgae, encrusting invertebrates) cover, as well as grain size of underlying substrate. Northern clingfish seek shelter under rocks of 15-45 cm in size. These rocks have variable Aufwuchs cover, and gravel is the main underlying substrate type. In the intertidal, environmental conditions change with the tides, and for clingfish, the daily time under water (DTUW%) was a key parameter explaining distribution. Rather than location being determined by intertidal zonation, an 80% DTUW, a finer scale concept of tidal inundation, was required by the fish. We expect that this is likely because the mobility of the fish allows them to more closely track the ideal inundation in the marine intertidal.

Experimental investigation of the impact of macroalgal mats on flow dynamics and sediment stability in shallow tidal areas

NASA Astrophysics Data System (ADS)

Venier, C.; Figueiredo da Silva, J.; McLelland, S. J.; Duck, R. W.; Lanzoni, S.

2012-10-01

This study aims to quantify the impact of macroalgal mats of Ulva intestinalis on flow dynamics and sediment stability. Such mats are becoming increasingly common in many coastal and estuarine intertidal habitats, thus it is important to determine whether they increase flow resistance, promote bed stability and therefore reduce the risk of erosion leading to tidal flooding or to degradation of coastal lagoons. The study has been carried out through a systematic series of experiments conducted in the large open-channel flume of the Total Environment Simulator (TES) facility, University of Hull, UK. The experimental facility was set up with a bed of fine sand, partially covered by strands of U. intestinalis; living individuals attached to large clasts were collected from Budle Bay, in the Lindisfarne National Nature Reserve, UK, and transplanted to the flume. The TES was equipped with acoustic doppler velocimetry (ADV) and acoustic backscatter (ABS) sensors, which measured current velocity, water level, bed level, and suspended sediment concentration. The experiments consisted of several unidirectional flow runs, firstly with a mobile sediment bed covered with U. intestinalis, then with a bare sediment surface, conducted at three different water depths. Under the investigated experimental range of velocities, typical of tidal environments, the macroalgal filaments were bent parallel to the sediment bed. The resulting velocity profile departed from the classical logarithmic trend, implying an increase of the overall roughness. This result reflects the different vertical Reynolds shear stress profiles and energy spectra features of the turbulent flow with respect to a bare sandy bed configuration. Macroalgae are also found to affect the morphological configuration of bedforms. The overall result is significant bio-stabilization, with increased flow resistance and reduced sediment transport.

Description of the small plastics fragments in marine sediments along the Alang-Sosiya ship-breaking yard, India

NASA Astrophysics Data System (ADS)

Srinivasa Reddy, M.; Basha, Shaik; Adimurthy, S.; Ramachandraiah, G.

2006-07-01

This study aimed to assess the accumulation of small plastic debris in the intertidal sediments of the world's largest ship-breaking yard at Alang-Sosiya, India. Small plastics fragments were collected by flotation and separated according to their basic polymer type under a microscope, and subsequently identified by FT-IR spectroscopy as polyurethane, nylon, polystyrene, polyester and glass wool. The morphology of these materials was also studied using a scanning electron microscope. Overall, there were on average 81 mg of small plastics fragments per kg of sediment. The described plastic fragments are believed to have resulted directly from the ship-breaking activities at the site.

Indices, multispecies and synthesis descriptors in benthic assessments: Intertidal organic enrichment from oyster farming

NASA Astrophysics Data System (ADS)

Quintino, Victor; Azevedo, Ana; Magalhães, Luísa; Sampaio, Leandro; Freitas, Rosa; Rodrigues, Ana Maria; Elliott, Michael

2012-09-01

Intertidal off-bottom oyster culture is shown to cause organic enrichment of the shore and although there are two stressors of interest (the presence of a structure, the trestles, and also the sediment and organic waste from the oysters), these can be separated and their relative impacts determined using an appropriate nested experimental design and data treatments. Although no artificial food sources are involved, the oysters feeding activity and intensity of culture enhances biodeposition and significantly increases the sediment fines content and total organic matter. This in general impoverished the benthic community in culture areas rather than a species succession with the installation of opportunists or a resulting increase in the abundance and biomass of benthic species; the findings can be a direct consequence of the intertidal situation which is less-amenable recruitment of species more common to the subtidal environment. Thus the most appropriate biological descriptors to diagnose the effects associated with the organic enrichment were the multispecies abundance data as well as the primary biological variables species richness and abundance. The effects were however spatially and statistically significantly confined to the area located directly underneath the culture bags compared to the corridors located between the trestles, which do not show such enrichment effects. Synthesis biotic indices were much less effective to diagnose the benthic alterations associated with this organic enrichment. These results show that special attention must be paid when using indices in areas where the organic enrichment induces an impoverishment of the benthic community but not necessarily a species replacement with the installation of opportunists.

Influence of macrofaunal assemblages and environmental heterogeneity on microphytobenthic production in experimental systems

PubMed Central

Dyson, Kirstie E; Bulling, Mark T; Solan, Martin; Hernandez-Milian, Gema; Raffaelli, David G; White, Piran C.L; Paterson, David M

2007-01-01

Despite the complexity of natural systems, heterogeneity caused by the fragmentation of habitats has seldom been considered when investigating ecosystem processes. Empirical approaches that have included the influence of heterogeneity tend to be biased towards terrestrial habitats; yet marine systems offer opportunities by virtue of their relative ease of manipulation, rapid response times and the well-understood effects of macrofauna on sediment processes. Here, the influence of heterogeneity on microphytobenthic production in synthetic estuarine assemblages is examined. Heterogeneity was created by enriching patches of sediment with detrital algae (Enteromorpha intestinalis) to provide a source of allochthonous organic matter. A gradient of species density for four numerically dominant intertidal macrofauna (Hediste diversicolor, Hydrobia ulvae, Corophium volutator, Macoma balthica) was constructed, and microphytobenthic biomass at the sediment surface was measured. Statistical analysis using generalized least squares regression indicated that heterogeneity within our system was a significant driving factor that interacted with macrofaunal density and species identity. Microphytobenthic biomass was highest in enriched patches, suggesting that nutrients were obtained locally from the sediment–water interface and not from the water column. Our findings demonstrate that organic enrichment can cause the development of heterogeneity which influences infaunal bioturbation and consequent nutrient generation, a driver of microphytobenthic production. PMID:17698480

Origin of Amazon mudbanks along the northeastern coast of South America

USGS Publications Warehouse

Allison, M.A.; Lee, M.T.; Ogston, A.S.; Aller, R.C.

2000-01-01

Seismic profiles, sediment cores, and water column measurements were collected along the northeastern coast of Brazil to examine the origin of mudbanks in the Amazon coastal mud belt. These 10-60-km-long, shore-attached features previously had been observed to migrate along the 1200 km coast of the Guianas in response to wave forcing. CHIRP (3.5 kHz) seismic profiles of the shoreface and inner shelf located two mudbanks updrift of the previous eastern limit in French Guiana. 210Pb geochronology shows that these two banks are migrating to the northwest over a relict mud surface in 5-20 m water depth. The mudbanks are 3-4 m thick and are translating over a modern shoreface mud wedge deposited by previous mudbank passage in < 5 m water depth. Initial mudbank development is taking place on the intertidal and shallow subtidal mudflats at Cabo Cassipore, associated with an alongshore-accreting clinoform feature. Sediment trapping in this area is controlled by the nearshore presence of strong water column stratification produced by the enormous Amazon freshwater discharge on the shelf and by proximity to the Cassipore River estuary. Seasonal and decadal periods of sediment supply and starvation in this area likely are controlled by variations in northwest trade wind intensity. (C) 2000 Elsevier Science B.V.

Relationships among benthic green macroalgae, infaunal invertebrates, and dissolved sulfides in sediment pore waters, Yaquina Estuary, Oregon, USA

EPA Science Inventory

Relatively high abundances of benthic green macroalgae (Ulva spp.) have been measured in Yaquina Estuary on the central coast of the State of Oregon, USA. Band transects (30 meters in width) from the lower to the upper intertidal zone were established at two sites (Idaho Point a...

RELATIONSHIPS BETWEEN WATER AND SEDIMENT CHARACTERISTICS AND BENTHIC GREEN MACROALGAE ABUNDANCE IN YAQUINA BAY, OREGON: 1999-2000

EPA Science Inventory

"Green tides" or blooms of ulvoid green algae are frequent in Yaquina Bay Estuary on the central Oregon coast, USA. Measurements of their biomass were made from late spring to early winter in 1999 at six intertidal sites in the estuary and were continued throughout the winter of...

Benthic impacts of intertidal oyster culture, with consideration of taxonomic sufficiency.

PubMed

Forrest, Barrie M; Creese, Robert G

2006-01-01

An investigation of the impacts from elevated intertidal Pacific oyster culture in a New Zealand estuary showed enhanced sedimentation beneath culture racks compared with other sites. Seabed elevation beneath racks was generally lower than between them, suggesting that topographic patterns more likely result from a local effect of rack structures on hydrodynamic processes than from enhanced deposition. Compared with control sites, seabed sediments within the farm had a greater silt/clay and organic content, and a lower redox potential and shear strength. While a marked trend in macrofaunal species richness was not evident, species composition and dominance patterns were consistent with a disturbance gradient, with farm effects not evident 35 m from the perimeter of the racks. Of the environmental variables measured, sediment shear strength was most closely associated with the distribution and density of macrofauna, suggesting that human-induced disturbance from farming operations may have contributed to the biological patterns. To evaluate the taxonomic sufficiency needed to document impacts, aggregation to the family level based on Linnean classification was compared with an aggregation scheme based on ;general groups' identifiable with limited taxonomic expertise. Compared with species-level analyses, spatial patterns of impact were equally discernible at both aggregation levels used, provided density rather than presence/absence data were used. Once baseline conditions are established and the efficacy of taxonomic aggregation demonstrated, a ;general group' scheme provides an appropriate and increasingly relevant tool for routine monitoring.

Disturbance-mediated facilitation by an intertidal ecosystem engineer.

PubMed

Wright, Jeffrey T; Gribben, Paul E

2017-09-01

Ecosystem engineers facilitate communities by providing a structural habitat that reduces abiotic stress or predation pressure for associated species. However, disturbance may damage or move the engineer to a more stressful environment, possibly increasing the importance of facilitation for associated communities. In this study, we determined how disturbance to intertidal boulders (i.e., flipping) and the subsequent movement of a structural ecosystem engineer, the tube-forming serpulid worm Galeolaria caespitosa, from the bottom (natural state, low abiotic stress) to the top (disturbed state, high abiotic stress) surface of boulders influenced the importance of facilitation for intertidal communities across two intertidal zones. Theory predicts stronger relative facilitation should occur in the harsher environments of the top of boulders and the high intertidal zone. To test this prediction, we experimentally positioned boulders with the serpulids either face up or face down for 12 months in low and high zones in an intertidal boulder field. There were very different communities associated with the different boulders and serpulids had the strongest facilitative effects on the more stressful top surface of boulders with approximately double the species richness compared to boulders lacking serpulids. Moreover, within the serpulid matrix itself there was also approximately double the species richness (both zones) and abundance (high zone only) of small invertebrates on the top of boulders compared to the bottom. The high relative facilitation on the top of boulders reflected a large reduction in temperature by the serpulid matrix on that surface (up to 10°C) highlighting a key role for modification of the abiotic environment in determining the community-wide facilitation. This study has demonstrated that disturbance and subsequent movement of an ecosystem engineer to a more stressful environment increased the importance of facilitation and allowed species to persist that would otherwise be unable to survive in that environment. © 2017 by the Ecological Society of America.

Increasing sea surface temperature and range shifts of intertidal gastropods along the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Rubal, Marcos; Veiga, Puri; Cacabelos, Eva; Moreira, Juan; Sousa-Pinto, Isabel

2013-03-01

There are well-documented changes in abundance and geographical range of intertidal invertebrates related to climate change at north Europe. However, the effect of sea surface warming on intertidal invertebrates has been poorly studied at lower latitudes. Here we analyze potential changes in the abundance patterns and distribution range of rocky intertidal gastropods related to climate change along the Iberian Peninsula. To achieve this aim, the spatial distribution and range of sub-tropical, warm- and cold-water species of intertidal gastropods was explored by a fully hierarchical sampling design considering four different spatial scales, i.e. from region (100 s of km apart) to quadrats (ms apart). Variability on their patterns of abundance was explored by analysis of variance, changes on their distribution ranges were detected by comparing with previous records and their relationship with sea water temperature was explored by rank correlation analyses. Mean values of sea surface temperature along the Iberian coast, between 1949 and 2010, were obtained from in situ data compiled for three different grid squares: south Portugal, north Portugal, and Galicia. Lusitanian species did not show significant correlation with sea water temperature or changes on their distributional range or abundance, along the temperature gradient considered. The sub-tropical species Siphonaria pectinata has, however, increased its distribution range while boreal cold-water species showed the opposite pattern. The latter was more evident for Littorina littorea that was almost absent from the studied rocky shores of the Iberian Peninsula. Sub-tropical and boreal species showed significant but opposite correlation with sea water temperature. We hypothesized that the energetic cost of frequent exposures to sub-lethal temperatures might be responsible for these shifts. Therefore, intertidal gastropods at the Atlantic Iberian Peninsula coast are responding to the effect of global warming as it is happening at higher latitudes. However, the identity of the species showing changes in their range of distribution was different.

The morphological development of newly inundated intertidal areas: the mechanisms driving the early evolution of an estuarine environment designed and constructed by humans

NASA Astrophysics Data System (ADS)

Dale, Jonathan; Burgess, Heidi; Cundy, Andrew

2017-04-01

Intertidal saltmarsh and mudflat habitats are of global importance due to the ecosystem, economic and cultural services they provide. These services include wildlife habitat provision and species diversity, immobilisation of pollutants and protection from coastal flooding. Saltmarsh and mudflat environments are, however, being lost and degraded due to erosion caused by rising sea levels and increased storminess. These losses are exacerbated by anthropogenic influences including land reclamation, increased coastal development and the construction of coastal flood defences which prevent the landwards migration of saltmarsh and mudflat environments, resulting in coastal squeeze. To compensate for saltmarsh and mudflat losses areas of the coastal hinterland are being inundated by breaching defences and constructing new defences inland, thus extending or constructing new estuarine environments; a processes known as de-embankment or managed realignment. Morphological engineering and landscaping within managed realignment sites prior to site inundation varies depending on the aims of the scheme. However, there is a shortage of data on the morphological evolution within these sites post site inundation impeding the ability of coastal engineers to effectively design and construct future sites. To date there has been a focus on the colonisation of marine macro fauna and flora within newly inundated managed realignment sites, which can be relatively rapid and easily quantified. Little is known of the morphological evolution in response to altered sedimentary processes, its driving mechanisms and therefore the success and ecological sustainability of these sites. This study evaluates the post-inundation morphological development of the largest open coast managed realignment site in Europe, at Medmerry on the south coast of the United Kingdom. Inundated in September 2013, the Medmerry Managed Realignment Site consists of a mosaic of former agricultural land and areas of lower elevation excavated during site construction, drained by a series of natural and engineered channels. Results indicate different rates and patterns of sedimentation and resulting morphology across the site. Near the breach continuous sedimentation of > 15cm over a 1 year period was measured, compared to rhythmic periods of accretion and erosion inland. These variations have been related to site design, former land-use and different sediment sources. The evolution of developing creek networks, formed by pluvial action and sediment "piping", are controlled by unconformities found in the sub-surface sediment related to Holocene site evolution. Analysis of the sedimentary processes and subsequent morphological development of these areas provides a new insight into coastal and estuarine evolution in an anthropogenically designed and constructed estuarine environment.

Effects of laughing gull and shorebird predation on the intertidal fauna at Cape May, New Jersey

NASA Astrophysics Data System (ADS)

Botton, M. L.

1984-02-01

The intertidal flats of the Cape May, New Jersey shore of Delaware Bay are populated by large numbers of laughing gulls and migrating shorebirds during the spring and early summer. Exclusion of birds from a shallow slough and a sand bar had only minor effects on the infaunal benthic invertebrate assemblage at either site. The Cape May beaches provide a rich source of food in the form of horseshoe crab ( Limulus polyphemus) eggs; foraging on this item may be more profitable than probing the sediment for infauna. Gemma gemma, a small, thick-shelled bivalve, composed over 98% of the benthic infauna at both sites in 1980, and this species may be resistant to predation by certain shorebirds, as suggested by Schneider (1978).

Analyze of waves dynamic over an intertidal mudflat of a sandy-gravely estuarine beach - Field survey and preliminary modeling approach

NASA Astrophysics Data System (ADS)

Morio, Olivier; Sedrati, Mouncef; Goubert, Evelyne

2014-05-01

As well as marine submersion or erosive phenomena, clay-silted sediment in-filling on estuarial and bay beaches are a main issue in these human-attractive areas. Coupled sandy/gravely and clay/silty intertidal areas can be observed in these particular coastal areas, depending of rivers characteristic (discharge of particle, water flow), ocean dynamics (wave exposure, current) and sediments sources. All around the world, sandy/gravely beaches are exposed to punctual or continuous input clay sediments. Vilaine estuary, Bay of Arcachon and Bay of Seine in France, Plymouth Bay in UK and also Wadden Sea in Deutschland are few examples of muddy/sandy coupled or mixed system. The beach of Bétahon (Ambon town, Brittany - France) is located on the external Vilaine estuary and is an example of this issue. This meso-macrotidal intermediate (low tide terrace) beach presents heterogeneous sediments. The upper intertidal zone is composed by sand and gravel and characterized by a steep slope. A very gentle slope characterized the lower part of the beach and is constituted by silt and clay. Clay/sand limit is characterized by a decimetric erosion cliff of mudflat along the beach. In order to understand bed variations and sediment transport of this complex heterogeneous beach, a well understanding of wave dynamic across the beach is necessary. This study focus on wave dynamics over the beach, using field observations and MIKE 21 3D wave numerical model. This paper is a preliminary approach of an upcoming global understanding of this estuarial beach behavior. Swell from deep-sea to near-shore area is modeled over a 100 km² area and real wind, deep sea wave characteristic, river water flow and tidal level are defined as open boundary conditions for the regional model. This last one is based on multiple bathymetric surveys over the last 50 years. Local model, triangular mesh gridded to 5 meters, covering Bétahon beach , is based on topographic and photographic survey of the mudflat since 2005 (an amplitude above 1.4 meters has been observed over a start reference state). Modeling significant wave height, wave direction and period are compared to a cross-shore wave dynamics survey over the beach, during one week. Surf zone positions over the beach, wave characteristics at local and regional scales, impacts of mudflat altitude on waves are analyzed and discussed.

Plant-Sediment Interactions in Salt Marshes - An Optode Imaging Study of O2, pH, and CO 2 Gradients in the Rhizosphere.

PubMed

Koop-Jakobsen, Ketil; Mueller, Peter; Meier, Robert J; Liebsch, Gregor; Jensen, Kai

2018-01-01

In many wetland plants, belowground transport of O 2 via aerenchyma tissue and subsequent O 2 loss across root surfaces generates small oxic root zones at depth in the rhizosphere with important consequences for carbon and nutrient cycling. This study demonstrates how roots of the intertidal salt-marsh plant Spartina anglica affect not only O 2 , but also pH and CO 2 dynamics, resulting in distinct gradients of O 2 , pH, and CO 2 in the rhizosphere. A novel planar optode system (VisiSens TD ® , PreSens GmbH) was used for taking high-resolution 2D-images of the O 2 , pH, and CO 2 distribution around roots during alternating light-dark cycles. Belowground sediment oxygenation was detected in the immediate vicinity of the roots, resulting in oxic root zones with a 1.7 mm radius from the root surface. CO 2 accumulated around the roots, reaching a concentration up to threefold higher than the background concentration, and generally affected a larger area within a radius of 12.6 mm from the root surface. This contributed to a lowering of pH by 0.6 units around the roots. The O 2 , pH, and CO 2 distribution was recorded on the same individual roots over diurnal light cycles in order to investigate the interlinkage between sediment oxygenation and CO 2 and pH patterns. In the rhizosphere, oxic root zones showed higher oxygen concentrations during illumination of the aboveground biomass. In darkness, intraspecific differences were observed, where some plants maintained oxic root zones in darkness, while others did not. However, the temporal variation in sediment oxygenation was not reflected in the temporal variations of pH and CO 2 around the roots, which were unaffected by changing light conditions at all times. This demonstrates that plant-mediated sediment oxygenation fueling microbial decomposition and chemical oxidation has limited impact on the dynamics of pH and CO 2 in S. anglica rhizospheres, which may in turn be controlled by other processes such as root respiration and root exudation.

Disappointment Reach, Australia as seen from STS-67 Endeavour

NASA Technical Reports Server (NTRS)

1995-01-01

A nearly vertical view of Disappointment Reach and surroundings. Ripple-like patterns extending at right angles to the tidal flow can be discerned on shoals. Relict sand dune patterns, crests unvegetated, are evident on the western side of the estuary. Red mud brought down the Mooramel River on the east side of the estuary does extend into the shallow water of the inter-tidal lagoons. Most of the light-colored water along the coast, represents shoals of lime sediment. Patterns of sediment distribution by tides, waves, streams, and wind combine to create a complex and colorful scene.

Disappointment Reach, Australia as seen from STS-67 Endeavour

NASA Image and Video Library

1995-03-14

A nearly vertical view of Disappointment Reach and surroundings. Ripple-like patterns extending at right angles to the tidal flow can be discerned on shoals. Relict sand dune patterns, crests unvegetated, are evident on the western side of the estuary. Red mud brought down the Mooramel River on the east side of the estuary does extend into the shallow water of the inter-tidal lagoons. Most of the light-colored water along the coast, represents shoals of lime sediment. Patterns of sediment distribution by tides, waves, streams, and wind combine to create a complex and colorful scene.

INTERTIDAL SEDIMENT TEMPERATURE VARIANCE AS A POSSIBLE LIMITING FACTOR FOR EELGRASSES ZOSTERA MARINA AND ZOSTERA JAPONICA IN YAQUINA BAY, OR

EPA Science Inventory

The eelgrass species Zostera marina and Z. japonica co-occur in most Pacific Northwest estuaries; Z. marina is regarded as a native species, Z. japonica as non-indigenous, introduced in Yaquina Bay in approximately 1975. The mean tidal range is ~2 m, extreme ~3m. The vertical d...

Ecosystem engineering by seagrasses interacts with grazing to shape an intertidal landscape.

PubMed

van der Heide, Tjisse; Eklöf, Johan S; van Nes, Egbert H; van der Zee, Els M; Donadi, Serena; Weerman, Ellen J; Olff, Han; Eriksson, Britas Klemens

2012-01-01

Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic environment) and consumer-resource interactions are both major determinants of spatial patchiness in ecosystems. However, interactive effects of these two mechanisms on spatial complexity have not been extensively studied. We investigated the mechanisms underlying a spatial mosaic of low-tide exposed hummocks and waterlogged hollows on an intertidal mudflat in the Wadden Sea dominated by the seagrass Zostera noltii. A combination of field measurements, an experiment and a spatially explicit model indicated that the mosaic resulted from localized sediment accretion by seagrass followed by selective waterfowl grazing. Hollows were bare in winter, but were rapidly colonized by seagrass during the growth season. Colonized hollows were heavily grazed by brent geese and widgeon in autumn, converting these patches to a bare state again and disrupting sediment accretion by seagrass. In contrast, hummocks were covered by seagrass throughout the year and were rarely grazed, most likely because the waterfowl were not able to employ their preferred but water requiring feeding strategy ('dabbling') here. Our study exemplifies that interactions between ecosystem engineering by a foundation species (seagrass) and consumption (waterfowl grazing) can increase spatial complexity at the landscape level.

On inter-tidal transport equation

USGS Publications Warehouse

Cheng, Ralph T.; Feng, Shizuo; Pangen, Xi

1989-01-01

The transports of solutes, sediments, nutrients, and other tracers are fundamental to the interactive physical, chemical, and biological processes in estuaries. The characteristic time scales for most estuarine biological and chemical processes are on the order of several tidal cycles or longer. To address the long-term transport mechanism meaningfully, the formulation of an inter-tidal conservation equation is the main subject of this paper. The commonly used inter-tidal conservation equation takes the form of a convection-dispersion equation in which the convection is represented by the Eulerian residual current, and the dispersion terms are due to the introduction of a Fickian hypothesis, unfortunately, the physical significance of this equation is not clear, and the introduction of a Fickian hypothesis is at best an ad hoc approximation. Some recent research results on the Lagrangian residual current suggest that the long-term transport problem is more closely related to the Lagrangian residual current than to the Eulerian residual current. With the aid of additional insight of residual current, the inter-tidal transport equation has been reformulated in this paper using a small perturbation method for a weakly nonlinear tidal system. When tidal flows can be represented by an M2 system, the new intertidal transport equation also takes the form of a convective-dispersion equation without the introduction of a Fickian hypothesis. The convective velocity turns out to be the first order Lagrangian residual current (the sum of the Eulerian residual current and the Stokes’ drift), and the correlation terms take the form of convection with the Stokes’ drift as the convective velocity. The remaining dispersion terms are perturbations of lower order solution to higher order solutions due to shear effect and turbulent mixing.

Variations in phytodetritus derived carbon uptake of the intertidal foraminifera Ammonia tepida and Haynesina germanica

NASA Astrophysics Data System (ADS)

Wukovits, Julia; Bukenberger, Patrick; Enge, Annekatrin; Wanek, Wolfgang; Watzka, Margarete; Heinz, Petra

2016-04-01

Phytodetritus represents a major component of particulate organic carbon in intertidal mudflats. Estuaries and tidal currents yield an extensive amount of these particles that display a substantial nutrient source for littoral food webs. For benthic foraminifera, a group of marine protists, phytodetritus serves as the main food source. Foraminifera are considered to play a significant role in marine carbon turnover processes and show seasonally very high population densities in intertidal sediments. Therefore, it is important to gather explicit data about the specific carbon uptake behavior of intertidal foraminiferal species. In this study, laboratory feeding experiments were carried out to observe phytodetrital carbon uptake of foraminiferal specimen collected in the German Wadden Sea. Artificially produced phytodetritus was labelled with 13C to follow carbon ingestion into foraminiferal cytoplasm over time at different simulated conditions. The experiments were performed with monocultures under exclusion of other meiofauna. Chlorophyte detritus (Dunaliella tertiolecta) was fed to the two common species Ammonia tepida and Haynesina germanica. Ammonia tepida showed a significantly higher affinity to this food source than H. germanica. Testing the effect of temperature revealed a significant decrease of carbon ingestion with increasing temperature in H. germanica. Observations focusing on A. tepida showed a rising phytodetrital carbon content in the biomass of juvenile individuals in contrast to adult foraminifera. In general, carbon uptake reaches saturation levels a few hours after food supply. Furthermore, A. tepida benefits from constant availability of fresh food rather than from a high amount of phytodetritus derived from a single food pulse. Our investigations showed that the foraminiferal impact on intertidal processing of phytodetrital carbon sources is species specific, temperature related and depends on developmental stage and input dynamics. Additionally, the presented data reveal the quantitative level of food derived carbon gathered within foraminiferal biomass.

A mega-nourishment creates novel habitat for intertidal macroinvertebrates by enhancing habitat relief of the sandy beach

NASA Astrophysics Data System (ADS)

van Egmond, E. M.; van Bodegom, P. M.; Berg, M. P.; Wijsman, J. W. M.; Leewis, L.; Janssen, G. M.; Aerts, R.

2018-07-01

Globally, sandy beaches are subject to coastal squeeze due to erosion. Soft-sediment strategies, such as sand nourishment, are increasingly applied to mitigate effects of erosion, but have long-term negative impacts on beach flora and fauna. As a more ecologically and sustainable alternative to regular beach nourishments, a mega-nourishment has been constructed along the Dutch coast by depositing 21.5 Mm3 of sand, from which sand is gradually redistributed along the coast by natural physical processes. The 'Sand Motor' mega-nourishment was constructed as a long-term management alternative for coastal protection and is the first large-scale experiment of its kind. We evaluated the development of intertidal macroinvertebrate communities in relation to this mega-nourishment, and compared it to species composition of beaches subject to regular beach or no nourishment. We found that a mega-nourishment resulted initially in a higher macroinvertebrate richness, but a lower macroinvertebrate abundance, compared to regular beach nourishment. As there was no effect of year after nourishment, this finding suggests that colonization and/or local extinction were not limiting macroinvertebrate richness at the mega-nourishment. In addition, a mega-nourishment does not converge to an intertidal macroinvertebrate community similar to those on unnourished beaches within a time scale of four years. Beach areas at the mega-nourishment sheltered from waves harbored a distinct macroinvertebrate community compared to typical wave-exposed sandy beach communities. Thus, a mega-nourishment temporally creates new habitat for intertidal macroinvertebrates by enhancing habitat relief of the sandy beach. We conclude that a mega-nourishment may be a promising coastal defense strategy for sandy shores in terms of the macroinvertebrate community of the intertidal beach.

Detection of terrigenous and marine organic matter flow into a eutrophic semi-enclosed bay by δ13C and δ15N of intertidal macrobenthos and basal food sources.

PubMed

Arbi, Iman; Liu, Songlin; Zhang, Jingping; Wu, Yunchao; Huang, Xiaoping

2018-02-01

The pathways of terrigenous and marine organic matter originating into Daya Bay intertidal habitats were investigated using carbon and nitrogen stable isotope analyses. Spatiotemporal (sites, seasons and tidal levels) variations in isotopic ratios of basal food sources and macrobenthic consumers, and also the contribution of sources to the diet of representative species and the whole macrobenthic biomass were estimated using Isosource mixing model. Results showed the anthropogenic impacts on benthic and pelagic organic matter as well as macrobenthos, depending on the spatial and temporal scales. Macrobenthic trophic structure was affected by mariculture and nuclear power plants in the dry season (winter), and the allochthonous sources i.e. industrial and urban sewage in flood season (summer). Microphytobenthos dominated the sediment organic matter pool and macrobenthic diet, while the trophic importance of mangrove leaf litter for intertidal macrobenthic communities was low. However, mangroves showed their indirect effects on the variations in macrobenthic trophic function across tidal levels. The isotopic ratios of benthic food sources and common taxa varied significantly among the tidal levels of the mangrove-lined ecosystem. In addition, pooling the macrobenthic taxa based on their feeding guild and also biomass confirmed the causes and effects for variations in organic matter composition and flow indicated by representative species in the study area. Therefore, using feeding guild and biomass as the indicators of the macrobenthic trophic function is suggested as well as the tidal level spatial scale in the heterogeneous intertidal ecosystems for data analyses and sampling design of intertidal macrobenthic food web modeling. Copyright © 2017 Elsevier B.V. All rights reserved.

Temporal variability of exchange between groundwater and surface water based on high-frequency direct measurements of seepage at the sediment-water interface

USGS Publications Warehouse

Rosenberry, Donald O.; Sheibley, Rich W.; Cox, Stephen E.; Simonds, Frederic W.; Naftz, David L.

2013-01-01

Seepage at the sediment-water interface in several lakes, a large river, and an estuary exhibits substantial temporal variability when measured with temporal resolution of 1 min or less. Already substantial seepage rates changed by 7% and 16% in response to relatively small rain events at two lakes in the northeastern USA, but did not change in response to two larger rain events at a lake in Minnesota. However, seepage at that same Minnesota lake changed by 10% each day in response to withdrawals from evapotranspiration. Seepage increased by more than an order of magnitude when a seiche occurred in the Great Salt Lake, Utah. Near the head of a fjord in Puget Sound, Washington, seepage in the intertidal zone varied greatly from −115 to +217 cm d−1 in response to advancing and retreating tides when the time-averaged seepage was upward at +43 cm d−1. At all locations, seepage variability increased by one to several orders of magnitude in response to wind and associated waves. Net seepage remained unchanged by wind unless wind also induced a lake seiche. These examples from sites distributed across a broad geographic region indicate that temporal variability in seepage in response to common hydrological events is much larger than previously realized. At most locations, seepage responded within minutes to changes in surface-water stage and within minutes to hours to groundwater recharge associated with rainfall. Likely implications of this dynamism include effects on water residence time, geochemical transformations, and ecological conditions at and near the sediment-water interface.

Detecting Subtle Shifts in Ecosystem Functioning in a Dynamic Estuarine Environment

PubMed Central

Pratt, Daniel R.; Lohrer, Andrew M.; Thrush, Simon F.; Hewitt, Judi E.; Townsend, Michael; Cartner, Katie; Pilditch, Conrad A.; Harris, Rachel J.; van Colen, Carl; Rodil, Iván F.

2015-01-01

Identifying the effects of stressors before they impact ecosystem functioning can be challenging in dynamic, heterogeneous ‘real-world’ ecosystems. In aquatic systems, for example, reductions in water clarity can limit the light available for photosynthesis, with knock-on consequences for secondary consumers, though in naturally turbid wave-swept estuaries, detecting the effects of elevated turbidity can be difficult. The objective of this study was to investigate the effects of shading on ecosystem functions mediated by sandflat primary producers (microphytobenthos) and deep-dwelling surface-feeding macrofauna (Macomona liliana; Bivalvia, Veneroida, Tellinidae). Shade cloths (which reduced incident light intensity by ~80%) were deployed on an exposed, intertidal sandflat to experimentally stress the microphytobenthic community associated with the sediment surface. After 13 weeks, sediment properties, macrofauna and fluxes of oxygen and inorganic nutrients across the sediment-water interface were measured. A multivariate metric of ecosystem function (MF) was generated by combining flux-based response variables, and distance-based linear models were used to determine shifts in the drivers of ecosystem function between non-shaded and shaded plots. No significant differences in MF or in the constituent ecosystem function variables were detected between the shaded and non-shaded plots. However, shading reduced the total explained variation in MF (from 64% in non-shaded plots to 15% in shaded plots) and affected the relative influence of M. liliana and other explanatory variables on MF. This suggests that although shade stress may shift the drivers of ecosystem functioning (consistent with earlier investigations of shading effects on sandflat interaction networks), ecosystem functions appear to have a degree of resilience to those changes. PMID:26214854

Response of Muddy Sediments and Benthic Diatom-based Biofilms to Repeated Erosion Events

NASA Astrophysics Data System (ADS)

Valentine, K.; Mariotti, G.; Fagherazzi, S.

2016-02-01

Benthic biofilms, microbes aggregated within a matrix of Extracellular Polymeric Substances (EPS), are commonly found in shallow coastal areas and intertidal environments. Biofilms have the potential to stabilize sediments, hence reducing erosion and possibly mitigating land loss. The purpose of this study is to determine how repeated flow events that rework the bed affect biofilm growth and its ability to stabilize cohesive sediments. Natural mud devoid of grazers was used to create placed beds in four annular flumes; biofilms were allowed to grow on the sediment surface. Each flume was eroded at different time intervals (1 or 12 days) to allow for varied levels of biofilm growth and adjustment following erosion. In addition, experiments with abiotic mud were performed by adding bleach to the tank. Each erosion test consisted of step-wise increases in flow that were used to measured erodibility. In the experiments where the bed was eroded every day both the abiotic and biotic flumes exhibited a decrease in erodibility with time, likely due to consolidation, but the decrease in erodibility was greater in the flume with a biofilm. Specifically the presence of biofilm reduced bed erosion at low shear stresses ( 0.1 Pa). We attribute this progressive decrease in erodibility to the accumulation of EPS over time: even though the biofilm was eroded during each erosion event, the EPS was retained within the flume, mixed with the eroded sediment and eventually settled. Less frequent erosion allowed the growth of a stronger biofilm that decreased bed erosion at higher shear stresses ( 0.4 Pa). We conclude that the time between destructive flow events influences the ability of biofilms to stabilize sediments. This influence will likely be affected by biofilm growth conditions such as light, temperature, nutrients, salinity, and the microbial community.

Impact of boat generated waves over an estuarine intertidal zone of the Seine estuary (France)

NASA Astrophysics Data System (ADS)

Deloffre, Julien; Lafite, Robert

2015-04-01

Water movements in macrotidal estuaries are controlled by the tidal regime modulated seasonally by the fluvial discharge. Wind effect on hydrodynamics and sediment transport is also reported at the mouth. Besides estuaries are frequently man altered our knowledge on the human impact on hydrodynamics and sediment transport is less extended. As an example on the Seine estuary (France) port authorities have put emphasis on facilitating economic exchanges by means of embankment building and increased dredging activity over the last century. These developments led to secure sea vessel traffic in the Seine estuary but they also resulted in a change of estuarine hydrodynamics and sediment transport features. Consequences of boat generated waves are varied: increased water turbidity and sediment transfer, release of nutrient and contaminants in the water column, harmful to users, ecosystems and infrastructures generating important maintenance spending. The aim of this study is to analyse the impact of boat generated waves on sediment transport over an intertidal area. The studied site is located on the left bank in the fluvial part of the Seine estuary. On this site the maximum tidal range ranges between 1.25 and 3.5m respectively during neap and spring tide. The sampling strategy is based on continuous ADV acquisition at 4Hz coupled with turbidimeter and altimeter measurements (1 measurement every minute) in order to decipher sediment dynamics during one year. Our results indicate that sediment dynamics are controlled by river flow while medium term scale evolution is dependent on tidal range and short term dynamics on sea-vessels waves. 64% of boat passages generated significant sediment reworking (from few mm.min-1 to 3cm.min-1). This reworking rate is mainly controlled by two parameters: (i) water height on the site and (ii) vessels characteristics; in particular the distance between seabed and keel that generate a Bernoulli wave (with maximum amplitude of 0.6m). Simultaneous hydrodynamics and bed elevation measurements permit to quantify the impact of the boat generated wave. Measurements demonstrate that the sediment transport occurs during the Bernoulli wave (few mm up to 8cm). This mechanism induces mainly a long-shore transfer of particles over the interdal area. This study proves that the sediment transport generated by boat waves cannot be neglected in the Seine estuary case.

Latest Holocene evolution and human disturbance of a channel segment in the Hudson River Estuary

USGS Publications Warehouse

Klingbeil, A.D.; Sommerfield, C.K.

2005-01-01

The latest Holocene sedimentary record of a cohesive channel and subtidal shoal in the lower Hudson River Estuary was examined to elucidate natural (sea-level rise, sediment transport) and anthropogenic (bulkheading, dredging) influences on the recent morphodynamic evolution of the system. To characterize the seafloor and shallow subbottom, ??? 100 km of high-resolution seismic reflection profiles (chirp) were collected within a 20-km reach of the estuary and correlated with sediment lithologies provided by eight vibracores recovered along seismic lines. Sediment geochronology with 137Cs and 14C was used to estimate intermediate and long-term sedimentation rates, respectively, and historical bathymetric data were analyzed to identify regional patterns of accretion and erosion, and to quantify changes in channel geometry and sediment volume. The shoal lithosome originated around 4 ka presumably with decelerating eustatic sea level rise during the latest Holocene. Long-term sedimentation rates on the shoal (2.3-2.6 mm/yr) are higher than in the channel (2 mm/yr) owing to hydrodynamic conditions that preferentially sequester suspended sediment on the western side of the estuary. As a result, the shoal accretes oblique to the principal axis of tidal transport, and more rapidly than the channel to produce an asymmetric cross-section. Shoal deposits consist of tidally bedded muds and are stratified by minor erosion surfaces that seismic profiles reveal to extend for 10s of meters to kilometers. The frequency and continuity of these surfaces suggest that the surficial shoal is catastrophically stripped on decadal-centennial time scales by elevated tidal flows; tidal erosion maintains the shoal at a uniform depth below sea level and prevents it from transitioning to an intertidal environment. Consequently, the long-term sedimentation rate approximates the rate of sea-level rise in the lower estuary (1-3 mm/yr). After the mid 1800s, the natural geometry of the lower Hudson River Estuary changed rapidly in response to engineering works that forced the channel to self-deepen. Analysis of historical bathymetric data indicates that the channel lost an estimated 3 ?? 106 tons of sediment between ca. 1939 and 2002 (50,000 tons/yr average) by subaqueous erosion, increasing in depth by as much as 4 m in places. Erosion appears to have been concurrent with systematic bulkheading of the shoreline after ca. 1865, which decreased the estuary surface area by ??? 19% overall. Evidently, self-deepening of the channel is a morphodynamic adjustment to reestablish equilibrium cross-sectional area, yet the state of this change locally and elsewhere in the estuary is unknown. Subaqueous erosion documented in this study is a significant source of sediment with implications to the sediment budget and environmental quality of the Hudson River Estuary. ?? 2005 Elsevier B.V. All rights reserved.

Community composition and activity of anaerobic ammonium oxidation bacteria in the rhizosphere of salt-marsh grass Spartina alterniflora.

PubMed

Zheng, Yanling; Hou, Lijun; Liu, Min; Yin, Guoyu; Gao, Juan; Jiang, Xiaofen; Lin, Xianbiao; Li, Xiaofei; Yu, Chendi; Wang, Rong

2016-09-01

Anaerobic ammonium oxidation (anammox) as an important nitrogen removal pathway has been investigated in intertidal marshes. However, the rhizosphere-driven anammox process in these ecosystems is largely overlooked so far. In this study, the community dynamics and activities of anammox bacteria in the rhizosphere and non-rhizosphere sediments of salt-marsh grass Spartina alterniflora (a widely distributed plant in estuaries and intertidal ecosystems) were investigated using clone library analysis, quantitative PCR assay, and isotope-tracing technique. Phylogenetic analysis showed that anammox bacterial diversity was higher in the non-rhizosphere sediments (Scalindua and Kuenenia) compared with the rhizosphere zone (only Scalindua genus). Higher abundance of anammox bacteria was detected in the rhizosphere (6.46 × 10(6)-1.56 × 10(7) copies g(-1)), which was about 1.5-fold higher in comparison with that in the non-rhizosphere zone (4.22 × 10(6)-1.12 × 10(7) copies g(-1)). Nitrogen isotope-tracing experiments indicated that the anammox process in the rhizosphere contributed to 12-14 % N2 generation with rates of 0.43-1.58 nmol N g(-1) h(-1), while anammox activity in the non-rhizosphere zone contributed to only 4-7 % N2 production with significantly lower activities (0.28-0.83 nmol N g(-1) h(-1)). Overall, we propose that the rhizosphere microenvironment in intertidal marshes might provide a favorable niche for anammox bacteria and thus plays an important role in nitrogen cycling.

Impact of intertidal oyster trestle cultivation on the Ecological Status of benthic habitats.

PubMed

Forde, James; O'Beirn, Francis X; O'Carroll, Jack Pj; Patterson, Adrian; Kennedy, Robert

2015-06-15

A considerable number of Ireland's shellfish production areas co-occur with or are adjacent to Natura 2000 sites which are protected under European legislation. To investigate the general interaction between trestle oyster cultivation and the surrounding intertidal environment, six sites were selected within designated Natura 2000 sites. At each trestle site three Treatment areas were sampled. One Treatment area corresponded to potential impacts associated with cultivation activities occurring at trestle structures (designated the Trestle Treatment) while one Treatment area corresponded to potential impacts due to cultivation activities occurring along access routes (the Access Treatment). An area not subject to any known anthropogenic activity was used as a control (the Control Treatment). Potential impacts associated with Trestle Treatment areas included changes in sediment total organic matter (TOM) levels underneath trestles due to the bio-deposition of faecal/pseudofaecal material while the predominant impact associated with Access Treatment areas was compaction of sediments due to heavy vehicle traffic. In this study, macrobenthic communities at the sites were highly variable and exhibited low levels of diversity which prevented the detection of general effects of cultivation activity on community structure, diversity and secondary production. To overcome this variability, the Infaunal Quality Index (IQI) was used to assess impacts on Ecological Status (ES) of benthic communities (sensu Water Framework Directive). Relative to Control and Trestle Treatment areas, activities occurring at Access Treatment areas had a significant negative impact on ES. This study highlights the potential of the IQI for the management of aquaculture activity and provides validation for the use of the IQI in Irish intertidal environments. This study also highlights the IQI as a potential tool for assessing the conservation status of designated habitats in Natura 2000 sites. Copyright © 2015 Elsevier Ltd. All rights reserved.

Diverse metal reduction and nano- mineral formation by metal-reducing bacteria enriched from inter-tidal flat sediments

NASA Astrophysics Data System (ADS)

Kim, Y.; Park, B.; Seo, H.; Roh, Y.

2009-12-01

Dissimilatory metal-reducing bacteria utilize diverse metal oxides as electron acceptors and couple this microbial metal reduciton to growth. However, the microbe-metal interactions playing important roles in the metal geochemistry and organic matter degradation in the tidal flat sediments have not been uncovered enough to employ in various environmental and industrial applications. The objective of this study was to examine biomineralization and bioremediation by the facultative metal-reducing bacteria isolated from the inter-tidal flat sediments in southwestern of Korea. 16S-rRNA analysis showed bacterial consortium mainly consists of genus of Clostridium sp. The enriched bacteria were capable of reducing diverse metals such as iron oxide, maganese oxide, Cr(VI) and Se(VI) during glucose fermentation process at room temperature. The bacteria reduced highly toxic and reactive elements such as Cr(VI) and Se(VI) to Cr(III) and Se(0). The results showed that microbial processes induced transformation from toxic states of heavy metals to less toxic and mobile states in natural environments. Andthe bacteria also reduced iron oxyhydroxide such as ferrihydrite and akaganeite (β-FeOOH) and formed nanometer-sized magnetite (Fe3O4). This study indicates microbial processes not only can be used for bioremediation of inorganic contaminants existing in the marine environments, but also form the magnetite nanoparticles which are exhibit superparamagnetic properties that can be useful for relevant medical and industrial applications.

Finescale turbulence and seabed scouring around pneumatophores in a wave-exposed mangrove forest

NASA Astrophysics Data System (ADS)

Mullarney, J. C.; Norris, B. K.; Henderson, S. M.; Bryan, K. R.

2015-12-01

Coastal mangroves provide a barrier between the coast and lower energy intertidal environments. The presence of mangrove roots (pneumatophores) alters local hydrodynamics by slowing currents, dissipating waves, enhancing within-canopy turbulence, and introducing significant spatial variability to the flow, particularly on the stem scale. To date, limited measurements exist within pneumatophore regions owing to the difficulties of measuring on sufficiently small scales. Hence, little is known about the turbulence controlling sediment transport within these regions. We report unique field observations near the seaward edge of a mangrove forest in the Mekong Delta, Vietnam. This forest is exposed to moderate wave energy (maximum heights of around 1 m), with waves observed to propagate and break up to 100 m inside the forest. Our measurements focus on a rapidly prograding area with a relatively sandy substrate and a gentle topographic slope. We resolved millimeter-scale turbulent flows within and above the pneumatophore canopy. Precise measurements of vegetation densities as a function of height were obtained using photogrammetry techniques. The dissipation rate of turbulent kinetic energy was enhanced at the canopy edge (ɛ ~ 10-4 W/kg), and decreased with distance into the forest (ɛ ~ 10-5 W/kg), although rates remained elevated above values measured on the tidal flat immediately offshore of the mangroves (ɛ ~ 10-6 W/kg). The dependence of turbulence on vegetation characteristics and on the stage of the tidal cycle is explored. The hydrodynamic measurements are then linked with changes in bathymetric features noted after a large wave event. Finer mud sediments were deposited outside the forest on the intertidal mudflat, whereas sandy sediments in the fringe region were significant scoured around regions of dense pneumatophores, and sediment mounds developed in the gaps between pneumatophores.

High parasite burden increases the surfacing and mortality of the manila clam (Ruditapes philippinarum) in intertidal sandy mudflats on the west coast of Korea during hot summer.

PubMed

Nam, Ki-Woong; Jeung, Hee-Do; Song, Jae-Hee; Park, Kwan-Ha; Choi, Kwang-Sik; Park, Kyung-Il

2018-01-18

Over the past few decades, mass mortality events of Manila clams have been reported from several tidal flats on the west coast of Korea during hot summers. During such mortality events, once clams simultaneously surface, they fail to re-burrow, perishing within a week. The present study aimed to identify the possible causes of the mass mortality of this clam species by investigating the Perkinsus olseni parasite burden and immune parameters of surfaced clams (SC) and normal buried clams (NBCs) when sea water or sediment temperature in the study area varied from 25 °C to 34 °C from late July through mid-August 2015. We collected 2 groups of clams distributed within a 10-m 2 area when a summer clam mortality event occurred around Seonyu-do Island on the west coast of Korea in 2015. The clams were collected 2 days after they surfaced on the sediment and still looked healthy without any gaping. The clams were transported to the laboratory, and we compared P. olseni infection intensity and cell-mediated hemocyte parameters between the NBCs and SCs. SCs showed significantly higher levels of P. olseni burden, lower condition index, and lower levels of cell-mediated immune functions than those of NBCs. Our study suggests that high P. olseni infection weakens Manila clams' resistance against thermal stress, causing them to surface. We surmise that the summer mass mortality of Manila clams on the west coast of Korea is caused by the combined effects of high P. olseni infection levels and abnormally high water temperature stress.

Microbial mat records in siliciclastic rocks: Examples from Four Indian Proterozoic basins and their modern equivalents in Gulf of Cambay

NASA Astrophysics Data System (ADS)

Sarkar, Subir; Banerjee, Santanu; Samanta, Pradip; Chakraborty, Nivedita; Chakraborty, Partha Pratim; Mukhopadhyay, Soumik; Singh, Arvind K.

2014-09-01

Microbial mat-related structures (MRS) in siliciclastics have been investigated from four Proterozic formations in India, namely the Marwar Supergroup, the Vindhyan Supergroup, the Chhatisgarh Supergroup and the Khariar Group for their spectral variations, genetic aspects, palaeo-environmental significance and influence on sequence stratigraphic architecture. The maximum diversification of MRS has been experienced in shallow marine coastal Precambrian successions. Observations made from modern environment as well as Precambrian rock records clearly indicates that the features like petee ridges, sand-cracks, gas domes, multi-directed ripples, reticulate surfaces, sieve-like surfaces and setulf are most likely to form in the shallowest part of the marine basins, in upper intertidal to supratidal conditions while wrinkle structures, roll-up structures and patchy ripples had a broader range of palaeogeographic settings from the supratidal to subtidal conditions. Discoidal microbial colony (DMC) represents a special variety of the mat-layer feature in modern environment that may have diverse internal architecture, sometimes falsely resembles Ediacaran medusoids. The uniqueness in sequence stratigraphic architecture of the microbial mat-covered sediment is reflected by the presence of more amalgamated HSTs compare to that of TSTs. The preservation of forced and normal regressive deposits on low-gradient epeiric shelf under low continental freeboard indicates microbial mat-infested sea-floor impedes erosion and concomitant sediment supply may facilitate formation and preservation of regressive packages.

The lugworm Arenicola marina: A model of physiological adaptation to life in intertidal sediments

NASA Astrophysics Data System (ADS)

Zebe, E.; Schiedek, D.

1996-03-01

The results of more than two decades of intensive research on the physiological and biochemical features of the lugworm are reviewed with the aim of drawing a general and comprehensive picture of the adaptation of this species to the special conditions of living in the tidal zone, which may also hold true for the majority of invertebrates found in this habitat.

Total and extractable elemental composition of the intertidal estuarine biofilm of the Río de la Plata: Disentangling natural and anthropogenic influences

NASA Astrophysics Data System (ADS)

García-Alonso, J.; Lercari, D.; Araujo, B. F.; Almeida, M. G.; Rezende, C. E.

2017-03-01

Estuarine transitional waters constitute regions affected by or at risk of anthropogenic impact due to urbanization and industrial development. The elemental composition of the intertidal biofilm sediment is an excellent marker for the detection of any impact, and may exert a bottom-up influence by natural concatenation to higher organization levels (e.g. molecules, cells, organisms, communities). The distribution pattern of elemental composition (total and bioavailable fraction) along the estuary axes was analyzed, disentangling potential shifts produced by human activities. We predict that most abundant elements in the Rio de la Plata estuary are the natural earth-crust components and that these will not show any evident gradient along the estuarine axis. Elements involved in human related processes will shape concentration gradients from the most probable source (i.e. cities) indicating estuarine pollution. The research strategy involved the sampling of intertidal biofilm along the entire estuary and the registration of environmental variables and the total and bioavailable elemental composition. Sampling sites represent pristine, agricultural, and urbanized areas along a 428-km-long coastline comprising the inner, middle and outer Río de la Plata estuarine zones and a coastal fringe of oceanic beaches of Uruguay (South America). Biofilm sediment samples were collected in Autumn 2011 and digested for total and extractable (bioavailable) elements quantification measured by ICP-OES. Mercury (Hg) sediments were digested with aqua regia and quantified by cold vapor atomic absorption (CVAAS). The most abundant elements measured were Al, Fe, and Ca in all sampling. Anthropogenic marker elements such as Hg, Cr, Pb, Zn, and Cu were found, even at potentially toxic levels, at urban beaches at the city of Montevideo. The ordination of samples highlights the distinctive characteristics of urban beaches, placed in a particular location along the first principal component. This position is mainly driven by human impact marker metals and C/N ratios. The results highlight the value of bioavailable elemental composition analyses of benthic biofilm as a tool for detecting shifts in estuarine systems.

Carbonate chemistry in a Kennebec Estuary softshell clam flat: Seasonal variability and implications for blue carbon mitigation

NASA Astrophysics Data System (ADS)

Miller, H. R.; Jurcic, B.; Indrick, R.; LaVigne, M.

