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1

Aerobic methanotrophs drive the formation of a seasonal anoxic benthic nepheloid layer in monomictic Lake Lugano  

NASA Astrophysics Data System (ADS)

In the southern basin of Lake Lugano, thermal stratification of the water column during summer and autumn leads to a lack of exchange between surface and deep water masses, and consequently to seasonal bottom water anoxia, associated with high methane concentrations. With the onset of bottom water anoxia, a dense layer of high particulate matter concentration - a so-called benthic nepheloid layer (BNL) - develops in the bottom waters. A sharp redox gradient marks the upper boundary of the BNL. At its maximum, the BNL extends 15 - 30 m from the sediment into the water column. We investigated the identity of the BNL and key environmental factors controlling its formation in the framework of a seasonal study. Compound specific C-isotope measurements and Fluorescence In Situ Hybridisation (FISH) of suspended particulate organic matter, radioactive tracer based measurements of methane oxidation, as well as investigation of geochemical water column parameters were performed in spring and autumn. Our analyses revealed that the microbial biomass within the BNL is dominated by methanotrophic bacteria. Aerobic methane oxidation (MOx) was restricted to a narrow zone at the top of the BNL, reaching maximum rates of up to 1.8 ?M/day. The rates of MOx activity effectively consumed most (>99%) of the uprising methane, leading to the formation of a sharp CH4 concentration gradient and a strongly suppressed kinetic isotope effect (? = -2.8o). CH4 oxidation was limited by the diffusive supply of O2 from the upper hypolimnion, implying that methanotrophy is the primary driver of the seasonal expansion of the anoxic bottom water volume, and explaining the vertical migration of the BNL in response to its own O2 consumption. The bulk organic matter extracted from the BNL was strongly depleted in 13C (?13C < -60o), providing evidence for the incorporation of CH4-derived carbon into the biomass, suggesting that the BNL was composed of MOx-communities. This was further evidenced by four dominant fatty acid biomarkers (C16:1?5, C16:1?6, C16:1?7, and C16:1?8), which were strongly C-isotopically depleted, with ?13C values between -62o (?6) and -80o (?7). The fingerprint of isotopically depleted FAs indicates a dominance of Type I MOx bacteria in the BNL, which we could confirm with FISH using specific probes. Isotope mixing considerations suggest that 77 - 96 % of fatty acid carbon in the BNL is CH4-derived. FISH revealed that up to 30% of microbial cells in the BNL are methanotrophic. The cell size of methanotrophs was significantly larger than of other microbial cells, and an independent approach to quantify the contribution of methanotroph-carbon to the BNL biomass, based on methanotrophic cell size, confirmed our C-isotope-based estimate.

Blees, Jan; Niemann, Helge; Wenk, Christine B.; Zopfi, Jacob; Schubert, Carsten J.; Jenzer, Joël S.; Veronesi, Mauro L.; Lehmann, Moritz F.

2014-05-01

2

Development of the benethic nepheloid layer on the south Texas continental shelf, western Gulf of Mexico  

USGS Publications Warehouse

A monitoring study of suspended sediment on the South Texas Continental Shelf indicates that a turbid benthic nepheloid layer is regionally persistent. A sequence of quasi-synoptic measurements of the water column obtained during six cruises in an 18-month period indicates substantial spatial and temporal variability in nepheloidlayer characteristics. Regionally, the thickness of the shelf nepheloid layer increases both seaward and in a convergent alongshelf direction. Greatest thicknesses occur over a muddy substrate, indicating a causal relationship; maximum observed local thickness is 35 m which occurs along the southern shelf break. Analyses of suspended particulate matter in shelf bottom waters indicate mean concentrations ranging from 49 ?? 104 to 111 ?? 104 particle counts/cc; concentrations persistently increase shoreward throughout the region. Bottom particulate matter is predominantly composed of inorganic detritus. Admixtures of organic skeletal particles, primarily diatoms, are generally present but average less than 10% of the total particulate composition. Texturally, the particulate matter in bottom waters is predominantly poorly sorted sediment composed of very fine silt (3.9-7.8 ??m). The variability in nepheloid-layer characteristics indicates a highly dynamic shelf feature. The relationship of nepheloid-layer characteristics to hydrographic and substrate conditions suggests a conceptual model whereby nepheloid-layer development and maintenance are the results of the resuspension of sea-floor sediment. Bottom turbulence is attributed primarily to vertical shear and shoaling progressive internal waves generated by migrating shelf-water masses, especially oceanic frontal systems, and secondarily to shoaling surface gravity waves. ?? 1981.

Shideler, G. L.

1981-01-01

3

Nepheloid layer distribution in the Benguela upwelling area offshore Namibia  

NASA Astrophysics Data System (ADS)

The distribution of nepheloid layers across the outer shelf and upper continental slope off Namibia was studied during a cruise with R.V. Meteor in late austral summer 2003. Optical measurements, carried out with a transmissometer and a backscattering fluorometer, are correlated with suspended particulate matter (SPM) and particulate organic carbon (POC) values from water sample filtration. Conductivity-temperature-depth and oxygen data are used to relate the nepheloid layers to hydrographic structures. The particle content of surface water at the continental slope is controlled primarily by the offshore extension of highly productive upwelling filaments. A pronounced bottom nepheloid layer (BNL) covers the entire area of study with maximum intensity above the outer shelf and at the shelf break—an area where erosional forces dominate. The detachment of this BNL at the shelf break feeds a major intermediate nepheloid layer (INL) at 25.5°S. This INL is positioned at 250-400 m depth, at the lower boundary of an oxygen minimum zone, and is likely connected to the poleward flow of South Atlantic Central Water (SACW) across the shelf break. Together, these strong subsurface nepheloid layers are indicators of intensive lateral particle transport from the outer shelf towards a depocenter of organic matter on the upper continental slope.

Inthorn, Maik; Mohrholz, Volker; Zabel, Matthias

2006-08-01

4

Responses of deep-water shrimp populations to intermediate nepheloid layer detachments on the Northwestern Mediterranean continental margin  

Microsoft Academic Search

A clear link between the distribution of intermediate nepheloid layer detachments on the Northwestern Mediterranean continental margin and the population structure of five congeneric megafaunal species of deep-water benthic shrimps inhabiting different depth ranges between 100 and 1100m was found. The results of the multidisciplinary approach presented in this study provide evidence for the ecological conditions that affect the spatial

Pere Puig; Francesc Sardà; Albert Palanques

2001-01-01

5

The importance of subsurface nepheloid layers in transport and delivery of sediments to the eastern Cariaco Basin, Venezuela  

NASA Astrophysics Data System (ADS)

Optical transmissometer measurements were coupled with particulate organic matter (POM) observations to understand suspended sediment composition and distribution in the eastern Cariaco Basin during the rainy seasons of September 2003 and 2006. Our results suggest that nepheloid layers originating at the mouth of small mountainous rivers discharging into the eastern Basin are a major delivery mechanism of terrigenous sediments to the Basin interior. Intermediate nepheloid layers (INL) were observed near the shelf break (˜100 m) and appear to effectively transport terrigenous material laterally from the shelf to deep waters, thereby providing a plausible supply mechanism of the terrestrial material observed in sediment traps. These findings highlight the importance of small, local rivers in the Cariaco Basin as sources of terrestrial material. In contrast, these nepheloid layers contained only limited POM. When this information is combined with published sediment trap POM data, it suggests that nepheloid layers may not be a primary mechanism for delivering terrigenous POM to the deeper waters of the basin during the rainy season. Rather, BNL may redistribute marine-derived POM from shallow waters to the Basin's interior by providing ballast materials, particularly during episodic events driven by wind and precipitation. Though we have determined that nepheloid layers play an important role in the seaward transport of particulate material in the Cariaco Basin, their composition and temporal variability have not been fully characterized. This is critical to understand lateral particle transport, since nepheloid layers constitute a significant source of sediment to the deep Cariaco Basin.

Lorenzoni, Laura; Thunell, Robert C.; Benitez-Nelson, Claudia R.; Hollander, David; Martinez, Nahysa; Tappa, Eric; Varela, Ramón; Astor, Yrene; Muller-Karger, Frank E.

2009-12-01

6

Nepheloid Layers: Origin and Development In A Narrow Continental Shelf (nw Portugal)  

NASA Astrophysics Data System (ADS)

A general hydrographic, nephelometric and sedimentological surveying of the NW Portuguese continental shelf and slope was undertaken, under winter and spring con- ditions in order to elaborate a conceptual model of suspended sediments (nepheloid layer) dynamics. Two major situations were found: 1) Spring/Summer - with northerly winds (upwelling) and low energetic wave regime that favour the deposition of sedi- ments. The northerly winds promote offshore transport in the surface nepheloid layer (SNL) and the establishment of a seasonal thermocline allow the expansion of the SNL to the west. The SNL can reach or even cross the shelf-break (?50 km from coastline). Particulate organic carbon (POC) content in this layer highlights the higher contribution of biogenic particles (average concentration of 22%); 2) Winter, with southerly winds (downwelling) and high energetic wave regime that favour mid- shelf sediments resuspension and offshore transport in the bottom nepheloid layer (BNL). In the shelf-break the BNL detached to form intermediate nepheloid layers (INL). The SNL is restricted to the inner shelf. The effect of southerly winds gener- ates shoreward Ekman transport and detains the offshore westward extension of this layer even during high river run-off periods. The POC content indicates a dominance of litogenic particles in suspension (average concentration of 8%). Over the mid- and inner-shelf the dominant resuspension mechanism is associated with surface waves (Vitorino et al., 2002). Estimates based on wave measurements at mid-shelf (86m depth) suggested that, in winter, the wave shear velocity frequently exceeds 1 cm/s, assumed as the critical shear velocity for the resuspension of the fine grained sedi- ments (34?m) of the bottom cover. Storm events, such as the one observed in November 1996 easily increase the wave shear velocities over 3 cm/s, leading to the increase of the BNL thickness (20-30m) (Vitorino et al., 2002; Oliveira et al., 2002). Low-frequency currents (periods longer than about 2 days) and internal waves can also lead to the resuspension of fine bottom sediments. Shelf morphology (outer shelf re- lieves and Porto submarine canyon) and sedimentary cover can also affect both spatial and vertical development of BNL.

Oliveira, A.; Vitorino, J.; Rodrigues, A.; Jouanneau, J. M.; Weber, O.; Dias, J. A.

7

The importance of subsurface nepheloid layers in transport and delivery of sediments to the eastern Cariaco Basin, Venezuela  

Microsoft Academic Search

Optical transmissometer measurements were coupled with particulate organic matter (POM) observations to understand suspended sediment composition and distribution in the eastern Cariaco Basin during the rainy seasons of September 2003 and 2006. Our results suggest that nepheloid layers originating at the mouth of small mountainous rivers discharging into the eastern Basin are a major delivery mechanism of terrigenous sediments to

Laura Lorenzoni; Robert C Thunell; Claudia R. Benitez-Nelson; David Hollander; Nahysa Martinez; Eric Tappa; Ramón Varela; Yrene Astor; Frank E. Muller-Karger

2009-01-01

8

Suspended particulate loads and transports in the nepheloid layer of the abyssal Atlantic Ocean  

USGS Publications Warehouse

Vertical profiles of light scattering from over 1000 L-DGO nephelometer stations in the Atlantic Ocean have been used to calculate mass concentrations of suspended particles based on a calibration from the western North American Basin. From these data are plotted the distributions of particulate concentrations at clear water and in the more turbid near-bottom water. Clear water is the broad minimum in concentration and light scattering that occurs at varying mid-depths in the water column. Concentrations at clear water are as much as one-to-two orders of magnitude lower than those in surface water but still reflect a similar geographic distribution: relatively higher concentrations at ocean margins, especially underneath upwelling areas, and the lowest concentrations underneath central gyre areas. These distributions within the clear water reflect surface-water biogenic productivity, lateral injection of particles from shelf areas and surface circulation patterns and require that the combination of downward vertical and horizontal transport processes of particles retain this pattern throughout the upper water column. Below clear water, the distribution of standing crops of suspended particulate concentrations in the lower water column are presented. The integration of mass of all particles per unit area (gross particulate standing crop) reflects a relative distribution similar to that at the surface and at clear water levels, superimposed on which is the strong imprint of boundary currents along the western margins of the Atlantic. Reducing the gross particulate standing crop by the integral of the concentration of clear water yields a net particulate standing crop. The distribution of this reflects primarily the interaction of circulating abyssal waters with the ocean bottom, i.e. a strong nepheloid layer which is coincident with western boundary currents and which diminishes in intensity equatorward. The resuspended particulate loads in the nepheloid layer of the basins west of the Mid-Atlantic Ridge, resulting from interaction of abyssal currents with the bottom, range from ??? 2 ?? 106 tons in the equatorial Guyana Basin to ??? 50 ?? 106 tons in the North American Basin. The total resuspended particulate load in the western basins (111 ?? 106 tons) is almost an order of magnitude greater than that in the basins east of the Mid-Atlantic Ridge (13 ?? 106 tons). The net northward flux of resuspended particles carried in the AABW drops from ??? 8 ?? 106 tons/year between the southern and northern ends of the Brazil Basin and remains ??? 1 ?? 106 tons/year across the Guyana Basin. ?? 1977.

Biscaye, P. E.; Eittreim, S. L.

1977-01-01

9

Chemical Characterization of Suspended Particulate Organic Matter by Pyrolysis-Gas Chromatography Coupled with Mass Spectrometry and High Performance Liquid Chromatography in the Bottom Nepheloid Layer of the Rhône Delta  

NASA Astrophysics Data System (ADS)

During the DYPOL-6 Mission in the Rhône delta the use of a metallic frame provided water samples at three levels of the underlying water column, 2, 1, and 0·5 m above the sea bottom. These sampling levels allowed determination of the characteristics of suspended organic material at the deeper layers of the bottom nepheloid layer and, eventually, their relations with the overlying suspended particulate matter. The results obtained by the measurement of the suspended particulate organic matter, the elemental analysis, the analysis of the main classes of organic compounds by pyrolysis-gas chromatography coupled with mass spectrometry and the determination of phenolic compounds by high performance liquid chromatography (HPLC) emphasized the functional characteristics of the Rhône deltaic system. Near the bottom, the lower water levels of the benthic nepheloid layer showed some obvious biogeochemical gradients related to the location of the sampling station: the amount of pyrolysis-derived phenolic compounds, aromatic hydrocarbons and carbohydrates in the suspended material was high at the stations directly exposed to input of the Rhône River. The stations from the river mouth to offshore areas showed the influence of the Rhône inflow. But sometimes, according to the river regime and the current orientation, the influence of the Liguro-provencal current oriented East-West was noticeable even near the river mouth. In the eastern region of the surveyed area, the stations submitted to this current indicated some specific characteristics: the nepheloid layer, concentrated 1 m above the bottom, had a high particulate organic carbon content and a relatively high amount of phenolic compounds which indicated a possible seagrass ( Posidonia oceanica) origin. At the more seaward stations, although the influence of the river input was always detectable, the suspended particulate matter was less abundant and essentially supplied by the local biogenic input: the lower water levels were enriched in compounds yielding acetonitrile upon pyrolysis, i.e. nitrogen-containing compounds. If the proximity of the river source and regime influenced the suspended particulate matter distribution and the geochemical characteristics of organic matter, the evolution through time of the bottom turbid flow from one station to another also had a great influence. Near the bottom, the terrestrial character is shown in the shoreward stations by high contents of pyrolysis-derived aromatic hydrocarbons and phenols as well as by lignin-derived phenolic compounds analysed by HPLC. In contrast, a marine character appeared in the seaward stations, emphasized by high values of pyrolysis-derived compounds indicative of carbohydrates and nitrogenous compounds as well as by phenolic compounds representative of phytoplankton production. However the upper water layers of the bottom nepheloid were generally more influenced by terrestrial input. Some trends emphasizing a microstratification of the water layers in the deeper levels of the bottom nepheloid, related to the existence of very thin bottom currents, or, maybe, to resuspension processes resulting from the bottom proximity, were shown by the geochemical characteristics of the three water levels analysed.

Gadel, François; Charrière, Bruno; Serve, Léon

1993-09-01

10

Sedimentary sources of old high molecular weight dissolved organic carbon from the ocean margin benthic nepheloid layer  

Microsoft Academic Search

Average 14C ages of dissolved organic carbon (DOC) in the ocean are 3–6,000 years, and are influenced by old DOC from continental margins. However, sources of DOC from terrestrial, autochthonous, and sedimentary organic carbon seem to be too young to be responsible for the old DOC observed in the ocean. Since colloidal organic carbon (COC, i.e., high molecular weight DOC),

Laodong Guo; Peter H. Santschi

2000-01-01

11

Bay of Bengal nutrient-rich benthic layer  

NASA Astrophysics Data System (ADS)

A nutrient- and carbon-rich, oxygen-poor benthic layer is observed in the lower 100 m of the central and western Bay of Bengal, at depths between 3400 to 4000 m. The observed ratios for the biogeochemical anomalies in the benthic layer water are similar to those observed for phytoplankton blooms in open oceans and hence suggest that the source of the high silica, phosphate, nitrate and carbon is likely to be due to decomposition of marine plankton deposited on the Ganges fan. While similar sediment types are expected to exist across a more extensive area of the Bay of Bengal, accumulation of nutrients only within a confined pool of bottom water is due to a greater degree of ventilation elsewhere. To the north of the nutrient-rich benthic pool, in shallower water, inflow of water from West Australian Basin minimizes anomalous benthic properties. To the south, in deeper water, ventilation by bottom water of the Central Indian Basin lifts the Bay of Bengal nutrient-rich benthic water off the sea floor. Thus the nutrient-rich benthic layer occupies zone between better ventilated regions. A counter-clockwise flow of bottom water is suggested for the Bay of Bengal, with nutrient-rich bottom water flowing westward south of Sri Lanka.

Gordon, Arnold L.; Giulivi, Claudia F.; Takahashi, Taro; Sutherland, Stewart; Morrison, John; Olson, Donald

12

Particle flux and properties affecting the fate of bacterial productivity in the benthic boundary layer at a mud-bottom site in South-Central Gulf of Riga  

NASA Astrophysics Data System (ADS)

At a deep-water station in South-Central Gulf of Riga (Stn. 119), the use of a multitrap for high time-resolution in the benthic boundary layer (BBL) enabled a refinement of the analytical endmember approach of Gasith [Gasith, A., 1975. Tripton sedimentation in eutrophic lakes — simple correction for the resuspended matter. Verh. Internat. Verein. Limnol., 19, pp. 116-122.] by which vertical flux emanating from surface waters may be distinguished from resuspension flux. As a consequence, the quantity of both slow- and fast-falling particles could be resolved also in bottom-water samples. Among events recorded during three intensive field studies were (1) a surface water export event in early May 1995, whereby net vertical flux increased from around 1 to 2-5 g m -2 d -1; (2) friction velocities at 1.4 cm s -1 causing a marked nepheloid layer, strained oxygenation and a characteristic high bacteria/chlorophyll ratio; (3) strong current-induced resuspension as the immediate response of a low-pressure passage around mid-summer 1994; and (4) a distinctly green and fresh pulse of phytoplankton arriving in less than 12 h in late August 1993. Results confirm previous observations of (1) strong benthic-pelagic coupling subject to event-controlled pulses of surface water export; furthermore, (2) the confined nature of the nepheloid layer with a bimodal falling-velocity distribution showing on the one hand rapidly falling (at 10 m d -1) aggregates and on the other hand slower-falling (at <1 m d -1) particles, the latter with a lower nitrogen content but both varying in concentration and presumably interacting through scavenging and fluff layer disaggregation; (3) how weather-controlled bottom currents regularly and easily entrain organic matter from the sediment-water interface. They also (4) suggest microbial activity in the BBL to be more associated with the slow-falling particles. Findings seem reconcilable with the notion of microbial benefits from staying suspended in the BBL rather than inside aggregates and the fluff layer.

Floderus, Sören; Jähmlich, Sabine; Ekebom, Jan; Saarso, Mart

1999-12-01

13

Sediment trap fluxes and benthic recycling of organic carbon, polycyclic aromatic hydrocarbons, and polychlorobiphenyl congeners in Lake Superior  

Microsoft Academic Search

Sediment trap fluxes of solids, organic carbon, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were measured in Lake Superior in 1984 and 1985. Mass fluxes from surface waters ranged from 0.14 to 1.1 g\\/m²{center dot}day and increased near the lake floor due to resuspension of surficial sediment and horizontal transport in the benthic nepheloid layer. Organic matter fluxes from

Joel E. Baker; Steven J. Eisenreich; Brian J. Eadie

1991-01-01

14

Spatial and temporal variability of particulate matter in the benthic boundary layer at the N.W. European Continental Margin (Goban Spur)  

NASA Astrophysics Data System (ADS)

Near bottom water samples and sediments were taken during five cruises to 6 stations forming a transect across the N.W. European Continental Margin at Goban Spur. Flow velocity spot measurements in the benthic boundary layer (BBL) always increased from the shelf to the upper slope (1470 m) from 5 to 9 cm s -1 in spring/summer and from 15 to 37 cm s -1 in autumn/winter. Decreasing values were detected at the lower slope (2000 m) and the lowest values of ca. 2 cm s -1 at the continental rise at 4500 m water depth. Long term measurements with a benthic lander at 1470 m show that currents have a tidal component and reach maximum velocities up to 20 cm s -1, sufficiently high periodically to resuspend and transport phytodetritus. During these long-term observations, currents were always weaker in spring/summer than in autumn/winter. Critical shear velocities of shelf/slope sediments increased with depth from 0.5 to 1.7 cm s -1 and major resuspension events and Intermediate Nepheloid Layers (INLs) should occur around 1000 m. Chloroplastic Pigment Equivalents (CPE) ranged from 0.0 to 0.21 ?g dm -3, Particulate Organic Carbon (POC) from 12 to 141 ?g dm -3 and Total Particulate Matter (TPM) from 0.2 to 10.0 mg dm -3. Aggregates in the BBL occurred with a median diameter of 152 to 468 ?m. Data on suspended particulate matter in the near-bottom waters showed that hydrodynamic sorting within the particulate organic fraction occurred. Phytodetritus was packaged in relatively large aggregates and contributed little to the total organic carbon pool in nearbottom waters (CPE/POC ca.0.2%). The main organic fraction has low settling velocities and high residence times within the benthic boundary layer. As POC was not concentrated in the near bed region the degree to which carbon is accessible to the benthic community depends on aggregate formation, subsequent settling and/or biodeposition of the POC. Close to the sea bed downslope transport may dominate. Under flow conditions high enough to resuspend fresh phythodetritus from sediments at the productive shelf edge, this could be transported to 1500 m (Goban Spur) or abyssal depth (Canyon site between Meriadzek and Goban Spur) within 21 days.

Thomsen, L.; van Weering, Tj. C. E.

1998-12-01

15

The benthic boundary layer approach and its application to Lake Päijänne, Finland  

Microsoft Academic Search

Resuspension of bottom sediments is the net result of a wide variety of different fluid mechanical processes with characteristic time and length scales that extend over six orders of magnitude. The sum of these effects is most heavily concentrated in a layer adjacent to the bottom called the benthic boundary layer (BBL). The physics of BBL must be understood before

T. Huttula

1992-01-01

16

Abyssal hydrography, nephelometry, currents, and benthic boundary layer structure in the Vema channel  

Microsoft Academic Search

New data from closely spaced hydrocasts, thermograd profiles, vertical nephelometer profiles, and direct bottom current observations within the Vema Channel (near 30°13'S) allow an interpretation of the flow regime and the structure of the benthic boundary layer. A sharp gradient in potential temperature, light scattering, concentration of suspended particulates, and excess radon is present in the transition zone between northward

David A. Johnson; Scott E. McDowell; Lawrence G. Sullivan; Pierre E. Biscaye

1976-01-01

17

Hydrographic structure and nepheloid spatial distribution in the Gulf of Lions continental margin  

NASA Astrophysics Data System (ADS)

A general hydrographic and nephelometric survey of the Gulf of Lions margin was undertaken, under autumn conditions. The distribution of suspended material along the margin during this experiment is controlled, at least in part, by the following factors: (a) the hydrography of the shelf-slope waters, i.e. the nepheloid layers follow the isopyenals; and (b) the cyclonic circulation of the water masses (the Liguro-Provençal Current and, in particular the proximity and depth of the Levantine Intermediate Water circulation). On the northeastern part of the margin along the slope, the seaward extension of the nepheloid layers is sharply bounded and is concentrated in canyon heads by the general water circulation. In the southwestern part, the decreasing depth of the major flow of the general circulation and its increased distance seaward from the upper slope allow the seaward and downward expansion of the nepheloid structures. The suspended material extending offshore is swept away and diluted by the general circulation. The stepwise increase toward the southwest, in suspended particulate contents in the slope waters between the northeastern and southwestern ends of the Gulf of Lions, is assumed to be due mainly to inputs from the shelf through the canyons. The Marseille canyon, at the northeastern part of the Gulf of Lions margin, is influenced less by the Rhoˆne and other rivers of the shelf. The influence of the Rhoˆne is seen first at the longitude of the Rhoˆne's canyons. In the southwestern part of the Gulf, the Bourcart and Lacaze-Duthiers canyons are areas through which the suspended material, originating from the whole shelf, passes.

Durrieu de Madron, X.; Nyffeler, F.; Godet, C. H.

1990-09-01

18

Temporal variability in currents and the benthic boundary layer at an abyssal station off central California  

Microsoft Academic Search

Current meter records from seven sequential moorings were collected during 1993–1996 at an abyssal station off central California (Sta. M; 4100m depth). The entire 214-yr time series of the flow at 600, 50, and 2.5m above bottom (above, near the top of, and within the benthic boundary layer) were analyzed for mean flow statistics and subtidal and tidal variability. The

Stace Beaulieu; Roberta Baldwin

1998-01-01

19

Escaping the flow: boundary layer use by the darter Etheostoma tetrazonum (Percidae) during benthic station holding.  

PubMed

Aquatic habitats characterized by directional water flow (lotic environments) pose numerous challenges to their inhabitants, including the constant threat of dislodgement and downstream transport. As a result, many organisms exhibit morphological and/or behavioral adaptations that facilitate midwater or benthic station holding in these environments, such as the ventral sucker disc of armored catfishes. However, a few groups, including the species-rich group of small (7-8 cm long and 1-2 cm high) North American stream fishes called darters, exhibit no obvious morphological adaptations to life in lotic habitats. We therefore asked whether small size itself facilitates benthic station holding in these fish. We first used digital particle image velocimetry to quantify the fluid dynamics of flow over a variety of substrates. We then visualized the patterns of flow over the darter Etheostoma tetrazonum during benthic station holding. The thickness of the region of decreased water velocity (i.e. the boundary layer) associated with several types of rocky substrate was large enough (?2 cm high in some cases) for E. tetrazonum and many other darter species to escape the oncoming flow. We also found that, despite the large size of its pectoral fins, E. tetrazonum is capable of producing only very weak negative lift forces with fins. These substrate-directed forces likely act in conjunction with upstream-directed frictional forces between the tail, anal and pelvic fins and the substrate to facilitate station holding. Thus, we hypothesize that, in darters, small size is an adaptation to life in the benthic boundary layer of lotic environments. PMID:21389204

Carlson, Rose L; Lauder, George V

2011-04-01

20

Temporal variability in currents and the benthic boundary layer at an abyssal station off central California  

NASA Astrophysics Data System (ADS)

Current meter records from seven sequential moorings were collected during 1993-1996 at an abyssal station off central California (Sta. M; 4100 m depth). The entire 2 1/4-yr time series of the flow at 600, 50, and 2.5 m above bottom (above, near the top of, and within the benthic boundary layer) were analyzed for mean flow statistics and subtidal and tidal variability. The mean current vectors at each altitude were southward at <1 cm s -1, although not significantly different from zero. Spectral analysis revealed energetic mesoscale and seasonal oscillations in the flow, indicated by peaks in principal axis magnitudes at periods of 50-175 days. Tidal (mainly semidiurnal) and inertial forcing contributed to flow variability and influenced the mean principal axis orientation calculated for each record. The highest flow speeds were recorded at 50 m above bottom (with an average of 3.8 cm s -1; maximum 18.2 cm s -1). An examination of monthly-averaged current vectors at this altitude revealed that flow was to the south during the months of highest flow speed (April 1994 and 1995 and October 1994) and to the north and west during the months of lowest flow speed (July 1994 and August 1995). Profiles of light transmission and potential temperature, collected intermittently during the 2 1/4-yr period, showed that the benthic mixed layer at Sta. M extended on average 40 m above bottom (range 15-80 mab). Evidence for local resuspension of recently deposited detritus came from time-lapse photographs of the sea floor that showed a period of near-bottom turbidity that corresponded to a period of high near-bottom flow. However, rough estimates of friction velocity indicated that the bed stress usually was too low at Sta. M to cause local resuspension of sediments. We hypothesize that the observed benthic mixed layers contained suspended particles advected from more energetic areas to the north of Sta. M.

Beaulieu, Stace; Baldwin, Roberta

21

Monitoring the recolonization of the Mt Pinatubo 1991 ash layer by benthic foraminifera  

Microsoft Academic Search

Benthic foraminifera from the South China Sea were studied to assess mass mortality and to monitor the composition and recovery of the benthic communities following the 1991 Mt Pinatubo ashfall. Surface distribution data from monitoring stations in the eastern South China Sea that were occupied during four cruises between spring 1994 and summer 1998 display the following trends in recolonization

Silvia Hess; Wolfgang Kuhnt; Simon Hill; Michael A. Kaminski; Ann Holbourn; Marietta de Leon

2001-01-01

22

Nitrogen15 Isotope Enrichment in Benthic Boundary Layer Gases of a Stratified Eutrophic Iron and Manganese Rich Lake  

Microsoft Academic Search

The applicability of the natural abundance of nitrogen gas isotope ratios was used to indicate the spatial distribution of\\u000a nitrogen transformations in the water column and sediment pore waters of Lake Ngapouri, a small (area 0.19 km2), monomictic, eutrophic lake in the Taupo Volcanic Zone, North Island, New Zealand. Samples were collected from the epilimnion,\\u000a hypolimnion, benthic boundary layer and at

L. K. Pearson; C. H. Hendy; D. P. Hamilton; W. B. Silvester

23

Life in the Benthic Boundary Layer: Connection to the Mid-Water and Sea Floor: Discussion  

Microsoft Academic Search

The abyssal benthopelagic zone is enriched in biomass and numbers of species, relative to the overlying water column. It is inhabited by (i) pelagic species whose ranges are truncated by the sea bed, (ii) normally benthic species who use the zone as a refuge, for dispersal or for locating their food, (iii) a specialized fauna, which includes many novel species

G. A. Boxshall; M. V. Angel

1990-01-01

24

Development of Technologies for Coastal Observing Systems and the Study of Benthic Boundary Layer Processes  

NSF Publications Database

... BBL - defined here as the portion of the water column and surface sediments impacted by the presence ... to comprise the bottom boundary layer of the water column and surface sediment layer. The dynamic ...

25

The role of horizontal exchanges on ventilation of the benthic boundary layer on the Black Sea shelf  

NASA Astrophysics Data System (ADS)

The state of the benthic component of the shelf ecosystem is strongly influenced by availability of dissolved oxygen. The chemical structure of the Black Sea waters is largely determined by the location and the strength of the pycnocline. Due to similarity in the mechanisms of vertical exchanges the oxycline and the chemocline occur at the same depth intervals as the halocline and pycnocline (Özsoy and Ünlüata, 1997). As the data for dissolved oxygen on the shelf is relatively sparse we assume that much abundant data on physical parameters (temperature and salinity) can be used as proxy in determining the location of the oxycline and hence the spatial extent of near-bottom waters depleted in oxygen. When the waters of the benthic boundary layers below the pycnocline are ‘locked' i.e. unable to mix vertically with surface then the biological pump and supply of oxygen are suppressed. However, the locked water can, in principle, move ‘horizontally', predominantly along the constant density levels and get ventilated via isopycnal exchanges. The isopycnals in the Black Sea have generally a dome-like structure, so that the isopycnal movements across the shelf break can ventilate bottom shelf waters with water masses from upper parts of the water column in the deep sea. We use the intra- and inter-annual variations in the near-bottom temperature as indicators for variability of physical conditions in the benthic boundary layer on the shelf. The physical reason for this is that interannual variations in the near-bottom temperature are directly related with the volume of cold waters (Ivanov et al., 2000) which are formed on the shelf and then exported into the deep sea, so that variations in temperature may indicate changes in the intensity of horizontal exchanges. In this paper we identified areas on the Black Sea margin where bottom waters can not be mixed vertically (‘locked' waters) during the winter months and locations to which the locked waters can move ‘horizontally'. The potential energy approach was used to identify the spatial and temporal variability of the areas and volumes occupied by the locked waters. This approach allows to assess a relative strength of the ability of locked waters to mix vertically with oxygen rich surface waters as compared to ‘horizontal' exchanges with the deep sea along isopycnic surfaces. Analysis of interannual variability of temperature showed that the period 1965-1983 was a warm period when the ‘summer' season ( May to November) temperatures of the benthic waters were higher than the average; to the contrary the period 1983-2001 (i.e. up to end of available data sets) was a cold period. Correlations between various time series of hydrographical and meteorological parameters were calculated to establish the relative importance of vertical versus horizontal exchanges in ventilation of the locked water masses. A low correlation (R=0.24) was obtained between the variation of the winter sea surface temperature on the shelf and the ‘summer' temperatures of locked waters. A higher correlation (R=0.56) was found between the summer temperatures of the Cold Intermediate Waters below the seasonal pycnocline in the deep sea (density range sigma-theta= 14.2-14.8) and the ‘summer' temperatures of the ‘locked' waters in the benthic boundary layer on the shelf. Analysis shows that the isopycnic exchanges with the deep sea are more important for ventilation of the benthic boundary layer on the shelf than winter convection on the shelf itself. This work was made possible via support from EU FP6 SESAME and EU FP7 MyOcean projects and NERC PhD studentship. References Özsoy, E. and Ünlüata, Ü., 1997. Oceanography of the Black Sea: a review of some recent results. Earth-Sci. Rev., 42(4): 231-272. Ivanov, L.I., Belokopytov, V.N., Özsoy, E. and Samodurov, A., 2000. Ventilation of the Black Sea pycnocline on seasonal and interannual time scales. Mediterr. Mar. Sci., 1/2: 61-74.

Shapiro, Georgy; Wobus, Fred

2010-05-01

26

Bacteria in the cold deep-sea benthic boundary layer and sediment-water interface of the NE Atlantic.  

PubMed

This is a short review of the current understanding of the role of microorganisms in the biogeochemistry in the deep-sea benthic boundary layer (BBL) and sediment-water interface (SWI) of the NE Atlantic, the gaps in our knowledge and some suggestions of future directions. The BBL is the layer of water, often tens of meters thick, adjacent to the sea bed and with homogenous properties of temperature and salinity, which sometimes contains resuspended detrital particles. The SWI is the bioreactive interface between the water column and the upper 1 cm of sediment and can include a large layer of detrital material composed of aggregates that have sedimented from the upper mixed layer of the ocean. This material is biologically transformed, over a wide range of time scales, eventually forming the sedimentary record. To understand the microbial ecology of deep-sea bacteria, we need to appreciate the food supply in the upper ocean, its packaging, passage and transformation during the delivery to the sea bed, the seasonality of variability of the supply and the environmental conditions under which the deep-sea bacteria grow. We also need to put into a microbial context recent geochemical findings of vast reservoirs of intrinsically labile organic material sorped onto sediments. These may well become desorped, and once again available to microorganisms, during resuspension events caused by deep ocean currents. As biotechnologists apply their tools in the deep oceans in search of unique bacteria, an increasing knowledge and understanding of the natural processes undertaken and environmental conditions experienced by deep-sea bacteria will facilitate this exploitation. PMID:10967208

Turley

2000-08-01

27

Particle flux and properties affecting the fate of bacterial productivity in the benthic boundary layer at a mud-bottom site in South-Central Gulf of Riga  

Microsoft Academic Search

At a deep-water station in South-Central Gulf of Riga (Stn. 119), the use of a multitrap for high time-resolution in the benthic boundary layer (BBL) enabled a refinement of the analytical endmember approach of Gasith [Gasith, A., 1975. Tripton sedimentation in eutrophic lakes — simple correction for the resuspended matter. Verh. Internat. Verein. Limnol., 19, pp. 116–122.] by which vertical

Sören Floderus; Sabine Jähmlich; Jan Ekebom; Mart Saarso

1999-01-01

28

Spatial and temporal variability of particulate matter in the benthic boundary layer at the N.W. European Continental Margin (Goban Spur)  

Microsoft Academic Search

Near bottom water samples and sediments were taken during five cruises to 6 stations forming a transect across the N.W. European Continental Margin at Goban Spur. Flow velocity spot measurements in the benthic boundary layer (BBL) always increased from the shelf to the upper slope (1470 m) from 5 to 9 cm s?1 in spring\\/summer and from 15 to 37

L. Thomsen; Tj. C. E. van Weering

1998-01-01

29

Benthic foraminifera from Capbreton Canyon revisited; faunal evolution after repetitive sediment disturbance  

NASA Astrophysics Data System (ADS)

At a 650 m deep site in the axis of Capbreton Canyon an 18-cm-thick turbidite was deposited in December 1999. During subsequent campaigns, an almost monospecific fauna of the benthic foraminifer Technitella melo, considered as a pioneer species, was found in May 2000. In 2001 this fauna had disappeared and was replaced by an exceptionally rich fauna strongly dominated by the opportunistic species Bolivina subaenariensis. We present sedimentological, radionuclide and foraminiferal data of new cores, sampled in 2005 and 2011, taken with the aim to study the further evolution of the benthic ecosystem. Cores sampled in 2005 show that in the canyon axis a new, ca. 5 cm thick, turbidite has been deposited. The live benthic foraminiferal faunas were much poorer than in 2001, but still had a high dominance and low diversity, although less extreme than in 2001. We conclude that in the canyon axis, benthic foraminiferal faunas remain in an early stage of ecosystem colonization. It appears that the very thick 1999 turbidite marks an exceptional event. The uncommonly rich faunas observed in 2001 could be a response to the concentration of organic-rich material in the fine-grained top of this deposit. In 2011, cores were sampled at a slightly different site, on the lower canyon flank. The sedimentary sequence here is marked by the absence of coarse turbidite layers, although some levels show slightly increased grain size, and lower 210Pbxs activities, indicative of an admixture with advected older sediments. Live foraminiferal faunas are much more equilibrated, as shown by their higher diversity, lower dominance, and deeper penetration into the sediment. All these characteristics are indicative of a much more stable ecosystem. Dead faunas are present throughout the core, indicating that the levels with slightly elevated grain size are not typical turbidites resulting from hyperpycnal currents (which are characterized by levels barren of foraminifera) but denote other, more long-term sedimentary processes leading to the advection of older material, such as bottom nepheloid layers, or repetitive fine-grained turbidite deposits due to small-scale slumping. The comparison of live and dead fauna shows that at both sites, the foraminiferal turnover rates are fairly low. At the lower canyon flank site sampled in 2011, the foraminiferal faunas are renewed every 1.5-2 years. Such a fairly long foraminiferal lifespan corresponds to earlier estimates, but is surprisingly high for the opportunistic taxa that dominate the faunal assemblages in these unstable and food-enriched submarine canyon settings.

Bolliet, T.; Jorissen, F. J.; Schmidt, S.; Howa, H.

2014-06-01

30

High Energy Benthic Boundary Layer Experiment (HEBBLE): Preliminary program plan and conceptual design  

NASA Technical Reports Server (NTRS)

Deep sea processes of flow-sediment interaction, particularly the role of high energy ocean bottom current events in forming the seafloor topography, transporting material, and mixing the bottom of the water column are examined. A series of observations at and near the sea bottom, in water depths of 4 to 5 km, in areas of the western North Atlantic where high energy current events occur, include site surveys and physical reconnaissance to identify suitable areas and positions, and one or more six month experiments to investigate temporal and spatial variations of high energy events within the boundary layer and their interaction with the seabed. Descriptions of proposed HEBBLE activities are included, with emphasis on technology transfer to the oceanographic community through design, fabrication, testing, and operation of an instrumented ocean bottom lander.

Frewing, K.

1980-01-01

31

Dynamics of the bathyal Benthic Boundary Layer in the northwestern Mediterranean: depth and temporal variations in macrofaunal–megafaunal communities and their possible connections within deep-sea trophic webs  

Microsoft Academic Search

The distribution patterns of benthopelagic fauna and the macrofauna–megafauna trophic relationships in the Benthic Boundary Layer (BBL) were studied. The study is based on data collected during 6 sampling cruises off the Catalan coast (western Mediterranean) during 1991–1995 at depths ranging from 389–1355 m. Crustaceans were the dominant benthopelagic macrofauna in the BBL level closest to the sea bed (~0–1.5

Joan E. Cartes

1998-01-01

32

Trophic interactions in the benthic boundary layer of the Beaufort Sea shelf, Arctic Ocean: Combining bulk stable isotope and fatty acid signatures  

NASA Astrophysics Data System (ADS)

The food web structure and diets of 26 taxa of benthic boundary layer (BBL) zooplankton on the Beaufort Sea shelf were studied using carbon and nitrogen stable isotopes and fatty acids. Mean ?15N values ranged from 7.3‰ for the amphipod Melita formosa to 14.9‰ for an unidentified polychaete, suggesting that taxa sampled came from three trophic levels. For 8 taxa, the lightest carbon signature occurred near the mouth of the Mackenzie River. Stable isotope ratios helped clarify the origin of signature fatty acids. Levels of certain polyunsaturated fatty acids (PUFA) were negatively correlated with ?15N, with the exception of 22:6?3, which was positively correlated with ?15N, suggesting that this essential PUFA was retained through the food web. Discriminant analysis proved to be a powerful tool, predicting taxa from fatty acid profiles with 99% accuracy, and revealing strong phylogenetic trends in fatty acid profiles. The amphipod Arrhis phyllonyx had higher levels of ?6 PUFA, especially 20:4?6 with several possible sources, than other peracarid crustaceans. The holothurian had high levels of odd numbered and branched chain fatty acids, indicative of bacterial consumption, while fatty acids of phytoplankton origin were important discriminants for Calanus hyperboreus and the chaetognaths Eukrohnia hamata and Parasagitta elegans. This relationship indicates that the conventional phytoplankton-copepod-chaetognath food web found in the water column also exists in the BBL. This observation, as well as generally low ?15N and high levels of certain PUFA in samples with lower ?15N, strongly suggests that BBL zooplankton on the Beaufort Sea shelf have access to fresh material of phytoplankton origin either by feeding on sedimenting matter or by active migration to surface waters.