2016-12-01

Maine's softshell clam (Mya arenaria) industry brings $20 million to the state annually. Reduced clam flat sediments aragonite saturation state (Ω), a predicted effect of ocean acidification, has been shown to negatively impact shell development in M. arenaria's early life stages. Seagrass restoration has been proposed to benefit Maine clam flats. However, the Gulf of Maine experiences seasonal changes in temperature and freshwater input, and the impacts on the carbonate chemistry of intertidal ecosystems have yet to be quantified. We measured overlying water and surface ( upper 1cm) porewater temperature (T), salinity (S), pH, and alkalinity (TA) biweekly from March to August, 2016 to quantify spatial and seasonal sediment Ω variability in a Kennebec Estuary clam flat (Wyman Bay, Maine). Reduced freshwater flow from spring into summer caused an increase in overlying water S (5-25ppt), TA (400-1800ueq/L), and W (0.09-1.20). Surface sediment pore water S (15-29ppt) and TA (1100-2100ueq/L) also increased in summer; however, Ω was variable and remained well below saturation (<0.40). Overlying water pH (7.38-7.96) and sediment pore water pH (6.85-7.47) showed no seasonal trend. Contrary to the predicted impact of seagrass on clam flat carbonate chemistry, preliminary data show sediment Ω is significantly lower in a site located within S. alterniflora (0.150.05) compared to sites lacking alterniflora (0.210.1) within Wyman Bay. Elevated sediment organic matter concentrations found with grasses (4.6%0.5) vs. without (2.9%0.4) may be produced by the grasses and organisms attracted to the ecosystem, and may result in greater respiration driving pH and Ω down rather than up. The strong correlation between TA and S (R2=0.78-0.99) suggests freshwater flow with spring melt during M. arenaria's planktonic larval stage and rain events (predicted to increase with climate change) can reduce Ω, with potentially negative implications for early M. arenaria life stages.

Effect of chronic oil pollution on salt-marsh nitrogen fixation (acetylene redution). [Spartina alterniflora

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomson, A.D.; Webb, K.L.

1984-03-01

Annual acetylene reduction rates associated with intertidal communities in a chronically oil polluted Virgina salt marsh were compared to rates measured in an undisturbed marsh. Chronic oil treatment resulted in visible damage to the higher plants of the Spartina alterniflora zones; however, vegetation-associated acetylene reduction was not different from the untreated control. Sediment rates generally were affected little by oil application, except during the summer when rates in the median tidal elevation zones were considerably higher than those of the control. Acetylene reduction occurred in all transects, each of which extended from upper mudflat to the Spartina patens zone. Intertidalmore » sediment acetylene reduction was patchy, both spatially and seasonally. Estimated rates were greatest near the surface; free-living bacterial N/sub 2/ fixation activity averaged 2.23 mg N per m/sup 2/ per d (range = undetectable to 365 mg N per m/sup 2/ per d) in the untreated and 3.17 mg N per m/sup 2/ per d (range = undetectable to 564 mg N per m/sup 2/ per d) in the oil-treated marsh during the year. Vegetation-associated N/sub 2/ fixation activity yielded highest overall mean rates (156 mg N per M/sub 2/ per d). The seasonal pattern of sediment and vegetation-associated fixation may be controlled by temperature and availability of oxidizable substrates. 39 references, 2 figures, 5 tables.« less

Hydrodynamic conditioning of diversity and functional traits in subtidal estuarine macrozoobenthic communities

NASA Astrophysics Data System (ADS)

van der Wal, Daphne; Lambert, Gwladys I.; Ysebaert, Tom; Plancke, Yves M. G.; Herman, Peter M. J.

2017-10-01

Variations in abundance and diversity of estuarine benthic macrofauna are typically described along the salinity gradient. The influence of gradients in water depth, hydrodynamic energy and sediment properties are less well known. We studied how these variables influence the distribution of subtidal macrofauna in the polyhaline zone of a temperate estuary (Westerschelde, SW Netherlands). Macrofauna density, biomass and species richness, combined in a so-called ecological richness, decreased with current velocities and median grain-size and increased with organic carbon of the sediment, in total explaining 39% of the variation. The macrofauna community composition was less well explained by the three environmental variables (approx. 12-15% in total, with current velocity explaining approx. 8%). Salinity, water depth and distance to the intertidal zone had a very limited effect on both ecological richness and the macrofauna community. The proportion of (surface) deposit feeders (including opportunistic species), decreased relative to that of omnivores and carnivores with increasing current velocity and sediment grain-size. In parallel, the proportion of burrowing sessile benthic species decreased relative to that of mobile benthic species that are able to swim. Correspondingly, spatial variations in hydrodynamics yielded distinct hotspots and coldspots in ecological richness. The findings highlight the importance of local hydrodynamic conditions for estuarine restoration and conservation. The study provides a tool based on a hydrodynamic model to assess and predict ecological richness in estuaries.

Dynamics of Inorganic Nutrients in Intertidal Sediments: Porewater, Exchangeable, and Intracellular Pools

PubMed Central

Garcia-Robledo, Emilio; Bohorquez, Julio; Corzo, Alfonso; Jimenez-Arias, Juan L.; Papaspyrou, Sokratis

2016-01-01

The study of inorganic nutrients dynamics in shallow sediments usually focuses on two main pools: porewater (PW) nutrients and exchangeable (EX) ammonium and phosphate. Recently, it has been found that microphytobenthos (MPB) and other microorganisms can accumulate large amounts of nutrients intracellularly (IC), highlighting the biogeochemical importance of this nutrient pool. Storing nutrients could support the growth of autotrophs when nutrients are not available, and could also provide alternative electron acceptors for dissimilatory processes such as nitrate reduction. Here, we studied the magnitude and relative importance of these three nutrient pools (PW, IC, and EX) and their relation to chlorophylls (used as a proxy for MPB abundance) and organic matter (OM) contents in an intertidal mudflat of Cadiz Bay (Spain). MPB was localized in the first 4 mm of the sediment and showed a clear seasonal pattern; highest chlorophylls content was found during autumn and lowest during spring-summer. The temporal and spatial distribution of nutrients pools and MPB were largely correlated. Ammonium was higher in the IC and EX fractions, representing on average 59 and 37% of the total ammonium pool, respectively. Similarly, phosphate in the IC and EX fractions accounted on average for 40 and 31% of the total phosphate pool, respectively. Nitrate in the PW was low, suggesting low nitrification activity and rapid consumption. Nitrate accumulated in the IC pool during periods of moderate MPB abundance, being up to 66% of the total nitrate pool, whereas it decreased when chlorophyll concentration peaked likely due to a high nitrogen demand. EX-Nitrate accounted for the largest fraction of total sediment nitrate, 66% on average. The distribution of EX-Nitrate was significantly correlated with chlorophyll and OM, which probably indicates a relation of this pool to an increased availability of sites for ionic adsorption. This EX-Nitrate pool could represent an alternative nitrate source with significant concentrations available to the microbial community, deeper in the sediment below the oxic layer. PMID:27303370

Dynamics of Inorganic Nutrients in Intertidal Sediments: Porewater, Exchangeable, and Intracellular Pools.

PubMed

Garcia-Robledo, Emilio; Bohorquez, Julio; Corzo, Alfonso; Jimenez-Arias, Juan L; Papaspyrou, Sokratis

2016-01-01

The study of inorganic nutrients dynamics in shallow sediments usually focuses on two main pools: porewater (PW) nutrients and exchangeable (EX) ammonium and phosphate. Recently, it has been found that microphytobenthos (MPB) and other microorganisms can accumulate large amounts of nutrients intracellularly (IC), highlighting the biogeochemical importance of this nutrient pool. Storing nutrients could support the growth of autotrophs when nutrients are not available, and could also provide alternative electron acceptors for dissimilatory processes such as nitrate reduction. Here, we studied the magnitude and relative importance of these three nutrient pools (PW, IC, and EX) and their relation to chlorophylls (used as a proxy for MPB abundance) and organic matter (OM) contents in an intertidal mudflat of Cadiz Bay (Spain). MPB was localized in the first 4 mm of the sediment and showed a clear seasonal pattern; highest chlorophylls content was found during autumn and lowest during spring-summer. The temporal and spatial distribution of nutrients pools and MPB were largely correlated. Ammonium was higher in the IC and EX fractions, representing on average 59 and 37% of the total ammonium pool, respectively. Similarly, phosphate in the IC and EX fractions accounted on average for 40 and 31% of the total phosphate pool, respectively. Nitrate in the PW was low, suggesting low nitrification activity and rapid consumption. Nitrate accumulated in the IC pool during periods of moderate MPB abundance, being up to 66% of the total nitrate pool, whereas it decreased when chlorophyll concentration peaked likely due to a high nitrogen demand. EX-Nitrate accounted for the largest fraction of total sediment nitrate, 66% on average. The distribution of EX-Nitrate was significantly correlated with chlorophyll and OM, which probably indicates a relation of this pool to an increased availability of sites for ionic adsorption. This EX-Nitrate pool could represent an alternative nitrate source with significant concentrations available to the microbial community, deeper in the sediment below the oxic layer.

Mixed-sediment transport modelling in Scheldt estuary with a physics-based bottom friction law

NASA Astrophysics Data System (ADS)

Bi, Qilong; Toorman, Erik A.

2015-04-01

In this study, the main object is to investigate the performance of a few new physics-based process models by implementation into a numerical model for the simulation of the flow and morphodynamics in the Western Scheldt estuary. In order to deal with the complexity within the research domain, and improve the prediction accuracy, a 2D depth-averaged model has been set up as realistic as possible, i.e. including two-way hydrodynamic-sediment transport coupling, mixed sand-mud sediment transport (bedload transport as well as suspended load in the water column) and a dynamic non-uniform bed composition. A newly developed bottom friction law, based on a generalised mixing-length (GML) theory, is implemented, with which the new bed shear stress closure is constructed as the superposition of the turbulent and the laminar contribution. It allows the simulation of all turbulence conditions (fully developed turbulence, from hydraulic rough to hydraulic smooth, transient and laminar), and the drying and wetting of intertidal flats can now be modelled without specifying an inundation threshold. The benefit is that intertidal morphodynamics can now be modelled with great detail for the first time. Erosion and deposition in these areas can now be estimated with much higher accuracy, as well as their contribution to the overall net fluxes. Furthermore, Krone's deposition law has been adapted to sand-mud mixtures, and the critical stresses for deposition are computed from suspension capacity theory, instead of being tuned. The model has been calibrated and results show considerable differences in sediment fluxes, compared to a traditional approach and the analysis also reveals that the concentration effects play a very important role. The new bottom friction law with concentration effects can considerably alter the total sediment flux in the estuary not only in terms of magnitude but also in terms of erosion and deposition patterns.

Effects of temporal fluctuation in population processes of intertidal Lanice conchilega (Pallas, 1766) aggregations on its ecosystem engineering

NASA Astrophysics Data System (ADS)

Alves, Renata M. S.; Vanaverbeke, Jan; Bouma, Tjeerd J.; Guarini, Jean-Marc; Vincx, Magda; Van Colen, Carl

2017-03-01

Ecosystem engineers contribute to ecosystem functioning by regulating key environmental attributes, such as habitat availability and sediment biogeochemistry. While autogenic engineers can increase habitat complexity passively and provide physical protection to other species, allogenic engineers can regulate sediment oxygenation and biogeochemistry through bioturbation and/or bioirrigation. Their effects rely on the physical attributes of the engineer and/or its biogenic constructs, such as abundance and/or size. The present study focused on tube aggregations of a sessile, tube-building polychaete that engineers marine sediments, Lanice conchilega. Its tube aggregations modulate water flow by dissipating energy, influencing sedimentary processes and increasing particle retention. These effects can be influenced by temporal fluctuations in population demographic processes. Presently, we investigated the relationship between population processes and ecosystem engineering through an in-situ survey (1.5 years) of L. conchilega aggregations at the sandy beach of Boulogne-sur-Mer (France). We (1) evaluated temporal patterns in population structure, and (2) investigated how these are related to the ecosystem engineering of L. conchilega on marine sediments. During our survey, we assessed tube density, demographic structure, and sediment properties (surficial chl-a, EPS, TOM, median and mode grain size, sorting, and mud and water content) on a monthly basis for 12 intertidal aggregations. We found that the population was mainly composed by short-lived (6-10 months), small-medium individuals. Mass mortality severely reduced population density during winter. However the population persisted, likely due to recruits from other populations, which are associated to short- and long-term population dynamics. Two periods of recruitment were identified: spring/summer and autumn. Population density was highest during the spring recruitment and significantly affected several environmental properties (i.e. EPS, TOM, mode grain size, mud and water content), suggesting that demographic processes may be responsible for periods of pronounced ecosystem engineering with densities of approx. 30 000 ind·m-2.

Flow and nutrient dynamics in a subterranean estuary (Waquoit Bay, MA, USA): Field data and reactive transport modeling

NASA Astrophysics Data System (ADS)

Spiteri, Claudette; Slomp, Caroline P.; Charette, Matthew A.; Tuncay, Kagan; Meile, Christof

2008-07-01

A two-dimensional (2D) reactive transport model is used to investigate the controls on nutrient ( NO3-, NH4+, PO 4) dynamics in a coastal aquifer. The model couples density-dependent flow to a reaction network which includes oxic degradation of organic matter, denitrification, iron oxide reduction, nitrification, Fe 2+ oxidation and sorption of PO 4 onto iron oxides. Porewater measurements from a well transect at Waquoit Bay, MA, USA indicate the presence of a reducing plume with high Fe 2+, NH4+, DOC (dissolved organic carbon) and PO 4 concentrations overlying a more oxidizing NO3--rich plume. These two plumes travel nearly conservatively until they start to overlap in the intertidal coastal sediments prior to discharge into the bay. In this zone, the aeration of the surface beach sediments drives nitrification and allows the precipitation of iron oxide, which leads to the removal of PO 4 through sorption. Model simulations suggest that removal of NO3- through denitrification is inhibited by the limited overlap between the two freshwater plumes, as well as by the refractory nature of terrestrial DOC. Submarine groundwater discharge is a significant source of NO3- to the bay.

Unstable Pore-Water Flow in Intertidal Wetlands

NASA Astrophysics Data System (ADS)

Barry, D. A.; Shen, C.; Li, L.

2014-12-01

Salt marshes are important intertidal wetlands strongly influenced by interactions between surface water and groundwater. Bordered by coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur over vastly different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil condition, particularly aeration, which influences the marsh plant growth. Numerous studies have been carried out to examine the pore-water flow process in the marsh soil driven by tides, focusing on stable flow with the assumption of homogeneity in soil and fluid properties. This assumption, however, is questionable given the actual inhomogeneous conditions in the field. For example, the salinity of surface water in the tidal creek varies temporally and spatially due to the influence of rainfall and evapotranspiration as well as the freshwater input from upland areas to the estuary, creating density gradients across the marsh surface and within the marsh soil. Many marshes possess soil stratigraphy with low-permeability mud typically overlying high-permeability sandy deposits. Macropores such as crab burrows are commonly distributed in salt marsh sediments. All these conditions are prone to the development of non-uniform, unstable preferential pore-water flow in the marsh soil, for example, funnelling and fingering. Here we present results from laboratory experiments and numerical simulations to explore such unstable flow. In particular, the analysis aims to address how the unstable flow modifies patterns of local pore-water movement and solute transport, as well as the overall exchange between the marsh soil and creek water. The changes would influence not only the marsh soil condition for plant growth but also nutrient cycling in the marsh soil and discharge to the coastal sea.

Short-term dynamics of intertidal microphytobenthic biomass. Mathematical modelling [La dynamique a court terme de la biomasse du microphytobenthos intertidal. Formalisation mathematique

USGS Publications Warehouse

Guarini, J.-M.; Gros, P.; Blanchard, G.F.; Bacher, C.

1999-01-01

We formulate a deterministic mathematical model to describe the dynamics of the microphytobenthos of intertidal mudflats. It is 'minimal' because it only takes into account the essential processes governing the functioning of the system: the autotrophic production, the active upward and downward migrations of epipelic microalgae, the saturation of the mud surface by a biofilm of diatoms and the global net loss rates of biomass. According to the photic environment of the benthic diatoms inhabiting intertidal mudflats, and to their migration rhythm, the model is composed of two sub-systems of ordinary differential equations; they describe the simultaneous evolution of the biomass 'S' concentrated in the mud surface biofilm - the photic layer - and of the biomass 'F' diluted in the topmost centimetre of the mud - the aphotic layer. Qualitatively, the model solutions agree fairly well with the in situ observed dynamics of the S + F biomass. The study of the mathematical properties of the model, under some simplifying assumptions, shows the convergence of solutions to a stable cyclic equilibrium, whatever the frequencies of the physical synchronizers of the production. The sensitivity analysis reveals the necessity of a better knowledge of the processes of biomass losses, which so far are uncertain, and may further vary in space and time.

Larval Behaviours and Their Contribution to the Distribution of the Intertidal Coral Reef Sponge Carteriospongia foliascens

PubMed Central

Abdul Wahab, Muhammad Azmi; de Nys, Rocky; Webster, Nicole; Whalan, Steve

2014-01-01

Sponges (Phylum Porifera) are an evolutionary and ecologically significant group; however information on processes influencing sponge population distributions is surprisingly limited. Carteriospongia foliascens is a common Indo-Pacific sponge, which has been reported from the intertidal to the mesophotic. Interestingly, the distribution of C. foliascens at inshore reefs of the Great Barrier Reef is restricted to the intertidal with no individuals evident in adjacent subtidal habitats. The abundance of C. foliascens and substrate availability was first quantified to investigate the influence of substrate limitation on adult distribution. Pre-settlement processes of larval spawning, swimming speeds, phototaxis, vertical migration, and settlement to intertidal and subtidal substrate cues were also quantified. Notably, suitable settlement substrate (coral rubble) was not limiting in subtidal habitats. C. foliascens released up to 765 brooded larvae sponge−1 day−1 during the day, with larvae (80%±5.77) being negatively phototactic and migrating to the bottom within 40 minutes from release. Subsequently, larvae (up to 58.67%±2.91) migrated to the surface after the loss of the daylight cue (nightfall), and after 34 h post-release >98.67% (±0.67) of larvae had adopted a benthic habit regardless of light conditions. Intertidal and subtidal biofilms initiated similar settlement responses, inducing faster (as early 6 h post-release) and more successful metamorphosis (>60%) than unconditioned surfaces. C. foliascens has a high larval supply and larval behaviours that support recruitment to the subtidal. The absence of C. foliascens in subtidal habitats at inshore reefs is therefore proposed to be a potential consequence of post-settlement mortalities. PMID:24853091

Hurricane-induced Sediment Transport and Morphological Change in Jamaica Bay, New York

NASA Astrophysics Data System (ADS)

Hu, K.; Chen, Q. J.

2016-02-01

Jamaica Bay is located in Brooklyn and Queens, New York on the western end of the south shore of the Long Island land mass. It experienced a conversion of more than 60% of the vegetated salt-marsh islands to intertidal and subtidal mudflats. Hurricanes and nor'easters are among the important driving forces that reshape coastal landscape quickly and affect wetland sustainability. Wetland protection and restoration need a better understanding of hydrodynamics and sediment transport in this area, especially under extreme weather conditions. Hurricane Sandy, which made landfall along east coast on October 30, 2012, provides a critical opportunity for studying the impacts of hurricanes on sedimentation, erosion and morphological changes in Jamaica Bay and salt marsh islands. The Delft3D model suit was applied to model hydrodynamics and sediment transport in Jamaica Bay and salt marsh islands. Three domains were set up for nesting computation. The local domain covering the bay and salt marshes has a resolution of 10 m. The wave module was online coupled with the flow module. Vegetation effects were considered as a large number of rigid cylinders by a sub-module in Delft3D. Parameters in sediment transport and morphological change were carefully chosen and calibrated. Prior- and post-Sandy Surface Elevation Table (SET)/accretion data including mark horizon (short-term) and 137Cs and 210Pb (long-term) at salt marsh islands in Jamaica Bay were used for model validation. Model results indicate that waves played an important role in hurricane-induced morphological change in Jamaica Bay and wetlands. In addition, numerical experiments were carried out to investigate the impacts of hypothetic hurricanes. This study has been supported by the U.S. Geological Survey Hurricane Sandy Disaster Recovery Act Funds.

Benthic metabolism over the emersion - immersion alternation in sands colonized by the invasive Manila clam Ruditapes philippinarum

NASA Astrophysics Data System (ADS)

Migné, Aline; Trigui, Rima Jihane; Davoult, Dominique; Desroy, Nicolas

2018-01-01

The effect of an invasive infaunal suspension-feeding bivalve, the Manila clam Ruditapes philippinarum, on benthic inorganic carbon and nutrient fluxes was examined through in situ incubations. Measurements were performed in spring and summer on a tidal sandflat of the Rance estuary (south part of the Western English Channel) colonized by the Manila clam after its deliberate introduction in the 1990's. Benthic inorganic carbon fluxes were measured using light and dark benthic chambers both at emersion and immersion. Benthic nutrient fluxes were measured using dark benthic chambers at immersion. Inorganic carbon (IC) and ammonium sediment release under darkness at immersion reached 5.60 mmol m-2 h-1 and 441 μmol m-2 h-1 respectively for a clam density of 291 ind m-2. The sediment IC-release under darkness was lower during emersion than during immersion, probably due to the reduced activity of infauna at low tide. Under ambient light, a sediment IC-uptake was systematically measured at emersion, indicating a net autotrophy under the condition of measurements (125 < surface PAR < 1670 μmol m-2 s-1), while either sediment IC-uptake or release was measured at immersion according to light variation (20 < underwater PAR < 990 μmol m-2 s-1). The highest gross community primary production, calculated from highest IC-fluxes at light (i.e. net community production) and highest IC-fluxes at dark (i.e. community respiration), was similar at emersion and immersion and reached 6.2 mmolC m-2 h-1. These results suggest that the metabolic activity of the invasive Manila clam Ruditapes philippinarum contributes to increase inorganic C and ammonium sediment release. These regenerated nutrients may support microphytobenthic production which appeared particularly high on this intertidal sand flat.

Enhanced Biotransformation of Fluoranthene by Intertidally Derived Cunninghamella elegans under Biofilm-Based and Niche-Mimicking Conditions

PubMed Central

Mitra, Sayani; Pramanik, Arnab; Banerjee, Srijoni; Haldar, Saubhik; Gachhui, Ratan

2013-01-01

The aims of the investigation were to ascertain if surface attachment of Cunninghamella elegans and niche intertidal conditions provided in a bioreactor influenced biotransformation of fluoranthene by C. elegans. A newly designed polymethylmethacrylate (PMMA) conico-cylindrical flask (CCF) holding eight equidistantly spaced rectangular strips mounted radially on a circular disc allowed comparison of fluoranthene biotransformation between CCFs with a hydrophobic surface (PMMA-CCF) and a hydrophilic glass surface (GS-CCF) and a 500-ml Erlenmeyer flask (EF). Fluoranthene biotransformation was higher by 22-fold, biofilm growth was higher by 3-fold, and cytochrome P450 gene expression was higher by 2.1-fold when C. elegans was cultivated with 2% inoculum as biofilm culture in PMMA-CCF compared to planktonic culture in EF. Biotransformation was enhanced by 7-fold with 10% inoculum. The temporal pattern of biofilm progression based on three-channel fluorescence detection by confocal laser scanning microscopy demonstrated well-developed, stable biofilm with greater colocalization of fluoranthene within extracellular polymeric substances and filaments of the biofilm grown on PMMA in contrast to a glass surface. A bioreactor with discs rotating at 2 revolutions per day affording 6-hourly emersion and immersion mimicked the niche intertidal habitat of C. elegans and supported biofilm formation and transformation of fluoranthene. The amount of transformed metabolite was 3.5-fold, biofilm growth was 3-fold, and cytochrome P450 gene expression was 1.9-fold higher in the process mimicking the intertidal conditions than in a submerged process without disc rotation. In the CCF and reactor, where biofilm formation was comparatively greater, higher concentration of exopolysaccharides allowed increased mobilization of fluoranthene within the biofilm with consequential higher gene expression leading to enhanced volumetric productivity. PMID:24038685

Uniform functional structure across spatial scales in an intertidal benthic assemblage.

PubMed

Barnes, R S K; Hamylton, Sarah

2015-05-01

To investigate the causes of the remarkable similarity of emergent assemblage properties that has been demonstrated across disparate intertidal seagrass sites and assemblages, this study examined whether their emergent functional-group metrics are scale related by testing the null hypothesis that functional diversity and the suite of dominant functional groups in seagrass-associated macrofauna are robust structural features of such assemblages and do not vary spatially across nested scales within a 0.4 ha area. This was carried out via a lattice of 64 spatially referenced stations. Although densities of individual components were patchily dispersed across the locality, rank orders of importance of the 14 functional groups present, their overall functional diversity and evenness, and the proportions of the total individuals contained within each showed, in contrast, statistically significant spatial uniformity, even at areal scales <2 m(2). Analysis of the proportional importance of the functional groups in their geospatial context also revealed weaker than expected levels of spatial autocorrelation, and then only at the smaller scales and amongst the most dominant groups, and only a small number of negative correlations occurred between the proportional importances of the individual groups. In effect, such patterning was a surface veneer overlying remarkable stability of assemblage functional composition across all spatial scales. Although assemblage species composition is known to be homogeneous in some soft-sediment marine systems over equivalent scales, this combination of patchy individual components yet basically constant functional-group structure seems as yet unreported. Copyright © 2015 Elsevier Ltd. All rights reserved.

Carbon, nutrient and trace metal cycling in sandy sediments: A comparison of high-energy beaches and backbarrier tidal flats

NASA Astrophysics Data System (ADS)

Reckhardt, Anja; Beck, Melanie; Seidel, Michael; Riedel, Thomas; Wehrmann, Achim; Bartholomä, Alexander; Schnetger, Bernhard; Dittmar, Thorsten; Brumsack, Hans-Jürgen

2015-06-01

In order to evaluate the importance of coastal sandy sediments and their contribution to carbon, nutrient and metal cycling we investigated two beach sites on Spiekeroog Island, southern North Sea, Germany, and a tidal flat margin, located in Spiekeroog's backbarrier area. We also analyzed seawater and fresh groundwater on Spiekeroog Island, to better define endmember concentrations, which influence our study sites. Intertidal sandy flats and beaches are characterized by pore water advection. Seawater enters the sediment during flood and pore water drains out during ebb and at low tide. This pore water circulation leads to continuous supply of fresh organic substrate to the sediments. Remineralization products of microbial degradation processes, i.e. nutrients, and dissolved trace metals from the reduction of particulate metal oxides, are enriched in the pore water compared to open seawater concentrations. The spatial distribution of dissolved organic carbon (DOC), nutrients (PO43-, NO3-, NO2-, NH4+, Si(OH)4 and total alkalinity), trace metals (dissolved Fe and Mn) as well as sulfate suggests that the exposed beach sites are subject to relatively fast pore water advection, which leads to organic matter and oxygen replenishment. Frequent pore water exchange further leads to comparatively low nutrient concentrations. Sulfate reduction does not appear to play a major role during organic matter degradation. High nitrate concentrations indicate that redox conditions are oxic within the duneward freshwater influenced section, while ammonification, denitrification, manganese and iron reduction seem to prevail in the ammonium-dominated seawater circulation zone. In contrast, the sheltered tidal flat margin site exhibits a different sedimentology (coarser beach sands versus finer tidal flat sands) and nutrients, dissolved manganese and DOC accumulate in the pore water. Ammonium is the dominant pore water nitrogen species and intense sulfate reduction leads to the formation of sulfide, which precipitates dissolved iron as iron sulfide. These findings are due to slower advective pore water exchange in the tidal flat sediments. This study illustrates how different energy regimes affect biogeochemical cycling in intertidal permeable sediments.

Effectiveness of remediation of metal-contaminated mangrove sediments (Sydney estuary, Australia).

PubMed

Birch, Gavin; Nath, Bibhash; Chaudhuri, Punarbasu

2015-04-01

Industrial activities and urbanization have had a major consequence for estuarine ecosystem health and water quality globally. Likewise, Sydney estuary has been significantly impacted by widespread, poor industrial practices in the past, and remediation of legacy contaminants have been undertaken in limited parts of this waterway. The objective of the present investigation was to determine the effectiveness of remediation of a former Pb-contaminated industrial site in Homebush Bay on Sydney estuary (Australia) through sampling of inter-tidal sediments and mangrove (Avicennia marina) tissue (fine nutritive roots, pneumatophores, and leaves). Results indicate that since remediation 6 years previously, Pb and other metals (Cu, Ni and Zn) in surficial sediment have increased to concentrations that approach pre-remediation levels and that they were considerably higher than pre-settlement levels (3-30 times), as well as at the reference site. Most metals were compartmentalized in fine nutritive roots with bio-concentration factors greater than unity, while tissues of pneumatophores and leaves contained low metal concentrations. Lead concentrations in fine nutritive root, pneumatophore, and leaf tissue of mangroves from the remediated site were similar to trees in un-remediated sites of the estuary and were substantially higher than plants at the reference site. The situation for Zn in fine nutritive root tissue was similar. The source of the metals was either surface/subsurface water from the catchment or more likely remobilized contaminated sediment from un-remediated parts of Homebush Bay. Results of this study demonstrate the problems facing management in attempting to reduce contamination in small parts of a large impacted area to concentrations below local base level.

Evidence of tidal processes from the lower part of the Witwatersrand Supergroup, South Africa

NASA Astrophysics Data System (ADS)

Eriksson, Kenneth A.; Turner, Brian R.; Vos, Richard G.

1981-08-01

A 1600-m succession of quartz arenites and associated shaley deposits comprising the Hospital Hill Subgroup at the base of the Witwatersrand Supergroup is considered to have been deposited largely under the influence of tidal processes. Facies analysis indicates that deposition occurred in the following environments: (1) marine shalf; (2) shallow subtidal to intertidal; (3) intertidal flat; and (4) tidal inlet. The presence of strong tidal currents implies that the Witwatersrand Basin was open to an ocean basin, at least during the early stages of its evolution. Palaeocurrent trends and isopach data suggest that this probably lay to the southwest, an area now occupied by the high grade Natal—Namaqua metamorphic belt. The contrast between the supermature quartz arenites of the Hospital Hill Subgroup and the overlying gold-bearing immature subgreywackes, feldspathic quartzites and conglomerates of fluvial origin is believed to be a function of tidal reworking of sediments.

A method to assess the evolution and recovery of heavy metal pollution in estuarine sediments: Past history, present situation and future perspectives.

PubMed

Bárcena, Javier F; Claramunt, Inigo; García-Alba, Javier; Pérez, María Luisa; García, Andrés

2017-11-15

A methodology to assess the historical evolution and recovery of heavy metal pollution in estuarine sediments was developed and is presented here. This approach quantifies the distribution of heavy metals in sediment cores, and investigates the influence of anthropogenic activities and/or core locations on the heavy metal pollution, by proposing and using sediment quality indices and polynomial regressions. The method has been applied to the Suances Estuary confirming its suitability as a comprehensive and practical management tool. In this estuary, the evolution of heavy metal pollution (since 1997-1998 to 2015) pointed out the deeper the sediments, the more polluted, indicating a recovery at the upper layers due to the closure and ending of washing discharges from mining, and the reduction of metal loads from industrial wastewaters. In terms of global pollution, the intertidal and subtidal sediments will require 43.1±2.8 and 8.6±0.6years to be unpolluted, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spatial and temporal correlation between beach and wave processes: implications for bar-berm sediment transition

NASA Astrophysics Data System (ADS)

Joevivek, V.; Chandrasekar, N.; Saravanan, S.; Anandakumar, H.; Thanushkodi, K.; Suguna, N.; Jaya, J.

2018-06-01

Investigation of a beach and its wave conditions is highly requisite for understanding the physical processes in a coast. This study composes spatial and temporal correlation between beach and nearshore processes along the extensive sandy beach of Nagapattinam coast, southeast peninsular India. The data collection includes beach profile, wave data, and intertidal sediment samples for 2 years from January 2011 to January 2013. The field data revealed significant variability in beach and wave morphology during the northeast (NE) and southwest (SW) monsoon. However, the beach has been stabilized by the reworking of sediment distribution during the calm period. The changes in grain sorting and longshore sediment transport serve as a clear evidence of the sediment migration that persevered between foreshore and nearshore regions. The Empirical Orthogonal Function (EOF) analysis and Canonical Correlation Analysis (CCA) were utilized to investigate the spatial and temporal linkages between beach and nearshore criterions. The outcome of the multivariate analysis unveiled that the seasonal variations in the wave climate tends to influence the bar-berm sediment transition that is discerned in the coast.

Effect of intertidal exposure on Vibrio parahaemolyticus levels in Pacific Northwest oysters.

PubMed

Nordstrom, J L; Kaysner, C A; Blackstone, G M; Vickery, M C L; Bowers, J C; DePaola, A

2004-10-01

Interest in Vibrio parahaemolyticus (Vp) increased in the United States following Vp-associated gastroenteritis outbreaks in 1997 and 1998 involving the West Coast and other areas. The present study evaluated multiple aspects of Vp ecology in the Pacific Northwest with three objectives: (i) to determine the effect of low-tide exposure on Vp levels in oysters, (ii) to determine the relationship between total and pathogenic Vp, and (iii) to examine sediments and aquatic fauna as reservoirs for pathogenic Vp. Samples were collected from intertidal reefs along Hood Canal, Wash., in August 2001. Fecal matter from marine mammals and aquatic birds as well as intestinal contents from bottom-dwelling fish were tested. Total and pathogenic Vp levels in all the samples were enumerated with colony hybridization procedures using DNA probes that targeted the thermolabile direct hemolysin (tlh) and thermostable direct hemolysin (tdh) genes, respectively. The mean Vp densities in oysters were four to eight times greater at maximum exposure than at the corresponding first exposure. While tdh-positive Vp counts were generally < or = 10 CFU/g at first exposure, counts as high as 160 CFU/g were found at maximum exposure. Vp concentrations in sediments were not significantly different from those in oysters at maximum exposure. Pathogenic (tdh positive) Vp was detected in 9 of 42 (21%) oyster samples at maximum exposure, in 5 of 19 (26%) sediment samples, but in 0 of 9 excreta samples. These results demonstrate that summer conditions permit the multiplication of Vp in oysters exposed by a receding tide.

Frequency domain electromagnetic induction survey in the intertidal zone: Limitations of low-induction-number and depth of exploration

NASA Astrophysics Data System (ADS)

Delefortrie, Samuël; Saey, Timothy; Van De Vijver, Ellen; De Smedt, Philippe; Missiaen, Tine; Demerre, Ine; Van Meirvenne, Marc

2014-01-01

Subsurface investigation in the Belgian intertidal zone is severely complicated due to high heterogeneity and tides. Near-surface geophysical techniques can offer assistance since they allow fast surveying and collection of high spatial density data and frequency domain electromagnetic induction (EMI) was chosen for archaeological prospection on the Belgian shore. However, in the intertidal zone the effects of extreme salinity compromise validity of low-induction-number (LIN) approximated EMI data. In this paper, the effects of incursion of seawater on multi-receiver EMI data are investigated by means of survey results, field observations, cone penetration tests and in-situ electrical conductivity measurements. The consequences of LIN approximation breakdown were researched. Reduced depth of investigation of the quadrature-phase (Qu) response and a complex interpretation of the in-phase response were confirmed. Nonetheless, a high signal-to-noise ratio of the Qu response and viable data with regard to shallow subsurface investigation were also evidenced, allowing subsurface investigation in the intertidal zone.

Dynamic equilibrium behaviour observed on two contrasting tidal flats from daily monitoring of bed-level changes

NASA Astrophysics Data System (ADS)

Hu, Zhan; van der Wal, Daphne; Cai, Huayang; van Belzen, Jim; Bouma, Tjeerd J.

2018-06-01

Dynamic equilibrium theory (DET) has been applied to tidal flats to systematically explain intertidal morphological responses to various distributions of bed shear stress (BSS). However, it is difficult to verify this theory with field observations because of the discrepancy between the idealized conceptions of theory and the complex reality of intertidal dynamics. The core relation between intertidal morphodynamics and BSS distribution can be easily masked by noise in complex datasets, leading to conclusions of insufficient field evidence to support DET. In the current study, hydrodynamic and morphodynamic data were monitored daily for one year on two tidal flats with contrasting wave exposures. BSS distribution was obtained by validated numerical models. Tidal flat dynamic equilibrium behaviour and BSS were linked via Empirical Orthogonal Function (EOF) analysis. We show that the principal morphodynamic modes corresponded well with the respective modes of BSS found at both sites. Tide-induced BSS was the dominant force at both sites, regardless of the level of wave exposure. The overall erosional and steepening trend found at the two flats can be attributed to the prevailing action of tidal forcing and reduced sediment supply. Hence, EOF analysis confirmed that tidal flat morphodynamics are consistent with DET, providing both field and model evidence to support this theory.

Molluscs of an intertidal soft-sediment area in China: Does overfishing explain a high density but low diversity community that benefits staging shorebirds?

NASA Astrophysics Data System (ADS)

Yang, Hong-Yan; Chen, Bing; Piersma, Theunis; Zhang, Zhengwang; Ding, Changqing

2016-03-01

The Yellow Sea is a key staging ground for shorebirds that migrate from Australasia to the Arctic each spring. A lot of attention has been paid to the impact of habitat loss due to land reclamation on shorebird survival, but any effects of overfishing of coastal resources are unclear. In this study, the abundance of molluscs in the intertidal mudflats of northern Bohai Bay on the Chinese Yellow Sea was investigated in 2008-2014 from the perspective of their importance as food for northward migrating shorebirds, especially Red Knots Calidris canutus. Numerically contributing 96% to the numbers of 17 species found in spring 2008, the bivalve Potamocorbula laevis (the staple food of Red Knots and other shorebirds) dominated the intertidal mollusc community. In the spring of 2008-2014, the densities of P. laevis were surprisingly high, varying between 3900 and 41,000 individuals/m2 at distinctly small sizes (average shell lengths of 1.1 to 4.8 mm), and thus reaching some of the highest densities of marine bivalves recorded worldwide and providing good food for shorebirds. The distribution of P. laevis was associated with relatively soft sediments in close proximity to the recently built seawalls. A monthly sampling programme showed steep seasonal changes in abundance and size. P. laevis were nearly absent in winter, each year settling on the intertidal mudflats anew. Peak densities were reached in spring, when 0-age P. laevis were 1-3 mm long. The findings point to a highly unusual demographic structure of the species, suggesting that some interfering factors are at play. We hypothesise that the current dominance of young P. laevis in Bohai Bay reflects the combined pressures of a nearly complete active removal of adult populations from mid-summer to autumn for shrimp farming (this clearing of adults may offer space for recruitment during the next spring) and low numbers of epibenthic predators of bivalves, such as shrimps and crabs, due to persistent overfishing in recent decades (allowing freshly settled juveniles to reach high densities). To the best of our knowledge, the idea that overfishing of competing marine mesopredators benefits staging shorebirds, at least in the short term, is novel; it now needs further experimental and comparative scrutiny. The long-term effects of overfishing on benthic communities of the mudflats need further investigation.

Mechanisms of Sediment Transport to an Abandoned Distributary Channel on the Huanghe (Yellow River) Delta, China

NASA Astrophysics Data System (ADS)

Kumpf, L. L.; Kineke, G. C.; Carlson, B.; Mullane, M.

2017-12-01

Avulsions on the fine-grained Huanghe delta have left it scarred with traces of abandoned distributary channels that become intertidal systems, open to water and sediment exchange with the sea. In 1996, an engineered avulsion of the Huanghe left a 30 km long abandoned channel to the south of the modern active river channel. Though all fluvial input was cut off, present-day sedimentation on the new tidal flats has been observed at rates around 2 cm/yr. The source must be suspended-sediment from the Bohai Sea conveyed by the tidal channel network, but the mechanisms promoting sediment import are unknown. Possible mechanisms include (A) import sourced from the sediment-rich buoyant coastal plume, (B) wave resuspension on the shallow shelf, (C) reverse-estuarine residual circulation in the tidal channel, and (D) tidal asymmetry in the channel. Over three summers, in situ measurements of current velocity, suspended-sediment concentration (SSC), and wave climate were made on the delta front, and measurements of velocity, SSC, and salinity were made within the tidal channel. Results suggest that the buoyant plume from the active Huanghe channel can transport sediment south toward the tidal channel mouth (A). Additionally, wave resuspension (B) takes place on the subaqueous topset beds when the significant wave height exceeds 1 m, providing potential sources of suspended-sediment to the tidal channel. Within the abandoned channel, the tidal channel can become hypersaline and exhibit reverse-estuarine circulation (C), which would promote import of turbid coastal water near the surface. Time-series of velocity in the tidal channel indicate that ebb currents are consistently higher than flood currents through the spring-neap cycle (D), with maximum velocities exceeding 1 m/s and corresponding maximum SSC reaching 2 g/L during spring tide. While ebb dominance would typically tend to flush the system of its sediment over time, sediment supplied to the tidal flats may not be removed during the ebb, leading to net accumulation. Flocculation may also enhance settling over the inundated mudflats, contributing to the observed sedimentation. If import and sedimentation proceed at current rates, this abandoned channel may eventually anneal, contributing to the stability of the Huanghe delta.

Key parameters of the sediment surface morphodynamics in an estuary - An assessment of model solutions

NASA Astrophysics Data System (ADS)

Sampath, D. M. R.; Boski, T.

2018-05-01

Large-scale geomorphological evolution of an estuarine system was simulated by means of a hybrid estuarine sedimentation model (HESM) applied to the Guadiana Estuary, in Southwest Iberia. The model simulates the decadal-scale morphodynamics of the system under environmental forcing, using a set of analytical solutions to simplified equations of tidal wave propagation in shallow waters, constrained by empirical knowledge of estuarine sedimentary dynamics and topography. The key controlling parameters of the model are bed friction (f), current velocity power of the erosion rate function (N), and sea-level rise rate. An assessment of sensitivity of the simulated sediment surface elevation (SSE) change to these controlling parameters was performed. The model predicted the spatial differentiation of accretion and erosion, the latter especially marked in the mudflats within mean sea level and low tide level and accretion was mainly in a subtidal channel. The average SSE change mutually depended on both the friction coefficient and power of the current velocity. Analysis of the average annual SSE change suggests that the state of intertidal and subtidal compartments of the estuarine system vary differently according to the dominant processes (erosion and accretion). As the Guadiana estuarine system shows dominant erosional behaviour in the context of sea-level rise and sediment supply reduction after the closure of the Alqueva Dam, the most plausible sets of parameter values for the Guadiana Estuary are N = 1.8 and f = 0.8f0, or N = 2 and f = f0, where f0 is the empirically estimated value. For these sets of parameter values, the relative errors in SSE change did not exceed ±20% in 73% of simulation cells in the studied area. Such a limit of accuracy can be acceptable for an idealized modelling of coastal evolution in response to uncertain sea-level rise scenarios in the context of reduced sediment supply due to flow regulation. Therefore, the idealized but cost-effective HESM model will be suitable for estimating the morphological impacts of sea-level rise on estuarine systems on a decadal timescale.

Vertical distribution of potentially toxic elements in sediments impacted by intertidal geothermal hot springs (Bahia Concepcion, Gulf of California)

NASA Astrophysics Data System (ADS)

Leal-Acosta, M. L.; Shumilin, E.

2016-12-01

The intertidal geothermal hot springs (GHS) in Bahia Concepcion, Gulf of California are the source of potentially toxic elements to the adjacent marine environment surrounded by mangroves trees. The anoxic sediments enriched in organic carbon accumulate As, Hg and other heavy metals that can be bioavailable for the biota. To know the vertical distribution of these elements the geochemistry of a short sediment core was carried out. It was collected in June, 2010 in the mangrove area near to GHS (1 m) during a low tide, pushing manually a polypropylene tube into the sediments. The extracted sediment core was cut with plastic knife on 1 cm thick sub-samples, stored in plastic bags and transported on ice to the laboratory. The major and trace elements contents were determinate by ICP-MS after total digestion with stronger acids (HClO4-HNO3-HCl-HF). Certificate reference materials were used for the quality control of the method obtaining good recoveries for most of the elements (80-105%). The sediment core had high maximum contents of CaCO3 (70%) and total organic carbon (12%). The concentration of Hg along the core ranges from 650 to 74300 mg kg-1 and had more than three orders of magnitude above the reference values of 40 mg kg-1 for the Upper Continental Crust (UCC)1. In contrast, As ranges from 12 to 258 mg kg-1 resulting in more than one order of magnitude respect to UCC1 (1.7 mg kg-1). Similar pattern result for Mn, Cu, Pb, and Zn with the maximum values of 3200 mg kg-1, 42 mg kg-1, 12.4 mg kg-1, 71 mg kg-1 respectively that coincide with the maximum for As at the same core depth (4 cm). The Ca, Li, Co, Sb, U, and Mg also show high contents in comparison with the UCC1reference values. The maximum contents of Mo and Cd coincide with maximum concentration of sulfur (2%) at 6 to 8 cm. The enrichment factor calculated using Al as normalizing element showed Cd (7-280), As (26-329) and Hg (23-1196) as highly enriched mainly in the first centimeters of the sediment core. 1 Wedephol (1995)

Biota: sediment partitioning of aluminium smelter related PAHs and pulp mill related diterpenes by intertidal clams at Kitimat, British Columbia.

PubMed

Yunker, Mark B; Lachmuth, Cara L; Cretney, Walter J; Fowler, Brian R; Dangerfield, Neil; White, Linda; Ross, Peter S

2011-09-01

The question of polycyclic aromatic hydrocarbon (PAH) bioavailability and its relationship to specific PAH sources with different PAH binding characteristics is an important one, because bioavailability drives PAH accumulation in biota and ultimately the biochemical responses to the PAH contaminants. The industrial harbour at Kitimat (British Columbia, Canada) provides an ideal location to study the bioavailability and bioaccumulation of sediment hydrocarbons to low trophic level biota. Samples of soft shell clams (Mya arenaria) and intertidal sediment collected from multiple sites over six years at various distances from an aluminium smelter and a pulp and paper mill were analysed for 106 PAHs, plant diterpenes and other aromatic fraction hydrocarbons. Interpretation using PAH source ratios and multivariate data analysis reveals six principal hydrocarbon sources: PAHs in coke, pitch and emissions from anode combustion from the aluminium smelter, vascular plant terpenes and aromatised terpenes from the pulp and paper mill, petroleum PAHs from shipping and other anthropogenic activities and PAHs from natural plant detritus. Harbour sediments predominantly contain either pitch or pyrogenic PAHs from the smelter, while clams predominantly contain plant derived PAHs and diterpenes from the adjacent pulp mill. PAHs from the smelter have low bioavailability to clams (Biota-Sediment Accumulation Factors; BSAFs <1 for pitch and coke; <10 for anode combustion, decreasing to ∼0.1 for the mass 300 and 302 PAHs), possibly due to binding to pitch or soot carbon matrices. Decreases in PAH isomer ratios between sediments and clams likely reflect a combination of variation in uptake kinetics of petroleum PAHs and compound specific metabolism, with the importance of petroleum PAHs decreasing with increasing molecular weight. Plant derived compounds exhibit little natural bioaccumulation at reference sites, but unsaturated and aromatised diterpenes released from resins by industrial pulping processes are readily accumulated by the clams (BSAFs >500). Thus while most of the smelter associated PAHs in sediments may not be bioavailable to benthic organisms, the plant terpenes (including retene, totarol, ferruginol, manool, dehydroabietane and other plant terpenes that form the chemical defence mechanism of conifers) released by pulp mills are bioavailable and possess demonstrated toxic properties. The large scale release of plant terpenes by some of the many pulp mills located in British Columbia and elsewhere represents a largely undocumented risk to aquatic biota. Copyright © 2011 Elsevier Ltd. All rights reserved.

Tidal and meteorological forcing of sediment transport in tributary mudflat channels.

PubMed

Ralston, David K; Stacey, Mark T

2007-06-01

Field observations of flow and sediment transport in a tributary channel through intertidal mudflats indicate that suspended sediment was closely linked to advection and dispersion of a tidal salinity front. During calm weather when tidal forcing was dominant, high concentrations of suspended sediment advected up the mudflat channel in the narrow region between salty water from San Francisco Bay and much fresher runoff from the small local watershed. Salinity and suspended sediment dispersed at similar rates through each tidal inundation, such that during receding ebbs the sediment pulse had spread spatially and maximum concentrations had decreased. Net sediment transport was moderately onshore during the calm weather, as asymmetries in stratification due to tidal straining of the salinity front enhanced deposition, particularly during weaker neap tidal forcing. Sediment transport by tidal forcing was periodically altered by winter storms. During storms, strong winds from the south generated wind waves and temporarily increased suspended sediment concentrations. Increased discharge down the tributary channels due to precipitation had more lasting impact on sediment transport, supplying both buoyancy and fine sediment to the system. Net sediment transport depended on the balance between calm weather tidal forcing and perturbations by episodic storms. Net transport in the tributary channel was generally off-shore during storms and during calm weather spring tides, and on-shore during calm weather neap tides.

Tidal and meteorological forcing of sediment transport in tributary mudflat channels

PubMed Central

Ralston, David K.; Stacey, Mark T.

2011-01-01

Field observations of flow and sediment transport in a tributary channel through intertidal mudflats indicate that suspended sediment was closely linked to advection and dispersion of a tidal salinity front. During calm weather when tidal forcing was dominant, high concentrations of suspended sediment advected up the mudflat channel in the narrow region between salty water from San Francisco Bay and much fresher runoff from the small local watershed. Salinity and suspended sediment dispersed at similar rates through each tidal inundation, such that during receding ebbs the sediment pulse had spread spatially and maximum concentrations had decreased. Net sediment transport was moderately onshore during the calm weather, as asymmetries in stratification due to tidal straining of the salinity front enhanced deposition, particularly during weaker neap tidal forcing. Sediment transport by tidal forcing was periodically altered by winter storms. During storms, strong winds from the south generated wind waves and temporarily increased suspended sediment concentrations. Increased discharge down the tributary channels due to precipitation had more lasting impact on sediment transport, supplying both buoyancy and fine sediment to the system. Net sediment transport depended on the balance between calm weather tidal forcing and perturbations by episodic storms. Net transport in the tributary channel was generally off-shore during storms and during calm weather spring tides, and on-shore during calm weather neap tides. PMID:21499572

Sediment reworking by a polychaete, Perinereis aibuhitensis, in the intertidal sediments of the Gomso Bay, Korea

NASA Astrophysics Data System (ADS)

Koo, Bon Joo; Seo, Jaehwan

2017-12-01

Bioturbation, especially sediment reworking by the activities of macroinvertebrates, such as feeding and burrowing, is one of the major processes that affect the physical, chemical, and biological characteristics of marine sediments. Given the importance of sediment reworking, this study was designed to evaluate the sediment reworking rate of a polychaete, Perinereis aibuhitensis, which is dominant in the upper tidal flats on the west coast of Korea, based on quantification of pellet production during spring and fall surveys. The density of individuals was higher in fall than in spring, whereas, due to a difference in the proportion of adults between the two seasons, the morphometric dimensions of the worm and its pellets were significantly longer and heavier in the spring. Hourly pellet production per inhabitant and density were closely related, with pellet production gradually decreasing as density increased. Daily pellet production was much higher in spring than in fall, mostly due to an increase in daytime production. The sediment reworking rate of Perinereis was similar in the two seasons in which observations were made and depended on its density and the sediment reworking rate per individual. The overall sediment reworking rate of Perinereis was 31 mm yr-1 based on its density in the study area.

Kite aerial photography for low-cost, ultra-high spatial resolution multi-spectral mapping of intertidal landscapes.

PubMed

Bryson, Mitch; Johnson-Roberson, Matthew; Murphy, Richard J; Bongiorno, Daniel

2013-01-01

Intertidal ecosystems have primarily been studied using field-based sampling; remote sensing offers the ability to collect data over large areas in a snapshot of time that could complement field-based sampling methods by extrapolating them into the wider spatial and temporal context. Conventional remote sensing tools (such as satellite and aircraft imaging) provide data at limited spatial and temporal resolutions and relatively high costs for small-scale environmental science and ecologically-focussed studies. In this paper, we describe a low-cost, kite-based imaging system and photogrammetric/mapping procedure that was developed for constructing high-resolution, three-dimensional, multi-spectral terrain models of intertidal rocky shores. The processing procedure uses automatic image feature detection and matching, structure-from-motion and photo-textured terrain surface reconstruction algorithms that require minimal human input and only a small number of ground control points and allow the use of cheap, consumer-grade digital cameras. The resulting maps combine imagery at visible and near-infrared wavelengths and topographic information at sub-centimeter resolutions over an intertidal shoreline 200 m long, thus enabling spatial properties of the intertidal environment to be determined across a hierarchy of spatial scales. Results of the system are presented for an intertidal rocky shore at Jervis Bay, New South Wales, Australia. Potential uses of this technique include mapping of plant (micro- and macro-algae) and animal (e.g. gastropods) assemblages at multiple spatial and temporal scales.

Kite Aerial Photography for Low-Cost, Ultra-high Spatial Resolution Multi-Spectral Mapping of Intertidal Landscapes

PubMed Central

Bryson, Mitch; Johnson-Roberson, Matthew; Murphy, Richard J.; Bongiorno, Daniel

2013-01-01

Intertidal ecosystems have primarily been studied using field-based sampling; remote sensing offers the ability to collect data over large areas in a snapshot of time that could complement field-based sampling methods by extrapolating them into the wider spatial and temporal context. Conventional remote sensing tools (such as satellite and aircraft imaging) provide data at limited spatial and temporal resolutions and relatively high costs for small-scale environmental science and ecologically-focussed studies. In this paper, we describe a low-cost, kite-based imaging system and photogrammetric/mapping procedure that was developed for constructing high-resolution, three-dimensional, multi-spectral terrain models of intertidal rocky shores. The processing procedure uses automatic image feature detection and matching, structure-from-motion and photo-textured terrain surface reconstruction algorithms that require minimal human input and only a small number of ground control points and allow the use of cheap, consumer-grade digital cameras. The resulting maps combine imagery at visible and near-infrared wavelengths and topographic information at sub-centimeter resolutions over an intertidal shoreline 200 m long, thus enabling spatial properties of the intertidal environment to be determined across a hierarchy of spatial scales. Results of the system are presented for an intertidal rocky shore at Jervis Bay, New South Wales, Australia. Potential uses of this technique include mapping of plant (micro- and macro-algae) and animal (e.g. gastropods) assemblages at multiple spatial and temporal scales. PMID:24069206

A method for measuring vertical accretion, elevation, and compaction of soft, shallow-water sediments

USGS Publications Warehouse

Cahoon, D.R.; Marin, P.E.; Black, B.K.; Lynch, J.C.