Connelly, Tara L.; Deibel, Don; Parrish, Christopher C.

2014-01-01

33

Marine benthic dynamics  

SciTech Connect

The proceedings from this symposium contain an overview of the benthic ecosystem. The structure, population dynamics, and secondary production of benthic ecosystems are discussed in light of the role of detritus and nutrient cycling in the food chain. The twenty three articles of presentation are grouped by categories of secondary production, population studies, nutrient cycling, and detritus and are summarized and indexed with an abstract for each presentation. (DS)

Tenore, K.R.; Coull, B.C. (eds.)

1980-01-01

34

Do bottom mixed layers influence 234Th dynamics in the abyssal near-bottom water column?  

NASA Astrophysics Data System (ADS)

Dynamics of the natural radioactive particle tracer 234Th (half-life: 24.1 days) within the abyssal water column up to 1000 m above bottom and within surface sediments of the northeast Atlantic (Porcupine Abyssal Plain; depth: ?4845 m) were investigated. Distributions of transmissometer voltages and potential temperature indicated a subdivision of the near-bottom water column into a benthic mixed layer (BML; thickness: ?10-65 m) and the layer above the BML up to the upper boundary of the bottom nepheloid layer (BNL; thickness: ?1000 m). Comparison of 234Th fluxes (dpm m -2d -1) in sediment traps, vertical fluxes derived from 234Th/ 238U-disequilibrium in the near-bottom water column and excess 234Th inventories in the surface sediment provided evidence for lateral advection of 234Th-depleted water and a 'missing sink' for 234Th. A simple one-dimensional steady-state box-model approach was applied to investigate 234Th dynamics. Estimated residence times suggest the BML and the resuspension zone of the surface sediment to be highly dynamic systems with respect to particle cycling and sorptive reactions on a time scale of weeks. Model results indicate that, through the chemical forcing of changing particle concentration, a thickening BML results in (1) increasing residence times of particulate 234Th in the BML with respect to the net fluxes across the upper boundary of the BML and into the surface sediment; (2) declining adsorption rate constants in the BML; (3) increasing desorptive fluxes in the BML resulting in (4) enhanced 234Th decay in the BML; (5) decreasing net fluxes of particulate 234Th from the BML to the upper BNL above the BML and to the sediment. Potential consequences for carbon cycling in the water column of the deep ocean are discussed.

Turnewitsch, Robert; Springer, Barbara M.

2001-05-01

35

Benthic Invertebrate Biomonitoring  

NSDL National Science Digital Library

The Environmental Protection Agency's Great Lakes National Program Office (GLNPO), which has sampled for plankton and nutrients since the 1980's, has recently made available results from the 1997 Great Lakes benthic invertebrate biomonitoring study. These data incorporate results from the program's first year of operation; samples were collected at 45 stations during the 1997 summer survey, in nearshore and offshore communities. Results (in summary and table format) include a project introduction (including color maps and figures), site description, substrate characteristics, benthic community description, and distribution of Diporeia hoyi.

1999-01-01

36

Benthic foraminiferal thanatocoenoses from the Cap-Ferret Canyon area (NE Atlantic): A complex interplay between hydro-sedimentary and biological processes  

NASA Astrophysics Data System (ADS)

Benthic foraminiferal thanatocoenoses from the Cap-Ferret Canyon area were studied in the >150-?m fraction of 4-5 cm deep sediment levels, at 13 stations. The shallowest station (151 m depth) is located at the shelf break, close to the canyon head. All other stations are located along two bathymetric transects: seven stations along the canyon axis between 300 and 3000 m depth, and five stations from 300 m to 2000 m depth along the southern flank of the canyon. The comparison between the live (Rose-Bengal-stained) and dead assemblages shows that biological (i.e. population dynamic) and taphonomic processes (i.e. test destruction, transport) generate important discrepancies between live and dead assemblages. An important question is, to what degree post-mortem transport and redeposition of foraminiferal tests contribute to the difference between living and dead assemblages? The composition of the thanatocoenoses (<1% of neritic species) indicates that there is no substantial transport of shells >150 ?m from the inner continental shelf to the Cap-Ferret Canyon axis. However, transport of tests from outer shelf or upper canyon axis towards deeper sites occurs, as indicated by an increase of diversity indices of the dead fauna along the canyon axis. Moreover, some species (e.g., Cassidulina carinata) are observed in the living fauna restricted to the shallow sites, but occur in important amounts in the dead fauna at deeper stations, suggesting that these taxa have been transported from upper canyon stations toward deeper sites. Since Cap-Ferret Canyon is inactive in terms of massive sediment transport (i.e. gravity events), downslope transport of foraminiferal tests probably takes place in nepheloid layers. Downslope transports of foraminiferal tests may create important biases for the utilisation of paleoceanographic proxies using the assemblage characteristics and/or the geochemical composition of selected species. However, the study of dead assemblages along a canyon axis can give important clues about the sedimentary dynamics, especially an idea of the quantity of reworked foraminifera transported through the canyon axis. Along the adjacent flank, such evidence of downslope transport was not observed. Despite taphonomic (test destruction) and biological processes (population dynamics), the live fauna closely resembles the distribution and the composition of the dead assemblage. Therefore, ecological information obtained from the fossil flank samples can be more reliably used to reconstruct paleoenvironmental conditions.

Duros, P.; Jorissen, F. J.; Cesbron, F.; Zaragosi, S.; Schmidt, S.; Metzger, E.; Fontanier, C.

2014-06-01

37

Benthic-Pelagic coupling in the Black Sea northwestern shelf  

NASA Astrophysics Data System (ADS)

A new approach for modeling the benthic compartment in 3D ocean models is applied to analyze the benthic-pelagic coupling in the Black Sea northwestern shelf (BS-NWS) and to review the contribution of sedimentary diagenesis to the BS-NWS biogeochemical cycles (nitrogen, oxygen and carbon). This approach combines an explicit representation of sediment organic matter deposition and resuspension, controlled by the bottom shear stress, and a parameterization of mineralization pathways control by bottom environmental properties. The model reproduces the magnitude and inter-regional and seasonal variability depicted by in situ benthic fluxes estimates obtained by benthic chambers and sediment cores incubations. The model illustrates how this observed variability results from both variable sedimentation rate and variable diagenetic pathways in the sediment layer. Three distinct areas are identified based on the analysis of the simulated seasonal cycle of bottom environmental conditions, benthic-pelagic fluxes and diagenetic processes. These areas extend along a gradient from the land-ocean interface to the open sea boundary and are each characterized by a particular diagenetic pathway, in a way similar as they succeed vertically in a sediment profile. (1) In the hypoxic zone, high remineralization rates lead to a seasonal peak in anoxic diagenesis and under certain conditions to hydrogen sulphide effluxes from the sediment, (2) in the denitrification zone, benthic denitrification rates are maximal and (3) in the oxic zone, where organic matter accumulation are low, oxic diagenesis prevails and seasonality is less marked. This study underlines that representing resuspension and deposition processes in coupled benthic-pelagic models is essential to realistically describe the horizontal distribution of benthic-pelagic fluxes and the export from the shelf region to the deep sea.

Capet, Arthur; Akoumianaki, Ionna; Meysman, Filip; Soetaert, Karline; Grégoire, Marilaure

2014-05-01

38

Hydrophobicity as an Adhesion Mechanism of Benthic Cyanobacteria  

PubMed Central

The capacity of benthic cyanobacteria to adhere to solid substrates was examined in terms of their cell surface properties. By using a biphasic water-hydrocarbon test system, it was demonstrated that benthic cyanobacteria from divergent habitats were all hydrophobic, whereas all the planktonic cyanobacteria tested were hydrophilic. Divalent cations were found more efficient than monovalent cations in effecting the expression of hydrophobicity. Mechanical shearing of the cell surface, as well as chemical removal of the cell wall, demonstrated that the hydrophobicity was confined to the outer surface layers. The hydrophobic sites were distributed along the whole length of the cyanobacterial filament. Hydrophilic hormogonia of benthic cyanobacteria became hydrophobic within 48 h when grown in the light; chloramphenicol, 3(3,4-dichlorophenyl)1,1 dimethylurea, or incubation in the dark prevented this transition. Hydrophobicity of Phormidium filaments was masked in late stationary phase; this effect was removed by gentle washing. Images

Fattom, Ali; Shilo, Moshe

1984-01-01

39

Manganese and Iron Oxidation During Benthic Oxygenic Photosynthesis  

NASA Astrophysics Data System (ADS)

The effect of benthic oxygenic photosynthesis on sediment-water fluxes of manganese and iron was studied for an intertidal sediment. Undisturbed sediments were incubated at an incident surface irradiance of 250 ?E m -2 s -1at 26 °C. Oxygenic photosynthesis was selectively inhibited by adding [3-(3,4-dichloro)-1,1-dimethyl-urea] (DCMU). Benthic fluxes were determined experimentally from the change in manganese and iron concentrations in the overlying water, and were predicted from the pore water concentration gradients at the sediment-water interface assuming molecular diffusion as the transport mechanism. The experimental fluxes of manganese and iron in DCMU-treated cores amounted to -0·84 and -0·59 mmol m -2day -1, respectively, and were directed from the sediment towards the overlying water. In the control cores, showing high rates of benthic oxygenic photosynthesis, the fluxes of manganese and iron were directed towards the sediment, 0·06 and 0·01 mmol m -2day -1, respectively. Mass balances for the 0·1-0·14 cm thick oxic zone, calculated from the experimental fluxes and the predicted fluxes, suggest a minimum areal reoxidation of 0·6 mmol m -2day -1for manganese and of 0·48 mmol m -2day -1for iron in cores showing benthic photosynthesis. The estimated turnover times for dissolved Mn 2+and dissolved Fe 2+in the oxic surface layer during benthic photosynthesis were 0·8 and 0·25 h, respectively. Sediment oxygen microprofiles and the sediment pH profiles suggest that chemical precipitation and reoxidation dominates the retention of manganese and iron during benthic oxygenic photosynthesis in shallow intertidal sediments.

Epping, E. H. G.; Schoemann, V.; de Heij, H.

1998-12-01

40

Determining the Causes of Benthic Condition  

Microsoft Academic Search

A benthic index for northern Gulf of Mexico estuaries has been developed and successfully validated by the Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) in the Louisianian Province. The benthic index is a useful and valid indicator of estuarine condition that is intended to provide environmental managers with a simple tool for assessing the ecological condition of benthic macroinvertebrate

Virginia D. Engle; J. Kevin Summers

1998-01-01

41

Hydrodynamic processes affecting benthic recruitment  

Microsoft Academic Search

Recruitment of animals into initially dcfaunated sites containing simulated stalks of a marsh grass was studied on an intertidal sandflat. Laboratory flume experiments were used to predict the effects of these structures on near-bed flow, the sediment size-frequency composi- tion, and the patterns and rates of benthic recruitment. The effects of simulated stalks on both rates of fluid transport near

JAMES E ECKMAN

1983-01-01

42

Radiotracer estimates of benthic activity effects on trace metal diffusion into mangrove sediments.  

PubMed

Potential influences of the whole benthic organisms' activity (i.e., coupled faunal and microbial effects) on (58)Co, (51)Cr and (65)Zn diffusion into surface mangrove sediment layers (0-6 cm depth) were evaluated in 36 h experiments. Benthic activity indices (BAI) were proposed, calculated as the relative percent difference between untreated sediments and formaldehyde-treated sediments data in relation to untreated sediments data. Benthic activity was estimated as responsible for 32%-44% of total inventories within sediments, being the chromate anion spiked the less affected radiotracer, while (65)Zn was the most sensitive. Benthic activity was quantitatively evidenced as a control on trace metal diffusion into the sediments, contributing to determine the sediment role as a metal sink. This influence can also affect metal potential bioavailability, considering that recently diffused metals can be more readily available to biological uptake. PMID:23174087

Suzuki, K N; Machado, E C; Machado, W; Bellido, L F; Bellido, A V B; Lopes, R T

2013-02-01

43

INDIVIDUAL TURBULENT CELL INTERACTION: BASIS FOR BOUNDARY LAYER ESTABLISHMENT  

EPA Science Inventory

Boundary layers are important in determining the forces on objects in flowing fluids, mixing characteristics, and other phenomena. For example, benthic boundary layers are frequently active resuspension layers that determine bottom turbidity and transniissivity. Traditionally, bo...

44

Do benthic diatoms influence erosion thresholds of coastal subtidal sediments?  

NASA Astrophysics Data System (ADS)

This study reports diatom cell abundance, concentrations of water-soluble and water-insoluble carbohydrates, and concentrations of chlorophyll—a equivalents as indicators of microbial exudates and biomass in the uppermost sediment layer of two coastal sites (19 m water depth: fine sand; 25 m water depth: mud) in Mecklenburg Bight, south-western Baltic Sea. Correlation analysis with experimentally determined erosion thresholds measured in five different periods of a year showed that the sediment water content and the content of water-soluble carbohydrates may indicate erosion thresholds for both sediment types. Erosion thresholds were significantly negatively correlated with sediment water content at the mud site. At both sites, colloidal carbohydrates, as indicators for diatom EPS, showed significantly negative correlations with sediment water content and no correlation with diatom biomass. Therefore, following current interpretation, we argue that micro-biostabilsation effects of benthic microalgae play a minor role in the investigation area. Light is likely to be insufficient for phototrophic growth on the seafloor of the investigated sites most of the year, as indicated by in situ measurements and calculated values of photosynthetically active radiation. We consider lateral transport of benthic diatoms from shallower to deeper areas of Mecklenburg Bight and subsequent to be the mechanism influencing diatom abundance. Exhaustive biofilms are absent at these depths and mass erosion is not likely to be affected by benthic diatoms.

Ziervogel, Kai; Forster, Stefan

2006-01-01

45

Benthic phosphorus regeneration in the Potomac River Estuary  

USGS Publications Warehouse

The flux of dissolved reactive phosphate from Potomac riverine and estuarine sediments is controlled by processes occurring at the water-sediment interface and within surficial sediment. In situ benthic fluxes (0.1 to 2.0 mmoles m-2 day-1) are generally five to ten times higher than calculated diffusive fluxes (0.020 to 0.30 mmoles m-2 day-1). The discrepancy between the two flux estimates is greatest in the transition zone (river mile 50 to 70) and is attributd to macrofaunal irrigation. Both in situ and diffusive fluxes of dissolved reactive phosphate from Potomac tidal river sediments are low while those from anoxic lower estuarine sediments are high. The net accumulation rate of phosphorus in benthic sediment exhibits an inverse pattern. Thus a large fraction of phosphorus is retained by Potomac tidal river sediments, which contain a surficial oxidized layer and oligochaete worms tolerant of low oxygen conditions, and a large fraction of phosphorus is released from anoxic lower estuary sediments. Tidal river sediment pore waters are in equilibrium with amorphous Fe (OH)3 while lower estuary pore waters are significantly undersaturated with respect to this phase. Benthic regeneration of dissolved reactive phosphorus is sufficient to supply all the phosphorus requirements for net primary production in the lower tidal river and transition-zone waters of the Potomac River Estuary. Benthic regeneration supplies approximately 25% as much phosphorus as inputs from sewage treatment plants and 10% of all phosphorus inputs to the tidal Potomac River. When all available point source phosphorus data are put into a steady-state conservation of mass model and reasonable coefficients for uptake of dissolved phosphorus, remineralization of particulate phosphorus, and sedimentation of particulate phosphorus are used in the model, a reasonably accurate simulation of dissolved and particulate phosphorus in the water column is obtained for the summer of 1980. ?? 1982 Dr W. Junk Publishers.

Callender, E.

1982-01-01

46

Assemblages of benthic foraminifers in the White Sea  

NASA Astrophysics Data System (ADS)

Based upon the composition of the dominant species of benthic foraminifers in the bottom sediments sampled at 50 sampling stations in the White Sea, their six assemblages (communities) were defined and mapped. The ranges of these communities depend on the environmental factors determined by the bathymetric, latitudinal, and circum-continental sea zonalities, the sea currents, the bottom upwellings, the continental runoff, the productivity of the waters, and the CaCO3 content in the near-bottom water layers and bottom sediments.

Saidova, Kh. M.

2009-08-01

47

High-frequency acoustic observations of benthic spatial and temporal variability  

NASA Astrophysics Data System (ADS)

A bottom-mounted sonar operating at 40 kHz has been used to measure the variation of bottom acoustic scattering over extended time intervals at two shallow sites as part of the Coastal Benthic Boundary Layer Special Research Project. The acoustic data were analyzed using a correlation method that measures the spatial and temporal dependence of benthic change. The rate of decorrelation was two orders of magnitude more rapid at a sandy site near Panama City, Florida, USA, than at a silty site in Eckernförde Bay, Germany, and both sites were characterized by hot spots or localized regions of activity.

Jackson, Darrell R.; Williams, Kevin L.; Briggs, Kevin B.

1996-09-01

48

Feasibility of remote sensing benthic microalgae  

NASA Technical Reports Server (NTRS)

Results of data analyses from multispectral scanning data are presented. The data was collected in July 1977 for concentration of chlorophyll in benthic microalgae (mainly diatoms) on an estuary mudflat.

Zingmark, R. G.

1979-01-01

49

An In-situ Benthic Respirometer.  

National Technical Information Service (NTIS)

Preliminary field tests of an in-situ benthic respirometer yielded reasonable results which are believed to be a satisfactory measure of the benthal oxygen demands actually occurring in the waters studied. Further tests of this measurement technique under...

O'Connell Weeks

1965-01-01

50

Population of Benthic Macroinvertebrates in Ham's Lake.  

National Technical Information Service (NTIS)

Ham's Lake, Oklahoma, was destratified during summer 1976 by pumping surface water to the bottom. Number of species, diversity, and density of benthic macroinvertebrates were significantly correlated with the concentration of dissolved oxygen, while none ...

J. L. Wilhm D. Barker E. Clay N. McClintock

1977-01-01

51

MESA New York Bight Atlas: Benthic Fauna.  

National Technical Information Service (NTIS)

The benthic macroinvertebrate fauna of New York Bight generally resemble the fauna common to most of the Middle Atlantic Bight and show considerable spatial and temporal heterogeneity in numbers of individuals, species richness, and diversity. The relativ...

J. B. Pearce D. J. Radosh J. V. Caracciolo F. W. Steimle

1981-01-01

52

EPA'S BENTHIC HABITAT DATA FOR YAQUINA ESTUARY  

EPA Science Inventory

Scientists at EPA's National Health and Environmental Effects Research Laboratory, Western Ecology Division (WED) have been studying seafloor (benthic) habitats in Yaquina estuary for several years. Those studies were conducted as parts of several research projects, including: e...

53

Alkanes and Alkenes in Marine Benthic Algae.  

National Technical Information Service (NTIS)

Saturated and olefinic hydrocarbons were determined in additional species of benthic marine algae from the Cape Cod Massachusetts area. The distribution of homologous and isomeric olefins was studied in plants of different age and in morphologically diffe...

W. W. Youngblood M. Blumer

1973-01-01

54

Shallow-water benthic and pelagic metabolism  

Microsoft Academic Search

Pelagic primary production and benthic and pelagic aerobic metabolism were measured monthly at one site in the estuarine plume region of the nearshore continental shelf in the Georgia Bight. Benthic and water-column oxygen uptake were routinely measured and supplemented with seasonal measures of total carbon dioxide flux. Average respiratory quotients were 1.18:1 and 1.02:1 for the benthos and water column,

C. S. Hopkinson

1985-01-01

55

Studies of the Benthic Environment of Twin Lakes, Colorado.  

National Technical Information Service (NTIS)

Three papers discuss ecological aspects of the benthic environment of Twin Lakes, Colo. The first paper discusses the general limnological aspects of Twin Lakes and specific biological aspects of their profundal benthic environment. The second paper inclu...

J. F. LaBounty

1976-01-01

56

Benthic fluxes in San Francisco Bay  

Microsoft Academic Search

Measurements of benthic fluxes have been made on four occasions between February 1980 and February 1981 at a channel station and a shoal station in South San Francisco Bay, using in situ flux chambers. On each occasion replicate measurements of easily measured substances such as radon, oxygen, ammonia, and silica showed a variability (±1a) of 30% or more over distances

Douglas E. Hammond; Christopher Fuller; Dana Harmon; Blayne Hartman; Michael Korosec; Laurence G. Miller; Rebecca Rea; Steven Warren; William Berelson; Stephen W. Hager

1985-01-01

57

Tampa Bay Benthic Monitoring Program Redesign Assessment.  

National Technical Information Service (NTIS)

The Tampa Bay Estuary Program (TBEP) has established a comprehensive and long-term monitoring program to assess benthic habitat and biota conditions in Tampa Bay. This program has collected annual data from 1993 to present, and the data provide a comprehe...

2003-01-01

58

Benthic Invertebrates of the Lower West River  

Microsoft Academic Search

The purpose of this study was to document existing benthic organisms of the lower West River in New Haven and West Haven, Connecticut, in order to enable monitoring of salt marsh restoration. Seventeen sites were sampled between the Chapel Street Bridge and the mouth of the West River during the month of July 1995. All sites contained polychaete worms and

Carmela Cuomo; Gabriele A. Zinn

59

Near-bottom particle flux in the abyssal northeast Atlantic  

Microsoft Academic Search

During a 17-month study at a site on the Porcupine Abyssal Plain of the northeast Atlantic (approx. 48°N20°W), the downward flux of particulate material within and above the benthic nepheloid layer (BNL) was measured using sediment traps 1455m above bottom (mab) (3100m depth) and 90mab (4465m depth). Flux at 90mab is usually higher than the primary flux at 3100m depth,

R. S. Lampitt; P. P. Newton; T. D. Jickells; J. Thomson; P. King

2000-01-01

60

Harnessing the self-harvesting capability of benthic cyanobacteria for use in benthic photobioreactors.  

PubMed

Benthic species of algae and cyanobacteria (i.e., those that grow on surfaces), may provide potential advantages over planktonic species for some commercial-scale biotechnological applications. A multitude of different designs of photobioreactor (PBR) are available for growing planktonic species but to date there has been little research on PBR for benthic algae or cyanobacteria. One notable advantage of some benthic cyanobacterial species is that during their growth cycle they become positively buoyant, detach from the growth surface and form floating mats. This 'self-harvesting' capability could be advantageous in commercial PBRs as it would greatly reduce dewatering costs. In this study we compared the growth rates and efficiency of 'self-harvesting' among three species of benthic cyanobacteria; Phormidium autumnale; Phormidium murrayi and Planktothrix sp.. Phormidium autumnale produced the greatest biomass and formed cohesive mats once detached. Using this strain and an optimised MLA media, a variety of geometries of benthic PBRs (bPBRs) were trialed. The geometry and composition of growth surface had a marked effect on cyanobacterial growth. The highest biomass was achieved in a bPBR comprising of a vertical polyethylene bag with loops of silicone tubing to provide additional growth surfaces. The productivity achieved in this bPBR was a similar order of magnitude as planktonic species, with the additional advantage that towards the end of the exponential phase the bulk of the biomass detached forming a dense mat at the surface of the medium. PMID:21906375

Esson, Diane; Wood, Susanna A; Packer, Michael A

2011-01-01

61

Spectral discrimination of coral reef benthic communities  

Microsoft Academic Search

Effective identification and mapping of coral reef benthic communities using high-spatial and -spectral resolution digital\\u000a imaging spectrometry requires that the different communities are distinguishable by their spectral reflectance characteristics.\\u000a In Kaneohe Bay, Oahu, Hawaii, USA, we collected in situ a total of 247 spectral reflectances of three coral species (Montipora capitata, Porites compressa, Porites lobata), five algal species (Dictyosphaeria cavernosa,

E. J. Hochberg; M. J. Atkinson

2000-01-01

62

State of the benthic ecosystem on western Black Sea shelf in spring 2008  

NASA Astrophysics Data System (ADS)

Since the changes in the economies in the Black Sea countries in the 1990's, the momentarily associated decrease in anthropogenic pressures has put the ecosystem of Black Sea western shelf on a trajectory to recovery. However, the suspected non-linearity of recovery and the ecological instability of the benthic shelf ecosystem in particular became evident in the field surveys supported by the BSERP in 2003, 2004, 2005 and 2006, e.g. in the spread of opportunistic species taking new niches and the re-occurrence of large-scale bottom water hypoxia like in 2001. The temporal dynamics of the recovery (as well as of the decline) may also be tied to climatic effects. The Black Sea is known to respond to north Atlantic oscillation (NAO) forcing and decadal climate changes. The target of the 363th cruise of R/V Poseidon in March 2008 has been to map the current state of the benthic ecosystem in a quasi-winter situation. We assessed: a) the current state of the benthic ecosystem on the north-western shelf; to what degree it recovered during the past decade from its collapse in the 1980's. In this respect, we investigated the role of the seabed as storage media of nutrients from past eutrophication, and the role of the sediments as internal source of nutrients to the pelagic system. We focused on zoo- and phytobenthos distribution, the interaction of benthic biota with the sediment, accumulation of nutrients in the sediment, and the flux of nutrients from the sediments to the water. b) The benthic-pelagic coupling, i.e. how the nutrients nitrogen, phosphorus and silica for algal growth are transported from the seafloor to the sea surface and thus fuel biologic productivity. c) The exchange of water between the shelf and the open Black Sea, and hence the transport of nutrients, i.e. the fertilization of the open Black Sea with nutrients from the shelf. Here, we are presenting results from the spring 2008 survey and compare them to findings from a summer survey in 2006: thermal heating and freshwater input created a double front structure on the western shelf, and intrusion of the Cold Intermediate Layer (CIL) into shelf waters was observed. Surface distribution of dissolved nutrients reflects clear signals of silica and total dissolved nitrogen input from the Danube River. Phosphate appears to have a different source, e.g. benthic and/or from the CIL. The benthic ecosystem remains fragile; diversity indices reflect small recovery, quantities in biomass of both zoo- and phytobenthos indicate ongoing perturbations in nearshore areas. A full recovery of historical beds of Phyllophora is not evident, coverage both in winter and summer is less than 10%, and its role as habitat could be compromised by overgrowth of filamentous algae. The benthic system with an epibenthic community in balance releases less nutrients than a disturbed system without benthic life. Nutrients release from the sediment is lower in winter than in summer. The oxygen penetration depth in the sediment triggers denitrification. A spectacular population development of opportunistic species both in zoo- and phytobenthos was observed. The question remains whether or not those opportunistic species can ensure ecosystem functionality and stability. Our findings will help to identify locations crucial for the functioning for the benthic shelf ecosystem, to define "Good Environmental Status" and help to provide recommendations for Marine protected areas on the western Black Sea shelf. It is hoped that the data will make an important contribution to the information base underpinning the new European Marine Strategy Directive and the Bucharest Convention for the Protection of the Black Sea.

Friedrich, J.; Aleynik, D.; Eulenburg, A.; Kusch, St.; Mee, L. D.; Minicheva, G.; Stevens, T. F.; Teaca, A.; Shapiro, G. I.; Soloviev, D.

2009-04-01

63

A Process for Comparing and Interpreting Differences in Two Benthic Indices in New York Harbor  

EPA Science Inventory

Often when various estuarine benthic indices disagree in their assessments of benthic condition, they are reflecting different aspects of benthic condition. We describe a process to screen indices for associations and, after identifying candidate metrics, to evaluate metrics indi...

64

Benthic Macroinvertebrate Assemblages and Environmental Correlates in Springs of the Ridge and Valley Province  

EPA Science Inventory

Springs are unique features in the landscape that provide important habitat for benthic invertebrates, yet there are few studies characterizing the distribution of benthic macro invertebrates in springs. Benthic macroinvertebrate and water quality data were collected at 35 spring...

65

Benthic Mapping Guidance Document: Lessons Learned from NPS Benthic Mapping Pilot Projects.  

National Technical Information Service (NTIS)

The National Park Service (NPS) has 85 ocean, coastal and Great Lakes parks with more than 11,000 miles of shoreline and 2.5 million acres of marine and estuarine areas across 22 States and four U.S. territories. Benthic habitat data and maps are lacking ...

J. N. Cross L. T. Curdts

2013-01-01

66

The benthic community of the eastern US continental shelf: A literature synopsis of benthic faunal resources  

Microsoft Academic Search

The existing scientific literature on offshore benthic assemblages (OBA) residing along the US East and Gulf of Mexico continental shelf was reviewed. Identification was made of any associations between the dominant OBA and particular sediment types and\\/or bathymetry. Of special interest was the evaluation of reported effects of sand dredge\\/mining activities on the dominant OBA and recognition of data deficiencies.

R. Allen Brooks; Carla N. Purdy; Susan S. Bell; Kenneth J. Sulak

2006-01-01

67

Benthic fluxes in San Francisco Bay  

USGS Publications Warehouse

Measurements of benthic fluxes have been made on four occasions between February 1980 and February 1981 at a channel station and a shoal station in South San Francisco Bay, using in situ flux chambers. On each occasion replicate measurements of easily measured substances such as radon, oxygen, ammonia, and silica showed a variability (??1??) of 30% or more over distances of a few meters to tens of meters, presumably due to spatial heterogeneity in the benthic community. Fluxes of radon were greater at the shoal station than at the channel station because of greater macrofaunal irrigation at the former, but showed little seasonal variability at either station. At both stations fluxes of oxygen, carbon dioxide, ammonia, and silica were largest following the spring bloom. Fluxes measured during different seasons ranged over factors of 2-3, 3, 4-5, and 3-10 (respectively), due to variations in phytoplankton productivity and temperature. Fluxes of oxygen and carbon dioxide were greater at the shoal station than at the channel station because the net phytoplankton productivity is greater there and the organic matter produced must be rapidly incorporated in the sediment column. Fluxes of silica were greater at the shoal station, probably because of the greater irrigation rates there. N + N (nitrate + nitrite) fluxes were variable in magnitude and in sign. Phosphate fluxes were too small to measure accurately. Alkalinity fluxes were similar at the two stations and are attributed primarily to carbonate dissolution at the shoal station and to sulfate reduction at the channel station. The estimated average fluxes into South Bay, based on results from these two stations over the course of a year, are (in mmol m-2 d-1): O2 = -27 ?? 6; TCO2 = 23 ?? 6; Alkalinity = 9 ?? 2; N + N = -0.3 ?? 0.5; NH3 = 1.4 ?? 0.2; PO4 = 0.1 ?? 0.4; Si = 5.6 ?? 1.1. These fluxes are comparable in magnitude to those in other temperate estuaries with similar productivity, although the seasonal variability is smaller, probably because the annual temperature range in San Francisco Bay is smaller. Budgets constructed for South San Francisco Bay show that large fractions of the net annual productivity of carbon (about 90%) and silica (about 65%) are recycled by the benthos. Substantial rates of simultaneous nitrification and denitrification must occur in shoal areas, apparently resulting in conversion to N2 of 55% of the particulate nitrogen reaching the sediments. In shoal areas, benthic fluxes can replace the water column standing stocks of ammonia in 2-6 days and silica in 17-34 days, indicating the importance of benthic fluxes in the maintenance of productivity. Pore water profiles of nutrients and Rn-222 show that macrofaunal irrigation is extremely important in transport of silica, ammonia, and alkalinity. Calculations of benthic fluxes from these profiles are less accurate, but yield results consistent with chamber measurements and indicate that most of the NH3, SiO2, and alkalinity fluxes are sustained by reactions occurring throughout the upper 20-40 cm of the sediment column. In contrast, O2, CO2, and N + N fluxes must be dominated by reactions occurring within the upper one cm of the sediment-water interface. While most data support the statements made above, a few flux measurements are contradictory and demonstrate the complexity of benthic exchange. ?? 1985 Dr W. Junk Publishers.

Hammond, D. E.; Fuller, C.; Harmon, D.; Hartman, B.; Korosec, M.; Miller, L. G.; Rea, R.; Warren, S.; Berelson, W.; Hager, S. W.

1985-01-01

68

A MORE COST-EFFECTIVE EMAP BENTHIC MACROFAUNAL SAMPLING PROTOCOL  

EPA Science Inventory

Benthic macrofaunal sampling protocols in the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) are to collect 30 to 50 random benthic macrofauna [defined as animals retained on a 0.5 mm (East and Gulf Coasts, USA) or a 1.0 mm mesh siev...

69

INDEX OF ESTUARINE BENTHIC INTEGRITY FOR GULF OF MEXICO ESTUARIES  

EPA Science Inventory

A benthic index for northern Gulf of Mexico estuaries has been developed and successfully validated by the Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) in the Louisianian Province. The benthic index is a useful indicator of estuarine condition that provi...

70

BENTHIC NUTRIENT FLUX IN A SMALL ESTUARY IN NORTHWESTERNFLORIDA (USA)  

EPA Science Inventory

Benthic Nutrient Flux in a Small Estuary in Northwestern Florida(USA).Gulf and Caribbean Research 18, 15-25, 2006. Benthic nutrient fluxes of ammonium (NH4+), nitrite/nitrate (NO2-+NO3-), phosphate (PO4-), and dissolved silica (DSi) were measured in Escambia Bay, an estuar...

71

MDE NON-TIDAL BENTHIC MACROINVERTEBRATE MONITORING PROGRAM  

EPA Science Inventory

The Maryland Non-tidal Benthic Macroinvertebrate Monitoring Program provides data on benthic macroinvertebrates for many streams in the state. Through it, an entire network of 100 stations in the nontidal reaches of Marylands Chesapeake Bay Basin are sampled within a two year per...

72

FRESHWATER POTOMAC LONG-TERM BENTHIC MONITORING PROGRAM  

EPA Science Inventory

The Maryland Department of the Environments Freshwater Potomac Long-Term Benthic Monitoring Program provides seasonal information on abundance and composition for the benthic fauna of the freshwater portion of the Potomac River for use in recommendations to State agencies accordi...

73

Towards generalized benthic species recognition and quantification using computer vision  

Microsoft Academic Search

Seabed resource exploitation and conservation efforts are extending to offshore areas where the distribution of benthic epifauna (animals living on the seafloor) is unknown. There is a need to survey these areas to determine how biodiversity is distributed spatially and to evaluate and monitor ecosystem states. Seafloor imagery, collected by underwater vehicles, offer a means for large-scale characterization of benthic

Adam F. Gobi

2010-01-01

74

Towards Generalized Benthic Species Recognition and Quantification Using Computer Vision  

Microsoft Academic Search

Seabed resource exploitation and conservation efforts are extending to offshore areas where the distribution of benthic epifauna (animals living on the seafloor) is unknown. There is a need to survey these areas to determine how biodiversity is distributed spatially and to evaluate and monitor ecosystem states. Seafloor imagery, collected by underwater vehicles, offer a means for large-scale characterization of benthic

Adam F. Gobi

2010-01-01

75

Tolerance of benthic foraminifera (Protista : Sarcodina) to hydrogen sulphide  

Microsoft Academic Search

Benthic foraminifera are dominant members of tb meiofauna, commonly occurring below the anoxic-oxic interface in marine sediments. The absence of oxygen in marine coastal sediments is often correlated with the formation of hydrogen sulphide. In this study the tolerance of benthic foraminifera (from the northwestern Adriatic Sea) to hydrogen sulphide was examined experimentally. Although the foraminiferal assemblage exhibited a high

L. Moodley; BEM Schaub; Van der Zwaan J. G; P. M. J. Herman

1998-01-01

76

Establishing a Benthic Cabled Observatory with ROV Based Cable Deployment  

Microsoft Academic Search

The Monterey Bay Aquarium Research Institute (MBARI) in support of the MBARI Ocean Observation System (MOOS) Science Experiment 2006 (MSE06) has established a benthic cabled observatory. The goal of MSB 06 is to study deep seafloor processes within and adjacent to the outer Monterey Bay Submarine Canyon. At the study site near Shepard Meander, a Benthic Instrument Node (BIN) and

L. E. Bird; D. Graves; G. Massion; M. Chaffey; R. Keaten

2006-01-01

77

Evidence for benthic body size miniaturization in the deep sea  

Microsoft Academic Search

The benthic body size miniaturization hypothesis states that deep-sea communities are dominated by organisms of smaller body size, although some ¢eld studies have produced contradictory results. Using appropriate sample sets, this study tests this hypothesis by contrasting the benthic communities of the Fladen Ground (North Sea, 150 m) and the Faroe ^Shetland Channel (1600 m). Samples were collected for large

Janne I. Kaariainen; Brian J. Bett

2006-01-01

78

Assessing benthic ecological status in stressed Liaodong Bay (China) with AMBI and M-AMBI  

NASA Astrophysics Data System (ADS)

Rapid economic development in recent decades has resulted in environmental degradation of Liaodong Bay, North China, where eutrophication is becoming more evident because of excess nutrients inputs. To assess the benthic ecological status in Liaodong Bay, AZTI's Marine Biotic Index (AMBI) and multivariate-AMBI (M-AMBI) were applied using both benthic macroinvertebrate density and biomass data collected from Liaodong Bay in July 2007. This first application of AMBI and M-AMBI in Liaodong Bay showed that the nearshore areas of the bay, especially near river estuaries, were severely disturbed, with a clear gradient of disturbance decreasing seaward. Ecological status assessed from density and biomass data was quite similar. Significant relationships were also found between both indices and environmental variables in Liaodong Bay. Moreover, the spatial distributions of both AMBI and M-AMBI matched those of plotted eutrophication indices (EI) in the surface water layer, and significant linear correlations were found between both benthic indices and EI. In general, both AMBI and M-AMBI worked well on assessing the ecological status of Liaodong Bay under eutrophication stress due to excess nutrients inputs.

Cai, Wenqian; Meng, Wei; Zhu, Yanzhong; Zhou, Juan; Liu, Lusan

2013-05-01

79

Scavenging rates and particle characteristics in and near the Lacaze-Duthiers submarine canyon, northwest Mediterranean  

NASA Astrophysics Data System (ADS)

To better understand the particle exchange processes across the Pyrenean continental margin, sampling was conducted in 1994 and 1995 at stations in and near the Lacaze-Duthiers canyon in the northwestern Mediterranean. Moored current meters provide evidence of water transport along the canyon axis (cross-slope) and along-slope with the prevailing regional circulation. Turbidity measurements show surficial nepheloid layers (SNL) roughly coincident with fluorescence resulting from biological productivity. Recurrent benthic nepheloid layers (BNL) (as observed at a station on the outer-shelf) are advected into the canyon, forming intermediate nepheloid layers (INL). The mineralogical composition of suspended particles collected at stations on the outer-shelf and head of the canyon indicates an illite and chlorite-rich assemblage with minor magnesian calcite, indicative of materials resuspended from the adjacent shelf sediments. The mineralogy of suspended particles at stations farther in the canyon shows the presence of material derived from the Rhone River and likely transported along-slope by the Liguro-Provençal current. Measurements of the short-lived naturally occurring radionuclide 234Th show that it is actively scavenged from the nepheloid layers. Within the canyon, scavenging (as indicated by the mean residence time of dissolved Th with respect to uptake onto particles) is similar in both the SNL (30-58 d) and INL (25-85 d). Residence times of particulate Th with respect to removal from the water column follow the same trends, with values of about 5 d (1994) and 12-19 d (1995) in the SNL and 11-20 d (1994) and 15-23 d (1995) in the INL. This research suggests that while the Lacaze-Duthiers canyon serves as a conduit through which sediment associated with nepheloid layers detached from the shelf are transported, the rates of scavenging of Th in the canyon are not appreciably different from those on the adjacent shelf.

Frignani, M.; Courp, T.; Cochran, J. K.; Hirschberg, D.; Vitoria i Codina, L.

2002-10-01

80

Prediction of Benthic Impact for Salmon Net-Pens Based on the Balance of Benthic Oxygen Supply and Demand  

Microsoft Academic Search

The ratio between oxygen supply and oxygen demand was examined as a predictor of benthic response to organic enrichment caused by salmon net-pen aquaculture. Oxygen supply to the benthos was calculated based on Fickian diffusion and near-bottom flow velocities. A strong linear correlation was found between measured carbon sedimentation rates and rates of benthic metabolism. This relationship allowed an estimation

R. H. Findlay; Les Watling

1997-01-01

81

Generalized analytical model for benthic water flux forced by surface gravity waves  

USGS Publications Warehouse

A generalized analytical model for benthic water flux forced by linear surface gravity waves over a series of layered hydrogeologic units is developed by adapting a previous solution for a hydrogeologic unit with an infinite thickness (Case I) to a unit with a finite thickness (Case II) and to a dual-unit system (Case III). The model compares favorably with laboratory observations. The amplitude of wave-forced benthic water flux is shown to be directly proportional to the amplitude of the wave, the permeability of the hydrogeologic unit, and the wave number and inversely proportional to the kinematic viscosity of water. A dimensionless amplitude parameter is introduced and shown to reach a maximum where the product of water depth and the wave number is 1.2. Submarine groundwater discharge (SGD) is a benthic water discharge flux to a marine water body. The Case I model estimates an 11.5-cm/d SGD forced by a wave with a 1 s period and 5-cm amplitude in water that is 0.5-m deep. As this wave propagates into a region with a 0.3-m-thick hydrogeologic unit, with a no-flow bottom boundary, the Case II model estimates a 9.7-cm/d wave-forced SGD. As this wave propagates into a region with a 0.2-m-thick hydrogeologic unit over an infinitely thick, more permeable unit, the Case III quasi-confined model estimates a 15.7-cm/d wave-forced SGD. The quasi-confined model has benthic constituent flux implications in coral reef, karst, and clastic regions. Waves may undermine tracer and seepage meter estimates of SGD at some locations. Copyright 2009 by the American Geophysical Union.

King, J. N.; Mehta, A. J.; Dean, R. G.

2009-01-01

82

Benthic response to the sedimentation of particulate organic matter at the BIOTRANS station, 47°N, 20°W  

NASA Astrophysics Data System (ADS)

The benthic response to the sedimentation of particulate organic matter (POM) was investigated during 1985-1990 at 47°N, 20°W (BIOTRANS station). The first noticeable annual sedimentation of phytodetritus, as indicated by chlorophyll a concentrations in the sediment, occurred as early as late April-early May. Maximum amounts were found in June-July. Two different sedimentation pulses to the sea bed are described that demonstrate interannual variation: the occurrence of salp faecal pellets early in the year 1988 and the massive fall out of a plankton bloom in summer 1986, which deposited approximately 15 mmol C m -2. The benthic reaction to POM pulses was quite diverse. The mega-, macro- and meiobenthos showed no change in biomass, whereas bacterial biomass doubled between March and July. This corresponds to a seasonal maximum of total adenylate biomass. The relative abundance of Foraminifera among the meiobenthos increased during the summer. Benthic activity (ATP, ratio ATP/ETSA), as well as in situ sediment community oxygen consumption rates (SCOC), showed distinct seasonal maxima in July-August of 0.75 mmol C m -2 day -1. Based on SCOC and the carbon demand for growth, a benthic carbon consumption of 0.94 mmol C m -2 day -1 was estimated. This represents about 1.1% of spring bloom primary production and 9.6% of the export flux beneath the 150 m layer, measured during the North Atlantic Bloom Experiment. Bacteria and protozoans colonizing the epibenthic phytodetrital layer were responsible for 60-80% of the seasonal increase in SCOC. The strong reaction of the smaller benthic size groups (bacteria, protozoans) to POM pulses stresses their particular importance for sediment-water interface flux rates.

Pfannkuche, O.

83

Diel variability in seawater pH relates to calcification and benthic community structure on coral reefs.  

PubMed

Community structure and assembly are determined in part by environmental heterogeneity. While reef-building corals respond negatively to warming (i.e. bleaching events) and ocean acidification (OA), the extent of present-day natural variability in pH on shallow reefs and ecological consequences for benthic assemblages is unknown. We documented high resolution temporal patterns in temperature and pH from three reefs in the central Pacific and examined how these data relate to community development and net accretion rates of early successional benthic organisms. These reefs experienced substantial diel fluctuations in temperature (0.78°C) and pH (>0.2) similar to the magnitude of 'warming' and 'acidification' expected over the next century. Where daily pH within the benthic boundary layer failed to exceed pelagic climatological seasonal lows, net accretion was slower and fleshy, non-calcifying benthic organisms dominated space. Thus, key aspects of coral reef ecosystem structure and function are presently related to natural diurnal variability in pH. PMID:22952785

Price, Nichole N; Martz, Todd R; Brainard, Russell E; Smith, Jennifer E

2012-01-01

84

Diel Variability in Seawater pH Relates to Calcification and Benthic Community Structure on Coral Reefs  

PubMed Central

Community structure and assembly are determined in part by environmental heterogeneity. While reef-building corals respond negatively to warming (i.e. bleaching events) and ocean acidification (OA), the extent of present-day natural variability in pH on shallow reefs and ecological consequences for benthic assemblages is unknown. We documented high resolution temporal patterns in temperature and pH from three reefs in the central Pacific and examined how these data relate to community development and net accretion rates of early successional benthic organisms. These reefs experienced substantial diel fluctuations in temperature (0.78°C) and pH (>0.2) similar to the magnitude of ‘warming’ and ‘acidification’ expected over the next century. Where daily pH within the benthic boundary layer failed to exceed pelagic climatological seasonal lows, net accretion was slower and fleshy, non-calcifying benthic organisms dominated space. Thus, key aspects of coral reef ecosystem structure and function are presently related to natural diurnal variability in pH.

Martz, Todd R.; Brainard, Russell E.

2012-01-01

85

Bite profiles of some benthic grab samplers  

NASA Astrophysics Data System (ADS)

The bite profiles of six 0·1 m 2 benthic grab samplers were reconstructed from video recordings of closure. The Petersen and the chain-rigged van Veen grabs both took shallow bites of variable profile; the Day and the Smith-McIntyre grabs both took fairly deep and consistent bites but were prevented by their frames from using their momentum on landing to increase penetration; two designs of warp-rigged van Veen grab both took deep, parallel sided bites. The long arm, warp-rigged van Veen was the only grab to collect sediment from a depth of at least 50 mm over the entire 0·1 m 2 sampled. A bucket shape, designed to optimise penetration and minimise upwards movement on closure, is suggested.

Riddle, Martin J.

1989-09-01

86

Hadal disturbance in the Japan Trench induced by the 2011 Tohoku-Oki Earthquake  

PubMed Central

In situ video observations and sediment core samplings were performed at two hadal sites in the Japan Trench on July, 2011, four months after the Tohoku–Oki earthquake. Video recordings documented dense nepheloid layers extending ~30–50?m above the sea bed. At the trench axis, benthic macrofauna was absent and dead organisms along with turbid downslope current were observed. The top 31?cm of sediment in the trench axis revealed three recent depositions events characterized by elevated 137Cs levels and alternating sediment densities. At 4.9?km seaward from the trench axis, little deposition was observed but the surface sediment contained 134Cs from the Fukushima Dai–ichi nuclear disaster. We argue that diatom blooms observed by remote sensing facilitated rapid deposition of 134Cs to hadal environment and the aftershocks induced successive sediment disturbances and maintained dense nepheloid layers in the trench even four months after the mainshock.

Oguri, Kazumasa; Kawamura, Kiichiro; Sakaguchi, Arito; Toyofuku, Takashi; Kasaya, Takafumi; Murayama, Masafumi; Fujikura, Katsunori; Glud, Ronnie N.; Kitazato, Hiroshi

2013-01-01

87

Hadal disturbance in the Japan Trench induced by the 2011 Tohoku-Oki earthquake.  

PubMed

In situ video observations and sediment core samplings were performed at two hadal sites in the Japan Trench on July, 2011, four months after the Tohoku-Oki earthquake. Video recordings documented dense nepheloid layers extending ~30-50 m above the sea bed. At the trench axis, benthic macrofauna was absent and dead organisms along with turbid downslope current were observed. The top 31 cm of sediment in the trench axis revealed three recent depositions events characterized by elevated (137)Cs levels and alternating sediment densities. At 4.9 km seaward from the trench axis, little deposition was observed but the surface sediment contained (134)Cs from the Fukushima Dai-ichi nuclear disaster. We argue that diatom blooms observed by remote sensing facilitated rapid deposition of (134)Cs to hadal environment and the aftershocks induced successive sediment disturbances and maintained dense nepheloid layers in the trench even four months after the mainshock. PMID:23715086

Oguri, Kazumasa; Kawamura, Kiichiro; Sakaguchi, Arito; Toyofuku, Takashi; Kasaya, Takafumi; Murayama, Masafumi; Fujikura, Katsunori; Glud, Ronnie N; Kitazato, Hiroshi

2013-01-01

88

BENTHIC MACROFAUNA-HABITAT ASSOCIATIONS IN WILLAPA BAY, WASHINGTON, USA  

EPA Science Inventory

Estuary-wide benthic macrofauna-habitat associations in Willapa Bay, Washington, United States, were determined for 4 habitats (eelgrass [Zostera marina], Atlantic cordgrass [Spartina alterniflora], mud shrimp [Upogebia pugettensis], ghost shrimp [Neotrypaea californiensis]) in 1...

89

BENTHIC MACROFAUNA-HABITAT RELATIONSHIPS IN WILLAPA BAY, WA  

EPA Science Inventory

Benthic macrofauna-habitat relationships were determined estuary-wide in Willapa Bay, WA for four intertidal habitats ((1) eelgrass, Zostera marina, (2) Atlantic cordgrass, Spartina alterniflora, (3) ghost shrimp, Neotrypaea californiensis, (4) mud shrimp, Upogebia pugettensis) i...

90

DECLINE IN LAKE ONTARIO POPULATIONS OF BENTHIC MACROINVERTEBRATES  

EPA Science Inventory

Surveys of benthic macroinvertebrates conducted in Lake Ontario during 1994 and 1997 revealed declines in populations of three major groups of organisms: oligochaetes, sphariids, and Diporeia spp. (Amphipoda), with the most drastic reductions occurring in the latter. Based on phy...

91

Ecological Characterization of the Benthic Community of Lake Pontchartrain, Louisiana.  

National Technical Information Service (NTIS)

We have examined and documented several changes in the benthic community structure of Lake Pontchartrain. The change from dominance by large Rangia cuneata to dominance by very small hydrobiid gastropods, for instance, has occurred since the last large-sc...

J. P. Sikora W. B. Sikora

1982-01-01

92

Benthic Faunal Composition along Princess Astrid Coast, East Antarctica  

Microsoft Academic Search

species, representing 9 major benthic faunal groups encountered at 200 m depth off the Princess Astrid coast (Lat. 69°54'S; Long. 12°49'E) in the Eastern Antarctica, are described here. Estimated benthic biomass was 68 gm -2 . Echinoderms (35%) followed by sponges (22%), molluscs (15%), ascidians (8%), coelenterates (5%), crustaceans (5%), bryozoans (4%) and annelids (3%) were the major faunal taxa.

R. A. SREEPADA; V. JAYASREE; A. H. PARULEKAR

93

Benthic Metabolism as an Indicator of Stream Ecosystem Health  

Microsoft Academic Search

We tested direct and indirect measures of benthic metabolism as indicators of stream ecosystem health across a known agricultural\\u000a land-use disturbance gradient in southeast Queensland, Australia. Gross primary production (GPP) and respiration (R24) in benthic chambers in cobble and sediment habitats, algal biomass (as chlorophyll a) from cobbles and sediment cores, algal biomass accrual on artificial substrates and stable carbon isotope

Christine S. Fellows; Joanne E. Clapcott; James W. Udy; Stuart E. Bunn; Bronwyn D. Harch; Michael J. Smith; Peter M. Davies

2006-01-01

94

Benthic fluxes of nutrients in the northwestern Black Sea  

Microsoft Academic Search

The exchange of O2, NH4+, Si(OH)4, ortho-phosphate, Fe2+, Mn2+ and H2S between the sediment and the overlying water (benthic flux) was determined at 6 locations on the northwestern shelf of the Black Sea using an in situ benthic lander. Oxygen consumption by the sediments ranged from 0 to 33 mmol m?2 d?1 depending mostly on the initial oxygen concentration in

Gabriela Friedl; Christian Dinkel; Bernhard Wehrli

1998-01-01

95

Dispersal, survival and delayed growth of benthic foraminiferal propagules  

Microsoft Academic Search

New data support our previously published propagule dispersal hypothesis and show that propagules of some benthic foraminiferal species can survive for two years before growth commences. Following exposure to simulated shallow-water conditions, shallow-water species of benthic foraminifera appeared and grew in large numbers (commonly >100 ind\\/12ml sediment) in the <32µm-size sediment fraction collected from 320m water depth in the Skagerrak

Elisabeth Alve; Susan T. Goldstein

2010-01-01

96

Environmental impacts on the benthic foraminiferal fauna in nearshore ecosystems  

Microsoft Academic Search

This review presents data on how natural and anthropogenic factors affect species composition, abundance, and test morphology\\u000a of benthic foraminifera of the world oceans. Major emphasis is placed on high sensitivity of foraminifera to changes in the\\u000a state of the environment, particularly in nearshore zones under anthropogenic impact. It is shown that benthic foraminifera\\u000a can provide indicators of environmental conditions

T. S. Tarasova

2006-01-01

97

Organic matter and benthic metabolism in Lake Illawarra, Australia  

Microsoft Academic Search

Carbon and nitrogen contents (total organic carbon and total nitrogen), chlorophyll-a concentrations in surface sediments and benthic sediment water fluxes of oxygen and carbon dioxide were investigated at five stations in Lake Illawarra (Australia) to compare the sources\\/quality of sedimentary organic matter and the characteristics of diagenesis and benthic biogeochemical processes for different primary producers (e.g., seagrass, microphytobenthos and macroalgae)

Wenchuan Qu; R. J. Morrison; R. J. West; Chenwei Su

2006-01-01

98

Organic matter and benthic metabolism in Lake Illawarra, Australia  

Microsoft Academic Search

Carbon and nitrogen contents (total organic carbon and total nitrogen), chlorophyll-a concentrations in surface sediments and benthic sediment–water fluxes of oxygen and carbon dioxide were investigated at five stations in Lake Illawarra (Australia) to compare the sources\\/quality of sedimentary organic matter and the characteristics of diagenesis and benthic biogeochemical processes for different primary producers (e.g., seagrass, microphytobenthos and macroalgae) and\\/or

Wenchuan Qu; R. J. Morrison; R. J. West; Chenwei Su

2006-01-01

99

The role of sediments on the Bering Sea shelf N cycle: Insights from measurements of benthic denitrification and benthic DIN fluxes  

NASA Astrophysics Data System (ADS)

Continental shelves are hotspots for sedimentary denitrification, and the loss of N through denitrification can limit primary production in ecosystems. Spatial and seasonal trends in sedimentary denitrification and benthic nutrient fluxes are poorly characterized in the highly productive Bering Sea shelf ecosystem. Through the Bering Sea Ecosystem Study (BEST) program, we measured benthic fluxes of N2 and dissolved inorganic nitrogen (DIN: NH4++NO2-+NO3-), the extent of coupled sedimentary nitrification/denitrification, and the water column DIN deficit relative to phosphate, as indicated by a modified N* parameter (N**), on the Bering Sea shelf in the spring and summer 2009-2010. We found that sedimentary denitrification is widespread over the shelf, it is fueled mostly through coupled nitrification/denitrification, the net balance of sedimentary DIN flux is near zero over the shelf, and that the water column DIN deficit varies widely according to season and year. In the summer, N** in the surface layer appeared to be strongly affected by non-Redfieldian uptake of inorganic nutrients by phytoplankton in the spring bloom; in the winter, N** was strongly affected by sedimentary denitrification. Our findings indicate that the estimate of total N loss in Bering Sea shelf sediments should be revised upwards by at least 50% to 5.2-6.2 Tg N y-1. In addition, sediments are not a significant source of remineralized N for primary production over the shelf; hence sedimentary denitrification exacerbates N-limitation of the ecosystem.

Horak, Rachel E. A.; Whitney, Heather; Shull, David H.; Mordy, Calvin W.; Devol, Allan H.

2013-10-01

100

Lake Malawi cichlid evolution along a benthic/limnetic axis  

PubMed Central

Divergence along a benthic to limnetic habitat axis is ubiquitous in aquatic systems. However, this type of habitat divergence has largely been examined in low diversity, high latitude lake systems. In this study, we examined the importance of benthic and limnetic divergence within the incredibly species-rich radiation of Lake Malawi cichlid fishes. Using novel phylogenetic reconstructions, we provided a series of hypotheses regarding the evolutionary relationships among 24 benthic and limnetic species that suggests divergence along this axis has occurred multiple times within Lake Malawi cichlids. Because pectoral fin morphology is often associated with divergence along this habitat axis in other fish groups, we investigated divergence in pectoral fin muscles in these benthic and limnetic cichlid species. We showed that the eight pectoral fin muscles and fin area generally tended to evolve in a tightly correlated manner in the Lake Malawi cichlids. Additionally, we found that larger pectoral fin muscles are strongly associated with the independent evolution of the benthic feeding habit across this group of fish. Evolutionary specialization along a benthic/limnetic axis has occurred multiple times within this tropical lake radiation and has produced repeated convergent matching between exploitation of water column habitats and locomotory morphology.

Hulsey, C D; Roberts, R J; Loh, Y-H E; Rupp, M F; Streelman, J T

2013-01-01

101

Phototoxicity of TiO? nanoparticles to a freshwater benthic amphipod: are benthic systems at risk?  

PubMed

This study investigated phototoxicity of TiO? nanoparticles (nano-TiO?) to a freshwater benthic amphipod (Hyalella azteca) using 48-h and 96-h bioassays. Thorough monitoring of particle interactions with exposure media (Lake Superior water, LSW) and the surface of organisms was performed using dynamic light scattering, UV/Vis spectroscopy, and Scanning Electron Microscopy. Large agglomeration and sedimentation (>77%) in LSW was observed after 0.5h. A simulated solar radiation (SSR)-favored surface attachment of nanoparticles was observed, indicating enhanced phototoxicity with the increased attachment. A 96-h median lethal concentration (LC50) of 29.9 mg/L in H. azteca was calculated, with a daily 4-h UV exposure of 2.2 W/m(2). Phototoxicity of nano-TiO? under SSR had a 21-fold increase as compared to that under ambient laboratory light. This phototoxicity was also dependent on UV dose, with calculated LC50s around 22.9 (95% CI, 20.5-23.3)Wh/m(2) when exposed to 20 mg/L nano-TiO?. Also, H. azteca exhibited negative phototaxis in the presence of shelters, indicating that other factors might play a role in environmental systems. Finally, the environmental implications of nano-TiO? to benthic organisms were illustrated, emphasizing the importance of various environmental factors in the ultimate phototoxicity. This increased phototoxicity and its complex interactions with various environmental factors suggest further investigations are needed for future risk assessment of photoactive nanomaterials to benthic organisms. PMID:23973546

Li, Shibin; Wallis, Lindsay K; Ma, Hongbo; Diamond, Stephen A

2014-01-01

102

Parameterisation of clastic sediments including benthic structures  

NASA Astrophysics Data System (ADS)

The sediment transport processes in the south-western Baltic Sea are predicted by means of a numerical model in the project DYNAS. There are two sediment parameters that influence the results of modelling remarkably: critical shear stress velocity and bottom roughness. This paper presents the way how to parameterise these factors and extrapolate them into the investigation area. The critical shear stress velocity is parameterised basing on grain size data, combining approximations after Hjulström [Hjulström, F., 1935: Studies in the morphological activity of rivers as illustrated by the river Fyris. Geological Institution of University of Uppsala: Bulletin (25): 221-528.], Shields [Shields, A., 1936: Anwendung der Ähnlichkeits-Mechanik und der Turbulenzforschung auf die Geschiebebewegung. Mitteilungen der Preussischen Versuchsanstalt für Wasserbau und Schiffahrt (26): 26 pp.] and Bohling [Bohling, B., 2003: Untersuchungen zur Mobilität natürlicher und anthropogener Sedimente in der Mecklenburger Bucht. unpublished doctoral thesis, Mathematisch-Naturwissenschaftliche Fakultät, Ernst-Moritz-Arndt-Universität Greifswald/Germany, 156 pp.]. The roughness length, in the case of absence of macro zoo-benthos and their structures, is parameterised basing on grain size too employing Soulsby [Soulsby, R.L., 1997: Dynamics of Marine Sands: a Manual for Practical Applications. London, Thomas Telford Publications. 249 pp.], Nielsen [Nielsen, P., 1983: Analytical determination of nearshore wave height variation due to refraction shoaling and friction. Coastal Engineering 7, 233-251.] and Yalin [Yalin, M.S., 1977: Mechanics of Sediment Transport. Pergamon Press, New York. 298 pp.]. No equivalent simple parameterisations for biologically caused bed roughness exist. Here, findings of Friedrichs [Friedrichs, M., 2004: Flow-induced effects of macro zoo-benthic structures on the near-bed sediment transport. Dissertation, Universität Rostock, 80 S.] and estimations by the DYNAS biologists group were combined in order to derive roughness lengths from abundance measurements of four previously selected key species which represent the originators of the dominating benthic structures at the sea floor in the south-western Baltic Sea. Critical shear stress velocity and bed roughness are known at few sample sites only. They were extrapolated into the larger investigation area using a proxy-target concept. The mean near bottom milieu (bathymetry, median grain size, salinity, oxygen) which was derived using results from numerical modelling serves as the proxy. Since the milieu parameters are measured at the sampling sites for which the target parameters have been determined, a combined hierarchical and supervised classification was employed to transfer the local knowledge into the unknown investigation area.

Bobertz, B.; Harff, J.; Bohling, B.

2009-02-01

103

The continental shelf benthic iron flux and its isotope composition  

NASA Astrophysics Data System (ADS)

Benthic iron fluxes from sites along the Oregon-California continental shelf determined using in situ benthic chambers, range from less than 10 ?mol m -2 d -1 to values in excess of ˜300 ?mol m -2 d -1. These fluxes are generally greater than previously published iron fluxes for continental shelves contiguous with the open ocean (as opposed to marginal seas, bays, or estuaries) with the highest fluxes measured in the regions around the high-sediment discharge Eel River and the Umpqua River. These benthic iron fluxes do not covary with organic carbon oxidation rates in any systematic fashion, but rather seem to respond to variations in bottom water oxygen and benthic oxygen demand. We hypothesize that the highest rates of benthic iron efflux are driven, in part, by the greater availability of reactive iron deposited along these river systems as compared to other more typical continental margin settings. Bioirrigation likely plays an important role in the benthic Fe flux in these systems as well. However, the influence of bottom water oxygen concentrations on the iron flux is significant, and there appears to be a threshold in dissolved oxygen (˜60-80 ?M), below which sediment-ocean iron exchange is enhanced. The isotope composition of this shelf-derived benthic iron is enriched in the lighter isotopes, and appears to change by ˜3‰ (? 56Fe) during the course of a benthic chamber experiment with a mean isotope composition of -2.7 ± 1.1‰ (2 SD, n = 9) by the end of the experiment. This average value is slightly heavier than those from two high benthic Fe flux restricted basins from the California Borderland region where ? 56Fe is -3.4 ± 0.4‰ (2 SD, n = 3). These light iron isotope compositions support previous ideas, based on sediment porewater analyses, suggesting that sedimentary iron reduction fractionates iron isotopes and produces an isotopically light iron pool that is transferred to the ocean water column. In sum, our data suggest that continental shelves may export a higher efflux of iron than previously hypothesized, with the likelihood that along river-dominated margins, the benthic iron flux could well be orders of magnitude larger than non-river dominated shelves. The close proximity of the continental shelf benthos to the productive surface ocean means that this flux is likely to be essential for maintaining ecosystem micronutrient supply.

Severmann, Silke; McManus, James; Berelson, William M.; Hammond, Douglas E.

2010-07-01

104

Miocene benthic foraminiferal isotope records: A synthesis  

USGS Publications Warehouse

18O 16O and 13C 12C ratios of Miocene benthic foraminifera from a number of Atlantic, Pacific and Indian Ocean DSDP sites (71, 77B, 206, 208, 238, 279, 289, 296, 329, 357 and 366A) have been compiled. These provide a rather detailed history of Miocene deep water especially in the Pacific Ocean. Bottom-water temperatures rose during the early Miocene and then declined rapidly during the middle Miocene. This decline was accompanied by an increase in Antarctic glaciation. Late Miocene bottom temperatures and Antarctic ice volumes are inferred to be similar to today's, but exhibited some fluctuation. The early Miocene ocean was less thermally stratified at intermediate and abyssal depths while the late Miocene deep ocean had a thermal structure generally similar to the modern ocean. Foraminiferal carbon isotope ratios at most of the sites varied quasi-sympathetically throughout the Miocene. These variations must reflect comparable variations in the mean 13C 12C of marine HCO3-. However, the causes of such variations are not yet clear. ?? 1981.

Savin, S. M.; Douglas, R. G.; Keller, G.; Killingley, J. S.; Shaughnessy, L.; Sommer, M. A.; Vincent, E.; Woodruff, F.

1981-01-01

105

Benthic macroinvertebrates' vertical distribution in the Tagus estuary (Portugal): The influence of tidal cycle  

NASA Astrophysics Data System (ADS)

In this work we evaluated the vertical distribution pattern of benthic infauna during the tidal cycle at one of the most important mudflats of the Tagus estuary. Samples were collected hourly during 24 h periods at four complete tidal cycles, using a corer specifically designed for the study purpose that allowed easy and effective separation of 15 different sediment layers. A particular case of general linear models, the hurdle model, was used to analyse data sets. We found that different species have different distribution and abundance according to sediment layers. Results showed that individuals tend to go deeper into sediment with a lower water column height and that these migrations are more visible during spring tides.

Cardoso, Inês; Granadeiro, José Pedro; Cabral, Henrique

2010-03-01

106

Temporal variation of diatom benthic propagules in a monsoon-influenced tropical estuary  

NASA Astrophysics Data System (ADS)

Temporal variations in the diatom benthic propagule (DBP) community and their role in the phytoplankton community in a monsoon-affected tropical estuary, Zuari estuary, Goa (India) are presented. The DBP from the sediments was enumerated using an extinction dilution method (most probable number method), which allows estimation of resting stages through examination of germinated vegetative cells in culture. The DBP community was dominated by planktonic species belonging to the genera Skeletonema, Fragilariopsis, Thalassiosira, and Chaetoceros. Benthic propagules (BPs) of Skeletonema costatum and Fragilariopsis sp. were dominant throughout the year. Between these two species, only S. costatum showed a linear relationship between the BP and planktonic cells, indicating that this species is particularly important in coupling of pelagic and benthic ecosystems. During the onset and restart of monsoon after an intermittent break, water column was stratified, with a low-salinity layer arising from riverine discharge and precipitation at the surface and relatively cold, saline, low-oxygen waters at the bottom. Stratification favored blooming of S. costatum and Fragilariopsis sp. in nutrient-rich surface and bottom waters, respectively. The decline in these blooms ensuing nitrate depletion and salinity change resulted in an increased abundance of BP. Chaetoceros bloom was observed during the monsoon break as well as during non-monsoon period and on both the occasions the decline in bloom was coupled with freshwater discharge. During the non-monsoon season, Thalassiosira blooms were encountered subsequent to high nitrate inputs. These findings suggest that in such shallow tropical regions, physical processes during monsoon (freshwater discharge) and non-monsoon seasons (currents, waves and tides) cause resuspension of diatom BP. Since light is not a limiting factor for germination in such regions, the blooming of resuspended BP depends on nutrient availability.

Patil, Jagadish S.; Anil, Arga Chandrashekar

2008-10-01

107

Benthic Macroinvertebrate Assemblages in the Near Coastal Zone of Lake Erie  

EPA Science Inventory

Benthic macroinvertebrate assemblages have been used as indicators of ecological condition because their responses integrate localized environmental conditions of the sediments and overlying water. Assemblages of benthic invertebrates in the near coastal region are of particular...

108

Importance of Physical Scaling Factors to Benthic Marine Invertebrate Recolonization of Laboratory Microcosms.  

National Technical Information Service (NTIS)

Five laboratory studies of benthic macroinvertebrate recolonization were conducted for six-wk periods to evaluate the effects of physical scaling factors (i.e., microcosm size, seawater flow rates and sediment depth) on benthic community structure. Design...

D. A. Flemer J. R. Clark R. S. Stanley C. M. Bundrick G. R. Plaia

1993-01-01

109

Spatial Patterns of Subtidal Benthic Invertebrates and Environmental Factors in the Nearshore Gulf of Maine  

EPA Science Inventory

The spatial patterns of subtidal benthic invertebrates and physical-chemical variables in the nearshore Gulf of Maine (Acadian Biogeographic Province) were studied to provide information needed to calibrate benthic indices of environmental condition, determine physical-chemical f...

110

Eddy-Kinetic Energy, Benthic Storms and Sediment Redistribution in the Argentine Basin.  

National Technical Information Service (NTIS)

To establish and define relationships between benthic storms (periods of intense currents and bottom resuspension) sediment distribution patterns, and the intensity of eddy kinetic energy observed in surface or bottom waters. A correlation between benthic...

M. J. Richardson W. D. Gardner

1989-01-01

111

Application of multiple index development approaches to benthic invertebrate data from the Virginian Biogeographic Province  

EPA Science Inventory

Benthic invertebrate indices have commonly been utilized to assess benthic invertebrate communities. These indices have been constructed using different techniques, but have shown different levels of application success. For example, the EMAP Virginian Province Index did not pe...

112

Global environmental predictors of benthic marine biogeographic structure  

PubMed Central

Analyses of how environmental factors influence the biogeographic structure of biotas are essential for understanding the processes underlying global diversity patterns and for predicting large-scale biotic responses to global change. Here we show that the large-scale geographic structure of shallow-marine benthic faunas, defined by existing biogeographic schemes, can be predicted with 89–100% accuracy by a few readily available oceanographic variables; temperature alone can predict 53–99% of the present-day structure along coastlines. The same set of variables is also strongly correlated with spatial changes in species compositions of bivalves, a major component of the benthic marine biota, at the 1° grid-cell resolution. These analyses demonstrate the central role of coastal oceanography in structuring benthic marine biogeography and suggest that a few environmental variables may be sufficient to model the response of marine biogeographic structure to past and future changes in climate.

Belanger, Christina L.; Jablonski, David; Roy, Kaustuv; Krug, Andrew Z.; Valentine, James W.

2012-01-01

113

Acute bioassays with benthic macroinvertebrates conducted in situ  

SciTech Connect

Several methods of toxicity testing using macroinvertebrates in controlled laboratory experiments have been reported. Researchers conducted bioassays with natural assemblages of benthic macroinvertebrates exposed to several petroleum refinery effluents. They found that the populations of invertebrates declined after only a few days of exposure. The objective of the study was to determine the acute toxic effects of discharge water from a petrochemical complex on a natural assemblage of benthic macroinvertebrates. The discharge water consisted of refinery wastewater and sanitary wastewater, as well as brine discharge from a power/desalination plant. The benthic macroinvertebrates were transplanted from a healthy reef area to the outfall channel receiving the discharge water. The study began on October 7, 1985, and concluded that same week. Any decrease in specific species would indicate that the discharge was toxic to these species. These species could also serve as indicators of toxic conditions at other locations.

Whaley, M.; Garcia, R.; Sy, J. (Amartech Ltd., Yanbu Al-Sinaiyah (Saudi Arabia))

1989-10-01

114

Clinch River remedial investigation task 9 -- benthic macroinvertebrates  

SciTech Connect

This report summarizes the results of Task 9 of the TVA/Department of Energy (DOE) Interagency Agreement supporting DOE`s Clinch River Remedial Investigation. Species lists and densities (numbers/m{sup 2}) of benthic macroinvertebrates sampled at 16 sites in the Clinch River and Poplar Creek embayments of upper Watts Bar Reservoir near Oak Ridge, Tennessee, in March, 1994, are presented and briefly discussed. Data are also analyzed to assess and compare quality of benthic communities at each site, according to methods developed for TVA`s Reservoir Vital Signs Monitoring Program. Results of this study will be incorporated with other program tasks in a comprehensive report prepared by Oak Ridge National Laboratory in 1995, which will, in part, assess the effect of sediment contaminants on benthic macroinvertebrate communities in Watts Bar Reservoir.

Scott, E.M. Jr.

1994-08-01

115

Seasonal fluctuations in benthic protozoan populations at different depths in marine sediments  

NASA Astrophysics Data System (ADS)

We used epifluorescence microscopy to enumerate small (< 20 ?m) protozoa in extracts of flushed fixed sediment samples. This method retrieved 91±4% ( x ± se) of cultured flagellates from sediments. Protist densities at different depths in the sediments were studied over 1 year at 3 intertidal flats in the Wadden Sea. There was a general pattern of seasonal density fluctuation at all sites with a marked increase in March from winter density levels (50 to 100·10 3·cm -3) to 2 to 3 times higher summer levels (150 to 300·10 3·cm -3). Deeper in the sediments (30 to 33 and 60 to 63 mm) densities were throughout the year 2 to 3 times lower than in the sediment surface layer. Fluctuations in densities at the surface were generally mirrored at greater depths. At least 50% of the cells were in the size class of 2 to 5 ?m. Estimates for total biomass ranged between 1.2 and 8.5·10 -6 g C·cm -3. About 33% of the protists contained chlorophyll. There were no obvious correlations with concurrently measured parameters such as porosity, POC, bacterial numbers or biomass. Increased bacterial productivity, however, was invariably paralleled by increased protist densities. This suggests that high benthic protist densities are indications of high benthic microbial growth.

Bak, R. P. M.; Nieuwland, G.

116

Spectral library of macroalgae and benthic substrates in Estonian coastal waters  

Microsoft Academic Search

Benthic algal cover and trends in its changes are indicators of water state in coastal areas. Mapping benthic algal cover with conventional methods (diving) provides great accuracy and high resolution yet is very expensive and is limited by the time and manpower necessary to monitor large bodies of water and long stretches of coastline. Mapping of benthic macroalgal cover by

Tiit Kutser; Ele Vahtmäe; Liisa Metsamaa

2006-01-01

117

APPLICATION OF TWO INDICES OF BENTHIC COMMUNITY CONDITION IN CHESAPEAKE BAY  

EPA Science Inventory

The Chesapeake Bay Benthic Index of Biotic Integrity (B-161) and the Environmental Monitoring and Assessment Program's Virginian Province Benthic Index (EMAP-VP BI) were applied to 294 sampling events in Chesapeake Bay and the results were compared. These benthic indices are inte...

118

Benthic microalgae in coral reef sediments of the southern Great Barrier Reef, Australia  

Microsoft Academic Search

The abundance and productivity of benthic microalgae in coral reef sediments are poorly known compared with other, more conspicuous (e.g. coral zooxanthellae, macroalgae) primary producers of coral reef habitats. A survey of the distribution, biomass, and productivity of benthic microalgae on a platform reef flat and in a cross-shelf transect in the southern Great Barrier Reef indicated that benthic microalgae

C. A. Heil; K. Chaston; A. Jones; P. Bird; B. Longstaff; S. Costanzo; W. C. Dennison

2004-01-01

119

An analysis of benthic biological dynamics in a North Sea ecosystem model  

Microsoft Academic Search

This paper presents an overview and analysis of the benthic biological submodel of the European Regional Seas Ecosystem Model II (ERSEM II). This submodel consists of a detailed model description of the benthic system which is integrated with a marine ecosystem model which attempts to address the full range of pelagic and benthic biogeochemical and physical processes. The submodel simulates

J. C. Blackford

1997-01-01

120

Rates of Ocean Acidification: Decoupling of Planktic and Benthic Extinctions?  

NASA Astrophysics Data System (ADS)

Deep-sea benthic organisms derive food from export of organic matter produced in the photic zone, so that pelagic and benthic productivity are coupled, suggesting that severe extinction of plankton and benthos in the geological past should have been coupled. An asteroid impact at the Cretaceous/Paleogene (K/Pg) boundary (~65 Ma), however, caused mass extinction of calcifying plankton (foraminifera and nannoplankton), whereas benthic calcifyers (foraminifera) did not suffer significant extinction. Also, pelagic calcifyers did not suffer severe extinction during the carbon-cycle perturbation and global warming at the Paleocene-Eocene (P/E) boundary 10 myr later, when deep-sea benthic foraminifera did. The K/Pg extinction has been interpreted as darkness-caused collapse of productivity, but this is not supported by the lack of benthic extinction. To evaluate extinction mechanisms, we compared benthic foraminiferal and stable isotope records at ODP sites in the Pacific, SE Atlantic and Southern Oceans. Across the K/Pg boundary, the decrease in export productivity was moderate, regionally variable, and insufficient to explain the mass extinction at higher levels of the food chain. Across the P/E boundary, productivity increased in epicontinental seas and on continental margins, whereas pelagic productivity may have declined (increased trophic resource continuum). We thus found no evidence that the different benthic and pelagic extinction patterns at K/Pg and P/E were linked to changes in (export) productivity. Instead, the difference between planktic and benthic extinction patterns may have been caused by the occurrence of ocean acidification at different rates. Very rapid (faster than present anthropogenic) surface ocean acidification at the K/Pg boundary may have been due to influx of impact-generated nitric acid, followed by rapid oceanic buffering. This may have been a factor in the massive extinction of pelagic calcifyers, ammonites and top-level predators such as large fish and mosasaurs, while oceanic productivity in terms of biomass recovered rapidly. Acidification at the end of the Paleocene was triggered by the much slower injection of a large mass of carbon-compounds into the atmosphere and transfer into the oceans (~10-20 kyr), leading to severe extinction of deep-sea calcifying benthos, but much less severe turnover in the plankton. The study of the biogeography of biotic consequences of the K/Pg and P/E boundary events thus may assist in the evaluation of the varying effects on oceanic biota with varying rates and sources of acidification.

Thomas, E.; Alegret, L.

2012-12-01

121

Effects of CO2 on benthic biota: an in situ benthic chamber experiment in Storfjorden (Norway).  

PubMed

Carbon capture and storage (CCS) methods, either sub-seabed or in ocean depths, introduces risk of CO2 leakage and subsequent interaction with the ecosystem. It is therefore important to obtain information on possible effects of CO2. In situ CO2 exposure experiments were carried out twice for 10 days during 2005 using a Benthic Chamber system at 400 m depth in Storfjorden, Norway. pCO2 in the water above the sediment in the chambers was controlled at approximately 500, 5000 and 20,000 ?atm, respectively. This article describes the experiment and the results from measured the biological responses within the chamber sediments. The results show effects of elevated CO2 concentrations on biological processes such as increased nanobenthos density. Methane production and sulphate reduction was enhanced in the approximately 5000 ?atm chamber. PMID:23465619

Ishida, Hiroshi; Golmen, Lars G; West, Julia; Krüger, Martin; Coombs, Patricia; Berge, John Arthur; Fukuhara, Tastuo; Magi, Michimasa; Kita, Jun

2013-08-30

122

Pelagic and benthic ecology of the lower interface of the Eastern Tropical Pacific oxygen minimum zone  

NASA Astrophysics Data System (ADS)

The distributions of pelagic and benthic fauna were examined in relation to the lower boundary of the oxygen minimum zone (OMZ) on and near Volcano 7, a seamount that penetrates this feature in the Eastern Tropical Pacific. Although the broad, pronounced OMZ in this region is an effective barrier for most zooplankton, zooplankton abundances, zooplankton feeding rates, and ambient suspended particulate organic carbon (POC) peaked sharply in the lower OMZ (about 740-800 m), in association with the minimum oxygen concentration and the increasing oxygen levels just below it. Zooplankton in the lower OMZ were also larger in size, and the pelagic community included some very abundant, possibly opportunistic, species. Elevated POC and scatter in the light transmission data suggested the existence of a thin, particle-rich, and carbon-rich pelagic layer at the base of the OMZ. Gut contents of planktonic detrifvores implied opportunistic ingestion of bacterial aggregates, possibly from this layer. Benthic megafaunal abundances on the seamount, which extended up to 730 m, peaked at about 800 m. There was a consistent vertical progression in the depth of first occurrence of different megafaunal taxa in this depth range, similar to intertidal zonation. Although the vertical gradients of temperature, salinity, and oxygen were gradual at the lower OMZ interface (in contrast to the upper OMZ interface at the thermocline), temporal variability in oxygen levels due to internal wave-induced vertical excursions of the OMZ may produce the distinct zonation in the benthic fauna. The characteristics of the lower OMZ interface result from biological interactions with the chemical and organic matter gradients of the OMZ. Most zooplankton are probably excluded physiologically from pronounced OMZs. The zooplankton abundance peak at the lower interface of the OMZ occurs where oxygen becomes sufficiently high to permit the zooplankton to utilize the high concentrations of organic particles that have descended through the OMZ relatively unaltered because of low metazoan abundance. A similar scenario applies to megabenthic distributions. Plankton layers and a potential short food chain (bacteria to zooplankton) at OMZ interfaces suggest intense utilization and modification of organic material, localized within a thin midwater depth zone. This could be a potentially significant filter for organic material sinking to the deep-sea floor.

Wishner, Karen F.; Ashjian, Carin J.; Gelfman, Celia; Gowing, Marcia M.; Kann, Lisa; Levin, Lisa A.; Mullineaux, Lauren S.; Saltzman, Jennifer

1995-01-01

123

Modelling benthic oxygen consumption and benthic-pelagic coupling at a shallow station in the southern North Sea  

NASA Astrophysics Data System (ADS)

A time-series of benthic oxygen consumption, water-column and sediment chlorophyll concentrations, and temperature in the southern North Sea was subjected to inverse modelling in order to study benthic-pelagic coupling in this coastal marine system. The application of a Markov Chain Monte Carlo (MCMC) on a simple box model allowed deriving deposition rates and temperature-dependent remineralization rates of both phytopigments and bulk carbon, as well as estimates of uncertainty for each of these processes. Together with organic matter availability, temperature had an important effect on benthic respiration rates thus delaying remineralization of spring bloom material until the late summer when temperatures were at their highest. The sediment at our station clearly acts as a buffer, removing large quantities of nutrients from the pelagic system during the spring bloom and only slowly releasing them back into the water column as temperatures increase later during summer.