2000-01-01

High-resolution measures of vertical accretion, elevation, and compaction of shallow-water sediments are fundamental to understanding the processes that control elevation change and the mechanisms of progradation (e.g., development of mudflats and intertidal wetlands) in coastal systems. Yet, measurements of elevation by traditional survey methods often are of low accuracy because of the compressible nature of the substrates. Nor do they provide measures of vertical accretion or sediment compaction. This paper evaluates the use in shallow-water systems of an approach designed to measure these variables in vegetated wetlands. The approach employs simultaneous measures of elevation from temporary benchmarks using a sedimentation-erosion table (SET) and vertical accretion from marker horizons with sediment cores collected with a cryogenic coring apparatus. The measures are made with a level of resolution sufficient to distinguish between the influence of surface and subsurface processes on elevation, thus providing quantitative estimates of shallow subsidence. The SET-marker horizon approach was evaluated on a developing splay created by an artificial crevasse of a distributary in the Mississippi River delta. The approach provided high-resolution measures of vertical accretion (48.3 ' 2.0 cm.) and elevation (36.7 ' 1.6 cm) over a 4-year period, with the difference between the two indicating the amount of shallow subsidence. In addition, by laying new marker horizons in later years, the approach provided rates not only of shallow subsidence (3.9 ' 0.5 cm y-1) but also compaction of newly deposited seiments (2.1 ' 0.6 cm y-1) and compaction of underlying sediments (1.8 ' 2.0 cm y-1 ) over a two-year period. Hence, the SET-marker horizon approach has widespread applicability in both emergent wetland and shallow water environments for providing high resolution measures of the processes controlling elevation change.

Tidally driven pore water exchange within offshore intertidal sandbanks: Part II numerical simulations

NASA Astrophysics Data System (ADS)

Gibbes, B.; Robinson, C.; Li, L.; Lockington, D.; Li, H.

2008-12-01

Field measurements presented by [Gibbes, B., Robinson, C., Li, L., Lockington, D.A., Carey, H., 2008. Tidally driven pore water exchange within offshore intertidal sandbanks: Part I Field measurements. Estuarine, Coastal and Shelf Science 79, pp. 121-132.] revealed a tidally driven pore water flow system within an offshore intertidal sandbank in Moreton Bay, Australia. The field data suggested that this flow system might be capable of delivering nutrients, and in particular bio-available iron, across the sediment-water interface. Bio-available iron has been implicated as a key nutrient in the growth of the toxic marine cyanobacteria Lyngbya majuscula and therefore this pore water exchange process is of interest at sites where L. majuscula blooms have been observed. In this study two-dimensional numerical simulations were used in conjunction with hydraulic data from field measurements to further investigate the tidally induced pore water flow patterns. Simulation results generally showed good agreement with the field data and revealed a more complex residual pore water flow system in the sandbank than shown by the field data. The flow system, strongly influenced by the geometry of the sandbank, was characterized by two circulation cells which resulted in pore water discharge at the bank edge and also to a permanently ponded area within the sandbank interior. Simulated discharge volumes in these two zones were in the order of 0.813 m 3 and 0.143 m 3 per meter width (along shore) of sandbank per tidal cycle at the bank edge and sandbank interior respectively. Transit times of pore water circulating through these cells were found to range from ≈ 17 days to > 60 years with an average time of 780 days. The results suggest that the tidally driven flow systems might provide a mechanism for transport of bio-available iron across the sediment-water interface. This flow could constitute a previously unrecognized source of bio-available iron for L. majuscula blooms in the Bay.

The contaminant legacy from historic coastal landfills and their potential as sources of diffuse pollution.

PubMed

O'Shea, Francis T; Cundy, Andrew B; Spencer, Kate L

2018-03-01

Prior to modern environmental regulation landfills in low-lying coastal environments were frequently constructed without leachate control, relying on natural attenuation within inter-tidal sediments to dilute and disperse contaminants reducing environmental impact. With sea level rise and coastal erosion these sites may now pose a pollution risk, yet have received little investigation. This work examines the extent of metal contamination in saltmarsh sediments surrounding a historic landfill in the UK. Patterns of sediment metal data suggest typical anthropogenic pollution chronologies for saltmarsh sediments in industrialised nations. However, many metals were also enriched at depth in close proximity to the landfill boundary and are indicative of a historical leachate plume. Though this total metal load is low, e.g., c. 1200 and 1650kg Pb and Zn respectively, with >1000 historic landfills on flood risk or eroding coastlines in the UK this could represent a significant, yet under-investigated, source of diffuse pollution. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Reciprocal experimental transplantations to assess effects of organic enrichment on the recolonization of benthic macrofauna in a subtropical estuary.

PubMed

Gern, Fabiana Regina; Lana, Paulo da Cunha

2013-02-15

Coastal benthic habitats are usually in a state of continuous recolonization as a consequence of natural disturbances or human activities. Recolonization patterns can be strongly affected by the quality of the sediment. We evaluated herein the macrobenthic recolonization of organically enriched sediments through a manipulative experiment involving reciprocal transplants between contaminated and non-contaminated intertidal areas. Regardless of the experimental treatments, the density of the polychaete Capitella sp. was extremely high in the contaminated area as well as the density of the gastropod Cylichna sp. in the non-contaminated area. We rejected the hypothesis that differences in sediment quality would determine macrofaunal recolonization at least in the considered scales of space in meters and time in weeks. The recolonization process in a subtropical estuarine environment was strongly dependent on the migration of adults present in the sediments adjacent to the experimental units. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effect of nutrient enrichment on the source and composition of sediment organic carbon in tropical seagrass beds in the South China Sea.

PubMed

Liu, Songlin; Jiang, Zhijian; Zhang, Jingping; Wu, Yunchao; Lian, Zhonglian; Huang, Xiaoping

2016-09-15

To assess the effect of nutrient enrichment on the source and composition of sediment organic carbon (SOC) beneath Thalassia hemprichii and Enhalus acoroides in tropical seagrass beds, Xincun Bay, South China Sea, intertidal sediment, primary producers, and seawater samples were collected. No significant differences on sediment δ(13)C, SOC, and microbial biomass carbon (MBC) were observed between T. hemprichii and E. acoroides. SOC was mainly of autochthonous origin, while the contribution of seagrass to SOC was less than that of suspended particulate organic matter, macroalgae and epiphytes. High nutrient concentrations contributed substantially to SOC of seagrass, macroalgae, and epiphytes. The SOC, MBC, and MBC/SOC ratio in the nearest transect to fish farming were the highest. This suggested a more labile composition of SOC and shorter turnover times in higher nutrient regions. Therefore, the research indicates that nutrient enrichment could enhance plant-derived contributions to SOC and microbial use efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recent benthic foraminifera and sedimentary facies from mangrove swamps and channels of Abu Dhabi (United Arab Emirates)

NASA Astrophysics Data System (ADS)

Fiorini, Flavia; Odeh, Weaam A. S. Al; Lokier, Stephen W.; Paul, Andreas

2016-04-01

Zonation of Recent mangrove environments can be defined using benthic foraminifera, however, little is known about foraminifera from mangrove environments of the Arabian Gulf. The objective of this study is to produce a detailed micropaleontological and sedimentological analysis to identify foraminiferal associations in several coastline environments (mangrove swamps and channels) located on the eastern side of Abu Dhabi Island (UAE). Detailed sediment sampling collection in mangal environments of Eastern Abu Dhabi was carried out to assess the distribution of living and dead benthic foraminifera in different sedimentary facies in the mangal and in the surrounding area comprising natural environments of the upper and lower intertidal area (mud flats and channels) and areas modified by anthropogenic activities (dredged channels). The fine-grain sediments collected near mangrove (Avicenna marina) roots presented a high abundance of living and dead foraminifera tests. The assemblages in these samples show very low diversity and are almost entirely constituted of small-sized opportunistic species belonging to the genera Ammonia and Elphidium. In particular: • Samples collected on the mud flat and in ponds at the margin of the channel show a foraminiferal assemblage characterised by abundant foraminifera belonging to the genera Ammonia, Elphidium, Triloculina, Quinqueloculina, Peneroplis and Spirolina. • Samples collected in the lower (wet) intertidal area close to Avicenna marina roots, presented a low-diversity assemblage mostly comprising opportunistic foraminifera of the genera Ammonia and Elphidium along with rare miliolidae. • Samples from the upper intertidal area (dry) close to Avicenna marina roots, produced an assemblage exclusively composed of small-sized opportunistic Ammonia and Elphidium, together with abundant specimens belonging to the genera Trochammina. Throchammina specimens have not been previously recorded from Recent sedimentary samples of the coastline environments of the Arabian Gulf. The samples collected in the higher energy settings (channels) were characterised by a very low abundance of foraminiferal tests, no or rare living forms were found in the coarser grained facies. Most of the samples collected in the dredged channels were barren. The distribution of Recent benthic foraminifera from mangrove environment of the Abu Dhabi region present a powerful tool for constructing zonation of marine coastline environments and can be employed as a modern analogue for interpreting the depositional environment of ancient coastline sediments.

The effect of wind waves on spring-neap variations in sediment transport in two meso-tidal estuarine basins with contrasting fetch

NASA Astrophysics Data System (ADS)

Hunt, Stephen; Bryan, Karin R.; Mullarney, Julia C.

2017-03-01

Higher-energy episodic wind-waves can substantially modify estuarine morphology over short timescales which are superimposed on lower-energy but long-term tidal asymmetry effects. Theoretically, wind waves and tidal currents change the morphology through their combined influence on the asymmetry between bed shear stress, τmax, on the flood and ebb tide, although the relative contribution of such wind-wave events in shaping the long-term morphological evolution in real estuaries is not well known. If the rising tide reaches sufficiently high water depths, τmax decreases as water depth increases because of the depth attenuation of wave orbital velocities. However, this effect is opposed by the increase in τmax associated with the longer fetch occurring at high tide, which allows the generation of larger waves. Additionally, these effects are superimposed on the spring-neap variations in current associated with changes to tidal range. By comparing two mesotidal basins in the same dendritic estuary, one with a large fetch aligned with the prevailing wind direction and one with only a small fetch, we show that for a sufficiently large fetch even the small and frequently occurring wind events are able to create waves that are capable of changing the morphology ('morphologically significant'). Conversely, in the basin with reduced fetch, these waves are generated less frequently and therefore are of reduced morphological significance. Here, we find that although tidal current should be stronger during spring tides and alter morphology more, on average the reduced fetch and increased water depth during spring tides mean that the basin-averaged intertidal τmax is similar during both spring and neap tides. Moreover, in the presence of wind waves, the duration of slack water is reduced during neap tides relative to spring tides, resulting in a reduced chance for accretion during neap tides. Finally, τmax is lower in the subtidal channels during neaps than springs but of a similar magnitude over the intertidal areas, and so sediment is more likely to be advected from the intertidal regions during neap tides rather than springs. This spring-neap cycle in sediment transport potential is in sharp contrast to that found previously in microtidal wave-dominated environments, where spring tides are expected to enhance erosion.

Grounding of the Bahia Paraiso at Arthur Harbor, Antarctica. 1. Distribution and fate of oil spill related hydrocarbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kennicutt, M.C. II; Sweet, S.T.; Fraser, W.R.

1991-03-01

In January to March 1989 water, organisms, and sediments within a 2-mile radius of Arthur Harbor were contaminated with an estimated 600,000 L of petroleum spilled by the Bahia Paraiso. All components of the ecosystem were contaminated to varying degrees during the spill, including birds, limpets, macroalgae, clams, bottom-feeding fish, and sediments. The high-energy environment, the relatively small volume of material released, and the volatility of the released product all contributed to limiting toxic effects in time and space. The most effective removal processes were evaporation, dilution, winds, and currents. Sedimentation, biological uptake, microbial oxidation, and photooxidation accounted for removalmore » of only a minor portion of the spill. One year after the spill several areas still exhibited contamination. Subtidal sediments and the more distant intertidal locations were devoid of detectable PAH contaminants whereas sediments near the docking facility at Palmer Station continued to reflect localized nonspill-related activities in the area. Arthur Harbor and adjacent areas continue to be chronically exposed to low-level petroleum contamination emanating from the Bahia Paraiso.« less

Modelling reactive transport in a phosphogypsum dump, Venezia, Italia

NASA Astrophysics Data System (ADS)

Calcara, Massimo; Borgia, Andrea; Cattaneo, Laura; Bartolo, Sergio; Clemente, Gianni; Glauco Amoroso, Carlo; Lo Re, Fabio; Tozzato, Elena

2013-04-01

We develop a reactive-transport porous media flow model for a phosphogypsum dump located on the intertidal deposits of the Venetian Lagoon: 1. we construct a complex conceptual and geologic model from field data using the GMS™ graphical user interface; 2. the geological model is mapped onto a rectangular MODFLOW grid; 3. using the TMT2 FORTRAN90 code we translate this grid into the MESH, INCON and GENER input files for the TOUGH2 series of codes; 4. we run TOUGH-REACT to model flow and reactive transport in the dump and the sediments below it. The model includes 3 different dump materials (phosphogypsum, bituminous and hazardous wastes) with the pores saturated by specific fluids. The sediments below the dump are formed by an intertidal sequence of calcareous sands and silts, in addition to clays and organic deposits, all of which are initially saturated with lagoon salty waters. The recharge rain-water dilutes the dump fluids. In turn, the percolates from the dump react with the underlying sediments and the sea water that saturates them. Simulation results have been compared with chemical sampled analyses. In fact, in spite of the simplicity of our model we are able to show how the pH becomes neutral at a short distance below the dump, a fact observed during aquifer monitoring. The spatial and temporal evolution of dissolution and precipitation reactions occur in our model much alike reality. Mobility of some elements, such as divalent iron, are reduced by specific and concurrent conditions of pH from near-neutrality to moderately high values and positive redox potential; opposite conditions favour mobility of potentially toxic metals such as Cr, As Cd and Pb. Vertical movement are predominant. Trend should be therefore heavily influenced by pH and Eh values. If conditions are favourable to mobility, concentration of these substances in the bottom strata could be high. However, simulation suggest that the sediments tend to reduce the transport potential of contaminants.

Aeolian sand transport over complex intertidal bar-trough beach topography

NASA Astrophysics Data System (ADS)

Anthony, Edward J.; Ruz, Marie-Hélène; Vanhée, Stéphane

2009-04-01

Aeolian sand transport on macrotidal beaches with complex intertidal bar-trough topography (ridge-and-runnel beaches) was assessed from experiments in northern France that involved measurements of wind speed, saltation, surface moisture contents, and rates of sand trapping across surveyed portions of the upper beach profile. Beaches exhibiting intertidal bars and troughs are much more complex, topographically, than simple reflective or dissipative beaches. Furthermore, the intertidal bar-trough morphology commonly exhibits strong cross-shore variations in the moisture contents of the beach surface and in patterns of bedform development. The results of four 30-minute experiments, conducted along topographically surveyed portions of the upper beach-dune toe profile, show that troughs act as extremely efficient sand interceptors, because of their permanently saturated state, which also inhibits sand mobilisation. Troughs, thus, limit or segment the dry fetch during conditions of intermittent saltation. Flow lines, inferred from the wind profiles, suggest that complex interactions at the boundary layer are generated by the bar-trough topography. Troughs systematically appear to be characterised by air expansion, while bar faces generate ramp wind acceleration for onshore winds, and sometimes immediate downwind deceleration for offshore winds. These effects may also contribute to cross-shore variations in the rates of sand trapping. Finally, a simple conceptual model of effective fetch development, integrating the effects of the spring-neap tidal range and of gross bar-trough morphological variability over time, is proposed for bar-trough beaches. The model highlights the key theme of fetch segmentation induced by cross-shore differentiation in the moisture contents of the beach surface hinged on the complex topography of multiple bars and troughs.

On the ecogeomorphological feedbacks that control tidal channel network evolution in a sandy mangrove setting

PubMed Central

van Maanen, B.; Coco, G.; Bryan, K. R.

2015-01-01

An ecomorphodynamic model was developed to study how Avicennia marina mangroves influence channel network evolution in sandy tidal embayments. The model accounts for the effects of mangrove trees on tidal flow patterns and sediment dynamics. Mangrove growth is in turn controlled by hydrodynamic conditions. The presence of mangroves was found to enhance the initiation and branching of tidal channels, partly because the extra flow resistance in mangrove forests favours flow concentration, and thus sediment erosion in between vegetated areas. The enhanced branching of channels is also the result of a vegetation-induced increase in erosion threshold. On the other hand, this reduction in bed erodibility, together with the soil expansion driven by organic matter production, reduces the landward expansion of channels. The ongoing accretion in mangrove forests ultimately drives a reduction in tidal prism and an overall retreat of the channel network. During sea-level rise, mangroves can potentially enhance the ability of the soil surface to maintain an elevation within the upper portion of the intertidal zone, while hindering both the branching and headward erosion of the landward expanding channels. The modelling results presented here indicate the critical control exerted by ecogeomorphological interactions in driving landscape evolution. PMID:26339195

Shoreline ecology program for Prince William Sound, Alaska, following the Exxon Valdez oil spill. Part 3: Biology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilfillan, E.S.; Page, D.S.; Harner, E.J.

1995-12-31

This study describes the biological results of a comprehensive shoreline ecology program designed to assess ecological recovery in Prince William Sound following the Exxon Valdez oil spill on march 24, 1989. The program is an application of the ``Sediment Quality Triad`` approach, combining chemical, toxicological, and biological measurements. The study was designed so that results could be extrapolated to the entire spill zone in Prince William Sound. The spill affected four major shoreline habitat types in Prince William Sound: pebble/gravel, boulder/cobble, sheltered bedrock, and exposed bedrock. The study design had two components: (1) one-time stratified random sampling at 64 sitesmore » representing four habitats and four oiling levels (including unoiled reference sites) and (2) periodic sampling at 12 nonrandomly chosen sites that included some of the most heavily oiled locations in the sound. Biological communities on rock surfaces and in intertidal and shallow subtidal sediments were analyzed for differences resulting from to oiling in each of 16 habitat/tide zone combinations. Statistical methods included univariate analyses of individual species abundances and community parameter variables (total abundance, species richness, and Shannon diversity), and multivariate correspondence analysis of community structure. 58 refs., 13 figs., 9 tabs.« less

Two Genera of Magnetococci with Bean-like Morphology from Intertidal Sediments of the Yellow Sea, China

PubMed Central

Zhang, Wen-Yan; Zhou, Ke; Pan, Hong-Miao; Yue, Hai-Dong; Jiang, Ming

2012-01-01

Magnetotactic bacteria have the unique capacity of being able to swim along geomagnetic field lines. They are Gram-negative bacteria with diverse morphologies and variable phylogenetic relatedness. Here, we describe a group of uncultivated marine magnetococci collected from intertidal sediments of Huiquan Bay in the Yellow Sea. They were coccoid-ovoid in morphology, with an average size of 2.8 ± 0.3 μm by 2.0 ± 0.2 μm. Differential interference contrast microscopy, fluorescence microscopy, and transmission electron microscopy revealed that each cell was apparently composed of two hemispheres. The cells synthesized iron oxide-type magnetosomes that clustered on one side of the cell at the interface between the two hemispheres. In some cells two chains of magnetosomes were observed across the interface. Each cell had two bundles of flagella enveloped in a sheath and displayed north-seeking helical motion. Two 16S rRNA gene sequences having 91.8% identity were obtained, and their authenticity was confirmed by fluorescence in situ hybridization. Phylogenetic analysis revealed that the magnetococci are affiliated with the Alphaproteobacteria and are most closely related to two uncultured magnetococci with sequence identities of 92.7% and 92.4%, respectively. Because they display a >7% sequence divergence to all bacteria reported, the bean-like magnetococci may represent two novel genera. PMID:22660708

Food supply and size class depending variations in phytodetritus intake in the benthic foraminifer Ammonia tepida.

PubMed

Wukovits, Julia; Bukenberger, Patrick; Enge, Annekatrin Julie; Gerg, Maximillian; Wanek, Wolfgang; Watzka, Margarete; Heinz, Petra

2018-04-13

Ammonia tepida is a common and abundant benthic foraminifer in intertidal mudflats. Benthic foraminifera are primary consumers and detritivores and act as key players in sediment nutrient fluxes. In this study, laboratory feeding experiments using isotope-labeled phytodetritus were carried out with A. tepida collected at the German Wadden Sea, to investigate the response of A. tepida to varying food supply. Feeding mode (single pulse, constant feeding; different incubation temperatures) caused strong variations in cytoplasmic carbon and nitrogen cycling, suggesting generalistic adaptations to variations in food availability. To study the influence of intraspecific size to foraminiferal carbon and nitrogen cycling, three size fractions (125-250 µm, 250-355 µm, >355 µm) of A. tepida specimens were separated. Small individuals showed higher weight specific intake for phytodetritus, especially for phytodetrital nitrogen, highlighting that size distribution within foraminiferal populations is relevant to interpret foraminiferal carbon and nitrogen cycling. These results were used to extrapolate the data to natural populations of living A. tepida in sediment cores, demonstrating the impact of high abundances of small individuals on phytodetritus processing and nutrient cycling. It is estimated that at high abundances of individuals in the 125-250 µm size fraction, Ammonia populations can account for more than 11% of phytodetritus processing in intertidal benthic communities. © 2018. Published by The Company of Biologists Ltd.

Dynamic factor analysis of long-term growth trends of the intertidal seagrass Thalassia hemprichii in southern Taiwan

NASA Astrophysics Data System (ADS)

Kuo, Yi-Ming; Lin, Hsing-Juh

2010-01-01

We examined environmental factors which are most responsible for the 8-year temporal dynamics of the intertidal seagrass Thalassia hemprichii in southern Taiwan. A dynamic factor analysis (DFA), a dimension-reduction technique, was applied to identify common trends in a multivariate time series and the relationships between this series and interacting environmental variables. The results of dynamic factor models (DFMs) showed that the leaf growth rate of the seagrass was mainly influenced by salinity (Sal), tidal range (TR), turbidity ( K), and a common trend representing an unexplained variability in the observed time series. Sal was the primary variable that explained the temporal dynamics of the leaf growth rate compared to TR and K. K and TR had larger influences on the leaf growth rate in low- than in high-elevation beds. In addition to K, TR, and Sal, UV-B radiation (UV-B), sediment depth (SD), and a common trend accounted for long-term temporal variations of the above-ground biomass. Thus, K, TR, Sal, UV-B, and SD are the predominant environmental variables that described temporal growth variations of the intertidal seagrass T. hemprichii in southern Taiwan. In addition to environmental variables, human activities may be contributing to negative impacts on the seagrass beds; this human interference may have been responsible for the unexplained common trend in the DFMs. Due to successfully applying the DFA to analyze complicated ecological and environmental data in this study, important environmental variables and impacts of human activities along the coast should be taken into account when managing a coastal environment for the conservation of intertidal seagrass beds.

Modelling the effects and economics of managed realignment on the cycling and storage of nutrients, carbon and sediments in the Blackwater estuary UK

NASA Astrophysics Data System (ADS)

Shepherd, D.; Burgess, D.; Jickells, T.; Andrews, J.; Cave, R.; Turner, R. K.; Aldridge, J.; Parker, E. R.; Young, E.

2007-07-01

A hydrodynamic model is developed for the Blackwater estuary (UK) and used to estimate nitrate removal by denitrification. Using the model, sediment analysis and estimates of sedimentation rates, we estimate changes in estuarine denitrification and intertidal carbon and nutrient storage and associated value of habitat created under a scenario of extensive managed realignment. We then use this information, together with engineering and land costs, to conduct a cost benefit analysis of the managed realignment. This demonstrates that over a 50-100 year timescale the value of the habitat created and carbon buried is sufficient to make the large scale managed realignment cost effective. The analysis reveals that carbon and nutrient storage plus habitat creation represent major and quantifiable benefits of realignment. The methodology described here can be readily transferred to other coastal systems.

Distribution, enrichment and accumulation of heavy metals in coastal sediments of Alang-Sosiya ship scrapping yard, India.

PubMed

Reddy, M Srinivasa; Basha, Shaik; Sravan Kumar, V G; Joshi, H V; Ramachandraiah, G

2004-06-01

Since its inception in 1982, the Alang-Sosiya yard has become the largest ship scrapping works in the world. Several hundreds of ships arrive every year. The degree of heavy metal contamination has been studied in bulk and fine sediments from the intertidal zone of this ship scrapping yard, two stations, one on either side at 5 km distance and one reference station 60 km distance near Mahuva, towards the south. The samples have been subjected to a total digestion technique and analysed for elements: Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Zn and Al, and %TOC. The absolute metal concentrations reflected variations in BF and FF sediment samples with organic matter content. Enrichment factors (EF) and geoaccumulation indices (Igeo) have been calculated and the relative contamination levels are assessed at these sites. At Alang-Sosiya, the enrichment of heavy metals has been observed to be relatively high.

Storm impacts and shoreline recovery: Mechanisms and controls in the southern North Sea

NASA Astrophysics Data System (ADS)

Brooks, S. M.; Spencer, T.; Christie, E. K.

2017-04-01

Storm impacts play a significant role in shoreline dynamics on barrier coastlines. Furthermore, inter-storm recovery is a key parameter determining long-term coastal resilience to climate change, storminess variability and sea level rise. Over the last decade, four extreme storms, with strong energetic waves and high still water levels resulting from high spring tides and large skew surge residuals, have impacted the shoreline of the southern North Sea. The 5th December 2013 storm, with the highest run-up levels recorded in the last 60 years, resulted in large sections of the frontline of the North Norfolk coast being translated inland by over 10 m. Storms in March and November 2007 also generated barrier scarping and shoreline retreat, although not on the scale of 2013. Between 2008 and 2013, a calm period, recovery dominated barrier position and elevation but was spatially differentiated alongshore. For one study area, Scolt Head Island, no recovery was seen; this section of the coast is being reset episodically landwards during storms. By contrast, the study area at Holkham Bay showed considerable recovery between 2008 and 2013, with barrier sections developing seaward through foredune recovery. The third study area, Brancaster Bay, showed partial recovery in barrier location and elevation. Results suggest that recovery is promoted by high sediment supply and onshore intertidal bar migration, at rates of 40 m a- 1. These processes bring sand to elevations where substrate drying enables aeolian processes to entrain and transport sand from upper foreshores to foredunes. We identify three potential sediment transport pathways that create a region of positive diffusivity at Holkham Bay. During calm periods, a general westward movement of sediment from the drift divide at Sheringham sources the intertidal bar and foredune development at Holkham Bay. However, during and following storms the drift switches to eastward, not only on the beach itself but also below the - 7 m isobath. Sediment from the eroding barrier at Brancaster Bay, and especially Scolt Head Island, also sources the sediment sink of Holkham Bay. Knowledge of foredune growth and barrier recovery in natural systems are vital aspects of future coastal management planning with accelerated sea-level rise and storminess variability.

Deposition, erosion, and bathymetric change in South San Francisco Bay: 1858-1983

USGS Publications Warehouse

Foxgrover, Amy C.; Higgins, Shawn A.; Ingraca, Melissa K.; Jaffe, Bruce E.; Smith, Richard E.

2004-01-01

Since the California Gold Rush of 1849, sediment deposition, erosion, and the bathymetry of South San Francisco Bay have been altered by both natural processes and human activities. Historical hydrographic surveys can be used to assess how this system has evolved over the past 150 years. The National Ocean Service (NOS) (formerly the United States Coast and Geodetic Survey (USCGS), collected five hydrographic surveys of South San Francisco Bay from 1858 to 1983. Analysis of these surveys enables us to reconstruct the surface of the bay floor for each time period and quantify spatial and temporal changes in deposition, erosion, and bathymetry. The creation of accurate bathymetric models involves many steps. Sounding data was obtained from the original USCGS and NOS hydrographic sheets and were supplemented with hand drawn depth contours. Shorelines and marsh areas were obtained from topographic sheets. The digitized soundings and shorelines were entered into a Geographic Information System (GIS), and georeferenced to a common horizontal datum. Using surface modeling software, bathymetric grids with a horizontal resolution of 50 m were developed for each of the five hydrographic surveys. Prior to conducting analyses of sediment deposition and erosion, we converted all of the grids to a common vertical datum and made adjustments to correct for land subsidence that occurred from 1934 to 1967. Deposition and erosion that occurred during consecutive periods was then computed by differencing the corrected grids. From these maps of deposition and erosion, we calculated volumes and rates of net sediment change in the bay. South San Francisco Bay has lost approximately 90 x 106 m3 of sediment from 1858 to 1983; however within this timeframe there have been periods of both deposition and erosion. During the most recent period, from 1956 to 1983, sediment loss approached 3 x 106 m3/yr. One of the most striking changes that occurred from 1858 to 1983 was the conversion of more than 80% of the tidal marsh to salt ponds, agricultural, and urban areas. In addition, there has been a decline of approximately 40% in intertidal mud flat area. Restoration of these features will require a detailed understanding of the morphology and sediment sources of this complex system.

Intertidal sand body migration along a megatidal coast, Kachemak Bay, Alaska

USGS Publications Warehouse

Adams, P.N.; Ruggiero, P.; Schoch, G.C.; Gelfenbaum, G.

2007-01-01

Using a digital video-based Argus Beach Monitoring System (ABMS) on the north shore of Kachemak Bay in south central Alaska, we document the timing and magnitude of alongshore migration of intertidal sand bed forms over a cobble substrate during a 22-month observation period. Two separate sediment packages (sand bodies) of 1-2 m amplitude and ???200 m wavelength, consisting of well-sorted sand, were observed to travel along shore at annually averaged rates of 278 m/yr (0.76 m/d) and 250 m/ yr (0.68 m/d), respectively. Strong seasonality in migration rates was shown by the contrast of rapid winter and slow summer transport. Though set in a megatidal environment, data indicate that sand body migration is driven by eastward propagating wind waves as opposed to net westward directed tidal currents. Greatest weekly averaged rates of movement, exceeding 6 m/d, coincided with wave heights exceeding 2 m suggesting a correlation of wave height and sand body migration. Because Kachemak Bay is partially enclosed, waves responsible for sediment entrainment and transport are locally generated by winds that blow across lower Cook Inlet from the southwest, the direction of greatest fetch. Our estimates of sand body migration translate to a littoral transport rate between 4,400-6,300 m3/yr. Assuming an enclosed littoral cell, minimal riverine sediment contributions, and a sea cliff sedimentary fraction of 0.05, we estimate long-term local sea cliff retreat rates of 9-14 cm/yr. Applying a numerical model of wave energy dissipation to the temporally variable beach morphology suggests that sand bodies are responsible for enhancing wave energy dissipation by ???13% offering protection from sea cliff retreat. Copyright 2007 by the American Geophysical Union.

Influences of hydrological regime on heavy metal and salt ion concentrations in intertidal sediment from Chongming Dongtan, Changjiang River estuary, China

NASA Astrophysics Data System (ADS)

Zhao, Jiale; Gao, Xiaojiang; Yang, Jin

2017-11-01

The tidal flat along the Changjiang (Yangtze) River estuary has long been reclaimed for the agricultural purposes, with the prevailing hydrological conditions during such pedogenic transformations being of great importance to their successful development. In this study, samples of surface sediment from Chongming Dongtan, situated at the mouth of the Changjiang River estuary, were collected and analyzed in order to understand how hydrological management can influence the concentrations of heavy metals and salt ions in pore water, and chemical fractionation of heavy metals during the reclamation process. We performed a series of experiments that simulated three different hydrological regimes: permanent flooding (R1), alternative five-day periods of wetting and drying (R2), continuous field capacity (R3). Our results exhibited good Pearson correlations coefficients between heavy metals and salt ions in the pore water for both R1 and R2. In particular, the concentrations of salt ions in the pore water decreased in all three regimes, but showed the biggest decline in R2. With this R2 experiment, the periodic concentration patterns in the pore water varied for Fe and Mn, but not for Cr, Cu, Pb and Zn. Neither the fractionation of Ni nor the residual fractions of any metals changed significantly in any regime. In R1, the reducible fractions of heavy metals (Cr, Cu, Zn and Pb) in the sediment decreased, while the acid extractable fractions increased. In R2, the acid extractable and the reducible fractions of Cr, Cu, Zn and Pb both decreased, as did the oxidizable fraction of Cu. These data suggest that an alternating hydrological regime can reduce both salinity and the availability of heavy metals in sediments.

Microplastic-associated bacterial assemblages in the intertidal zone of the Yangtze Estuary.

PubMed

Jiang, Peilin; Zhao, Shiye; Zhu, Lixin; Li, Daoji

2018-05-15

Plastic trash is common in oceans. Terrestrial and marine ecosystem interactions occur in the intertidal zone where accumulation of plastic frequently occurs. However, knowledge of the plastic-associated microbial community (the plastisphere) in the intertidal zone is scanty. We used high-throughput sequencing to profile the bacterial communities attached to microplastic samples from intertidal locations around the Yangtze estuary in China. The structure and composition of plastisphere communities varied significantly among the locations. We found the taxonomic composition on microplastic samples was related to their sedimentary and aquatic origins. Correlation network analysis was used to identify keystone bacterial genera (e.g. Rhodobacterales, Sphingomonadales and Rhizobiales), which represented important microbial associations within the plastisphere community. Other species (i.e. potential pathogens) were considered as hitchhikers in the plastic attached microbial communities. Metabolic pathway analysis suggested adaptations of these bacterial assemblages to the plastic surface-colonization lifestyle. These adaptations included reduced "cell motility" and greater "xenobiotics biodegradation and metabolism." The findings illustrate the diverse microbial assemblages that occur on microplastic and increase our understanding of plastisphere ecology. Copyright © 2017 Elsevier B.V. All rights reserved.

Long-distance electron transport occurs globally in marine sediments

NASA Astrophysics Data System (ADS)

Burdorf, Laurine D. W.; Tramper, Anton; Seitaj, Dorina; Meire, Lorenz; Hidalgo-Martinez, Silvia; Zetsche, Eva-Maria; Boschker, Henricus T. S.; Meysman, Filip J. R.

2017-02-01

Recently, long filamentous bacteria have been reported conducting electrons over centimetre distances in marine sediments. These so-called cable bacteria perform an electrogenic form of sulfur oxidation, whereby long-distance electron transport links sulfide oxidation in deeper sediment horizons to oxygen reduction in the upper millimetres of the sediment. Electrogenic sulfur oxidation exerts a strong impact on the local sediment biogeochemistry, but it is currently unknown how prevalent the process is within the seafloor. Here we provide a state-of-the-art assessment of its global distribution by combining new field observations with previous reports from the literature. This synthesis demonstrates that electrogenic sulfur oxidation, and hence microbial long-distance electron transport, is a widespread phenomenon in the present-day seafloor. The process is found in coastal sediments within different climate zones (off the Netherlands, Greenland, the USA, Australia) and thrives on a range of different coastal habitats (estuaries, salt marshes, mangroves, coastal hypoxic basins, intertidal flats). The combination of a widespread occurrence and a strong local geochemical imprint suggests that electrogenic sulfur oxidation could be an important, and hitherto overlooked, component of the marine cycle of carbon, sulfur and other elements.

A siphonous morphology affects light-harvesting modulation in the intertidal green macroalga Bryopsis corticulans (Ulvophyceae).

PubMed

Giovagnetti, Vasco; Han, Guangye; Ware, Maxwell A; Ungerer, Petra; Qin, Xiaochun; Wang, Wen-Da; Kuang, Tingyun; Shen, Jian-Ren; Ruban, Alexander V

2018-06-01

The macroalga Bryopsis corticulans relies on a sustained protective NPQ and a peculiar body architecture to efficiently adapt to the extreme light changes of intertidal shores. During low tides, intertidal algae experience prolonged high light stress. Efficient dissipation of excess light energy, measured as non-photochemical quenching (NPQ) of chlorophyll fluorescence, is therefore required to avoid photodamage. Light-harvesting regulation was studied in the intertidal macroalga Bryopsis corticulans, during high light and air exposure. Photosynthetic capacity and NPQ kinetics were assessed in different filament layers of the algal tufts and in intact chloroplasts to unravel the nature of NPQ in this siphonous green alga. We found that the morphology and pigment composition of the B. corticulans body provides functional segregation between surface sunlit filaments (protective state) and those that are underneath and undergo severe light attenuation (light-harvesting state). In the surface filaments, very high and sustained NPQ gradually formed. NPQ induction was triggered by the formation of transthylakoid proton gradient and independent of the xanthophyll cycle. PsbS and LHCSR proteins seem not to be active in the NPQ mechanism activated by this alga. Our results show that B. corticulans endures excess light energy pressure through a sustained protective NPQ, not related to photodamage, as revealed by the unusually quick restoration of photosystem II (PSII) function in the dark. This might suggest either the occurrence of transient PSII photoinactivation or a fast rate of PSII repair cycle.

Sediment chemoautotrophy in the coastal ocean

NASA Astrophysics Data System (ADS)

Vasquez-Cardenas, Diana; Meysman, Filip J. R.; van Breugel, Peter; Boschker, Henricus T. S.

2016-04-01

A key process in the biogeochemistry of coastal sediments is the reoxidation of reduced intermediates formed during anaerobic mineralization which in part is performed by chemoautotrophic micro-organisms. These microbes fix inorganic carbon using the energy derived from reoxidation reactions and in doing so can fix up to 32% of the CO2 released by mineralization. However the importance and distribution of chemoautotrophy has not been systematically investigated in these environments. To address these issues we surveyed nine coastal sediments by means of bacterial biomarker analysis (phospholipid derived fatty acids) combined with stable isotope probing (13C-bicarbonate) which resulted in an almost doubling of the number of observations on coastal sedimentary chemoautotrophy. Firstly, sediment chemoautotrophy rates from this study and rates compiled from literature (0.07 to 36 mmol C m-2 d-1) showed a power-law relation with benthic oxygen uptake (3.4 to 192 mmol O2 m-2 d-1). Benthic oxygen uptake was used as a proxy for carbon mineralization to calculate the ratio of the CO2 fixed by chemoautotrophy over the total CO2 released through mineralization. This CO2 efficiency was 3% in continental shelf, 9% in nearshore and 21% in salt marsh sediments. These results suggest that chemoautotrophy plays an important role in C-cycling in reactive intertidal sediments such as salt marshes rather than in the organic-poor, permeable continental shelf sediments. Globally in the coastal ocean our empirical results show that chemoautotrophy contributes ˜0.05 Pg C y-1 which is four times less than previous estimates. Secondly, five coastal sediment regimes were linked to the depth-distribution of chemoautotrophy: 1) permeable sediments dominated by advective porewater transport, 2) bioturbated sediments, and cohesive sediments dominated by diffusive porewater transport characterized by either 3) canonical sulfur oxidation, 4) nitrate-storing Beggiatoa, or 5) electrogenic sulfur oxidation. Sediments with an O2-H2S interface exhibited highest chemoautotrophy activity in the top centimeter via canonical sulfur oxidation, whereas in the presence of electrogenic sulfur oxidation a uniform distribution of chemoautotrophy throughout the top centimeters of the sediment was evidenced. Lowest dark carbon fixation was found in permeable advective-driven sediments with deep oxygen penetration resulting in higher subsurface than surface activity. Hence, the depth-distribution of chemoautotrophy in coastal sediments varies due to several biogeochemical characteristics such as grain size, organic carbon content, presence of filamentous sulfur oxidizing bacteria, and macrofaunal activity.

Investigating the distribution and sources of organic matter in surface sediment of Coombabah Lake (Australia) using elemental, isotopic and fatty acid biomarkers

NASA Astrophysics Data System (ADS)

Dunn, R. J. K.; Welsh, D. T.; Teasdale, P. R.; Lee, S. Y.; Lemckert, C. J.; Meziane, T.

2008-10-01

Extensive physical and biological measurements were made of the surface sediments within the shallow, semi-urbanised Coombabah Lake in southern Moreton Bay, Australia. Sediment bulk parameters (C/N ratios, δ13C and δ15N) and fatty acid biomarkers were used to determine distributions and sources of organic matter in the intertidal sediments. The determination of organic matter sources within coastal and estuarine settings is important in understanding the roles of organic matter as energy and nutrient sources. Spatial variability of biomarker values within the sediments were interpreted by thematic maps employing the Krigging algorithm. Grain size analysis indicated the lake was dominated by mud (<63 μm) in the southern (landward) and sand (>63 μm) in the northern (seaward) lake regions, respectively. Surface sediment organic C and N values ranged from 0.12% to 1.76% and 0.01% to 0.12% dry weight, respectively, and C/N ratios averaged 16.3±3.19%. Sedimentary δ13C values ranged from -26.1‰ to -20.9‰, with an average value of -23.9±1.0‰. Sedimentary δ15N values ranged from +1.7‰ to +4.8‰, with an average value of +2.8±0.8‰. Bulk sediment parameters suggested that sedimentary organic matter is provided predominantly by allochthonous sources in the form of fringing mangroves. Thirty-nine individual fatty acids were identified using gas chromatography-mass spectrometry. The mean contributions of long chain fatty acids (LCFAs), polyunsaturated fatty acids (PUFAs), saturated fatty acids (SAFAs) and bacterial fatty acids (BAFAs) were, respectively, 13.9±11.4%, 7.6±4.1%, 53.6±8.6% and 18.2±4.6% of the identified fatty acid methyl esters (FAMEs), with BAFAs occurring in all sampled sediments. Fatty acid compositions varied throughout lake sediments, which indicated spatial differences in autochthonous and allochthonous organic matter sources, including terrestrial and planktonic (i.e. zooplankton, diatoms and other algal species) sources. The contribution of organic matter from shoreline mangroves was confirmed by the presence of LCFAs and 18:2 ω6 and 18:3 ω3, which are markers for mangroves in this ecosystem. BAFAs were identified in increased proportions in sediments adjacent to urban developments and dominated by mud. Grain size was identified as a dominant factor in the fatty acid compositions and contributing values to FAME pool. Spatial patterns of C/N ratios, δ13C and δ15N values, and fatty acid biomarker contributions illustrated that there is a greater contribution of autochthonous and labile organic matter to the sedimentary organic matter pool in the northern (marine entrance) sediments compared to the more allochthonous sourced organic matter of the southern region of the lake. This study details the distribution and sources of organic matter within Coombabah Lake and illustrates the usefulness of a multiple biomarker approach in discriminating organic matter sources within estuarine environments.

The macroalgal carbonate factory at a cool-to-warm temperate marine transition, Southern Australia

NASA Astrophysics Data System (ADS)

James, Noel P.; Reid, Catherine M.; Bone, Yvonne; Levings, Andrew; Malcolm, Isabelle

2013-06-01

The shallow neritic seafloor to depths of ~ 30 m along the coast of southwestern Victoria Australia, is the site of rocky reefs on volcanic and aeolianite bathymetric highs. The region, located near the warm- to cool-temperate environmental transition, is a site of prolific macroalgae (kelp) growth. Kelps are most prolific and diverse in high-energy, open-ocean environments whereas broad-leafed seagrasses, at their cold-water eastern limit, are restricted to local protected embayments. The seagrasses are reduced to one species of Amphibolis whereas the kelps are diverse and include the large intertidal bull kelp (Durvillaea), not present in warmer waters. The macroalgal forest extends from the intertidal to ~ 30 mwd (metres water depth) as a series of distinct biomes; 1) the Peritidal, 2) the Phaeophyte Forest (0-17 mwd), 3) the Rhodophyte Thicket (17-15 mwd), and 4) the Invertebrate Coppice (> 25 mwd). The Phaeophyte Forest is partitioned into a Durvillaea zone (0-2 mwd), a Phyllospora zone (2-10 mwd) and an Ecklonia zone (10-17mwd). The two major habitats within each biome comprise 1) an upward facing illuminated surface that supports a macroalgal canopy over an understorey of coralline algae and herbivorous gastropods, and 2) a separate, cryptic, shaded habitat dominated by a diverse community of filter-feeding invertebrates. These communities produce two different sediments; 1) geniculate and encrusting corallines and diverse gastropods from the upper surface, and 2) bryozoans, molluscs, barnacles, chitons, serpulids, and benthic foraminifers from the shaded, cryptic habitats. These particles are blended together with the latter becoming proportionally more abundant with increasing depth. Results of this study, when integrated with recent investigations in warm-temperate (South Australia) and cool-temperate (New Zealand) environments now define carbonate sedimentology of the macroalgal reef depositional system in this part of the northern Southern Ocean.

Spatial distributions of biogeochemical reactions in freshwater-saltwater mixing zones of sandy beach aquifers

NASA Astrophysics Data System (ADS)

Kim, K. H.; Michael, H. A.; Ullman, W. J.; Cai, W. J.

2017-12-01

Beach aquifers host biogeochemically dynamic mixing zones between fresh and saline groundwaters of contrasting origins, histories, and compositions. Seawater, driven up the beachface by waves and tides, infiltrates into the sand and meets the seaward-discharging fresh groundwater, creating and maintaining a highly reactive intertidal circulation cell well-defined by salinity. Seawater supplies oxygen and reactive carbon to the circulation cell, supporting biogeochemical reactions within the cell that transform and attenuate dissolved nutrient fluxes from terrestrial sources. We investigated the spatial distribution of chemical reaction zones within the intertidal circulation cell at Cape Shores, Lewes, Delaware. Porewater samples were collected from multi-level wells along a beach-perpendicular transect. Samples were analyzed for particulate carbon and reactive solutes, and incubated to obtain rates of oxic respiration and denitrification. High rates of oxic respiration were observed higher on the beach, in the landward freshwater-saline water mixing zone, where dissolved oxygen availability was high. Denitrification was dominant in lower areas of the beach, below the intertidal discharge point. High respiration rates did not correlate with particulate carbon concentrations entrained within porewater, suggesting that dissolved organic carbon or immobile particulate carbon trapped within the sediment can contribute to and alter bulk reactivity. A better understanding of the sources and sinks of carbon within the beach will improve our ability to predict nutrient fluxes to estuaries and oceans, aiding the management of coastal environments and ecosystems.

Effects of an oil spill on benthic community production and respiration on subtropical intertidal sandflats.

PubMed

Lee, Li-Hua; Lin, Hsing-Juh

2013-08-15

This study determined effects of an oil spill on subtropical benthic community production and respiration by monitoring CO2 fluxes in benthic chambers on intertidal sandflats during emersion before and after an accidental spill. The oil spill decreased sediment chlorophyll a concentrations, altered benthic macrofaunal community, and affected ecological functioning by suppressing or even stopping microalgal production, increasing bacterial respiration, and causing a shift from an autotrophic system to a heterotrophic system. Effects of the oil spill on the macrofauna were more severe than on benthic microalgae, and affected sedentary infauna more than motile epifauna. Despite the oil spill's impact on the benthic community and carbon metabolism, the affected area appeared to return to normal in about 23 days. Our results suggest that the prompt response of benthic metabolism to exposure to petroleum hydrocarbons can serve as a useful indicator of the impact of an oil spill. Copyright © 2013 Elsevier Ltd. All rights reserved.

Impact of flood events on macrobenthic community structure on an intertidal flat developing in the Ohta River Estuary.

PubMed

Nishijima, Wataru; Nakano, Yoichi; Nakai, Satoshi; Okuda, Tetsuji; Imai, Tsuyoshi; Okada, Mitsumasa

2013-09-15

We investigated the effects of river floods on the macrobenthic community of the intertidal flat in the Ohta River Estuary, Japan, from 2005 to 2010. Sediment erosion by flood events ranged from about 2-3 cm to 12 cm, and the salinity dropped to 0‰ even during low-intensity flood events. Cluster analysis of the macrobenthic population showed that the community structure was controlled by the physical disturbance, decreased salinity, or both. The opportunistic polychaete Capitella sp. was the most dominant species in all clusters, and populations of the long-lived polychaete Ceratonereis erythraeensis increased in years with stable flow and almost disappeared in years with intense flooding. The bivalve Musculista senhousia was also an important opportunistic species that formed mats in summer of the stable years and influenced the structure of the macrobenthic community. Our results demonstrate the substantial effects of flood events on the macrobenthic community structure. Copyright © 2013 Elsevier Ltd. All rights reserved.

Peritidal cyclic sedimentation from La Manga Formation (Oxfordian), Neuquén Basin, Mendoza, Argentina

NASA Astrophysics Data System (ADS)

Palma, Ricardo M.; Kietzmann, Diego A.; Bressan, Graciela S.; Martín-Chivelet, Javier; López-Gómez, José; Farias, María E.; Iglesias Llanos, María P.

2013-11-01

The La Manga Formation consists of marine carbonates and represents most of the sedimentary record of the Callovian-Oxfordian in the Neuquén Basin. Three localities in the southern Mendoza province were studied and their cyclicity was determined by means of facies analysis and their vertical arrangement. Facies of inner ramp, that were deposited in extremely shallow-water environments with intermittent subaerial exposures have been broken down into shallow subtidal, and intertidal-supratidal environments. Shallow subtidal facies are arranged into decimetre scale upward-shallowing cycles composed of marls, laminated or massive mudstones or bioclastic wackestones and intraclastic wackestone-packstones. Intertidal-supratidal centimetre-scale cycles consist of an upward-shallowing succession of restricted facies, overlaid by horizontal or crinkle microbial laminites, flat pebble conglomerates or breccias beds. The defined cycles show a shallowing upward trend in which the evidence of relative sea-level lowering is accepted. The interpretation of Fischer plots allowed the recognition of changes in accommodation space.

Flexibility of Physiological Traits Underlying Inter-Individual Growth Differences in Intertidal and Subtidal Mussels Mytilusgalloprovincialis

PubMed Central

Fernández-Reiriz, María José; Irisarri, Jade; Labarta, Uxio

2016-01-01

Mussel seed (Mytilusgalloprovincialis) gathered from the intertidal and subtidal environments of a Galician embayment (NW, Spain) were maintained in the laboratory during five months to select fast (F) and slow (S) growing mussels. The physiological basis underlying inter-individual growth variations were compared for F and S mussels from both origins. Fast growing seemed to be a consequence of greater energy intake (20% higher clearance and ingestion rate) and higher food absorption rate coupled with low metabolic costs. The enhanced energy absorption (around 65% higher) resulted in 3 times higher Scope for Growth in F mussels (20.5±4.9 J h−1) than S individuals (7.3±1.1 J h−1). The higher clearance rate of F mussels appears to be linked with larger gill filtration surface compared to S mussels. Intertidal mussels showed higher food acquisition and absorption per mg of organic weight (i.e. mass-specific standardization) than subtidal mussels under the optimal feeding conditions of the laboratory. However, the enhanced feeding and digestive rates were not enough to compensate for the initial differences in tissue weight between mussels of similar shell length collected from the intertidal and subtidal environments. At the end of the experiment, subtidal individuals had higher gill efficiency, which probably lead to higher total feeding and absorption rates relative to intertidal individuals. PMID:26849372

Low-Cost Ultra-High Spatial and Temporal Resolution Mapping of Intertidal Rock Platforms

NASA Astrophysics Data System (ADS)

Bryson, M.; Johnson-Roberson, M.; Murphy, R.

2012-07-01

Intertidal ecosystems have primarily been studied using field-based sampling; remote sensing offers the ability to collect data over large areas in a snapshot of time which could compliment field-based sampling methods by extrapolating them into the wider spatial and temporal context. Conventional remote sensing tools (such as satellite and aircraft imaging) provide data at relatively course, sub-meter resolutions or with limited temporal resolutions and relatively high costs for small-scale environmental science and ecology studies. In this paper, we describe a low-cost, kite-based imaging system and photogrammetric pipeline that was developed for constructing highresolution, 3D, photo-realistic terrain models of intertidal rocky shores. The processing pipeline uses automatic image feature detection and matching, structure-from-motion and photo-textured terrain surface reconstruction algorithms that require minimal human input and only a small number of ground control points and allow the use of cheap, consumer-grade digital cameras. The resulting maps combine colour and topographic information at sub-centimeter resolutions over an area of approximately 100m, thus enabling spatial properties of the intertidal environment to be determined across a hierarchy of spatial scales. Results of the system are presented for an intertidal rock platform at Cape Banks, Sydney, Australia. Potential uses of this technique include mapping of plant (micro- and macro-algae) and animal (e.g. gastropods) assemblages at multiple spatial and temporal scales.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cox, D.L.

The Berea Sandstone is a widely recognized producer of oil and gas in the Appalachian basin. Subsurface mapping, core analysis, and production data from producing wells have been evaluated in west-central West Virginia, where the Berea Sandstone represents a wide range of nearshore and coastal environments. Fluvial system deposits are found in southern Jackson County as channel sands (Gay-Fink) and adjacent deltaic facies. Coastal sediments were deposited to the north as intertidal shoals, tidal flats, and coarse-grained tidal-creek point bars. Marine shelf sands are found to the west.

Importance of biogeomorphic and spatial properties in assessing a tidal salt marsh vulnerability to sea-level rise

USGS Publications Warehouse

Thorne, Karen M.; Elliott-Fisk, Deborah L.; Wylie, Glenn D.; Perry, William M.; Takekawa, John Y.

2014-01-01

We evaluated the biogeomorphic processes of a large (309 ha) tidal salt marsh and examined factors that influence its ability to keep pace with relative sea-level rise (SLR). Detailed elevation data from 1995 and 2008 were compared with digital elevation models (DEMs) to assess marsh surface elevation change during this time. Overall, 37 % (113 ha) of the marsh increased in elevation at a rate that exceeded SLR, whereas 63 % (196 ha) of the area did not keep pace with SLR. Of the total area, 55 % (169 ha) subsided during the study period, but subsidence varied spatially across the marsh surface. To determine which biogeomorphic and spatial factors contributed to measured elevation change, we collected soil cores and determined percent and origin of organic matter (OM), particle size, bulk density (BD), and distance to nearest bay edge, levee, and channel. We then used Akaike Information Criterion (AICc) model selection to assess those variables most important to determine measured elevation change. Soil stable isotope compositions were evaluated to assess the source of the OM. The samples had limited percent OM by weight (-3, indicating that the soils had high mineral content with a relatively low proportion of pore space. The most parsimonious model with the highest AICc weight (0.53) included distance from bay's edge (i.e., lower intertidal) and distance from levee (i.e., upper intertidal). Close proximity to sediment source was the greatest factor in determining whether an area increased in elevation, whereas areas near landward levees experienced subsidence. Our study indicated that the ability of a marsh to keep pace with SLR varied across the surface, and assessing changes in elevation over time provides an alternative method to long-term accretion monitoring. SLR models that do not consider spatial variability of biogeomorphic and accretion processes may not correctly forecast marsh drowning rates, which may be especially true in modified and urbanized estuaries. In light of SLR, improving our understanding of elevation change in these dynamic marsh systems will play a crucial role in forecasting potential impacts to their sustainability and the survival of these ecosystems.

Historical flux of mercury associated with mining and industrial sources in the Marano and Grado Lagoon (northern Adriatic Sea)

NASA Astrophysics Data System (ADS)

Covelli, Stefano; Langone, Leonardo; Acquavita, Alessandro; Piani, Raffaella; Emili, Andrea

2012-11-01

The "MIRACLE" Project was established in order to assess the feasibility of clam farming and high levels of sediment mercury (Hg) contamination coexisting in the Marano and Grado Lagoon, Italy. This lagoon has been subjected to Hg input from both industrial waste (chlor-alkali plant) and long-term mining activity (Idrija mine, NW Slovenia). One of the subtasks of the "MIRACLE" Project was to determine the historical evolution of Hg accumulation in the lagoon's bottom sediments. Thirteen 1-m deep sediment cores were collected from the subtidal and intertidal zones, plus one in a saltmarsh, all of which were then analyzed for total Hg content and several physicochemical parameters. Sedimentation rate assessments were performed by measuring short-lived radionuclides (excess 210Pb and 137Cs). For most of the analyzed cores, natural background levels of Hg were observed at depths of 50-100 cm. In the eastern area, Hg contamination was found to be at its maximum level at the core top (up to 12 μg g-1) as a consequence of the long-term mining activity. The vertical distribution of Hg was related to the influence of the single-point contamination sources, whereas the grain-size variability or organic matter content seemed not to affect it. In the western area, Hg content at the surface was found not to exceed 7 μg g-1 and contamination was recorded only in the first 20-30 cm. Geochronological measurements showed that the depositional flux of Hg was influenced by anthropogenic inputs after 1800, when mining activity was more intense. After 1950, Hg in the surface sediment, most remarkable in the central-western sector, seemed to also be affected by the discharge of the Aussa River, which delivers Hg from the chlor-alkali plant. In 1996, Hg mining at Idrija ceased, however the core profiles did not show any subsequent decreasing trend in terms of Hg flux, which implies the system retaining some "memory" of contamination. Thus, in the short term, a decrease in Hg inputs into the nearby Gulf of Trieste and the lagoon seems unlikely. A preliminary rounded-down gross estimate of total Hg "trapped" in the lagoon's sediments amounted to 251 t. Such a quantity, along with the complexity of the lagoon ecosystem, suggests that an in toto reclamation of the sediments at the lagoon scale is unfeasible, both economically and environmentally.

Tracing biosignatures from the Recent to the Jurassic in sabkha-associated microbial mats

NASA Astrophysics Data System (ADS)

van der Land, Cees; Dutton, Kirsten; Andrade, Luiza; Paul, Andreas; Sherry, Angela; Fender, Tom; Hewett, Guy; Jones, Martin; Lokier, Stephen W.; Head, Ian M.

2017-04-01

Microbial mat ecosystems have been operating at the sediment-fluid interface for over 3400 million years, influencing the flux, transformation and preservation of carbon from the biosphere to the physical environment. These ecosystems are excellent recorders of rapid and profound changes in earth surface environments and biota as they often survive crisis-induced extreme paleoenvironmental conditions. Their biosignatures, captured in the preserved organic matter and the biominerals that form the microbialite rock, constitute a significant tool in understanding geobiological processes and the interactions of the microbial communities with sediments and with the prevailing physical chemical parameters, as well as the environmental conditions at a local and global scale. Nevertheless, the exact pathways of diagenetic organic matter transformation and early-lithification, essential for the accretion and preservation in the geological record as microbialites, are not well understood. The Abu Dhabi coastal sabkha system contains a vast microbial mat belt that is dominated by continuous polygonal and internally-laminated microbial mats across the upper and middle intertidal zones. This modern system is believed to be the best analogue for the Upper Jurassic Arab Formation, which is both a prolific hydrocarbon reservoir and source rock facies in the United Arab Emirates and in neighbouring countries. In order to characterise the processes that lead to the formation of microbialites we investigated the modern and Jurassic system using a multidisciplinary approach, including growth of field-sampled microbial mats under controlled conditions in the laboratory and field-based analysis of microbial communities, mat mineralogy and organic biomarker analysis. In this study, we focus on hydrocarbon biomarker data obtained from the surface of microbial mats actively growing in the intertidal zone of the modern system. By comparing these findings to data obtained from recently-buried, unlithified mats and fully lithified Jurassic mats we are able to identify those biochemical signatures of organic matter preserved in microbialites which survived diagenetic disintegration and represent the primary microbial production. Biomarkers, in the form of alkanes, mono-, di- and trimethylalkanes (MMA, DMA, TMA) were identified in surface and buried mats. Previous studies reported a bimodal distribution of n-Alkanes in the buried mats due to the relatively rapid decline in the abundance of MMAs and DMAs in the C16-C22 range with C24-C45 exclusively found in buried mats, however, this bimodal distribution was not found in our samples. Furthermore, we were able to improve the subsurface facies model for the Jurassic microbialites with our biomarker data as it shows that microbial mats growing in tidal pools or lagoons within the sabkha system form the most prolific hydrocarbon source rocks.

[Distribution and seasonal dynamics of meiofauna in intertidal zone of Qingdao sandy beaches, Shandong Province of East China].

PubMed

Li, Ha; Hua, Er; Zhang, Zhi-Nan

2012-12-01

An investigation was conducted on the abundance, group composition, and distribution of meiofauna at the Second Beach of Taiping Bay and the Shilaoren Beach in Qingdao in January, April, July, and October 2008, aimed to analyze the distribution and seasonal dynamics of meiofauna in the intertidal zone of Qingdao sandy beaches. The measurements of environmental factors, including sediment grain size, interstitial water salinity, interstitial water temperature, organic matter content (TOC), and chlorophyll a (Chl a) content, were made simultaneously. There existed obvious seasonal differences in the environment factors, which could be clustered into two groups, i. e. , spring-winter group (January and April) and summer-autumn group (July and October). At the Second Beach of Taiping Bay, the mean annual abundance of meiofauna was (1167.3 +/- 768.3) ind x 10 cm(-2), and the most dominant group was Nematoda, accounting for 91% of the total. The meiofaunal group composition and abundance at the Second Beach differed horizontally, with the abundance ranked as high tide zone < middle tide zone < low tide zone. The meiofaunal group composition and abundance also varied seasonally, with high values in spring/winter and low values in summer/autumn (spring > winter > autumn > summer). The vertical distribution of the meiofauna in the high and middle tide zones of the Second Beach varied seasonally too. The meiofauna migrated downward with increasing temperature, concentrated in surface layer in winter and migrated downward in summer. At the Shilaoren Beach, the mean annual abundance of meiofauna was (1130.2 +/- 1419.1) ind x 10 cm(-2), and Nematoda accounted for 85% of the total. There was a great similarity of the environmental factors in the middle tide zone of the Second Beach and Shilaoren Beach, which led to no differences in the meiofaunal group composition and abundance. However, the vertical distribution of the meiofauna differed between the two beaches. When the temperature decreased, the meiofauna at Shilaoren Beach migrated downward. The ANOVA and BIOENV analyses showed that the TOC and MD phi were most responsible for the distribution of meiofauna among the tidal zones, the interstitial water temperature, MD phi, and TOC were the main causes of the seasonal variation of meiofaunal group composition and abundance, whereas the sediment Chl a affected the vertical migration of meiofauna. Tourism-induced sediment variation was another factor affecting the meiofaunal abundance, group composition, and distribution.

Relating salt marsh pore water geochemistry patterns to vegetation zones and hydrologic influences

NASA Astrophysics Data System (ADS)

Moffett, Kevan B.; Gorelick, Steven M.

2016-03-01

Physical, chemical, and biological factors influence vegetation zonation in salt marshes and other wetlands, but connections among these factors could be better understood. If salt marsh vegetation and marsh pore water geochemistry coorganize, e.g., via continuous plant water uptake and persistently unsaturated sediments controlling vegetation zone-specific pore water geochemistry, this could complement known physical mechanisms of marsh self-organization. A high-resolution survey of pore water geochemistry was conducted among five salt marsh vegetation zones at the same intertidal elevation. Sampling transects were arrayed both parallel and perpendicular to tidal channels. Pore water geochemistry patterns were both horizontally differentiated, corresponding to vegetation zonation, and vertically differentiated, relating to root influences. The geochemical patterns across the site were less broadly related to marsh hydrology than to vegetation zonation. Mechanisms contributing to geochemical differentiation included: root-induced oxidation and nutrient (P) depletion, surface and creek-bank sediment flushing by rainfall or tides, evapotranspiration creating aerated pore space for partial sediment flushing in some areas while persistently saturated conditions hindered pore water renewal in others, and evapoconcentration of pore water solutes overall. The concentrated pore waters draining to the tidal creeks accounted for 41% of ebb tide solutes (median of 14 elements), including being a potentially toxic source of Ni but a slight sink for Zn, at least during the short, winter study period in southern San Francisco Bay. Heterogeneous vegetation effects on pore water geochemistry are not only significant locally within the marsh but may broadly influence marsh-estuary solute exchange and ecology.

Effect of nutrient amendments on indigenous hydrocarbon biodegradation in oil-contaminated beach sediments.

PubMed

Xu, Ran; Obbard, Jeffrey P

2003-01-01

Nutrient amendment to oil-contaminated beach sediments is a critical factor for the enhancement of indigenous microbial activity and biodegradation of petroleum hydrocarbons in the intertidal marine environment. In this study, we investigated the stimulatory effect of the slow-release fertilizers Osmocote (Os; Scotts, Marysville, OH) and Inipol EAP-22 (Ip; ATOFINA Chemicals, Philadelphia, PA) combined with inorganic nutrients on the bioremediation of oil-spiked beach sediments using an open irrigation system with artificial seawater over a 45-d period. Osmocote is comprised of a semipermeable membrane surrounding water-soluble inorganic N, P, and K. Inipol, which contains organic N and P, has been used for oil cleanup on beach substrate. Nutrient concentrations and microbial activity in sediments were monitored by analyzing sediment leachates and metabolic dehydrogenase activity of the microbial biomass, respectively. Loss of aliphatics (n-C12 to n-C33, pristane, and phytane) was significantly greater (total loss between 95 and 97%) in oil-spiked sediments treated with Os alone or in combination with other nutrient amendments, compared with an unamended oil-spiked control (26% loss) or sediments treated with the other nutrient amendments (28-65% loss). A combination of Os and soluble nutrients (SN) was favorable for the rapid metabolic stimulation of the indigenous microbial biomass, the sustained release of nutrients, and the enhanced biodegradation of petroleum hydrocarbons in leached, oil-contaminated sediments.

UV radiation impacts body weight, oxygen consumption, and shelter selection in the intertidal vertebrate Girella laevifrons.

PubMed

Pulgar, José; Waldisperg, Melany; Galbán-Malagón, Cristóbal; Maturana, Diego; Pulgar, Victor M; Aldana, Marcela

2017-02-01

The amount of ultraviolet (UV) radiation reaching the earth's surface has increased due to ozone layer depletion, and this fact represents an opportunity to evaluate the physiological and behavioral responses of animals to this global-scale stressor. The transitory fish Girella laevifrons inhabits pools in the upper intertidal zone, which is characterized by exposure to a wide range of stressors, including UV radiation. We documented the field magnitude and the impact of UV radiation on oxygen consumption, body mass variations, and shelter (rocky and algae) selection by G. laevifrons. UV-exposed animals showed increased oxygen consumption, slower body weight increase, and active rocky shelter selection. Control fish showed increased body weight and no evident shelter selection. The results indicated that UV exposure affects fish energetic balance and habitat selection to favor greater protection against radiation. Increased UV exposure in transitory intertidal animals at levels observed in upper intertidal pools may alter the residency time of fish before leaving for the subtidal zone. Therefore, UV-induced energetic changes may determine animal performance and ontogenetic physiological itineraries, whereas shelter quality might determine habitat use. Copyright © 2016 Elsevier B.V. All rights reserved.

Continuous monitoring bed-level dynamics on an intertidal flat: introducing novel stand-alone high-resolution SED-sensors

NASA Astrophysics Data System (ADS)

Hu, Zhan; Lenting, Walther; van der Wal, Daphne; Bouma, Tjeerd

2015-04-01

Tidal flat morphology is continuously shaped by hydrodynamic force, resulting in highly dynamic bed elevations. The knowledge of short-term bed-level changes is important both for understanding sediment transport processes as well as for assessing critical ecological processes such as e.g. vegetation recruitment chances on tidal flats. Due to the labour involved, manual discontinuous measurements lack the ability to continuously monitor bed-elevation changes. Existing methods for automated continuous monitoring of bed-level changes lack vertical accuracy (e.g., Photo-Electronic Erosion Pin sensor and resistive rod) or limited in spatial application by using expensive technology (e.g., acoustic bed level sensors). A method provides sufficient accuracy with a reasonable cost is needed. In light of this, a high-accuracy sensor (2 mm) for continuously measuring short-term Surface-Elevation Dynamics (SED-sensor) was developed. This SED-sensor makes use of photovoltaic cells and operates stand-alone using internal power supply and data logging system. The unit cost and the labour in deployments is therefore reduced, which facilitates monitoring with a number of units. In this study, the performance of a group of SED-sensors is tested against data obtained with precise manual measurements using traditional Sediment Erosion Bars (SEB). An excellent agreement between the two methods was obtained, indicating the accuracy and precision of the SED-sensors. Furthermore, to demonstrate how the SED-sensors can be used for measuring short-term bed-level dynamics, two SED-sensors were deployed for 1 month at two sites with contrasting wave exposure conditions. Daily bed-level changes were obtained including a severe storm erosion event. The difference in observed bed-level dynamics at both sites was statistically explained by their different hydrodynamic conditions. Thus, the stand-alone SED-sensor can be applied to monitor sediment surface dynamics with high vertical and temporal resolutions, which provides opportunities to pinpoint morphological responses to various forces in a number of environments (e.g. tidal flats, beaches, rivers and dunes).

Variations of Morphologic Changes induced by Tropical Storm Debby along Three Barrier Island, West-Central Florida, USA

NASA Astrophysics Data System (ADS)

Wang, P.; Roberts, T.

2012-12-01

Tropical Storm Debby generated sustained high waves and elevated water levels for nearly three days from June 24th to 26th, 2012, inducing substantial changes in beach and nearshore morphology. In addition, the storm winds and high waves approached the coast from a highly oblique angle from the south, driving substantial northward longshore sand transport, opposite to the regional net annual southward transport. A total of 145 beach and nearshore profiles along 3 adjacent barrier islands were surveyed 2 weeks before and one week after the storm impact. Overall, dune, beach, intertidal, and immediate subtidal areas suffered erosion, while deposition was measured over the nearshore bar. Beach recovery in the form of ridge and runnel development occurred as the storm energy subsided. Substantial longshore variations of storm-induced beach changes were measured, including both severe dune/beach/berm erosion and storm berm accretion, and both onshore and offshore migration of nearshore bar. Factors controlling these longshore variations include: 1) the oblique approaching of the storm forcing, 2) pre-storm beach morphology and chronic erosional or accretional trends, 3) sediment supply, and 4) tidal inlet and beach interactions. Wide spreading dune scarping occurred along the 30-km studied coast. Based on the pre- and post-storm survey data, a balanced sediment budget is obtained accounting for sand volume loss from dune, beach, intertidal, and subtidal zones, and sand gains over the nearshore bar and along the northern sections of the beach.

Biotically constrained palaeoenvironmental conditions of a mid-Holocene intertidal lagoon on the southern shore of the Arabian Gulf: evidence associated with a whale skeleton at Musaffah, Abu Dhabi, UAE

NASA Astrophysics Data System (ADS)

Stewart, J. R.; Aspinall, S.; Beech, M.; Fenberg, P.; Hellyer, P.; Larkin, N.; Lokier, S. W.; Marx, F. G.; Meyer, M.; Miller, R.; Rainbow, P. S.; Taylor, J. D.; Whittaker, J. E.; Al-Mehsin, K.; Strohmenger, C. J.

2011-12-01

Whale remains (a left and right mandible, scapula, humerus and fragmentary radius and ulna as well as parts of the cranium and rostrum) belonging to a probable humpback whale ( Megaptera cf. novaeangliae) were found in the well-described sabkha sequence exposed in the Musaffah Industrial Channel, Abu Dhabi, United Arab Emirates. More precisely, the whale remains were found in a series of sediments representing a range of lagoonal facies. The sediments surrounding the whale bones were age-dated at approximately 5200 14C yrs BP and are therefore interpreted to correspond to the previously documented late Flandrian sea-level peak, preceding a fall in sea-level which culminated in the supratidal sabkha overprint of the carbonates. Associated with the whale remains is an assemblage of molluscs, foraminifera and ostracods. Together with the inferred presence of sea grass and algae, these facies are interpreted to indicate a very shallow subtidal to intertidal lagoonal environment. Cirripede remains found associated with the skeleton were identified as those of the whale barnacle Coronula diadema and hence had their origins with the whale. Significantly, the low species diversity of microfossils suggests that higher salinities existed in the mid-Holocene lagoon than are present in modern counterparts. This is here inferred to be related to the onset of continental aridity in Arabia during the mid-Holocene.

Vulnerability to Climate Change of Mangroves: Assessment from Cameroon, Central Africa

PubMed Central

Ellison, Joanna C.; Zouh, Isabella

2012-01-01

Intertidal mangrove ecosystems are sensitive to climate change impacts, particularly to associated relative sea level rise. Human stressors and low tidal range add to vulnerability, both characteristics of the Doula Estuary, Cameroon. To investigate vulnerability, spatial techniques were combined with ground surveys to map distributions of mangrove zones, and compare with historical spatial records to quantify change over the last few decades. Low technology techniques were used to establish the tidal range and relative elevation of the mapped mangrove area. Stratigraphic coring and palaeobiological reconstruction were used to show the longer term biological history of mangroves and net sedimentation rate, and oral history surveys of local communities were used to provide evidence of recent change and identify possible causes. Results showed that the seaward edge of mangroves had over two thirds of the shoreline experienced dieback at up to 3 m per year over the last three decades, and an offshore mangrove island had suffered 89% loss. Results also showed low net sedimentation rates under seaward edge mangroves, and restricted intertidal elevation habitats of all mangroves, and Avicennia and Laguncularia in particular. To reduce vulnerability, adaptation planning can be improved by reducing the non-climate stressors on the mangrove area, particularly those resulting from human impacts. Other priorities for adaptation planning in mangrove areas that are located in such low tidal range regions are to plan inland migration areas and strategic protected areas for mangroves, and to undertake management activities that enhance accretion within the mangroves. PMID:24832511

Mangrove growth in New Zealand estuaries: the role of nutrient enrichment at sites with contrasting rates of sedimentation.

PubMed

Lovelock, Catherine E; Feller, Ilka C; Ellis, Joanne; Schwarz, Ann Maree; Hancock, Nicole; Nichols, Pip; Sorrell, Brian

2007-09-01

Mangrove forest coverage is increasing in the estuaries of the North Island of New Zealand, causing changes in estuarine ecosystem structure and function. Sedimentation and associated nutrient enrichment have been proposed to be factors leading to increases in mangrove cover, but the relative importance of each of these factors is unknown. We conducted a fertilization study in estuaries with different sedimentation histories in order to determine the role of nutrient enrichment in stimulating mangrove growth and forest development. We expected that if mangroves were nutrient-limited, nutrient enrichment would lead to increases in mangrove growth and forest structure and that nutrient enrichment of trees in our site with low sedimentation would give rise to trees and sediments that converged in terms of functional characteristics on control sites in our high sedimentation site. The effects of fertilizing with nitrogen (N) varied among sites and across the intertidal zone, with enhancements in growth, photosynthetic carbon gain, N resorption prior to leaf senescence and the leaf area index of canopies being significantly greater at the high sedimentation sites than at the low sedimentation sites, and in landward dwarf trees compared to seaward fringing trees. Sediment respiration (CO(2) efflux) was higher at the high sedimentation site than at the low one sedimentation site, but it was not significantly affected by fertilization, suggesting that the high sedimentation site supported greater bacterial mineralization of sediment carbon. Nutrient enrichment of the coastal zone has a role in facilitating the expansion of mangroves in estuaries of the North Island of New Zealand, but this effect is secondary to that of sedimentation, which increases habitat area and stimulates growth. In estuaries with high sediment loads, enrichment with N will cause greater mangrove growth and further changes in ecosystem function.

Integration of TerraSAR-X, RapidEye and airborne lidar for remote sensing of intertidal bedforms on the upper flats of Norderney (German Wadden Sea)

NASA Astrophysics Data System (ADS)

Adolph, Winny; Jung, Richard; Schmidt, Alena; Ehlers, Manfred; Heipke, Christian; Bartholomä, Alexander; Farke, Hubert

2017-04-01

The Wadden Sea is a large coastal transition area adjoining the southern North Sea uniting ecological key functions with an important role in coastal protection. The region is strictly protected by EU directives and national law and is a UNESCO World Heritage Site, requiring frequent quality assessments and regular monitoring. In 2014 an intertidal bedform area characterised by alternating crests and water-covered troughs on the tidal flats of the island of Norderney (German Wadden Sea sector) was chosen to test different remote sensing methods for habitat mapping: airborne lidar, satellite-based radar (TerraSAR-X) and electro-optical sensors (RapidEye). The results revealed that, although sensitive to different surface qualities, all sensors were able to image the bedforms. A digital terrain model generated from the lidar data shows crests and slopes of the bedforms with high geometric accuracy in the centimetre range, but high costs limit the operation area. TerraSAR-X data enabled identifying the positions of the bedforms reflecting the residual water in the troughs also with a high resolution of up to 1.1 m, but with larger footprints and much higher temporal availability. RapidEye data are sensitive to differences in sediment moisture employed to identify crest areas, slopes and troughs, with high spatial coverage but the lowest resolution (6.5 m). Monitoring concepts may differ in their remote sensing requirements regarding areal coverage, spatial and temporal resolution, sensitivity and geometric accuracy. Also financial budgets limit the selection of sensors. Thus, combining differing assets into an integrated concept of remote sensing contributes to solving these issues.

Geochemical factors promoting die-back gap formation in colonizing patches of Spartina densiflora in an irregularly flooded marsh

NASA Astrophysics Data System (ADS)

Mirlean, Nicolai; Costa, Cesar S. B.

2017-04-01

Circular (RP) and ring-shape (RP) patches of vegetation in intertidal flats have been associated with the radial expansion of tussock growth forms and die-back gap in older central stands, respectively. RP formation has not yet been sufficiently explained. We accomplished a comparative geochemical study of CP and RP structures of Spartina densiflora within a single saltmarsh in a microtidal estuary (<0.5 m). The pore water under these structures demonstrated distinctive physical-chemical properties by marked seasonal changing in water level and salinity. During high-water period dissolved H2S was frequently low in pore waters of S. densiflora structures due to reactive-Fe, which scavenge the sulfide from solution and form solid sulfides. During less flooded-brackish water period, pore water pH goes down below 4 inside the vegetated bordering areas of RP. In these locations the concentration of soluble sulfides dramatically increases up to 140 μM L-1. The high concentration of protons in pore water is the result of solid sulfides atmospheric oxidation to sulfuric acid. High dissolution of H2S, along with the low pH, creates a toxic environment for S. densiflora and die-back central gap formation in RP. CP structure was 5 cm higher in the intertidal than RP but shows frequent presence of a water layer, less severe oxidation of sulfides and limited building-up of toxic condition to plants. Development of S. densiflora RP probably indicates the uplift of sediment by this bioengineer grass and/or periodic lowering of the water surface below a certain critical level.

The morphodynamics and internal structure of intertidal fine-gravel dunes: Hills Flats, Severn Estuary, UK

NASA Astrophysics Data System (ADS)

Carling, P. A.; Radecki-Pawlik, A.; Williams, J. J.; Rumble, B.; Meshkova, L.; Bell, P.; Breakspear, R.

2006-01-01

In the macrotidal Severn estuary, UK, the dynamics of intertidal fine-gravel dunes were investigated. These dunes are migrating across a bedrock platform. Systematic observations were made of hydraulic climate, geometry, migration rates and internal sedimentary structures of the dunes. During spring tides, the ebb flow is dominant, dunes grow in height and have ebb orientated geometry with bedrock floors in the troughs. During neap tides, a weak flood flow may dominate. Dunes then are flood orientated or symmetrical. Neap dune heights decrease and the eroded sediment is stored in the dune troughs where the bedrock becomes blanketed by muddy gravel. During spring tides, instantaneous bed shear stresses reach 8 N m - 2 , sufficient to disrupt a 9 mm-gravel armour layer. However, a sustained bed shear stress of 4 N m - 2 is required to initiate dune migration at which time the critical depth-mean velocity is 1 m s - 1 . Ebb and flood inequalities in the bed shear stress explain the changes in dune asymmetry and internal structures. During flood tides, the crests of the dunes reverse such that very mobile sedimentary 'caps' overlie a more stable dune 'core'. Because ebb tides dominate, internal structures of the caps often are characterised by ebb orientated steep open-work foresets developed by strong tidal currents and some lower angle crossbeds deposited as weaker currents degrade foresets. The foresets forming the caps may be grouped into cosets (tidal bundles) and are separated from mud-infused cores of crossbeds that lie below, by reactivation and erosion surfaces blanketed by discontinuous mud drapes. The cores often exhibit distinctive muddy toe sets that define the spacing of tidal cosets.

Migratory flows and foraging habitat selection by shorebirds along the northeastern coast of Brazil: The case of Baía de Todos os Santos

NASA Astrophysics Data System (ADS)

Lunardi, Vitor O.; Macedo, Regina H.; Granadeiro, José P.; Palmeirim, Jorge M.

2012-01-01

Large numbers of Nearctic shorebirds migrate and winter along the coast of northeastern Brazil, but there is little information on their migratory flows, foraging ecology, and on the structure of the species assemblages that they form with resident shorebirds. We studied these issues on intertidal flats of Baía de Todos os Santos (Bahia), the second largest bay in Brazil. During a full year cycle we carried out weekly bird counts in an intertidal area of 280 ha divided in sectors, where we also measured environmental parameters. The analyses of weekly counts resulted in a detailed phenology of use of the area by shorebirds. Five species were resident and ten were Nearctic migrants. Several of the latter had clear peaks in numbers in March and October, revealing the use of the bay as a stopover during both the north-bound and south-bound migration flows. A canonical correspondence analysis of the relationship between environmental parameters and bird numbers indicated that the foraging bird assemblage could be divided into five main groups, occupying distinct ecological gradients in the study area. The most important factors driving this structure were invertebrate prey abundance, percentage of fine sediments, area of mangrove cover and distance to channels. Our findings imply that maintenance of the diversity of intertidal habitats in this bay is crucial to satisfy the particular habitat requirements of resident and migrant shorebirds using the northeastern coastal regions of Brazil.

The development of the Ganges-Brahmaputra tidal delta plain: construction to maintenance phase changes in platform and channel morphology

NASA Astrophysics Data System (ADS)

Wilson, C.; Goodbred, S. L., Jr.; Hale, R. P.; Bain, R. L.

2016-12-01

The lower Ganges-Brahmaputra (G-B) delta can be divided into the fluvial-tidal river mouth and distributaries under active construction by the G-B rivers, and the distal tidally maintained deltaplain. In the active river-mouth, distributaries have constructed 5,000 km2 of large, coalescing islands that define the prograding coastline and subaerial-delta front. Although seasonal riverbank erosion is common, the area as a whole has gained land, primarily via horizontal and vertical accretion of intertidal mudflats and seaward progradation of emergent, tidally-elongated sandy channel-mouth bars. An analysis of historical imagery within the active river mouth shows larger and higher order channels form as merging bars and shoal-islands constrict distributary channels, while lower order creeks emerge secondarily, presumably as flow on shoaling intertidal mudflats becomes channelized and mangrove vegetation takes hold. With waning fluvial input (occurring from major distributary migration or avulsion), tidal and marine processes exhibit a stronger control on sediment transport and distribution, as is happening in the downdrift areas of the G-B tidal delta plain. The relatively pristine Sundarbans mangrove forest covers 4,100 km2 along the coast, while 11,200 km2 of the lower tidal delta plain is densely inhabited (population density up to 1,000/km2) and embanked for agricultural purposes. Although considered moribund or abandoned from direct fluvial sediment input, distal portions of the tidal delta are connected to the sediment transport system by its dense network of tidal channels. The subaerial landscape that was initially constructed by the point-sourced input of coarser-grained fluvial sediment from the mainstem rivers is thereafter maintained predominantly by onshore tidal sediment transport of finer-grained silt, and we observe accretion rates as high as 2-4 cm/y supported on the mangrove platform during the monsoon season. The tidal channels show evidence of some migration since the mid-1800s (Allison, 1998); however, there appears to be little evidence of net infilling or widening in coastal areas (<50 km from the Bay of Bengal). In contrast, we show interior areas have chronic siltation over the past 50 years due to anthropogenically modified changes in the tidal prism from poldering.

Lethal and sub-lethal effects of elevated CO2 concentrations on marine benthic invertebrates and fish.

PubMed

Lee, Changkeun; Hong, Seongjin; Kwon, Bong-Oh; Lee, Jung-Ho; Ryu, Jongseong; Park, Young-Gyu; Kang, Seong-Gil; Khim, Jong Seong

2016-08-01

Concern about leakage of carbon dioxide (CO2) from deep-sea storage in geological reservoirs is increasing because of its possible adverse effects on marine organisms locally or at nearby coastal areas both in sediment and water column. In the present study, we examined how elevated CO2 affects various intertidal epibenthic (benthic copepod), intertidal endobenthic (Manila clam and Venus clam), sub-tidal benthic (brittle starfish), and free-living (marine medaka) organisms in areas expected to be impacted by leakage. Acute lethal and sub-lethal effects were detected in the adult stage of all test organisms exposed to varying concentrations of CO2, due to the associated decline in pH (8.3 to 5.2) during 96-h exposure. However, intertidal organisms (such as benthic copepods and clams) showed remarkable resistance to elevated CO2, with the Venus clam being the most tolerant (LpH50 = 5.45). Sub-tidal species (such as brittle starfish [LpH50 = 6.16] and marine medaka [LpH50 = 5.91]) were more sensitive to elevated CO2 compared to intertidal species, possibly because they have fewer defensive capabilities. Of note, the exposure duration might regulate the degree of acute sub-lethal effects, as evidenced by the Venus clam, which showed a time-dependent effect to elevated CO2. Finally, copper was chosen as a model toxic element to find out the synergistic or antagonistic effects between ocean acidification and metal pollution. Combination of CO2 and Cu exposure enhances the adverse effects to organisms, generally supporting a synergistic effect scenario. Overall, the significant variation in the degree to which CO2 adversely affected organisms (viz., working range and strength) was clearly observed, supporting the general concept of species-dependent effects of elevated CO2.

Recent advances in the use of estuarine meiobenthos to assess contaminated sediment effects in multi-species whole sediment microcosms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandler, G.T.; Coull, B.C.; Schizas, N.V.

1995-12-31

Many marine meiobenthic taxa (i.e. invertebrates passing a 1-mm sieve but retaining on a 0.063 mm sieve) are ideal for ``whole-sediment`` and porewater bioassay of sedimented pollutants. Annual production of meiobenthos is 5--10 times that of the more commonly studied macrobenthos, and > 95% of all meiobenthos live in the oxic zone of muddy sediments at densities of 4--12 million per M{sup 2}. Most spend their entire lifecycles, burrowing freely and feeding on/within the sediment:porewater matrix, many taxa undergo 10--14 generations per year, most larval/juvenile stages are benthic, and many have easily quantifiable reproductive output. Furthermore, many meiobenthic taxa canmore » be cultured indefinitely over multiple life-cycles within simple sediment microcosms consisting of sealed whole-sediment cores collected intact from intertidal mudflats. The authors describe several recent technical developments exploiting meiofaunal sediment culture for rapid contaminated sediment bioassays of toxicant effects on survival, reproduction and population growth of meiobenthic taxa in whole-sediment microcosms. Currently meiobenthic copepods, nematodes, foraminifers and polychaetes are being continuously cultured to study these parameters under exposure to model sediment-associated toxicants (e.g. cadmium). Bioassays are run for 21-d under flowing seawater. With this approach, fertile benthic copepods (e.g. Amphiascus tenuiremis) can be added to core microcosms to assess survival and growth of a fixed population cohort. All other meiobenthic taxa are enumerated relative to controls and evaluated for toxicant effects on higher order community-level endpoints. This approach exploits meiobenthos` high abundance and rapid reproductive rates to yield on a micro scale better endpoints than much larger sediment mesocosms targeted at macrofaunal endpoints.« less

Material exchange and food web of seagrass beds in the Sylt-Rømø Bight: how significant are community changes at the ecosystem level?

NASA Astrophysics Data System (ADS)

Asmus, H.; Asmus, R.

2000-07-01

Material exchange, biodiversity and trophic transfer within the food web were investigated in two different types of intertidal seagrass beds: a sheltered, dense Zostera marina bed and a more exposed, sparse Z. noltii bed, in the Northern Wadden Sea. Both types of Zostera beds show a seasonal development of above-ground biomass, and therefore measurements were carried out during the vegetation period in summer. The exchange of particles and nutrients between seagrass beds and the overlying water was measured directly using an in situ flume. Particle sedimentation [carbon (C), nitrogen (N) and phosphorus (P) constituents] from the water column prevailed in dense seagrass beds. In the sheltered, dense seagrass bed, a net particle uptake was found even on windy days (7-8 Beaufort). Dissolved inorganic N and orthophosphate were mainly taken up by the dense seagrass bed. At times of strong winds, nutrients were released from the benthic community to tidal waters. In a budget calculation of total N and total P, the dense seagrass beds were characterised as a material sink. The seagrass beds with sparse Z. noltii were a source of particles even during calm weather. The uptake of dissolved inorganic N in the sparse seagrass bed was low but significant, while the uptake of inorganic phosphate and silicate by seagrasses and their epiphytes was exceeded by release processes from the sediment into the overlying water. Estimates at the ecosystem level showed that material fluxes of seagrass beds in the Sylt-Rømø Bight are dominated by the dense type of Zostera beds. Therefore, seagrass beds act as a sink for particles and for dissolved inorganic nutrients. During storms, seagrass beds are distinct sources for inorganic nutrients. The total intertidal area of the Sylt-Rømø Bight could be described as a sink for particles and a source for dissolved nutrients. This balance of the material budget was estimated by either including or excluding seagrass beds. Including the subtidal part, the function of the ecosystem as a source for particles increased, supposing that all seagrass beds were lost from the area. During the vegetation period, seagrass beds act as a storage compartment for material accumulated in the living biomass of the community. There was great biodiversity among the plant and animal groups found in intertidal seagrass beds of the Sylt-Rømø Bay, representing 50-86% of the total number of species investigated, depending on the particular group. Since most species are not exclusively seagrass residents, the loss of intertidal seagrass beds would be of minor importance for biodiversity at the ecosystem level. Food web structure in seagrass beds is different from other intertidal communities. Primary production and detritus input is high, but secondary production is similar to that of unvegetated areas, although the relative importance of the trophic guilds is different. The loss of seagrass beds leads to profound alterations in the food web of the total ecosystem. Historical as well as recent changes in material fluxes and energy flow due to man-made alterations to the ecosystem are discussed.

Intertidal geothermal hot springs as a source of trace elements to the coastal zone: A case study from Bahía Concepción, Gulf of California.

PubMed

Leal-Acosta, María Luisa; Shumilin, Evgueni; Mirlean, Nicolai; Baturina, Elena Lounejeva; Sánchez-Rodríguez, Ignacio; Delgadillo-Hinojosa, Francisco; Borges-Souza, José

2018-03-01

We investigated the influence of the intertidal geothermal hot spring (GHS) on the biogeochemistry of trace elements in Santispac Bight, Bahía Concepción (Gulf of California). The geothermal fluids were enriched in As and Hg mainly in ionic form. The suspended particulate matter of the GHS had elevated enrichment factor (EF) >1 of As, Bi, Cd, Co, Cu, Mn, Mo, Sb, Sn, Sr, Ti, U and Zn. The sediment core from GHS1 had high concentration of As, Hg, C org , S, V, Mo, and U and the extremely high EF of these elements at 8cm of the core. The maximum bioaccumulation of As and Hg was in seaweeds Sargassum sinicola collected near the GHS2. The results confirm the input of trace elements to the coastal zone in Bahía Concepción from geothermal fluids and the evident modification of the chemical composition of the adjacent marine environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Relative Importance of Biotic and Abiotic Forces on the Composition and Dynamics of a Soft-Sediment Intertidal Community

PubMed Central

Barbeau, Myriam A.

2016-01-01

Top-down, bottom-up, middle-out and abiotic factors are usually viewed as main forces structuring biological communities, although assessment of their relative importance, in a single study, is rarely done. We quantified, using multivariate methods, associations between abiotic and biotic (top-down, bottom-up and middle-out) variables and infaunal population/community variation on intertidal mudflats in the Bay of Fundy, Canada, over two years. Our analysis indicated that spatial structural factors like site and plot accounted for most of the community and population variation. Although we observed a significant relationship between the community/populations and the biotic and abiotic variables, most were of minor importance relative to the structural factors. We suggest that community and population structure were relatively uncoupled from the structuring influences of biotic and abiotic factors in this system because of high concentrations of resources that sustain high densities of infauna and limit exploitative competition. Furthermore, we hypothesize that the infaunal community primarily reflects stochastic spatial events, namely a “first come, first served” process. PMID:26790098

Occurrence, source and ecological assessment of baseline hydrocarbons in the intertidal marine sediments along the shoreline of Douglas Channel to Hecate Strait in British Columbia.

PubMed

Yang, Zeyu; Hollebone, Bruce P; Laforest, Sonia; Lambert, Patrick; Brown, Carl E; Yang, Chun; Shah, Keval; Landriault, Mike; Goldthorp, Michael

2017-09-15

The occurrence, source and ecological assessment of baseline hydrocarbons in the intertidal zone along the northern British shoreline were evaluated based on analyzing total petroleum hydrocarbons (TPH), n-alkanes, petroleum related biomarkers such as terpanes and steranes, and polycyclic aromatic hydrocarbons (PAHs) including non-alkylated and alkylated homologues (APAHs). The TPH levels, n-alkanes, petroleum biomarkers and PAHs in all the sampling sites, except for Masset Harbor/York Point at Gil Island were low, without obvious unresolved complex mixture (UCM) and petroleum contamination input. Specifically, n-alkanes showed a major terrestrial plants input; PAHs with abundant non-alkylated PAHs but minor APAHs showed a major pyrogenic input. However, obvious petroleum-derived hydrocarbons have impacted Masset Harbor. A historical petroleum input was found in York Point at Gil Island, due to the presence of the low level of petroleum biomarkers. Ecological assessment of 13 non-alkylated PAHs in Masset Harbor indicated no potential toxicity to the benthic organisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

Bio-foam enhances larval retention in a free-spawning marine tunicate

PubMed Central

Castilla, Juan Carlos; Manríquez, Patricio H.; Delgado, Alejandro P.; Gargallo, Ligia; Leiva, Angel; Radic, Deodato

2007-01-01

Here we report a mechanism that reduces dispersal of early developing stages and larvae in a free-spawning intertidal and shallow subtidal tunicate, Pyura praeputialis (Heller 1878), in the Bay of Antofagasta, Chile. The spawning of gametes by the tunicate into the naturally turbulent aerated seawater decreases their surface tension and induces the formation of a bio-foam. Water collected from foamy intertidal pools and tide channels showed a high concentration of P. praeputialis early developing stages and tadpole larvae in the foam. Because gametes are synchronically spawned for external fertilization and larvae settle near adults, our results suggest that this bio-foam increases fertilization success and effective settlement of their short-lived larvae in the vicinity of the adults spawning the gametes. This mechanism reinforces published evidence suggesting that local retention of intertidal and inshore marine invertebrate larvae may be more common than previously thought, offering, for instance, new perspectives for the design and networking of marine protected and management areas. PMID:17984045

Bio-foam enhances larval retention in a free-spawning marine tunicate.

PubMed

Castilla, Juan Carlos; Manríquez, Patricio H; Delgado, Alejandro P; Gargallo, Ligia; Leiva, Angel; Radic, Deodato

2007-11-13

Here we report a mechanism that reduces dispersal of early developing stages and larvae in a free-spawning intertidal and shallow subtidal tunicate, Pyura praeputialis (Heller 1878), in the Bay of Antofagasta, Chile. The spawning of gametes by the tunicate into the naturally turbulent aerated seawater decreases their surface tension and induces the formation of a bio-foam. Water collected from foamy intertidal pools and tide channels showed a high concentration of P. praeputialis early developing stages and tadpole larvae in the foam. Because gametes are synchronically spawned for external fertilization and larvae settle near adults, our results suggest that this bio-foam increases fertilization success and effective settlement of their short-lived larvae in the vicinity of the adults spawning the gametes. This mechanism reinforces published evidence suggesting that local retention of intertidal and inshore marine invertebrate larvae may be more common than previously thought, offering, for instance, new perspectives for the design and networking of marine protected and management areas.

Long-term, high frequency in situ measurements of intertidal mussel bed temperatures using biomimetic sensors

PubMed Central

Helmuth, Brian; Choi, Francis; Matzelle, Allison; Torossian, Jessica L.; Morello, Scott L.; Mislan, K.A.S.; Yamane, Lauren; Strickland, Denise; Szathmary, P. Lauren; Gilman, Sarah E.; Tockstein, Alyson; Hilbish, Thomas J.; Burrows, Michael T.; Power, Anne Marie; Gosling, Elizabeth; Mieszkowska, Nova; Harley, Christopher D.G.; Nishizaki, Michael; Carrington, Emily; Menge, Bruce; Petes, Laura; Foley, Melissa M.; Johnson, Angela; Poole, Megan; Noble, Mae M.; Richmond, Erin L.; Robart, Matt; Robinson, Jonathan; Sapp, Jerod; Sones, Jackie; Broitman, Bernardo R.; Denny, Mark W.; Mach, Katharine J.; Miller, Luke P.; O’Donnell, Michael; Ross, Philip; Hofmann, Gretchen E.; Zippay, Mackenzie; Blanchette, Carol; Macfarlan, J.A.; Carpizo-Ituarte, Eugenio; Ruttenberg, Benjamin; Peña Mejía, Carlos E.; McQuaid, Christopher D.; Lathlean, Justin; Monaco, Cristián J.; Nicastro, Katy R.; Zardi, Gerardo

2016-01-01

At a proximal level, the physiological impacts of global climate change on ectothermic organisms are manifest as changes in body temperatures. Especially for plants and animals exposed to direct solar radiation, body temperatures can be substantially different from air temperatures. We deployed biomimetic sensors that approximate the thermal characteristics of intertidal mussels at 71 sites worldwide, from 1998-present. Loggers recorded temperatures at 10–30 min intervals nearly continuously at multiple intertidal elevations. Comparisons against direct measurements of mussel tissue temperature indicated errors of ~2.0–2.5 °C, during daily fluctuations that often exceeded 15°–20 °C. Geographic patterns in thermal stress based on biomimetic logger measurements were generally far more complex than anticipated based only on ‘habitat-level’ measurements of air or sea surface temperature. This unique data set provides an opportunity to link physiological measurements with spatially- and temporally-explicit field observations of body temperature. PMID:27727238

Long-term, high frequency in situ measurements of intertidal mussel bed temperatures using biomimetic sensors

NASA Astrophysics Data System (ADS)

Helmuth, Brian; Choi, Francis; Matzelle, Allison; Torossian, Jessica L.; Morello, Scott L.; Mislan, K. A. S.; Yamane, Lauren; Strickland, Denise; Szathmary, P. Lauren; Gilman, Sarah E.; Tockstein, Alyson; Hilbish, Thomas J.; Burrows, Michael T.; Power, Anne Marie; Gosling, Elizabeth; Mieszkowska, Nova; Harley, Christopher D. G.; Nishizaki, Michael; Carrington, Emily; Menge, Bruce; Petes, Laura; Foley, Melissa M.; Johnson, Angela; Poole, Megan; Noble, Mae M.; Richmond, Erin L.; Robart, Matt; Robinson, Jonathan; Sapp, Jerod; Sones, Jackie; Broitman, Bernardo R.; Denny, Mark W.; Mach, Katharine J.; Miller, Luke P.; O'Donnell, Michael; Ross, Philip; Hofmann, Gretchen E.; Zippay, Mackenzie; Blanchette, Carol; Macfarlan, J. A.; Carpizo-Ituarte, Eugenio; Ruttenberg, Benjamin; Peña Mejía, Carlos E.; McQuaid, Christopher D.; Lathlean, Justin; Monaco, Cristián J.; Nicastro, Katy R.; Zardi, Gerardo

2016-10-01

At a proximal level, the physiological impacts of global climate change on ectothermic organisms are manifest as changes in body temperatures. Especially for plants and animals exposed to direct solar radiation, body temperatures can be substantially different from air temperatures. We deployed biomimetic sensors that approximate the thermal characteristics of intertidal mussels at 71 sites worldwide, from 1998-present. Loggers recorded temperatures at 10-30 min intervals nearly continuously at multiple intertidal elevations. Comparisons against direct measurements of mussel tissue temperature indicated errors of ~2.0-2.5 °C, during daily fluctuations that often exceeded 15°-20 °C. Geographic patterns in thermal stress based on biomimetic logger measurements were generally far more complex than anticipated based only on ‘habitat-level’ measurements of air or sea surface temperature. This unique data set provides an opportunity to link physiological measurements with spatially- and temporally-explicit field observations of body temperature.

Intertidal foraminifera (Protista) and carbon-nitrogen cycling: combined effects of temperature and diet quality

NASA Astrophysics Data System (ADS)

Wukovits, Julia; Enge, Annekatrin Julie; Oberrauch, Max; Watzka, Margarete; Wanek, Wolfgang; Heinz, Petra

2017-04-01

Benthic foraminifera (eukaryotic protists) are to a large extent acting as detrivores, feeding on microalgal detritus. Phytodetritus constitutes a main component of the intertidal carbon (C) and nitrogen (N) pool, thus making foraminifera important players in intertidal nutrient fluxes. These fluxes are strongly dependent on interactions between biotic and abiotic environmental factors, as e.g. the energetic value or the quality of phytodetritus that depends on environmental nutrient availability. Increased inorganic C concentrations in coastal water bodies (e.g. due to increased atmospheric CO2) can have a negative effect on the phytodetrital quality by increasing microalgal C:N ratios. Simultanous warming of the environment can cause increased metabolic rates of exposed heterotrophic organisms, like foraminifera. The combination of lower food quality and increased metabolic rates is supposed to cause cascading effects on organismic C cycling, potentially diminishing the role of detrivorous food as a C sink in marine food webs by increased discharge of excess C. In this study, the above described scenario was tested in laboratory feeding experiments on a common and abundant intertidal foraminiferal species (Haynesina germanica, collected in the German Wadden Sea). Two batches of artificially produced and dual isotope labeled (13C and 15N) chlorophyte detritus (1.5 gDW m-2) with different C:N ratios (5.5 and 7.6) and one batch of isotopically labelled diatom detritus (C:N 5.6) were fed under controlled conditions at three different temperatures. Results were extrapolated to the in situ abundance of live H. germanica individuals in the sampling area (sediment core data), to estimate the magnitude of the effect on an areal basis within the natural habitat. The study revealed significant, temperature induced variations in the carbon and nitrogen processing of H. germanica. The food source with an increased C:N ratio doubled the release of carbon from the H. germanica community at 20°C in relation to 15°C, causing a theoretical carbon loss of 1000 μg m-2 within 24 hours. The uptake of diatom detritus was higher relative to chlorophyte detritus uptake, though the carbon release did not differ from the chlorophyte food source of similar C:N (C:N 5.5). The results illustrate the impact of altered environmental factors on benthic nutrient fluxes in foraminiferal communities, an important but often overlooked component of intertidal microfauna associations.

A quantitative evaluation of the effects of Ascophyllum harvesting on the littoral ecosystem

NASA Astrophysics Data System (ADS)

Boaden, P. J. S.; Dring, M. T.

1980-03-01

Little is known of the ecological effects of harvesting littoral algae although this is a worldwide commercial activity. In 1976 an attempt to establish harvesting in Strangford Lough, Northern Ireland, was opposed on mainly theoretical conservation grounds. The attempt began and stopped within a single small bay leaving a sharp boundary between cut and uncut areas. A subjective survey apparently confirmed the predicted loss of cryptic fauna, decline through predation and the resorting of interboulder sediment. In April 1979 the cut and uncut areas were examined in detail to determine whether any of these effects had persisted and were demonstrable scientifically. Beach and boulder transects and various other studies showed some increases in the cut area. There was significantly more Fucus, Enteromorpha and Ulva; Cirratulus (inhabiting Rhodochorton-bound sediment on boulder surfaces) had a greater biomass. Some changes in Littorina colour morphs were apparent. Sediment in the cut area was coarser and had significantly more crustacean meiofauna. Ascophyllum internodal length and lateral branching were increased but it still provided 20% less shore cover than in the uncut area. There were significant decreases in the cover of Cladophora on the sides of boulders and of Halichondria, Hymeniacodon and Balanus on undersurfaces. Indeed on the habitable underside of boulders total animal cover had been reduced by nearly two-thirds and the average number of species per boulder by one-third. It is concluded that Ascophyllum harvesting has a significant and persistent effect on shore ecology. Littoral algae are a valuable commercial asset but it is important that some fairly large intertidal areas should be left unharvested for general conservation purposes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wendt, P.H.; Van Dolah, R.F.; Bobo, M.Y.

Recent evidence indicates that the wood preservative commonly used in dock pilings (chromated copper arsenate or CCA) is highly toxic to several estuarine organisms in laboratory experiments. Increasing demand for residential docks prompted a field study intended to complement these earlier laboratory investigations. Objectives of the study were to: (1) examine concentrations of Cu, Cr, and As in sediments and oysters from intertidal locations in several creeks with and without high densities of docks; (2) examine the bioaccumulation of wood preservative leachates by laboratory-reared oysters transferred to field sites near and distant from newly constructed docks; and (3) investigate themore » acute toxicity of wood preservative leachates for several species of estuarine fishes and invertebrates exposed to these compounds in the field. Preliminary results indicate that sediment concentrations of all three metals were well below ER-L levels reported by Long and Morgan at all but one dock site. In an ancillary study, 24h LC{sub 50} bioassays were performed using rotifers (Brachionus plicatilis) which were exposed to pore water from sediments in creeks with and without docks. Toxicities of bulk sediments from the same sites were examined using Microtox which measures decreases in bioluminescence of marine bacteria (Photobacterium phosphoreum) as a function of sediment concentration. Neither the rotifer nor the Microtox bioassays showed any significant differences in toxicity between creeks with and without docks.« less

Seasonal and Spatial Variations of Macro Benthos in the Intertidal Mudflat of Southern Yellow River Delta, China in 2007/2008

NASA Astrophysics Data System (ADS)

Zou, Li; Yao, Xiao; Yamaguchi, Hitomi; Guo, Xinyu; Gao, Huiwang; Wang, Kai; Sun, Mingyi

2018-04-01

In order to examine the seasonal and spatial distributions of benthic animals in the intertidal mudflat of the southern Yellow River Delta, field investigations were carried out in 2007 and 2008 and multiple methods were applied. Results showed that, the biomass of macro benthos ranged at 0.75-1151.00 g wet m-2 and averaged at 156.31 g wet m-2, in which Mactra veneriformis accounted for 75.6%-93.4% of the total macro benthic biomass. More than 90% of macro benthos inhabited in the middle and low tide lines, and higher biomass occurred in early summer and lower in winter. Statistical analysis showed that: 1) M. veneriformis growth was primarily favored at higher temperature and lower salinity; 2) after long time interaction, benthic bivalve grazers led to patching distributions of Chlorophyll a (Chl a); 3) macro benthic biomass positively related with Chl a when the concentration of Chl a was low, but they were negatively related when Chl a concentration was high; and 4) furthermore, the biomass of benthic bivalves peaked in the sediment with median grain size about 0.55 mm, but decreased gradually in coarse or fine sediments. The secondary productivity ranged at 0.37-283.68 g m-2yr-1 and averaged at 47.88 g m-2 yr-1, in which 69.7% was contributed by M. veneriformis It was estimated that primary production was transformed to secondary production at a rate of 6.87% approximately, which implies that there is a local sustainability of high bivalve production.

Surface water and groundwater interactions in coastal wetlands

NASA Astrophysics Data System (ADS)

Li, Ling; Xin, Pei; Shen, Chengji

2014-05-01

Salt marshes are an important wetland system in the upper intertidal zone, interfacing the land and coastal water. Dominated by salt-tolerant plants, these wetlands provide essential eco-environmental services for maintaining coastal biodiversity. They also act as sediment traps and help stabilize the coastline. While they play an active role in moderating greenhouse gas emissions, these wetlands have become increasingly vulnerable to the impact of global climate change. Salt marshes are a complex hydrological system characterized by strong, dynamic interactions between surface water and groundwater, which underpin the wetland's eco-functionality. Bordered with coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur at different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil aeration conditions, which in turn affect marsh plant growth. This talk presents results and findings from recent numerical and experimental studies, focusing on the pore-water flow behaviour in the marsh soil under the influence of tides and density-gradients.

Phospholipid-derived fatty acids and quinones as markers for bacterial biomass and community structure in marine sediments.

PubMed

Kunihiro, Tadao; Veuger, Bart; Vasquez-Cardenas, Diana; Pozzato, Lara; Le Guitton, Marie; Moriya, Kazuyoshi; Kuwae, Michinobu; Omori, Koji; Boschker, Henricus T S; van Oevelen, Dick

2014-01-01

Phospholipid-derived fatty acids (PLFA) and respiratory quinones (RQ) are microbial compounds that have been utilized as biomarkers to quantify bacterial biomass and to characterize microbial community structure in sediments, waters, and soils. While PLFAs have been widely used as quantitative bacterial biomarkers in marine sediments, applications of quinone analysis in marine sediments are very limited. In this study, we investigated the relation between both groups of bacterial biomarkers in a broad range of marine sediments from the intertidal zone to the deep sea. We found a good log-log correlation between concentrations of bacterial PLFA and RQ over several orders of magnitude. This relationship is probably due to metabolic variation in quinone concentrations in bacterial cells in different environments, whereas PLFA concentrations are relatively stable under different conditions. We also found a good agreement in the community structure classifications based on the bacterial PLFAs and RQs. These results strengthen the application of both compounds as quantitative bacterial biomarkers. Moreover, the bacterial PLFA- and RQ profiles revealed a comparable dissimilarity pattern of the sampled sediments, but with a higher level of dissimilarity for the RQs. This means that the quinone method has a higher resolution for resolving differences in bacterial community composition. Combining PLFA and quinone analysis as a complementary method is a good strategy to yield higher resolving power in bacterial community structure.