Provoost, Pieter; Braeckman, Ulrike; Van Gansbeke, Dirk; Moodley, Leon; Soetaert, Karline; Middelburg, Jack J.; Vanaverbeke, Jan

2013-03-01

124

Geophysical Conceptual Model for Benthic Flux and Submarine Groundwater Discharge  

NASA Astrophysics Data System (ADS)

Numerous investigators characterize benthic flux and submarine groundwater discharge (SGD) using a geochemical conceptual model that relies on the estimation of tracer fluxes into and out of a control volume. (Benthic flux is the rate of flow across the bed of any water body, per unit area of bed. Benthic flux is a vector that includes both discharge and recharge components. SGD is a benthic water discharge flux to a marine water body.) For the geochemical approach, benthic discharge flux or SGD is estimated by summing the flux of tracer into or out of the control volume---a water body or portion of a water body---and deducing that tracer deficiency within the control volume must be explained by SGD. Typically, estimated or measured fluxes include advection and mixing in surface-water, diffusion, evasion across the air-water interface, production, and decay. The geochemical model, however, does not account for fluxes that do not transport tracer. For example, investigators found equivalent (<10 dpm per liter) radon activities in both surface water, and in pore fluid within the upper 30 cm of sediment in the Indian River Lagoon, Florida, in June and July 2003. At this location, a surface-gravity wave with a five-centimeter amplitude and one-second period in 0.5 m of water forced a 12-cm-per-day SGD. The radon tracer technique may not characterize SGD forced by the one-second wave due to the time scale of the wave, the absence of a radon activity gradient between bed medium and surface water, and the <30 cm depth to which the wave affects the flow field within the porous medium. A new geophysical conceptual model for benthic flux is proposed. The model parses benthic flux into components driven by individual forcing mechanisms. The model recognizes that benthic flux components may interact in a constructive or destructive manner, such that benthic flux generated by multiple forcing mechanisms at the same location may not be equivalent to the linear sum of benthic flux generated by single forcing mechanisms. Restated: the whole may be different than the sum of the parts. Individual forcing mechanisms that drive benthic flux components include: the terrestrial hydraulic gradient, tide, surface gravity waves, density gradients, chemical gradients, diagenesis, bio-irrigation, sea-level rise, and bedform-current interaction. Other forcing mechanisms surely exist. Although many of these component forcing mechanisms can be characterized, component interactions are not fully understood. Differences exist between the geophysical and geochemical conceptual models. The geochemical model integrates the contribution of forcing mechanisms over both the control volume and duration of study. Because a tracer can not characterize a flux that does not transport the tracer, and because the time-scale or spatial-scale of some SGD forcing mechanisms is not resolved by certain tracers, the geochemical model may not describe all SGD to a water body. Restated: the geochemical model may only describe the component of SGD that transports the tracer. Some components of the geophysical model may be difficult or impossible to measure in natural systems. Interaction between specific components of the geophysical model may be intractable.

King, J. N.

2010-12-01

125

Effects of harvesting callianassid (ghost) shrimps on subtropical benthic communities  

Microsoft Academic Search

The effects of harvesting of callianassid shrimp (Trypaea australiensis) on the abundance and composition of macrobenthic assemblages in unvegetated sediments of a subtropical coastal embayment in Queensland, Australia were examined using a combination of sampling and manipulative experiments. First, the abundance and composition of the benthic infauna in an area regularly used for the collection of shrimp for bait by

Greg A. Skilleter; Yuri Zharikov; Bronwyn Cameron; Daryl P. McPhee

2005-01-01

126

An Apparatus for Preparing Benthic Samples aboard Ship  

Microsoft Academic Search

We describe a safe and effective apparatus for washing and reducing the volume of benthic samples collected by grab samplers aboard ship. The sample is transferred directly from the dredge to the apparatus and then washed with water pumped through pipes in the apparatus and from onboard hoses. Wastewater and materials smaller than 0.541 mm in diameter are washed overboard.

Phillip N. Pepper; Thomas L. Girard; Martin A. Stapanian

2001-01-01

127

A survey of benthic invertebrates in the Suwannee River, Florida  

Microsoft Academic Search

Benthic invertebrate communities were surveyed in a 233 km reach of the middle and lower Suwannee River in Northwestern Florida in the winter 1987 and early summer 1988 to determine their abundance and distribution as potential foods of the Gulf sturgeon, Acipenser oxyrhynchus desotoi, and to determine the effects of possible natural and human-induced disturbances to the communities. In substrates

William T. Mason

1991-01-01

128

BENTHIC MACROFAUNA-HABITAT RELATIONSHIPS IN TWO PACIFIC NORTHWEST ESTUARIES  

EPA Science Inventory

Habitat-based ecological risk assessments rely, in part, on estimates of the ecological value of the habitats at risk. As part of a larger programmatic effort to estimate estuarine habitat values, we determined benthic macrofauna-habitat relationships for 8 intertidal habitats i...

129

BENTHIC MACROFAUNA AND HABITAT RELATIONSHIPS IN TILLAMOOK BAY  

EPA Science Inventory

Tillamook Bay is subject to natural and man-made stressors, such as increased nutrients and sediments, which can alter its habitats and, thereby, impact its productivity and ecological resources. The benthic macrofauna are small, sediment-dwelling invertebrates which have strong...

130

Mapping coral reef benthic cover with fused IKONOS imagery  

Microsoft Academic Search

In this article, we present some experiments on coral reef benthic cover mapping with fused IKONOS image. The objective of our study is to establish an efficient approach for the classification task on hand. Four scenarios are designed and in each scenario two classification methods (Maximum Likelihood and Decision Tree) are implemented. Ground truth data is obtained through visual interpretation

Yuanyuan Wang; Yunhao Chen; Jing Li

2007-01-01

131

Benthic foraminifera of a Miocene canyon and fan  

Microsoft Academic Search

We present benthic foraminiferal assemblage data from an exhumed Miocene canyon and fan system from the Tabernas Basin (SE Spain). The presence of good indicator taxa and unique assemblages occupying specific environments allows the distinction of slope, canyon and fan environments within the Tabernas Basin by foraminiferal assemblages alone. Five assemblages are defined on the basis of the occurrence of

M. Rogerson; T. J. Kouwenhoven; G. J. van der Zwaan; B. J. O'Neill; C. J. van der Zwan; G. Postma; K. Kleverlaan; H. Tijbosch

2006-01-01

132

CHARACTERISTICS OF BENTHIC ALGAL COMMUNITIES IN THE UPPER GREAT LAKES  

EPA Science Inventory

The upper Great Lakes contain a diverse array of benthic algal communities. Characteristic communities occupy substrates from the supralittoral to depths in excess of 30 m. Diatoms are the dominant taxonomic group present in terms of numbers, and usually in terms of biomass, exce...

133

Reservoir manipulations and benthic macroinvertebrates in a Prairie River  

Microsoft Academic Search

Samples were taken on the Tongue River, Montana, USA, during 1974 and 1975 to determine the distributions and abundances of the benthic fauna after various reservoir manipulations. The upper cold water section, influenced by hypolimnial discharge from the Tongue River Reservoir, was impoverished in insect fauna and dominated by the molluscs Physa and Sphaerium. The lower warm water sections of

James A. Gore

1977-01-01

134

PHOTOINDUCED TOXICITY OF FLUORANTHENE TO SEVEN MARINE BENTHIC CRUSTACEANS  

EPA Science Inventory

Seven marine benthic crustaceans were exposed in 4 d water-only toxicity tests to five concentrations of fluoranthene.After exposures, mortality (LC50) and the ability to bury in clean sediment (EC50) were determined. Survivors were then exposed to UV radiation for 1 h. The diffe...

135

Benthic foraminiferal response to experimentally induced Erika oil pollution  

Microsoft Academic Search

Benthic foraminifera from an intertidal mudflat (Bay of Bourgneuf, France) have been exposed to different types of oil-polluted seawater in an experimental laboratory setting. The aim of this experiment was to study the response of foraminiferal faunas from the intertidal zone to oil spills, as observed after the wreckage of the Erika oil tanker in December 1999 on the French

S. R. Ernst; J. Morvan; E. Geslin; A. Le Bihan; F. J. Jorissen

2006-01-01

136

On the coupling of benthic and pelagic biogeochemical models  

Microsoft Academic Search

Mutual interaction of water column and sediment processes is either neglected or only crudely approximated in many biogeochemical models.We have reviewed the approaches to couple benthic and pelagic biogeochemical models. It is concluded that they can be classified into a hierarchical set consisting of five levels, differing in the amount of detail given to the sediment processes. The most complex

Karline Soetaert; Jack J. Middelburg; Peter M. J. Herman; Kerst Buis

2000-01-01

137

Measuring coral reef community metabolism using new benthic chamber technology  

Microsoft Academic Search

Accurate measurement of coral reef community metabolism is a necessity for process monitoring and in situ experimentation on coral reef health. Traditional methodologies used for these measurements are effective but limited by location and scale constraints. We present field trial results for a new benthic chamber system called the Submersible Habitat for Analyzing Reef Quality (SHARQ). This large, portable incubation

K. K. Yates; R. B. Halley

2003-01-01

138

Impact of benthic disturbance on megafauna in Central Indian Basin  

Microsoft Academic Search

Deep-sea photographs and video data were studied to evaluate the effects of benthic disturbance on megafaunal distribution in the Central Indian Basin. Xenophyophores (41%) and holothurians (30%) are the most abundant taxa, followed by other groups in the area before the disturbance. An overall reduction (32%) in the total megafaunal population after disturbance is direct evidence of the impact on

Nimi Rodrigues; Rahul Sharma; B. Nagendernath

2001-01-01

139

DETECTING BENTHIC COMMUNITY DIFFERENCES: INFLUENCE OF STATISTICAL INDEX AND SEASON  

EPA Science Inventory

An accurate assessment of estuarine condition is critical to determining whether there has been a change from baseline or 'natural' conditions; benthic communities are routinely used as an ecological endpoint to make this assessment. We addressed two issues which arise when attem...

140

Synthesis of benthic flux components in the Patos Lagoon coastal zone, Rio Grande do Sul, Brazil  

NASA Astrophysics Data System (ADS)

The primary objective of this work is to synthesize components of benthic flux in the Patos Lagoon coastal zone, Rio Grande do Sul, Brazil. Specifically, the component of benthic discharge flux forced by the terrestrial hydraulic gradient is 0.8 m3 d-1; components of benthic discharge and recharge flux associated with the groundwater tidal prism are both 2.1 m3 d-1; components of benthic discharge and recharge flux forced by surface-gravity wave setup are both 6.3 m3 d-1; the component of benthic discharge flux that transports radium-228 is 350 m3 d-1; and components of benthic discharge and recharge flux forced by surface-gravity waves propagating over a porous medium are both 1400 m3 d-1. (All models are normalized per meter shoreline.) Benthic flux is a function of components forced by individual mechanisms and nonlinear interactions that exist between components. Constructive and destructive interference may enhance or diminish the contribution of benthic flux components. It may not be possible to model benthic flux by summing component magnitudes. Geochemical tracer techniques may not accurately model benthic discharge flux or submarine groundwater discharge (SGD). A conceptual model provides a framework on which to quantitatively characterize benthic discharge flux and SGD with a multifaceted approach.

King, J. N.

2012-12-01

141

A review of benthic faunal surveys in San Francisco Bay  

USGS Publications Warehouse

During the past 60 years, considerable effort has been expended in studies of the relations of the biotic community and physicochemical characteristics of San Francisco Bay water. In very recent years these studies have emphasized the relations between the 'state of health' of bottom-living invertebrates (the benthos) and the levels of pollutants in the bay. Benthic organisms, generally sessile, are unable to escape deleterious environmental changes, and they reflect these changes in alterations of normal species composition of assemblages and species abundance. Data that expands understanding of these relations in urbanized areas such as San Francisco Bay are critical. Because of the implications of such data in control of water quality, the U.S. Geological Survey undertook a review of the results and major conclusions of San Francisco Bay benthic surveys. The size and species composition of faunal assemblages are largely controlled by the salinity of the water, the texture of the bottom sediments, and locally by wastes discharged into the bay. Efforts to describe the structure and function of benthic communities of the bay and to quantify the effects of waste discharge on them have been hampered by inconsistent and often faulty sampling methodology and species identification. Studies made show a lack of information on the normal life processes of the organisms concerned. The diversity index (a mathematical expression of the number of kinds of organisms present at a location), commonly used to describe the 'health' of the benthic community, has been employed without regard for the need for standardizing methodology and species identifications or for understanding natural biological processes that affect such mathematical indices. There are few reliable quantitative data on the distribution of benthic organisms in San Francisco Bay with which future assessments of the 'health' of the benthic community might be compared. Methods for study of the benthos must be standardized, identifications of species verified by trained taxonomists, and new field and laboratory studies undertaken before we can expect to obtain an accurate description of the benthic fauna and its relations with the environment.

Nichols, Frederic H.

1973-01-01

142

Benthic oxygen consumption on continental shelves off eastern Canada  

NASA Astrophysics Data System (ADS)

The consumption of phytoplankton production by the benthos is an important component of organic carbon budgets for continental shelves. Sediment texture is a major factor regulating benthic processes because fine sediment areas are sites of enhanced deposition from the water column, resulting in increased organic content, bacterial biomass and community metabolism. Although continental shelves at mid- to high latitudes consist primarily of coarse relict sediments ( PIPER, Continental Shelf Research, 11, 1013-1035), shelf regions of boreal and subarctic eastern Canada contain large areas of silt and clay sediments ( FADER, Continental Shelf Research, 11, 1123-1153). We collated estimates of benthic oxygen consumption in coarse (<20% silt-clay, <0.5% organic matter) and fine sediments (20% silt-clay, 0.5% organic matter) for northwest Atlantic continental shelves including new data for Georges Bank, the Scotian Shelf, the Grand Banks of Newfoundland and Labrador Shelf. Estimates were applied to the areal distribution of sediment type on these shelves to obtain a general relationship between sediment texture and benthic carbon consumption. Mean benthic oxygen demand was 2.7 times greater in fine sediment than in coarse sediment, when normalized to mean annual temperature. In terms of carbon equivalents, shelf regions with minimal fine sediment (Georges Bank, the Grand Banks of Newfoundland-northeast Newfoundland) consumed only 5-8% of annual primary production. Benthos of the Gulf of Maine (100% fine sediment) and the Scotian Shelf (35% fine sediment) utilized 16-19% of primary production. Although 32% of the Labrador Shelf area contained fine sediments, benthic consumption of pelagic production (8%) was apparently limited by low mean annual temperature (2°C). These results indicate that incorporation of sediment-specific oxygen uptake into shelf carbon budgets may increase estimates of benthic consumption by 50%. Furthermore, respiration and production by large macrofauna allow an even greater proportion of primary production to enter benthic pathways. Fine sediment areas (shelf basins or "depocenters") are postulated to be sites of enhanced biological activity which must be considered in the modelling of shelf carbon budgets and the role of the benthos in demersal fisheries.

Grant, Jonathan; Emerson, Craig W.; Hargrave, Barry T.; Shortle, Jeannette L.

1991-08-01

143

The PROWQM physical biological model with benthic pelagic coupling applied to the northern North Sea  

NASA Astrophysics Data System (ADS)

PROWQM, a 1-D depth resolving model which couples physical and microbiological processes in the water column with sedimentation/resuspension and benthic mineralisation processes, has been used to simulate seasonal changes of chlorophyll, nutrients and oxygen at the PROVESS north site (59°20'N 1°00'E) in the North Sea. PROWQM is derived from the 3-D model COHERENS, and improves COHEREN's benthic and pelagic biology. The physical sub-model of PROWQM implicitly solves turbulence closure equations forced by climatological, or realistic high-frequency, meteorological and tidal data. The pelagic biological sub-model 2MPPD includes a 'diatomy' microplankton (mp1) and a 'flagellatey' (or microbial loop) microplankton (mp2), the cycling of silicon and nitrogen, slow-sinking detritus, and fast-sinking phytodetritus. Phytodetritus is formed by shear-driven aggregation of particulate material, using a simple algorithm for bulk processes that is derived by considering the interactions of single cells. The microplankton compartments include heterotrophic bacteria and protozoa as well as phytoplankton, and most microplankton rates are specified with the aid of a 'heterotroph fraction' parameter, which was 0.125 for mp1 and 0.6 for mp2. The microbiological system is closed by mesozooplankton grazing pressures imposed as time varying series determined from observed zooplankton abundance. The benthic boundary sub-model includes a superficial fluff layer and a nutrient element reservoir in the consolidated sediment. Particulate material in the fluff layer can be resuspended (in response to bed stress by near-bed flows), mineralised or carried by bioturbation into the underlying, consolidated, sediment, where it is mineralised and its nutrients returned to the water-column at rates mainly dependent on (implicit) macrobenthic pumping. Benthic denitrification can occur when mineralisation rates exceed oxygen supply. Verification of the PROWQM numerical implementation used test cases and checks for nutrient element conservation. Simulations with realistic forcing, for a range of parameter values, were compared with historic observations in the NOWESP data set and during FLEX76, and with those made during the PROVESS cruises in autumn 1998. PROWQM provided a good simulation of the seasonal succession from a diatom-dominated spring bloom to summer dominance by small flagellates. The simulations included sedimentation of organic matter from the spring bloom, and qualitatively realistic behaviour of the fluff layer, but decay rates were too slow and there was almost no denitrification. The simulated surface mixed layer was too shallow during the summer. Simulated annual net microplankton primary production was in between 59 and 91 g C m -2 y -1. A large proportion of mineralisation, 28-47% of nitrogen and 40-67% of silicon mineralisation, took place as a result of the decay of sinking and resuspended detritus whilst in the water column. PROWQM is discussed in relation to other models that have been used to simulate this part of the North Sea, in particular the simpler ECOHAM1 and the more complex ERSEM, and in relation to PROWQM's evolution from COHERENS.

Lee, Jae-Young; Tett, Paul; Jones, Ken; Jones, Sarah; Luyten, Patrick; Smith, Claire; Wild-Allen, Karen

2002-12-01

144

Layers and Layers  

NSDL National Science Digital Library

This lesson has students create their own rock layers by slowly adding and observing how different types of sediment interact when layered upon each other. This lesson is meant to illustrate how we can use these layers to discover the relative age of an object found in that layer by utilizing the Law of Superposition.

Tremarco, Cheri

2011-10-07

145

Benthic photosynthesis and oxygen consumption in permeable carbonate sediments at Heron Island, Great Barrier Reef, Australia  

NASA Astrophysics Data System (ADS)

In order to investigate benthic photosynthesis and oxygen demand in permeable carbonate sands and the impact of benthic boundary layer flow on sedimentary oxygen consumption, in situ and laboratory chamber experiments were carried out at Heron Island, Great Barrier Reef, Australia. Total photosynthesis, net primary production and respiration were estimated to be 162.9±43.4, 98.0±40.7, and 64.9±15.0 mmol C m -2 d -1, respectively. DIN and DIP fluxes for these sands reached 0.34 and 0.06 mmol m -2 d -1, respectively. Advective pore water exchange had a strong impact on oxygen consumption in the permeable sands. Consumption rates in the chamber with larger pressure gradient (20 rpm, 1.2 Pa between centre and rim) simulating a friction velocity of 0.6 cm s -1 were approximately two-fold higher than in the chambers with slow stirring (10 rpm, 0.2 Pa between centre and rim, friction velocity of 0.3 cm s -1). In the laboratory chamber experiments with stagnant water column, oxygen consumption was eight times lower than in the chamber with fast stirring. Laboratory chamber experiments with Br - tracer revealed solute exchange rates of 2.6, 2.2, 0.7 ml cm -2 d -1 at stirring rates of 20, 10, and 0 rpm, respectively. In a laboratory experiment investigating the effect of sediment permeability on oxygen and DIC fluxes, a three-fold higher permeability resulted in two- to three-fold higher oxygen consumption and DIC release rates. These experiments demonstrate the importance of boundary flow induced flushing of the upper layer of permeable carbonate sediment on oxygen uptake in the coral sands. The high filtration and oxidation rates in the sub-tropical permeable carbonate sediments and the subsequent release of nutrients and DIC reveal the importance of these sands for the recycling of matter in this oligotrophic environment.

Rasheed, Mohammed; Wild, Christian; Franke, Ulrich; Huettel, Markus

2004-01-01

146

Phototoxicity of TiO2 nanoparticles to a freshwater benthic amphipod: are benthic systems at risk?  

EPA Science Inventory

This study investigated phototoxicity of TiO2 nanoparticles (nano-TiO2) to a freshwater benthic amphipod (Hyalella azteca) using 48-h and 96-h bioassays. Thorough monitoring of particle interactions with exposure media (Lake Superior water, LSW) and the surface of organisms was p...

147

Benthic geochemistry of manganese in the Bay of Biscay, and sediment mass accumulation rate  

NASA Astrophysics Data System (ADS)

Manganese is a major redox reactive element of benthic metabolism. We have built a database of existing knowledge on the benthic geochemistry of Mn in the Bay of Biscay, in order to comprehensively assess the behaviour of Mn in a variety of environments during early diagenesis. The database contains vertical profiles of particulate and dissolved Mn species of 59 cores collected during 17 cruises between 1997 and 2006 at nine stations positioned between 140 and 4,800 m water depths. At all studied stations, Mn species follow the conventional distribution, where Mn(III,IV) species are enriched in the oxic layer, and dissolved Mn is present in the anoxic sediments. A minor part of Mn-oxides originates from sedimenting particles. The major part is of diagenetic origin, and derives from the oxidation of upward-diffusing dissolved Mn(II). Mn-oxide inventories are higher at the deeper stations than at the shallower ones. This difference cannot be attributed to different sources of sedimenting particles, but it must depend on sedimentation rate and diagenetic processes. At depth, dissolved Mn(II) concentrations are constant. This probably reflects equilibrium with an authigenic Mn(II) phase, which is the ultimate phase into which Mn is fossilized. The Mn content of deeper anoxic sediments is similarly low in all the cores studied, associated with corresponding trends of Mn content in sedimenting particles of the Bay of Biscay. Bioturbation, rather than redox oscillations, can convey Mn(III,IV) species downwards into the anoxic sediments where they are reduced, associated with a peak of dissolved Mn. Because dissolved Mn(II) is re-oxidized when it diffuses towards the oxic layer, the inventory of the diagenetic Mn(III,IV) phase remains at steady state, especially at stations where the oxic layer is thick. It then becomes possible to calculate the residence time of diagenetic Mn(III,IV) particles within the oxic layer, using the upward-directed flux of pore water Mn(II). By applying this residence time to the accumulation of sediments within the oxic layer, we obtain the sediment mass accumulation rate. The values calculated for the sediments of the Bay of Biscay fit well with accumulation rates obtained from radionuclides or sediment traps. The method has also been validated with data collected in other marine sedimentary environments.

Mouret, Aurélia; Anschutz, Pierre; Lecroart, Pascal; Chaillou, Gwénaëlle; Hyacinthe, Christelle; Deborde, Jonathan; Jorissen, Frans J.; Deflandre, Bruno; Schmidt, Sabine; Jouanneau, Jean-Marie

2009-06-01

148

Depth Dependant Variations in Benthic Foraminiferal Assemblages and Stable Isotopes Across the P-E Boundary, Walvis Ridge (ODP Leg 208)  

NASA Astrophysics Data System (ADS)

The Paleocene-Eocene Thermal Maximum (PETM) ( ˜55 Ma), was characterized by extreme global warming, a negative carbon isotope excursion, intensified carbonate dissolution, and a severe mass extinction of benthic foraminifera. The lack of continuous, undisturbed cores over a wide depth range has limited efforts to place constraints on key aspects of the PETM event, such as changes in ocean redox and carbon chemistry, and depth dependent patterns of the benthic extinction. The P-E boundary was recovered in multiple holes at 5 sites from Walvis Ridge in the southeastern Atlantic (ODP Leg 208). We document changes in benthic assemblages and stable isotopes across the PETM at ODP Leg 208, and compare these with data from other PE boundary sections, including DSDP Sites 525 and 527 previously drilled on Walvis Ridge. Faunal assemblage analyses show a distinct drop in diversity coincident with the base of the clay layer at all sites. There is a clear relationship between water depth and magnitude of the benthic foraminifera isotope excursion along the Walvis Ridge depth transect. Site 1263 (2717m) records excursion values of -2.2 ? 13C and -2.5 ? 18O; whereas Site 1262 (4759m) has values of -0.2 ? 13C and -0.8 ? 18O at the height of the excursion. This difference implies truncation of the record at deeper sites by carbonate dissolution, possibly as well as a depth dependent difference in water mass chemistry and temperature during the PETM. Several benthic foraminiferal species such as Nuttallides truempyi and various abyssaminid species that may indicate low nutrient availability increase in abundance at the onset of the isotope excursion, while the percentage of biserial and triserial species, used as high food/low oxygen indicators, decreases. There are thus distinct changes in ocean chemistry over the 2.3 km paleodepth range of the Walvis Ridge transect during the PETM event.

McCarren, H. K.; Thomas, E.; Zachos, J.

2004-12-01

149

Saturated and unsaturated hydrocarbons in marine benthic algae  

Microsoft Academic Search

Saturated and olefinic hydrocarbons were determined in 24 species of green, brown and red benthic marine algae from the Cape Cod area (Massachusetts, USA). Among the saturated hydrocarbons, n-pentadecane predominates in the brown and n-heptadecane in the red algae. A C17 alkyleyclopropane has been identified tentatively in Ulvalactuca and Enteromorpha compressa, two species of green algae. Mono-and diolefinic C15 and

W. W. Youngblood; M. Blumer; R. L. Guillard; F. Fiore

1971-01-01

150

Benthic foraminifera from polluted marine environment of Sulaibikhat Bay (Kuwait)  

Microsoft Academic Search

Quantitative analyses of recent benthic foraminiferal assemblages (living and dead) were carried out on the surface sediments\\u000a of Sulaibikhat Bay. Marked contrast in foraminiferal assemblages between the shallow tidal mudflats and the deep tidal channel\\u000a and their relation to the extent of pollution were observed. Cluster analysis of quantitative data on the distribution of\\u000a foraminiferal tests revealed three assemblages that

A. Z. Al-Zamel; M. A. Al-Sarawi; S. R. Khader; I. A. Al-Rifaiy

2009-01-01

151

Bipolar gene flow in deep-sea benthic foraminifera  

Microsoft Academic Search

Despite its often featureless appearance, the deep-ocean floor includes some of the most diverse habitats on Earth. However, the accurate assessment of global deep-sea diversity is impeded by a paucity of data on the geographical ranges of bottom-dwelling species, particularly at the genetic level. Here, we present molecular evidence for exceptionally wide distribution of benthic foraminifera, which constitute the major

J. PAW L O W S K I; J. FA H R N I; A. J. G O O D AY; Quai Ernest Ansermet

152

Pre and post-settlement events in benthic community dynamics  

Microsoft Academic Search

In all marine benthic environments, organism replacement depends on recruitment limitation, i.e. the impact of both pre- and post-settlement events on the success of recruitment. The relative contribution of pre- versus post-settlement processes in shaping adult populations has been extensively studied. Most analyses concluded that recruitment limitation is a strong determinant of adults’ density. The magnitude of its limitation depends

Simonetta Fraschetti; Adriana Giangrande; Antonio Terlizzi; Ferdinando Boero

2002-01-01

153

Impact of deforestation on benthic macroinvertebrate communities in tributaries of  

Microsoft Academic Search

Benthic macroinvertebrate communities of Lake Tanganyika tributaries in pristine, forested, and impacted, deforested, watersheds were examined. Samples were collected using a Surber-sampler, and identified under a dissecting microscope. Family biotic indices (FBI), percent of Ephemeroptera\\/Plecoptera\\/Trichoptera (%EPT), relative Chironomid abundance (RCA), and taxa richness of five impacted streams in western Tanzania were compared, using paired t-test and single factor ANOVA, to

Lake Tanganyika; East Africa; Robert F. Swarthout Mentor; Catherine O'Reilly

154

Clinch River remedial investigation task 9 -- benthic macroinvertebrates  

Microsoft Academic Search

This report summarizes the results of Task 9 of the TVA\\/Department of Energy (DOE) Interagency Agreement supporting DOE`s Clinch River Remedial Investigation. Species lists and densities (numbers\\/m²) of benthic macroinvertebrates sampled at 16 sites in the Clinch River and Poplar Creek embayments of upper Watts Bar Reservoir near Oak Ridge, Tennessee, in March, 1994, are presented and briefly discussed. Data

E. M. Jr

1994-01-01

155

Declines in benthic macroinvertebrate populations in southern Lake Michigan  

Microsoft Academic Search

Abstract: Densities of the major benthic macroinvertebrate groups declined dramatically at sites shallower than 50 m in southern Lake Michigan between 1980 and 1993. Declines in Diporeia, Oligochaeta, and Sphaeriidae ranged from 40 to 75% at these depths. Total densities declined from 16 800·m, in 1980?1987. We hypothesize that the filtering activities of large populations of Dreissena polymorpha,in nearshore waters

Thomas F. Nalepa; David J. Hartson; David L. Fanslow; Gregory A. Lang; J. Lozano

156

Effects of an oil spill on benthic community production and respiration on subtropical intertidal sandflats.  

PubMed

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. PMID:23743269

Lee, Li-Hua; Lin, Hsing-Juh

2013-08-15

157

Modern benthic foraminifer distribution in the Amerasian Basin, Arctic Ocean  

USGS Publications Warehouse

A total of 38 box cores were collected from the Amerasian Basin, Arctic Ocean during the U.S. Geological Survey 1992 (PI92-AR) and 1993 (PI93-AR) Arctic Cruises aboard the U.S. Coast Guard Icebreaker Polar Star. In addition, the cruises collected geophysical data, piston cores and hydrographic data to address the geologic and oceanographic history of the western Arctic Ocean. This paper reports the results of the quantitative analyses of benthic foraminifer distribution data of the total (live + dead) assemblages derived from 22 box core-top samples. The results show that a distinct depth distribution of three dominant benthic foraminifer assemblages, the Textularia spp. - Spiroplectammina biformis, Cassidulina teretis and Oridorsalis tener - Eponides tumidulus Biofacies are strongly controlled by the dominant water masses within the Canada Basin: the Arctic Surface Water, Arctic Intermediate Water and Canada Basin Deep Water. The faunal distributions and their oceanographic associations in the Canada Basin are consistent with observations of benthic foraminifer distributions from other regions within the Arctic Ocean.

Ishman, S. E.; Foley, K. M.

1996-01-01

158

Improved oxygen isotope temperature calibrations for cosmopolitan benthic foraminifera  

NASA Astrophysics Data System (ADS)

Despite decades of use as a paleoceanographic proxy, considerable uncertainty still surrounds the temperature dependence of benthic foraminiferal ?18O. Widely applied paleotemperature equations may mix non-equilibrium foraminifera with equilibrium synthetic calcite, resulting in temperature sensitivities that are too large. Warm-water foraminiferal calibrations may give temperature sensitivities that are too small for very cold waters. Here we combine new core top measurements from the Florida Straits and the Arctic Ocean with published data to derive new ?18O:temperature relationships for three groups of benthic foraminifera. We derive a quadratic equation for Cibicidoides and Planulina that agrees well with equilibrium synthetic calcite, and that should be applicable over all oceanographic temperatures. We find that Uvigerina is not at equilibrium and is isotopically heavier than Cibicidoides and Planulina by 0.47‰, in contrast to the historically used 0.64‰. Hoeglundina elegans is further enriched and appears to be slightly heavier than equilibrium aragonite. Finally we discuss the implications of the Florida Straits observations for the hypothesis that benthic foraminifera precipitate their shells from a pH-dependent mixture of bicarbonate and carbonate ions.

Marchitto, T. M.; Curry, W. B.; Lynch-Stieglitz, J.; Bryan, S. P.; Cobb, K. M.; Lund, D. C.

2014-04-01

159

Sediment toxicity and benthic communities in mildly contaminated mudflats  

SciTech Connect

Sediment physicochemical characteristics, benthic community structure, and toxicity were measured at reference and contaminated intertidal mudflats around the North Island of New Zealand. Chronic whole-sediment toxicity tests were conducted with the estuarine amphipod, Chaetocorophium lucasi and the marine bivalve, Macomona lilana, and pore-water toxicity tests were conducted with embryos of the echinoid, Fellaster zelandiae. Although concentrations of organic chemicals and heavy metals were up to several orders of magnitude higher at the sites considered to be contaminated, levels of contamination were relatively low compared to internationally based sediment quality guidelines. Although no pronounced difference was found in benthic community structure between reference and contaminated sites, multivariate analysis indicated that natural sediment characteristics and factors related to contamination may have been affecting community structure. Although benthic effects caused by present levels of contamination are not yet dramatic, subtle changes in community structure related to pollution may be occurring. The two whole-sediment and the pore-water toxicity tests presented different response patterns. Growth of C. lucasi and M. liliana was a less sensitive endpoint than survival. None of the three toxicity tests responded more strongly to the contaminated than to the reference sites, that is, neither natural-sediment and pore-water characteristics nor unmeasured contaminants affected the test organisms. It is possible that sediment collection and handling may have induced chemical changes, confounding interpretation of toxicity tests.

Nipper, M.G.; Roper, D.S.; Williams, E.K.; Martin, M.L.; Van Dam, L.F.; Mills, G.N. [National Inst. of Water and Atmospheric Research Ltd., Hamilton (New Zealand)

1998-03-01

160

Factors affecting benthic impacts at Scottish fish farms.  

PubMed

The factors affecting patterns of benthic [seabed] biology and chemistry around 50 Scottish fish farms were investigated using linear mixed-effects models that account for inherent correlations between observations from the same farm. The abundance of benthic macrofauna and sediment concentrations of organic carbon were both influenced by a significant, albeit weak, interaction between farm size, defined as the maximum weight of fish permitted on site at any one time, and current speed. Above a farm size threshold of between 800 and 1000 t, the magnitude of effects at farms located in areas of elevated current speeds were greater than at equivalent farms located in more quiescent waters. Sediment concentrations of total organic matter were influenced by an interaction between distance and depth, indicating that wind-driven resuspension events may help reduce the accumulation of organic waste at farms located in shallow waters. The analyses presented here demonstrate that the production and subsequent fate of organic waste at fish farms is more complex than is often assumed; in isolation, current speed, water depth, and farr size are not necessarily good predictors of benthic impact. PMID:20178333

Mayor, Daniel J; Zuur, Alain F; Solan, Martin; Paton, Graeme I; Killham, Ken

2010-03-15

161

Impact of benthic disturbance on megafauna in Central Indian Basin  

NASA Astrophysics Data System (ADS)

Deep-sea photographs and video data were studied to evaluate the effects of benthic disturbance on megafaunal distribution in the Central Indian Basin. Xenophyophores (41%) and holothurians (30%) are the most abundant taxa, followed by other groups in the area before the disturbance. An overall reduction (32%) in the total megafaunal population after disturbance is direct evidence of the impact on benthic environment. Different groups such as xenophyophores, sea anemones, shrimps, starfish, brittle stars, holothurians and fish show different degrees of reduction (21-48%) in their numbers, depending upon their ability to withstand increased turbidity and sedimentation rates due to disturbance. Faunal groups such as protobranch molluscs, polychaete worms, seafans and squids, observed before the disturbance, were not seen after disturbance, whereas populations of some taxa increased after the disturbance. Increased numbers of mobile taxa could be due to increased levels of organic carbon due to resedimentation, whereas increase in sessile taxa may partly reflect the difficulty in distinguishing live from dead specimens. The impact on faunal assemblages is more severe in the disturbed area than the undisturbed area. Our results indicate that monitoring of megafauna can be used effectively to evaluate the potential impacts of large-scale mining or other disturbance on the seafloor, and may therefore help in developing measures for conservation of the benthic environment.

Rodrigues, Nimi; Sharma, Rahul; Nagender Nath, B.

162

Pelagic-Benthic Coupling of Nucleic Acids in an Abyssal Location of the Northeastern Atlantic Ocean  

PubMed Central

Spatial and temporal changes in sedimentary nucleic acid concentrations in an abyssal locality of the northeastern Atlantic Ocean were investigated in relation to fluxes of nucleic acids produced in the photic layer. Sediment trap material, collected between 1996 and 1998 at depths of 1,000, 3,000, and 4,700 m, and sediment samples were analyzed for DNA and RNA content. Nucleic acid concentrations in the sediments were very high and displayed significant temporal changes, whereas mesoscale variability was low. DNA and RNA concentrations generally displayed opposite temporal patterns, which are likely to be dependent on the nature and characteristics of DNA and RNA molecules. Nucleic acid fluxes were high and displayed clear seasonal changes apparently coupled with seasonal pulses of primary production. However, while median values of DNA fluxes were relatively similar in all sediment traps, median values of RNA fluxes almost doubled from the 1,000- to the 4,700-m depth, suggesting differences in the metabolic activity of microbes associated with sinking particles. Significant relationships between DNA concentrations in the sediments and DNA fluxes and between RNA concentrations and RNA fluxes, indicating the presence of a clear pelagic-benthic coupling of particulate nucleic acids, were observed. The benthic system investigated was not steady state since we estimated that, from September 1996 to October 1998, nucleic acid concentration in the sediments decreased by about 165 mg of DNA m?2. Vertical profiles revealed a significant decrease in DNA concentration with depth in the sediments, reaching an asymptotic value of about 5 ?g g?1. This DNA fraction constitutes a pool of potentially refractory DNA (accounting for 16 to 40% of the total DNA pool) that might be buried in the sediments.

Dell'Anno, A.; Fabiano, M.; Mei, M. L.; Danovaro, R.

1999-01-01

163

Spectral reflectance of carbonate sediments and application to remote sensing classification of benthic habitats  

NASA Astrophysics Data System (ADS)

Remote sensing is a valuable tool in marine research that has advanced to the point that images from shallow waters can be used to identify different seafloor types and create maps of benthic habitats. A major goal of this dissertation is to examine differences in spectral reflectance and create new methods of analyzing shallow water remote sensing data to identify different seafloor types quickly and accurately. Carbonate sediments were used as a model system as they presented a relatively uniform, smooth surface for measurement and are a major bottom type in tropical coral reef systems. Experimental results found that sediment reflectance varied in shape and magnitude depending on pigment content, but only varied in magnitude with variations in grain size and shape. Derivative analysis of the reflectance spectra identified wavelength regions that correlate to chlorophyll a and chlorophyllide a as well as accessory pigments, indicating differences in microbial community structure. Derivative peak height also correlated to pigment content in the sediments. In remote sensing data, chlorophyll a, chlorophyllide a, and some xanthophylls were identified in derivative spectra and could be quantified from second derivative peak height. Most accessory pigments were attenuated by the water column, however, and could not be used to quantify pigments in sediments from remote sensing images. Radiative transfer modeling of remote sensing reflectance showed that there was sufficient spectral variation to separate major sediment types, such as ooid shoals and sediment with microbial layers, from different densities of seagrass and pavement bottom communities. Both supervised classification with a spectral library and unsupervised classification with principal component analysis were used to create maps of seafloor type. The results of the experiments were promising; classified seafloor types correlated with ground truth observations taken from underwater video and were comparable to existing maps of seafloor type. Creation of accurate seafloor type maps is an important step in constructing maps of benthic habitats.

Louchard, Eric Michael

164

Refinement, validation, and application of a benthic condition index for Northern Gulf of Mexico estuaries  

Microsoft Academic Search

By applying discriminant analysis to benthic macroinvertebrate data, we have developed an indicator of benthic condition for\\u000a northern Gulf of Mexico estuaries. The data used were collected by the United states Environmental Protection Agency’s Environmental\\u000a Monitoring and Assessment Program (EMAP) in the Louisianian Province from 1991 to 1994. This benthic index represents a linear\\u000a combination of the following weighted parameters:

Virginia D. Engle; J. Kevin Summers

1999-01-01

165

The control of the development of a marine benthic community by predation on recruits  

Microsoft Academic Search

Recruitment is an important process in regulating many marine benthic communities and many studies have examined factors controlling the dispersal and distribution of larval immigrants. However, benthic species also have early post-settlement life-stages that are dramatically different from adult and larval stages. Predation on these stages potentially impacts measured recruitment and the benthic populations and communities that ultimately develop.We examined

Richard W. Osman; Robert B. Whitlatch

2004-01-01

166

On relating physical limits to the carbon: nitrogen ratio of unicellular algae and benthic plants  

Microsoft Academic Search

Unicellular algae such as phytoplankton and benthic microalgae have an elemental ratio of carbon to nitrogen to phosphorus (C\\/N\\/P) of approximately 106:16:1, known as the Redfield ratio. Benthic plants, including benthic macroalgae and seagrass, have a significantly different and more variable C\\/N\\/P ratio, with a median of 550:30:1, herein called the Atkinson ratio. In this paper, the implications of physically

Mark E. Baird; Jason H. Middleton

2004-01-01

167

Do benthic biofilters contribute to sustainability and restoration of the benthic environment impacted by offshore cage finfish aquaculture?  