Response of Benthic Foraminifera to Organic Matter Quantity and Quality and Bioavailable Concentrations of Metals in Aveiro Lagoon (Portugal)

PubMed Central

Martins, Maria Virgínia Alves; Silva, Frederico; Laut, Lazaro L. M.; Frontalini, Fabrizio; Clemente, Iara M. M. M.; Miranda, Paulo; Figueira, Rubens; Sousa, Silvia H. M.; Dias, João M. Alveirinho

2015-01-01

This work analyses the distribution of living benthic foraminiferal assemblages of surface sediments in different intertidal areas of Ria de Aveiro (Portugal), a polihaline and anthropized coastal lagoon. The relationships among foraminiferal assemblages in association with environmental parameters (temperature, salinity, Eh and pH), grain size, the quantity and quality of organic matter (enrichment in carbohydrates, proteins and lipids), pollution caused by metals, and mineralogical data are studied in an attempt to identify indicators of adaptability to environmental stress. In particular, concentrations of selected metals in the surficial sediment are investigated to assess environmental pollution levels that are further synthetically parameterised by the Pollution Load Index (PLI). The PLI variations allowed the identification of five main polluted areas. Concentrations of metals were also analysed in three extracted phases to evaluate their possible mobility, bioavailability and toxicity in the surficial sediment. Polluted sediment in the form of both organic matter and metals can be found in the most confined zones. Whereas enrichment in organic matter and related biopolymers causes an increase in foraminifera density, pollution by metals leads to a decline in foraminiferal abundance and diversity in those zones. The first situation may be justified by the existence of opportunistic species (with high reproduction rate) that can live in low oxic conditions. The second is explained by the sensitivity of some species to pressure caused by metals. The quality of the organic matter found in these places and the option of a different food source should also explain the tolerance of several species to pollution caused by metals, despite their low reproductive rate in the most polluted areas. In this study, species that are sensitive and tolerant to organic matter and metal enrichment are identified, as is the differential sensitivity/tolerance of some species to metals enrichment. PMID:25706860

Relationship between Enterococcal Levels and Sediment Biofilms at Recreational Beaches in South Florida

PubMed Central

Piggot, Alan M.; Johnson, Sara; Phillips, Matthew C.; Solo-Gabriele, Helena M.

2012-01-01

Enterococci, recommended at the U.S. federal level for monitoring water quality at marine recreational beaches, have been found to reside and grow within beach sands. However, the environmental and ecological factors affecting enterococcal persistence remain poorly understood, making it difficult to determine levels of fecal pollution and assess human health risks. Here we document the presence of enterococci associated with beach sediment biofilms at eight south Florida recreational beaches. Enterococcal levels were highest in supratidal sands, where they displayed a nonlinear, unimodal relationship with extracellular polymeric secretions (EPS), the primary component of biofilms. Enterococcal levels peaked at intermediate levels of EPS, suggesting that biofilms may promote the survival of enterococci but also inhibit enterococci as the biofilm develops within beach sands. Analysis of bacterial community profiles determined by terminal restriction fragment length polymorphisms showed the bacterial communities of supratidal sediments to be significantly different from intertidal and subtidal communities; however, no differences were observed in bacterial community compositions associated with different EPS concentrations. Our results suggest that supratidal sands are a microbiologically unique environment favorable for the incorporation and persistence of enterococci within beach sediment biofilms. PMID:22706061

Searching for the Source of Salt Marsh Buried Mercury.

NASA Astrophysics Data System (ADS)

Brooke, C. G.; Nelson, D. C.; Fleming, E. J.

2016-12-01

Salt marshes provide a barrier between upstream mercury contamination and coastal ecosystems. Mercury is sorbed, transported, and deposited in estuarine systems. Once the upstream mercury source has been remediated, the downstream mercury contaminated salt marsh sediments should become "capped" or buried by uncontaminated sediments preventing further ecosystem contamination. Downstream from a remediated mercury mine, an estuarine intertidal marsh in Tomales Bay, CA, USA, scavengers/predators (e.g. Pachygrapsus crassipes, Lined Shore Crab) have leg mercury concentrations as high as 5.5 ppm (dry wt./dry wt.), which increase significantly with crab size, a surrogate for trophic level. These elevated mercury concentrations suggests that "buried" mercury is rereleased into the environment. To locate possible sources of mercury release in Walker Marsh, we sampled a transect across the marsh that included diverse micro-environments (e.g. rhizoshere, stratified sediments, faunal burrows). From each location we determined the sediment structure, sediment color, total sediment mercury, total sediment iron, and microbial composition (n = 28). Where flora or fauna had perturbed the sediment, mercury concentrations were 10% less than undisturbed stratified sediments (1025 ppb vs. 1164 ppb, respectively). High-throughput SSU rRNA gene sequencing and subsequent co-occurrence network analysis genera indicated that in flora- or fauna- perturbed sediments there was an increased likelihood that microbial genera contained mercury mobilizing genes (94% vs 57%; in perturbed vs stratified sediments, respectively). Our observations are consistent with findings by others that in perturbed sites mercury mobility increased. We did however identify a microbial and geochemical profile with increased mercury mobility. For future work we plan to quantify the role these micro-environments have on mercury-efflux from salt marshes.

The influence of cyanobacteria on oil polluted intertidal soils at the Saudi Arabian Gulf shores.

PubMed

Barth, Hans Jörg

2003-10-01

In 1991 the second Gulf War lead to the largest oil spill in human history. Over 770 km of coastline from southern Kuwait to Abu Ali Island (Saudi Arabia) were smothered with oil and tar, erasing most of the local plant and animal communities. In the following year cyanobacteria colonized most of the oil polluted shores. In the study area at the Saudi Arabian Gulf coast north of Jubail three different processes were observed that followed the extensive formation of cyanobacterial mats. The first one is desiccation, cracking, and peeling of the cyanobacterial mats, thereby removing the uppermost part of the oiled sediment. The second is the resettlement of burrowing macrofauna like crabs and benthic animals such as gastropods, which outcompete the cyanobacteria again. The third process is further extensive growth of cyanobacteria building thick laminated mats. These layers, completely seal the surface and hence produce an anaerobic milieu which inhibits oil degradation. As long as such cyanobacteria exist, they will prevent microbial oil degradation as well as any resettlement by macrofauna.

Significance of nearshore trace-fossil assemblages of the cambro-ordovician deadwood formation and Aladdin Sandstone, South Dakota

USGS Publications Warehouse

Stanley, T.M.; Feldmann, R.M.

1998-01-01

The Cambro-Ordovician Deadwood Formation and Aladdin Sandstone represent intertidal and subtidal, nearshore deposystems that contain few well-preserved body fossils, but contain abundant trace fossils. The present study uses the much neglected trace-fossil fauna to describe the diverse paleoenvironments represented in the Deadwood-Aladdin deposystems, and to better understand the environmental conditions that controlled benthic life in the Early Paleozoic. The Deadwood-Aladdin ichnotaxa can be separated into three distinct assemblages based on the changing sedimentologic and hydrodynamic conditions that existed across the Cambro-Ordovician shelf. Trace-fossil assemblages and corresponding lithofacies characteristics indicate that the Deadwood-Aladdin deposystems formed within an intertidal-flat and subtidal-shelf environment. Based on the distribution and numbers of preserved ichnotaxa, the intertidal flat can be subdivided further into an ecologically stressful inner sand-flat environment, and a more normal marine outer sand-flat environment, both of which belong to a mixed, Skolithos-Cruziana softground ichnofacies. The inner sand flat is characterized by low diversity, low numbers, and a general lack of complexly constructed ichnotaxa. Trace fossils common to both assemblages tend to be smaller in the inner flat compared to the outer sand flat. Taphonomic effects, such as substrate type and sediment heterogeneity, also aid in differentiating between the inner and outer sand-flat assemblages. The subtidal shelf environment is categorized in the Cruziana Ichnofacies. Ichnological evidence of periodic tempestite deposition and hardground development within this subtidal regime is manifested by high diversity and low abundance of ichnogenera.

Seasonal changes in environmental variables, biomass, production and nutrient contents in two contrasting tropical intertidal seagrass beds in South Sulawesi, Indonesia.

PubMed

Erftemeijer, Paul L A; Herman, Peter M J

1994-09-01

Seasonal dynamics were studied by monthly monitoring of biological and environmental variables in permanent quadrats in two contrasting intertidal seagrass beds in South Sulawesi, Indonesia, from February 1991 to January 1992. Datasets were analysed with canonical correlation analysis for correlations between environmental and biological variables. Considerable variation in biomass, production and plant tissue nutrient contents in a monospecific seagrass bed of Enhalus acoroides, growing on a coastal terrigenous mudbank (Gusung Tallang), was assumed to be related to riverine influences of the nearby Tallo River. The variation in seagrass variables at this site could, however, not be significantly correlated to seasonal patterns in rainfall, salinity, tides, nutrient availability, water motion or turbidity. A seasonal cycle in biomass, production and nutrient contents in a mixed seagrass bed of Thalassia hemprichii and E. acoroides, growing on carbonate sand on the reef flat of an offshore coral island (Barang Lompo), was found to be largely determined by tidal exposure and water motion. Exposure of the intertidal seagrass bed during hours of low water during spring tides showed a gradual shift from exposure during the night (January-June) to exposure during daylight (July-December). Daylight exposure resulted in a significant loss of above-ground plant biomass through desiccation and 'burning' of leaves. The observed seasonal dynamics of the seagrass bed on reef sediment contrast with reports from the Caribbean, where the effect of tidal exposure on comparable shallow-water seagrass communities is relatively insignificant due to a small tidal amplitude.

Biophysical control of intertidal benthic macroalgae revealed by high-frequency multispectral camera images

NASA Astrophysics Data System (ADS)

van der Wal, Daphne; van Dalen, Jeroen; Wielemaker-van den Dool, Annette; Dijkstra, Jasper T.; Ysebaert, Tom

2014-07-01

Intertidal benthic macroalgae are a biological quality indicator in estuaries and coasts. While remote sensing has been applied to quantify the spatial distribution of such macroalgae, it is generally not used for their monitoring. We examined the day-to-day and seasonal dynamics of macroalgal cover on a sandy intertidal flat using visible and near-infrared images from a time-lapse camera mounted on a tower. Benthic algae were identified using supervised, semi-supervised and unsupervised classification techniques, validated with monthly ground-truthing over one year. A supervised classification (based on maximum likelihood, using training areas identified in the field) performed best in discriminating between sediment, benthic diatom films and macroalgae, with highest spectral separability between macroalgae and diatoms in spring/summer. An automated unsupervised classification (based on the Normalised Differential Vegetation Index NDVI) allowed detection of daily changes in macroalgal coverage without the need for calibration. This method showed a bloom of macroalgae (filamentous green algae, Ulva sp.) in summer with > 60% cover, but with pronounced superimposed day-to-day variation in cover. Waves were a major factor in regulating macroalgal cover, but regrowth of the thalli after a summer storm was fast (2 weeks). Images and in situ data demonstrated that the protruding tubes of the polychaete Lanice conchilega facilitated both settlement (anchorage) and survival (resistance to waves) of the macroalgae. Thus, high-frequency, high resolution images revealed the mechanisms for regulating the dynamics in cover of the macroalgae and for their spatial structuring. Ramifications for the mode, timing, frequency and evaluation of monitoring macroalgae by field and remote sensing surveys are discussed.

Influence of vegetation on the infilling of a macrotidal embayment: examples from salt marshes and shingle spit of the Baie de Somme (North France)

NASA Astrophysics Data System (ADS)

Le Bot, Sophie; Forey, Estelle; Lafite, Robert; Langlois, Estelle

2015-04-01

As many estuaries in the English Channel, the Baie de Somme is currently filling with a mean seabed elevation between 1.3 and 1.8 cm/yr. Embankments and polders, as well as sea level rise, increase this natural accretion process, which leads to important modifications of environment uses. Interactions between vegetation and sediment dynamics constitute a key-point to consider, in order to better understand the infilling processes in estuaries. To estimate the effect of vegetation on these processes, two particular environments have been studied in the bay: (i) the mid salt marsh covered with Halimione portulacoides, associated with a silty sedimentation, and (ii) the shingle spit, that closes the bay from the South, on which the sea kale (Crambe maritime), a protected pioneer species, develops. Salt marshes progress with a rate of 5-10 m/yr (mean value calculated on the 1947-2011 period). Sedimentological analysis have been conducted on 9 cores (50cm long) collected in three Halimione communities of the bay. They are associated with a silty-dominated (38-84 micrometer) sedimentation under the influence of decantation processes. Rhythmicity is observed in the sedimentation, due to the repetition of a two-layer pattern, that includes a dark layer composed of vegetal rests and that would represent annual sedimentation. Annual sedimentation rates (0.7 to 5.8 cm/yr) are consistent with mean values previously recorded. The shingle spit progresses to the North under the influence of the littoral drift at a rate of 7 m/yr (mean value calculated on the 1947-2011 period). Sea kales are observed on parts formed since several years, above the level of the highest astronomical tides. TLS surveys and sedimentation bars have allowed to measure erosion/sedimentation volumes at the scale of the spit and of sea kale individuals, during spring 2013. Individuals of this species facilitate the trapping of sand, transported by winds from the intertidal flats. Sea kale thus contributes to the maintenance of sand at the surface of the spit during spring (development period of sea kales) and, probably to the progressive silting up of the spit on a longer-term. Thus, sea kale indirectly favours the filling of the bay through the building up and consolidation of the spit that, in turn, enhances sheltered conditions increasing the part of decantation processes in the sedimentation in the bay. (financial support by Région Haute-Normandie and Réseau d'Observation du Littoral Normand et Picard, ROLNP)

Spilled oil and infaunal activity - Modification of burrowing behavior and redistribution of oil

USGS Publications Warehouse

Clifton, H.E.; Kvenvolden, K.A.; Rapp, J.B.

1984-01-01

A series of experiments in Willapa Bay, Washington, indicates the degree to which the presence of spilled oil modifies the burrowing behavior of infauna and the extent to which the animals redistribute oil into intertidal sediment. Small amounts of North Slope crude oil introduced at low tide directly into burrow openings (mostly made by the crustacean Callianassa) resulted in a limited and temporary reduction in the number of burrow openings. In contrast, a layer of oil-saturated sand 1 cm thick buried about 5 cm below the sediment surface sharply reduced the number of burrow openings. After a year, the few new burrows penetrated only the margins of the experimental plot, and bioturbation below the buried oil-saturated sand layer declined dramatically. The experiments suggest that small amounts of oil temporarily stranded by tides in themselves have no long-range effect on burrowing behavior. The fauna, however, are capable of introducing measurable amounts of oil into the subsurface, where it is retained long after the rest of the stranded oil had washed away. A buried layer of oil-saturated sand greatly reduces infaunal activity; the oil presents an effective barrier that can persist for years. The oil incorporated into the sediment from burrow openings showed evidence of degradation after 7 months. In contrast the layer of buried oil remained essentially undergraded after a period of two years, even though oil in lower concentrations above the layer was degraded after a period of one year. This variation in degree of degradation of the buried oil, as well as the heterogeneity of oil distribution wherever the oil has been incorporated from the surface, emphasises the importance of careful sampling in any attempt to locate or monitor the presence of spilled oil in the substrate.In a series of experiments in Willapa Bay, Washington, small amounts of North Slope crude oil introduced at low tide directly into burrow openings resulted in a limited and temporary reduction in the number of burrow openings. In contrast, a layer of oil-saturated sand 1 cm thick buried about 5 cm below the sediment surface sharply reduced the number of burrow openings. After a year, the few new burrows penetrated only the margins of the experimental plot, and bioturbation below the buried oil-saturated sand layer declined dramatically. The experiments suggest that small amounts of oil temporarily stranded by tides in themselves have no long-range effect on burrowing behavior. The oil incorporated into the sediment from burrow openings showed evidence of degradation after 17 months. In contrast, the layer of buried oil remained essentially undegraded after a period of two years. Refs.

The denitrification paradox: The role of O2 in sediment N2O production

NASA Astrophysics Data System (ADS)

Barnes, Jonathan; Upstill-Goddard, Robert C.

2018-01-01

We designed a novel laboratory sediment flux chamber in which we maintained the headspace O2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (∼3 cm depth) and headspace O2 regulation (headspace: sediment/water ratio ∼9:1), net N2O production was highest at 1.2% O2 (sub-oxic; 32.3 nmol N2O m-2 d-1), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m-2 d-1) or 20.85% (ambient; 2.3 nmol N2O m-2 d-1) O2. In a longer-term sealed incubation (∼490 h) without O2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O2 or N2O up to ∼ 100 h; (ii) a quasi-linear, inverse correlation between O2 and N2O to ∼360 h, in which O2 declined to ∼2.1% and N2O rose to ∼7800 natm; (iii) over the following 50 h a slower O2 decline, to ∼1.1%, and a more rapid N2O increase, to ∼12000 natm; (iv) over the next 24 h a slowed O2 decline towards undetectable levels and a sharp fall in N2O to ∼4600 natm; (iv) a continued N2O decrease at zero O2, to ∼3000 natm by ∼ 490 h. These results show clearly that rapid N2O consumption (∼115 nmol m-2 d-1), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m-2 d-1 (NH4+ addition) and 0.4-2.2 nmol N2O m-2 d-1 (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O production in Tyne sediments. Highest N2O production occurred under sub-oxic headspace (∼1.2 O2%) incubations. Anoxic sediments where HD was isolated acted as periodic N2O sinks or relatively small sources of N2O. Our experimental approach thus gives valuable insight into the O2 effect on N2O fluxes from intertidal sediments.

Marine habitat mapping of the Milford Haven Waterway, Wales, UK: Comparison of facies mapping and EUNIS classification for monitoring sediment habitats in an industrialized estuary

NASA Astrophysics Data System (ADS)

Carey, Drew A.; Hayn, Melanie; Germano, Joseph D.; Little, David I.; Bullimore, Blaise

2015-06-01

A detailed map and dataset of sedimentary habitats of the Milford Haven Waterway (MHW) was compiled for the Milford Haven Waterway Environmental Surveillance Group (MHWESG) from seafloor images collected in May, 2012 using sediment-profile and plan-view imaging (SPI/PV) survey techniques. This is the most comprehensive synoptic assessment of sediment distribution and benthic habitat composition available for the MHW, with 559 stations covering over 40 km2 of subtidal habitats. In the context of the MHW, an interpretative framework was developed that classified each station within a 'facies' that included information on the location within the waterway and inferred sedimentary and biological processes. The facies approach provides critical information on landscape-scale habitats including relative location and inferred sediment transport processes and can be used to direct future monitoring activities within the MHW and to predict areas of greatest potential risk from contaminant transport. Intertidal sediment 'facies' maps have been compiled in the past for MHW; this approach was expanded to map the subtidal portions of the waterway. Because sediment facies can be projected over larger areas than individual samples (due to assumptions based on physiography, or landforms) they represent an observational model of the distribution of sediments in an estuary. This model can be tested over time and space through comparison with additional past or future sample results. This approach provides a means to evaluate stability or change in the physical and biological conditions of the estuarine system. Initial comparison with past results for intertidal facies mapping and grain size analysis from grab samples showed remarkable stability over time for the MHW. The results of the SPI/PV mapping effort were cross-walked to the European Nature Information System (EUNIS) classification to provide a comparison of locally derived habitat mapping with European-standard habitat mapping. Cross-walk was conducted by assigning each facies (or group of facies) to a EUNIS habitat (Levels 3 or 5) and compiling maps comparing facies distribution with EUNIS habitat distribution. The facies approach provides critical information on landscape-scale habitats including relative location and inferred sediment transport processes. The SPI/PV approach cannot consistently identify key species contained within the EUNIS Level 5 Habitats. For regional planning and monitoring efforts, a combination of EUNIS classification and facies description provides the greatest flexibility for management of dynamic soft-bottom habitats in coastal estuaries. The combined approach can be used to generate and test hypotheses of linkages between biological characteristics (EUNIS) and physical characteristics (facies). This approach is practical if a robust cross-walk methodology is developed to utilize both classification approaches. SPI/PV technology can be an effective rapid ground truth method for refining marine habitat maps based on predictive models.

Photoacclimatory Responses of Zostera marina in the Intertidal and Subtidal Zones.

PubMed

Park, Sang Rul; Kim, Sangil; Kim, Young Kyun; Kang, Chang-Keun; Lee, Kun-Seop

2016-01-01

Photoacclimatory responses of the seagrass Zostera marina in the intertidal and subtidal zones were investigated by measuring chlorophyll a fluorescence parameters, photosynthetic pigments, leaf δ13C values, and shoot morphology in two bay systems. Intertidal plants had higher carotenoid concentrations than subtidal plants to avoid photodamage under excess light conditions during the day. The maximum relative electron transport rate (rETRmax) and minimum saturation irradiance (Ek) of the intertidal plants were higher than those of the subtidal plants, whereas photosynthetic efficiency (α) and maximum quantum yield (Fv/Fm) were higher in subtidal plants. The intertidal plants also had significantly greater Stern-Volmer non-photochemical quenching (NPQ) than that of the subtidal plants. These results suggest that the subtidal plants photoacclimated to use limited light more efficiently, and the intertidal plants exhibited photosynthetic responses to minimize photodamage at excess irradiance. The δ13C values of leaf tissues were more negative in the intertidal plants than those in the subtidal plants, suggesting that the intertidal plants used atmospheric or dissolved CO2 for photosynthesis during emersion. Effective quantum yield (ΔF/Fm´) in the intertidal plants decreased more slowly after emersion than that in the subtidal plants, indicating higher desiccation tolerance of the intertidal plants. The intertidal plants also recovered more rapidly from desiccation damage than the subtidal plants, suggesting photosynthetic adaptation to desiccation stress. The photosynthetic plasticity of Z. marina in response to variable environmental conditions most likely allows this species to occur in the intertidal and subtidal zones.

Habitat heterogeneity: importance of salt marsh pools and high marsh surfaces to fish production in two Gulf of Maine salt marshes

Treesearch

R.A. MacKenzie; M. Dionne

2008-01-01

Both permanent high marsh pools and the intertidal surfaces of Spartina patens high marshes in southern Maine, USA, proved to be important habitat for resident mummichog Fundulus heteroclitus production. Manipulations of fish movement onto high marsh Surfaces revealed similar growth rates and production among fish that were (1) restricted to pools, (2) had access to...

Sediment-stabilizing and Destabilizing Ecoengineering Species from River to Estuary: the Case of the Scheldt System

NASA Astrophysics Data System (ADS)

Selakovic, S.; Cozzoli, F.; Leuven, J.; Van Braeckel, A.; Speybroeck, J.; Kleinhans, M. G.; Bouma, T.

2017-12-01

Interactions between organisms and landscape forming processes play an important role in evolution of coastal landscapes. In particular, biota has a strong potential to interact with important geomorphological processes such as sediment dynamics. Although many studies worked towards quantifying the impact of different species groups on sediment dynamics, information has been gathered on an ad hoc base. Depending on species' traits and distribution, functional groups of ecoengineering species may have differential effects on sediment deposition and erosion. We hypothesize that the spatial distributions of sediment-stabilizing and destabilizing species across the channel and along the whole salinity gradient of an estuary partly determine the planform shape and channel-shoal morphology of estuaries. To test this hypothesis, we analyze vegetation and macrobenthic data taking the Scheldt river-estuarine continuum as model ecosystem. We identify species traits with important effects on sediment dynamics and use them to form functional groups. By using linearized mixed modelling, we are able to accurately describe the distributions of the different functional groups. We observe a clear distinction of dominant ecosystem engineering functional groups and their potential effects on the sediment in the river-estuarine continuum. The first results of longitudinal cross section show the highest effects of stabilizing plant species in riverine and sediment bioturbators in weak polyhaline part of continuum. The distribution of functional groups in transverse cross sections shows dominant stabilizing effect in supratidal zone compared to dominant destabilizing effect in the lower intertidal zone. This analysis offers a new and more general conceptualization of distributions of sediment stabilizing and destabilizing functional groups and their potential impacts on sediment dynamics, shoal patterns, and planform shapes in river-estuarine continuum. We intend to test this in future modelling and experiments.

Decadal-timescale estuarine geomorphic change under future scenarios of climate and sediment supply

USGS Publications Warehouse

Ganju, N.K.; Schoellhamer, D.H.

2010-01-01

Future estuarine geomorphic change, in response to climate change, sea-level rise, and watershed sediment supply, may govern ecological function, navigation, and water quality. We estimated geomorphic changes in Suisun Bay, CA, under four scenarios using a tidal-timescale hydrodynamic/sediment transport model. Computational expense and data needs were reduced using the morphological hydrograph concept and the morphological acceleration factor. The four scenarios included (1) present-day conditions; (2) sea-level rise and freshwater flow changes of 2030; (3) sea-level rise and decreased watershed sediment supply of 2030; and (4) sea-level rise, freshwater flow changes, and decreased watershed sediment supply of 2030. Sea-level rise increased water levels thereby reducing wave-induced bottom shear stress and sediment redistribution during the wind-wave season. Decreased watershed sediment supply reduced net deposition within the estuary, while minor changes in freshwater flow timing and magnitude induced the smallest overall effect. In all future scenarios, net deposition in the entire estuary and in the shallowest areas did not keep pace with sea-level rise, suggesting that intertidal and wetland areas may struggle to maintain elevation. Tidal-timescale simulations using future conditions were also used to infer changes in optical depth: though sea-level rise acts to decrease mean light irradiance, decreased suspended-sediment concentrations increase irradiance, yielding small changes in optical depth. The modeling results also assisted with the development of a dimensionless estuarine geomorphic number representing the ratio of potential sediment import forces to sediment export forces; we found the number to be linearly related to relative geomorphic change in Suisun Bay. The methods implemented here are widely applicable to evaluating future scenarios of estuarine change over decadal timescales. ?? The Author(s) 2009.

Critical bifurcation of shallow microtidal landforms in tidal flats and salt marshes

PubMed Central

Fagherazzi, Sergio; Carniello, Luca; D'Alpaos, Luigi; Defina, Andrea

2006-01-01

Shallow tidal basins are characterized by extensive tidal flats and salt marshes that lie within specific ranges of elevation, whereas intermediate elevations are less frequent in intertidal landscapes. Here we show that this bimodal distribution of elevations stems from the characteristics of wave-induced sediment resuspension and, in particular, from the reduction of maximum wave height caused by dissipative processes in shallow waters. The conceptual model presented herein is applied to the Venice Lagoon, Italy, and demonstrates that areas at intermediate elevations are inherently unstable and tend to become either tidal flats or salt marshes. PMID:16707583

Statistical characterization of wind-wave induced sediment resuspension events in shallow tidal basins

NASA Astrophysics Data System (ADS)

D'Alpaos, A.; Carniello, L.; Rinaldo, A.

2013-12-01

Wind-wave induced erosion processes play a critical role on the morphodynamic evolution of shallow tidal landscapes. Both in the horizontal and in the vertical planes, patterns of wind-induced bottom shear stresses contribute to control the morphological and biological features of the tidal landscape, through the erosion of tidal-flat surfaces and of salt-marsh margins, the disruption of the polymeric microphytobenthic biofilm, and the increase in suspended sediment concentration which affects the stability of intertidal ecosystems. Towards the goal of developing a synthetic theoretical framework to represent wind wave-induced resuspension events and account for their erosional effects on the long-term biomorphodynamic evolution of tidal systems, we have employed a complete, coupled finite element model accounting for the role of wind waves and tidal currents on the hydrodynamic circulation in shallow basins. Our analysis of the characteristics of combined current and wave-induced exceedances in bottom shear stress over a given threshold for erosion, suggest that wind wave-induced resuspension events can be modeled as a marked Poisson process. Moreover, the analysis of wind-wave induced resuspension events for different historical configurations of the Venice Lagoon shows that the interarrival times of erosion events have decreased through the last two centuries, whereas the intensities of erosion events have increased. This allows us to characterize the threatening erosion and degradation processes that the Venice Lagoon has been experiencing since the beginning of the last century.

High-quality draft genome sequence of Sedimenticola selenatireducens strain AK4OH1T, a gammaproteobacterium isolated from estuarine sediment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Louie, Tiffany S.; Giovannelli, Donato; Yee, Nathan

Sedimenticola selenatireducens strain AK4OH1 T (= DSM 17993 T = ATCC BAA-1233 T) is a microaerophilic bacterium isolated from sediment from the Arthur Kill intertidal strait between New Jersey and Staten Island, NY. S. selenatireducens is Gram-negative and belongs to the Gammaproteobacteria. Strain AK4OH1 T was the first representative of its genus to be isolated for its unique coupling of the oxidation of aromatic acids to the respiration of selenate. It is a versatile heterotroph and can use a variety of carbon compounds, but can also grow lithoautotrophically under hypoxic and anaerobic conditions. Furthermore, the draft genome comprises 4,588,530 bpmore » and 4276 predicted protein-coding genes including genes for the anaerobic degradation of 4-hydroxybenzoate and benzoate. We report the main features of the genome of S. selenatireducens strain AK4OH1 T.« less

High-quality draft genome sequence of Sedimenticola selenatireducens strain AK4OH1T, a gammaproteobacterium isolated from estuarine sediment

DOE PAGES

Louie, Tiffany S.; Giovannelli, Donato; Yee, Nathan; ...

2016-09-08

Sedimenticola selenatireducens strain AK4OH1 T (= DSM 17993 T = ATCC BAA-1233 T) is a microaerophilic bacterium isolated from sediment from the Arthur Kill intertidal strait between New Jersey and Staten Island, NY. S. selenatireducens is Gram-negative and belongs to the Gammaproteobacteria. Strain AK4OH1 T was the first representative of its genus to be isolated for its unique coupling of the oxidation of aromatic acids to the respiration of selenate. It is a versatile heterotroph and can use a variety of carbon compounds, but can also grow lithoautotrophically under hypoxic and anaerobic conditions. Furthermore, the draft genome comprises 4,588,530 bpmore » and 4276 predicted protein-coding genes including genes for the anaerobic degradation of 4-hydroxybenzoate and benzoate. We report the main features of the genome of S. selenatireducens strain AK4OH1 T.« less

New Insights on Coastal Foredune Growth: The Relative Contributions of Marine and Aeolian Processes

NASA Astrophysics Data System (ADS)

Cohn, Nicholas; Ruggiero, Peter; de Vries, Sierd; Kaminsky, George M.

2018-05-01

Coastal foredune growth is typically associated with aeolian sediment transport processes, while foredune erosion is associated with destructive marine processes. New data sets collected at a high energy, dissipative beach suggest that total water levels in the collision regime can cause dunes to accrete—requiring a paradigm shift away from considering collisional wave impacts as unconditionally erosional. From morphologic change data sets, it is estimated that marine processes explain between 9% and 38% of annual dune growth with aeolian processes accounting for the remaining 62% to 91%. The largest wind-driven dune growth occurs during the winter, in response to high wind velocities, but out of phase with summertime beach growth via intertidal sandbar welding. The lack of synchronization between maximum beach sediment supply and wind-driven dune growth indicates that aeolian transport at this site is primarily transport, rather than supply, limited, likely due to a lack of fetch limitations.

Shallow subtidal survey of the Washington outer coast and Olympic National park to determine the distribution, fate, and effects of spilled bunker C fuel oil. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carney, D.; Kvitek, R.G.

1990-12-01

The report provides an evaluation of the impacts of the bunker C fuel oil spill on the shallow subtidal benthic communities of the Washington coast. The study is designed to provide a subtidal extension of the intertidal investigation performed by Battelle Laboratories. As such, the study sites and many of the methodologies are the same. There are four objectives of the study. They are: (1) to identify and define from existing data, the probable distribution of subtidal deposits along the Washington coast, (2) to document petroleum hydrocarbon contamination in shallow subtidal sediments in the Olympic National Park and along themore » Washington outer coast, (3) to characterize petroleum hydrocarbon contamination in molluscan and other species' tissues of opportunity in subtidal habitats along the Washington outer coast, and (4) to collect the initial faunal and sediment samples required for possible future analyses should oil-spill related hydrocarbons be detected from initial sediment and tissue analyses.« less

Photoacclimatory Responses of Zostera marina in the Intertidal and Subtidal Zones

PubMed Central

Park, Sang Rul; Kim, Sangil; Kim, Young Kyun; Kang, Chang-Keun; Lee, Kun-Seop

2016-01-01

Photoacclimatory responses of the seagrass Zostera marina in the intertidal and subtidal zones were investigated by measuring chlorophyll a fluorescence parameters, photosynthetic pigments, leaf δ13C values, and shoot morphology in two bay systems. Intertidal plants had higher carotenoid concentrations than subtidal plants to avoid photodamage under excess light conditions during the day. The maximum relative electron transport rate (rETRmax) and minimum saturation irradiance (Ek) of the intertidal plants were higher than those of the subtidal plants, whereas photosynthetic efficiency (α) and maximum quantum yield (Fv/Fm) were higher in subtidal plants. The intertidal plants also had significantly greater Stern–Volmer non-photochemical quenching (NPQ) than that of the subtidal plants. These results suggest that the subtidal plants photoacclimated to use limited light more efficiently, and the intertidal plants exhibited photosynthetic responses to minimize photodamage at excess irradiance. The δ13C values of leaf tissues were more negative in the intertidal plants than those in the subtidal plants, suggesting that the intertidal plants used atmospheric or dissolved CO2 for photosynthesis during emersion. Effective quantum yield (ΔF/Fm´) in the intertidal plants decreased more slowly after emersion than that in the subtidal plants, indicating higher desiccation tolerance of the intertidal plants. The intertidal plants also recovered more rapidly from desiccation damage than the subtidal plants, suggesting photosynthetic adaptation to desiccation stress. The photosynthetic plasticity of Z. marina in response to variable environmental conditions most likely allows this species to occur in the intertidal and subtidal zones. PMID:27227327

Environmental and eelgrass response to dike removal: Nisqually River Delta (2010–14)

USGS Publications Warehouse

Takesue, Renee K.

2016-10-03

Restoration of tidal flows to formerly diked marshland can alter land-to-sea fluxes and patterns of accumulation of terrestrial sediment and organic matter, and these tidal flows can also affect existing nearshore habitats. Dikes were removed from 308 hectares (ha) of the Nisqually National Wildlife Refuge on the Nisqually River Delta in south Puget Sound, Washington, in fall 2009 to improve habitat for wildlife, such as juvenile salmon. Ecologically important intertidal and subtidal eelgrass (Zostera marina) beds grow on the north and west margins of the delta. The goal of this study was to understand long-term changes in eelgrass habitat and their relation to dike removal. Sediment and eelgrass properties were monitored annually in May from 2010 to 2014 at two sites on the west side of the Nisqually River Delta along McAllister Creek, a spring-fed creek near two restored tidal channels. In May 2014, the mean canopy height of eelgrass was the same as in previous years in an 8-ha bed extending to the Nisqually River Delta front, but mean canopy height was 20 percent lower in a 0.3-ha eelgrass bed closer to the restored marsh when compared to mean canopy height of eelgrass in May 2010, 6 months after dike removal was completed. Over 5 years, the amount of eelgrass leaf area per square meter (m2) in the 8-ha bed increased slightly, and surface-sediment grain size became finer. In contrast, in the 0.3-ha bed, eelgrass leaf area per m2 decreased by 45 percent, and surface sediment coarsened. Other potential stressors, including sediment pore water reduction-oxidation potential (redox) and hydrogen sulfide (H2S) concentration in the eelgrass rhizosphere, or root zone, were below levels that negatively affect eelgrass growth and therefore did not appear to be environmental stressors on plants. Eelgrass biomass partitioning, though less favorable in the 8-ha eelgrass bed compared to the 0.3-ha one, was well above the critical above-ground to below-ground biomass ratio of 2:1 for Z. marina, an indication that these plants were not at risk of a carbon deficit during low-light conditions. After 5 years, nearshore changes associated with the restoration of tidal flows to formerly diked marshes of the Nisqually River Delta appeared to have little impact on the large eelgrass bed extending from Luhr Beach to the Nisqually River Delta front; however, restoration appears to be contributing to the decline of a small eelgrass bed closer to the restoration area.

Lateral trends and vertical sequences in estuarine sediments, Willapa Bay, Washington

USGS Publications Warehouse

Clifton, H. Edward; Phillips, L.

1980-01-01

Willapa Bay is a sizable estuary on the southern coast of Washington- Relatively unmodified in a geologic sense by human activity the bay provides an excellent example of modern depositional facies in an estuarine setting. Studies of these deposits indicate that consistent lateral trends exist in sediment texture and sedimentary structures. The texture changes from sandy at the mouth of the bay to muddy in its upper parts. In any part of the bay , sediment is coarsest in the channel bottoms, where lag deposits accumulate. The sediment tends to fine in an upslope direction and is finest in supratidal flat deposits of silt and clay. The nature of sedimentary structures depends on the combination of physical and biological processes and sediment textures. Bedforms exist wherever the bed is sandy. In the main tidal channels sandwaves and dunes up to 4 meters high occur. In tributary channels and at the margins of the main channel, at shallower depths and under less intense currents , the structures are generally less than a meter high. Current ripples occur in t he sandy bed of all of the tidal channels and in runoff channels cross the tidal flat. Symmetric long-crested ripples are produced by wave action over the sandy intertidal flat. Internal structures in the bay's sediment depend not only on the nature of the bedform but also on the rate of bioturbation relative to physical processes. Under fields of large sandwaves or dunes, medium- to large-scale tabular and trough crossbedding predominates. This crossbedding generally is unidirectional, reflecting the locally dominant current (ebb or flood). Ripple bedding predominates elsewhere in sandy sediment within the channels. Where sand transport is diminished, as on the floor of the upper tributary channels, bioturbation exceeds the rate of production of physical structures and bedding is destroyed. The depositional banks in such areas tend to be sites of rapid sediment accumulation and bedding in the form of interlayered sand (commonly ripple bedded) and mud persists. On intertidal flats the sediment accumulates slowly and bioturbation erases nearly all physical structures. Bedding is preserved only where deposition is locally rapid , as in topographic depressions or on the depositional banks of runoff channels, or where faunal activity is inhibited, as beneath mounds of blue-green algae. The rate of sedimentation is slower still on the supratidal flats, but the general paucity of faunal activity allows the preservation of thin alternations of fine sand , silt or clay. The lateral migration of the tidal channels produces vertical sequences in which topographically higher facies are superposed on one another. Near the mouth of the estuary the upward sequence: lag deposit — crossbedded sand — ripple or planar-bedded sand is typical. The crossbedding shows a general upward decrease in thickness and a progression from trough to tabular units. In the main tidal channel - in the central estuary and in sandy tributary channels, the typical vertical sequence resembles that near the mouth , with the exception that the sequence is capped by bioturbated sandy or muddy tide flat deposits. In the upper estuary , where muddy sediment predominates, a typical sequence shows the progression-. bioturbated lag deposit — gently dipping interlaminated sand and mud layers of the accretionary bank — bioturbated mud flat deposits — thinly laminated fine supratidal deposits.

A geomorphic and tectonic model for the formation of the flight of Holocene marine terraces at Mahia Peninsula, New Zealand

NASA Astrophysics Data System (ADS)

Berryman, Kelvin; Clark, Kate; Cochran, Ursula; Beu, Alan; Irwin, Sarah

2018-04-01

At Table Cape, Mahia Peninsula, North Island, New Zealand, four marine terraces have been uplifted coseismically during the past 3500 years. Detailed facies assessment of the terrace coverbed sequence coupled with identification of modern analogues on the active shore platform were used to infer the process of marine terrace formation and to estimate the timing and amount of past uplift events (earthquakes). The modern platform can be subdivided into seven depositional zones: subtidal, outer platform, intertidal sand pockets, inner platform, high-tide, mid-storm, and storm beach. Terrace coverbeds were characterised from two trenches excavated across the full width of the uplifted terrace sequence. Off-lapping packages of high tidal, mid-storm, and storm beach sediments were most common. Outer platform sediments occurred only rarely near the base of some uplifted shore platforms. Overlying the marine sediments were near-horizontal terrestrial deposits of airfall tephra (on the two highest terraces), subsoil, topsoil, rare wedges of colluvial sediment (slopewash) shed from terrace risers, and an anomalous deposit possibly emplaced by a tsunami. Fifty-one radiocarbon ages, obtained from molluscs in the marine coverbeds, showed a general pattern of seaward-younging across the coastal plain and across each terrace and a less pronounced pattern of decreasing age upward in each coverbed sequence. The distinctive stepped geomorphology of the terraces, the facies and age structure of the terrace deposits and historical earthquake causation of similar terraces elsewhere in New Zealand provided the data to invoke an earthquake-driven model for terrace formation. Marine terrace development following an uplift event involved rapid cutting of a new intertidal shore platform and generally regressive deposition of high-tide to storm beach deposits. Following further uplift, the platform became a geomorphic terrace (above marine influence) and was then mantled by terrestrial sediments. On the two highest terraces at Table Cape, airfall tephras mantling the marine coverbeds provided a minimum age for terrace uplift. The youngest radiocarbon ages from high-tide deposits high in the stratigraphy and near the seaward edge of each terrace provided the best estimates for the timing of uplift. Based on the new radiocarbon ages and the constraining airfall tephra ages, we revised the earthquake ages to 3530-3350, 1810-1730, 1560-1300 and 300-100 cal. YBP. Associated best estimates of the coseismic uplift amounts were 2.1, 1.4, 1.8, and 3.1 m respectively, once we accounted for eustatic sea level changes through the late Holocene.

Effects of conversion of mangroves into gei wai ponds on accumulation, speciation and risk of heavy metals in intertidal sediments.

PubMed

Li, Rongyu; Qiu, Guo Yu; Chai, Minwei; Shen, Xiaoxue; Zan, Qijie

2018-06-23

Mangroves are often converted into gei wai ponds for aquaculture, but how such conversion affects the accumulation and behavior of heavy metals in sediments is not clear. The present study aims to quantify the concentration and speciation of heavy metals in sediments in different habitats, including gei wai pond, mangrove marsh dominated by Avicennia marina and bare mudflat, in a mangrove nature reserve in South China. The results showed that gei wai pond acidified the sediment and reduced its electronic conductivity and total organic carbon (TOC) when compared to A. marina marsh and mudflat. The concentrations of Cd, Cu, Zn and Pb at all sediment depths in gei wai pond were lower than the other habitats, indicating gei wai pond reduced the fertility and the ability to retain heavy metals in sediment. Gei wai pond sediment also had a lower heavy metal pollution problem according to multiple evaluation methods, including potential ecological risk coefficient, potential ecological risk index, geo-accumulation index, mean PEL quotients, pollution load index, mean ERM quotients and total toxic unit. Heavy metal speciation analysis showed that gei wai pond increased the transfer of the immobilized fraction of Cd and Cr to the mobilized one. According to the acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) analysis, the conversion of mangroves into gei wai pond reduced values of ([SEM] - [AVS])/f oc , and the role of TOC in alleviating heavy metal toxicity in sediment. This study demonstrated the conversion of mangrove marsh into gei wai pond not only reduced the ecological purification capacity on heavy metal contamination, but also enhanced the transfer of heavy metals from gei wai pond sediment to nearby habitats.

Coastal lithofacies and biofacies associated with syndepositional dolomitization and silicification (Draken Formation, Upper Riphean, Svalbard).

PubMed

Fairchild, I J; Knoll, A H; Swett, K

1991-01-01

The Draken Formation (120-250 m) of northeast Spitsbergen (Svalbard) forms part of a thick Upper Proterozoic carbonate platform succession. It consists predominantly of intraformational dolomitic conglomerates, with excellent textural preservation. Six main lithofacies were recognized in the field: quartz sandstones, stromatolitic mats, conglomerates with silicified intraclasts, dolostone conglomerates with desiccated mudrocks, oolitic/pisolitic grainstones and fenestral dolostones. A series of five main gradational biofacies were recognized from silicified (and rare calcified) microfossils. Biofacies 1 represents low-energy subtidal benthos (erect filaments) and plankton (acritarchs and vase-shaped microfossils) whereas biofacies 2 to 5 are microbial mat assemblages (with filamentous mat-builders, and associated dwellers and washed-in plankton) ranging from basal intertidal to high intertidal/supratidal. Colour values (a measure of the lightness of the colour shade) of sawn rock samples were quantified using a Munsell chart, and exhibit a pronounced variation (means of major groups varying from 4.0 to 5.95) across the spectrum of subtidal to supratidal sediments as inferred from other criteria. The lightening in progressively more exposed sediments is related to lowering of organic carbon contents, probably mainly by oxidation. Six types of early cement have been recognized. Calcite microspar (type 1) is common as a subtidal cement in many Proterozoic formations, whereas types 2 (subtidal isopachous fringes), 3 (subtidal hardground dolomicrite) and 4 (intertidal meniscus dolomicrite) are very similar to Phanerozoic examples except for their dolomitic mineralogy. Types 5 and 6 are complex and variable dolomite growths associated with expansion and replacive phenomena. They characterize the fenestral lithofacies and compare with modern supratidal cements. Consideration of diagenetic fabrics and truncation textures of intraclasts indicates that leaching, dolomitization, silicification were all significant syndepositional processes altering the original metastable carbonates. The data set provides evidence for a spectrum of peritidal environments including ooid shoals, protected subtidal, tidal sandflats and protected carbonate mudflats. Different sections show a preponderance of particular facies. The coastal lithofacies continuum was completely dolomitized, unlike offshore to ooid shoal facies of adjacent formations. Dolomitization thus bears a relationship to depositional bathymetry. Although hydrodynamics clearly have a role, the potential importance of whiting precipitation in raising Mg/Ca in marginal marine environments is also stressed.

Coastal lithofacies and biofacies associated with syndepositional dolomitization and silicification (Draken Formation, Upper Riphean, Svalbard)

NASA Technical Reports Server (NTRS)

Fairchild, I. J.; Knoll, A. H.; Swett, K.

1991-01-01

The Draken Formation (120-250 m) of northeast Spitsbergen (Svalbard) forms part of a thick Upper Proterozoic carbonate platform succession. It consists predominantly of intraformational dolomitic conglomerates, with excellent textural preservation. Six main lithofacies were recognized in the field: quartz sandstones, stromatolitic mats, conglomerates with silicified intraclasts, dolostone conglomerates with desiccated mudrocks, oolitic/pisolitic grainstones and fenestral dolostones. A series of five main gradational biofacies were recognized from silicified (and rare calcified) microfossils. Biofacies 1 represents low-energy subtidal benthos (erect filaments) and plankton (acritarchs and vase-shaped microfossils) whereas biofacies 2 to 5 are microbial mat assemblages (with filamentous mat-builders, and associated dwellers and washed-in plankton) ranging from basal intertidal to high intertidal/supratidal. Colour values (a measure of the lightness of the colour shade) of sawn rock samples were quantified using a Munsell chart, and exhibit a pronounced variation (means of major groups varying from 4.0 to 5.95) across the spectrum of subtidal to supratidal sediments as inferred from other criteria. The lightening in progressively more exposed sediments is related to lowering of organic carbon contents, probably mainly by oxidation. Six types of early cement have been recognized. Calcite microspar (type 1) is common as a subtidal cement in many Proterozoic formations, whereas types 2 (subtidal isopachous fringes), 3 (subtidal hardground dolomicrite) and 4 (intertidal meniscus dolomicrite) are very similar to Phanerozoic examples except for their dolomitic mineralogy. Types 5 and 6 are complex and variable dolomite growths associated with expansion and replacive phenomena. They characterize the fenestral lithofacies and compare with modern supratidal cements. Consideration of diagenetic fabrics and truncation textures of intraclasts indicates that leaching, dolomitization, silicification were all significant syndepositional processes altering the original metastable carbonates. The data set provides evidence for a spectrum of peritidal environments including ooid shoals, protected subtidal, tidal sandflats and protected carbonate mudflats. Different sections show a preponderance of particular facies. The coastal lithofacies continuum was completely dolomitized, unlike offshore to ooid shoal facies of adjacent formations. Dolomitization thus bears a relationship to depositional bathymetry. Although hydrodynamics clearly have a role, the potential importance of whiting precipitation in raising Mg/Ca in marginal marine environments is also stressed.

Environmental radiation and potential ecological risk levels in the intertidal zone of southern region of Tamil Nadu coast (HBRAs), India.

PubMed

Punniyakotti, J; Ponnusamy, V

2018-02-01

Natural radioactivity content and heavy metal concentration in the intertidal zone sand samples from the southern region of Tamil Nadu coast, India, have been analyzed using gamma ray spectrometer and ICP-OES, respectively. From gamma spectral analysis, the average radioactivity contents of 238 U, 232 Th, and 40 K in the intertidal zone sand samples are 12.13±4.21, 59.03±4.26, and 197.03±26.24Bq/kg, respectively. The average radioactivity content of 232 Th alone is higher than the world average value. From the heavy metal analysis, the average Cd, Cr, Cu, Ni, Pb, and Zn concentrations are 3.1, 80.24, 82.84, 23.66, 91.67, and 137.07ppm, respectively. The average Cr and Ni concentrations are lower, whereas other four metal (Cd, Cu, Pb, and Zn) concentrations are higher than world surface rock average values. From pollution assessment parameter values, the pollution level is "uncontaminated to moderately contaminated" in the study area. Copyright © 2017 Elsevier Ltd. All rights reserved.

Kilop Cretaceous Hardground (Kale, Gümüshane, NE Turkey):description and origin

NASA Astrophysics Data System (ADS)

Eren, Muhsin; Tasli, Kemal

2002-06-01

A hardground surface is well exposed in the Kilop area of Kale (Gümüshane, NE Turkey) which forms part of the Eastern Pontides. Here, the hardground is underlain by shallow water Lower Cretaceous limestones, and overlain by Upper Cretaceous red limestones/marls which contains a planktonic microfauna including Globotruncanidae. In the field, the recognition of the hardground is based on the presence of extensive burrows (especially vertical burrows), the encrusting rudistid bivalve Requienia, neptunian-dykes with infills of pelagic sediments and synsedimentary faults. Skolithos and Thalassinoides-type burrows are present. Some burrow walls show iron hydroxide-staining. The extensive burrowing occurred prior to lithification. On the other hand, the neptunian-dykes and synsedimentary faults, which cut the hard ground, occurred after the lithification. These features indicate the progressive hardening of the substrate. The burrowed limestone consists of an intrabioclastic peloidal grainstone which was deposited in an intertidal to shallow, subtidal, moderate to relatively high energy environment. The peloidal limestone shows little or no evidence of submarine cementation, characterized by only scarce relics of isopachous cement rims of bladed calcite spar. The grainstone cement is composed predominantly of blocky calcite and overgrowth calcite cements on the echinoid-fragments. The origin of this cement is controversial. Biostratigraphic analysis of the limestones demonstrates that there is a marked stratigraphic gap (hiatus), spanning the Aptian to the Santonian, in the Cretaceous of the Kilop area. The formation of the Kilop Hardground is related to the break-up and subsidence of the Eastern Pontides carbonate platform during the formation of the Black Sea backarc basin. Hardground development was initiated in a shallow marine environment of slow sedimentation and with moderate to high energy indicating slow subsidence. Later, the hardground subsided abruptly, as shown by the deposition of pelagic sediments on the hardground surface. During drowning, the Kilop area was converted to a bypass-margin where currents were effective. The formation of the hardground may also have been associated with an eustatic rise in sea-level.

Responses of estuarine circulation and salinity to the loss of intertidal flats – A modeling study

DOE PAGES

Yang, Zhaoqing; Wang, Taiping

2015-08-25

Intertidal flats in estuaries are coastal wetlands that provide critical marine habitats to support wide ranges of marine species. Over the last century many estuarine systems have experienced significant loss of intertidal flats due to anthropogenic impacts. This paper presents a modeling study conducted to investigate the responses of estuarine hydrodynamics to the loss of intertidal flats caused by anthropogenic actions in Whidbey Basin of Puget Sound on the northwest coast of North America. Changes in salinity intrusion limits in the estuaries, salinity stratification, and circulation in intertidal flats and estuaries were evaluated by comparing model results under the existingmore » baseline condition and the no-flat condition. Model results showed that loss of intertidal flats results in an increase in salinity intrusion, stronger mixing, and a phase shift in salinity and velocity fields in the bay front areas. Model results also indicated that loss of intertidal flats enhances two-layer circulation, especially the bottom water intrusion. Loss of intertidal flats increases the mean salinity but reduces the salinity range in the subtidal flats over a tidal cycle because of increased mixing. Salinity intrusion limits extend upstream in all three major rivers discharging into Whidbey Basin when no intertidal flats are present. Changes in salinity intrusion and estuarine circulation patterns due to loss of intertidal flats affect the nearshore habitat and water quality in estuaries and potentially increase risk of coastal hazards, such as storm surge and coastal flooding. Furthermore, model results suggested the importance of including intertidal flats and the wetting-and-drying process in hydrodynamic simulations when intertidal flats are present in the model domain.« less

Mychonastes desiccatus Brown sp. nova (Chlorococcales, Chlorophyta)--an intertidal alga forming achlorophyllous desiccation-resistant cysts

NASA Technical Reports Server (NTRS)

Margulis, L.; Hinkle, G.; McKhann, H.; Moynihan, B.

1988-01-01

An intertidal Chlorella-like alga Mychonastes desiccatus Brown sp. nova, capable of forming achlorophyllous desiccation-resistant cysts, has been grown in unialgal culture. This small alga was first isolated from a dried sample of a well-studied microbial mat. The mat, located at North Pond, Laguna Figueroa, San Quintin, Baja California, Mexico, is a vertically-stratified microbial community which forms laminated sediments. Morphology, pigment composition and G+C content are within the range typical for the genus Chlorella s. 1. Unlike other chlorellae, however, upon desiccation M. desiccatus forms an achlorophyllous, lipid-filled cyst (thick-walled resting stage) in which no plastid is evident. Rewetting leads to chloroplast differentiation, excystment and recovery of the fully green alga. During desiccation, sporopollenin is deposited within a thickening cell wall. Encystment cannot be induced by growth in the dark. The formation of desiccation-induced cysts allows the alga to survive frequent and intermittent periods of dryness. These chlorellae tolerate wide ranges of acidity and temperature; they both grow and form cysts in media in which sodium ions are replaced with potassium. Although the cysts tolerate crystalline salts, the cell grow optimally in concentrations corresponding from three-quarters to full-strength seawater.

No estuarine intertidal bathymetry? No worries! Estimating intertidal depth contours from readily available GIS data

EPA Science Inventory

The importance of littoral elevation to the distribution of intertidal species has long been a cornerstone of estuarine ecology and its historical importance to navigation cannot be understated. However, historically, intertidal elevation measurements have been sparse likely due ...

Pricia antarctica gen. nov., sp. nov., a member of the family Flavobacteriaceae, isolated from Antarctic intertidal sediment.

PubMed

Yu, Yong; Li, Hui-Rong; Zeng, Yin-Xin; Sun, Kun; Chen, Bo

2012-09-01

A yellow-coloured, rod-shaped, Gram-reaction- and Gram-staining-negative, non-motile and aerobic bacterium, designated strain ZS1-8(T), was isolated from a sample of sandy intertidal sediment collected from the Antarctic coast. Flexirubin-type pigments were absent. In phylogenetic analyses based on 16S rRNA gene sequences, strain ZS1-8(T) formed a distinct phyletic line and the results indicated that the novel strain should be placed in a new genus within the family Flavobacteriaceae. In pairwise comparisons between strain ZS1-8(T) and recognized species, the levels of 16S rRNA gene sequence similarity were all <93.3 %. The strain required Ca(2+) and K(+) ions as well as NaCl for growth. Optimal growth was observed at pH 7.5-8.0, 17-19 °C and with 2-3 % (w/v) NaCl. The major fatty acids were iso-C(15 : 1) G, iso-C(15 : 0), summed feature 3 (iso-C(15 : 0) 2-OH and/or C(16 : 1)ω7c), an unknown acid with an equivalent chain-length of 13.565 and iso-C(17 : 0) 3-OH. The major respiratory quinone was MK-6. The predominant polar lipid was phosphatidylethanolamine. The genomic DNA G+C content was 43.9 mol%. Based on the phylogenetic, phenotypic and chemotaxonomic data, strain ZS1-8(T) represents a novel species in a new genus in the family Flavobacteriaceae for which the name Pricia antarctica gen. nov., sp. nov. is proposed. The type strain of the type species is ZS1-8(T) (= JCM 17291(T) = DSM 23421(T)).

Spatial variability of metal bioaccumulation in estuarine killifish (Fundulus heteroclitus) at the Callahan Mine Superfund site, Brooksville, ME

PubMed Central

Buckman, Kate L.; Bugge, Deenie M.; Chen, Celia Y.

2013-01-01

The former Callahan Mine Site in Brooksville, ME is an open-pit, hardrock mine site in an intertidal system, providing a unique opportunity to evaluate how metal-enriched sediments and overlying water impact estuarine food webs. Cu, Zn, Cd, and Pb concentrations in sediment, whole water, and Atlantic killifish (Fundulus heteroclitus) were evaluated at sites in Goose Pond (the Callahan Mine Site) and at reference sites. The metal concentrations of sediment, water, and fish were spatially distinct and significantly higher at the Mine Site than in the reference estuary. Sediment concentrations were particularly elevated and were above probable effects levels (PEL) for all four metals adjacent to the tailings pile. Even in this well-mixed system, water metal concentrations were significantly elevated adjacent to the tailings pile and the concentrations of Cu and Zn were above ambient water quality criteria (AWQC) for chronic marine exposure. Neither organic matter in the sediment nor salinity or pH of the water explained the metal concentrations. Adjacent to the tailings pile, killifish body burdens were elevated and were significantly related to both sediment and aqueous concentrations. In conclusion, (1) the contaminated sediment and seepage from the tailings impoundment and waste rock pile 3 create a continual flux of metals into the water column, (2) the metals are bioavailable and are bioconcentrating as evident in the killifish tissue concentrations, and (3) Callahan Mine is directly affecting metal bioaccumulation in fauna residing in the Goose Pond estuary and, potentially, in Penobscot Bay via the ‘trophic nekton relay.’ PMID:24022459

Spatial variability of metal bioaccumulation in estuarine killifish (Fundulus heteroclitus) at the Callahan mine superfund site, Brooksville, ME.

PubMed

Broadley, Hannah J; Buckman, Kate L; Bugge, Deenie M; Chen, Celia Y

2013-11-01

The former Callahan Mine Site in Brooksville, ME, is an open-pit, hardrock mine site in an intertidal system, thus providing a unique opportunity to evaluate how metal-enriched sediments and overlying water impact estuarine food webs. Copper, zinc, cadmium, and lead concentrations in sediment, whole water, and Atlantic killifish (Fundulus heteroclitus) were evaluated at sites in Goose Pond (GP; Callahan Mine Site) and at reference sites. The metal concentrations of sediment, water, and fish were spatially distinct and significantly greater at the mine site than in the reference estuary. Sediment concentrations were particularly elevated and were above probable effects levels for all four metals adjacent to the tailings pile. Even in this well-mixed system, water metal concentrations were significantly elevated adjacent to the tailings pile, and concentrations of Cu and Zn were above ambient water-quality criteria for chronic marine exposure. Neither organic matter in the sediment nor salinity or pH of the water explained the metal concentrations. Adjacent to the tailings pile, killifish metal body burdens were elevated and were significantly related to both sediment and aqueous concentrations. In conclusion, (1) the contaminated sediment and seepage from the tailings impoundment and waste rock pile no. 3 create a continual flux of metals into the water column, (2) the metals are bioavailable and bioconcentrating as evident in the killifish tissue concentrations, and (3) Callahan Mine is directly affecting metal bioaccumulation in fauna residing in the GP estuary and, potentially, in Penobscot Bay by the way of “trophic nekton relay.”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhaoqing; Wang, Taiping

Intertidal flats in estuaries are coastal wetlands that provide critical marine habitats to support wide ranges of marine species. Over the last century many estuarine systems have experienced significant loss of intertidal flats due to anthropogenic impacts. This paper presents a modeling study conducted to investigate the responses of estuarine hydrodynamics to the loss of intertidal flats caused by anthropogenic actions in Whidbey Basin of Puget Sound on the northwest coast of North America. Changes in salinity intrusion limits in the estuaries, salinity stratification, and circulation in intertidal flats and estuaries were evaluated by comparing model results under the existingmore » baseline condition and the no-flat condition. Model results showed that loss of intertidal flats results in an increase in salinity intrusion, stronger mixing, and a phase shift in salinity and velocity fields in the bay front areas. Model results also indicated that loss of intertidal flats enhances two-layer circulation, especially the bottom water intrusion. Loss of intertidal flats increases the mean salinity but reduces the salinity range in the subtidal flats over a tidal cycle because of increased mixing. Salinity intrusion limits extend upstream in all three major rivers discharging into Whidbey Basin when no intertidal flats are present. Changes in salinity intrusion and estuarine circulation patterns due to loss of intertidal flats affect the nearshore habitat and water quality in estuaries and potentially increase risk of coastal hazards, such as storm surge and coastal flooding. Furthermore, model results suggested the importance of including intertidal flats and the wetting-and-drying process in hydrodynamic simulations when intertidal flats are present in the model domain.« less

Changes in the location of biodiversity-ecosystem function hot spots across the seafloor landscape with increasing sediment nutrient loading.

PubMed

Thrush, Simon F; Hewitt, Judi E; Kraan, Casper; Lohrer, A M; Pilditch, Conrad A; Douglas, Emily

2017-04-12

Declining biodiversity and loss of ecosystem function threatens the ability of habitats to contribute ecosystem services. However, the form of the relationship between biodiversity and ecosystem function (BEF) and how relationships change with environmental change is poorly understood. This limits our ability to predict the consequences of biodiversity loss on ecosystem function, particularly in real-world marine ecosystems that are species rich, and where multiple ecosystem functions are represented by multiple indicators. We investigated spatial variation in BEF relationships across a 300 000 m 2 intertidal sandflat by nesting experimental manipulations of sediment pore water nitrogen concentration into sites with contrasting macrobenthic community composition. Our results highlight the significance of many different elements of biodiversity associated with environmental characteristics, community structure, functional diversity, ecological traits or particular species (ecosystem engineers) to important functions of coastal marine sediments (benthic oxygen consumption, ammonium pore water concentrations and flux across the sediment-water interface). Using the BEF relationships developed from our experiment, we demonstrate patchiness across a landscape in functional performance and the potential for changes in the location of functional hot and cold spots with increasing nutrient loading that have important implications for mapping and predicating change in functionality and the concomitant delivery of ecosystem services. © 2017 The Author(s).

Long-term monitoring and modeling of the mass transfer of polychlorinated biphenyls in sediment following pilot-scale in-situ amendment with activated carbon.

PubMed

Cho, Yeo-Myoung; Werner, David; Choi, Yongju; Luthy, Richard G

2012-03-15

The results of five years of post-treatment monitoring following in-situ activated carbon (AC) placement for stabilization of polychlorinated biphenyls (PCBs) at an inter-tidal mudflat adjacent to Hunters Point Shipyard, San Francisco Bay, CA, USA are reported in this paper. After five years, AC levels of the sediment cores were comparable to those at earlier sampling times. Passive sampler uptake validated the benefit of the AC amendment with a strong local sorbent dose-response relationship. The PCB uptakes in passive samplers decreased up to 73% with a 3.7 dry wt.% AC dose after five years, confirming the temporal enhancement of the amendment benefit from a 19% reduction with a 4.4% dose observed within one month. The long-term effectiveness of AC, the local AC dose response, the impact of fouling by NOM, the spatial heterogeneity of AC incorporation, and the effects of advective sediment pore-water movement are discussed with the aid of a PCB mass transfer model. Modeling and experimental results indicated that the homogeneous incorporation of AC in the sediment will significantly accelerate the benefit of the treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Environmental-economic evaluation of the filling and reclamation process in the bay of Santander, Spain

NASA Astrophysics Data System (ADS)

Cendrero, A.; Díaz de Terán, J. R.; Salinas, J. M.

1981-11-01

The historical development of a process of reclamation of intertidal areas in an estuary has been quantitatively studied by means of old engravings, maps, navagation charts, and aerial photographs. These show that about 83 percent of the natural coastline of the estuary has disappeared, nearly two-thirds of its intertidal area has been covered, and over 40 percent of its volume has been lost. The rate of this artificial process is several tens of times faster than that of the natural sedimentation. Extrapolation of the observed trends shows that, if these continue, the intertidal areas would disappear completely in 31 to 105 years. Theoretical calculations based on comparisons with other estuaries show that the accumulated loss in the productivity of living matter (in the form of primary producers), since the process started about 140 years ago, could reach 1.5·1010 kg. This could represent, considering several possible food chains, the equivalent of the food necessary to sustain several thousand people for life. An economic analysis of the impact of the process has been made by considering, first, the decrease in fish and shellfish catches in the bay (using historical data and data about present clam productivity) and the decrease in its aesthetic quality and recreational potential. These were determined by means of interviews with the population to obtain a “demand curve” for the willingness to pay for the preservation and use of the bay. Second, the price of the man-made land obtained was considered. The data obtained show that the economic losses would offset the benefits within 10 to 30 years.

A Novel Approach to Mapping Intertidal Areas Using Shore-Based X-band Marine Radar

NASA Astrophysics Data System (ADS)

Bird, Cai; Bell, Paul

2014-05-01

Monitoring the morphology of coastal zones in response to high energy weather events and changing patterns of erosion and deposition over time is vital in enabling effective decision-making at the coast. Common methods of mapping intertidal bathymetry currently include vessel-based sonar and airborne LiDAR surveys, which are expensive and thus not routinely collected on a continuous basis. Marine radar is a ubiquitous technology in the marine industry and many ports operate a system to guide ships into port, this work aims to utilise this already existing infrastructure to determine bathymetry over large intertidal areas, currently up to 4 km from the radar. Standard X-band navigational radar has been used in the marine industry to measure hydrodynamics and derive bathymetry using empirical techniques for several decades. Methods of depth mapping thus far have relied on the electromagnetic backscattering from wind-roughened water surface, which allows a radar to gather sea surface image data but requires the waves to be clearly defined. The work presented here does not rely on identifying and measuring these spatial wave features, which increases the robustness of the method. Image data collected by a 9.4Ghz Kelvin Hughes radar from a weather station on Hilbre Island at the mouth of the River Dee estuary, UK were used in the development of this method. Image intensity at each pixel is a function of returned electromagnetic energy, which in turn can be related to the roughness of the sea surface. Images collected over time periods of 30 minutes show general patterns of wave breaking and mark the advance and retreat of the waterline in accordance with the tidal cycle and intertidal morphology. Each pixel value can be extracted from these mean images and analysed over the course of several days, giving a fluctuating time series of pixel intensity, the gradient of which gives a series of pulses representing transitions between wet and dry at each location. A tidal elevation record collected from a gauge at the Island is used to generate a similar series of pulses for each elevation above chart datum. A matching algorithm compares these pulse sequences at each tide level and determines a bed elevation value for each pixel location. Values derived have a maximum error of 1 m when compared to a LiDAR survey of the area during the same time period. Refinements of this technique could form the basis of a long-term automated monitoring system for the morphology of intertidal coastal areas allowing varying scales of sedimentary features to be tracked. This may allow the optimisation of maintenance dredging and quantify the effects of beach nourishment and capital dredging along a shoreline.

Can salt marshes survive sea level rise ?

NASA Astrophysics Data System (ADS)

Tambroni, N.; Seminara, G.

2008-12-01

Stability of salt marshes is a very delicate issue depending on the subtle interplay among hydrodynamics, morphodynamics and ecology. In fact, the elevation of the marsh platform depends essentially on three effects: i) the production of soil associated with sediments resuspended by tidal currents and wind waves in the adjacent tidal flats, advected to the marsh and settling therein; ii) production of organic sediments by the salt marsh vegetation; iii) soil 'loss' driven by sea level rise and subsidence. In order to gain insight into the mechanics of the process, we consider a schematic configuration consisting of a salt marsh located at the landward end of a tidal channel connected at the upstream end with a tidal sea, under different scenarios of sea level rise. We extend the simple 1D model for the morphodynamic evolution of a tidal channel formulated by Lanzoni and Seminara (2002, Journal of Geophysical Research-Oceans, 107, C1) allowing for sediment resuspension in the channel and vegetation growth in the marsh using the depth dependent model of biomass productivity of Spartina proposed by Morris et al. (2002, Ecology, 83, pp. 2869 - 2877). We first focus on the case of a tide dominated salt marsh neglecting wind driven sediment resuspension in the shoal. Results show that the production of biomass plays a crucial role on salt marsh stability and, provided productivity is high enough, it may turn out to be sufficient to counteract the effects of sea level rise even in the absence of significant supply of mineral sediments. The additional effect of wind resuspension is then introduced. Note that the wind action is twofold: on one hand, it generates wind waves the amplitude of which is strongly dependent on shoal depth and wind fetch; on the other hand, it generates currents driven by the surface setup induced by the shear stress acting on the free surface. Here, each contribution is analysed separately. Results show that the values of bottom stress induced by wind setup are small compared with those associated with wind waves. However, the permanence of wind currents makes them as significant as the oscillating tidal currents in determining the direction and the intensity of the residual sediment flux. Marshes are typically characterised by a variety of vegetation species competing for habitat space within the intertidal zone: we analyze this feature by considering the case of two different species. Preliminary results show that the presence of a species characterised by a narrower habitat range, lower optimum elevation and biomass productivity, has a positive feedback on the growth of the other species. Moreover, the presence of an invader raises marsh elevation above the value reached in the presence of just one species. Finally, we investigate the effect of a reduction of the amount of sediments supplied from the sea.

Do Large Carnivores and Mesocarnivores Have Redundant Impacts on Intertidal Prey?

PubMed Central

Clinchy, Michael; Zanette, Liana Y.

2017-01-01

The presence of large carnivores can affect lower trophic levels by suppressing mesocarnivores and reducing their impacts on prey. The mesopredator release hypothesis therefore predicts prey abundance will be higher where large carnivores are present, but this prediction assumes limited dietary overlap between large and mesocarnivores. Where dietary overlap is high, e.g., among omnivorous carnivore species, or where prey are relatively easily accessible, the potential exists for large and mesocarnivores to have redundant impacts on prey, though this possibility has not been explored. The intertidal community represents a potentially important but poorly studied resource for coastal carnivore populations, and one for which dietary overlap between carnivores may be high. To evaluate usage of the intertidal community by coastal carnivores and the potential for redundancy between large and mesocarnivores, we surveyed (i) intertidal prey abundance (crabs and fish) and (ii) the abundance and activity of large carnivores (predominantly black bears) and mesocarnivores (raccoons and mink) in an area with an intact carnivore community in coastal British Columbia, Canada. Overall carnivore activity was strongly related to intertidal prey availability. Notably, this relationship was not contingent on carnivore species identity, suggestive of redundancy–high intertidal prey availability was associated with either greater large carnivore activity or greater mesocarnivore activity. We then compared intertidal prey abundances in this intact system, in which bears dominate, with those in a nearby system where bears and other large carnivores have been extirpated, and raccoons are the primary intertidal predator. We found significant similarities in intertidal species abundances, providing additional evidence for redundancy between large (bear) and mesocarnivore (raccoon) impacts on intertidal prey. Taken together, our results indicate that intertidal prey shape habitat use and competition among coastal carnivores, and raise the interesting possibility of redundancy between mesocarnivores and large carnivores in their role as intertidal top predators. PMID:28085962

Growth studies of Mytilus californianus using satellite surface temperatures and chlorophyll data for coastal Oregon

NASA Astrophysics Data System (ADS)

Price, J.; Lakshmi, V.

2013-12-01

The advancement of remote sensing technology has led to better understanding of the spatial and temporal variation in many physical and biological parameters, such as, temperature, salinity, soil moisture, vegetation cover, and community composition. This research takes a novel approach in understanding the temporal and spatial variability of mussel body growth using remotely sensed surface temperatures and chlorophyll-a concentration. Within marine rocky intertidal ecosystems, temperature and food availability influence species abundance, physiological performance, and distribution of mussel species. Current methods to determine the temperature mussel species experience range from in-situ field observations, temperature loggers, temperature models, and using other temperature variables. However, since the temperature that mussel species experience is different from the air temperature due to physical and biological characteristics (size, color, gaping, etc.), it is difficult to accurately predict the thermal stresses they experience. Methods to determine food availability (chlorophyll-a concentration used as a proxy) for mussel species are mostly done at specific study sites using water sampling. This implies that analysis of temperature and food availability across large spatial scales and long temporal scales is not a trivial task given spatial heterogeneity. However, this is an essential step in determination of the impact of changing climate on vulnerable ecosystems such as the marine rocky intertidal system. The purpose of this study was to investigate the potential of using remotely sensed surface temperatures and chlorophyll-a concentration to better understand the temporal and spatial variability of the body growth of the ecologically and economically important rocky intertidal mussel species, Mytilus californianus. Remotely sensed sea surface temperature (SST), land surface temperature (LST), intertidal surface temperature (IST), chlorophyll-a concentration, and mussel body growth were collected for eight study sites along the coast of Oregon, USA for a 12 year period from 2000 through 2011. Differences in surface temperatures, chlorophyll-a concentration, and mussel body growth were seen across study sites. The northernmost study site, Cape Meares, had the highest average SST and the lowest average chlorophyll-a concentration. Interestingly, it also had high average mussel growth. Whereas, Cape Arago and Cape Blanco, the two southernmost study sites, had the lowest average SST and lowest average mussel growth, but had higher average chlorophyll-a concentrations. Furthermore, some study sites showed that mussel growth was related to temperature and at other study sites chlorophyll-a concentration was related to mussel growth. The strongest relationship between either temperature or chlorophyll-a concentration, was found at Boiler Bay, Oregon. Approximately 81% of the variations in mean size-specific mussel growth was explained by mean annual LST anomalies. This means that at Boiler Bay, cooler LST years resulted in less mussel growth and warmer years resulted in higher mussel growth. Results suggest that SST may influence mussel body growth more than chlorophyll-a concentration.

Remote sensing of intertidal morphological change in Morecambe Bay, U.K., between 1991 and 2007

NASA Astrophysics Data System (ADS)

Mason, D. C.; Scott, T. R.; Dance, S. L.

2010-04-01

Tidal Flats are important examples of extensive areas of natural environment that remain relatively unaffected by man. Monitoring of tidal flats is required for a variety of purposes. Remote sensing has become an established technique for the measurement of topography over tidal flats. A further requirement is to measure topographic changes in order to measure sediment budgets. To date there have been few attempts to make quantitative estimates of morphological change over tidal flat areas. This paper illustrates the use of remote sensing to measure quantitative and qualitative changes in the tidal flats of Morecambe Bay during the relatively long period 1991-2007. An understanding of the patterns of sediment transport within the Bay is of considerable interest for coastal management and defence purposes. Tidal asymmetry is considered to be the dominant cause of morphological change in the Bay, with the higher currents associated with the flood tide being the main agency moulding the channel system. Quantitative changes were measured by comparing a Digital Elevation Model (DEM) of the intertidal zone formed using the waterline technique applied to satellite Synthetic Aperture Radar (SAR) images from 1991-1994, to a second DEM constructed from airborne laser altimetry data acquired in 2005. Qualitative changes were studied using additional SAR images acquired since 2003. A significant movement of sediment from below Mean Sea Level (MSL) to above MSL was detected by comparing the two Digital Elevation Models, though the proportion of this change that could be ascribed to seasonal effects was not clear. Between 1991 and 2004 there was a migration of the Ulverston channel of the river Leven north-east by about 5 km, followed by the development of a straighter channel to the west, leaving the previous channel decoupled from the river. This is thought to be due to independent tidal and fluvial forcing mechanisms acting on the channel. The results demonstrate the effectiveness of remote sensing for measurement of long-term morphological change in tidal flat areas. An alternative use of waterlines as partial bathymetry for assimilation into a morphodynamic model of the coastal zone is also discussed.

Evolution of a foredune and backshore river complex on a high-energy, drift-aligned beach

NASA Astrophysics Data System (ADS)

Heathfield, Derek K.; Walker, Ian J.

2015-11-01

This paper examines the multi-decadal evolution of a foredune and backshore river complex on a wave-dominated, drift-aligned coast at Wickaninnish Bay on southwestern Vancouver Island, British Columbia, Canada. Local shoreline positions are generally prograding seaward as fast as + 1.46 m a- 1 in response to rapid regional tectonic uplift and positive onshore sediment budgets. The northern end of the foredune system has extended rapidly alongshore in response to net northward littoral drift. Despite these net accretional responses, the beach-dune system experiences relatively frequent (return interval 1.53 years) erosive events when total water levels exceed a local erosional threshold elevation of 5.5 m above regional chart datum. Geomorphic recovery of the beach-dune system from erosive events is usually rapid (i.e., within a year) by way of high onshore sand transport and aeolian delivery to the upper beach. This response is complicated locally, however, by the influence of a backshore river that alters spatial-temporal patterns of both intertidal and supratidal erosion and deposition. Historic landscape changes and rates of shoreline positional change are derived from several years of aerial photography (1973, 1996, 2007, 2009, 2012) using the USGS Digital Shoreline Analysis System (DSAS). Significant volumetric changes are also estimated from aerial LiDAR-derived DEMs in 2005, 2009 and 2012, and related morphodynamics are interpreted using a statistically constrained geomorphic change detection method. Results suggest that supratidal bar development, overwash deposition and aeolian deposition on a low-lying supratidal platform, combined with alongshore extension of the foredune complex, is forcing Sandhill Creek to migrate northward in the direction of beach drift. In response, the river actively erodes (- 1.24 m a- 1) a bluff system landward of the channel, which generates substantial sediment volumes (- 0.137 m3 m- 2 a- 1) that feed a large intertidal braided channel and delta system. These local responses provide context for a conceptual model of the evolution of a wave-dominated, drift-aligned beach-foredune system that interacts with a backshore river. This model may provide useful information to local park managers as erosion and sedimentation hazards threaten visitor safety and park infrastructure.

Comparison of two feature selection methods for the separability analysis of intertidal sediments with spectrometric datasets in the German Wadden Sea

NASA Astrophysics Data System (ADS)

Jung, Richard; Ehlers, Manfred

2016-10-01

The spectral features of intertidal sediments are all influenced by the same biophysical properties, such as water, salinity, grain size or vegetation and therefore they are hard to separate by using only multispectral sensors. This could be shown by a previous study of Jung et al. (2015). A more detailed analysis of their characteristic spectral feature has to be carried out to understand the differences and similarities. Spectrometry data (i.e., hyperspectral sensors), for instance, have the opportunity to measure the reflection of the landscape as a continuous spectral pattern for each pixel of an image built from dozen to hundreds of narrow spectral bands. This reveals a high potential to measure unique spectral responses of different ecological conditions (Hennig et al., 2007). In this context, this study uses spectrometric datasets to distinguish between 14 different sediment classes obtained from a study area in the German Wadden Sea. A new feature selection method is proposed (Jeffries-Matusita distance bases feature selection; JMDFS), which uses the Euclidean distance to eliminate the wavelengths with the most similar reflectance values in an iterative process. Subsequent to each iteration, the separation capability is estimated by the Jeffries-Matusita distance (JMD). Two classes can be separated if the JMD is greater than 1.9 and if less than four wavelengths remain, no separation can be assumed. The results of the JMDFS are compared with a state-of-the-art feature selection method called ReliefF. Both methods showed the ability to improve the separation by achieving overall accuracies greater than 82%. The accuracies are 4%-13% better than the results with all wavelengths applied. The number of remaining wavelengths is very diverse and ranges from 14 to 213 of 703. The advantage of JMDFS compared with ReliefF is clearly the processing time. ReliefF needs 30 min for one temporary result. It is necessary to repeat the process several times and to average all temporary results to achieve a final result. In this study 50 iterations were carried out, which makes four days of processing. In contrast, JMDFS needs only 30 min for a final result.

When time affects space: Dispersal ability and extreme weather events determine metacommunity organization in marine sediments.

PubMed

Corte, Guilherme N; Gonçalves-Souza, Thiago; Checon, Helio H; Siegle, Eduardo; Coleman, Ross A; Amaral, A Cecília Z

2018-05-01

Community ecology has traditionally assumed that the distribution of species is mainly influenced by environmental processes. There is, however, growing evidence that environmental (habitat characteristics and biotic interactions) and spatial processes (factors that affect a local assemblage regardless of environmental conditions - typically related to dispersal and movement of species) interactively shape biological assemblages. A metacommunity, which is a set of local assemblages connected by dispersal of individuals, is spatial in nature and can be used as a straightforward approach for investigating the interactive and independent effects of both environmental and spatial processes. Here, we examined (i) how environmental and spatial processes affect the metacommunity organization of marine macroinvertebrates inhabiting the intertidal sediments of a biodiverse coastal ecosystem; (ii) whether the influence of these processes is constant through time or is affected by extreme weather events (storms); and (iii) whether the relative importance of these processes depends on the dispersal abilities of organisms. We found that macrobenthic assemblages are influenced by each of environmental and spatial variables; however, spatial processes exerted a stronger role. We also found that this influence changes through time and is modified by storms. Moreover, we observed that the influence of environmental and spatial processes varies according to the dispersal capabilities of organisms. More effective dispersers (i.e., species with planktonic larvae) are more affected by spatial processes whereas environmental variables had a stronger effect on weaker dispersers (i.e. species with low motility in larval and adult stages). These findings highlight that accounting for spatial processes and differences in species life histories is essential to improve our understanding of species distribution and coexistence patterns in intertidal soft-sediments. Furthermore, it shows that storms modify the structure of coastal assemblages. Given that the influence of spatial and environmental processes is not consistent through time, it is of utmost importance that future studies replicate sampling over different periods so the influence of temporal and stochastic factors on macrobenthic metacommunities can be better understood. Copyright © 2018 Elsevier Ltd. All rights reserved.

Revision of the genus Parasphaerolaimus (Nematoda: Sphaerolaimidae) with description of new species.

PubMed

Zograf, Julia K; Pavlyuk, Olga N; Trebukhova, Yulia A; Tu, Nguyen Dinh

2017-02-15

The family Sphaerolaimidae Filipjev, 1918 includes nematodes that are characterized by the finely striated cuticle, round amphids, broad buccal cavity with longitudinal ribs, and single anterior ovary in females. Parasphaerolaimus species from this family are found in intertidal and subtidal sediments and have also been reported from mangroves and estuaries. Parasphaerolaimus pilosus sp. n. is characterized by the moderately plump body, presence of lateral alae, long cervical setae, small amphids in males, and relatively short spicules. As a result of a comprehensive evaluation of species descriptions, eight species in the genus Parasphaerolaimus are recognized valid, and an identification key to species level is provided.

Comparative study on the fauna composition of intertidal invertebrates between natural and artificial substrata in the northeastern coast of Jeju Island

NASA Astrophysics Data System (ADS)

Cha, Jae-Hoon; Kim, Kwang-Bae; Song, Ji-Na; Kim, In-Soo; Seo, Jeong-Bin; Kwoun, Chul-Hwi

2013-12-01

This study was carried out to learn about differences in the sessile macrobenthic fauna communities between the artificial and natural habitats. There were some differences in terms of species composition and dominant species and community structure between two habitat types. The dominant species include Pollicipes mitella and Granuilittorina exigua in natural rocky intertidal zones; Monodonta labio confusa, Ligia exotica, Tetraclita japonica in the artificial rocky intertidal zones. Among all the species, L. exotica and T. japonica occurred only in the artificial rocky intertidal zone. The results of cluster analysis and nMDS analysis showed a distinct difference in community structure between artificial and natural rocky intertidal zones. The fauna in the natural rocky intertidal zones were similar to each other and the fauna in the artificial rocky intertidal zones were divided depending on the slope of the substratum. In the case of a sloping tetrapod, M. labio confusa and P. mitella were dominant, but at the vertical artificial seawall, Cellana nigrolineata, L. exotica T. japonica were dominant. The analysis of the species presented in natural and artificial rocky intertidal areas showed the exclusive presence of 10 species on natural rocks and 12 species on artificial rocks. The species in the natural rocky intertidal area included mobile gastropods and cnidarians (i.e. rock anemones), and the species in the artificial rocky intertidal area mostly included non-mobile attached animals. The artificial novel structure seems to contribute to increasing the heterogeneity of habitats for marine invertebrate species and an increase the species diversity in rocky coastal areas.

Seasonal changes in the vertical distribution of two types of multicellular magnetotactic prokaryotes in the sediment of Lake Yuehu, China.

PubMed

Liu, Jia; Zhang, Wenyan; Du, Haijian; Leng, Xiaoyun; Li, Jin-Hua; Pan, Hongmiao; Xu, Jianhong; Wu, Long-Fei; Xiao, Tian

2018-04-24

There are two genetically distinct morphological types of multicellular magnetotactic prokaryotes (MMPs) in the intertidal zone of Lake Yuehu (China): ellipsoidal MMPs (eMMPs) and spherical MMPs (sMMPs). We studied the vertical distribution of both types of MMPs in the sediment at Lake Yuehu during 1 year. Both types of MMPs were observed at sediment depths ranging from 1 to 34 cm, depending on the seasons. The eMMPs distributed at depths of 2-34 cm during spring, 1-11 cm during summer, 2-21 cm during autumn and 9-32 cm during winter. The eMMP species Candidatus Magnetananas rongchenensis, with magnetite magnetosomes, dominated at all distribution depths. These results suggested that Ca. M. rongchenensis migrated vertically during four seasons. The vertical profiles of oxidation-reduction potential (ORP) in Lake Yuehu changed seasonally, and these changes coincided with the seasonal distribution of MMPs, suggesting that the ORP affected the vertical distribution of MMPs. In addition, high concentrations of ammonium and silicate were associated with low abundances of MMPs. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

Monitoring the Condition of the Estuaries of the United States: The National Coastal Assessment Experience

EPA Science Inventory

Coastal waters in the United States include estuaries, bays, sounds, coastal wetlands, coral reefs, intertidal zones, mangrove and kelp forests, seagrass meadows, and coastal ocean and upwelling areas (i.e. deep water rising to surface). These coastal areas encompass a wide diver...

Contributions of organic and inorganic matter to sediment ...

EPA Pesticide Factsheets

A mixing model derived from first principles describes the bulk density (BD) of intertidal wetland sediments as a function of loss on ignition (LOI). The model assumes the bulk volume of sediment equates to the sum of self-packing volumes of organic and mineral components or BD = 1/[LOI/k1 + (1-LOI)/k2], where k1 and k2 are the self-packing densities of the pure organic and inorganic components, respectively. The model explained 78% of the variability in total BD when fitted to 5075 measurements drawn from 33 wetlands distributed around the conterminous United States. The values of k1 and k2 were estimated to be 0.085 ± 0.0007 g cm-3 and 1.99 ± 0.028 g cm-3, respectively. Based on the fitted organic density (k1) and constrained by primary production, the model suggests that the maximum steady state accretion arising from the sequestration of refractory organic matter is ≤ 0.3 cm yr-1. Thus, tidal peatlands are unlikely to survive indefinitely a higher rate of sea-level rise in the absence of a significant source of mineral sediment. Application of k2 to a mineral sediment load typical of East and eastern Gulf Coast estuaries gives a vertical accretion rate from inorganic sediment of 0.2 cm yr-1. Total steady state accretion is the sum of the parts and therefore should not be greater than 0.5 cm yr-1 under the assumptions of the model. Accretion rates could deviate from this value depending on variation in plant productivity, root:shoot ratio, suspended sedim

Distribution, diversity and abundance of bacterial laccase-like genes in different particle size fractions of sediments in a subtropical mangrove ecosystem.

PubMed

Luo, Ling; Zhou, Zhi-Chao; Gu, Ji-Dong

2015-10-01

This study investigated the diversity and abundance of bacterial lacasse-like genes in different particle size fractions, namely sand, silt, and clay of sediments in a subtropical mangrove ecosystem. Moreover, the effects of nutrient conditions on bacterial laccase-like communities as well as the correlation between nutrients and, both the abundance and diversity indices of laccase-like bacteria in particle size fractions were also studied. Compared to bulk sediments, Bacteroidetes, Caldithrix, Cyanobacteria and Chloroflexi were dominated in all 3 particle-size fractions of intertidal sediment (IZ), but Actinobacteria and Firmicutes were lost after the fractionation procedures used. The diversity index of IZ fractions decreased in the order of bulk > clay > silt > sand. In fractions of mangrove forest sediment (MG), Verrucomicrobia was found in silt, and both Actinobacteria and Bacteroidetes appeared in clay, but no new species were found in sand. The declining order of diversity index in MG fractions was clay > silt > sand > bulk. Furthermore, the abundance of lacasse-like bacteria varied with different particle-size fractions significantly (p < 0.05), and decreased in the order of sand > clay > silt in both IZ and MG fractions. Additionally, nutrient availability was found to significantly affect the diversity and community structure of laccase-like bacteria (p < 0.05), while the total organic carbon contents were positively related to the abundance of bacterial laccase-like genes in particle size fractions (p < 0.05). Therefore, this study further provides evidence that bacterial laccase plays a vital role in turnover of sediment organic matter and cycling of nutrients.

The capability of estuarine sediments to remove nitrogen: implications for drinking water resource in Yangtze Estuary.

PubMed

Liu, Lin; Wang, Dongqi; Deng, Huanguang; Li, Yangjie; Chang, Siqi; Wu, Zhanlei; Yu, Lin; Hu, Yujie; Yu, Zhongjie; Chen, Zhenlou

2014-09-01

Water in the Yangtze Estuary is fresh most of the year because of the large discharge of Yangtze River. The Qingcaosha Reservoir built on the Changxing Island in the Yangtze Estuary is an estuarine reservoir for drinking water. Denitrification rate in the top 10 cm sediment of the intertidal marshes and bare mudflat of Yangtze Estuarine islands was measured by the acetylene inhibition method. Annual denitrification rate in the top 10 cm of sediment was 23.1 μmol m(-2) h(-1) in marshes (ranged from 7.5 to 42.1 μmol m(-2) h(-1)) and 15.1 μmol m(-2) h(-1) at the mudflat (ranged from 6.6 to 26.5 μmol m(-2) h(-1)). Annual average denitrification rate is higher at mashes than at mudflat, but without a significant difference (p = 0.084, paired t test.). Taking into account the vegetation and water area of the reservoir, a total 1.42 × 10(8) g N could be converted into nitrogen gas (N2) annually by the sediment, which is 97.7 % of the dissolved inorganic nitrogen input through precipitation. Denitrification in reservoir sediment can control the bioavailable nitrogen level of the water body. At the Yangtze estuary, denitrification primarily took place in the top 4 cm of sediment, and there was no significant spatial or temporal variation of denitrification during the year at the marshes and mudflat, which led to no single factor determining the denitrification process but the combined effects of the environmental factors, hydrologic condition, and wetland vegetation.

Inferring tidal wetland stability from channel sediment fluxes: observations and a conceptual model

USGS Publications Warehouse

Ganju, Neil K.; Nidzieko, Nicholas J.; Kirwan, Matthew L.

2013-01-01

Anthropogenic and climatic forces have modified the geomorphology of tidal wetlands over a range of timescales. Changes in land use, sediment supply, river flow, storminess, and sea level alter the layout of tidal channels, intertidal flats, and marsh plains; these elements define wetland complexes. Diagnostically, measurements of net sediment fluxes through tidal channels are high-temporal resolution, spatially integrated quantities that indicate (1) whether a complex is stable over seasonal timescales and (2) what mechanisms are leading to that state. We estimated sediment fluxes through tidal channels draining wetland complexes on the Blackwater and Transquaking Rivers, Maryland, USA. While the Blackwater complex has experienced decades of degradation and been largely converted to open water, the Transquaking complex has persisted as an expansive, vegetated marsh. The measured net export at the Blackwater complex (1.0 kg/s or 0.56 kg/m2/yr over the landward marsh area) was caused by northwesterly winds, which exported water and sediment on the subtidal timescale; tidally forced net fluxes were weak and precluded landward transport of suspended sediment from potential seaward sources. Though wind forcing also exported sediment at the Transquaking complex, strong tidal forcing and proximity to a turbidity maximum led to an import of sediment (0.031 kg/s or 0.70 kg/m2/yr). This resulted in a spatially averaged accretion of 3.9 mm/yr, equaling the regional relative sea level rise. Our results suggest that in areas where seaward sediment supply is dominant, seaward wetlands may be more capable of withstanding sea level rise over the short term than landward wetlands. We propose a conceptual model to determine a complex's tendency toward stability or instability based on sediment source, wetland channel location, and transport mechanisms. Wetlands with a reliable portfolio of sources and transport mechanisms appear better suited to offset natural and anthropogenic loss.

Controls on resilience and stability in a sediment-subsidized salt marsh.

PubMed

Stagg, Camille L; Mendelssohn, Irving A

2011-07-01

Although the concept of self-design is frequently employed in restoration, reestablishment of primary physical drivers does not always result in a restored ecosystem having the desired ecological functions that support system resilience and stability. We investigated the use of a primary environmental driver in coastal salt marshes, sediment availability, as a means of promoting the resilience and stability of submerging deltaic salt marshes, which are rapidly subsiding due to natural and human-induced processes. We conducted a disturbance-recovery experiment across a gradient of sediment slurry addition to assess the roles of sediment elevation and soil physico-chemical characteristics on vegetation resilience and stability in two restored salt marshes of differing age (a 15-year-old site and a 5-year-old site). Salt marshes that received moderate intensities of sediment slurry addition with elevations at the mid to high intertidal zone (2-11 cm above local mean sea level; MSL) were more resilient than natural marshes. The primary regulator of enhanced resilience and stability in the restored marshes was the alleviation of flooding stress observed in the natural, unsubsidized marsh. However, stability reached a sediment addition threshold, at an elevation of 11 cm above MSL, with decreasing stability in marshes above this elevation. Declines in resilience and stability above the sediment addition threshold were principally influenced by relatively dry conditions that resulted from insufficient and infrequent flooding at high elevations. Although the older restored marsh has subsided over time, areas receiving too much sediment still had limited stability 15 years later, emphasizing the importance of applying the appropriate amount of sediment to the marsh. In contrast, treated marshes with elevations 2-11 cm above MSL were still more resilient than the natural marsh 15 years after restoration, illustrating that when performed correctly, sediment slurry addition can be a sustainable restoration technique.

Diagenesis in subrecent marine sediments in the Eastern Scheldt, Southwest Netherlands

NASA Astrophysics Data System (ADS)

Oenema, O.

The diagenesis in fine-grained sediments from a 300 to 400-years-old Dunkirk deposit, exposed on the intertidal flat, was studied at a site in the Eastern Scheldt. A new in situ pore water sampling technique that allowed repeated sampling at exactly the same place was used to monitor the seasonal fluctuations in interstitial water composition. Concentrations of organic carbon (1.5 to 2%), nitrogen (C/N = 19), phosphorus (500 μg·g -1) and manganese (250 μg·g -1) in the subrecent anoxic sediments were low, probably because they had already been depleted during earlier stages of diagenesis. Rates of organic carbon mineralization by sulphate reduction (0.1 Mole·m -2·y -1) and rates of nutrient regeneration were 1 to 2 orders of magnitude lower than in recent fine-grained sediments elsewhere in the Eastern Scheldt. Pore water NH 4+ and ΣPO 4 concentrations were controlled by mineralization, uptake by Zostera noltii and sediment-seawater exchange. During the summer the uptake exceeded the mineralization rate at 0 to 5 cm. Mineralization and diffusional processes dominated the changes in the NH 4+ and ΣPO 4 profiles in the other seasons. Dissolved manganese and iron concentrations showed a typical subsurface maximum at 0 to 3 cm, and low (<5 μMole) concentrations below this depth. Dissolved iron concentrations were probably controlled by the solubility of iron sulphides, and manganese probably by the solubility of Mn, Ca-carbonate.

Mudflat morphodynamics and the impact of sea level rise in South San Francisco Bay

USGS Publications Warehouse

Van der Wegen, Mick; Jaffe, Bruce E.; Foxgrover, Amy C.; Roelvink, Dano

2017-01-01

Estuarine tidal mudflats form unique habitats and maintain valuable ecosystems. Historic measurements of a mudflat in San Fancsico Bay over the past 150 years suggest the development of a rather stable mudflat profile. This raises questions on its origin and governing processes as well as on the mudflats’ fate under scenarios of sea level rise and decreasing sediment supply. We developed a 1D morphodynamic profile model (Delft3D) that is able to reproduce the 2011 measured mudflat profile. The main, schematised, forcings of the model are a constant tidal cycle and constant wave action. The model shows that wave action suspends sediment that is transported landward during flood. A depositional front moves landward until landward bed levels are high enough to carry an equal amount of sediment back during ebb. This implies that, similar to observations, the critical shear stress for erosion is regularly exceeded during the tidal cycle and that modelled equilibrium conditions include high suspended sediment concentrations at the mudflat. Shear stresses are highest during low water, while shear stresses are lower than critical (and highest at the landward end) along the mudflat during high water. Scenarios of sea level rise and decreasing sediment supply drown the mudflat. In addition, the mudflat becomes more prone to channel incision because landward accumulation is hampered. This research suggests that sea level rise is a serious threat to the presence of many estuarine intertidal mudflats, adjacent salt marshes and their associated ecological values.

Quality of Tourist Beaches in Huatulco, SW of Mexico: Multiproxy Studies

NASA Astrophysics Data System (ADS)

Retama, I.; Jonathan, M. P.; Rodriguez-Espinosa, P. F.

2014-12-01

40 beach water and sediment samples were collected from the inter-tidal zones of tourist beaches of Huatulco in the State of Oaxaca, South Western part of Mexico. The samples were collected in an aim to know the concentration pattern of metals (Cu, Cd, Cr, Ni, Pb, Zn, Co, Mn, Fe, As, Hg) in sediments and microplastics. Physico-chemical parameters like temperature, pH, dissolved oxygen, conductivity and total dissolved solids, salinity and redox potential. Collection of samples was done during the peak season in April 2013. Our results from water samples indicate that the physico-chemical conditions of the beach water have been altered due to human activities in large numbers. The bioavailable metal concentrations indicate that enrichment of Pb, Cd, Cr and As and it is also supported by the higher values observed from the calculation of enrichment factor and geoaccumulation index. The higher values in the sediments is either due to natural sources like chemical weathering of rocks and external sources, which points to high tourism, agricultural activities in the region. Identification of micro-plastics was done through SEM photographs, indicating the type of plastic wastes deposited into the beach regions which can indicate the density, durability and the persistence level in the sediments. Eventhough the enrichment of metals and modification of beach water quality is observed, care need to be taken to avoid further damage to the coastal ecosystem. Keywords: Tourism, Beach sediments, Beach water, Micro plastics, Trace metals, Contamination indices, Huatulco, Mexico.

The origin of modern agglutinated foraminiferal assemblages: evidence from a stratified fjord

NASA Astrophysics Data System (ADS)

Murray, John W.; Alve, Elisabeth; Cundy, Andrew

2003-11-01

Loch Etive, a silled 145 m deep fjord on the Scottish west coast, provides an example of modern benthic foraminiferal assemblages at intermediate depths (i.e., below the intertidal zone and above the CCD) consisting almost exclusively of organic-cemented agglutinated forms. Since such faunas from intermediate depths are rare in modern oceans but relatively common in the fossil record, the present study allows new insights into one kind of ancient environment for which there are few modern analogues. The strong dominance of agglutinated forms (both living and in some dead assemblages of foraminifera to the exclusion of calcareous taxa) is attributed to the unusual oceanographic conditions. These include a combination of restricted deep-water renewals and strong influence of freshwater which drains through large areas (relative to the size of the loch) of vegetated land. The result is calm bottom water conditions with commonly occurring oxygen depletion (although not anoxic), brackish water throughout the water column (salinity 28 in the deeper parts), and organic-rich (mostly terrestrially derived) sediments with geochemical properties, which, to a much larger degree than open marine ones, are controlled by local input. This environment supports low abundance and low diversity live assemblages, mainly restricted to the surface 1 cm of sediment. The dead assemblages show similar faunal characteristics, but the calcareous components are, due to carbonate dissolution, even more reduced. One of the calcareous species in Loch Etive is Elphidium albiumbilicatum. Its occurrence is the first record in British waters and it matches the previously suggested southern limit of its distribution. Analysis of a 90 cm long core representing sediments deposited over the past two centuries shows the presence of a calcareous dominated assemblage, including more marine species, with a higher diversity, in the lower part. This suggests that Loch Etive is in the process of going from a marine, to a more terrestrial dominated environment. The relatively high sedimentation rate (0.5 cm per yr), the apparent lack of smearing through bioturbation, and the presence of faunal changes in response to reduced marine influence over the past centuries, shows that Loch Etive has a good potential for performing high-resolution climatic studies.

Burrow characteristics of the mud shrimp Austinogebia edulis, an ecological engineer causing sediment modification of a tidal flat.

PubMed

Das, Shagnika; Tseng, Li-Chun; Wang, Lan; Hwang, Jiang-Shiou

2017-01-01

The mud shrimp Austinogebia edulis, being abundant in the intertidal zone of western Taiwan, constructs deep burrows (>1 m). This study highlights the potential of mud shrimps to modify sediment characteristics of the tidal flat by its burrowing behavior. We studied the structure of the burrow wall, compared the difference in the sediment composition of the burrow and the background sediment, and compared the organic content inside the burrow wall. This study was carried out from September 2015 to November 2016 in three areas of the western coast of Taiwan, namely Shengang, Hanbow, and Wangong. The present study found significant differences between burrow wall and the burrow lumen. The diameter of the burrow wall was double as wide as the inner burrow lumen at the opening and gradually increased to 10 times of the burrow lumen at 30 cm depth. The burrow wall of A. edulis showed low permeability and increased the sheer strength. Statistically, a significant difference was noticed in the comparison between the sediment composition of the burrow wall and the background (p < 0.05, Student's t-test). An accumulation of 3.63 for fine sand (t = -5.22, p < 0.001, fine sand) and 9 for clay (t = -25.01, p < 0.001, clay) was found in the upper burrow wall of A. edulis. This indicated that they somehow chose finer particles to build burrows. This will gradually change the sediment distribution-vertically and horizontally. The burrow wall consisted of a 24 times higher organic matter content than one individual of mud shrimp. The burrow may provide organic material as a potential food source. The mud shrimp thus transforms the sediment characteristics as an ecological engineer, which is expected to have a significant ecological impact on the ecosystem.

Heterogeneous distribution in sediments and dispersal in waters of Alexandrium minutum in a semi-enclosed coastal ecosystem.

PubMed

Klouch, Z K; Caradec, F; Plus, M; Hernández-Fariñas, T; Pineau-Guillou, L; Chapelle, A; Schmitt, S; Quéré, J; Guillou, L; Siano, R

2016-12-01

Within the framework of research aimed at using genetic methods to evaluate harmful species distribution and their impact on coastal ecosystems, a portion of the ITS1rDNA of Alexandrium minutum was amplified by real-time PCR from DNA extracts of superficial (1-3cm) sediments of 30 subtidal and intertidal stations of the Bay of Brest (Brittany, France), during the winters of 2013 and 2015. Cell germinations and rDNA amplifications of A. minutum were obtained for sediments of all sampled stations, demonstrating that the whole bay is currently contaminated by this toxic species. Coherent estimations of ITS1rDNA copy numbers were obtained for the two sampling cruises, supporting the hypothesis of regular accumulation of A. minutum resting stages in the south-eastern, more confined embayments of the study area, where fine-muddy sediments are also more abundant. Higher ITS1rDNA copy numbers were detected in sediments of areas where blooms have been seasonally detected since 2012. This result suggests that specific genetic material estimations in superficial sediments of the bay may be a proxy of the cyst banks of A. minutum. The simulation of particle trajectory analyses by a Lagrangian physical model showed that blooms occurring in the south-eastern part of the bay are disconnected from those of the north-eastern zone. The heterogeneous distribution of A. minutum inferred from both water and sediment suggests the existence of potential barriers for the dispersal of this species in the Bay of Brest and encourages finer analyses at the population level for this species within semi-enclosed coastal ecosystems. Copyright © 2016 Elsevier B.V. All rights reserved.

Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state

PubMed Central

Barber, Donald C.; Callaway, John C.; Chambers, Randy; Hagen, Scott C.; Hopkinson, Charles S.; Johnson, Beverly J.; Megonigal, Patrick; Neubauer, Scott C.; Troxler, Tiffany; Wigand, Cathleen

2016-01-01

Abstract A mixing model derived from first principles describes the bulk density (BD) of intertidal wetland sediments as a function of loss on ignition (LOI). The model assumes that the bulk volume of sediment equates to the sum of self‐packing volumes of organic and mineral components or BD = 1/[LOI/k1 + (1‐LOI)/k2], where k1 and k2 are the self‐packing densities of the pure organic and inorganic components, respectively. The model explained 78% of the variability in total BD when fitted to 5075 measurements drawn from 33 wetlands distributed around the conterminous United States. The values of k1 and k2 were estimated to be 0.085 ± 0.0007 g cm−3 and 1.99 ± 0.028 g cm−3, respectively. Based on the fitted organic density (k1) and constrained by primary production, the model suggests that the maximum steady state accretion arising from the sequestration of refractory organic matter is ≤ 0.3 cm yr−1. Thus, tidal peatlands are unlikely to indefinitely survive a higher rate of sea‐level rise in the absence of a significant source of mineral sediment. Application of k2 to a mineral sediment load typical of East and eastern Gulf Coast estuaries gives a vertical accretion rate from inorganic sediment of 0.2 cm yr−1. Total steady state accretion is the sum of the parts and therefore should not be greater than 0.5 cm yr−1 under the assumptions of the model. Accretion rates could deviate from this value depending on variation in plant productivity, root:shoot ratio, suspended sediment concentration, sediment‐capture efficiency, and episodic events. PMID:27819012

Littorally adaptive? Testing the link between habitat, morphology, and reproduction in the intertidal sculpin subfamily Oligocottinae (Pisces: Cottoidea).

PubMed

Buser, Thaddaeus J; Burns, Michael D; López, J Andrés

2017-01-01

While intertidal habitats are often productive, species-rich environments, they are also harsh and highly dynamic. Organisms that live in these habitats must possess morphological and physiological adaptations that enable them to do so. Intertidal fishes are generally small, often lack scales, and the diverse families represented in intertidal habitats often show convergence into a few general body shapes. However, few studies have quantified the relationship between phenotypes and intertidal living. Likewise, the diversity of reproductive traits and parental care in intertidal fishes has yet to be compared quantitatively with habitat. We examine the relationship of these characters in the sculpin subfamily Oligocottinae using a phylogenetic hypothesis, geometric morphometrics, and phylogenetic comparative methods to provide the first formal test of associations between fish phenotypes and reproductive characters with intertidal habitats. We show that the ability to live in intertidal habitats, particularly in tide pools, is likely a primitive state for Oligocottinae, with a single species that has secondarily come to occupy only subtidal habitats. Contrary to previous hypotheses, maximum size and presence of scales do not show a statistically significant correlation with depth. However, the maximum size for all species is generally small (250 mm or less) and all show a reduction in scales, as would be expected for an intertidal group. Also contrary to previous hypotheses, we show that copulation and associated characters are the ancestral condition in Oligocottinae, with copulation most likely being lost in a single lineage within the genus Artedius . Lastly, we show that body shape appears to be constrained among species with broader depth ranges, but lineages that occupy only a narrow range of intertidal habitats display novel body shapes, and this may be associated with habitat partitioning, particularly as it relates to the degree of wave exposure.