PubMed

Benthic biofilters were deployed under a cage fish farm and in two reference locations to assess the influence of the farm on the biofilters and the surroundings, as well as to verify the usefulness of this technology as a mitigation tool. The biofilters underneath the farm recruited a fouling community practically identical to that of the control biofilters, which included a variety of trophic strategies. The former showed a higher 15N enrichment, indicating that fouling beneath the farm was benefiting from the farm waste. The waste retention efficiency was low (0.02 g N m(-2) month(-1)) beneath the farm. Benthic biofilters aggregated demersal wild fish around and within them. Pelagic wild fish also frequently used the biofilters beneath the farm, forming compact shoals around them. The increased complexity of the habitat below the fish farm enhanced biodiversity, but this improvement did not lead to the recovery of the sediments around the biofilters. PMID:21669446

Aguado-Giménez, F; Piedecausa, M A; Carrasco, C; Gutiérrez, J M; Aliaga, V; García-García, B

2011-08-01

168

Benthic production and processes off Baja California, northwest Africa and Peru: a classification of benthic subsystems in upwelling ecosystems  

SciTech Connect

Estimates of the standing stocks, secondary production and metabolism of the benthos have been compared in the coastal upwelling ecosystems off northwest Africa, Baja California, and southern Peru. Northwest Africa is characterized by shelf break upwelling and as a result standing stocks, macrobenthic production and sediment organic matter are highest out at the shelf-slope boundary. Sediment microbial activity and biomass on the other hand are highest nearshore in the dynamic zone where aeolian silt and sand are being blown into the sea from the Sahara Desert. Baja California is dominated by the red crab, Pleuroncodes planipes, having high rates of growth and metabolic utilization of organic matter, both on bottom and in the water. Peru benthos and metabolism are very different from the above areas because of the low oxygen concentrations in the bottom water. Organic matter is far higher in the sediment and heterotrophic metabolism is principally anaerobic rather than aerobic. A normal offshore benthic fauna is replaced by a mat of sulfur bacteria with unknown production and metabolic rates. Benthic subsystems in upwelling ecosystems can be placed in two categories: those overloaded with organic matter, depleted of oxygen and dominated by sulfate reduction and those that are not overloaded and remain aerobic. Peru and southwest Africa typify overloaded systems whereas NW Africa and Baja California are examples of aerobic systems. Although benthic metabolism and ionorganic nutrient regeneration are high in both types of subsystems, all upwelling ecosystems, with their dynamic open boundaries, export organic particulate matter and import inorganic nutrients at rates that are far in excess of that consumed or produced by benthic metabolism. 42 refs., 7 figs., 8 tabs.

Rowe, G.T.

1983-01-01

169

BENTHIC MACROINVERTEBRATES AS INDICATORS OF ENVIRONMENTAL CONDITION IN THREE GREAT LAKES  

EPA Science Inventory

Biological, physical, and chemical data were collected from surficial sediments of Lakes Ontario, Michigan, and Superior to examine benthic macroinvertebrate community structure as an indicator of environmental condition....

170

Benthic habitat characterisation of soft-bottom continental shelves: Integration of acoustic surveys, benthic samples and trawling disturbance intensity  

NASA Astrophysics Data System (ADS)

Eleven sites were located on Mediterranean continental shelves to explore the link between the physical characteristics and epibenthic fauna from soft-sediment habitats. These sites, at 32-82 m in depth, were associated with fishing grounds and the trawling intensity was estimated at the site scale to assess the effects of trawling on benthic communities. Each site was surveyed with Multi-Beam (bathymetry and backscatter), side-scan sonar, benthic grabs and a surface dredge. The sites were clustered in three habitat types. Habitat 1, with moderate trawling disturbance, was characterised by homogeneous mud and associated epifauna that was also highly homogeneous across sites. Habitat 2, with sandy mud and scattered gravel and rocks, had a high abundance of sessile suspension feeders that probably attach to the coarser substratum and benefit from the low fishing disturbance in these sites. Habitat 3 included sites with heterogeneous sediments with maërl as the prevailing biocenosis and having the highest species richness, despite being subjected to variable trawling intensity. Statistical models were used to relate environmental parameters and the species abundance. More than 3 physical variables were necessary to explain the epifaunal patterns across sites, including the percentage of mud, sediment heterogeneity and fishing effort. These analyses are an essential step for extrapolating information from benthic samples to the larger scale of habitats, mapped through acoustic surveys. Despite this, a good integration is required between the mapping of physical habitat distribution and the ecological knowledge of communities.

de Juan, S.; Lo Iacono, C.; Demestre, M.

2013-01-01

171

A Servicewide Benthic Mapping Program for National Parks  

USGS Publications Warehouse

In 2007, the National Park Service (NPS) Inventory and Monitoring Program directed the initiation of a benthic habitat mapping program in ocean and coastal parks in alignment with the NPS Ocean Park Stewardship 2007-2008 Action Plan. With 74 ocean and Great Lakes parks stretching over more than 5,000 miles of coastline across 26 States and territories, this Servicewide Benthic Mapping Program (SBMP) is essential. This program will deliver benthic habitat maps and their associated inventory reports to NPS managers in a consistent, servicewide format to support informed management and protection of 3 million acres of submerged National Park System natural and cultural resources. The NPS and the U.S. Geological Survey (USGS) convened a workshop June 3-5, 2008, in Lakewood, Colo., to discuss the goals and develop the design of the NPS SBMP with an assembly of experts (Moses and others, 2010) who identified park needs and suggested best practices for inventory and mapping of bathymetry, benthic cover, geology, geomorphology, and some water-column properties. The recommended SBMP protocols include servicewide standards (such as gap analysis, minimum accuracy, final products) as well as standards that can be adapted to fit network and park unit needs (for example, minimum mapping unit, mapping priorities). SBMP Mapping Process. The SBMP calls for a multi-step mapping process for each park, beginning with a gap assessment and data mining to determine data resources and needs. An interagency announcement of intent to acquire new data will provide opportunities to leverage partnerships. Prior to new data acquisition, all involved parties should be included in a scoping meeting held at network scale. Data collection will be followed by processing and interpretation, and finally expert review and publication. After publication, all digital materials will be archived in a common format. SBMP Classification Scheme. The SBMP will map using the Coastal and Marine Ecological Classification Standard (CMECS) that is being modified to include all NPS needs, such as lacustrine ecosystems and submerged cultural resources. CMECS Version III (Madden and others, 2010) includes components for water column, biotic cover, surface geology, sub-benthic, and geoform. SBMP Data Archiving. The SBMP calls for the storage of all raw data and final products in common-use data formats. The concept of 'collect once, use often' is essential to efficient use of mapping resources. Data should also be shared with other agencies and the public through various digital clearing houses, such as Geospatial One-Stop (http://gos2.geodata.gov/wps/portal/gos). To be most useful for managing submerged resources, the SBMP advocates the inventory and mapping of the five components of marine ecosystems: surface geology, biotic cover, geoform, sub-benthic, and water column. A complete benthic inventory of a park would include maps of bathymetry and the five components of CMECS. The completion of mapping for any set of components, such as bathymetry and surface geology, or a particular theme (for example, submerged aquatic vegetation) should also include a printed report.

Moses, Christopher S.; Nayegandhi, Amar; Beavers, Rebecca; Brock, John

2010-01-01

172

Application of Multiple Index Development Approaches to Benthic Invertebrate Data from the Virginian Biogeographic Province (SETAC NA)  

EPA Science Inventory

Benthic invertebrate indices have commonly been utilized to assess benthic invertebrate communities. These indices have been constructed using different techniques, but have shown different levels of application success. For example, the EMAP Virginian Province Index did not pe...

173

Antarctic Porifera database from the Spanish benthic expeditions  

PubMed Central

Abstract The information about the sponges in this dataset is derived from the samples collected during five Spanish Antarctic expeditions: Bentart 94, Bentart 95, Gebrap 96, Ciemar 99/00 and Bentart 2003. Samples were collected in the Antarctic Peninsula and Bellingshausen Sea at depths ranging from 4 to 2044 m using various sampling gears. The Antarctic Porifera database from the Spanish benthic expeditions is unique as it provides information for an under-explored region of the Southern Ocean (Bellingshausen Sea). It fills an information gap on Antarctic deep-sea sponges, for which there were previously very few data. This phylum is an important part of the Antarctic biota and plays a key role in the structure of the Antarctic marine benthic community due to its considerable diversity and predominance in different areas. It is often a dominant component of Southern Ocean benthic communities. The quality of the data was controlled very thoroughly with GPS systems onboard the R/V Hesperides and by checking the data against the World Porifera Database (which is part of the World Register of Marine Species, WoRMS). The data are therefore fit for completing checklists, inclusion in biodiversity pattern analysis and niche modelling. The authors can be contacted if any additional information is needed before carrying out detailed biodiversity or biogeographic studies. The dataset currently contains 767 occurrence data items that have been checked for systematic reliability. This database is not yet complete and the collection is growing. Specimens are stored in the author’s collection at the Spanish Institute of Oceanography (IEO) in the city of Gijón (Spain). The data are available in GBIF.

Rios, Pilar; Cristobo, Javier

2014-01-01

174

Benthic Foraminifer Nd Isotopes and Radiocarbon: a Preliminary Study  

NASA Astrophysics Data System (ADS)

The combined analysis of neodymium (Nd) isotopes and radiocarbon (14C) in sedimentary benthic foraminifera has the potential to remedy a major issue involved in the interpretation of 14C data. The problem is that changes in deep-water sourcing, deep-water source signature and deep-water renewal rates may all affect 14C concentration, complicating the interpretation of deep-water 14C reconstructions. To overcome this, the application of a circulation tracer is required. Traditional proxies such as ?13C, Cd/Ca, and deep-water temperature either do not behave as conservative tracers or only indirectly represent water mass mixing, and so are of limited use1. The application of a more recently developed proxy for water mass sourcing, circulation and mixing, Nd isotopes, might offer a solution to this problem. A recent pioneering study2 has demonstrated that sedimentary benthic foraminifera might be a suitable archive of past deep-water Nd isotope composition at high resolution, potentially more robust than acidic-reductive sediment leach data. This study seeks to utilise this promising new tracer by applying it to an investigation of deglacial ventilation changes in the North Atlantic. Initial data presented here for core-top benthic foraminifera from the Labrador Sea, Iberian Margin and Pacific illustrate nearly the complete dynamic range of Nd isotope compositions present in the modern ocean, in general agreement with existing seawater Nd isotope data. Preliminary down-core Nd isotope data from the Iberian Margin place initial constraints on the contribution of deep-water sourcing to observed changes in deep-water 14C ventilation across the last deglaciation. 1 - E. Boyle, Ann. Rev. Earth Planet. Sci. 20, 245-287 (1992) 2 - V. Klevenz et al., Earth Planet. Sci. Lett. 265, 571-587 (2008)

Scrivner, A. E.; Skinner, L. C.

2008-12-01

175

Dispersal, survival and delayed growth of benthic foraminiferal propagules  

NASA Astrophysics Data System (ADS)

New data support our previously published propagule dispersal hypothesis and show that propagules of some benthic foraminiferal species can survive for two years before growth commences. Following exposure to simulated shallow-water conditions, shallow-water species of benthic foraminifera appeared and grew in large numbers (commonly >100 ind/12 ml sediment) in the <32 µm-size sediment fraction collected from 320 m water depth in the Skagerrak basin (North Sea). None of the shallow-water species that grew abundantly ( Planorbulina mediterranensis, Morulaeplecta bulbosa, Bolivina pseudoplicata, Cuneata arctica, Eggerelloides scaber, Gavelinopsis praegeri) seem to grow or reproduce at or in the vicinity of the sampling site. Consequently, they must have been transported there as <32 µm-sized individuals. Their sudden appearance when exposed to shallow-water conditions suggests that they had been transported to the sampling site as propagules and that they could survive in the sediments until conditions became suitable for growth and, for some, reproduction. The lack of agglutination on the proloculi of the agglutinated taxa that appeared in the growth-chambers may enhance their passive transport via currents and, thereby, dispersal. Of all the indigenous foraminiferal species that occur at the sampling site, only Textularia earlandi and Bolivinellina pseudopunctata continued to grow and reproduce when transferred from bathyal (320 m) to simulated shallow-water (0 m) conditions. The former is considered a highly opportunistic species. According to the literature, most of the morphospecies which grew in the experiments are cosmopolitan. Our results indicate substantial inter-specific differences in dispersal potential and support previous suggestions that among free-living species, some serial forms have the potential for long-distance dispersal. Still, oceanographic, physical and ecological boundaries and barriers constrain the distribution of most species. In addition to benthic foraminifera, Gromia spp. (rhizarian protists related to the foraminifera) grew in >60% of the experimental growth-chambers.

Alve, Elisabeth; Goldstein, Susan T.

2010-01-01

176

Benthic macroinvertebrate richness along Sausal Creek, Oakland, California  

NASA Astrophysics Data System (ADS)

Sausal Creek, 5.0 km long, is one of the principal watercourses in Oakland, California. The headwaters of Sausal Creek arise in the Oakland Hills and the creek flows southwestward through the city, discharging into the tidal canal that separates the island of Alameda from Oakland; the creek ultimately flows into San Francisco Bay. Due to the presence of rainbow trout, the stream health of Sausal Creek is a local conservation priority. In the present study, a survey of benthic macroinvertebrates in the creek was conducted and possible correlations between environmental variables and taxonomic richness were analyzed. Three stations along the creek were sampled using a 30.5cm 500 micron aquatic d-net, and temperature, pH and dissolved oxygen levels were measured in creek samples obtained at each station. Temperature, pH and dissolved oxygen levels remained constant along the creek. Taxonomic richness was highest at the upstream site of Palo Seco, located in an eastern section of the creek, and furthest downstream at Dimond Park, in the western portion of the creek. The Monterrey site, just west of Palo Seco was found to be significantly low in benthic macroinvertebrates. The Palo Seco and Monterrey sites are separated by Highway 13 and storm drain inputs may bring contaminants into the creek at this site. At the Monterrey site Sausal Creek follows the Hayward Fault, gas emissions or change in substrate may also affect the local population of benthic invertebrates. Further research will be conducted to determine what factors are contributing to this local anomaly.

Lara, D.; Ahumada, E.; Leon, Y.; Bracho, H.; Telles, C.

2012-12-01

177

Disturbance, colonization and development of Antarctic benthic communities  

PubMed Central

A decade has yielded much progress in understanding polar disturbance and community recovery—mainly through quantifying ice scour rates, other disturbance levels, larval abundance and diversity, colonization rates and response of benthos to predicted climate change. The continental shelf around Antarctica is clearly subject to massive disturbance, but remarkably across so many scales. In summer, millions of icebergs from sizes smaller than cars to larger than countries ground out and gouge the sea floor and crush the benthic communities there, while the highest wind speeds create the highest waves to pound the coast. In winter, the calm associated with the sea surface freezing creates the clearest marine water in the world. But in winter, an ice foot encases coastal life and anchor ice rips benthos from the sea floor. Over tens and hundreds of thousands of years, glaciations have done the same on continental scales—ice sheets have bulldozed the seabed and the zoobenthos to edge of shelves. We detail and rank modern disturbance levels (from most to least): ice; asteroid impacts; sediment instability; wind/wave action; pollution; UV irradiation; volcanism; trawling; non-indigenous species; freshwater inundation; and temperature stress. Benthic organisms have had to recolonize local scourings and continental shelves repeatedly, yet a decade of studies have demonstrated that they have (compared with lower latitudes) slow tempos of reproduction, colonization and growth. Despite massive disturbance levels and slow recolonization potential, the Antarctic shelf has a much richer fauna than would be expected for its area. Now, West Antarctica is among the fastest warming regions and its organisms face new rapid changes. In the next century, temperature stress and non-indigenous species will drastically rise to become dominant disturbances to the Antarctic life. Here, we describe the potential for benthic organisms to respond to disturbance, focusing particularly on what we know now that we did not a decade ago.

Barnes, David K.A; Conlan, Kathleen E

2006-01-01

178

Deep-sea benthic footprint of the deepwater horizon blowout.  

PubMed

The Deepwater Horizon (DWH) accident in the northern Gulf of Mexico occurred on April 20, 2010 at a water depth of 1525 meters, and a deep-sea plume was detected within one month. Oil contacted and persisted in parts of the bottom of the deep-sea in the Gulf of Mexico. As part of the response to the accident, monitoring cruises were deployed in fall 2010 to measure potential impacts on the two main soft-bottom benthic invertebrate groups: macrofauna and meiofauna. Sediment was collected using a multicorer so that samples for chemical, physical and biological analyses could be taken simultaneously and analyzed using multivariate methods. The footprint of the oil spill was identified by creating a new variable with principal components analysis where the first factor was indicative of the oil spill impacts and this new variable mapped in a geographic information system to identify the area of the oil spill footprint. The most severe relative reduction of faunal abundance and diversity extended to 3 km from the wellhead in all directions covering an area about 24 km(2). Moderate impacts were observed up to 17 km towards the southwest and 8.5 km towards the northeast of the wellhead, covering an area 148 km(2). Benthic effects were correlated to total petroleum hydrocarbon, polycyclic aromatic hydrocarbons and barium concentrations, and distance to the wellhead; but not distance to hydrocarbon seeps. Thus, benthic effects are more likely due to the oil spill, and not natural hydrocarbon seepage. Recovery rates in the deep sea are likely to be slow, on the order of decades or longer. PMID:23950956

Montagna, Paul A; Baguley, Jeffrey G; Cooksey, Cynthia; Hartwell, Ian; Hyde, Larry J; Hyland, Jeffrey L; Kalke, Richard D; Kracker, Laura M; Reuscher, Michael; Rhodes, Adelaide C E

2013-01-01

179

Deep-Sea Benthic Footprint of the Deepwater Horizon Blowout  

PubMed Central

The Deepwater Horizon (DWH) accident in the northern Gulf of Mexico occurred on April 20, 2010 at a water depth of 1525 meters, and a deep-sea plume was detected within one month. Oil contacted and persisted in parts of the bottom of the deep-sea in the Gulf of Mexico. As part of the response to the accident, monitoring cruises were deployed in fall 2010 to measure potential impacts on the two main soft-bottom benthic invertebrate groups: macrofauna and meiofauna. Sediment was collected using a multicorer so that samples for chemical, physical and biological analyses could be taken simultaneously and analyzed using multivariate methods. The footprint of the oil spill was identified by creating a new variable with principal components analysis where the first factor was indicative of the oil spill impacts and this new variable mapped in a geographic information system to identify the area of the oil spill footprint. The most severe relative reduction of faunal abundance and diversity extended to 3 km from the wellhead in all directions covering an area about 24 km2. Moderate impacts were observed up to 17 km towards the southwest and 8.5 km towards the northeast of the wellhead, covering an area 148 km2. Benthic effects were correlated to total petroleum hydrocarbon, polycyclic aromatic hydrocarbons and barium concentrations, and distance to the wellhead; but not distance to hydrocarbon seeps. Thus, benthic effects are more likely due to the oil spill, and not natural hydrocarbon seepage. Recovery rates in the deep sea are likely to be slow, on the order of decades or longer.

Montagna, Paul A.; Baguley, Jeffrey G.; Cooksey, Cynthia; Hartwell, Ian; Hyde, Larry J.; Hyland, Jeffrey L.; Kalke, Richard D.; Kracker, Laura M.; Reuscher, Michael; Rhodes, Adelaide C. E.

2013-01-01

180

Organic matter and benthic metabolism in Lake Illawarra, Australia  

NASA Astrophysics Data System (ADS)

Carbon and nitrogen contents (total organic carbon and total nitrogen), chlorophyll-a concentrations in surface sediments and benthic sediment-water fluxes of oxygen and carbon dioxide were investigated at five stations in Lake Illawarra (Australia) to compare the sources/quality of sedimentary organic matter and the characteristics of diagenesis and benthic biogeochemical processes for different primary producers (e.g., seagrass, microphytobenthos and macroalgae) and/or sediment types (sand or mud). The unvegetated sediments showed lower C/N ratios (with the lowest value occurring in the deep organic-rich muddy site) than the seagrass ( Ruppia or Zostera) beds, which may be due to the contribution of microalgae (mainly diatoms) to the sedimentary organic matter pool. This was also supported by the detection of microalgal pigments in the bare sediments. On an annual basis, seagrass beds exhibited the highest gross primary productivity (O 2 or TCO 2 fluxes), while the lowest rates occurred in the deep central basin of the Lake. Seasonally, there was a general trend of highest production in spring or summer, and lowest production in winter or autumn. Organic carbon oxidation scenarios, evaluated by either calcium carbonate dissolution or sulfate reduction models, indicated that both models can explain organic matter mineralization. Trophic status was evaluated using different indices including benthic trophic state index, net O 2 fluxes and P/ R ratios for Lake Illawarra, which led to similar trophic classifications in general, and also the same trends in spatial and seasonal variations. Overall, these data indicated that the Lake was heterotrophic on an annual basis, as the total community carbon respiration exceeded production, and this supported an earlier LOICZ mass balance/stoichiometric modelling conclusion.

Qu, Wenchuan; Morrison, R. J.; West, R. J.; Su, Chenwei

2006-10-01

181

DEVELOPMENT OF AN INDEX OF BENTHIC CONDITION FOR COASTAL AREAS OF THE GULF OF MAINE  

EPA Science Inventory

The National Coastal Assessment has sampled benthic assemblages each summer since 2000 in coastal areas of the U.S. Gulf of Maine. We are developing a multimetric index to be used as an indicator of benthic condition for both spatial comparisons of condition along the coast and f...

182

DEVELOPING AND INDEX OF BENTHIC CONDITION FOR THE ACADIAN BIOGEOGRAPHIC PROVINCE  

EPA Science Inventory

The National Coastal Assessment has sampled benthic assemblages each summer since 2000 in coastal areas of the U.S. Acadian Biogeographic Province (tip of Cape Cod to Canadian border). We are developing a multimetric index to be used as an indicator of benthic condition. During...

183

Primary Production of Benthic Microalgae in the Oosterschelde Estuary (S. W. Netherlands).  

National Technical Information Service (NTIS)

The role of benthic micro-algae, primary producers on the intertidal areas of the Oosterschelde, has been studied during 1985 to 1986. To quantify benthic primary production microscale measurements of oxygen production and pH were performed in situ. Five ...

S. A. De Jong P. A. G. Hofman A. J. J. Sandee E. J. Wagenvoort

1990-01-01

184

Structural responses of benthic macroinvertebrate communities from different stream orders to zinc  

Microsoft Academic Search

It is well established that benthic invertebrate community structure and function shift in a predictable fashion along longitudinal stream gradients as a result of variation in environmental conditions. The authors research is concerned with experimentally testing whether this shift in community structure influences the response of benthic macroinvertebrates to heavy metals. Using artificial streams, they compared effects of Zn on

Peter M. Kiffney; William H. Clements

1994-01-01

185

The benthic biological submodel in the European regional seas ecosystem model  

Microsoft Academic Search

The submodel describing benthic biology including a bioturbation module as incorporated in the European Regional Seas Ecosystem Model (ERSEM) is discussed. It is linked to a nutrient dynamic model. The structure of the benthic model food web is presented. There are four macrobenthic functional groups, meiobenthos and aerobic and anaerobic bacteria. The modelling uses ‘standard organisms’ as basic building blocks.

W. Ebenhöh; C. Kohlmeier; P. J. Radford

1995-01-01

186

MARYLAND DEPARTMENT OF THE ENVIRONMENT NON-TIDAL BENTHIC MACROINVERTEBRATE MONITORING PROGRAM  

EPA Science Inventory

The Maryland Non-tidal Benthic Macroinvertebrate Monitoring Program provides data on benthic macroinvertebrates for many streams in the state. Through it, an entire network of 100 stations in the nontidal reaches of Marylands Chesapeake Bay Basin are sampled within a two year per...

187

IMPORTANCE OF PHYSICAL SCALING FACTORS TO BENTHIC MARINE INVERTEBRATE RECOLONIZATION OF LABORATORY MICROCOSMS  

EPA Science Inventory

Five laboratory studies of benthic macroinvertebrate recolonization were conducted for 6-wk periods to evaluate the effects of physical factors (i.e., microcosm size, seawater flow rates and sediment depth) on benthic community structure. esign variables included4 open-faced acry...

188

MIDDLE REACH OF THE SNAKE RIVER: WATER QUALITY AND BENTHIC BIOMONITORING  

EPA Science Inventory

This study examined spatial and temporal trends in water quality, sestonic and benthic algal concentrations, and benthic macroinvertebrate taxa richness, population density, and biomass at nine stations along the Middle Snake River from Pillar Falls to Upper Salmon Falls Dam. Pri...

189

Refinement, validation, and application of a benthic condition index for northern Gulf of Mexico estuaries  

USGS Publications Warehouse

By applying discriminant analysis to benthic macroinvertebrate data, we have developed an indicator of benthic condition for northern Gulf of Mexico estuaries. The data used were collected by the United States Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) in the Louisianian Province from 1991 to 1994. This benthic index represents a linear combination of the following weighted parameters: the proportion of expected species diversity, the mean abundance of tubificid oligochaetes, the percent of total abundance represented by capitellid polychaetes, the percent of total abundance represented by bivalve mollusks, and the percent of total abundance represented by amphipods. We successfully validated and retrospectively applied the benthic index to all of the benthic data collected by EMAP in the Louisianian Province. This benthic index was also calculated for independent data collected from Pensacola Bay, Florida, in order to demonstrate its flexibility and applicability to different estuarine systems within the same biogeographic region. The benthic index is a useful and valid indicator of estuarine condition that is intended to provide environmental managers with a simple tool for assessing the health of benthic macroinvertebrate communities.

Engle, V. D.; Summers, J. K.

1999-01-01

190

Benthic invertebrates investigation in the East River and habitat restoration strategies  

Microsoft Academic Search

The stream ecology of the East River is studied using benthic macro-invertebrates as indicator species. Samples were taken from 12 selected sites with different environmental conditions, from the upper reaches to the lower reaches. Four sites were selected to assess restoration strategies. The taxon richness, number density, biodiversity, and bio-community indices of benthic invertebrates remain at a relatively high level

Zhao-Yin Wang; Joseph H. W. Lee; Dongsheng Cheng; Xuehua Duan

2008-01-01

191

Spatial distribution of benthic microalgae on coral reefs determined by remote sensing  

Microsoft Academic Search

Understanding the ecological role of benthic microalgae, a highly productive component of coral reef ecosystems, requires information on their spatial distribution. The spatial extent of benthic microalgae on Heron Reef (southern Great Barrier Reef, Australia) was mapped using data from the Landsat 5 Thematic Mapper sensor, integrated with field measurements of sediment chlorophyll concentration and reflectance. Field-measured sediment chlorophyll concentrations,

Chris M. Roelfsema; S. R. Phinn; W. Dennison

2002-01-01

192

Quantitative evidence concerning the stabilization of sediments by marine benthic diatoms  

Microsoft Academic Search

Six species of benthic diatoms and a natural benthic diatom community were cultured in flasks on a variety of sediments. Diatom species which secreted large quantities of mucilage were effective sediment stabilizers. These mucilage-secreting species significantly reduced resuspension and retarded laminar flow of the sediments when the culture flasks were agitated. Diatom species which secreted little or no mucilage were

A. F. Holland; R. G. Zingmark; J. M. Dean

1974-01-01

193

Benthic foraminifera (protista) as tools in deep-water palaeoceanography: Environmental influences on faunal characteristics  

Microsoft Academic Search

Foraminiferal research lies at the border between geology and biology. Benthic foraminifera are a major component of marine communities, highly sensitive to environmental influences, and the most abundant Benthic organisms preserved in the deep-sea fossil record. These characteristics make them important tools for reconstructing ancient oceans. Much of the recent work concerns the search for palaeoceanographic proxies, particularly for the

Andrew J. Gooday

2003-01-01

194

Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records  

Microsoft Academic Search

We show that robust regressions can be established between relative sea-level (RSL) data and benthic foraminifera oxygen isotopic ratios from the North Atlantic and Equatorial Pacific Ocean over the last climatic cycle. We then apply these regressions to long benthic isotopic records retrieved at one North Atlantic and one Equatorial Pacific site to build a composite RSL curve, as well

C. Waelbroeck; L. Labeyrie; E. Michel; J. C. Duplessy; J. F. McManus; K. Lambeck; E. Balbon; M. Labracherie

2002-01-01

195

Effects of floods on epilithon and benthic macroinvertebrate populations in an unstable New Zealand river  

Microsoft Academic Search

Temporal changes in epilithon biomass and benthic macroinvertebrate density were investigated in the Ashley River, a flood-prone river with an unpredictable discharge regime. Biomass, primary production and respiration of the epilithic community were highest in spring when filamentous algae were present and lowest following two large floods that occurred in close succession. Sixty invertebrate species were taken in benthic samples

Garry J. Scrimgeour; Michael J. Winterbourn

1989-01-01

196

A Study of the Impact of a Pipeline Construction on Estuarine Benthic Invertebrate Communities  

Microsoft Academic Search

The effects of a pipeline construction on benthic invertebrates were investigated using a Before\\/After impact protocol at Clonakilty Bay, West Cork, Ireland. Benthic invertebrates were sampled once before the excavation and at one, two, three and six months after the completion of the work. Analysis was designed to compare natural variation over time within control sites with the variation that

L. J. Lewis; J. Davenport; T. C. Kelly

2002-01-01

197

A survey of the benthic microfauna (foraminifera, Ostracoda) on the Basque shelf, southern Bay of Biscay  

Microsoft Academic Search

In this work we describe by the first time the microfaunal content (foraminifers and ostracods) of the benthos of the Basque continental shelf, by studying the spatial distributions of benthic foraminifer and ostracod assemblages in relation to the environmental parameters affecting the sediments of this region of the Bay of Biscay. Most abundant benthic foraminifer species in the surface samples

Ana Pascual; Julio Rodriguez-Lazaro; Maite Martín-Rubio; Jean-Marie Jouanneau; Olivier Weber

2008-01-01

198

A MORE COST-EFFECTIVE EMAP-W BENTHIC MACROFAUNAL SAMPLE UNIT  

EPA Science Inventory

The standard EPA West Coast Environmental Monitoring and Assessment Program (EMAP-W) benthic macrofaunal sampling protocol is to collect 30-50 random benthic samples per reporting unit (e.g., estuary, region) using a 0.1 m2 grab and to sort out macrofauna using a 1.0 mm mesh scre...

199

A MORE COST-EFFECTIVE EMAP-ESTUARIES BENTHIC MACROFAUNAL SAMPLING PROTOCOL  

EPA Science Inventory

The standard benthic macrofaunal sampling protocol in the U.S. Environmental Protection Agency's Pacific Coast Environmental Monitoring and Assessment Program (EMAP) is to collect a minimum of 30 random benthic samples per reporting unit (e.g., estuary) using a 0.1 m2 grab and to...

200

Benthic-pelagic interactions in shallow water columns: an experimentalist's perspective  

Microsoft Academic Search

Shallow water column benthic and pelagic communities are thought to be linked by trophic relationships, through life history or ontogenetic links, and by biologically or physically-mediated resuspension or sedimentation processes. It is often confusing and sometimes misleading to focus only on benthic or only on pelagic components of aquatic food webs, even though the literature on shallow water column experiments

Stephen T. Threlkeld

1994-01-01

201

Effects of Karenia brevis on clearance rates and bioaccumulation of brevetoxins in benthic suspension feeding invertebrates  

Microsoft Academic Search

Blooms of the toxic alga Karenia brevis occur along coastlines where sessile suspension feeding invertebrates are common components of benthic communities. We studied the effects of K. brevis on four benthic suspension feeding invertebrates common to the coast of the SE United States: the sponge Haliclona tubifera, the bryozoan Bugula neritina, the bivalve Mercenaria mercenaria, and the tunicate Styela plicata.

Michael Echevarria; Jerome P. Naar; Carmelo Tomas; Joseph R. Pawlik

202

The Benthic Fauna and Sediments of the Nearshore Zone Off Panama City Beach, Florida.  

National Technical Information Service (NTIS)

This study presents: (1) basic data on the benthic fauna and surface sediments of the nearshore zone of Panama City Beach, Fla., before restoration of the beach, and (2) the results of a study on the effect of Hurricane Eloise on the benthic fauna in the ...

C. H. Saloman

1976-01-01

203

Water Mass Conversion in the Glacial Subarctic Pacific (54°N, 148°W): Physical Constraints and the Benthic-Planktonic Stable Isotope Record  

NASA Astrophysics Data System (ADS)

Benthic (Uvigerina spp., Cibicidoides spp., Gyroidinoides spp.) and planktonic (N. pachyderma sinistral, G. bulloides) stable isotope records from three core sites in the central Gulf of Alaska are used to infer mixed-layer and deepwater properties of the late glacial Subarctic Pacific. Glacial-interglacial amplitudes of the planktonic ?18O records are 1.1-1.3‰, less than half the amplitude observed at core sites at similar latitudes in the North Atlantic; these data imply that a strong, negative ?w anomaly existed in the glacial Subarctic mixed layer during the summer, which points to a much stronger low-salinity anomaly than exists today. If true, the upper water column in the North Pacific would have been statically more stable than today, thus suppressing convection even more efficiently. This scenario is further supported by vertical (i.e., planktic versus benthic) ?18O and ?13C gradients of >1‰, which suggest that a thermohaline link between Pacific deep waters and the Subarctic Pacific mixed layer did not exist during the late glacial. Epibenthic ?13C in the Subarctic Pacific is more negative than at tropical-subtropical Pacific sites but similar to that recorded at Southern Ocean sites, suggesting ventilation of the deep central Pacific from mid-latitude sources, e.g., from the Sea of Japan and Sea of Okhotsk. Still, convection to intermediate depths could have occurred in the Subarctic during the winter months when heat loss to the atmosphere, sea ice formation, and wind-driven upwelling of saline deep waters would have been most intense. This would be beyond the grasp of our planktonic records which only document mixed-layer temperature-salinity fields extant during the warmer seasons. Also we do not have benthic isotope records from true intermediate water depths of the Subarctic Pacific.

Zahn, Rainer; Pedersen, Thomas F.; Bornhold, Brian D.; Mix, Alan C.

1991-10-01

204

Benthic Marine Algal Herbarium of L.I. Sound  

NSDL National Science Digital Library

The University of Connecticut has a tremendous collection of algae from the Long Island Sound, and back in 2001 they went ahead and photographed the original herbarium sheets featuring the preserved algae specimens. The archive is quite comprehensive, as it features all of the benthic marine macroalgal species in the Long Island Sound. All told, there are over 299 images here, and visitors are encouraged to peruse the collection by phylum, family, or name. The site also contains a list of definitions, a regional map, and information about the team that worked to make this collection a possibility.

205

Continuous and simultaneous cultivation of benthic food diatom Nitzschia sp. and abalone Haliotis sieboldii by using deep seawater.  

PubMed

By using low-temperature, clean, and nutrient-rich properties of deep seawater (DSW; seawater below the euphotic layer), a continuous and simultaneous cultivation system for a benthic food diatom, Nitzschia sp., and juvenile abalone was established. Cell suspension of Nitzschia sp. was added to a bioreactor made of acrylic pipe (7 cm diameter x 50 cm long) containing short vinyl tubes (2 cm diameter x 2 cm long) as substrata. DSW collected from 320 m depth at Muroto City, in Kochi Prefecture, Japan, was supplied to the reactor and incubated under natural light (ca. 6000 lux) with a continuous DSW flow rate of 40 turnovers per hour. After growing enough benthic diatoms in the reactor, juveniles of abalone, Haliotis sieboldii (shell length ca. 10-20 mm) were put into a reactor, and cultivated simultaneously with food diatoms in the continuous flow system. During the four-month incubation, 7-month-old abalone juveniles with a shell length of 12.4 (average) +/-0.2 (SD) mm were grown to 19.4 (+/-1.7) mm in the reactor. Daily growth rates of abalones were 50-110 µm/day. These results indicate that the continuous cultivation system with DSW supports the growth of juvenile abalone without any supply of seaweed until it grows to release size. PMID:9852618

Fukami; Kawai; Asada; Okabe; Hotta; Moriyama; Doi; Nishijima; Yamaguchi; Taniguchi

1998-12-01

206

Flow enhances photosynthesis in marine benthic autotrophs by increasing the efflux of oxygen from the organism to the water  

PubMed Central

Worldwide, many marine coastal habitats are facing rapid deterioration due in part to human-driven changes in habitat characteristics, including changes in flow patterns, a factor known to greatly affect primary production in corals, algae, and seagrasses. The effect of flow traditionally is attributed to enhanced influx of nutrients and dissolved inorganic carbon (DIC) across the benthic boundary layer from the water to the organism however, here we report that the organism’s photosynthetic response to changes in the flow is nearly instantaneous, and that neither nutrients nor DIC limits this rapid response. Using microelectrodes, dual-pulse amplitude-modulated fluorometry, particle image velocimetry, and real time mass-spectrometry with the common scleractinian coral Favia veroni, the alga Gracilaria cornea, and the seagrass Halophila stipulacea, we show that this augmented photosynthesis is due to flow-driven enhancement of oxygen efflux from the organism to the water, which increases the affinity of the RuBisCO to CO2. No augmentation of photosynthesis was found in the absence of flow or when flow occurred, but the ambient concentration of oxygen was artificially elevated. We suggest that water motion should be considered a fundamental factor, equivalent to light and nutrients, in determining photosynthesis rates in marine benthic autotrophs.

Mass, Tali; Genin, Amatzia; Shavit, Uri; Grinstein, Mor; Tchernov, Dan

2010-01-01

207

A Comparison of Trichoptera (Caddisfly) Species Diversity From Several Peninsular Florida Waterbodies Using Benthic and Terrestrial Sampling Methods  

Microsoft Academic Search

Typically, environmental agencies tasked with water quality bioassessment solely use benthic sampling methods to collect aquatic insects. Because most aquatic insects live in water only as immatures, benthic samples consist largely of larvae. In Trichoptera, and most insect groups, alpha taxonomy is chiefly based on adult reproductive structures, thus specimens from benthic samples in many cases cannot be assigned species

A. K. Rasmussen; D. R. Denson

2005-01-01

208

Identifying cold-water coral ecosystem by using benthic foraminiferal indicators: from active reefs to the geological record  

NASA Astrophysics Data System (ADS)

Cold-water coral ecosystems dominated by the species Lophelia pertusa and Madrepora oculata, as well as cold-water coral carbonate mounds (fossils and/or active) occur worldwide and are especially developed along the European margin, from northern Norway to the Gulf of Cadiz and into the Alboran Sea. Their discovery is a major achievement of the last few decades and their widespread occurrence presents a challenge to understand their development, preservation and possible importance in the geologic record. On the Norwegian shelf active/living reefs are developed on elevated hard substrata. Along the Irish margin L. pertusa builds large fossil and/or active carbonate mounds. In the Gulf of Cadiz and in the Alboran Sea buried reefs and patch reefs are generally found in association with mud volcanoes. In modern oceans, they provide important ecological niches for the marine benthic fauna in the deep-sea. In comparison to the macrofauna the microfauna, particularly the foraminifera associated to these systems, are poorly known. We present here a detailed study based on quantitative analyses of benthic and planktonic foraminifera together with the statistical treatment of assemblage data collected along the Norwegian margin, in the Porcupine-Rockall region and in the Alboran Sea. The three regions were and/or are site of cold-water coral ecosystems settlements. Our study reveals that in the Porcupine/Rockall region benthic foraminiferal assemblages are strictly related to the distribution of facies. On the Norwegian margin, benthic foraminiferal habitats are weakly defined and grade one into the other preventing the sharp facies separation observed along the Irish margin (Margreth et al., 2009). In the Alboran Sea cold-water coral ecosystems and cold-water carbonate mounds are presently buried and corals are generally fragmented. However, benthic assemblages from coral-rich layers in the Alboran Sea and those from Porcupine/Rockall and Norway show remarkable similarities. In particular, epifaunal-attached species such as Discanomalina coronata, Cibicides refulgens, and Lobatula lobatula dominate the assemblages with D. coronata restricted to living cold-water coral reefs facies only and/or in co-occurrence with coral fragments. In conclusion, our data suggest that although cold-water coral ecosystems occur at different latitudes, the associated foraminiferal assemblages are consistent from Norway to the Western Mediterranean. Thus they can be used to identify these ecosystems even in the geologic record, when the corals are often strongly dissolved like in the Alboran Sea. References: Margreth, S., Rüggeberg, A. and Spezzaferri, S., 2009. Benthic foraminifera as bioindicator for cold-water coral reef ecosystems along the Irish margin. Deep Sea Res. Part I, 56: 2216-2234. This study is funded by the Swiss National Foundation Projects 200020-117928 and 200021-111694.

Margreth, Stephan; Rüggeberg, Andres; Gennari, Giordana; Spezzaferri, Silvia

2010-05-01

209

Spatial and temporal distribution of benthic stages of Cyclops vicinus and Chaoborus flavicans in relation to abiotic factors and benthic fauna  

Microsoft Academic Search

The horizontal distributions of the benthic stages of Chaoborus flavicans and Cyclops vicinus were studied in a eutrophic\\u000a stratified lake in the Massif-Central (France) over one year, at 5 stations from the shore to the centre of the lake. Their\\u000a distribution was investigated in relation to temperature, dissolved oxygen, sediment grain-size and other benthic organisms.\\u000a The dominant taxa of the

C. Rabette; N. Lair

1998-01-01

210

Bioaccumulation of heavy metals by benthic invertebrates at the Arkansas River, Colorado  

SciTech Connect

A one-year biomonitoring study was conducted to determine the extent of metal contamination (Cd, Cu, and Zn) in a benthic community from the Arkansas River (CO), a subalpine stream impacted by discharges from historic mining operations. Elevated concentrations of metals in water were paralleled by higher concentrations in benthic organisms. Significant differences (p < 0.05) in metal concentrations in aufwuchs and benthic macroinvertebrates among upstream (reference) and downstream stations were observed. Metal concentration in aufwuchs and benthic invertebrates remained elevated at some downstream stations, despite decreases in water concentrations. Time of year and functional group contributed to the variation in metal bioaccumulation in benthic macroinvertebrates. Monitoring metal concentrations in aquatic macroinvertebrates was a better indicator of metal bioavailability in the Arkansas River than ambient (water) metal concentrations.

Kiffney, P.M.; Clements, W.H. (Colorado State Univ., Fort Collins, CO (United States). Dept. of Fisheries and Wildlife Biology)

1993-08-01

211

Hydrologic controls on basin-scale distribution of benthic invertebrates  

NASA Astrophysics Data System (ADS)

variability is a major determinant of basin-scale distributions of benthic invertebrates. Here we present a novel procedure based on a probabilistic approach aiming at a spatially explicit quantitative assessment of benthic invertebrate abundance as derived from near-bed flow variability. Although the proposed approach neglects ecological determinants other than hydraulic ones, it is nevertheless relevant in view of its implications on the predictability of basin-scale patterns of organisms. In the present context, aquatic invertebrates are considered, given that they are widely employed as sensitive indicators of fluvial ecosystem health and human-induced perturbations. Moving from the analytical characterization of site-specific probability distribution functions of streamflow and bottom shear stress, we achieve a spatial extension to an entire stream network. Bottom shear stress distributions, coupled with habitat suitability curves derived from field studies, are used to produce maps of invertebrate suitability to shear stress conditions. Therefore, the proposed framework allows one to inspect the possible impacts on river ecology of human-induced perturbations of streamflow variability. We apply this framework to an Austrian river network for which rainfall and streamflow time series, river network hydraulic properties, and local information on invertebrate abundance for a limited number of sites are available. A comparison between observed species density versus modeled suitability to shear stress is also presented. Although the proposed strategy focuses on a single controlling factor and thus represents an ecological minimal model, it allows derivation of important implications for water resource management and fluvial ecosystem protection.

Ceola, Serena; Bertuzzo, Enrico; Singer, Gabriel; Battin, Tom J.; Montanari, Alberto; Rinaldo, Andrea

2014-04-01

212

Bipolar gene flow in deep-sea benthic foraminifera.  

PubMed

Despite its often featureless appearance, the deep-ocean floor includes some of the most diverse habitats on Earth. However, the accurate assessment of global deep-sea diversity is impeded by a paucity of data on the geographical ranges of bottom-dwelling species, particularly at the genetic level. Here, we present molecular evidence for exceptionally wide distribution of benthic foraminifera, which constitute the major part of deep-sea meiofauna. Our analyses of nuclear ribosomal RNA genes revealed high genetic similarity between Arctic and Antarctic populations of three common deep-sea foraminiferal species (Epistominella exigua, Cibicides wuellerstorfi and Oridorsalis umbonatus), separated by distances of up to 17, 000 km. Our results contrast with the substantial level of cryptic diversity usually revealed by molecular studies, of shallow-water benthic and planktonic marine organisms. The very broad ranges of the deep-sea foraminifera that we examined support the hypothesis of global distribution of small eukaryotes and suggest that deep-sea biodiversity may be more modest at global scales than present estimates suggest. PMID:17725572

Pawlowski, J; Fahrni, J; Lecroq, B; Longet, D; Cornelius, N; Excoffier, L; Cedhagen, T; Gooday, A J

2007-10-01

213

Measuring coral reef community metabolism using new benthic chamber technology  

USGS Publications Warehouse

Accurate measurement of coral reef community metabolism is a necessity for process monitoring and in situ experimentation on coral reef health. Traditional methodologies used for these measurements are effective but limited by location and scale constraints. We present field trial results for a new benthic chamber system called the Submersible Habitat for Analyzing Reef Quality (SHARQ). This large, portable incubation system enables in situ measurement and experimentation on community- scale metabolism. Rates of photosynthesis, respiration, and calcification were measured using the SHARQ for a variety of coral reef substrate types on the reef flat of South Molokai, Hawaii, and in Biscayne National Park, Florida. Values for daily gross production, 24-h respiration, and net calcification ranged from 0.26 to 6.45 g O2 m-2 day-1, 1.96 to 8.10 g O2 m-2 24 h-1, and 0.02 to 2.0 g CaCO3 m -2 day-1, respectively, for all substrate types. Field trials indicate that the SHARQ incubation chamber is an effective tool for in situ isolation of a water mass over a variety of benthic substrate types for process monitoring, experimentation, and other applications.

Yates, K. K.; Halley, R. B.

2003-01-01

214

An apparatus for preparing benthic samples aboard ship  

USGS Publications Warehouse

We describe a safe and effective apparatus for washing and reducing the volume of benthic samples collected by grab samplers aboard ship. The sample is transferred directly from the dredge to the apparatus and then washed with water pumped through pipes in the apparatus and from onboard hoses. Wastewater and materials smaller than 0.541 mm in diameter are washed overboard. Larger materials, including benthic organisms, collect on an upper 0.64-cm screen and on a lower 30-mm-mesh stainless steel bolt cloth. A collection jar is screwed into the bottom of the apparatus. Therefore, transfer of sample material from the apparatus to the jar is quick and easy. This apparatus has several advantages for use aboard ship over others described in the literature, especially in rough seas, in cold weather, and at night. The apparatus provides a safe and convenient platform for washing and reducing samples, and samples can be prepared while the vessel is traveling at full speed.

Pepper, Phillip N.; Girard, Thomas L.; Stapanian, Martin A.

2001-01-01

215

Benthic foraminiferal response to trace element pollution-the case study of the Gulf of Milazzo, NE Sicily (Central Mediterranean Sea).  

PubMed

The response of benthic foraminiferal assemblages to trace element pollution in the marine sediments of the Gulf of Milazzo (north-eastern Sicily) was investigated. Since the 1960s, this coastal area has been a preferred site for the development of two small marinas and a commercial harbour as well as for heavy industry. Forty samples collected in the uppermost 3-4 cm of an undisturbed layer of sediment in the littoral environment were used for this benthic foraminiferal analysis. The enrichment factors (EFs) of selected trace elements (As, Co, Cr, Cu, Mn, Ni, Pb and Zn) were also calculated. Changes both in benthic foraminiferal assemblages and in some trace elements concentrations have provided evidence that the gulf's littoral zone can be subdivided into three sectors characterised by environmental changes in the marine ecosystem. In the sector unpolluted, close to the Milazzo Cape, foraminiferal assemblages exhibit high values of species richness and foraminiferal density while trace element concentrations and their EFs are very low. Here, the highest densities of Miliolids and epiphytic species are present. On the contrary, in the sector polluted, from the marinas to the crude oil refinery, foraminiferal density and species diversity are low, and assemblages are dominated, albeit with very low densities, by species that tolerate stressed environmental conditions, such as LOFAs, agglutinants and Ammonia spp. Here, the highest trace elements concentrations of Pb, Zn and Cu and related EFs were detected. Eastwards, in the sector moderately polluted, foraminiferal populations are quite poor. They are characterised by low values of species richness and foraminiferal densities, nevertheless trace element concentrations become lower than in the other sectors and their EFs are often below 1. Deformed foraminifera, with percentages up to 7.14 %, were found in all three of the sectors. Differences in benthic foraminiferal assemblages, coupled with results from statistical analysis, indicate that anthropogenic trace element pollution could be considered as one of the most important causes of the modifications of foraminiferal assemblages in the study area. PMID:23828269

Cosentino, Claudia; Pepe, Fabrizio; Scopelliti, Giovanna; Calabrò, Monica; Caruso, Antonio

2013-10-01

216

Using Benthic Macroinvertebrate and Fish Communities as Bioindicators of the Tanshui River Basin Around the Greater Taipei Area -- Multivariate Analysis of Spatial Variation Related to Levels of Water Pollution  

PubMed Central

After decades of strict pollution control and municipal sewage treatment, the water quality of the Tanshui River increased significantly after pollution mitigation as indicated by the River Pollution Index (RPI). The pollution level of the estuarine region decreased from severe pollution to mostly moderately impaired. The most polluted waters are presently restricted to a flow track length between 15–35 km relative to the river mouth. From July 2011 to September 2012, four surveys of fish and benthic macroinvertebrates were conducted at 45 sampling sites around the Tanshui River basin. The pollution level of all the study area indicated by the RPI could also be explained by the Family Biotic Index (FBI) and Biotic Index (BI) from the benthic macroinvertebrate community, and the Index of Biotic Integrity (IBI) of the fish community. The result of canonical correlation analysis between aquatic environmental factors and community structure indicated that the community structure was closely related to the level of water pollution. Fish species richness in the estuarine area has increased significantly in recent years. Some catadromous fish and crustaceans could cross the moderate polluted water into the upstream freshwater, and have re-colonized their populations. The benthic macroinvertebrate community relying on the benthic substrate of the estuarine region is still very poor, and the water layer was still moderately polluted.

Young, Shuh-Sen; Yang, Hsi-Nan; Huang, Da-Ji; Liu, Su-Miao; Huang, Yueh-Han; Chiang, Chung-Ting; Liu, Jin-Wei

2014-01-01

217

Organic matter biolability and enzyme activities within stream benthic sediments in northeastern Siberia  

NASA Astrophysics Data System (ADS)

Predicted climate warming and permafrost thaw in northeastern Siberia is expected to alter hydrologic flow paths, changing the quantity and quality of organic matter (OM) supplied to streams. With deeper flow paths, higher contributions of OM sourced from permafrost soils may be exported. This material can be relatively biolabile and has been shown to stimulate microbial production of enzymes crucial for the degradation of carbon in stream waters. Permafrost derived OM that has a different composition than active layer OM may generate hot-spots for microbial activity, and CO2 and CH4 emissions in areas entering stream benthic sediments; however, our understanding of how OM composition influences enzyme activities, and how this affects carbon degradation in these areas remains rudimentary. Here we show that ancient OM residing in Yedoma permafrost (ice rich deposits formed during the late Pleistocene) and modern OM found in a typical Arctic watershed differ in their composition and biolability. Furthermore, we demonstrate that microbes within stream sediments receiving different OM sources (ancient/ modern) express different specific enzymes, which is likely affecting OM reactivity and is consistent with a shift in nutrient and organic carbon availability. We also show that differences in stream sediment type from a tussock grass dominated wetland and a stagnant pool in the stream channel may also affect enzyme activity rates. A better understanding of the impact of terrestrial carbon inputs on OM degradation in stream sediments will improve our understanding of potential feedbacks between permafrost and climate change.

Connolly, C. T.; Sather, K.; Ludwig, S.; Schade, J. D.; Sobczak, W. V.; Mann, P.

2013-12-01

218

Recovery of dairy manure nutrients by benthic freshwater algae.  

PubMed

Harnessing solar energy to grow algal biomass on wastewater nutrients could provide a holistic solution to nutrient management problems on dairy farms. The production of algae from a portion of manure nutrients to replace high-protein feed supplements which are often imported (along with considerable nutrients) onto the farm could potentially link consumption and supply of on-farm nutrients. The objective of this research was to assess the ability of benthic freshwater algae to recover nutrients from dairy manure and to evaluate nutrient uptake rates and dry matter/crude protein yields in comparison to a conventional cropping system. Benthic algae growth chambers were operated in semi-batch mode by continuously recycling wastewater and adding manure inputs daily. Using total nitrogen (TN) loading rates of 0.64-1.03 g m(-2) d(-1), the dried algal yields were 5.3-5.5 g m(-2) d(-1). The dried algae contained 1.5-2.1% P and 4.9-7.1% N. At a TN loading rate of 1.03 g m(-2) d(-1), algal biomass contained 7.1% N compared to only 4.9% N at a TN loading rate of 0.64 g m(-2) d(-1). In the best case, algal biomass had a crude protein content of 44%, compared to a typical corn silage protein content of 7%. At a dry matter yield of 5.5 g m(-2) d(-1), this is equivalent to an annual N uptake rate of 1,430 kg ha(-1) yr(-1). Compared to a conventional corn/rye rotation, such benthic algae production rates would require 26% of the land area requirements for equivalent N uptake rates and 23% of the land area requirements on a P uptake basis. Combining conventional cropping systems with an algal treatment system could facilitate more efficient crop production and farm nutrient management, allowing dairy operations to be environmentally sustainable on fewer acres. PMID:12137274

Wilkie, Ann C; Mulbry, Walter W

2002-08-01

219

Modeling and Field Studies of Chemical Plumes in Benthic Boundary Layers.  

National Technical Information Service (NTIS)

As part of the Chemical Sensing in the Marine Environment (CSME) program, a series of field experiments were carried out to investigate the dispersion and mixing of chemical plumes in the near-shore environment in order to assist the design and applicatio...

S. G. Monismith J. R. Koseff

1997-01-01

220

BLIPS: A SYSTEM FOR STUDYING BENTHIC BOUNDARY LAYER DYNAMICS. (R825513C001)  

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...

221

Antarctic Benthic Fauna in the Global Climate Change  

NASA Astrophysics Data System (ADS)

In the last 50 years a significant climatic shift has been observed along the Antarctic Peninsula (air and seawater temperature rise, glacial retreat, localized instances of lowered shallow waters salinities). Many Antarctic marine benthic invertebrates are adapted to specific environmental conditions (e.g. low stable temperatures, high salinity and oxygen content). Changes caused by global climate changes and subsequent glacial melting can be expected to have significant impacts on species physiology and distribution. The rise of sea water temperature coupled with such additional stress factors as melt water run-off, increased ice disturbance, disruption of food webs or invasion of alien species can be a serious problem for their long-term survival.

Kidawa, Anna; Janecki, Tomasz

2011-01-01

222

Benthic foraminifera of the Panamanian Province: distribution and origins.  

USGS Publications Warehouse

Two hundred twenty-nine species of benthic foraminifera have been identified from 96 stations representing 33 localities on the eastern Pacific inner continental shelf, ranging from southern Peru to northern Baja California. Their distributions mark nearshore provincial boundaries that are nearly identical with those previously documented from the distribution of ostracodes and molluscs. Thirteen species are characteristic of the Panamanian Province, one is characteristic of the Chilean-Peruvian Province, and one is characteristic of the newly proposed Sonoran Subprovince. Seventeen species (7%) appear to be endemic to the eastern Pacific. Fifty-eight (25%) of the species recognized are disjunct from population centers in the western Pacific, 134 species (59%) are disjunct from modern assemblages of the Atlanto-Carribean region, and 40 species (17%) are disjunct from both the western Pacific and the Atlanto-Caribbean. The distribution of the remaining 57 species (25%) is poorly documented; we classify them as of unknown origin. -Authors

Crouch, R. W.; Poag, C. W.

1987-01-01

223

Numerical modeling of benthic processes in the deep Arabian Sea  

NASA Astrophysics Data System (ADS)

Aerobic and anaerobic degradation of particulate organic carbon (POC) and carbonate equilibria in deep-sea surface sediments were studied at five stations located in the western (WAST), northern (NAST), eastern (EAST), central (CAST), and southern (SAST) Arabian Sea. In situ oxygen fluxes, porewater profiles of dissolved oxygen, nitrate, and Mn, pH profiles and solid-phase profiles of particulate organic carbon, Mn, and Fe were measured at each station. An early diagenesis model was applied to simulate the degradation and dissolution processes and to determine the benthic fluxes of POC, oxygen, nitrate, phosphate, CO 2, HCO 3-, and CO 32-. The benthic data sets were evaluated to constrain the POC input and the kinetics of organic matter degradation used in the model. The modeling showed that the POC rain rate to the seafloor is high at the western and northern stations, and decreases towards the southeast. At stations located in the vicinity of continental margins (WAST, NAST, EAST), 5-7% of the primary production sinks to the deep-sea floor. This unusually high POC rain is either caused by dust particles that accelerate and amplify the particle export from the euphotic zone or by rapid lateral transport processes. At the more remote stations (CAST, SAST) that receive lower dust inputs, the rain efficiency decreases to 1-4%. In the model, organic matter was separated into three fractions (3-G-model) that differ considerably in reactivity. At stations WAST, NAST, EAST, and CAST the bulk of organic matter is composed of extremely labile organic matter with a first order degradation constant ( k) of 15-30 yr -1. The moderately labile fraction with a kinetic constant of 0.2-0.6 yr -1 dominates the POC input at the oligotrophic station in the southern Arabian Sea (SAST). The third fraction that has a very low reactivity ( k=2-5×10 -4 yr -1) is only a minor component of the POC rain at all investigated stations. More than 95% of the organic matter is consumed in aerobic degradation processes. Denitrification and metal oxide reduction only contribute 1-2% to the total POC degradation. At the western station (WAST) a non-negligible portion (2%) of organic matter is consumed via sulfate reduction. The modeling demonstrates that carbonate dissolution is a major process in the deep Arabian Sea; 52-83% of the carbonate rain to the seafloor is dissolved within the surface sediments. In the western Arabian Sea, the monsoon systems produce a strong seasonality in the primary production. Non-steady-state modeling indicates that the benthic oxygen, nutrient, and inorganic carbon fluxes closely follow the seasonal dynamics in primary and export production. This very close benthic-pelagic coupling is established by the extremely labile organic matter fraction that dominates the POC rain to the seafloor. The metabolically released CO 2 induces a seasonal change in carbonate dissolution and carbonate alkalinity fluxes.

Luff, Roger; Wallmann, Klaus; Grandel, Sibylle; Schlüter, Michael

224

Geologic characteristics of benthic habitats in Glacier Bay, southeast Alaska  

USGS Publications Warehouse

In April 2004, more than 40 hours of georeferenced submarine digital video was collected in water depths of 15-370 m in Glacier Bay to (1) ground-truth existing geophysical data (bathymetry and acoustic reflectance), (2) examine and record geologic characteristics of the sea floor, and (3) investigate the relation between substrate types and benthic communities, and (4) construct predictive maps of seafloor geomorphology and habitat distribution. Common substrates observed include rock, boulders, cobbles, rippled sand, bioturbated mud, and extensive beds of living horse mussels and scallops. Four principal sea-floor geomorphic types are distinguished by using video observations. Their distribution in lower and central Glacier Bay is predicted using a supervised, hierarchical decision-tree statistical classification of geophysical data.

Harney, Jodi N.; Cochrane, Guy R.; Etherington, Lisa L.; Dartnell, Pete; Golden, Nadine E.; Chezar, Hank

2006-01-01

225

Benthic exchange and biogeochemical cycling in permeable sediments.  

PubMed

The sandy sediments that blanket the inner shelf are situated in a zone where nutrient input from land and strong mixing produce maximum primary production and tight coupling between water column and sedimentary processes. The high permeability of the shelf sands renders them susceptible to pressure gradients generated by hydrodynamic and biological forces that modulate spatial and temporal patterns of water circulation through these sediments. The resulting dynamic three-dimensional patterns of particle and solute distribution generate a broad spectrum of biogeochemical reaction zones that facilitate effective decomposition of the pelagic and benthic primary production products. The intricate coupling between the water column and sediment makes it challenging to quantify the production and decomposition processes and the resultant fluxes in permeable shelf sands. Recent technical developments have led to insights into the high biogeochemical and biological activity of these permeable sediments and their role in the global cycles of matter. PMID:23987916

Huettel, Markus; Berg, Peter; Kostka, Joel E

2014-01-01

226

A polyethylenetherephthalate (PET) device for sampling freshwater benthic macroinvertebrates.  

PubMed

A new device to sample freshwater benthic macroinvertebrates was used in a low and sandy stretch of a Brazilian sub-tropical river (the River Cai, Triunfo, RS) and in one of its small tributaries, Bom Jardim brook (Arroio Bom Jardim). In this study, the effectiveness of this device, a PET sampler, was tested at different sites in the river and the brook throughout the four seasons between 2001-2002. Comparisons were made by PCA and ANOVA, both employing a bootstrap procedure based on similarity matrices. The PET sampler proved to be a reliable tool for detection of seasonal and spatial differences in richness, total abundance of organisms, and Shannon's diversity index in both river and brook and is therefore recommended for use in the monitoring of macroinvertebrate communities in this system. PMID:15622850

Volkmer-Ribeiro, C; Guadagnin, D L; De Rosa-Barbosa, R; Silva, M M; Drügg-Hahn, S; Lopes-Pitoni, V L; Gastal, H A de O; Barros, M P; Demaman, L V

2004-08-01

227

Benthic Exchange and Biogeochemical Cycling in Permeable Sediments  

NASA Astrophysics Data System (ADS)

The sandy sediments that blanket the inner shelf are situated in a zone where nutrient input from land and strong mixing produce maximum primary production and tight coupling between water column and sedimentary processes. The high permeability of the shelf sands renders them susceptible to pressure gradients generated by hydrodynamic and biological forces that modulate spatial and temporal patterns of water circulation through these sediments. The resulting dynamic three-dimensional patterns of particle and solute distribution generate a broad spectrum of biogeochemical reaction zones that facilitate effective decomposition of the pelagic and benthic primary production products. The intricate coupling between the water column and sediment makes it challenging to quantify the production and decomposition processes and the resultant fluxes in permeable shelf sands. Recent technical developments have led to insights into the high biogeochemical and biological activity of these permeable sediments and their role in the global cycles of matter.

Huettel, Markus; Berg, Peter; Kostka, Joel E.

2014-01-01

228

Methods applied in studies of benthic marine debris.  

PubMed

The ocean floor is one of the main accumulation sites of marine debris. The study of this kind of debris still lags behind that of shorelines. It is necessary to identify the methods used to evaluate this debris and how the results are presented and interpreted. From the available literature on benthic marine debris (26 studies), six sampling methods were registered: bottom trawl net, sonar, submersible, snorkeling, scuba diving and manta tow. The most frequent method used was bottom trawl net, followed by the three methods of diving. The majority of the debris was classified according to their former use and the results usually expressed as items per unity of area. To facilitate comparisons of the contamination levels among sites and regions some standardization requirements are suggested. PMID:18082846

Spengler, Angela; Costa, Monica F

2008-02-01

229

Probabilistic sequence alignment of Late Pleistocene benthic ?18O data  

NASA Astrophysics Data System (ADS)

The stratigraphic alignment of ocean sediment cores plays a vital role in paleoceanographic research because it is used to develop mutually consistent age models for climate proxies measured in these cores. The most common proxy used for alignment is the The stratigraphic alignment of ocean sediment cores plays a vital role in paleoceanographic research because it is used to develop mutually consistent age models for climate proxies measured in these cores. The most common proxy used for alignment is the ?18O of calcite from benthic or planktonic foraminifera because a large fraction of ?18O variance derives from the global signal of ice volume. To date, alignment has been performed either by manual, qualitative comparison or by deterministic algorithms (Martinson, Pisias et al. Quat. Res. 27 1987; Lisiecki and Lisiecki Paleoceanography 17, 2002; Huybers and Wunsch, Paleoceanography 19, 2004). Here we present a probabilistic sequence alignment algorithm which provides 95% confidence bands for the alignment of pairs of benthic ?18O records. The probabilistic algorithm presented here is based on a hidden Markov model (HMM) (Levinson, Rabiner et al. Bell Systems Technical Journal, 62,1983) similar to those that have been used extensively to align DNA and protein sequences (Durbin, Eddy et al. Biological Sequence Analysis, Ch. 4, 1998). However, here the need to the alignment of sequences stems from expansion and/or contraction in the records due to changes in sedimentation rates rather than the insertion or deletion of residues. Transition probabilities that are used in this HMM to model changes in sedimentation rates are based on radiocarbon estimates of sedimentation rates. The probabilistic algorithm considers all possible alignments with these predefined sedimentation rates. Exact calculations are completed using dynamic programming recursions. The algorithm yields the probability distributions of the age at each point in the record, which are probabilistically inferred from the LR04 stack. The complication of the central (1-?)% intervals of these distributions yields the confidence bands. In an extension of this work we are rebuilding the stack using a profile HMM model (Durbin, Eddy et al, Ch. 5). We analyze the confidence bands produced for the alignments of 35 Late Pleistocene benthic ?18O records to the LR04 benthic ?18O stack. We find that the mean width of 95% confidence bands for core alignments varies between 3-23 kyr depending on the resolution and noisiness of the core's ?18O signal. Confidence bands within individual cores also vary greatly, ranging from ~0 to >40 kyr. These alignment confidence bands will allow researchers to examine the robustness of their conclusions with respect to alignment uncertainty at all points in the record. Additionally, they should aid in the identification of possible errors in inferred ages in the input record (e.g., due to core disturbances) because such errors are likely to be associated with large, local uncertainty.

Lawrence, C.; Lin, L.; Lisiecki, L. E.; Stern, J.

2013-12-01

230

Benthic nutrient sources to hypereutrophic Upper Klamath Lake, Oregon, USA  

USGS Publications Warehouse

Three collecting trips were coordinated in April, May, and August 2006 to sample the water column and benthos of hypereutrophic Upper Klamath Lake (OR, USA) through the annual cyanophyte bloom of Aphanizomenon flos-aquae. A porewater profiler was designed and fabricated to obtain the first high-resolution (centimeter-scale) estimates of the vertical, concentration gradients of macro- and micronutrients for diffusive-flux determinations. A consistently positive benthic flux for soluble reactive phosphorus (SRP) was observed with solute release from the sediment, ranging between 0.4 and 6.1 mg/m2/d. The mass flux over an approximate 200-km2 lake area was comparable in magnitude to riverine inputs. An additional concern, related to fish toxicity was identified when dissolved ammonium also displayed consistently positive benthic fluxes of 4 to 134 mg/m2/d, again, comparable to riverine inputs. Although phosphorus was a logical initial choice by water quality managers for the limiting nutrient when nitrogen-fixing cyanophytes dominate, initial trace-element results from the lake and major inflowing tributaries suggested that the role of iron limitation on primary productivity should be investigated. Dissolved iron became depleted in the lake water column during the course of the algal bloom, while dissolved ammonium and SRP increased. Elevated macroinvertebrate densities, at least of the order of 104 individuals/m2, suggested, that the diffusive-flux estimates may be significantly enhanced, by bioturbation. In addition, heat-flux modeling indicated that groundwater advection of nutrients could also significantly contribute to internal nutrient loading. Accurate environmental assessments of lentic systems and reasonable expectations for point-source management require quantitative consideration of internal solute sources ?? 2009 SETAC.

Kuwabara, J. S.; Topping, B. R.; Lynch, D. D.; Carter, J. L.; Essaid, H. I.

2009-01-01

231

Anthropogenic and natural disturbances to marine benthic communities in Antarctica  

SciTech Connect

Sampling and field experiments were conducted from 1975 to 1990 to test how the structure of marine benthic communities around McMurdo Station, Antarctica varied with levels of anthropogenic contaminants in marine sediments. The structure of communities (e.g., infauna density, species composition, and life history characteristics) in contaminated and uncontaminated areas were compared with the structure of communities influenced by two large-scale natural disturbances, anchor ice formation and uplift or iceberg scour. Benthic communities changed radically along a steep spatial gradient of anthropogenic hydrocarbon, metal, and PCB contamination around McMurdo Station. The heavily contaminated end of the gradient, Winter Quarters Bay, was low in infaunal and epifaunal abundance and was dominated by a few opportunistic species of polychaete worms. The edge of the heavily contaminated bay, the transition area, contained several motile polychaete species with less opportunistic life histories. Uncontaminated sedimentary habitats harbored dense tube mats of infaunal animals numerically dominated by populations of polychaete worms, crustaceans, and a large suspension feeding bivalve. These species are generally large and relatively sessile, except for several crustacean species living among the tubes. Although the community patterns around anthropogenic and natural disturbances were similar, particularly motile and opportunistic species at heavily disturbed and marginal areas, the natural disturbances cover much greater areas of the sea floor about the entire Antarctic continent. On the other hand, recovery from chemical contamination is likely to take many more decades than recovery from natural disturbances as contaminant degradation is a slow process. 77 refs., 6 figs., 5 tabs.

Lenihan, H.; Oliver, J.S. [Moss Landing Marine Labs., CA (United States)

1995-05-01

232

Sediment properties and benthic pelagic coupling in the North Water  

NASA Astrophysics Data System (ADS)

Measurements of sediment oxygen consumption were made during spring and summer in the North Water, the polynya that forms between Greenland and Ellesmere Island, and used in conjunction with sediment trap data to assess benthic-pelagic coupling in this system. Bottom sediments ranged from cobble in the north to soft muds in the southern part of the sampling grid. Muddy sediments were often pelletized as shown by disaggregation. Sediment photopigments were generally lower in coarse sediment stations to the north than in finer sediments stations to the south. Shipboard incubation of intact cores provided rates of 0.07-0.17 mmol O 2 m -2 h -1, with significantly greater oxygen consumption in summer than in spring. Additional incubation of macrofauna-free sediment aliquots in vials demonstrated significantly lower oxygen consumption in summer than in spring. Partitioning of benthic metabolism via these selective exclusion experiments showed a seasonal change in the response of the benthos to pelagic input, with meio-microbenthos dominating oxygen consumption in spring and macrofauna dominating in summer. Increased oxygen demand in the western polynya is suggested to coincide with the highest rates of carbon input measured by sediment traps and highest levels of sediment pigments. This region is an advective sink for particles produced in the east and subsequently transported by net polynya circulation. Although the benthos of the North Water does not display enhanced rates of carbon processing compared to other Arctic sediments, including other polynyas, the protracted production season of North Water provides a longer period over which the benthos can receive and mineralize organic carbon.

Grant, Jon; Hargrave, Barry; MacPherson, Paul

233

Benthic macrofauna data for San Francisco Bay, California, September 1986  

USGS Publications Warehouse

Benthic macrofauna were collected during September 1986 to evaluate locations for long-term monitoring stations as part of the U.S. Geological Survey Regional Effects Monitoring Program in San Francisco Bay, California. Three to ten replicate samples were collected with a modified Van Veen sampler (0.05 m2 area) at ten locations. One box core sample (0.06 m2 area) was collected at seven to the ten locations. Six of the box core samples were split into an upper 10 cm sample and a deeper sample before analysis. Macrofauna specimens were identified to the lowest possible taxon, usually genus and species, then counted. An average of 88 percent of the benthic macrofauna specimens were identified to the species level. The fraction identified varied among stations from 54 to 98 percent. Nematodes and oligochaetes accounted for most of the unidentified specimens. Relative to the total number of species identified in five replicates at each location, an average of 90 percent of the species were collected with three replicates. In general, species with high to moderate abundances were present in all replicates, and species collected only after three or more replicates averaged less than one specimen per replicate. Results from the box cores showed that the dominant species were most abundant in the upper 10 cm, the depth of sediment that can be adequately sampled with a modified Van Veen sampler. On the basis of the number of species and their abundances at each location, seven of the ten locations were selected for sampling in the regular program, which began in March 1987.

Schemel, Laurence E.; Thompson, J. K.; Harmon, J. G.; Yost, B. T.

1995-01-01

234

Water conditions and geochemistry in northern Adriatic anoxia-prone areas and response of benthic faunas to oxygen deficiencies  

NASA Astrophysics Data System (ADS)

One predicted effect of global climate change, specifically global warming, is the increase in the temperatures and stratification of shallow coastal and estuarine systems. This, coupled with ongoing anthropogenic eutrophication, will exacerbate hypoxia and benthic mortalities, significantly damaging these critical marine ecosystems. These phenomena are particularly severe on sublitoral soft-bottoms such as the poorly sorted silty sands at the study site in the northern Adriatic Sea. We deployed a specially developed underwater chamber to artificially induce anoxia in situ. Our Experimental Anoxia Generating Unit (EAGU) is a large plexiglass chamber that combines a digital camera with oxygen/hydrogen sulphide/pH sensors along with flashes and battery packs. The unit can be deployed for up to five days to autonomously generate oxygen crises and quantify both physico-chemical parameters and benthic responses. The system is initially positioned in an "open" configuration (open-sided aluminium frame) over the benthic fauna ("control" experiment). After 24 h the EAGU is switched to its "closed" configuration (plexiglass enclosure) and repositioned over the same assemblage. In this contribution, we focus on the natural oxygen content, temperature and pH of bottom waters during summer, the course of oxygen decrease during our experiments and the onset of H2S development. Oxygen content of the bottom water, a few centimetres above the sediment-water interface, ranges from ~3.5-8 but is mostly between 4-6 ml l-1 during July to September of the study periods (2005 and 2006) and decreases to zero within ~1-3 days after initiation of our experiments. In parallel, H2S starts to develop at the onset of anoxia. Water temperatures at the bottom were stable during experiments and ranged from 18.5°C to 21.4°C, but pH decreased from 8.3 to 8.1 at the beginning to 7.9 to 7.7 at the end of the experiments. Sediment profiling indicates that the diffusive benthic boundary layer is approximately 2.5 mm thick and that oxygen values decrease from ~2 ml l-1 3.5 mm above the sediment water interface to virtually zero at the interface. PH-values in 2 mm depth decrease from 8.15 to 7.6 within the first 10 h of the experiment. This indicates that the most reactive organic matter is decomposing in the uppermost few mm of the sediment. These data can be related to behavioural responses and mortality sequences of benthic faunas, including echinoids, crustaceans, molluscs and anemones. Beginning hypoxia (?2.0 ml l-1 DO) elicited escape patterns such as increased horizontal and vertical locomotion of animals. Moderate hypoxia (?1.0 ml l-1 DO) triggered species-specific sublethal effects such as arm-tipping in ophiuroids or extension from the sediment in sea anemones. At severe hypoxia (?0.5 ml l-1 DO) infaunal organisms began to emerge and first mortalities occurred. Some crustaceans and echinoderms are among the first to die, but sea anemones and large gastropods can even survive the onset of hydrogen sulfide.

Zuschin, Martin; Riedel, Bettina; Stachowitsch, Michael; Cermelj, Branko

2010-05-01

235

Comparison of benthic foraminifera inside and outside a sulphur-oxidizing bacterial mat from the present oxygen-minimum zone off Pakistan (NE Arabian Sea)  

NASA Astrophysics Data System (ADS)

Assemblages of live (Rose-Bengal-stained) and dead benthic foraminifera and stable oxygen and carbon isotopic composition of live benthic foraminifera were studied in and outside a bacterial mat composed of the large sulphur-oxidizing bacteria Thioploca and Beggiatoa from the oxygen-minimum zone off Pakistan (NE Arabian Sea). Two cores from the same Multicorer retrieved a bacterial mat and ambient sediment. The dominant species ( Globobulimina affinis, G. turgida, Bolivina pacifica, B. pseudopunctata, Uvigerina peregrina and Buliminella tenuata) in both cores are characteristic for dysoxic oxygen minimum zone conditions. The most significant difference between the two cores is the reduced number of stained benthic foraminifera (SBF) in the top 0.5 cm of the bacterial mat. Faunal densities of stained species are more than four times higher in the sediment surface sample (0-0.5 cm) outside the bacterial mat, at a distance of only 1.5 m. All stained species, however, observed outside the Beggiatoa/Thioploca mat were also observed in the core with the mat. Two species, Virgulinella fragilis and Bolivina dilatata, occur exclusively in the core with the bacterial mat. The diversity within the bacterial mat core is thus slightly higher than outside. Furthermore, the abundances of the species Buliminella morgani, B. tenuata and Alliatina primitiva are substantially higher in the bacterial mat than outside. Globobuliminids, on the other hand, seem to prefer the conditions outside the bacterial mat and are five times more frequent in the core taken outside the bacterial mat. Benthic foraminifers inhabit a broader microhabitat range outside the bacterial mat (˜5 cm) than within (3.5 cm). A marked decrease in SBF abundances was observed at the level of a black sulphur-rich layer which is interpreted to mark the shallow redox front below the bacterial mat. Stable carbon isotope analyses on live benthic foraminifera do not support a relation of the investigated Beggiatoa/Thioploca mat to a constant or seasonal seepage of methane at the continental slope off Pakistan. Surprisingly, however, stable oxygen isotope values of many species and especially of U. peregrina decrease with depth, which calls into question the suitability of U. peregrina as a recorder of bottom-water ?18O.

Erbacher, Jochen; Nelskamp, Susanne

2006-05-01

236

Mapping Benthic Habitats and Ocean Currents in the Vicinity of Central California's Big Creek Ecological Reserve.  

National Technical Information Service (NTIS)

Characterizations of benthic fish habitat and coastal ocean circulation patterns are critical steps in evaluating the effectiveness of the Big Creek Ecological Reserve at protecting and enhancing coastal fishery resources. With the coordinated efforts of ...

M. Yoklavich R. Starr J. Steger H. G. Greene F. Schwing C. Malzone

1997-01-01

237

The role of benthic fluxes of dissolved organic carbon in oceanic and sedimentary carbon cycling  

SciTech Connect

Benthic fluxes (sediment-water exchange) of dissolved organic carbon (DOC) represent a poorly quantified component of sedimentary and oceanic carbon cycling. In this paper the authors use pore water DOC data and direct DOC benthic flux measurements to begin to quantitatively examine this problem. These results; suggest that marine sediments represent a significant source of DOC to the oceans, as a lower limit of the globally-integrated benthic DOC flux is comparable in magnitude to riverine inputs of organic carbon to the oceans. Benthic fluxes of DOC also appear to be similar in magnitude to other sedimentary processes such as organic carbon oxidation (remineralization) in surface sediments and organic carbon burial with depth. 31 refs., 3 figs., 3 tabs.

Burdige, D.J.; Homstead, J. (Old Dominion Univ., Norfolk, VA (United States)); Alperin, M.J.; Martens, C.S.

1992-09-23

238

Evaluation of Benthic Macroinvertebrate Biomass Methodology. Part 1. Laboratory Analytical Methods.  

National Technical Information Service (NTIS)

Evaluation of analytical methods employed for wet weight (live or preserved samples) of benthic marcoinvertebrates reveals that centrifugation at 140 x gravity for one minute yields constant biomass estimates. Duration of specimen exposure in ethanol, for...

W. T. Mason P. A. Lewis C. I. Weber

1983-01-01

239

DEVELOPMENT OF BENTHIC MACROINVERTEBRATE INDEX FOR MEASURING THE CONDITION OF STREAMS AT A REGIONAL SCALE  

EPA Science Inventory

A multimetric macroinvertebrate index of stream condition was developed for the Mid-Atlantic Highlands Region of the United States. Benthic macroinvertebrate samples were collected from 562 first through third order streams between 1993 and 1995. Macroinvertebrates were collect...

240

Relationship Between Nutrient Enrichment and Benthic Function: Local Effects and Spatial Patterns  

EPA Science Inventory

Eutrophication-induced changes to benthic structure and function are problems of enormous ecological and economic significance. Understanding the relationships between nutrient enrichment and effects, modifying factors such as localized transport time, and symptoms of eutrophica...

241

St. Johns Estuary: Estuarine Benthic Macroinvertebrates Phase 2 Final Report. Special Publication SJ2012-SP4.  

National Technical Information Service (NTIS)

Benthic macrofaunal communities can be strongly influenced by changes in freshwater inflows in an estuary. Macrofauna are affected by changes in estuarine condition (including nutrient concentrations, sediment supply and salinity) caused by variation in f...

J. B. Pollack P. A. Montagna T. A. Palmer

2011-01-01

242

BENTHIC MICROBIAL RESPIRATION IN APPALACHIAN MOUNTAIN, PIEDMONT, AND COASTAL PLAINS, STREAMS OF THE EASTERN USA  

EPA Science Inventory

Our study had two objectives. First, in order to quantify the potential underestimation of community respiration caused by the exclusion of anaerobic processes, we compared benthic microbial respiration measured as 02 consumption with estimated based on DHA. Second, our previous ...

243

Coral reef condition and benthic sedimentation threat in four regions of south Puerto Rico  

EPA Science Inventory

Scleractinian corals, gorgonian octocorals, sponges and fishes were assessed near the cities of LaParguera, Guánica, Guayanilla, and Jobos along the southern coast of Puerto Rico in November – December 2010. Survey sites were targeted near areas with varying benthic...

244

DEVELOPMENT OF STANDARDIZED LARGE RIVER BIOASSESSMENT PROTOCOLS (LR-BP) FOR BENTHIC MACROINVERTEBRATE ASSEMBLAGES  

EPA Science Inventory

We conducted research comparing several methods currently in use for the bioassessment and monitoring of fish and benthic macroinvertebrate assemblages of large rivers. Fish data demonstrate that electrofishing 1000 m of shoreline is sufficient for bioassessments on boatable riv...

245

BIOGEOGRAPHY OF BENTHIC MACROINVERTEBRATES IN ESTUARIES ALONG THE GULF OF MEXICO AND WESTERN ATLANTIC COASTS  

EPA Science Inventory

The community composition of benthic macroinvertebrates from 870 estuarine sites was examined to determine boundaries of biogeographical provinces along the Gulf of Mexico and western Atlantic coasts of the United States. Our objective was to confirm or challenge established boun...

246

Ecological periodic tables for nekton and benthic macrofaunal community usage of estuarine habitats Slides  

EPA Science Inventory

Ecological periodic tables for nekton and benthic macrofaunal community usage of estuarine habitats Steven P. Ferraro, U.S. Environmental Protection Agency, Newport, OR Background/Questions/Methods The chemical periodic table, the Linnaean system of classification, and the Her...