Linking Intertidal and Subtidal Food Webs: Consumer-Mediated Transport of Intertidal Benthic Microalgal Carbon

PubMed Central

Kang, Chang-Keun; Park, Hyun Je; Choy, Eun Jung; Choi, Kwang-Sik; Hwang, Kangseok; Kim, Jong-Bin

2015-01-01

We examined stable carbon and nitrogen isotope ratios for a large variety of consumers in intertidal and subtidal habitats, and their potential primary food sources [i.e., microphytobenthos (MPB), phytoplankton, and Phragmites australis] in a coastal bay system, Yeoja Bay of Korea, to test the hypothesis that the transfer of intertidal MPB-derived organic carbon to the subtidal food web can be mediated by motile consumers. Compared to a narrow δ13C range (−18 to −16‰) of offshore consumers, a broad δ13C range (−18 to −12‰) of both intertidal and subtidal consumers indicated that 13C-enriched sources of organic matter are an important trophic source to coastal consumers. In the intertidal areas, δ13C of most consumers overlapped with or was 13C-enriched relative to MPB. Despite the scarcity of MPB in the subtidal, highly motile consumers in subtidal habitat had nearly identical δ13C range with many intertidal foragers (including crustaceans and fish), overlapping with the range of MPB. In contrast, δ13C values of many sedentary benthic invertebrates in the subtidal areas were similar to those of offshore consumers and more 13C-depleted than motile foragers, indicating high dependence on phytoplankton-derived carbon. The isotopic mixing model calculation confirms that the majority of motile consumers and also some of subtidal sedentary ones depend on intertidal MPB for more than a half of their tissue carbon. Finally, although further quantitative estimates are needed, these results suggest that direct foraging by motile consumers on intertidal areas, and thereby biological transport of MPB-derived organic carbon to the subtidal areas, may provide important trophic connection between intertidal production and the nearshore shallow subtidal food webs. PMID:26448137

Dolomite Formation within Microbial Mats in the Sabkha of Abu Dhabi (UAE) and Associated Microsedimentary Structures

NASA Astrophysics Data System (ADS)

Bontognali, T. R.; Vasconcelos, C.; McKenzie, J. A.

2008-12-01

The link between microbial activity and dolomite formation has been evaluated in the coastal sabkha of Abu Dhabi (UAE). This modern dolomite-forming environment is frequently cited as the type analogue for the interpretation of many ancient evaporitic sequences. The investigation of sabkha sediments along a transect from intertidal to supratidal zones revealed a close association between microbial mats and dolomite. Authigenic dolomite occurs within surface and buried microbial mats, which are comprised of exopolymeric substances (EPS). Dolomite forms as a direct consequence of mineral nucleation and growth within microbially produced EPS. The cation-binding effect of the EPS molecules influences the composition of the precipitate. The early stage of this process is characterized by the complexation of an amorphous Mg-Si precipitate, which promotes dolomite development. Mineral formation within EPS appears to be enhanced by evaporation with consequent supersaturation of the pore waters with respect to dolomite. Partial EPS degradation during diagenesis may also provide an additional source of cations. However, the specific mineral-template property of EPS, rather than an increase in cation concentrations, is the key factor for dolomite formation in the studied area of the sabkha. Indeed, within the modern microbial mat located at the surface, dolomite precipitates from pore waters whose composition is very close to seawater. In the supratidal zone, pore water analysis and stable isotope values did not reveal any linkage between dolomite formation and microbial excretion and/or consumption of metabolites along the sediment profiles. This is in contrast with current models, in which dolomite formation is mainly linked to microbial increase of pH and alkalinity or consumption of dissolved SO4 in pore-waters. The EPS of the microbial mats is characterized by an alveolar microfabric, which can be mineralized during early diagenesis, preserving fossil imprints of the original biofilm. Recognition of this biostructure, combined with the atypical Mg-Si phase, may be used to interpret ancient microbial dolomite throughout the geological record.

Evidence for coseismic subsidence events in a southern California coastal saltmarsh

USGS Publications Warehouse

Leeper, Robert; Rhodes, Brady P.; Kirby, Matthew E.; Scharer, Katherine M.; Carlin, Joseph A.; Hemphill-Haley, Eileen; Avnaim-Katav, Simona; MacDonald, Glen M.; Starratt, Scott W.; Aranda, Angela

2017-01-01

Paleoenvironmental records from a southern California coastal saltmarsh reveal evidence for repeated late Holocene coseismic subsidence events. Field analysis of sediment gouge cores established discrete lithostratigraphic units extend across the wetland. Detailed sediment analyses reveal abrupt changes in lithology, percent total organic matter, grain size, and magnetic susceptibility. Microfossil analyses indicate that predominantly freshwater deposits bury relic intertidal deposits at three distinct depths. Radiocarbon dating indicates that the three burial events occurred in the last 2000 calendar years. Two of the three events are contemporaneous with large-magnitude paleoearthquakes along the Newport-Inglewood/Rose Canyon fault system. From these data, we infer that during large magnitude earthquakes a step-over along the fault zone results in the vertical displacement of an approximately 5-km2 area that is consistent with the footprint of an estuary identified in pre-development maps. These findings provide insight on the evolution of the saltmarsh, coseismic deformation and earthquake recurrence in a wide area of southern California, and sensitive habitat already threatened by eustatic sea level rise.

Seagrass burial by dredged sediments: benthic community alteration, secondary production loss, biotic index reaction and recovery possibility.

PubMed

Tu Do, V; de Montaudouin, Xavier; Blanchet, Hugues; Lavesque, Nicolas

2012-11-01

In 2005, dredging activities in Arcachon Bay (France) led in burying 320,000 m(2) of Zostera noltii intertidal seagrass. Recovery by macrobenthos and seagrass was monitored. Six months after works, seagrass was absent and macrobenthos drastically different from surrounding vegetated stations. Rapidly and due to sediment dispersal, disposal area was divided into a sandflat with a specific benthic community which maintained its difference until the end of the survey (2010), and a mudflat where associated fauna became similar to those in adjacent seagrass. Macrobenthic community needs 3 years to recover while seagrass needs 5 years to recover in the station impacted by mud. The secondary production loss due to works was low. In this naturally carbon enriched system, univariate biotic indices did not perform well to detect seagrass destruction and recovery. Multivariate index MISS gave more relevant conclusions and a simplified version was tested with success, at this local scale. Copyright © 2012 Elsevier Ltd. All rights reserved.

Belowground dynamics in mangrove ecosystems

USGS Publications Warehouse

McKee, Karen L.

2004-01-01

Mangrove ecosystems are tropical/subtropical communities of primarily tree species that grow in the intertidal zone. These tidal communities are important coastal ecosystems that are valued for a variety of ecological and societal goods and services (fig. 1). Mangrove wetlands are important filters of materials moving between the land and sea, trapping sediment, nutrients, and pollutants in runoff from uplands and preventing their direct introduction into sensitive marine ecosystems such as seagrass beds and coral reefs. Mangroves serve as nursery grounds and refuge for a variety of organisms and are consequently vital to the biological productivity of coastal waters. Furthermore, because mangroves are highly resilient to disturbances such as hurricanes, they represent a self-sustaining, protective barrier for human populations living in the coastal zone. Mangrove ecosystems also contribute to shoreline stabilization through consolidation of unstable mineral sediments and peat formation. In order to help conserve mangrove ecoystems, scientists with the United States Geological Survey (USGS) at the National Wetlands Research Center are working to more fully understand the dynamics that impact these vital ecosystems.

Organic matter in a subtropical mangrove-estuary subjected to wastewater discharge: Origin and utilisation by two macrozoobenthic species

NASA Astrophysics Data System (ADS)

Meziane, Tarik; Tsuchiya, Makoto

2002-02-01

Total lipid amounts, fatty acid signature analysis, and C:N measurements were used to investigate the sources of organic matter in an Okinawan estuary (Okukubi, Japan) during the 1999 rainy season. This estuary has a mangrove forest and receives agricultural wastewater. Highest concentrations of total lipids and lowest C:N values were simultaneously found near the pipe where the agricultural water is discharged. Fatty acid profiles in the sediments varied among the stations, indicating differences in the contributing organic sources. Small amounts of lipids and low relative contributions of long-chain fatty acids, markers of vascular plants, were found at stations within and adjacent to the mangrove. These results indicate that the export of organic matter from the mangrove litter to the intertidal flat was limited and spatially restricted. The wastewater seems to induce high amounts of bacteria, macroalgae and benthic diatoms, as indicated by their respective fatty acid markers. The fatty acid profiles of the tissues of two dominant intertidal invertebrates, the crab Uca vocans and the gastropod Terebralia sulcata, indicated that their diet was largely comprised of bacteria. Green macroalgae were important food sources for the gastropods; diatoms and mangrove biomass contributed to the nutrition of the crabs, although their contributions were smaller.

Giant subtidal stromatolites forming in normal salinity waters

USGS Publications Warehouse

Dill, R.F.; Shinn, E.A.; Jones, A.T.; Kelly, K.; Steinen, R.P.

1986-01-01

We report here the discovery of giant lithified subtidal columnar stromatolites (>2 m high) growing in 7-8 m of clear oceanic water in current-swept channels between the Exuma Islands on the eastern Bahama Bank. They grow by trapping ooid and pelletal carbonate sand and synsedimentary precipitation of carbonate cement within a field of giant megaripples. The discovery is important to geologists and biologists because similar organo-sedimentary structures built by a combination of cementation and the trapping of sediment by microbes were the dominant fossil types during the Precambrian. Stromatolites are thought to have been responsible for the production of free oxygen and thus the evolution of animal life1,2. Until the discovery of small lithified subtidal columnar stromatolites in the Bahamas3, the only subtidal marine examples known to be living while undergoing lithification were in the hypersaline waters of Hamelin Pool at Shark Bay, Western Australia4-7. Shark Bay stromatolites range from intertidal to the shallow subtidal with the larger columns reaching 1 m in height. The Shark Bay stromatolites have strongly influenced geological interpretation; by analogy, many ancient stromatolites have been considered to have grown in intertidal and/or hypersaline conditions8, although hypersalinity was not a necessity for growth during the Precambrian because grazing metazoan life had not then evolved. ?? 1986 Nature Publishing Group.

Size Matters: The Contribution of Mega-Infauna to the Food ...

EPA Pesticide Factsheets

Large-bodied, invertebrates are common to infaunal communities of NE Pacific estuaries (e.g., bivalves, polychaetes, burrowing shrimps), but their contribution to the ecological structure, function and ecosystem services of most estuaries has been poorly characterized because they are difficult to sample and quantify. In a study of Yaquina estuary (Oregon) food webs, particular effort was made to quantify intertidal and subtidal mega-infauna using suction-excavated 40-cm diameter corers in addition to conventional sampling of macro-infauna. Additionally, the abundance and biomass of all floral and other faunal guilds (except microbial and mammalian guilds) were directly quantified or estimated from published studies, carbon and nitrogen stable isotopes were measured for abundant species, and inverse analysis was used to generate models of carbon flow within food webs of the lower and upper reaches of Yaquina estuary. Benthic invertebrates dominated the biomass and respiration among faunal guilds in both estuarine reaches, whereas biomass and respiration of birds and fish were two orders-of-magnitude smaller. Mega-infauna, particularly intertidal burrowing shrimps and bivalves, constituted most of the benthic invertebrate biomass, respiration and secondary production in both reaches, although only a small fraction of the total infaunal abundance. Mega-infauna were dominant consumers of phytoplankton, major contributors of carbon to sediment organic matter, a

Carbon stable isotope (δ13C) and elemental (TOC, TN, C/N) geochemistry in salt marsh surface sediments (Western Brittany, France): Adequate proxies for relative sea-level reconstruction?

NASA Astrophysics Data System (ADS)

Goslin, Jerome; Sans-jofre, Pierre; Van Vliet Lanoë, Brigitte; Delacourt, Christophe

2017-04-01

Reconstructing a dense network of precise and reliable records of Holocene relative sea-level (RSL) changes is still a major challenge for the paleo climate scientific community. In some regions, the use of traditional foraminifera-based transfer function is prevented by micro-fauna scarcity (e.g. Stéphan et al., 2014, Goslin et al., 2015), thus fostering the need for alternative proxies to be developed and used. Rather recently, isotopic and elemental geochemistry tools have been shown to form promising alternative proxies for RSL reconstruction (e.g. Wilson et al., 2005, Engelhart et al., 2013, Khan et al., 2015). Questions remain nonetheless open regarding the possibility for such markers to allow (i) distinguishing between freshwater and brackish to marine domains (this condition being needed if RSL index-points are to be derived from sedimentary markers) and (ii) to adequately identify the source of the organic matter preserved in the sediment. Concerns about the preservation of carbon and nitrogen compounds during diagenesis have also arose questioning the reliability of such markers for paleo-environmental reconstruction purposes (Wilson et al., 2005; Lamb et al., 2006). We analyzed stable carbon isotope ratios (δ13C), Total Organic Carbon (TOC), and Total Nitrogen (TN) values within 94 surface sediments sampled across two C-3 plants dominated saltmarshes (Brittany, France). The distributions of δ13C, TOC, TN and C/N values is observed to follow clear and strong elevation-dependent trends. Some slight local variability appears between the studied sites that can be easily explained by the different morphological configuration and functioning of these latter. An indicator is found that allows sediments from below and above the high-tide level to be discriminated. This finding forms an interesting advance in the field as it permits to ensure that samples formed under saline conditions and thus suggests that these can be used as stand-alone proxies for RSL reconstruction. This dataset is then used as a modern referential for Holocene RSL reconstruction. Statistical clustering analyses, conducted on the combined regional dataset allow for the identification of several intertidal elevation-dependent groups, characterized by specific values of δ13C, TOC, and TN. Our study thus confirm that δ13C, TOC, TN can act as direct RSL indicators in the context of C-3 plants dominated salt-marshes. Nonetheless, potential preservation issues are observed for the nitrogen compounds within the ancient sediments that deposited in the upper-tidal domain. This eventually challenges the reliable positioning of these latter on the former tidal frame, and thus introduces some uncertainty in the RSL positions that can be derived from them.

Dispersion in tidally averaged transport equation

USGS Publications Warehouse

Cheng, R.T.; Casulli, V.

1992-01-01

A general governing inter-tidal transport equation for conservative solutes has been derived without invoking the weakly nonlinear approximation. The governing inter-tidal transport equation is a convection-dispersion equation in which the convective velocity is a mean Lagrangian residual current, and the inter-tidal dispersion coefficient is defined by a dispersion patch. When the weakly nonlinear condition is violated, the physical significance of the Stokes' drift, as used in tidal dynamics, becomes questionable. For nonlinear problems, analytical solutions for the mean Lagrangian residual current and for the inter-tidal dispersion coefficient do not exist, they must be determined numerically. A rectangular tidal inlet with a constriction is used in the first example. The solutions of the residual currents and the computed properties of the inter-tidal dispersion coefficient are used to illuminate the mechanisms of the inter-tidal transport processes. Then, the present formulation is tested in a geometrically complex tidal estuary – San Francisco Bay, California. The computed inter-tidal dispersion coefficients are in the range between 5×104 and 5×106 cm2/sec., which are consistent with the values reported in the literature

Community structure of soft sediment pool fishes in Moreton Bay, Australia.

PubMed

Chargulaf, C A; Townsend, K A; Tibbetts, I R

2011-02-01

A survey of soft sediment tide pools was conducted to assess the occupation and assemblage of fishes on three different intertidal shores in Moreton Bay, Australia, between January and December 2009. Tide-pool volume ranged from 0· 30 to 29· 75 l and varied significantly between months and sites. A total of 1364 individuals representing 15 species and nine families of fishes were observed. At Dunwich, fish assemblages were dominated by the sand goby Favonigobius lentiginosus (89%) and whiting, Sillago spp. (10%). At Manly, the gobies Favonigobius exquisitus (37%), Pseudogobius sp. (31%) and the blenny Omobranchus punctatus (19%) dominated the shores while at Godwin Beach, F. lentiginosus (15%), F. exquisitus (45%) and Sillago spp. (25%) were the most abundant species. The mean ±s.e. density of fishes ranged from 0· 29 ± 0· 13 to 5· 04 ± 1· 74 fishes l(-1) and abundance of fish correlated with pool volume. Juveniles (75%) dominated assemblages suggesting that soft sediment pools may act as nurseries. The persistent and recurrent fish assemblages found in soft sediment tide pools in Moreton Bay suggest that these shores are behaving more like a tropical than a temperate climate shore, as there was no significant difference of fish abundances between seasons. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.

Biogeochemical Controls on Biodegradation of MC252 Oil:Sand Aggregates on a Rapidly Eroding Coastal Headland Beach

NASA Astrophysics Data System (ADS)

Pardue, J.; Elango, V.; Urbano, M.; Lemelle, K.

2012-12-01

The research described below was conducted on Fourchon Beach, a coastal headland consisting of nine miles of fairly pristine sandy beaches and dunes, backed by wetlands and tidal channels, located between Belle Pass tidal inlet on the west and Elmer's Island on the east in Lafourche Parish, Louisiana. MC252 oil first arrived in large quantities on Fourchon Beach on or around May 20, 2010. A unique oil form created under these conditions was an aggregate of sand and emulsified oil, typically 0.1-10 cm in diameter, termed small surface residue balls (SSRBs). The work from this project made critical measurements on the factors controlling biodegradability of these SSRB aggregates. SSRB aggregates were sampled across transects perpendicular to the beach from the intertidal to the supratidal. Areas in the supratidal that were sampled initially were set aside for research purposes and not altered by any clean-up activities. Chemical composition of SSRBs was measured including concentrations of n-alkanes, PAHs, hopanes, nutrients (nitrate, nitrite, ammonium and orthophosphate measured on water extracts of SSRBs), and electron acceptor concentrations (O2 microprofiles measured on intact SSRBs and sulfate). Physical characterization of the SSRBs including length and area dimensions, mass, density, porosity, moisture content, and salinity using standard methods. Microbial characterization of SSRBs was also conducted using denaturing gradient gel electrophoresis and sequencing of dominant bands. SSRBs were sampled from various locations across the beach profile deposited by 2 significant tropical events in 2010; Hurricane Alex and TS Bonnie, and one event in 2011, TS Lee. Sampling focused on comparing and contrasting impacts of biogeochemistry on weathering of oil stranded in three beach microenvironments; supratidal surface; subtidal subsurface which is permanently inundated and intertidal subsurface samples which are intermittently inundated. The three types of oil are dramatically different in appearance and have a distinctive chemical signature indicative of different rates of weathering. Supratidal surface samples were depleted in n-alkanes and lower-molecular weight PAHs. Geochemically, aggregates located in these environments had low salinities (1.3-1.5 ppt), O2 at near saturation throughout the aggregates and nutrient concentrations (N and P) significantly lower than SSRBs deposited in the intertidal and subtidal. Intertidal and subtidal subsurface oil samples were characterized by elevated nutrient concentrations and salinities consistent with regular seawater inundation. Complete inundation leads to O2 consumption in the aggregates after several days. Despite the presence of elevated nutrients, PAHs and n-alkanes were comparatively unweathered in the subtidal subsurface samples consistent with O2 limitations. Sequences of known PAH degraders were isolated from the supratidal and intertidal aggregates. The results to be presented support the hypothesis that SSRBs deposited at different locations on the beach have different biogeochemical characteristics . These characteristics are due, in part, to their location on the landscape.

The role of seasonal sediment storage in tidal channels on a mesotidal delta

NASA Astrophysics Data System (ADS)

Hale, R. P.; Wilson, C.; Bomer, J.; Goodbred, S. L., Jr.; Bain, R. L.

2017-12-01

The Sundarbans National Forest (SNF), located on the modern topset of the Ganges-Brahmaputra-Meghna (GBM) Delta, is the world's largest mangrove stand ( 10,000 km2), and provides a wide range of cultural, environmental, and economic benefits to the nation of Bangladesh. At present, sediment accretion in the SNF occurs at a rate comparable to that of the locally accelerated sea-level rise ( 1.1 cm/yr), despite substantial modification of the regional hydrodynamics via the construction of channel embankments to prevent inundation of agricultural areas. Approximately 50% of the sediment deposited in the SNF each year is recently delivered (<6 mos) from the GBM. As such, reducing sediment supply by an estimated 60-80% as a result of sediment and water diversions associated with India's National River Linking Project raises serious concerns over the SNF's continued sustainability. Here, we examine: 1) the capacity for short-term sediment storage within tidal channels of varying dimensions, and 2) the hydrodynamic conditions responsible for resuspending this material and delivering it to the mangrove platform. We compare textural and radiochemical characteristics from short cores (<50 cm) collected along the intertidal channel banks, with those from the mangrove platform, to assess seasonal storage of GBM sediment within tidal channels, and the timeframe of its delivery to the SNF platform. We also present instrument data from multiple locations within a confined basin of the SNF, using an upward-looking acoustic Doppler current profiler, pressure sensors, and optical backscatter sensors, to document how transport conditions vary with distance away from the primary tidal inlet, and across the platform. This collection of physical and instrumental observations is then compared to an existing dataset of platform inundation hydroperiods and deposition rates, allowing us to address the threat of a reduced sediment supply to this region, as well as the capacity for this system to self-supply sediment to the platform.

Chemoautotrophic carbon fixation rates and active bacterial communities in intertidal marine sediments.

PubMed

Boschker, Henricus T S; Vasquez-Cardenas, Diana; Bolhuis, Henk; Moerdijk-Poortvliet, Tanja W C; Moodley, Leon

2014-01-01

Chemoautotrophy has been little studied in typical coastal marine sediments, but may be an important component of carbon recycling as intense anaerobic mineralization processes in these sediments lead to accumulation of high amounts of reduced compounds, such as sulfides and ammonium. We studied chemoautotrophy by measuring dark-fixation of 13C-bicarbonate into phospholipid derived fatty acid (PLFA) biomarkers at two coastal sediment sites with contrasting sulfur chemistry in the Eastern Scheldt estuary, The Netherlands. At one site where free sulfide accumulated in the pore water right to the top of the sediment, PLFA labeling was restricted to compounds typically found in sulfur and ammonium oxidizing bacteria. At the other site, with no detectable free sulfide in the pore water, a very different PLFA labeling pattern was found with high amounts of label in branched i- and a-PLFA besides the typical compounds for sulfur and ammonium oxidizing bacteria. This suggests that other types of chemoautotrophic bacteria were also active, most likely Deltaproteobacteria related to sulfate reducers. Maximum rates of chemoautotrophy were detected in first 1 to 2 centimeters of both sediments and chemosynthetic biomass production was high ranging from 3 to 36 mmol C m(-2) d(-1). Average dark carbon fixation to sediment oxygen uptake ratios were 0.22±0.07 mol C (mol O2)(-1), which is in the range of the maximum growth yields reported for sulfur oxidizing bacteria indicating highly efficient growth. Chemoautotrophic biomass production was similar to carbon mineralization rates in the top of the free sulfide site, suggesting that chemoautotrophic bacteria could play a crucial role in the microbial food web and labeling in eukaryotic poly-unsaturated PLFA was indeed detectable. Our study shows that dark carbon fixation by chemoautotrophic bacteria is a major process in the carbon cycle of coastal sediments, and should therefore receive more attention in future studies on sediment biogeochemistry and microbial ecology.

Sustainable Seas Student Intertidal Monitoring Project at Duxbury Reef in Bolinas, CA

NASA Astrophysics Data System (ADS)

Soave, K.; Dean, A.; Yang, G.; Solli, E.; Dattels, C.; Wallace, K.; Boesel, A.; Steiger, C.; Buie, A.

2010-12-01

The Sustainable Seas Student Monitoring Project at the Branson School in Ross, CA has monitored Duxbury Reef in Bolinas, CA since 1999, in cooperation with the Farallones Marine Sanctuary Association and the Gulf of Farallones National Marine Sanctuary. Goals of the project include: 1) To monitor the rocky intertidal habitat and develop a baseline database of invertebrates and algal density and abundance; 2) To contribute to the conservation of the rocky intertidal habitat through education of students and visitors about intertidal species and the requirements for maintaining a healthy, diverse intertidal ecosystem; 3) To increase stewardship in the Gulf of the Farallones National Marine Sanctuary; and 4) To contribute abundance and population data on key algae and invertebrate species to the national database, LiMPETS (Long Term Monitoring Program & Experiential Training for Students). Student volunteers complete an intensive training course on the natural history of intertidal invertebrates and algae, identification of key species, rocky intertidal monitoring techniques, and history of the sanctuary. Students identify and count key invertebrate and algae species along two permanent transects (A and B) and using randomly determined points within a permanent 100 m2 area, three times per year (fall, winter, and late spring). Using the data collected since 2004, we will compare population densities, seasonal abundance and long-term population trends of key algal and invertebrate species, including Tegula funebralis. Future analyses and investigations will include intertidal abiotic factors (including water temperature and human foot-traffic) to enhance insights into the workings of the Duxbury Reef ecosystem, in particular, the high intertidal zone which experiences the greatest amount of human impacts.

Enhanced biofilm formation and melanin synthesis by the oyster settlement-promoting Shewanella colwelliana is related to hydrophobic surface and simulated intertidal environment.

PubMed

Mitra, Sayani; Gachhui, Ratan; Mukherjee, Joydeep

2015-01-01

A direct relationship between biofilm formation and melanogenesis in Shewanella colwelliana with increased oyster recruitment is already established. Previously, S. colwelliana was grown in a newly patented biofilm-cultivation device, the conico-cylindrical flask (CCF), offering interchangeable hydrophobic/hydrophilic surfaces. Melanization was enhanced when S. colwelliana was cultivated in a hydrophobic vessel compared with a hydrophilic vessel. In the present study, melanogenesis in the CCF was positively correlated with increased architectural parameters of the biofilm (mean thickness and biovolume obtained by confocal laser scanning microscopy) and melanin gene (melA) expression observed by densitometry. Niche intertidal conditions were mimicked in a process operated in an ultra-low-speed rotating disk bioreactor, which demonstrated enhanced biofilm formation, melanogenesis, exopolysaccharide synthesis and melA gene expression compared with a process where 12-h periodic immersion and emersion was prevented. The wettability properties of the settling plane as well as intermittent wetting and drying, which influenced biofilm formation and melA expression, may affect oyster settlement in nature.

Flood regime as a driver of the distribution of mangrove and salt marsh species in a subtropical estuary

NASA Astrophysics Data System (ADS)

Spier, Daphne; Gerum, Humberto L. N.; Noernberg, Maurício A.; Lana, Paulo C.

2016-09-01

Tidal patterns of the subtropical Paranaguá Estuarine Complex, in southern Brazil, are strongly affected by episodic cold fronts and by the coastal geometry and bottom topography, resulting in high temporal variability and marked gradients in flood regime. We delimit tolerance ranges of submersion and exposure for representative plant and animal species from local mangroves and salt marshes, through a quantitative analysis of flooding patterns in three estuarine sectors. Our results are consistent with flood regime being the leading factor on how species are distributed over the intertidal flats of the PEC. Subleading factors might be related to salinity, sediment composition and nutrient flow.

Littorally adaptive? Testing the link between habitat, morphology, and reproduction in the intertidal sculpin subfamily Oligocottinae (Pisces: Cottoidea)

PubMed Central

Burns, Michael D.; López, J. Andrés

2017-01-01

While intertidal habitats are often productive, species-rich environments, they are also harsh and highly dynamic. Organisms that live in these habitats must possess morphological and physiological adaptations that enable them to do so. Intertidal fishes are generally small, often lack scales, and the diverse families represented in intertidal habitats often show convergence into a few general body shapes. However, few studies have quantified the relationship between phenotypes and intertidal living. Likewise, the diversity of reproductive traits and parental care in intertidal fishes has yet to be compared quantitatively with habitat. We examine the relationship of these characters in the sculpin subfamily Oligocottinae using a phylogenetic hypothesis, geometric morphometrics, and phylogenetic comparative methods to provide the first formal test of associations between fish phenotypes and reproductive characters with intertidal habitats. We show that the ability to live in intertidal habitats, particularly in tide pools, is likely a primitive state for Oligocottinae, with a single species that has secondarily come to occupy only subtidal habitats. Contrary to previous hypotheses, maximum size and presence of scales do not show a statistically significant correlation with depth. However, the maximum size for all species is generally small (250 mm or less) and all show a reduction in scales, as would be expected for an intertidal group. Also contrary to previous hypotheses, we show that copulation and associated characters are the ancestral condition in Oligocottinae, with copulation most likely being lost in a single lineage within the genus Artedius. Lastly, we show that body shape appears to be constrained among species with broader depth ranges, but lineages that occupy only a narrow range of intertidal habitats display novel body shapes, and this may be associated with habitat partitioning, particularly as it relates to the degree of wave exposure. PMID:28828246

Sustainable Seas Student Intertidal Monitoring Project at Duxbury Reef in Bolinas, CA

NASA Astrophysics Data System (ADS)

Broad, C.; Soave, K.; Ericson, W.; Raabe, B.; Glazer, R.; Ahuatzi, A.; Pereira, M.; Rainsford, A.

2013-12-01

The Sustainable Seas Student Monitoring Project at the Branson School in Ross, CA has monitored Duxbury Reef in Bolinas, CA since 1999, in cooperation with the Farallones Marine Sanctuary Association and the Gulf of Farallones National Marine Sanctuary. Goals of this student-run project include: 1) To monitor the rocky intertidal habitat and develop a baseline database of invertebrates and algal density and abundance; 2) To contribute to the conservation of the rocky intertidal habitat through education of students and visitors about intertidal species and the requirements for maintaining a healthy, diverse intertidal ecosystem; 3) To increase stewardship in the Gulf of the Farallones National Marine Sanctuary; and 4) To contribute abundance and population data on key algae and invertebrate species to the national database, LiMPETS (Long Term Monitoring Program & Experiential Training for Students). Student volunteers complete an intensive training course on the natural history of intertidal invertebrates and algae, identification of key species, rocky intertidal monitoring techniques, and history of the sanctuary. Students identify and count key invertebrate and algae species along two permanent transects and, using randomly determined points, within two permanent 100 m2 areas, three times per year (fall, winter, and late spring). Using the data collected since 2004, we will once again compare population densities, seasonal abundance and long-term population trends of key algal and invertebrate species, including Tegula funebralis, Anthopluera elegantissima and Fucus spp. We will continue to closely monitor algal population densities in within our site in light of the November 2007 San Francisco Bay oil spill that leaked heavy bunker fuel into intertidal habitats around the SF Bay. Future analyses and investigations will include intertidal abiotic factors (including water temperature and human foot-traffic) to enhance insights into the workings of the Duxbury Reef ecosystem, in particular, the high and mid-intertidal zones experiencing the greatest amount of human impacts.

Quantitative assessment of historical coastal landfill contamination using in-situ field portable XRF (FPXRF)

NASA Astrophysics Data System (ADS)

O'Shea, Francis; Spencer, Kate; Brasington, James

2014-05-01

Historically, waste was deposited on low value, easily accessible coastal land (e.g. marsh land). Within England and Wales alone, there are over 5000 historical landfills situated within coastal areas at risk of flooding at a 1 in 100 year return period (Environment Agency, 2012). Historical sites were constructed prior to relevant legislation, and have no basal or side wall engineering, and the waste constituents are mostly unknown. In theory, contaminant concentrations should be reduced through natural attenuation as the leachate plume migrates through surrounding fine-grained inter-tidal sediments before reaching receptor waters. However, erosion resulting from rising sea level and increased storm intensity may re-distribute these sediments and release associated contaminants into the estuarine and coastal environment. The diffuse discharge from these sites has not been quantified and this presents a problem for those landfill managers who are required to complete EIAs. An earlier detailed field campaign at Newlands landfill site, on the Thames Estuary, UK identified a sub-surface (~2m depth) contaminant plume extending c. 20 m from the landfill boundary into surrounding fine-grained saltmarsh sediments. These saltmarsh sediments are risk of being eroded releasing their contaminant load to the Thames Estuary. The aims of this work were to; 1) assess whether this plume is representative of other historical landfills with similar characteristics and 2) to develop a rapid screening methodology using field portable XRF that could be used to identify potential risk of other coastal landfill sites. GIS was used to select landfill sites of similar age, hydrological regime and sedimentary setting in the UK, for comparison. Collection of sediment samples and analysis by ICP OES is expensive and time-consuming, therefore cores were extracted and analysed with a Niton Goldd XRF in-situ. Contaminant data were available immediately and the sampling strategy could be adapted in the field to determine the presence, location and extent of the sub-surface contaminant plume. Although XRF analysis has gained acceptance in the study of in-situ metal contamination (Kalnicky and Singhvi 2001; Martin Peinado et al. 2010) field moisture content and sample heterogeneity can suppress X-ray signals. Therefore, sediment samples were also collected and returned to the laboratory and analysed by ICP OES for comparison. Both wet and dry certified reference materials were also analysed in the laboratory using XRF and ICP OES to observe the impact of moisture content and to produce a correction factor allowing quantitative data to be collected in the field. In-situ raw XRF data identified the location of contamination plumes in the field in agreement with ICP data, although the data were systematically suppressed compared to ICP data, under-estimating the levels of contamination. Applying a correction factor for moisture content provided accurate measurements of concentration. The use of field portable XRF with the application of a moisture content correction factor enables the rapid screening of sediment fronting coastal landfill sites, goes some way towards providing a national baseline dataset and can contribute to the development of risk assessments.

Recolonization of intertidal Zostera marina L. (eelgrass) following experimental shoot removal

EPA Science Inventory

The recovery of eelgrass (Zostera marina) from physical disturbances is understudied and no attention has been given to the likely differences in damage recovery rates between the continuous lower intertidal perennial meadows and higher intertidal eelgrass patches. In the present...

Assessing the potential ecological risk of Co, Cr, Cu, Fe and Zn in the sediments of Hooghly-Matla estuarine system, India.

PubMed

Ghosh, Somdeep; Bakshi, Madhurima; Kumar, Alok; Ramanathan, A L; Biswas, Jayanta Kumar; Bhattacharyya, Subarna; Chaudhuri, Punarbasu; Shaheen, Sabry M; Rinklebe, Jörg

2018-05-09

Hooghly-Matla estuarine system along with the Sundarbans mangroves forms one of the most diverse and vulnerable ecosystems in the world. We have investigated the distribution of Co, Cr, Cu, Fe and Zn along with sediment properties at six locations [Shamshernagar (S1), Kumirmari (S2 and S3), Petuaghat (S4), Tapoban (S5) and Chemaguri (S6)] in the Hooghly estuary and reclaimed islands of the Sundarbans for assessing the degree of contamination and potential ecological risks. Enrichment factor values (0.9-21.6) show enrichment of Co, Cu and Zn in the intertidal sediments considering all sampling locations and depth profiles. Geo-accumulation index values irrespective of sampling locations and depth revealed that Co and Cu are under class II and class III level indicating a moderate contamination of sediments. The pollution load index was higher than unity (1.6-2.1), and Co and Cu were the major contributors to the sediment pollution followed by Zn, Cr and Fe with the minimum values at S1 and the maximum values at S5. The sediments of the Hooghly-Matla estuarine region (S4, S5 and S6) showed considerable ecological risks, when compared with effect range low/effect range median and threshold effect level/probable effect level values. The variation in the distribution of the studied elements may be due to variation in discharge pattern and exposure to industrial effluent and domestic sewage, storm water and agricultural run-off and fluvial dynamics of the region. The study illuminates the necessity for the proper management of vulnerable coastal estuarine ecosystem by stringent pollution control measures along with regular monitoring and checking program.

Tracking the Fate of Explosive-Trinitrotriazine (RDX) in Coastal Marine Ecosystems Using Stable Isotopic Tracer

NASA Astrophysics Data System (ADS)

Ariyarathna, T. S.; Ballentine, M.; Vlahos, P.; Smith, R. W.; Bohlke, J. K.; Tobias, C. R.; Fallis, S.; Groshens, T.; Cooper, C.

2017-12-01

It has been estimated that there are hundreds of explosive-contaminated sites all over the world and managing these contaminated sites is an international challenge. As coastal zones and estuaries are commonly impacted zones, it is vital to understand the fate and transport of munition compounds in these environments. The demand for data on sorption, biodegradation and mineralization of trinitrotriazine (RDX) in coastal ecosystems is the impetus for this study using stable nitrogen isotopes to track its metabolic pathways. Mesocosm experiments representing subtidal vegetated, subtidal unvegetated and intertidal marsh ecocosms were conducted. Steady state concentrations of RDX were maintained in the systems throughout two-week time duration of experiments. Sediment, pore-water and overlying water samples were analyzed for RDX and degradation products. Isotope analysis of the bulk sediments revealed an initial rising inventory of 15N followed by a decay illustrating the role of sediments on sorption and degradation of RDX in anaerobic sediments respectively. Both pore-water and overlying water samples were analyzed for 15N inventories of different inorganic nitrogen pools including ammonium, nitrate, nitrite, nitrous oxide and nitrogen gases. RDX is mineralized to nitrogen gas through a series of intermediates leaving nitrous oxide as the prominent metabolite of RDX. Significant differences in RDX metabolism were observed in the three different ecosystems based on sediment characteristics and redox conditions in the systems. Fine grained organic carbon rich sediments show notably higher mineralization rates of RDX in terms of production of its metabolites. Quantification of degradation and transformation rates leads to mass balances of RDX in the systems. Further analysis of results provides insights for mineralization pathways of RDX into both organic and inorganic nitrogen pools entering the marine nitrogen cycle.

Wave energy and intertidal productivity

PubMed Central

Leigh, Egbert G.; Paine, Robert T.; Quinn, James F.; Suchanek, Thomas H.

1987-01-01

In the northeastern Pacific, intertidal zones of the most wave-beaten shores receive more energy from breaking waves than from the sun. Despite severe mortality from winter storms, communities at some wave-beaten sites produce an extraordinary quantity of dry matter per unit area of shore per year. At wave-beaten sites of Tatoosh Island, WA, sea palms, Postelsia palmaeformis, can produce > 10 kg of dry matter, or 1.5 × 108 J, per m2 in a good year. Extraordinarily productive organisms such as Postelsia are restricted to wave-beaten sites. Intertidal organisms cannot transform wave energy into chemical energy, as photosynthetic plants transform solar energy, nor can intertidal organisms “harness” wave energy. Nonetheless, wave energy enhances the productivity of intertidal organisms. On exposed shores, waves increase the capacity of resident algae to acquire nutrients and use sunlight, augment the competitive ability of productive organisms, and protect intertidal residents by knocking away their enemies or preventing them from feeding. PMID:16593813

Differences in Intertidal Microbial Assemblages on Urban Structures and Natural Rocky Reef

PubMed Central

Tan, Elisa L.-Y.; Mayer-Pinto, Mariana; Johnston, Emma L.; Dafforn, Katherine A.

2015-01-01

Global seascapes are increasingly modified to support high levels of human activity in the coastal zone. Modifications include the addition of defense structures and boating infrastructure, such as seawalls and marinas that replace natural habitats. Artificial structures support different macrofaunal communities to those found on natural rocky shores; however, little is known about differences in microbial community structure or function in urban seascapes. Understanding how artificial constructions in marine environments influence microbial communities is important as these assemblages contribute to many basic ecological processes. In this study, the bacterial communities of intertidal biofilms were compared between artificial structures (seawalls) and natural habitats (rocky shores) within Sydney Harbour. Plots were cleared on each type of habitat at eight locations. After 3 weeks the newly formed biofilm was sampled and the 16S rRNA gene sequenced using the Illumina Miseq platform. To account for differences in orientation and substrate material between seawalls and rocky shores that might have influenced our survey, we also deployed recruitment blocks next to the habitats at all locations for 3 weeks and then sampled and sequenced their microbial communities. Intertidal bacterial community structure sampled from plots differed between seawalls and rocky shores, but when substrate material, age and orientation were kept constant (with recruitment blocks) then bacterial communities were similar in composition and structure among habitats. This suggests that changes in bacterial communities on seawalls are not related to environmental differences between locations, but may be related to other intrinsic factors that differ between the habitats such as orientation, complexity, or predation. This is one of the first comparisons of intertidal microbial communities on natural and artificial surfaces and illustrates substantial ecological differences with potential consequences for biofilm function and the recruitment of macrofauna. PMID:26635747

Discontinuity surfaces in the Lower Cretaceous of the high Andes (Mendoza, Argentina): Trace fossils and environmental implications

NASA Astrophysics Data System (ADS)

Mangano, M. G.; Buatois, L. A.

The paleoecologic and paleoenvironmental significance of trace fossils related to discontinuity surfaces in the Lower Cretaceous marine deposits of the Aconcagua area are analysed here. Carbonate-evaporite shoaling-upward cycles, developed by high organic production in a shallow hypersaline restricted environment, make up the section. Two types of cycles are defined, being mainly distinguished by their subtidal unit. Cycle I begins with a highly dolomitized lower subtidal unit (Facies A), followed upward by an intensely bioturbated upper subtidal unit (Facies B). The nodular packstone facies (B 1) is capped by a discontinuity surface (firmground or hardground) and occasionally overlain by an oystreid bed (Facies C). Cycle II is characterized by a pelletoidal subtidal unit (Facies B 2) with an abnormal salinity impoverished fauna. Both cycles end with intertidal to supratidal evaporite deposits (Facies D and E, respectively). Attention is particularly focused on cycle I due to its ichologic content. The mode of preservation and the distribution of trace fossils in nodular packstone facies are controlled by original substrate consolidation. Thalassinoides paradoxicus (pre-omission suite) represents colonization in a soft bottom, while Thalassinoides suevicus (omission suite pre-lithification) is apparently restricted to firm substrates. When consolidation processes are interrupted early, only an embryonic hard-ground that represents a minor halt in sedimentation was developed. Sometimes, consolidation processes continued leading to an intraformational hardground. Colonization by Trypanites solitarius (omission suite post-lithification) and Exogyra-like oystreids possibly characterizes hard substrate stage. When two discontinuity surfaces follow closely, a post-omission suite may be defined in relation to the lower cemented surface. As trace fossils are so closely related to changes in the degree of bottom lithification, they prove to be very useful as indicators of substrate evolution. The presence of discontinuity surfaces, evidenced by trace fossil association, suggests changes of sedimentary rate and environmental conditions that should be taken into account in future studies seeking to erect depositional models for these Cretaceous deposits.

Complex Effects of Ecosystem Engineer Loss on Benthic Ecosystem Response to Detrital Macroalgae.

PubMed

Rossi, Francesca; Gribsholt, Britta; Gazeau, Frederic; Di Santo, Valentina; Middelburg, Jack J

2013-01-01

Ecosystem engineers change abiotic conditions, community assembly and ecosystem functioning. Consequently, their loss may modify thresholds of ecosystem response to disturbance and undermine ecosystem stability. This study investigates how loss of the bioturbating lugworm Arenicola marina modifies the response to macroalgal detrital enrichment of sediment biogeochemical properties, microphytobenthos and macrofauna assemblages. A field manipulative experiment was done on an intertidal sandflat (Oosterschelde estuary, The Netherlands). Lugworms were deliberately excluded from 1× m sediment plots and different amounts of detrital Ulva (0, 200 or 600 g Wet Weight) were added twice. Sediment biogeochemistry changes were evaluated through benthic respiration, sediment organic carbon content and porewater inorganic carbon as well as detrital macroalgae remaining in the sediment one month after enrichment. Microalgal biomass and macrofauna composition were measured at the same time. Macroalgal carbon mineralization and transfer to the benthic consumers were also investigated during decomposition at low enrichment level (200 g WW). The interaction between lugworm exclusion and detrital enrichment did not modify sediment organic carbon or benthic respiration. Weak but significant changes were instead found for porewater inorganic carbon and microalgal biomass. Lugworm exclusion caused an increase of porewater carbon and a decrease of microalgal biomass, while detrital enrichment drove these values back to values typical of lugworm-dominated sediments. Lugworm exclusion also decreased the amount of macroalgae remaining into the sediment and accelerated detrital carbon mineralization and CO2 release to the water column. Eventually, the interaction between lugworm exclusion and detrital enrichment affected macrofauna abundance and diversity, which collapsed at high level of enrichment only when the lugworms were present. This study reveals that in nature the role of this ecosystem engineer may be variable and sometimes have no or even negative effects on stability, conversely to what it should be expected based on current research knowledge.

Microbial Activity and Depositional System Dynamics: Linking Scales With The Aid of New Technology

NASA Astrophysics Data System (ADS)

Defew, E. C.; Hagerthey, S. E.; Honeywill, C.; Perkins, R. G.; Black, K. S.; Paterson, D. M.

The dynamics of estuarine depositional systems are influenced by sediment-dwelling microphytobenthic assemblages. These assemblages produce extracellular polymeric substances (EPS), which are known to be important in the process of sediment biosta- bilisation. However, these communities are generally studied on very small spatial scales making the prediction of primary productivity and their importance in terms of sediment stability over large areas uncertain. Recent advances in our knowledge of the biostabilisation process have allowed the establishment of links between EPS produc- tion, spatial distribution of algal biomass and their primary productivity over much larger spatial scales. For example, during the multidisciplinary BIOPTIS project, re- mote sensing (RS) was combined with ground-truthing measurements of physical and biological parameters to produce synoptic maps leading to a better understanding of system dynamics and the potential effects of environmental perturbations such as cli- mate change. Recent work using low-temperature scanning electron microscopy (LT- SEM) and in-line laser holography has measured the influence of EPS on the erosional behaviour of sediment flocs and particles and has shown that an increase in the con- centration of EPS determines the nature of the eroded floc material and the critical threshold for sediment erosion. This provides the mechanistic link required between EPS concentration and sediment stability. Whilst it is not yet possible to discern EPS concentration directly by RS studies, we know that EPS concentrations in sediments co-vary with chlorophyll a content, and are closely related to algal productivity. There- fore, RS studies which provide large-scale spatial information of chlorophyll a distri- bution may be used to model the stability and productivity of intertidal depositional systems. This paper introduces the basis of these linkages from the cellular level (in situ chlorophyll fluorescence), the ground-truthing approach (sediment stability, struc- ture, pigment distribution, in situ chlorophyll fluorescence) and investigates the poten- tial of a RS approach in a case study of a Scottish Estuary.

Validating Experimental Bedform Dynamics on Cohesive Sand-Mud Beds in the Dee Estuary

NASA Astrophysics Data System (ADS)

Baas, Jaco H.; Baker, Megan; Hope, Julie; Malarkey, Jonathan; Rocha, Renata

2014-05-01

Recent laboratory experiments and field measurements have shown that small quantities of cohesive clay, and in particular 'sticky' biological polymers, within a sandy substrate dramatically reduce the development rate of sedimentary bedforms, with major implications for sediment transport rate calculations and process interpretations from the sedimentary record. FURTHER INFORMATION Flow and sediment transport predictions from sedimentary structures found in modern estuaries and within estuarine geological systems are impeded by an almost complete lack of process-based knowledge of the behaviour of natural sediments that consist of mixtures of cohesionless sand and biologically-active cohesive mud. Indeed, existing predictive models are largely based on non-organic cohesionless sands, despite the fact that mud, in pure form or mixed with sand, is the most common sediment on Earth and also the most biologically active interface across a range of Earth-surface environments, including rivers and shallow seas. The multidisciplinary COHBED project uses state-of-the-art laboratory and field technologies to measure the erosional properties of mixed cohesive sediment beds and the formation and stability of sedimentary bedforms on these beds, integrating the key physical and biological processes that govern bed evolution. The development of current ripples on cohesive mixed sediment beds was investigated as a function of physical control on bed cohesion versus biological control on bed cohesion. These investigations included laboratory flume experiments in the Hydrodynamics Laboratory (Bangor University) and field experiments in the Dee estuary (at West Kirby near Liverpool). The flume experiments showed that winnowing of fine-grained cohesive sediment, including biological stabilisers, is an important process affecting the development rate, size and shape of the cohesive bedforms. The ripples developed progressively slower as the kaolin clay fraction in the sandy substrate bed was increased. The same result was obtained for xanthan gum, which is a proxy for biological polymers produced by microphytobenthos. Yet, the xanthan gum was several orders more effective in slowing down ripple development than kaolin clay, suggesting that the cohesive forces for biological polymers are much higher than for clay minerals, and that sedimentological process models should refocus on biostabilisation processes. The first results of the field experiments show that the winnowing of fines from developing ripples and the slowing down of current ripple development in mixed cohesive sediment is mimicked on intertidal flats in the Dee estuary. In particular, these field data revealed that current ripples in cohesive sediment are smaller with more two-dimensional crestlines than in non-cohesive sand. The wider implications of these findings will be discussed. COHBED Project Team (NERC): Alan Davies (Bangor University); Daniel Parsons, Leiping Ye (University of Hull); Jeffrey Peakall (University of Leeds); Dougal Lichtman, Louise O'Boyle, Peter Thorne (NOC Liverpool); Sarah Bass, Andrew Manning, Robert Schindler (University of Plymouth); Rebecca Aspden, Emma Defew, Julie Hope, David Paterson (University of St Andrews)

Anaerobic ammonium oxidation mediated by Mn-oxides: from sediment to strain level.

PubMed

Javanaud, Cedric; Michotey, Valerie; Guasco, Sophie; Garcia, Nicole; Anschutz, Pierre; Canton, Mathieu; Bonin, Patricia

2011-11-01

Nitrite and (29)N(2) productions in slurry incubations of anaerobically sediment after (15)NO(3) or (15)NH(4) labelling in the presence of Mn-oxides suggested that anaerobic Mn-oxides mediated nitrification coupled with denitrification in muddy intertidal sediments of Arcachon Bay (SW Atlantic French coast). From this sediment, bacterial strains were isolated and physiologically characterized in terms of Mn-oxides and nitrate reduction as well as potential anaerobic nitrification. One of the isolated strain, identified as Marinobacter daepoensis strain M4AY14, was a denitrifier. Nitrous oxide production by this strain was demonstrated in the absence of nitrate and with Mn-oxides and NH(4) amendment, giving indirect proof of anaerobic nitrate or nitrite production. Anaerobic Mn-oxide-mediated nitrification was confirmed by (29)N(2) production in the presence of (15)NO(3) and (14)NH(4) under denitrifying conditions. Anaerobic nitrification by M4AY14 seemed to occur only in the absence of nitrate, or at nitrate levels lower than that of Mn-oxides. Most of the other isolates were affiliated with the Shewanella genus and were able to use both nitrate and Mn-oxides as electron acceptors. When both electron acceptors were present, whatever their concentrations, nitrate and Mn-oxide reduction co-occurred. These data indicate that bacterial Mn-oxide reduction could be an important process in marine sediments with low oxygen concentrations, and demonstrate for the first time the role of bacteria in anaerobic Mn-mediated nitrification. Copyright © 2011 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

On the role of impermeable groins on barred beach morphodynamics: Example of Matalascañas beach, Spain

NASA Astrophysics Data System (ADS)

Sedrati, Mouncef; Morales González, Juan Antonio

2017-04-01

Several studies on barred beaches in settings with mesotidal to macrotidal regimes have focused on cross-shore and alongshore bar mobility. Whereas the general link between hydrodynamics, sediment transport and the response of the intertidal bars and shoreline evolution has been recognized in the literature, the role of coastal defense structures (Breakwaters, groins, seawalls) on bar-trough systems morphodynamics have received more much less attention and the field-based experimental studies of these environments are rare. The main aim of this paper is to highlight the contrasting behavior of a natural and protected barred beach under several hydrodynamics conditions. This paper presents detailed hydrodynamic and morphological data from a field experiment spanning 10 days undertaken in Matalascañas beach, a mesotidal protected vs natural barred beach in the Southern Spanish coast. This mesotidal beach experienced intense erosion in the recent past and therefore it has been partially protected by groins (protection of sea-front touristic residences). During the fieldwork, an intertidal bars in the protected and non-protected areas highlighted contrasting morphological behaviour. The non-protected barred beach shows a less pronounced bar-trough system than the protected zone. Under low energy conditions (significant wave height < 0,6m), onshore bar migration rate in the protected area was more important than the non-protected area. This migration was associated with an onshore sediment transport, resulting from the erosion of the bar's seaward slope. In the same moment, a clear longshore bar migration was observed in the non-protected zone with the absence of this process in the protected zone. During few energetic tides (Significant wave height > 1m), the protected and non-protected zones show a flattening bars processes. The findings of the present study suggest that cross-shore vs longshore bar mobility may even be mitigated by the presence of the groins, which favour onshore than longshore bar migration.

Multi-scale variability of storm Ophelia 2017: The importance of synchronised environmental variables in coastal impact.

PubMed

Guisado-Pintado, Emilia; Jackson, Derek W T

2018-07-15

Low frequency, high magnitude storm events can dramatically alter coastlines, helping to relocate large volumes of sediments and changing the configuration of landforms. Increases in the number of intense cyclones occurring in the Northern Hemisphere since the 1970s is evident with more northward tracking patterns developing. This brings added potential risk to coastal environments and infrastructure in northwest Europe and therefore understanding how these high-energy storms impact sandy coasts in particular is important for future management. This study highlights the evolution of Storm (formally Hurricane) Ophelia in October 2017 as it passed up and along the western seaboard of Ireland. The largest ever recorded Hurricane to form in the eastern Atlantic, we describe, using a range of environmental measurements and wave modelling, its track and intensity over its duration whilst over Ireland. The impact on a stretch of sandy coast in NW Ireland during Storm Ophelia, when the winds were at their peak, is examined using terrestrial laser scanning surveys pre- and post-storm to describe local changes of intertidal and dune edge dynamics. During maximum wind conditions (>35 knots) waves no >2m were recorded with an oblique to parallel orientation and coincident with medium to low tide (around 0.8m). Therefore, we demonstrate that anticipated widespread coastal erosion and damage may not always unfold as predicted. In fact, around 6000m 3 of net erosion occurred along the 420m stretch of coastline with maximum differences in beach topographic changes of 0.8m. The majority of the sediment redistribution occurred within the intertidal and lower beach zone with some limited dune trimming in the southern section (10% of the total erosion). Asynchronous high water (tide levels), localised offshore winds as well as coastline orientation relative to the storm winds and waves plays a significant role in reducing coastal erosional impact. Copyright © 2018 Elsevier B.V. All rights reserved.