247

Benthic invertebrate bycatch from a deep?water trawl fishery, Chatham Rise, New Zealand  

Microsoft Academic Search

ABSTRACT 1. Benthic invertebrate bycatch,was collected during trawling,for orange,roughy,(Hoplostethus atlanticus) at water depths of 662?1524m on the northern and eastern Chatham Rise, New Zealand, in July 1994. Seventy-three trawl tows were examined, 49 from ‘flat’ areas and 24 from two groups of ‘hills’ (small seamounts). Benthos was,recorded,from,82% of all tows. 2. Some 96 benthic species were recorded including Ophiuroidea (12

P. KEITH PROBERT; DON G. MCKNIGHT; SIMON L. GROVE

1997-01-01

248

Comparison of stream benthic invertebrate assemblages among forest types in the temperate region of Japan  

Microsoft Academic Search

We compared benthic invertebrate assemblages among headwater streams in several forest types in Japan. Forests were divided\\u000a into three clusters based on vegetation composition: old-growth broad-leaved forest, planted coniferous forest, and mixed\\u000a forest. The numbers of individuals and families and the diversity (Shannon-Wiener) of benthic invertebrate assemblages did\\u000a not differ significantly among the three forest clusters. However, principal components analysis

Mayumi Yoshimura

2007-01-01

249

Benthic invertebrates in adjacent created and natural wetlands in northeastern Ohio, USA  

Microsoft Academic Search

The benthic invertebrates of three adjacent wetlands in northeastern Ohio, USA were sampled with a benthic corer during May–August\\u000a 2001. The three wetlands consisted of a deep created wetland that overflowed into a shallow created wetland and a pre-existing\\u000a natural wetland. The created wetlands were four years old and seeded with cattails. Forty-two invertebrate taxa were collected\\u000a from all wetlands

Marianne Stanczak; Joe B. Keiper

2004-01-01

250

Benthic Algae in High Altitude Streams of the Alps – a Neglected Component of the Aquatic Biota  

Microsoft Academic Search

This is a review on benthic algae from streams situated above the tree line in the Alps. It integrates published and unpublished\\u000a data from alpine streams in Austria and in the Trento Province (Northern Italy). The main focus is on the structural and taxonomic\\u000a composition of benthic algae including macro- and micro-algae and their contribution to the epilithic biofilm and

E. Rott; M. Cantonati; L. Füreder; P. Pfister

2006-01-01

251

Benthic geochemistry of manganese in the Bay of Biscay, and sediment mass accumulation rate  

Microsoft Academic Search

Manganese is a major redox reactive element of benthic metabolism. We have built a database of existing knowledge on the benthic\\u000a geochemistry of Mn in the Bay of Biscay, in order to comprehensively assess the behaviour of Mn in a variety of environments\\u000a during early diagenesis. The database contains vertical profiles of particulate and dissolved Mn species of 59 cores

Aurélia Mouret; Pierre Anschutz; Pascal Lecroart; Gwénaëlle Chaillou; Christelle Hyacinthe; Jonathan Deborde; Frans J. Jorissen; Bruno Deflandre; Sabine Schmidt; Jean-Marie Jouanneau

2009-01-01

252

Biogeographical Patterns of Marine Benthic Macroinvertebrates Along the Atlantic Coast of the Northeastern USA  

Microsoft Academic Search

The biogeography of marine benthic macroinvertebrates of US Atlantic estuaries and inshore coastal areas from Delaware Bay\\u000a north to Passamaquoddy Bay was studied to compare recent data with historical biogeographic studies, define physical–chemical\\u000a factors affecting species’ distributions, and provide information for calibrating benthic indices of environmental condition.\\u000a Five years (2000–2004) of data from 614 non-polluted, soft-bottom stations from the National

Stephen S. Hale

2010-01-01

253

Taxonomic richness of stream benthic algae: Effects of flood disturbance and nutrients  

Microsoft Academic Search

We sampled benthic algae monthly for 15 months in 12 New Zealand gravel-bed streams to investigate among- stream differences in algal taxonomic richness and how this might relate to among-stream differences in flood disturbance and nutrient resource regimes. The mean number of benthic algal taxa per month ranged from 9.4 to 21.3 among streams. There were moderate month-to-month fluctuations in

Barry J. F. Biggs; Robert A. Smith

2002-01-01

254

Consequences of Increasing Hypoxic Disturbance on Benthic Communities and Ecosystem Functioning  

PubMed Central

Disturbance-mediated species loss has prompted research considering how ecosystem functions are changed when biota is impaired. However, there is still limited empirical evidence from natural environments evaluating the direct and indirect (i.e. via biota) effects of disturbance on ecosystem functioning. Oxygen deficiency is a widespread threat to coastal and estuarine communities. While the negative impacts of hypoxia on benthic communities are well known, few studies have assessed in situ how benthic communities subjected to different degrees of hypoxic stress alter their contribution to ecosystem functioning. We studied changes in sediment ecosystem function (i.e. oxygen and nutrient fluxes across the sediment water-interface) by artificially inducing hypoxia of different durations (0, 3, 7 and 48 days) in a subtidal sandy habitat. Benthic chamber incubations were used for measuring responses in sediment oxygen and nutrient fluxes. Changes in benthic species richness, structure and traits were quantified, while stress-induced behavioral changes were documented by observing bivalve reburial rates. The initial change in faunal behavior was followed by non-linear degradation in benthic parameters (abundance, biomass, bioturbation potential), gradually impairing the structural and functional composition of the benthic community. In terms of ecosystem function, the increasing duration of hypoxia altered sediment oxygen consumption and enhanced sediment effluxes of NH4+ and dissolved Si. Although effluxes of PO43? were not altered significantly, changes were observed in sediment PO43? sorption capability. The duration of hypoxia (i.e. number of days of stress) explained a minor part of the changes in ecosystem function. Instead, the benthic community and disturbance-driven changes within the benthos explained a larger proportion of the variability in sediment oxygen- and nutrient fluxes. Our results emphasize that the level of stress to the benthic habitat matters, and that the link between biodiversity and ecosystem function is likely to be affected by a range of factors in complex, natural environments.

Villnas, Anna; Norkko, Joanna; Lukkari, Kaarina; Hewitt, Judi; Norkko, Alf

2012-01-01

255

Patterns of colonization and succession of benthic assemblages in two artificial substrates  

NASA Astrophysics Data System (ADS)

Benthic communities colonizing two different typologies of artificial structures, Tecnoreef® pyramids (PY), and plinth modules (PL), differing for material and shape, were investigated for three years after their deployment on a soft bottom offshore Pedaso (Western Adriatic Sea). The aims were to describe the colonization patterns of benthic assemblages on the two artificial modules, to highlight possible differences between them and to detect the effectiveness of the artificial reef on the ecosystem functioning.

Spagnolo, A.; Cuicchi, C.; Punzo, E.; Santelli, A.; Scarcella, G.; Fabi, G.

2014-04-01

256

Biogenic budgets of particle rain, benthic remineralization and sediment accumulation in the equatorial Pacific  

Microsoft Academic Search

Budgets of organic C (Corg), CaC03 and opal have been constructed for the Palisades, NY Pacific equatorial region at 140°W between 5°N and 5°S. Measurements of the rain and benthic remineralization rate of biogenic materials have been adjusted and normalized to account for sampling biases. Sea surface temperature serves as a master variable in normalizing sediment trap and benthic remineralization

W. M. Berelson; R. F. Anderson; J. Dymond; D. Demaster; D. E. Hammond; R. Collier; S. Honjo; M. Leinen; J. McManus; R. Pope; C. Smith; M. Stephens

1997-01-01

257

Spatial Variability of Benthic-Pelagic Coupling in an Estuary Ecosystem: Consequences for Microphytobenthos Resuspension Phenomenon  

PubMed Central

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).

Ubertini, Martin; Lefebvre, Sebastien; Gangnery, Aline; Grangere, Karine; Le Gendre, Romain; Orvain, Francis

2012-01-01

258

Continental shelf upwelling and benthic Ostracoda in the Benguela System (Southeastern Atlantic Ocean)  

Microsoft Academic Search

The distribution of benthic Ostracoda (micro-crustacea) on the continental shelf off southwestern Africa is controlled by sea-floor physical and chemical parameters, which in turn can be correlated with the positions of quasi-permanent upwelling cells of the Benguela System. The linkage between benthic and surface physico-chemical environments (and consequently between benthos and surface parameters) is not direct, however, being modulated by

R. V. Dingle

1995-01-01

259

Grazing On Pelagic Primary Producers – The Role Of Benthic Suspension Feeders In Estuaries  

Microsoft Academic Search

For more than two decades it has been recognized that benthic suspension feeders, by filtering particles out of the water,\\u000a may have a major impact on the overlying water column. Benthic suspension feeders comprise a large group of both passive and\\u000a active filter feeders, but only the impact of actively pumping macro-zoobenthic organisms will be dealt with. Of these are

Jens Kjerulf Petersen

260

Benthic invertebrate assemblage in Samborombón River (Argentina, S. America), a brackish plain river  

Microsoft Academic Search

The spatial and temporal differences in the structure and composition of benthic invertebrates were studied at three sites\\u000a of the Samborombón River, which is an important tributary of the Río de la Plata Estuary (Argentina), having a low slope and\\u000a brackish drainage. Biological samples were taken during each season. Physico-chemical variables were measured to determine\\u000a their association in the benthic

Fernando Spaccesi; Alberto Rodrigues Capítulo

2009-01-01

261

Spatiotemporal Patterns of Subtidal Benthic Microalgal Biomass and Community Composition in Galveston Bay, Texas, USA  

Microsoft Academic Search

Many Gulf of Mexico estuaries have low ratios of water volume to bottom surface area, and benthic processes in these systems\\u000a likely have a major influence on system structure and function. The purpose of this study was to determine the spatiotemporal\\u000a distribution of biomass and community composition of subtidal benthic microalgal (BMA) communities in Galveston Bay, TX, USA,\\u000a compare BMA

James L. Pinckney; Alyce R. Lee

2008-01-01

262

Protistan bacterivory and benthic microbial biomass in an intertidal creek mudflat  

Microsoft Academic Search

We examined 8 sediment samples collected at 3 h intervals at Dean Creek (Sapelo Island, Georgia) to assess the impact of protist bacterivory on the standing crops of benthic bacterial biomass. The combined biomass of the benthic microalgae (BMA), bacteria, heterotrophic protists, and meiofauna ranged from 0.41 to 0.57 mg C g1 wet sediment (gws) in the samples examined. BMA

Jt Hollibaugh

2008-01-01

263

Spatio-temporal patterns of benthic invertebrates along the continuum of a braided Alpine river  

Microsoft Academic Search

Aquatic invertebrate community structure was quantified from six sites, each located in distinctly different geomorphic reaches along the Tagliamento River (N.E. Italy). Quantitative samples of benthic invertebrates were collected quarterly over one year from six sites (from 5- 1100m above sea level), while physico-chemical data were collected monthly. Total abundance of benthic invertebrates was highly vari- able in space and

Dave B. Arscott; Klement Tockner; J. V. Ward

2003-01-01

264

Application of benthic foraminiferal Mg\\/Ca ratios to questions of Cenozoic climate change  

Microsoft Academic Search

We investigate the evolution of Cenozoic climate and ice volume as evidenced by the oxygen isotopic composition of seawater (?18Osw) derived from benthic foraminiferal Mg\\/Ca ratios to constrain the temperature effect contained in foraminiferal ?18O values. We have constructed two benthic foraminiferal Mg\\/Ca records from intermediate water depth sites (Ocean Drilling Program sites 757 and 689 from the subtropical Indian

K. Billups; D. P. Schrag

2003-01-01

265

Responses of benthic macroinvertebrate communities to natural geothermal discharges in Yellowstone National Park, USA  

Microsoft Academic Search

We examined responses of benthic macroinvertebrate communities to natural geothermal discharges in 32 streams in Yellowstone\\u000a National Park (YNP), USA. Geothermal discharges played a major role in structuring benthic communities in YNP, as downstream\\u000a communities were characterized by low species richness, reduced abundance of EPT taxa and increased abundance of tolerant\\u000a caddisflies (Trichoptera), chironomids and non-insects. While some taxa were

William H. ClementsJeffrey; Jeffrey L. Arnold; Todd M. Koel; Rob Daley; Cathie Jean

2011-01-01

266

Explosive diversification following a benthic to pelagic shift in freshwater fishes  

PubMed Central

Background Interspecific divergence along a benthic to pelagic habitat axis is ubiquitous in freshwater fishes inhabiting lentic environments. In this study, we examined the influence of this habitat axis on the macroevolution of a diverse, lotic radiation using mtDNA and nDNA phylogenies for eastern North America’s most species-rich freshwater fish clade, the open posterior myodome (OPM) cyprinids. We used ancestral state reconstruction to identify the earliest benthic to pelagic transition in this group and generated fossil-calibrated estimates of when this shift occurred. This transition could have represented evolution into a novel adaptive zone, and therefore, we tested for a period of accelerated lineage accumulation after this historical habitat shift. Results Ancestral state reconstructions inferred a similar and concordant region of our mtDNA and nDNA based gene trees as representing the shift from benthic to pelagic habitats in the OPM clade. Two independent tests conducted on each gene tree suggested an increased diversification rate after this inferred habitat transition. Furthermore, lineage through time analyses indicated rapid early cladogenesis in the clade arising after the benthic to pelagic shift. Conclusions A burst of diversification followed the earliest benthic to pelagic transition during the radiation of OPM cyprinids in eastern North America. As such, the benthic/pelagic habitat axis has likely influenced the generation of biodiversity across disparate freshwater ecosystems.

2013-01-01

267

Benthic foraminiferal faunal and isotopic changes as recorded in Holocene sediments of the northwest Indian Ocean  

NASA Astrophysics Data System (ADS)

Historically, the Holocene has been considered an interval of relatively stable climate. However, recent studies from the northern Arabian Sea (Netherlands Indian Ocean Program 905) suggested high-amplitude climate shifts in the early and middle Holocene based on faunal and benthic isotopic proxy records. We examined benthic foraminiferal faunal and stable isotopic data from Ocean Drilling Program (ODP) Site 723 and total organic carbon data from ODP Site 724, Oman Margin (808 and 593 m water depths, respectively). At Site 723 the mid-Holocene shift in ?18O values of infaunal benthic species Uvigerina peregrina (1.4‰) is 3 times larger than that of epifaunal benthic species Cibicides kullenbergi recorded at Site NIOP 905 off Somalia. However, none of the five other benthic species we measured at Hole 723A exhibits such a shift in ?18O. We speculate that the late Holocene ?18O decrease in U. peregrina represents species-specific changes in ecological habitat or food preference in response to changes in surface and deep ocean circulation. While the stable isotopic data do not appear to indicate a middle Holocene climatic shift, our total organic carbon and benthic faunal assemblage data do indicate that the early Holocene deep Arabian Sea was influenced by increased ventilation perhaps by North Atlantic Deep Water and/or Circumpolar Deep Water incursions into the Indian Ocean, leading to remineralization of organic matter and a relatively weak early Holocene oxygen minimum zone in the northwest Arabian Sea in spite of strong summer monsoon circulation.

Gupta, Anil K.; Das, Moumita; Clemens, Steven C.; Mukherjee, Baidehi

2008-06-01

268

Turnover and paleoenvironmental changes across the Cretaceous/Paleogene boundary at the Galanderud section (Northern Alborz, Iran) based on benthic foraminifera  

NASA Astrophysics Data System (ADS)

A high-resolution quantitative study of benthic foraminifera across the expanded and continuous Cretaceous/Paleogene (K/Pg) boundary at the Galanderud section in northern Iran provides an excellent record of the K/Pg event. The benthic foraminiferal assemblages, in contrast to the planktic foraminifers, did not suffer mass extinction at the K/Pg boundary. Uppermost Maastrichtian assemblages are well preserved and highly diverse. Only ~3% of the benthic species became extinct, including Bolivinoides draco, Eouvigerina subsculptura, Neoflabellina sp. and Praebulimina reussi. Other species are temporarily absent for a short interval after the K/Pg boundary. Benthic foraminifera indicate outer neritic-uppermost bathyal depths during the Plummerita hantkeninoides Zone until 70 cm below the K/Pg boundary. This interval contains abundant species of Bolivinoides draco, Gaudryina pyramidata, Cibicidoides hyphalus, P. reussi, and Sitella cushmani. The paleodepth decreased to outer neritic in the uppermost Maastrichtian based on the dominance of Stensioeina excolata, G. pyramidata, Cibicidoides pseudoacutus, and Coryphostoma incrassata forma gigantea. On the other hand, some species such as P. reussi and C. hyphalus, which are normally found at bathyal depths, decreased in their abundances. These data suggest a sea-level fall at the end of Maastrichtian. Additional evidence for sea-level fall is a decrease of planktic/benthic ratio from ~60% to ~40% in the uppermost Maastrichtian. The K/Pg clay layer is characterized by a high abundance of opportunistic species such as Cibicidoides spp., C. pseudoacutus, and Tappanina selemensis. The drastic change of benthic foraminiferal assemblages coincides with a sharp drop in magnetic susceptibility and %CaCO3, mass extinction of planktic foraminifera, a sharp enrichment in Ir, and a 2.25‰ negative excursion in ?13C at the K/Pg boundary, which is largely compatible with the catastrophic effects of an asteroid impact on Earth that briefly, but severely destabilized the oceanic phytoplankton food webs. Isothermal Remanent Magnetization (IRM) curves treated by the cumulative log-Gaussian function shows that hematite (or goethite) and magnetite are the main magnetic minerals in the K/Pg clay layer, whereas large and small magnetite characterize the Maastrichtian and the Danian sediments, respectively. The dominance of hematite over magnetite at the K/Pg boundary explains the lack of the characteristic positive magnetic susceptibility peak observed in other sections suggesting higher oxidation state of the Galanderud depositional environment during the impact. The presence of three calcareous dinoflagellate chalk layers and large excursions in O- and C-isotopic compositions in basal Danian Zone P0 highlight the instability of the ecosystem immediately following the K/Pg boundary. In the Parvularugoglobigerina eugubina and Parasubbotina pseudobulloides Zones, there is an increase in both diversity and infaunal morphogroups, and a slight decrease of the epifaunal morphogroups; some deeper species increase in abundance including Gyroidinoides globosus and Marssonella oxycona. These changes might indicate a sea level rise and uppermost bathyal paleodepths in the early Danian, but it might also indicate improved conditions at the seafloor including greater flux of organic matter. These abrupt paleoenvironmental changes at the K/Pg boundary are correlated in age to the Chicxulub impact event and to the Deccan Phase 2; the contribution of each event is currently under study.

Asgharianrostami, Masoud; Leckie, R. Mark; Font, Eric; Frontalini, Fabrizio; Koeberl, Christian

2014-05-01

269

Effects of transient bottom water currents and oxygen concentrations on benthic exchange rates as assessed by eddy correlation measurements  

NASA Astrophysics Data System (ADS)

correlation (EC) measurements in the benthic boundary layer (BBL) allow estimating benthic O2 uptake from a point distant to the sediment surface. This noninvasive approach has clear advantages as it does not disturb natural hydrodynamic conditions, integrates the flux over a large foot-print area and allows many repetitive flux measurements. A drawback is, however, that the measured flux in the bottom water is not necessarily equal to the flux across the sediment-water interface. A fundamental assumption of the EC technique is that mean current velocities and mean O2 concentrations in the bottom water are in steady state, which is seldom the case in highly dynamic environments like coastal waters. Therefore, it is of great importance to estimate the error introduced by nonsteady state conditions. We investigated two cases of transient conditions. First, the case of transient O2 concentrations was examined using the theory of shear flow dispersion. A theoretical relationship between the change of O2 concentrations and the induced vertical O2 flux is introduced and applied to field measurements showing that changes of 5-10 ?M O2 h-1 result in transient EC-fluxes of 6-12 mmol O2 m-2 d-1, which is comparable to the O2 uptake of shelf sediments. Second, the case of transient velocities was examined with a 2D k-? turbulence model demonstrating that the vertical flux can be biased by 30-100% for several hours during changing current velocities from 2 to 10 cm s-1. Results are compared to field measurements and possible ways to analyze and correct EC-flux estimates are discussed.

Holtappels, Moritz; Glud, Ronnie N.; Donis, Daphne; Liu, Bo; Hume, Andrew; WenzhöFer, Frank; Kuypers, Marcel M. M.

2013-03-01

270

Impact of crab bioturbation on benthic flux and nitrogen dynamics of Southwest Atlantic intertidal marshes and mudflats  

NASA Astrophysics Data System (ADS)

The effect of the SW Atlantic intertidal burrowing crab Neohelice (Chasmagnathus) granulata on benthic metabolism, benthic flux, and benthic N cycling processes was investigated through field experiments and in situ benthic chambers incubations. Our experimental results show that the presence and activity of N. granulata and its burrows may affect the direction and magnitude of nutrient benthic fluxes. Bioturbation enhanced ammonium efflux at mudflats, and influx at marshes. The flux of nitrate toward the sediment was stimulated by crabs at light and dark conditions in marshes, but only under light exposure in mudflats. Crab bioturbation stimulated benthic metabolism, N mineralization, nitrification and denitrification potentials in both sites. Crabs seem to have contrasting effects on dissolved inorganic nitrogen (DIN) availability between marshes and mudflats, as reflected on benthic DIN flux. This different effect on DIN availability and also the possible different effects of crabs on N 2-fixers organisms could explain the opposite N 2 fixation pattern found for both habitats, since crabs promoted N 2 fixation in marshes, but diminished its rate in mudflats. Thus, the results obtained here through manipulative field experiments using benthic chambers suggest that macrofauna may influence the N benthic cycle and DIN fluxes in estuarine sediments. Besides, these macrofauna effects could be context-dependent, being many of them opposite between mudflats and marshes. We concluded that the above mentioned effects and the bioturbation-macrophytes interaction may be affecting the dissolved nutrient exportation from marshes to open waters.

Fanjul, Eugenia; Bazterrica, María C.; Escapa, Mauricio; Grela, María A.; Iribarne, Oscar

2011-05-01

271

Assessment of toxicity thresholds in aquatic environments: does benthic growth of diatoms affect their exposure and sensitivity to herbicides?  

PubMed

Benthic diatoms evolved in a biofilm structure, at the interface between water and substrata. Biofilms can adsorb toxicants, such as herbicides, but little is known about the exposure of biofilm organisms, such as benthic diatoms, to these adsorbed herbicides. We assessed the sensitivity of 11 benthic diatoms species to 6 herbicides under both planktonic and benthic conditions using single-species bioassays. The concentration that reduced the growth rate of the population by 10% (EC10) and 50% (EC50), respectively, varied depending on the species, the herbicides, and the growth forms involved. As a general trend, the more hydrophobic the herbicide, the more species were found to be sensitive under benthic growth conditions. Statistical differences (alpha<5%) were observed between the sensitivities under planktonic and benthic growth conditions for many hydrophobic herbicides. A protective effect of the biofilm against herbicides was observed, and this tended to decrease (at both the EC10 and EC50 levels) with increasing hydrophobicity. The biofilm matrix appeared to control exposure to herbicides, and consequently their toxicity towards benthic diatoms. For metolachlor, terbutryn and irgarol, benthic thresholds derived from species sensitivity distributions were more protective than planktonic thresholds. For hydrophobic herbicides, deriving sensitivity thresholds from data obtained under benthic growth seems to offer a promising alternative. PMID:23831793

Larras, Floriane; Montuelle, Bernard; Bouchez, Agnès

2013-10-01

272

Heavy ? 15N in Intertidal Benthic Algae and Invertebrates in the Scheldt Estuary (The Netherlands): Effect of River Nitrogen Inputs  

NASA Astrophysics Data System (ADS)

The study investigated ? 15N in the intertidal benthic food webs from the middle Westerschelde Estuary and the middle Oosterschelde. Much heavier ? 15N values were observed for the main benthic primary producers and invertebrates in the Westerschelde Estuary. In the Oosterschelde, mean ? 15N values ranged from 1·4 to 7·3‰ for SOM and suspended POM, respectively, to 6·3 to 9·1‰ for Fucus vesiculosus and benthic diatoms, respectively. Mean ? 15N values in benthic invertebrates ranged from 9·7‰ for Gammarus locusta to 15·4‰ for Tubificoides sp. In the Westerschelde Estuary, mean ? 15N increased from 8·1 to 8·6‰ for suspended POM and SOM, respectively, to heavier ? 15N from 15·9 to 28·5‰ for F. vesiculosus and benthic diatoms, respectively. Mean ? 15N for intertidal invertebrates ranged from 18·1‰ for Lumbricillus sp. to 20·7‰ for Eulimnogammarus obtusatus. Higher enrichment in 15N in benthic primary producers and invertebrates from the Westerschelde Estuary are most likely due to the incorporation of 15N-enriched DIN carried by the Scheldt River by benthic algae and, then by benthic consumers. These results point to the fact that ? 15N in benthic estuarine food webs may respond directly to anthropogenic nitrogen inputs delivered into estuaries by rivers which drain highly urbanized areas.

Riera, P.; Stal, L. J.; Nieuwenhuize, J.

2000-09-01

273

Seaweed-assisted, benthic gravel transport by tidal currents  

NASA Astrophysics Data System (ADS)

Traction transport of pebbles and cobbles occurs subtidally at current velocities below 0.5 m s- 1 when seaweed attached to clasts provides additional lift and drag to the clast. In the Juan de Fuca Strait, British Columbia, Canada, the seaweed Cymanthere triplicata commonly attaches to pebbles and provides sufficient additional surface area for tidal currents to drag the clast along the seafloor. Using in situ measurements of current velocities at 13 m water depth, the threshold for initiation of motion of a 30 mm pebble with attached seaweed is 0.3 m s- 1. This is approximately one order of magnitude less than the activation velocity for a 30 mm pebble without attached seaweed. In addition to kelp-rafted (floated) gravel, seaweed-assisted, benthic gravel transport is possible in marine settings where unidirectional currents (e.g., tidal currents, storm-induced bottom currents) are sufficient to transport pebbles alongshore, and into and across the offshore (below fairweather wave base). If preserved in the rock record, deposits of algal-enhanced gravel deposited via unidirectional, subtidal currents will likely appear as isolated gravel clasts encased in sandstone, reflecting the similar current velocities required to transport these two clast groups.

Frey, Shannon E.; Dashtgard, Shahin E.

2012-07-01

274

Sedimentary membrane lipids recycled by deep-sea benthic archaea  

NASA Astrophysics Data System (ADS)

Deep-sea sediments harbour a vast biosphere. Archaea-one of the three domains of life-are prevalent in marine environments, and comprise a significant fraction of the biomass in marine sediments. Archaeal membranes are well characterized, and are comprised of a glycerol backbone and a nonpolar isoprenoid chain. However, the ecology of sedimentary archaea remains elusive, because it is difficult to grow them in the laboratory. Here, we trace the fate of 13C-labelled glucose added to marine sediments in Sagami Bay, Japan, to determine the in situ mechanisms of membrane synthesis. Following the addition of labelled glucose to sediment samples collected in the region, we placed the cores on the sea floor and sampled them after 9 and 405days. We found that the 13C was incorporated into the glycerol backbone of archaeal membranes; 13C was apparent after 9 days of incubation, but most pronounced after 405 days. However, the isoprenoid chain of the membranes remained unlabelled. On the basis of the differential uptake of 13C, we suggest that the glycerol unit is synthesized de novo, whereas the isoprenoid unit is synthesized from relic archaeal membranes and detritus, because of the prevalence of these compounds in marine sediments. We therefore suggest that some benthic archaea build their membranes by recycling sedimentary organic compounds.

Takano, Yoshinori; Chikaraishi, Yoshito; Ogawa, Nanako O.; Nomaki, Hidetaka; Morono, Yuki; Inagaki, Fumio; Kitazato, Hiroshi; Hinrichs, Kai-Uwe; Ohkouchi, Naohiko

2010-12-01

275

Oil from the tropical marine benthic-diatom Navicula sp.  

PubMed

The potential of the tropical marine benthic-diatom Navicula sp. for biodiesel feedstock was investigated. Growth profiles were analyzed by changing nutrient compositions in three different media (Walne, plain seawater, and modified seawater) and irradiance intensities. Navicula sp. cells showed significant growth in Walne and modified seawater medium but not in plain seawater medium. The microalgae grew well in a pH range of 7.8-8.4, and the cells were very sensitive to the intensity of direct sunlight exposure. The average cell concentration obtained from the cultures in plain seawater, Walne, and modified seawater media at the beginning of the stationary phase was 0.70, 2.17, and 2.54 g/L, respectively. Electron spray ionization-ion trap-mass spectrometry showed that the triacylglycerols of the algae oil were identified as POP (palmitic-oleic-palmitic), POO (palmitic-oleic-oleic), and OOLn (oleic-oleic-linoleic). The oil productivity of Navicula sp. cultivated in Walne and modified seawater media was 90 and 124 ?L L(-1) culture d(-1). The Navicula sp. biodiesel exhibited a kinematic viscosity of 1.299 mm(2)/s, density of 0.8347 g/mL, and internal energy of 0.90 kJ/mL. PMID:22926527

Nurachman, Zeily; Brataningtyas, Dewi Susan; Hartati; Panggabean, Lily Maria Goretty

2012-11-01

276

Enhanced power from chambered benthic microbial fuel cells.  

PubMed

We describe a new chamber-based benthic microbial fuel cell (BMFC) that incorporates a suspended, high surface area and semi-enclosed anode to improve performance. In Yaquina Bay, OR, two chambered BMFC prototypes generated current continuously for over 200 days. One BMFC was pumped intermittently, which produced power densities more than an order of magnitude greater than those achieved by previous BMFCs with single buried graphite-plate anodes. On average, the continuous power densities with pumping were 233 mW/m2 (2.3 W/m3); peak values were 380 mW/m2 (3.8 W/m3), and performance improved over the time of the deployments. Without pumping, high power densities could similarly be achieved after either BMFC was allowed to rest at open circuit. A third chambered BMFC with a 0.4 m2 footprint was deployed at a cold seep in Monterey Canyon, CA to test the new design in an environment with natural advection. The power density increased 5-fold (140 mW/m2 vs 28 mW/m2) when low-pressure check valves allowed unidirectional flow through the chamber. PMID:18075105

Nielsen, Mark E; Reimers, Clare E; Stecher, Hilmar A

2007-11-15

277

Sensitivity of heterogeneous marine benthic habitats to subtle stressors.  

PubMed

It is important to understand the consequences of low level disturbances on the functioning of ecological communities because of the pervasiveness and frequency of this type of environmental change. In this study we investigated the response of a heterogeneous, subtidal, soft-sediment habitat to small experimental additions of organic matter and calcium carbonate to examine the sensitivity of benthic ecosystem functioning to changes in sediment characteristics that relate to the environmental threats of coastal eutrophication and ocean acidification. Our results documented significant changes between key biogeochemical and sedimentary variables such as gross primary production, ammonium uptake and dissolved reactive phosphorus flux following treatment additions. Moreover, the application of treatments affected relationships between macrofauna communities, sediment characteristics (e.g., chlorophyll a content) and biogeochemical processes (oxygen and nutrient fluxes). In this experiment organic matter and calcium carbonate showed persistent opposing effects on sedimentary processes, and we demonstrated that highly heterogeneous sediment habitats can be surprisingly sensitive to subtle perturbations. Our results have important biological implications in a world with relentless anthropogenic inputs of atmospheric CO2 and nutrients in coastal waters. PMID:24312332

Rodil, Iván F; Lohrer, Andrew M; Thrush, Simon F

2013-01-01

278

Determining the relative sensitivity of benthic diatoms to atrazine using rapid toxicity testing: a novel method.  

PubMed

Herbicides pose a potential threat to aquatic ecosystems, especially to phototrophic organisms such as benthic diatoms. Benthic diatoms may be a valuable indicator of the toxic impacts of herbicides in aquatic systems. However, this requires information on the herbicide sensitivity of a wide range of freshwater benthic diatom taxa. Unfortunately this information is only available for a limited number of species as current methods of developing new algae toxicity tests on individual taxa are lengthy and costly. To address this issue, we developed a new rapid toxicity test method to test natural benthic communities, from which the relative herbicide sensitivity of many individual taxa can be derived. This involved the collection of natural benthic communities from rocks in situ, which were placed directly into laboratory toxicity tests. Sensitivity data for several diatom genera in a 48 hour exposure toxicity test were produced, without the need for cultures or multiple site visits. After exposure to the highest treatment of atrazine (500 ?g L(-1)) there were significant declines of healthy cells in the most sensitive genera: Gomphonema declined by 74%, Amphora by 62%, Cymbella by 54% and Ulnaria by 34% compared to control levels. In contrast, the genera, Eunotia, Achnanthidium and Navicula, had no statistically significant decline in cell health. This method can identify the diatom taxa most at risk of herbicide toxicity within the natural benthic diatom community. The rapid toxicity testing method presented is a simple and effective method to obtain sensitivity data for multiple taxa within a natural benthic diatom community in a relatively short period of time. PMID:24742551

Wood, Rebecca J; Mitrovic, Simon M; Kefford, Ben J

2014-07-01

279

The use of fossil benthic foraminifera to define reference conditions for present-day marine waters  

NASA Astrophysics Data System (ADS)

The implementation of legislations is generating a fruitful debate amongst marine scientists about how to define efficient and reliable bio-assessment tools to monitor the ecological quality status (EcoQS) of marine waters. According to those legislations, EcoQS assessment needs a "reference condition" with which to compare the present-day condition at a site. The fossil record has a potential to reconstruct PaleoEcoQS and thereby establish in situ reference conditions from pre-impact times. Unlike most macrofaunal groups which are the most commonly used biological quality indicator in these environments, benthic foraminifera leave a fossil record and therefore allow the reconstruction of human-induced environmental disturbance over decades to centuries. Foraminifera have the potential to serve as ecosystem characterization tools in modern and past marine environments. We compared the response of benthic foraminifera, macrofauna and selected environmental parameters from the same sites in areas with relatively stable salinity and temperature conditions but otherwise contrasting environmental properties (e.g., varying degree of anthropogenic impact). In August 2008, replicate samples for living (stained) benthic foraminifera and macrofauna from 27 stations in 11 silled fjords along the Norwegian Skagerrak coast were examined. Environmental data (bottom-water dissolved-oxygen, TOC, TN and pigments) were analysed for each station. The same kind of data were analysed from 2 recolonisation sites in the inner Oslofjord. In addition, the PaleoEcoQS during the past century was reconstructed using benthic foraminifera and selected environmental parameters from 11 stations in the inner Oslofjord. Results show that living benthic foraminifera are at least as reliable to define present-day EcoQS as conventional methods. Fossil benthic foraminifera can also define ecological status of reference conditions from pre-impacted times. This is not possible using conventional methods. Consequently, benthic foraminifera are excellent bioindicators of human-induced environmental impacts over time.

Bouchet, V. M. P.; Hess, S.; Dolven, J. K.; Alve, E.

2012-04-01

280

Modern assemblage changes of benthic algae as a result of hypersalinization of the Aral Sea  

NASA Astrophysics Data System (ADS)

The benthic algal coenosis, consisting of microphytobenthos, macrophytes, and microepiphytes, exhibited changes related to gradually increasing salinity in the Large Aral Sea from 2002 to 2005. Since 2000, the diversity has decreased from 159 species [Mirabdullayev, E.M., 2004. Succession of the ecosystems of the Aral Sea during its transition from oligohaline to polyhaline water body. The Dying Aral Sea, Selected Papers from the 35th International Liege Colloquium on Ocean Dynamics. J. Mar. Syst. 47 (1-4), 101-107.] to 38 species of microepiphytes, including mobile forms. We investigated species composition, assemblage structure, and spatial distribution. The salinity of the Large Aral Sea, which recently separated into two parts (a shallow eastern and a deep western basin connected by a channel to the north), ranges from 95-130‰, with the highest values in the eastern basin and in the channel. The algal flora of the Large Aral Sea currently consists primarily of diatoms. Diatom species previously restricted to the eastern basin ( Amphora coffeaformis, A. acutiuscula, and Synedra tabulata var . parva) spread into the western basin and species adapted to salinity < 90‰ ( Actinocyclus ehrenbergii) are gradually disappearing from the assemblages. However, the majority of the remaining algal flora species have adapted to the steadily increasing salinity. Some of the euryhaline species observed in the western basin exhibit a salinity tolerance > 90‰, which has not been described before. As a result of increasing salinity (91 to 97‰) in the western basin surface water layer, a replacement of "western" by "eastern" epiphytic type assemblages started in 2004-2005.

Sapozhnikov, F. V.; Ivanishcheva, P. S.; Simakova, U. V.

2009-03-01

281

Earth's Layers  

NSDL National Science Digital Library

Complete a poster all about Earth's Layers! Directions: Make a poster about Earth's Layers. (20 points) Include at least (1) large picture (15 points) on your poster complete with labels of every part (10 points). (15 points) Include at least three (3) facts about Earth's Layers. (5 points each) (15 points) Write at least a three sentence summary of your poster ...

Walls, Mrs.

2011-01-30

282

Multispecies Record of Benthic Foraminiferal Shell Weight in Santa Barbara Basin: A Deglacial Environmental Record  

NASA Astrophysics Data System (ADS)

There exists increasing interest in resolving the effect of environmental parameters on foraminiferal test weight. We utilize a high-resolution core, MV0811-15JC (34°36.930' N, 119°12.920' W; 418m water depth; 3-15 ka; sedimentation rate ~100cm/ka) from the Santa Barbara Basin (SBB) to examine a multispecies record of benthic foraminiferal weight and test wall thickness. We compare these findings to records of benthic ecosystem, oxygenation and ?18O change during and since the last deglaciation. Ongoing work in SBB has characterized drastic changes in benthic communities over the past 15 kyr in response to climate and dissolved oxygen concentrations. Records of the average test weight in the >250 ?m size fraction of Uvigerina peregrina covary with changes in the benthic community in response to oxygenation events and may represent a record of average maximum growth size. Average test weight, constrained by a narrow size fraction (within < 55 ?m difference in mesh size), is sometimes treated alone or with additional size correction as a proxy for test wall thickness. Narrow fraction test weights show significantly less variability in both Uvigerina peregrina and Bolivinia argentea between samples. We further analyze average test wall thickness in these samples, to develop an understanding of controls on shell weight and ongoing work seeks, to identify ideal benthic target species and to best understand shell weight as a proxy for carbonate ion (pH) of seawater.

Davis, K. V.; Hill, T. M.; Moffitt, S. E.; Downing, S.

2012-12-01

283

Effects of Stream Fishes on Benthic Primary Productivity: A Mechanistic Test  

NASA Astrophysics Data System (ADS)

I simultaneously tested three alternative hypotheses (the trophic cascade, nutrient enhancement via terrestrial nutrient translocation, and nutrient enhancement via bioturbation) for consumer regulation of primary productivity (PPR) by three widely distributed stream fish species (Orangethroat Darter, Western Mosquitofish, and Bullhead Minnow). I used stream mesocosms fitted with fish and terrestrial input barriers to address relative importance of localized fish predation versus access to terrestrial inputs for fish consumer effects. Orangethroat Darter, a benthic invertivore, increased PPR through an apparent trophic cascade, by localized reduction of benthic grazing invertebrate densities. Western mosquitofish, a surface feeding insectivore, increased PPR by enhancing nutrients through terrestrial nutrient translocation, and had no effect on benthic grazer invertebrate density. Bullhead Minnow, a benthic omnivore that disturbed sediments during foraging, increased PPR through nutrient enhancement via bioturbation, but within specific stream mesocosm areas two which the fish was restricted it also reduced benthic grazing invertebrates. Thus, suggesting this species may have affected PPR through a combination bioturbation and trophic cascade mechanisms. These mechanistic pathways are likely common processes by which fish affect food web structure and ecosystem function in many stream ecosystems.

Hargrave, C. W.

2005-05-01

284

Seasonal dynamics of benthic macroinvertebrates of Pond B, Savannah River Plant Aiken, South Carolina  

SciTech Connect

This study was designed to evaluate the spatial and seasonal distributions, compositions, and abundances of benthic macroinvertebrates in Pond B after 20 years of postthermal recovery. There are both basic and applied uses for the data gathered during the study. The examination of species composition and abundances as a function of season and water depth adds to the base of general knowledge on the benthic invertebrates of lentic systems. The current species composition also provides an indication of a portion of the postthermal community succession. An estimate of the biomass of the benthic community permits a calculation of the radionuclide inventory in this ecosystem compartment, if average concentrations are concurrently determined. Such data may then be used to predict food chain transfers to higher consumers and potential export from the ecosystem. Specific hypotheses tested were: (1) densities of certain benthic invertebrate communities vary with season, (2) densities of benthic invertebrates vary with water depth, and (3) the effect of season on invertebrate density depends on water depth (i.e. there is an interaction between depth and season). Other community parameters considered were species composition, diversity, and relative biomass by taxa. 30 refs., 5 figs., 9 tabs.

Whicker, A.D.

1988-01-01

285

Taxonomic diversity and structure of benthic macroinvertebrates in Aby Lagoon (Ivory Coast, West Africa).  

PubMed

The benthic macroinvertebrates of Aby lagoon (West Africa: Ivory coast) was studied during four seasons (high dry season, high rainy season, low dry season and low rainy season, respectively) from June 2006 to March 2007. The distribution of the benthic macroinvertebrates species was recorded at 13 stations on the whole of the lagoon. A total of 62 taxa of benthic macroinvertebrates belonging to 28 families and 10 orders were listed. The molluscs and crustaceans dominate qualitatively by adding up 51 and 24%, respectively of the total number of organisms. Five taxa (Corbula trigona (20%), Pachymelania aurita (12%), Clibernhardius cooki (7%), Oligochaeta (7%) and Crassostrea gasar (6%) accounted for 52% of total abundance. Classification analysis used to perform the characterisation of the lagoon on the basis of benthic macroinvertebrates showed the existence of four main clusters in which the seasonal pattern in benthic macroinvertebrates were very similar in the four seasons. In contrast the species richness and diversity indices were significantly different. Furthermore these indices where higher in the stations closer to the sea and surrounded by mangrove trees (southern area) compared to the inland ones. PMID:19137831

Kouadio, K N; Diomandé, D; Ouattara, A; Koné, Y J M; Gourène, G

2008-09-15

286

Benthic foraminifera from polluted marine environment of Sulaibikhat Bay (Kuwait).  