Spatial Variability of Benthic-Pelagic Coupling in an Estuary Ecosystem: Consequences for Microphytobenthos Resuspension Phenomenon

PubMed Central

Ubertini, Martin; Lefebvre, Sébastien; Gangnery, Aline; Grangeré, Karine; Le Gendre, Romain; Orvain, Francis

2012-01-01

The high degree of physical factors in intertidal estuarine ecosystem increases material processing between benthic and pelagic compartments. In these ecosystems, microphytobenthos resuspension is a major phenomenon since its contribution to higher trophic levels can be highly significant. Understanding the sediment and associated microphytobenthos resuspension and its fate in the water column is indispensable for measuring the food available to benthic and pelagic food webs. To identify and hierarchize the physical/biological factors potentially involved in MPB resuspension, the entire intertidal area and surrounding water column of an estuarine ecosystem, the Bay des Veys, was sampled during ebb tide. A wide range of physical parameters (hydrodynamic regime, grain size of the sediment, and suspended matter) and biological parameters (flora and fauna assemblages, chlorophyll) were analyzed to characterize benthic-pelagic coupling at the bay scale. Samples were collected in two contrasted periods, spring and late summer, to assess the impact of forcing variables on benthic-pelagic coupling. A mapping approach using kriging interpolation enabled us to overlay benthic and pelagic maps of physical and biological variables, for both hydrological conditions and trophic indicators. Pelagic Chl a concentration was the best predictor explaining the suspension-feeders spatial distribution. Our results also suggest a perennial spatio-temporal structure of both benthic and pelagic compartments in the ecosystem, at least when the system is not imposed to intense wind, with MPB distribution controlled by both grain size and bathymetry. The benthic component appeared to control the pelagic one via resuspension phenomena at the scale of the bay. Co-inertia analysis showed closer benthic-pelagic coupling between the variables in spring. The higher MPB biomass observed in summer suggests a higher contribution to filter-feeders diets, indicating a higher resuspension effect in summer than in spring, in turn suggesting an important role of macrofauna bioturbation and filter feeding (Cerastoderma edule). PMID:22952910

Cool barnacles: Do common biogenic structures enhance or retard rates of deterioration of intertidal rocks and concrete?

PubMed

Coombes, Martin A; Viles, Heather A; Naylor, Larissa A; La Marca, Emanuela Claudia

2017-02-15

Sedentary and mobile organisms grow profusely on hard substrates within the coastal zone and contribute to the deterioration of coastal engineering structures and the geomorphic evolution of rocky shores by both enhancing and retarding weathering and erosion. There is a lack of quantitative evidence for the direction and magnitude of these effects. This study assesses the influence of globally-abundant intertidal organisms, barnacles, by measuring the response of limestone, granite and marine-grade concrete colonised with varying percentage covers of Chthamalus spp. under simulated, temperate intertidal conditions. Temperature regimes at 5 and 10mm below the surface of each material demonstrated a consistent and statistically significant negative relationship between barnacle abundance and indicators of thermal breakdown. With a 95% cover of barnacles, subsurface peak temperatures were reduced by 1.59°C for limestone, 5.54°C for concrete and 5.97°C for granite in comparison to no barnacle cover. The amplitudes of short-term (15-30min) thermal fluctuations conducive to breakdown via 'fatigue' effects were also buffered by 0.70°C in limestone, 1.50°C in concrete and 1.63°C in granite. Furthermore, concentrations of potentially damaging salt ions were consistently lower under barnacles in limestone and concrete. These results indicate that barnacles do not enhance, but likely reduce rates of mechanical breakdown on rock and concrete by buffering near-surface thermal cycling and reducing salt ion ingress. In these ways, we highlight the potential role of barnacles as agents of bioprotection. These findings support growing international efforts to enhance the ecological value of hard coastal structures by facilitating their colonisation (where appropriate) through design interventions. Copyright © 2016 Elsevier B.V. All rights reserved.

Increased temperature causes different carbon and nitrogen processing patterns in two common intertidal foraminifera (Ammonia tepida and Haynesina germanica)

NASA Astrophysics Data System (ADS)

Wukovits, Julia; Enge, Annekatrin Julie; Wanek, Wolfgang; Watzka, Margarete; Heinz, Petra

2017-06-01

Benthic foraminifera are highly abundant heterotrophic protists in marine sediments, but future environmental changes will challenge the tolerance limits of intertidal species. Metabolic rates and physiological processes in foraminifera are strongly dependent on environmental temperatures. Temperature-related stress could therefore impact foraminiferal food source processing efficiency and might result in altered nutrient fluxes through the intertidal food web. In this study, we performed a laboratory feeding experiment on Ammonia tepida and Haynesina germanica, two dominant foraminiferal species of the German Wadden Sea/Friedrichskoog, to test the effect of temperature on phytodetritus retention. The specimens were fed with 13C and 15N labelled freeze-dried Dunaliella tertiolecta (green algae) at the start of the experiment and were incubated at 20, 25 and 30 °C respectively. Dual labelling was applied to observe potential temperature effects on the relation of phytodetrital carbon and nitrogen retention. Samples were taken over a period of 2 weeks. Foraminiferal cytoplasm was isotopically analysed to investigate differences in carbon and nitrogen uptake derived from the food source. Both species showed a positive response to the provided food source, but carbon uptake rates of A. tepida were 10-fold higher compared to those of H. germanica. Increased temperatures had a far stronger impact on the carbon uptake of H. germanica than on A. tepida. A distinct increase in the levels of phytodetrital-derived nitrogen (compared to more steady carbon levels) could be observed over the course of the experiment in both species. The results suggest that higher temperatures have a significant negative effect on the carbon exploitation of H. germanica. For A. tepida, higher carbon uptake rates and the enhanced tolerance range for higher temperatures could outline an advantage in warmer periods if the main food source consists of chlorophyte phytodetritus. These conditions are likely to impact nutrient fluxes in A. tepida/H. germanica associations.

A diverse assemblage of reef corals thriving in a dynamic intertidal reef setting (Bonaparte Archipelago, Kimberley, Australia).

PubMed

Richards, Zoe T; Garcia, Rodrigo A; Wallace, Carden C; Rosser, Natalie L; Muir, Paul R

2015-01-01

The susceptibility of reef-building corals to climatic anomalies is well documented and a cause of great concern for the future of coral reefs. Reef corals are normally considered to tolerate only a narrow range of climatic conditions with only a small number of species considered heat-tolerant. Occasionally however, corals can be seen thriving in unusually harsh reef settings and these are cause for some optimism about the future of coral reefs. Here we document for the first time a diverse assemblage of 225 species of hard corals occurring in the intertidal zone of the Bonaparte Archipelago, north western Australia. We compare the environmental conditions at our study site (tidal regime, SST and level of turbidity) with those experienced at four other more typical tropical reef locations with similar levels of diversity. Physical extremes in the Bonaparte Archipelago include tidal oscillations of up to 8 m, long subaerial exposure times (>3.5 hrs), prolonged exposure to high SST and fluctuating turbidity levels. We conclude the timing of low tide in the coolest parts of the day ameliorates the severity of subaerial exposure, and the combination of strong currents and a naturally high sediment regime helps to offset light and heat stress. The low level of anthropogenic impact and proximity to the Indo-west Pacific centre of diversity are likely to further promote resistance and resilience in this community. This assemblage provides an indication of what corals may have existed in other nearshore locations in the past prior to widespread coastal development, eutrophication, coral predator and disease outbreaks and coral bleaching events. Our results call for a re-evaluation of what conditions are optimal for coral survival, and the Bonaparte intertidal community presents an ideal model system for exploring how species resilience is conferred in the absence of confounding factors such as pollution.

Tidal and seasonal variations in the quantity and composition of seston in a North American, mid-Atlantic saltmarsh

NASA Astrophysics Data System (ADS)

Huang, S.-C.; Kreeger, D. A.; Newell, R. I. E.

2003-03-01

We determined the concentration of seston, particulate organic matter, and biological components (chlorophyll a, bacteria, and heterotrophic nanoflagellates) for <25 μm size fraction seston over five seasons in Canary Creek saltmarsh, Delaware Bay, USA. This material is the potential food resource for suspension-feeding ribbed mussels, Geukensia demissa, that inhabit the marsh intertidal zone. For eight tidal cycles each season we collected water six times at hourly intervals from mid-flood tide to mid-ebb tide. Although the concentration of seston did not vary seasonally, there were significant seasonal variations (analysis of variance, P<0.05) in seston components, with chlorophyll a concentration being highest in May and bacteria and heterotrophic nanoflagellates most abundant in August. Seston composition also varied within each tidal cycle with a magnitude as great as the seasonal variation. We conclude that ribbed mussels are subject to an unpredictable food supply that varies in composition and concentration on the order of hours and days. In contrast to the pronounced temporal changes, seston characteristics did not differ significantly among sampling locations within the marsh, or between samples collected close to the sediment surface and from the upper water column. Resuspension of sediment particles caused by tidal flow was not evident in tidal creeks and there were no dominant patterns in total seston concentration corresponding to tidal stages (flood tide, high slack water, and ebb tide) over the five sampling months. The abundance of biological components in the seston, including chlorophyll a, bacteria, and heterotrophic nanoflagellates, were significantly greater during high flood tide and high slack water than during ebb tide. The decline of biological components, particularly chlorophyll a in the ebb tide, indicates that this temperate saltmarsh imported organic material produced in the Delaware estuary.

Transient exposure to oxygen or nitrate reveals ecophysiology of fermentative and sulfate‐reducing benthic microbial populations

PubMed Central

Saad, Sainab; Bhatnagar, Srijak; Tegetmeyer, Halina E.; Geelhoed, Jeanine S.; Strous, Marc

2017-01-01

Summary For the anaerobic remineralization of organic matter in marine sediments, sulfate reduction coupled to fermentation plays a key role. Here, we enriched sulfate‐reducing/fermentative communities from intertidal sediments under defined conditions in continuous culture. We transiently exposed the cultures to oxygen or nitrate twice daily and investigated the community response. Chemical measurements, provisional genomes and transcriptomic profiles revealed trophic networks of microbial populations. Sulfate reducers coexisted with facultative nitrate reducers or aerobes enabling the community to adjust to nitrate or oxygen pulses. Exposure to oxygen and nitrate impacted the community structure, but did not suppress fermentation or sulfate reduction as community functions, highlighting their stability under dynamic conditions. The most abundant sulfate reducer in all cultures, related to Desulfotignum balticum, appeared to have coupled both acetate‐ and hydrogen oxidation to sulfate reduction. We describe a novel representative of the widespread uncultured candidate phylum Fermentibacteria (formerly candidate division Hyd24‐12). For this strictly anaerobic, obligate fermentative bacterium, we propose the name ‘USabulitectum silens’ and identify it as a partner of sulfate reducers in marine sediments. Overall, we provide insights into the function of fermentative, as well as sulfate‐reducing microbial communities and their adaptation to a dynamic environment. PMID:28836729

Evidence for contrasting accumulation pattern of cadmium in relation to other elements in Senilia senilis and Tagelus adansoni from the Bijagós archipelago, Guinea-Bissau.

PubMed

Catry, Teresa; Figueira, Paula; Carvalho, Lina; Monteiro, Rui; Coelho, Pedro; Lourenço, Pedro Miguel; Catry, Paulo; Tchantchalam, Quintino; Catry, Inês; Botelho, Maria J; Pereira, Eduarda; Granadeiro, José Pedro; Vale, Carlos

2017-11-01

Shellfish harvesting in intertidal areas is a widespread and economically important activity in many countries across West Africa. However, in some areas, there is virtually no information concerning the levels of contaminants (and other elements related to nutritional aspects) in the harvested species. We collected sediments and several individuals of the West African bloody cockle Senilia senilis and of the razor clam Tagelus adansoni during the dry season of 2015 nearby three islands in the Bijagós archipelago, Guinea-Bissau. Aluminium, Ca, Fe, Mg, As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn were determined in sediments and whole soft tissues of the two bivalves. Sediments showed uniformly low trace element concentrations, pointing to an ecosystem with low levels of trace element contamination. T. adansoni presented higher concentrations of most elements than S. senilis, with the exception of Cd that showed up to 40 times higher values in S. senilis than in T. adansoni from the same sites. Furthermore, Cd concentrations (25±8.7 mg kg -1 , dw) in S. senilis are clearly above the maximum level established for human consumption. Future studies should clarify whether biological factors are the major responsible for this unusual situation.

Seasonal assessment of trace element contamination in intertidal sediments of the meso-macrotidal Hooghly (Ganges) River Estuary with a note on mercury speciation.

PubMed

Mondal, Priyanka; de Alcântara Mendes, Rosivaldo; Jonathan, M P; Biswas, Jayanta Kumar; Murugan, Kadarkarai; Sarkar, Santosh Kumar

2018-02-01

The spatial and seasonal distribution of trace elements (TEs) (n=16) in surficial sediment were examined along the Hooghly River Estuary (~175km), India. A synchronous elevation of majority of TEs concentration (mgkg -1 ) was encountered during monsoon with the following descending order: Al (67070); Fe (31300); Cd (5.73); Cr (71.17); Cu (29.09); Mn (658.74); Ni (35.89). An overall low and homogeneous concentration of total Hg (T Hg =17.85±4.98ngg -1 ) was recorded in which methyl mercury (MeHg) shared minor fraction (8-31%) of the T Hg . Sediment pollution indices, viz. geo-accumulation index (I geo ) and enrichment factor (EF) for Cd (I geo =1.92-3.67; EF=13.83-31.17) and Ba (I geo =0.79-5.03; EF=5.79-108.94) suggested high contamination from anthropogenic sources. From factor analysis it was inferred that TEs primarily originated from lithogenic sources. This study would provide the latest benchmark of TE pollution along with the first record of MeHg in this fluvial system which recommends reliable monitoring to safeguard geochemical health of this stressed environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Heavy metal contamination of coastal lagoon sediments: Fongafale Islet, Funafuti Atoll, Tuvalu.

PubMed

Fujita, Masafumi; Ide, Yoichi; Sato, Daisaku; Kench, Paul S; Kuwahara, Yuji; Yokoki, Hiromune; Kayanne, Hajime

2014-01-01

To evaluate contamination of coastal sediments along Fongafale Islet, Central Pacific, a field survey was conducted in densely populated, sparsely populated, open dumping and undisturbed natural areas. Current measurements in shallow water of the lagoon indicated that contaminants from the densely populated area would only be transported for a small proportion of a tidal cycle. Acid-volatile sulfides were detected in both the intertidal beach and nearshore zones of the densely populated area, whereas these were no detection in the other areas. This observation lends support to argument that the coastal pollution mechanism that during ebb tide, domestic wastewater leaking from poorly constructed sanitary facilities seeps into the coast. The total concentrations of Cr, Mn, Ni, Cu, Zn, Cd and Pb were relatively high in all of the areas except the undisturbed natural area. The indices of contamination factor, pollution load index and geoaccumulation index were indicative of heavy metal pollution in the three areas. The densely populated area has the most significant contamination; domestic wastewater led to significant contamination of coastal sediments with Cr, Zn, Cu, Pb and Cd. The open dumping area is noteworthy with respect to Mn and Ni, which can be derived from disposed batteries. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Late Holocene megathrust earthquakes in south central Chile

NASA Astrophysics Data System (ADS)

Garrett, Ed; Shennan, Ian; Gulliver, Pauline; Woodroffe, Sarah

2013-04-01

A lack of comprehensive understanding of the seismic hazards associated with a subduction zone can lead to inadequate anticipation of earthquake and tsunami magnitudes. Four hundred and fifty years of Chilean historical documents record the effects of numerous great earthquakes; however, with recurrence intervals between the largest megathrust earthquakes approaching 300 years, seismic hazard assessment requires longer chronologies. This research seeks to verify and extend historical records in south central Chile using a relative-sea level approach to palaeoseismology. Our quantitative, diatom-based approaches to relative sea-level reconstruction are successful in reconstructing the magnitude of coseismic deformation during recent, well documented Chilean earthquakes. The few disparities between my estimates and independent data highlight the possibility of shaking-induced sediment consolidation in tidal marshes. Following this encouraging confirmation of the approach, we quantify land-level changes in longer sedimentary records from the centre of the rupture zone of the 1960 Valdivia earthquake. Here, laterally extensive marsh soils abruptly overlain by low intertidal sediments attest to the occurrence of four megathrust earthquakes. Sites preserve evidence of the 1960 and 1575 earthquakes and we constrain the timing of two predecessors to 1270 to 1410 and 1050 to 1200. The sediments and biostratigraphy lack evidence for the historically documented 1737 and 1837 earthquakes.

Residence times of reef-island sediments constrained by post-mortem precipitates

NASA Astrophysics Data System (ADS)

Mann, Thomas; Wizemann, André; Kench, Paul; Jompa, Jamaluddin; Westphal, Hildegard

2017-04-01

The precipitation of carbonate cements is a rapid process in tropical marine environments. Distinct from calcification, the onset of cementation coincides with the termination of 14C uptake within carbonate-sediment forming organisms. Here we show that this relationship presents new opportunities for examining the temporal lag between organism death and deposition in carbonate systems - the prerequisite for reliable depositional chronologies. We dated skeletal constituents collected from discretely stratified reef-island deposits in Indonesia. In each of the strata, internally least cemented segments of the calcifying green alga Halimeda yield the youngest ages. Complementary mesocosm experiments on cementation rates reveal that post-mortem cement growth initiates within months after transport commences. Continuous pore-filling cementation promptly stabilizes the initially fragile Halimeda skeleton. Furthermore, abrasion experiments show that such cementation significantly increases the durability of segments during transport. Implications of these findings are profound in two respects; first, evaluating residence times of skeletal carbonate constituents based on abrasion features is far from being adequate. Second, the absence of cements within sedimentary Halimeda segments signals that post-mortem transport through the intertidal zone occurred quasi-instantaneously. Radiometric ages from such specimens should minimize the temporal lag between organism death and deposition thus making them reliable indicators of sedimentation in supratidal environments.

OCCURRENCE AND ORIENTATION OF PARALICHTHID FLOUNDERS (BOTHIDAE: PARALICHTYS) ON AN INTERTIDAL BEACH

EPA Science Inventory

Middaugh, Douglas P. and Charles L. McKenney, Jr. 2003. Occurrence and Orientation of Flounders (Bothidae: Paralichthys) on an Intertidal Beach. J. North Carol. Acad. Sci. 119(4):157-171. (ERL,GB 1172).

The intertidal movement and burying pattern of paralichthid flounders...

EFFECTS OF EROSION AND MACROALGAE ON INTERTIDAL EELGRASS (ZOSTERA MARINA) IN A NORTHEASTERN PACIFIC ESTUARY (USA)

EPA Science Inventory

Eelgrass (Zostera marina) in open-coast northeastern Pacific estuaries is primarily intertidal, yet little research has been done on the natural factors controlling its upper intertidal growth limits. This two-year study in the Yaquina Estuary (Newport, Oregon, USA) evaluated the...

NATURAL FACTORS CONTROLLING INTERTIDAL EELGRASS: IS T17THHIS AS HIGH AS WE CAN GET?

EPA Science Inventory

Eelgrass (Zostera marina) in many open-coast Pacific Northwest estuaries is primarily intertidal, yet little research has been done on the natural factors which control its upper intertidal growth boundary. In Dec. 2002 a two year study was completed in Yaquina Bay (Newport, OR)...

A GUIDE TO MAPPING INTERTIDAL EELGRASS AND NONVEGETATED HABITATS IN ESTUARIES OF THE PACIFIC NORTHWEST USA

EPA Science Inventory

This document provides technical guidance for planning and implementing the production of aerial photomaps of intertidal vegetative habitats in coastal estuaries of the Pacific Northwest USA (PNW). The focus is on methods of documenting the intertidal distribution of the seagras...

Sustainable Seas Student Intertidal Monitoring Project at Duxbury Reef in Bolinas, CA (Invited)

NASA Astrophysics Data System (ADS)

Soave, K.; Dean, A.; Darakananda, K.; Ball, O.; Butti, C.; Yang, G.; Vetter, M.; Grimaldi, Z.

2009-12-01

Sustainable Seas Student Intertidal Monitoring Project at Duxbury Reef in Bolinas, CA Kathy Soave, Amy Dean, Olivia Ball, Karin Darakananda, Matt Vetter, Grant Yang, Charlotte Butti, Zoe Grimaldi The Sustainable Seas Student Monitoring Project at the Branson School in Ross, CA has monitored Duxbury Reef in Bolinas, CA since 1999, in cooperation with the Farallones Marine Sanctuary Association and the Gulf of Farallones National Marine Sanctuary. Goals of the project include: 1) To monitor the rocky intertidal habitat and develop a baseline database of invertebrates and algal density and abundance; 2) To contribute to the conservation of the rocky intertidal habitat through education of students and visitors about intertidal species and the requirements for maintaining a healthy, diverse intertidal ecosystem; 3) To increase stewardship in the Gulf of the Farallones National Marine Sanctuary; and 4) To contribute abundance and population data on key algae and invertebrate species to the national database, LiMPETS (Long Term Monitoring Program & Experiential Training for Students). Student volunteers complete an intensive training course on the natural history of intertidal invertebrates and algae, identification of key species, rocky intertidal monitoring techniques, and history of the sanctuary. Students identify and count key invertebrate and algae species along two permanent transects (A and B) and using randomly determined points within a permanent 100 m2 area, three times per year (fall, winter, and late spring). Using the data collected since 2004, we will analyze the population densities, seasonal abundance and long-term population trends of key algal and invertebrate species. Future analyses and investigations will include intertidal abiotic factors (including water temperature and human foot-traffic) to enhance insights into the workings of the Duxbury Reef ecosystem, in particular, the high intertidal zone which experiences the greatest amount of human impacts. Kathy Soave The Branson School 39 Fernhill Rd. Ross, CA 94957 (415) 454-3612 x 323 Amy Dean Farallones Marine Sanctuary Association, PO Box 29386 San Francisco, CA 94129, 415-561-6625 x 303 AGU Sponsor, Ines Cifuentes, AGU membership number 10189667

Sustainable Seas Student Intertidal Monitoring Project at Duxbury Reef in Bolinas, CA

NASA Astrophysics Data System (ADS)

Rainsford, A.; Soave, K.; Gerraty, F.; Jung, G.; Quirke-Shattuck, M.; Kudler, J.; Hatfield, J.; Emunah, M.; Dean, A. F.

2014-12-01

The Sustainable Seas Student Monitoring Project at the Branson School in Ross, CA has monitored Duxbury Reef in Bolinas, CA since 1999, in cooperation with the Farallones Marine Sanctuary Association and the Gulf of Farallones National Marine Sanctuary. Goals of this student-run project include: 1) To monitor the rocky intertidal habitat and develop a baseline database of invertebrates and algal density and abundance; 2) To contribute to the conservation of the rocky intertidal habitat through education of students and visitors about intertidal species; 3) To increase stewardship in the Gulf of the Farallones National Marine Sanctuary; and 4) To contribute abundance and population data on key algae and invertebrate species to the national database, LiMPETS (Long Term Monitoring Program & Experiential Training for Students). Each fall student volunteers complete an intensive training course on the natural history of intertidal invertebrates and algae, identification of key species, rocky intertidal monitoring techniques, and history of the sanctuary. Students identify and count key invertebrate and algae species along two permanent transects and, using randomly determined points, within two permanent 200 m2 areas, in fall, winter, and late spring. Using data from the previous years, we will compare population densities, seasonal abundance and long-term population trends of key algal and invertebrate species, including Tegula funebralis, Anthopluera elegantissima, Cladophora sp. and Fucus sp.. Future analyses and investigations will include intertidal abiotic factors (including water temperature, pH and human foot-traffic) to enhance insights into the Duxbury Reef ecosystem, in particular, the high and mid-intertidal zones experiencing the greatest amount of human impacts.

Bottom sediments and nutrients in the tidal Potomac system, Maryland and Virginia

USGS Publications Warehouse

Glenn, Jerry L.

1988-01-01

The characteristics and distributions of near-surface bottom sediments and of nutrients in the sediments provide information on modern sediment and nutrient sources, sedimentation environments, and geochemical reactions in the tidal Potomac system, Maryland and Virginia. This information is fundamental to an improved understanding of sedimentation and eutrophication problems in the tidal Potomac system. The tidal Potomac system consists of 1,230 square kilometers of intertidal to subtidal Potomac mainstem and tributary streambed from the heads-of-tides to Chesapeake Bay. Tidal Potomac sediments are dominantly silt and clay except in local areas. An average sediment sample is about two-thirds silt and clay (fine) particles and one-third sand (coarse) particles. The mean of the median size of all samples is 6.60 phi, or 0.010 millimeters. Sorting generally is poor and the average sediment is skewed toward the fine tail of the size-distribution curve. Mean particle-size measures have large standard deviations. Among geomorphic units, two distinctly different size populations are found; fine (median phi about 9), and poorly sorted (sorting about 3) sediments in the channel and the smooth flat, and coarse (median phi about 2), and well sorted (sorting about 1) sediments in the shoreline flat and the irregular slope. Among mainstem hydrologic divisions, an average sediment from the river and the estuary division is coarser and more variable than an average sediment from the transition division. Substantial concentrations of total carbon, total nitrogen, and total phosphorus, and limited amounts of inorganic carbon, ammonia nitrogen and nitrite plus nitrate nitrogen occur in tidal Potomac sediments. An average tidal Potomac sediment sample weighing 1 kilogram contains about 21,000 milligrams of total carbon, 2,400 milligrams of total nitrogen, 1,200 milligrams of total phosphorus, 600 milligrams of inorganic carbon, 170 milligrams of ammonia nitrogen, and 2 milligrams of nitrite plus nitrate nitrogen. Total carbon, nitrogen, and phosphorus have an average ratio by weight of 18:2:1 and an average ratio by atoms of 94:8:1. Nutrient concentrations and nutrient ratios have large ranges and standard deviations. Nutrient concentrations usually are closely related to particle size; large concentrations are characteristic of fine sediments in the channel and the smooth flat, and small concentrations are typical of coarse sediments in the shoreline flat and the irregular slope. Concentrations typically decrease from the river division to the estuary division. Mainstem and tributaries show no statistically significant difference in mean particle-size measures or mean nutrient concentrations. Tributaries do not contribute large quantities of sediment with diverse texture or nutrient content to the Potomac mainstem. Particle-size measures and nutrient concentrations in the mainstem are significantly related to hydrologic divisions and geomorphic units; that is, particle size and nutrients vary significantly along and across the Potomac mainstem. Lateral variations in particle size and nutrient content are more pronounced and contribute more to significant relations than longitudinal variations contribute. The mean values for the median particle size and for the percentage of sand indicate significant variations among hydrologic divisions for samples from a geomorphic unit, and among geomorphic units, for samples from a hydrologic division. Sediments of channels and smooth flats in the river division commonly are coarser than sediments of channels and smooth flats in the transition and the estuary divisions. Shoreline flats in the estuary division are coarser than shoreline flats in the river division. Shoreline flats and irregular slopes in each hydrologic division generally are significantly coarser than channels and smooth flats. Relations between particle-size measures and geomorphic units show progressively larger cor

Survival and development of horseshoe crab (Limulus polyphemus) embryos and larvae in hypersaline conditions.

PubMed

Ehlinger, Gretchen S; Tankersley, Richard A

2004-04-01

The horseshoe crab Limulus polyphemus spawns in the mid- to upper intertidal zone where females deposit eggs in nests below the sediment surface. Although adult crabs generally inhabit subtidal regions of estuaries with salinities from 5 to 34 ppt, developing embryos and larvae within nests are often exposed to more extreme conditions of salinity and temperature during summer spawning periods. To test whether these conditions have a negative impact on early development and survival, we determined development time, survival, and molt cycle duration for L. polyphemus embryos and larvae raised at 20 combinations of salinity (range: 30-60 ppt) and temperature (range: 25-40 degrees C). Additionally, the effect of hyperosmotic and hypoosmotic shock on the osmolarity of the perivitelline fluid of embryos was determined at salinities between 5 and 90 ppt. The embryos completed their development and molted at salinities below 60 ppt, yet failed to develop at temperatures of 35 degrees C or higher. Larval survival was high at salinities of 10-70 ppt but declined significantly at more extreme salinities (i.e., 5, 80, and 90 ppt). Perivitelline fluid remained nearly isoosmotic over the range of salinities tested. Results indicate that temperature and salinity influence the rate of crab development, but only the extremes of these conditions have an effect on survival.

How Specific Microbial Communities Benefit the Oil Industry: Dynamics of Alcanivorax spp. in Oil-Contaminated Intertidal Beach Sediments Undergoing Bioremediation

NASA Astrophysics Data System (ADS)

Singh, Arvind K.; Sherry, Angela; Gray, Neil D.; Jones, Martin D.; Röling, Wilfred F. M.; Head, Ian M.

The industrial revolution has led to significant increases in the consumption of petroleum hydrocarbons. Concomitant with this increase, hydrocarbon pollution has become a global problem resulting from emissions related to operational use, releases during production, pipeline failures and tanker spills. Importantly, in addition to these anthropogenic sources of hydrocarbon pollution, natural seeps alone account for about 50% of total petroleum hydrocarbon releases in the aquatic environment (National Research Council, 2003). The annual input from natural seeps would form a layer of hydrocarbons 20 molecules thick on the sea surface globally if it remained un-degraded (Prince, 2005). By contrast with natural seeps, many oil spills, e.g. Sea Empress (Milford Haven, UK), Prestige (Galicia, Spain), EXXON Valdez (Prince William Sound, Alaska, USA), released huge amounts of oil (thousands to hundreds of thousand tonnes; Table 24.1) in a locally confined area over a short period of time with a huge acute impact on the marine environment. These incidents have attracted the attention of both the general public and the scientific community due to their great impact on coastal ecosystems. Although many petroleum hydrocarbons are toxic, they are degraded by microbial consortia naturally present in marine ecosystems.

Post-glacial sea-level history for SW Ireland (Bantry Bay) based on offshore evidence

NASA Astrophysics Data System (ADS)

Plets, R. M.; Callard, L.; Cooper, A.; Long, A. J.; Belknap, D. F.; Edwards, R.; Jackson, D.; Kelley, J. T.; Long, D.; Milne, G. A.; Monteys, X.; Quinn, R.

2013-12-01

In recent years, progress in remote sensing techniques has helped to constrain the advance and retreat phases of the British-Irish Ice Sheet during and after the Last Glacial Maximum (LGM), both on- and offshore. However, little evidence has been collected to study the pattern of relative sea-level (RSL) change immediately after ice sheet retreat. Glacio-isostatic adjustment (GIA) models suggest a complex RSL pattern around Ireland, influenced by local and regional isostatic movements. Unfortunately, such models are poorly constrained for periods during which RSL was significantly lower than present, particularly the Late Pleistocene and Early Holocene, owing to the paucity of accurate observational data offshore. This poster presents post-LGM stratigraphic evidence from Bantry Bay (SW Ireland), one of seven areas targeted around the Irish Sea as part of a larger NERC funded project which aims to provide the first field data on the depth and age of the RSL minimum since deglaciation in the Irish Sea Basin. Data examined consists of: multibeam bathymetry and backscatter, pinger sub-bottom and vibrocores (25 sites). Notable features on the multibeam are a bluff line in the outer bay with a maximum height of 10 m in water depths of c. -80 m which forms the western edge of a large sediment lobe. The south-western boundary of this lobe is marked by a series of long (up to 22 km), parallel ridges at depths between -96 m and -131 m, with iceberg scouring evident on the offshore margin. Six seismo-stratigraphic units are interpreted from the pinger data, the most prominent of which can be traced from the inner part of the Bay to the inshore edge of the ridges. This unit sits on an erosional surface, is characterised by a turbid acoustic signature and is identified as alternating sand and clay layers with some traces of organic material and gas. Equal amounts of marine and estuarine foraminifera are present within this unit, whilst the underlying unit has a higher percentage of brackish species and the overlying unit becomes predominantly marine. Based on this evidence, we suggest that the erosional surface represents the transgressive surface, underlying intertidal sediments. Mapping the extent of this surface reveals a maximum depth of -75 m offshore, rising gradually to a depth of -30 m in the inner Bay, a profile remarkably similar to the modelled sea-level curve for the area. The long parallel ridges are interpreted to represent ice-marginal, submarine moraine ridges associated with ice retreat, behind which a glacio-marine delta formed, resulting in the large sediment lobe imaged at the mouth of Bantry Bay. Foraminifera from the proposed transgressive surface have been submitted for radiocarbon dating. Once available, these results will be used for fine-tuning the Earth and ice model parameters in the GIA model. Such adjustments could have important implications for modelled RSL curves around the Irish Sea basin.

DESICCATION AND OTHER FACTORS AFFECTING THE UPPER INTERTIDAL DISTRIBUTION OF EELGRASS IN YAQUINA BAY, OR

EPA Science Inventory

Eelgrass (Zostera marina) in Pacific Northwest is primarily intertidal, yet little research has been done on what factors control its upper intertidal growth boundary. In July 2000 a two year study was initiated in Yaquina Bay (Newport, OR) to evaluate the effects of four factor...

DESICCATION IS A LIMITING FACTOR FOR EELGRASS (ZOSTERA MARINA L.) DISTRIBUTION IN THE INTERTIDAL ZONE OF A NORTHEASTERN P{ACIFIC (USA) ESTUARY

EPA Science Inventory

Intertidal irradiance, temperature, and aerial exposure were measured for two years in intertidal Zostera marina beds located in Yaquina Bay (Newport, OR, USA). These physical data were correlated with plant growth and other metrics measured at intervals during the study. Pho...

DESICCATION INDEX: A MEASURE OF DAMAGE CAUSED BY ADVERSE AERIAL EXPOSURE ON INTERTIDAL EELGRASS (ZOSTERA MARINA) IN AN OREGON (USA) ESTUARY

EPA Science Inventory

Eelgrass (Zostera marina) blade necrosis resulting from intertidal aerial exposure is describe. A desiccation index was developed to quantitatively assess this damage. This index was then used to evaluate the extent of desiccation damage across intertidal bathymetric slopes (st...

Reciprocal subsidies and food web pathways leading to chum salmon fry in a temperate marine-terrestrial ecotone.

PubMed

Romanuk, Tamara N; Levings, Colin D

2010-04-08

Stable isotope analysis was used to determine the relative proportions of terrestrial and marine subsidies of carbon to invertebrates along a tidal gradient (low-intertidal, mid-intertidal, high-intertidal, supralittoral) and to determine the relative importance of terrestrial carbon in food web pathways leading to chum salmon fry Oncorhynchus keta (Walbaum) in Howe Sound, British Columbia. We found a clear gradient in the proportion of terrestrially derived carbon along the tidal gradient ranging from 68% across all invertebrate taxa in the supralittoral to 25% in the high-intertidal, 20% in the mid-intertidal, and 12% in the low-intertidal. Stable isotope values of chum salmon fry indicated carbon contributions from both terrestrial and marine sources, with terrestrially derived carbon ranging from 12.8 to 61.5% in the muscle tissue of chum salmon fry (mean 30%). Our results provide evidence for reciprocal subsidies of marine and terrestrially derived carbon on beaches in the estuary and suggest that the vegetated supralittoral is an important trophic link in supplying terrestrial carbon to nearshore food webs.

Reproducing on Time When Temperature Varies: Shifts in the Timing of Courtship by Fiddler Crabs

PubMed Central

Kerr, Kecia A.; Christy, John H.; Joly-Lopez, Zoé; Luque, Javier; Collin, Rachel; Guichard, Frédéric

2014-01-01

Many species reproduce when conditions are most favorable for the survival of young. Numerous intertidal fish and invertebrates release eggs or larvae during semilunar, large amplitude, nocturnal tides when these early life stages are best able to escape predation by fish that feed near the shore during the day. Remarkably, some species, including the fiddler crabs Uca terpsichores and Uca deichmanni, maintain this timing throughout the year as temperature, and thus the rate of embryonic development, vary. The mechanisms that allow such precision in the timing of the production of young are poorly known. A preliminary study suggested that when temperature decreases, U. terpsichores mate earlier in the tidal amplitude cycle such that larvae are released at the appropriate time. We tested this idea by studying the timing of courtship in U. terpsichores and U. deichmanni as temperature varied annually during two years, at 5 locations that differed in the temperature of the sediment where females incubate their eggs. Uca terpsichores courted earlier at locations where sediment temperature declined seasonally but not where sediment temperature remained elevated throughout the year. In contrast, clear shifts in courtship timing were not observed for U. deichmanni despite variation in sediment temperature. We discuss other mechanisms by which this species may maintain reproductive timing. These two species are likely to be affected differently by changes in the frequency and intensity of cold periods that are expected to accompany climate change. PMID:24832079

Sources and ages of fine-grained sediment to streams using fallout radionuclides in the Midwestern United States

USGS Publications Warehouse

Gellis, Allen; Fuller, Christopher C.; Van Metre, Peter C.

2017-01-01

Fallout radionuclides, 7Be and 210Pbex, sampled in bed sediment for 99 watersheds in the Midwestern region of the United States and in 15 samples of suspended sediment from 3 of these watersheds were used to partition upland from channel sources and to estimate the age or the time since the surface-derived portion of sediment was on the land surface (0–∼1 year). Channel sources dominate: 78 of the 99 bed material sites (79%) have >50% channel-derived sediment, and 9 of the 15 suspended-sediment samples (60%) have >50% channel-derived sediment. 7Be was detected in 82 bed sediment samples and all 15 suspended-sediment samples. The surface-derived portion of 54 of the 80 (68%) streams with detectable 7Be and 210Pbex were ≤ 100 days old and the surface-derived portion of all suspended-sediment samples were ≤ 100 days old, indicating that surface-derived fine-grained sediment moves rapidly though these systems. The concentrations of two hydrophobic pesticides–DDE and bifenthrin–are correlated with the proportion of surface-derived sediment, indicating a link between geomorphic processes and particle-associated contaminants in streams. Urban areas had the highest pesticide concentrations and the largest percentage of surface-derived sediment. Although the percentage of surface-derived sediment is less than channel sources at most of the study sites, the relatively young age of the surface-derived sediment might indicate that management actions to reduce sediment contamination where the land surface is an important source could have noticeable effects.

Long-term change in eelgrass distribution at Bahía San Quintín, Baja California, Mexico, using satellite imagery

USGS Publications Warehouse

Ward, David H.; Morton, Alexandra; Tibbitts, T. Lee; Douglas, David C.; Carrera-Gonzalez, Eduardo

2003-01-01

Seagrasses are critically important components of many marine coastal and estuarine ecosystems, but are declining worldwide. Spatial change in distribution of eelgrass, Zostera marina L., was assessed at Bahía San Quintín, Baja California, Mexico, using a map to map comparison of data interpreted from a 1987 Satellite Pour l'Observation de la Terre multispectral satellite image and a 2000 Landsat Enhanced Thematic Mapping image. Eelgrass comprised 49% and 43% of the areal extent of the bay in 1987 and 2000, respectively. Spatial extent of eelgrass was 13% less (-321 ha) in 2000 than in 1987 with most losses occurring in subtidal areas. Over the 13-yr study period, there was a 34% loss of submerged eelgrass (-457 ha) and a 13% (+136 ha) gain of intertidal eelgrass. Within the two types of intertidal eelgrass, the patchy cover class (<85% cover) expanded (+250 ha) and continuous cover class (≥85% cover) declined (-114 ha). Most eelgrass losses were likely the result of sediment loading and turbidity caused by a single flooding event in winter of 1992-1993. Recent large-scale agricultural development of adjacent uplands may have exacerbated the effects of the flood. Oyster farming was not associated with any detectable losses in eelgrass spatial extent, despite the increase in number of oyster racks from 57 to 484 over the study period.

Habitat risk: Use of intertidal flats by foraging red knots (Calidris canutus rufa), ruddy turnstones, (Arenaria interpres), semipalmated sandpipers (Calidris pusilla), and sanderling (Calidris alba) on Delaware Bay beaches.

PubMed

Burger, Joanna; Niles, Lawrence; Jeitner, Christian; Gochfeld, Michael

2018-05-04

Shorebirds usually forage on intertidal flats that are exposed during low tide, and roost on higher areas when the tidal flats are covered with water. During spring migration on Delaware Bay (New Jersey) shorebirds mainly forage on horseshoe crab (Limulus polyphemus) eggs that are concentrated at the high tide line. However, they also use other habitats for foraging. We examined habitat use of 4 species of shorebirds (with declining populations) at five Delaware Bay beaches to determine their use of the intertidal habitat (2015, 2016). We observed birds in three sections at different distances from the mean high tideline (< 100 m, 101-200 m, and 201-300 m)ne. We examined the presence of red knots (Calidris canutus rufa), ruddy turnstones (Arenaria interpres), semipalmated sandpipers (Calidris pusilla), and sanderling (Calidris alba) as a function of date, tide cycle, section shorebirds foraged from the mean high tide line, and presence of other shorebird species. Understanding how these species use the intertidal flats is important because these habitats are at risk from coastal development, sea level rise, and decreases in intertidal space, including the possible expansion of intertidal oyster culture. Overall, knots were present in the intertidal on 67% of the surveys, turnstones were present on 86% of the surveys, semipalmated sandpipers were present on 77% of the surveys, and sanderling were present on 86% of the surveys. Use of the intertidal flats varied among beaches. Peak and mean numbers of shorebirds/ decreased in each census section, as distance to mean high tideline increased. In general, shorebirds foraged at the waters' edge during high tide, and then moved out onto the intertidal flats. The strongest interspecific associations were between red knots and ruddy turnstones, and the lowest associations were between sanderling and semipalmated sandpipers. Variations in numbers of each species in 2016 were mainly explained by the number of other species, section (distance from the mean high tide line), location (one of 5 beaches), and date for all species (and minutes to low tide for sanderling). These data indicate that these 4 species use intertidal flats as they become available, and that the mean number in each newly exposed census section of the flats may be lower than in the previous one, partly as a result of some birds remaining in each previously-exposed section. We discuss the management and regulatory implications of shorebird use of the intertidal flats, which include protection of high quality intertidal for foraging by shorebirds. Copyright © 2018 Elsevier Inc. All rights reserved.

Response of salt-marsh carbon accumulation to climate change.

PubMed

Kirwan, Matthew L; Mudd, Simon M

2012-09-27

About half of annual marine carbon burial takes place in shallow water ecosystems where geomorphic and ecological stability is driven by interactions between the flow of water, vegetation growth and sediment transport. Although the sensitivity of terrestrial and deep marine carbon pools to climate change has been studied for decades, there is little understanding of how coastal carbon accumulation rates will change and potentially feed back on climate. Here we develop a numerical model of salt marsh evolution, informed by recent measurements of productivity and decomposition, and demonstrate that competition between mineral sediment deposition and organic-matter accumulation determines the net impact of climate change on carbon accumulation in intertidal wetlands. We find that the direct impact of warming on soil carbon accumulation rates is more subtle than the impact of warming-driven sea level rise, although the impact of warming increases with increasing rates of sea level rise. Our simulations suggest that the net impact of climate change will be to increase carbon burial rates in the first half of the twenty-first century, but that carbon-climate feedbacks are likely to diminish over time.

Spatial and temporal distribution of nitrite-dependent anaerobic methane-oxidizing bacteria in an intertidal zone of the East China Sea.

PubMed

Wang, Jiaqi; Shen, Lidong; He, Zhanfei; Hu, Jiajie; Cai, Zhaoyang; Zheng, Ping; Hu, Baolan

2017-11-01

Nitrite-dependent anaerobic methane oxidation (N-DAMO), which couples anaerobic methane oxidation and nitrite reduction, is a recently discovered bioprocess coupling microbial nitrogen and carbon cycles. The discovery of this microbial process challenges the traditional knowledge of global methane sinks and nitrogen losses. In this study, the abundance and activity of N-DAMO bacteria were investigated and their contributions to methane sink and nitrogen loss were estimated in different seasons and different partitions of an intertidal zone of the East China Sea. The results showed that N-DAMO bacteria were extensively and continuously present in the intertidal zone, with the number of cells ranging from 5.5 × 10 4 to 2.8 × 10 5 copy g -1 soil and the potential activity ranging from 0.52 to 5.7 nmol CO 2  g -1 soil day -1 , contributing 5.0-36.6% of nitrite- and sulfate-dependent anaerobic methane oxidation in the intertidal zone. The N-DAMO activity and its contribution to the methane consumption were highest in the spring and in the low intertidal zone. These findings showed that the N-DAMO process is an important methane and nitrogen sink in the intertidal zone and varies with the seasons and the partitions of the intertidal zone.

Impacts of Near-Future Ocean Acidification and Warming on the Shell Mechanical and Geochemical Properties of Gastropods from Intertidal to Subtidal Zones.

PubMed

Leung, Jonathan Y S; Connell, Sean D; Nagelkerken, Ivan; Russell, Bayden D

2017-11-07

Many marine organisms produce calcareous shells as the key structure for defense, but the functionality of shells may be compromised by ocean acidification and warming. Nevertheless, calcifying organisms may adaptively modify their shell properties in response to these impacts. Here, we examined how reduced pH and elevated temperature affect shell mechanical and geochemical properties of common grazing gastropods from intertidal to subtidal zones. Given the greater environmental fluctuations in the intertidal zone, we hypothesized that intertidal gastropods would exhibit more plastic responses in shell properties than subtidal gastropods. Overall, three out of five subtidal gastropods produced softer shells at elevated temperature, while intertidal gastropods maintained their shell hardness at both elevated pCO 2 (i.e., reduced pH) and temperature. Regardless of pH and temperature, degree of crystallization was maintained (except one subtidal gastropod) and carbonate polymorph remained unchanged in all tested species. One intertidal gastropod produced less soluble shells (e.g., higher calcite/aragonite) in response to reduced pH. In contrast, subtidal gastropods produced only aragonite which has higher solubility than calcite. Overall, subtidal gastropods are expected to be more susceptible than intertidal gastropods to shell dissolution and physical damage under future seawater conditions. The increased vulnerability to shell dissolution and predation could have serious repercussions for their survival and ecological contributions in the future subtidal environment.

In situ measurements of erosion shear stress and geotechnical shear strength of the intertidal sediments of the experimental managed realignment scheme at Tollesbury, Essex, UK

NASA Astrophysics Data System (ADS)

Watts, C. W.; Tolhurst, T. J.; Black, K. S.; Whitmore, A. P.

2003-11-01

Managed realignment is one of several 'soft' engineering options which may reduce the costs of coastal defence, provide a more 'natural' response to the problem of rising sea levels and at the same time deliver environmental, specifically nature conservation, benefits. The success of this technique depends on the ability of the soils and sediments within the site to resist the erosive action of waves and tidal currents and allow sediment accretion to occur, at least at a rate equal to mean sea-level rise. Once a critical shear stress, τ0 crt exerted by the moving fluids over the bed, is exceeded erosion will occur. A cohesive strength meter (CSM) and the fall-cone method were used to gather data, in situ on the strength and stability of sediments from an experimental managed realignment site and an adjacent, established saltmarsh in south-east England. Following six years of regular tidal cover, the underlying agricultural soil appeared both very strong (mean surface shear strength, τ f=228 kPa) and highly resistant to erosion ( τ 0 crt=6.23 N m -2). During this period much of the site had been covered by sediment, and saltmarsh plants ( Salicornia europaea) had become established above the mean high water neap tide (MHWN) level. Above MHWN level (tidal cover time <15%) sediments had greater bulk densities and lower water contents which resulted in a moderate shear strength (τ f=11.6 kPa) and resistance to erosion (τ 0 crt=2.45 N m -2) . Below MHWN, where sediment accretion rates were greatest, poor consolidation resulted in very high water contents and low bulk densities. These areas were at the highest potential risk of erosion (τ 0 crt=1.5 N m -2) and had very low shear strengths (τ f=0.33 kPa) . Where sediment exceeded 25 cm depth, gullies formed allowing their banks and adjacent margins to drain faster than the surrounding sediment. This led to a significant increase in bed strength (τ f=10.8 kPa) and stability (τ 0 crt=4.3 N m -2) . These gullies were probably the early stages of the complex creek patterns characteristic of the adjacent, established saltmarsh. The established saltmarsh was rich in plants and had a well-developed (aggregated) soil structure. These soils had a moderate to high resistance to erosion (τ 0 crt=2.45 N m -2) and shear strength (τ f=25.6 kPa) . Undrained sediment shear strength, τf, obtained with the fall-cone apparatus can also provide a useful indication of critical erosion shear stress, τ0 crt . Values of τ0 crt , measured across this site were all relatively large compared with computed bed stresses arising from locally generated waves. Thus this experimental managed realignment site was found to be primarily depositional and was thus successfully achieving the twin aims of protecting the coast from erosion and extending a rich ecosystem.

A novel approach to estimating potential maximum heavy metal exposure to ship recycling yard workers in Alang, India.

PubMed

Deshpande, Paritosh C; Tilwankar, Atit K; Asolekar, Shyam R

2012-11-01

The 180 ship recycling yards located on Alang-Sosiya beach in the State of Gujarat on the west coast of India is the world's largest cluster engaged in dismantling. Yearly 350 ships have been dismantled (avg. 10,000 ton steel/ship) with the involvement of about 60,000 workers. Cutting and scrapping of plates or scraping of painted metal surfaces happens to be the commonly performed operation during ship breaking. The pollutants released from a typical plate-cutting operation can potentially either affect workers directly by contaminating the breathing zone (air pollution) or can potentially add pollution load into the intertidal zone and contaminate sediments when pollutants get emitted in the secondary working zone and gets subjected to tidal forces. There was a two-pronged purpose behind the mathematical modeling exercise performed in this study. First, to estimate the zone of influence up to which the effect of plume would extend. Second, to estimate the cumulative maximum concentration of heavy metals that can potentially occur in ambient atmosphere of a given yard. The cumulative maximum heavy metal concentration was predicted by the model to be between 113 μg/Nm(3) and 428 μg/Nm(3) (at 4m/s and 1m/s near-ground wind speeds, respectively). For example, centerline concentrations of lead (Pb) in the yard could be placed between 8 and 30 μg/Nm(3). These estimates are much higher than the Indian National Ambient Air Quality Standards (NAAQS) for Pb (0.5 μg/Nm(3)). This research has already become the critical science and technology inputs for formulation of policies for eco-friendly dismantling of ships, formulation of ideal procedure and corresponding health, safety, and environment provisions. The insights obtained from this research are also being used in developing appropriate technologies for minimizing exposure to workers and minimizing possibilities of causing heavy metal pollution in the intertidal zone of ship recycling yards in India. Copyright © 2012 Elsevier B.V. All rights reserved.

Evaluating Tidal Marsh Sustainability in the Face of Sea-Level Rise: A Hybrid Modeling Approach Applied to San Francisco Bay

PubMed Central

Stralberg, Diana; Brennan, Matthew; Callaway, John C.; Wood, Julian K.; Schile, Lisa M.; Jongsomjit, Dennis; Kelly, Maggi; Parker, V. Thomas; Crooks, Stephen

2011-01-01

Background Tidal marshes will be threatened by increasing rates of sea-level rise (SLR) over the next century. Managers seek guidance on whether existing and restored marshes will be resilient under a range of potential future conditions, and on prioritizing marsh restoration and conservation activities. Methodology Building upon established models, we developed a hybrid approach that involves a mechanistic treatment of marsh accretion dynamics and incorporates spatial variation at a scale relevant for conservation and restoration decision-making. We applied this model to San Francisco Bay, using best-available elevation data and estimates of sediment supply and organic matter accumulation developed for 15 Bay subregions. Accretion models were run over 100 years for 70 combinations of starting elevation, mineral sediment, organic matter, and SLR assumptions. Results were applied spatially to evaluate eight Bay-wide climate change scenarios. Principal Findings Model results indicated that under a high rate of SLR (1.65 m/century), short-term restoration of diked subtidal baylands to mid marsh elevations (−0.2 m MHHW) could be achieved over the next century with sediment concentrations greater than 200 mg/L. However, suspended sediment concentrations greater than 300 mg/L would be required for 100-year mid marsh sustainability (i.e., no elevation loss). Organic matter accumulation had minimal impacts on this threshold. Bay-wide projections of marsh habitat area varied substantially, depending primarily on SLR and sediment assumptions. Across all scenarios, however, the model projected a shift in the mix of intertidal habitats, with a loss of high marsh and gains in low marsh and mudflats. Conclusions/Significance Results suggest a bleak prognosis for long-term natural tidal marsh sustainability under a high-SLR scenario. To minimize marsh loss, we recommend conserving adjacent uplands for marsh migration, redistributing dredged sediment to raise elevations, and concentrating restoration efforts in sediment-rich areas. To assist land managers, we developed a web-based decision support tool (www.prbo.org/sfbayslr). PMID:22110638

Burrow characteristics of the mud shrimp Austinogebia edulis, an ecological engineer causing sediment modification of a tidal flat

PubMed Central

Das, Shagnika; Tseng, Li-Chun; Wang, Lan

2017-01-01

The mud shrimp Austinogebia edulis, being abundant in the intertidal zone of western Taiwan, constructs deep burrows (>1 m). This study highlights the potential of mud shrimps to modify sediment characteristics of the tidal flat by its burrowing behavior. We studied the structure of the burrow wall, compared the difference in the sediment composition of the burrow and the background sediment, and compared the organic content inside the burrow wall. This study was carried out from September 2015 to November 2016 in three areas of the western coast of Taiwan, namely Shengang, Hanbow, and Wangong. The present study found significant differences between burrow wall and the burrow lumen. The diameter of the burrow wall was double as wide as the inner burrow lumen at the opening and gradually increased to 10 times of the burrow lumen at 30 cm depth. The burrow wall of A. edulis showed low permeability and increased the sheer strength. Statistically, a significant difference was noticed in the comparison between the sediment composition of the burrow wall and the background (p < 0.05, Student’s t-test). An accumulation of 3.63 for fine sand (t = -5.22, p < 0.001, fine sand) and 9 for clay (t = -25.01, p < 0.001, clay) was found in the upper burrow wall of A. edulis. This indicated that they somehow chose finer particles to build burrows. This will gradually change the sediment distribution—vertically and horizontally. The burrow wall consisted of a 24 times higher organic matter content than one individual of mud shrimp. The burrow may provide organic material as a potential food source. The mud shrimp thus transforms the sediment characteristics as an ecological engineer, which is expected to have a significant ecological impact on the ecosystem. PMID:29236717