PubMed

Quantitative analyses of recent benthic foraminiferal assemblages (living and dead) were carried out on the surface sediments of Sulaibikhat Bay. Marked contrast in foraminiferal assemblages between the shallow tidal mudflats and the deep tidal channel and their relation to the extent of pollution were observed. Cluster analysis of quantitative data on the distribution of foraminiferal tests revealed three assemblages that depend mainly on the intensity of pollution; (1) a highly polluted tidal flat assemblage, (2) normal (or less polluted) mud flat assemblage and, (3) tidal channel and subtidal assemblage. The highly polluted assemblage characterized by a drop in species densities (< 100 tests/20 cm(3) sediment) but with high average diversity (5.8 Yule-Simpson Index). The microfauna of the less polluted flat displays relatively lower diversity (4.6) but high density of tests (47.2% of the total picked tests). The most abundant species of this assemblage is Ammonia tepida, displays its maximum density in this assemblage. Ammonia tepida drops in density from 17.12% to 3.07% in the polluted assemblage. Tidal channel foraminiferal assemblages should normally display lower diversities than those of tidal flats, because tidal current in the channels tend to wash away most nutrient materials. However, this is not the case of the present study area which could be due to environmental setting of the Sulaibikhat Bay in which tidal currents bring in exceptionally high amounts of nutrients from Shatt Al-Arab Estuary and in which the tidal flats are strongly and adversely polluted. PMID:18389379

Al-Zamel, A Z; Al-Sarawi, M A; Khader, S R; Al-Rifaiy, I A

2009-02-01

287

Biological vs. physical mixing effects on benthic food web dynamics.  

PubMed

Biological particle mixing (bioturbation) and solute transfer (bio-irrigation) contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria) and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter assimilation by the metazoan lower part of the food web through niche establishment (i.e., ecosystem engineering) or rather deprives them from food sources, is so far unclear. We investigated the effects of the ecosystem engineers Lanice conchilega (bio-irrigator) and Abra alba (bioturbator) compared to abiotic physical mixing events on survival and food uptake of nematodes after a simulated phytoplankton bloom. The (13)C labelled diatom Skeletonema costatum was added to 4 treatments: (1) microcosms containing the bioturbator, (2) microcosms containing the bio-irrigator, (3) control microcosms and (4) microcosms with abiotic manual surface mixing. Nematode survival and subsurface peaks in nematode density profiles were most pronounced in the bio-irrigator treatment. However, nematode specific uptake (??(13)C) of the added diatoms was highest in the physical mixing treatment, where macrobenthos was absent and the diatom (13)C was homogenised. Overall, nematodes fed preferentially on bulk sedimentary organic material rather than the added diatoms. The total C budget (µg C m(-2)), which included TO(13)C remaining in the sediment, respiration, nematode and macrobenthic uptake, highlighted the limited assimilation by the metazoan benthos and the major role of bacterial respiration. In summary, bioturbation and especially bio-irrigation facilitated the lower trophic levels mainly over the long-term through niche establishment. Since the freshly added diatoms represented only a limited food source for nematodes, the macrobenthic effect was more pronounced in niche establishment than the negative structuring effects such as competition. PMID:21455308

Braeckman, Ulrike; Provoost, Pieter; Moens, Tom; Soetaert, Karline; Middelburg, Jack J; Vincx, Magda; Vanaverbeke, Jan

2011-01-01

288

Benthic invertebrate bioassays with toxic sediment and pore water  

USGS Publications Warehouse

The relative sensitivities of bioassays to determine the toxicity of sediments were investigated and three methods of making the sample dilutions required to generate dose-response relationships were compared. The assays studied were: (a) Microtox(R), a 15-min assay of Photobacterium phosphoreum bioluminescence inhibition by pore water; (b) 48-h Daphnia magna lethality test in pore water; (c) 10-d subchronic assay of lethality to and reduction of weight gain by Chironomus tentans performed in either whole sediment or pore water; (d) 168-h acute lethality assay of Hexagenia limbata in either whole sediment or pore water. The three methods of diluting sediments were: (a) extracting pore water from the toxic location and dilution with pore water from the control station; (b) diluting whole sediment from the toxic location with control whole sediment from a reference location, then extracting pore water; and (c) diluting toxic, whole sediment with whole sediment from a reference location, then using the whole sediment in bioassays. Based on lethality, H. limbata was the most sensitive organism to the toxicity of Detroit River sediment. Lethality of D. magna was similar to that of H. limbata in whole sediment and can be used to predict effects of whole sediment toxicity to H. limbata. The concentration required to cause a 50% reduction in C. tentans growth (10-d EC50) was approximately that which caused 50% lethality of D. magna (48-h LC50) and was similar to the toxicity that restricts benthic invertebrate colonization of contaminated sediments. While the three dilution techniques gave similar results with some assays, they gave very different results in other assays. The dose-response relationships determined by the three dilution techniques would be expected to vary with sediment, toxicant and bioassay type, and the dose-response relationship derived from each technique needs to be interpreted accordingly.

Giesy, John P.; Rosiu, Cornell J.; Graney, Robert L.; Henry, Mary G.

1990-01-01

289

Benthic Bacterial and Fungal Productivity and Carbon Turnover in a Freshwater Marsh  

PubMed Central

Heterotrophic bacteria and fungi are widely recognized as crucial mediators of carbon, nutrient, and energy flow in ecosystems, yet information on their total annual production in benthic habitats is lacking. To assess the significance of annual microbial production in a structurally complex system, we measured production rates of bacteria and fungi over an annual cycle in four aerobic habitats of a littoral freshwater marsh. Production rates of fungi in plant litter were substantial (0.2 to 2.4 mg C g?1 C) but were clearly outweighed by those of bacteria (2.6 to 18.8 mg C g?1 C) throughout the year. This indicates that bacteria represent the most actively growing microorganisms on marsh plant litter in submerged conditions, a finding that contrasts strikingly with results from both standing dead shoots of marsh plants and submerged plant litter decaying in streams. Concomitant measurements of microbial respiration (1.5 to 15.3 mg C-CO2 g?1 of plant litter C day?1) point to high microbial growth efficiencies on the plant litter, averaging 45.5%. The submerged plant litter layer together with the thin aerobic sediment layer underneath (average depth of 5 mm) contributed the bulk of microbial production per square meter of marsh surface (99%), whereas bacterial production in the marsh water column and epiphytic biofilms was negligible. The magnitude of the combined production in these compartments (?1,490 g C m?2 year?1) highlights the importance of carbon flows through microbial biomass, to the extent that even massive primary productivity of the marsh plants (603 g C m?2 year?1) and subsidiary carbon sources (?330 g C m?2 year?1) were insufficient to meet the microbial carbon demand. These findings suggest that littoral freshwater marshes are genuine hot spots of aerobic microbial carbon transformations, which may act as net organic carbon importers from adjacent systems and, in turn, emit large amounts of CO2 (here, ?870 g C m?2 year?1) into the atmosphere.

Buesing, Nanna; Gessner, Mark O.

2006-01-01

290

Gradients of benthic pelagic coupling and carbon budgets in the Adriatic and Northern Ionian Sea  

NASA Astrophysics Data System (ADS)

The Adriatic sea is generally viewed as a long bay in the Central Mediterranean, stretching SE to NW for 800 km, from the Strait of Otranto to the Gulf of Venice, with an extremely long, geometrically complex coastline, creating a high diversity of hydrodynamic and sedimentary environments. The seafloor slopes down from the North shallow shelf (mean depth 35 m) through the middle Adriatic depression (250 m depth in the Pomo Pit) to the bathyal reached in the Southern Adriatic pit (1260 m). Typical physiographic and climatic features strongly influence biological productivity. The productivity of the Northern Adriatic is among the highest in the Mediterranean, while it becomes lower in the offshore waters of the Central and Southern subbasins, defining clear oligotrophic and benthic-pelagic coupling gradients from the Northern to the Southern edge of the basin. Assessing the benthic response to particulate fluxes of organic matter from the photic layer was a target of the EU-MATER Project. The applied methodological strategy involved measurements of primary production by 14C in situ incubation technique, of particulate fluxes through the water column by moored sediment traps, of sediment community oxygen consumption (SCOC) by in situ and on-deck incubations, and of carbon burial fluxes at three sites in the Southern Adriatic (A1), the Otranto Strait (O2) and the Ionian sea (I1), along the main pathway of outflowing water masses. In this paper, yearly budget calculations of carbon are presented for stations, selected as being representative of wider areas in the three subbasins, to give a picture of the Adriatic basin as a whole. Data from the Northern basin, obtained by the same methodology, come from previous research programmes carried out in the framework of EU Marine projects (STEP/Adria and MTP 1/Euromarge AS). The carbon fraction reaching the seafloor was quantified as the sum of SCOC and burial fluxes and was compared to 14C primary production measurements in the photic zone. Both primary production estimates and carbon respired in the sediment (SCOC) show a clear depth dependence, with the former ranging between 588 g C m -2 year -1 in the Northern shelf off the Po river delta, and 62 g C m -2 year -1 in the Ionian sea, and the latter between 130 and 2 g C m -2 year -1 at the same sites. Burial efficiencies (the ratios of buried carbon to carbon rain) decrease from 47% to 3%. Sediment organic matter lability was investigated through its composition in terms of proteins, lipids and carbohydrates and the sum of their concentrations as expressed in carbon equivalents (biopolimeric carbon fraction, BPC). Compositional differences are clearly indicated between the Northern and the Middle-South Adriatic subbasins due to mixing with terrestrial carbon in the North and longer residence times in the water column in the Middle-South, with the Pomo Pit representing an accumulating site of refractory organic carbon. From carbon budget calculations for the deep sites, taking into account trap measured fluxes to the sediment, lateral input seems to play a role at the deep sites and especially in the Pomo Pit.

Giordani, P.; Helder, W.; Koning, E.; Miserocchi, S.; Danovaro, R.; Malaguti, A.

2002-06-01

291

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...

292

Secondary production of benthic communities at the habitat scale as a tool to assess ecological integrity in mountain streams  

Microsoft Academic Search

Secondary production of the benthic community was estimated in the four functional habitats identified in the pristine Pioverna stream (Northern Italy): riffle, pool, transition and bedrock habitats. The instantaneous growth, removal-summation and size-frequency methods were used to estimate production. Twelve taxa reached appreciable densities and presumably accounted for most of total benthic production. Three of them belong to the Plecoptera,

Andrea Buffagni; Ester Comin

2000-01-01

293

Secondary production of benthic communities at the habitat scale as a tool to assess ecological integrity in mountain streams  

Microsoft Academic Search

Secondary production of the benthic community was estimated in the four functional habitats identified in the pristine Pioverna stream (Northern Italy): riffle, pool, transition and bedrock habitats. The instantaneous growth, removal-summation and size-frequency methods were used to estimate production. Twelve taxa reached appre- ciable densities and presumably accounted for most of total benthic production. Three of them belong to the

Andrea Buffagni; Ester Comin

2000-01-01

294

Reconnaissance of benthic invertebrates from tributary streams of the Yampa and North Platte River basins, northwestern Colorado  

SciTech Connect

The benthic invertebrate communities in selected streams in coal mining areas were described and quantified. Field water-quality measurements, including water temperature, specific conductance, pH, dissolved oxygen, and bed material size were made to aid in assessing the relationship of stream water-quality conditions to benthic invertebrate communities. Density of organisms generally increased downstream in all streams sampled.

Britton, L.J.

1983-01-01

295

CHANGES IN THE FRESHWATER BENTHIC COMMUNITY OF LAKE ONTARIO SINCE THE INVASION OF DREISSENA 1972-1997  

EPA Science Inventory

Population changes of three major benthic taxa are discussed in relation to Dreissena spp. Lake Ontario was sampled pre-invasion (1972) and post-invasion (1994, 1997) for abundance of benthic organisms. In offshore sediments of Lake Ontario, neither species composition nor abunda...

296

New Data on the Stable Isotopes and Vertical Distribution of Benthic Foraminifers in the Western Barents Sea  

Microsoft Academic Search

Despite a wide use of benthic foraminifers in paleoceanographic and paleoclimatic studies, notably in the Arctic seas, their ecology is still poorly known. We studied the distribution of living (Rose Bengal stained) and dead benthic foraminifers, as well as oxygen and carbon isotope composition of monospecific samples in the upper 10 cm of sediment in six box corers retrieved from

E. Yamskova; E. Ivanova; B. Risebrobakken

2006-01-01

297

Importance of benthic production to fish populations in Lake Mead prior to the establishment of quagga mussels  

Microsoft Academic Search

Limnologists recently have developed an interest in quantifying benthic resource contributions to higher-level consumers. Much of this research focuses on natural lakes with very little research in reservoirs. In this study, we provide a contemporary snapshot of the food web structure of Lake Mead to evaluate the contribution of benthic resources to fish consumers. In addition, we document the available

John Umek; Sudeep Chandra; Michael Rosen; Marion Wittmann; Joe Sullivan; Erik Orsak

2010-01-01

298

Comparison of seasonal dynamics of the essential PUFA contents in benthic invertebrates and grayling Thymallus arcticus in the Yenisei river  

Microsoft Academic Search

Seasonal dynamics of contents of essential polyunsaturated fatty acids (PUFA) in dominant groups of benthic invertebrates: gammarids (Gammaridae, Amphipoda), oligochaetes (Oligochaeta), chironomid larvae (Chironomidae, Diptera) and caddisfly larvae (Trichoptera), and dominant benthivorous fish, Siberian grayling Thymallus arcticus, have been studied in ecosystem of the large Siberian river. During the year of the study most benthic invertebrate taxa showed significant variations

N. N. Sushchik; M. I. Gladyshev; G. S. Kalachova; O. N. Makhutova; A. V. Ageev

2006-01-01

299

Bacteria and Foraminifera: key players in a short-term deep-sea benthic response to phytodetritus  

Microsoft Academic Search

The deep-sea floor has long been considered a 'food desert' but recent observations suggest that episodic inputs of relatively fresh organic matter (phytodetritus) occur and that benthic processing of this material may be rapid. Although the responses of the total community in terms of oxygen consumption and of some individual benthic groups have been identified, the quantitative role of the

L. Moodley; J. J. Middelburg; H. T. S. Boschker; GCA Duineveld; R. Pel; P. M. J. Herman; C. H. R. Heip

2002-01-01

300

Benthic foraminifera as bio-indicators of drill cutting disposal in tropical east Atlantic outer shelf environments  

Microsoft Academic Search

We present a study of benthic foraminiferal faunas from the outer continental shelf off Congo (tropical West Africa), with the aim to determine the impact of the discharge of oily drill cuttings on the sea floor environment, to judge the regenerating capacity of the benthic ecosystem, and to investigate the possibility to develop an environmental monitoring method for open marine

M. Mojtahid; F. Jorissen; J. Durrieu; F. Galgani; H. Howa; F. Redois; R. Camps

2006-01-01

301

Benthic foraminiferal evidence for the formation of the Holocene mud-belt and bathymetrical evolution in the central Adriatic Sea  

Microsoft Academic Search

Detailed analyses of modern and fossil benthic foraminiferal assemblages collected in the central Adriatic Sea are used as tools to reconstruct the environmental changes that occurred between the Last Deglaciation and the Present (last 14 Kyrs); in particular we focus on the timing and formation of the mud-belt. The modern benthic foraminiferal assemblages display a parallel zonation to the Italian

Caterina Morigi; Frans J. Jorissen; Simona Fraticelli; Benjamin P. Horton; Mirko Principi; Anna Sabbatini; Lucilla Capotondi; Pietro V. Curzi; Alessandra Negri

2005-01-01

302

Seasonal variation in benthic community oxygen demand: A response to an ice algal bloom in the Beaufort Sea, Canadian Arctic?  

Microsoft Academic Search

Understanding pathways of carbon cycling on Arctic shelves is critical if we are to evaluate the potential effects of climate change on these systems. We investigated the relationship between ice algal standing stock and benthic respiration between January and July 2004 at a time series station in the southeastern Beaufort Sea. Both ice algal chlorophyll a and benthic sediment oxygen

Paul E. Renaud; Andrea Riedel; Christine Michel; Nathalie Morata; Michel Gosselin; Thomas Juul-Pedersen; Amy Chiuchiolo

2007-01-01

303

A conceptual model for the growth, persistence, and blooming behavior of the benthic mat-forming diatom Didymosphenia geminata (Invited)  

Microsoft Academic Search

The nuisance diatom Didymosphenia geminata (didymo) presents an ecological paradox. How can this benthic algae produce such large amounts of biomass in cold, fast flowing, low nutrient streams? The aim of this paper is to present a conceptual model for the growth, persistence, and blooming behavior of this benthic mat-forming diatom that may help to explain this paradox. The conceptual

J. D. Cullis; C. Gillis; M. Bothwell; C. Kilroy; A. I. Packman; M. A. Hassan

2010-01-01

304

Development of a regional littoral benthic macroinvertebrate multi-metric index (MMI) for lakes from the National Lakes Assessment  

EPA Science Inventory

During the 2007 National Lakes Assessment (NLA) benthic macroinvertebrate samples were collected from the lake littoral zone. The purpose of the sampling was to assess the feasibility of a multi-metric index (MMI) to assess the condition of the littoral benthic macroinvertebrate...

305

Assessment of a Mediterranean shallow lentic ecosystem (Lake Pamvotis, Greece) using benthic community diversity: Response to environmental parameters  

Microsoft Academic Search

Macroinvertebrates play a key role in freshwater lentic and lotic ecosystems. The macroinvertebrate benthic community of a shallow Mediterranean lake (Lake Pamvotis, NW Greece) was studied. The benthic assemblage was sampled monthly at five sites during a period of 1 year (Apr. 1998–Mar. 1999). In addition hypolimnetic water quality variables were monitored over the same period at each site.The aim

Ifigenia Kagalou; Georgios Economidis; Ioannis Leonardos; Constantinos Papaloukas

2006-01-01

306

Methods for collecting benthic invertebrate samples as part of the National Water-Quality Assessment Program  

USGS Publications Warehouse

Benthic invertebrate communities are evaluated as part of the ecological survey component of the U.S. Geological Survey's National Water-Quality Assessment Program. These biological data are collected along with physical and chemical data to assess water-quality conditions and to develop an understanding of the factors that affect water-quality conditions locally, regionally, and nationally. The objectives of benthic invertebrate community characterizations are to (1) develop for each site a list of tax a within the associated stream reach and (2) determine the structure of benthic invertebrate communities within selected habitats of that reach. A nationally consistent approach is used to achieve these objectives. This approach provides guidance on site, reach, and habitat selection and methods and equipment for qualitative multihabitat sampling and semi-quantitative single habitat sampling. Appropriate quality-assurance and quality-control guidelines are used to maximize the ability to analyze data within and among study units.

Cuffney, Thomas F.; Gurtz, Martin E.; Meador, Michael R.

1993-01-01

307

Swept away: resuspension of bacterial mats regulates benthic-pelagic exchange of sulfur.  

PubMed

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. PMID:17793235

Grant, J; Bathmann, U V

1987-06-12

308

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

NASA Astrophysics Data System (ADS)

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.

Grant, Jonathan; Bathmann, Ulrich V.

1987-06-01

309

Crater lake cichlids individually specialize along the benthic-limnetic axis  

PubMed Central

A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of elongated open water (limnetic) species and high-bodied shore (benthic) species from generalist ancestors. Studies on phenotype-diet correlations have suggested that population-wide individual specialization occurs at an early evolutionary and ecological stage of divergence and niche partitioning. This variable restricted niche use across individuals can provide the raw material for earliest stages of sympatric divergence. We investigated variation in morphology and diet as well as their correlations along the benthic-limnetic axis in an extremely young Midas cichlid species, Amphilophus tolteca, endemic to the Nicaraguan crater lake Asososca Managua. We found that A. tolteca varied continuously in ecologically relevant traits such as body shape and lower pharyngeal jaw morphology. The correlation of these phenotypes with niche suggested that individuals are specialized along the benthic-limnetic axis. No genetic differentiation within the crater lake was detected based on genotypes from 13 microsatellite loci. Overall, we found that individual specialization in this young crater lake species encompasses the limnetic-as well as the benthic macro-habitat. Yet there is no evidence for any diversification within the species, making this a candidate system for studying what might be the early stages preceding sympatric divergence. A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of open water (limnetic) species and of shore (benthic) species. Individual specialization can reflect earliest stages of evolutionary and ecological divergence. We here demonstrate individual specialization along the benthic–limnetic axis in a young adaptive radiation of crater lake cichlid fishes.

Kusche, Henrik; Recknagel, Hans; Elmer, Kathryn Rebecca; Meyer, Axel

2014-01-01

310

Multiscale patterns in the diversity and organization of benthic intertidal fauna among French Atlantic estuaries  

NASA Astrophysics Data System (ADS)

Based on a parallel sampling conducted during autumn 2008, a comparative study of the intertidal benthic macrofauna among 10 estuarine systems located along the Channel and Atlantic coasts of France was performed in order to assess the level of fauna similarity among these sites and to identify possible environmental factors involved in the observed pattern at both large (among sites) and smaller (benthic assemblages) scales. More precisely this study focused on unraveling the observed pattern of intertidal benthic fauna composition and diversity observed at among-site scale by exploring both biotic and abiotic factors acting at the among- and within-site scales. Results showed a limited level of similarity at the among-site level in terms of intertidal benthic fauna composition and diversity. The observed pattern did not fit with existing transitional water classification methods based on fish or benthic assemblages developed in the frame of the European Water Framework Directive (WFD). More particularly, the coastal plain estuaries displayed higher among-site similarity compared to ria systems. These coastal plain estuaries were characterized by higher influence of river discharge, lower communication with the ocean and high suspended particulate matter levels. On the other hand, the ria-type systems were more dissimilar and different from the coastal plain estuaries. The level of similarity among estuaries was mainly linked to the relative extent of the intertidal “Scrobicularia plana-Cerastoderma edule” and “Tellina tenuis” or “Venus” communities as a possible consequence of salinity regime, suspended matter concentrations and fine particles supply with consequences on the trophic functioning, structure and organization of benthic fauna. Despite biogeographical patterns, the results also suggest that, in the context of the WFD, these estuaries should only be compared on the basis of the most common intertidal habitat occurring throughout all estuarine systems and that the EUNIS biotope classification might be used for this purpose. In addition, an original inverse relation between ?-diversity and area was shown; however, its relevance might be questioned.

Blanchet, Hugues; Gouillieux, Benoît; Alizier, Sandrine; Amouroux, Jean-Michel; Bachelet, Guy; Barillé, Anne-Laure; Dauvin, Jean-Claude; de Montaudouin, Xavier; Derolez, Valérie; Desroy, Nicolas; Grall, Jacques; Grémare, Antoine; Hacquebart, Pascal; Jourde, Jérôme; Labrune, Céline; Lavesque, Nicolas; Meirland, Alain; Nebout, Thiebaut; Olivier, Frédéric; Pelaprat, Corine; Ruellet, Thierry; Sauriau, Pierre-Guy; Thorin, Sébastien

2014-07-01

311

Crater lake cichlids individually specialize along the benthic-limnetic axis.  

PubMed

A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of elongated open water (limnetic) species and high-bodied shore (benthic) species from generalist ancestors. Studies on phenotype-diet correlations have suggested that population-wide individual specialization occurs at an early evolutionary and ecological stage of divergence and niche partitioning. This variable restricted niche use across individuals can provide the raw material for earliest stages of sympatric divergence. We investigated variation in morphology and diet as well as their correlations along the benthic-limnetic axis in an extremely young Midas cichlid species, Amphilophus tolteca, endemic to the Nicaraguan crater lake Asososca Managua. We found that A. tolteca varied continuously in ecologically relevant traits such as body shape and lower pharyngeal jaw morphology. The correlation of these phenotypes with niche suggested that individuals are specialized along the benthic-limnetic axis. No genetic differentiation within the crater lake was detected based on genotypes from 13 microsatellite loci. Overall, we found that individual specialization in this young crater lake species encompasses the limnetic-as well as the benthic macro-habitat. Yet there is no evidence for any diversification within the species, making this a candidate system for studying what might be the early stages preceding sympatric divergence. A common pattern of adaptive diversification in freshwater fishes is the repeated evolution of open water (limnetic) species and of shore (benthic) species. Individual specialization can reflect earliest stages of evolutionary and ecological divergence. We here demonstrate individual specialization along the benthic-limnetic axis in a young adaptive radiation of crater lake cichlid fishes. PMID:24772288

Kusche, Henrik; Recknagel, Hans; Elmer, Kathryn Rebecca; Meyer, Axel

2014-04-01

312

Benthic foraminifera as indicators of pollution in high latitude marine environments  

NASA Astrophysics Data System (ADS)

An increasing number of studies demonstrate the potential of benthic foraminifera to characterize ecological status. However, the use of benthic foraminifera as bio-indicators has previously not been tested in high latitudes. This research contributes to the development of foraminifera as a bio-monitoring technique for the Arctic region, as industrial activities in this region will increase in the coming years. Surface sediments (0-1 cm) from sites close to gas fields in the SW Barents Sea were studied. In addition, to elucidate the range from less to very affected, surface sediments from the harbor of the town of Hammerfest (70° N) were studied. At least 300 living benthic foraminifera from the size fraction 100 µm-1 mm were counted and identified at species level. Pollution levels (heavy metals and persistent organic pollutants) and sediment properties (grainsize and TOC) were also analyzed. Pollution levels at the sea floor in the SW Barents Sea are of background to good level (level I-II) according to the definitions by the Water Framework Directorate (WFD). Benthic foraminiferal assemblages are influenced by natural environmental parameters such as water mass properties, water depth, nutrient availability, bottom current strength, and grain size. Surface sediments from the Hammerfest harbor are of moderate environmental status (WFD level II-III) based on heavy metal concentrations and of bad environmental status (WFD IV-V) based on persistent organic pollutant concentrations. Opportunistic benthic foraminifera are dominating the assemblages. The most polluted areas in the harbor are barren for foraminifera or have high amounts of deformed shells. In both environments the foraminiferal diversity of the samples, does not correspond to expected environmental status based on the pollution levels of the sediments. Environmental status classes, based on benthic foraminifera instead of macrofauna, would allow rapid analyses of the environmental impact of pollution.

Dijkstra, N.; Junttila, J.; Husum, K.; Carroll, J.; Klitgaard-Kristensen, D.; Hald, M.

2012-04-01

313

Spatial variation in density of stream benthic fishes in northern Hokkaido, Japan: does riparian vegetation affect fish density via food availability?  

Microsoft Academic Search

The densities of two benthic fishes, the Siberian stone loach (Noemacheilus barbatulus) and the wrinklehead sculpin (Cottus nozawae), and the biomass of their food resources (i.e., periphyton and benthic invertebrates) were compared between forest and grassland streams in northern Hokkaido, Japan, to examine whether riparian deforestation had positive effects on the benthic fishes via enhancement of food availability. The comparisons

Mikio Inoue; Masanori Nunokawa

2005-01-01

314

Residual concentrations of micropollutants in benthic mussels in the coastal areas of Bohai Sea, North China.  

PubMed

Studies of heavy metals and organic pollutants in different benthic mussel species from Bohai Sea show that concentrations of Cd in mussels commonly exceed national biological quality standards. In addition, a site located in Laizhou Bay exhibits higher average concentrations of As, Hg and Pb with respect to the other sites. Residual levels of petroleum hydrocarbons at several sites in Liaodong Bay also exceed quality guidelines. Contents and compositional characteristics of DDT and its metabolites in mussels suggest the probability of recent inputs and potential ecological risks to the local benthic environment. PMID:16950550

Liu, WenXin; Chen, JiangLin; Lin, XiuMei; Fan, YongSheng; Tao, Shu

2007-03-01

315

Effects of gut sediment contents on measurements of metal levels in benthic invertebrates - a cautionary note  

SciTech Connect

Studies of heavy metal levels in benthic organisms typically do not correct for gut sediment metal levels other than by allowing a period of depuration in clean water. The effectiveness of depuration has recently been questioned in British Columbia in the particular case of the marine clam Yoldia. In light of this controversy, it appears appropriate to present data from a study of heavy metal levels in sediments and benthic organisms in the Lower Fraser River, BC, regarding the effects of gut sediment contents.

Chapman, P.M.

1985-09-01

316

Benthic invertebrate communities in the fluctuating riverine habitat below Conowingo Dam. Final report  

SciTech Connect

This report summarizes the findings of a benthic invertebrate study conducted on the Susquehanna River in the vicinity of the Conowingo Dam and hydroelectric generating station. Variations in the release of water from hydroelectric projects can strongly affect the availability of suitable habitats for downstream benthic invertebrates. To examine the extent of this problem in the Susquehanna River below Conowingo reservoir, basket samples were deployed along four transects in three habitats: constantly submerged channels, pools that become isolated at low flow, and areas exposed at low flow. Samplers were incubated for 3-week periods from June through October.

Janicki, A.J.; Ross, R.N.

1982-03-01

317

Sequential sampling: cost-effective approach for monitoring benthic macroinvertebrates in environmental impact assessements  

SciTech Connect

Sequential sampling is a method for monitoring benthic macroinvertebrates that can significantly reduce the number of samples required to reach a decision, and consequently, decrease the cost of benthic sampling in environmental impact assessments. Rather than depending on a fixed number of samples, this analysis cumulatively compares measured parameter values (for example, density, community diversity) from individual samples, with thresholds that are based on specified degrees of precision. In addition to reducing sample size, a monitoring program based on sequential sampling can provide clear-cut decisions as to whether a priori-defined changes in the measured parameter(s) have or have not occurred.

Resh, V.H.; Price, D.G.

1984-01-01

318

Benthic macrofauna and ancillary data for San Francisco Bay, California, March to November 1987  

USGS Publications Warehouse

Benthic macrofauna and ancillary data were collected during 1987 as part of the U.S. Geological Survey Regional Effects Monitoring Program in San Francisco Bay, California. Data were collected during five cruises at 2-month intervals from March through November. Benthic macrofauna for identification of species and sediment for size analysis were sampled at eight stations. Ancillary data, which consisted of salinity, temperature, dissolved-oxygen concentrations, and suspended sediment, were collected at 12 stations. Salinity and temperature were measured at three stations that coincided with continuous water quality monitors. Abundances and geographical distributions of a newly introduced species of clam were measured. (USGS)

Schemel, Laurence E.; Ota, A. Y.; Harmon, J. G.; Shay, J. M.; Adorado,R. N.

1988-01-01

319

Correspondence of stream benthic invertebrate assemblages to regional classification schemes in Missouri  

USGS Publications Warehouse

Benthic invertebrates from 44 reference streams throughout the state of Missouri were examined for their concordance with established regionalization systems, both aquatic and terrestrial. Invertebrate assemblages coincided nicely with Pflieger's established aquatic faunal regions system, expanding its generality to more than fish assemblages. Our benthic invertebrate and Pflieger's fish assemblages coincided well with both Bailey's ecological sections and Omernik's ecoregions. Subregionalization using Pflieger's subregions and Bailey's subsections further reduced unexplained variation and is recommended for use wherever possible. The concordance of the aquatic fauna and terrestrial features implies the possibility of coordinated regional management among different natural resource disciplines.

Rabeni, C. F.; Doisy, K. E.

2000-01-01

320

Distribution and abundance of benthic organisms in the Sacramento River, California  

USGS Publications Warehouse

General comparisons were made between benthic organism samples collected in 1960-61 and 1972-73 from five sites in the Sacramento River between Red Bluff and Knights Landing, Calif. The composition of benthic organisms from both collection periods was similar. The 1972-73 data showed variable patterns in monthly changes at each site and downstream changes each month with number of organisms per square meter, number of taxa per square meter, and diversity index. Generally, the mean number of taxa per square meter and diversity index for all sampling periods were higher in the upper reach than the lower reach of the Sacramento River. (Woodard-USGS)

Ferreira, Rodger F.; Green, D. Brady

1977-01-01

321

Multiple tube sampler for benthic and pelagic invertebrates in shallow wetlands  

USGS Publications Warehouse

Sampling devices that minimize bias and function in aquatic habitats used by waterfowl are needed. We devised a multiple tube sampling device for quantitative sampling of small (<3 cm) aquatic invertebrates in wetlands. The sampler reduced bias associated with sampling macroinvertebrates that utilize the benthic-pelagic interface because it simultaneously collects benthic and water column invertebrates. The sampler was statistically superior to other sampling devices because each sampling effort provided 4 subsamples and a within-sample variance that could be estimated. The device also was durable and reasonably inexpensive to construct.

Euliss, N. H., Jr.; Swanson, G. A.; MacKay, J.

1992-01-01

322

Fatty acid profiles of marine benthic microorganisms isolated from the continental slope of bay of bengal: a possible implications in the benthic Food web  

Microsoft Academic Search

Marine bacteria, actinomycetes and fungal strains were isolated from continental slope sediment of the Bay of Bengal and studied\\u000a for fatty acid profile to investigate their involvement in the benthic food-web. Fifteen different saturated and unsaturated\\u000a fatty acids from bacterial isolates, 14 from actinomycetes and fungal isolates were detected. The total unsaturated fatty\\u000a acids in bacterial isolates ranged from 11.85

Surajit Das; P. S. Lyla; S. Ajmal Khan

2007-01-01

323

The relation between invertebrate drift and two primary controls, discharge and benthic densities, in a large regulated river  

USGS Publications Warehouse

1. Invertebrate drift is a fundamental process in streams and rivers. Studies from laboratory experiments and small streams have identified numerous extrinsic (e.g. discharge, light intensity, water quality) and intrinsic factors (invertebrate life stage, benthic density, behaviour) that govern invertebrate drift concentrations (# m?3), but the factors that govern invertebrate drift in larger rivers remain poorly understood. For example, while large increases or decreases in discharge can lead to large increases in invertebrate drift, the role of smaller, incremental changes in discharge is poorly described. In addition, while we might expect invertebrate drift concentrations to be proportional to benthic densities (# m?2), the benthic–drift relation has not been rigorously evaluated. 2. Here, we develop a framework for modelling invertebrate drift that is derived from sediment transport studies. We use this framework to guide the analysis of high-resolution data sets of benthic density and drift concentration for four important invertebrate taxa from the Colorado River downstream of Glen Canyon Dam (mean daily discharge 325 m3 s?1) that were collected over 18 months and include multiple observations within days. Ramping of regulated flows on this river segment provides an experimental treatment that is repeated daily and allowed us to describe the functional relations between invertebrate drift and two primary controls, discharge and benthic densities. 3. Twofold daily variation in discharge resulted in a >10-fold increase in drift concentrations of benthic invertebrates associated with pools and detritus (i.e. Gammarus lacustris and Potamopyrgus antipodarum). In contrast, drift concentrations of sessile blackfly larvae (Simuliium arcticum), which are associated with high-velocity cobble microhabitats, decreased by over 80% as discharge doubled. Drift concentrations of Chironomidae increased proportional to discharge. 4. Drift of all four taxa was positively related to benthic density. Drift concentrations of Gammarus, Potamopyrgus and Chironomidae were proportional to benthic density. Drift concentrations of Simulium were positively related to benthic density, but the benthic–drift relation was less than proportional (i.e. a doubling of benthic density only led to a 40% increase in drift concentrations). 5. Our study demonstrates that invertebrate drift concentrations in the Colorado River are jointly controlled by discharge and benthic densities, but these controls operate at different timescales. Twofold daily variation in discharge associated with hydropeaking was the primary control on within-day variation in invertebrate drift concentrations. In contrast, benthic density, which varied 10- to 1000-fold among sampling dates, depending on the taxa, was the primary control on invertebrate drift concentrations over longer timescales (weeks to months).

Kennedy, Theodore A.; Yackulic, Charles B.; Cross, Wyatt F.; Grams, Paul E.; Yard, Michael D.; Copp, Adam J.

2014-01-01

324

Similarity & Instability in Flows Over Permeable Layers (Invited)  

NASA Astrophysics Data System (ADS)

Permeable obstructions (such as seagrass meadows) are prevalent in the benthic region of freshwater and coastal environments. Their impact on the near-bed flow, turbulence and vertical transport is profound. Here, I use particle imaging and point velocity measurements in both steady and oscillatory flows to demonstrate three salient features of environmental flows over permeable layers: (1) A framework developed for vegetation canopies has the capacity to predict flow, turbulence and mixing properties over a wide range of permeable layers (from sediment beds to coral reefs to 'urban' canopies to ancient rangeomorph communities). (2) Steady flows are characterized by the development of a Kelvin-Helmholtz-type instability at the interface between the permeable layer and the free flow. These coherent structures dominate vertical mixing at the interface and generate regular oscillations in flow and transport. The height of the permeable layer relative to its drag length scale defines three regimes of obstructed shear flow. (3) Such instability is also observed in oscillatory flow when both the Reynolds and Keulegan-Carpenter numbers exceed threshold values. This is important in the prediction of residence time in ecologically-significant benthic habitats that exist in shallow (and therefore, typically, wave-dominated) coastal regions.

Ghisalberti, M.

2013-12-01

325

RAPID ASSESSMENT OF RIVER WATER QUALITY IN TURKEY USING BENTHIC MACROINVERTEBRATES  

Microsoft Academic Search

SUMMARY A study of the relationship between benthic macro- invertebrates and water quality parameters, such as bio- chemical oxygen demand (BOD), chemical oxygen de- mand (COD) and dissolved oxygen (DO), in a river in Turkey was carried out in order to assess the ecological impact of polluted water discharge into rivers. Five sam- pling stations were selected on the river;

Sinan Uyanik; Guzel Yilmaz; M. Irfan Yesilnacar; Mustafa Aslan; Ozlem Demir

2005-01-01

326

Benthic macroinvertebrate populations of urban freshwater tidal wetlands in the Anacostia River, Washington D.C  

Microsoft Academic Search

This study characterizes the benthic communities establishing themselves on recently reconstructed urban freshwater tidal wetlands along the Anacostia River in Washington, D.C. in comparison to a similar relic wetland as well as to a reference wetland in the adjacent Patuxent River watershed. The study's focus is the two main areas of Kingman Marsh, which were reconstructed from Anacostia dredge material

K. D. Brittingham

2005-01-01

327

THE INFLUENCE OF SIEVE MESH SIZE SELECTIVITY ON BENTHIC INVERTEBRATE INDICES OF EUTROPHICATION  

EPA Science Inventory

The selective retention of benthic invertebrates by sieves of various mesh sizes was demonstrated by Jonasson (1955, 1958) who reported that decreasing the mesh opening from 0.62 to 0.51 mm (effective decrease on one-third mesh opening area) resulted in samples with an average of...

328

OPTIMUM BENTHIC MACROFAUNAL SAMPLING PROTOCOL FOR DETECTING DIFFERENCES BETWEEN FOUR HABITATS IN WILLAPA BAY, WASHINGTON, USA  

EPA Science Inventory

Abstract -- As part of an effort to estimate estuarine habitat values with respect to ecological indicators of benthic macrofaunal community condition, an optimal (effective and least costly) sampling protocol (sample unit size [area 3 depth], sieve mesh size, and sample number [...

329

Biological modifiers of marine benthic seascapes: Their role as ecosystem engineers  

NASA Astrophysics Data System (ADS)

Benthic organisms in marine ecosystems modify the environment on different spatial and temporal scales. These modifications, many of which are initially at a microscale, are likely to have large scale effects on benthic seascapes. This is especially so if the species are ecosystem engineers. Most species of infaunal and epifaunal invertebrates and macrophytes contribute at a geophysical or geochemical level. Microorganisms also play a key but currently neglected role. In the intertidal and immediately sublittoral zone, algae and seagrasses, and mussels in mussel beds have received considerable attention. A substantial fossil record also exists. Mathematical modelling of these systems is still in its infancy, although several sophisticated mathematical tools have been applied. The effects of bioturbation and of microorganisms have been less studied, and little is known about the activities of benthic organisms in the deep sea. This paper addresses all these effects, and places them in the context of large scale benthic seascapes and of the extensive literature on species defined as ecosystem engineers in the sea.

Meadows, Peter S.; Meadows, Azra; Murray, John M. H.

2012-07-01

330

ESTIMATING DENSITIES OF ESTUARINE EELGRASS AND BENTHIC MACROALGAE VIA AERIAL PHOTOGRAPHY  

EPA Science Inventory

The goal of this research was to distinguish meadows of native eelgrass (Zostera marina L.) from adjacent beds of benthic green macroalgae in the exposed intertidal zone of Pacific Northwest estuaries, using false-color near-infrared aerial photography. Aerial photographs of Yaq...

331

The Relative Abundance of Opossum Shrimp, Mysis relicta, in Twin Lakes, Colorado Using a Benthic Trawl..  

National Technical Information Service (NTIS)

The study of the opossum shrimp (Mysis relicta) at Twin Lakes, Colo., is part of an investigation into the potential impacts of pumped-storage power generation on the two lakes. Since 1974, large and small benthic sled-type trawls have been used monthly t...

T. P. Nesler

1981-01-01

332

Arsenic in benthic bivalves of San Francisco Bay and the Sacramento\\/San Joaquin River Delta  

Microsoft Academic Search

Arsenic concentrations were determined in fine-grained, oxidized, surface sediments and in two benthic bivalves, Corbicula sp. and Macoma balthica, within San Francisco Bay, the Sacramento\\/ San Joaquin River Delta, and selected rivers not influenced by urban or industrial activity. Arsenic concentrations in all samples were characteristic of values reported for uncontaminated estuaries. Small temporal fluctuations and low arsenic concentrations in

CAROLYN JOHNS; SAMUEL N. LUOMA

1990-01-01

333

Mapping coral reef benthic substrates using hyperspectral space-borne images and spectral libraries  

Microsoft Academic Search

The suitability of Hyperion, the first civilian hyperspectral sensor in space, for mapping coral reef benthic substrates has been investigated in this study. An image of Cairns Reef, in the northern section of the Australian Great Barrier Reef (GBR), was acquired during Hyperion Calibration and Validation activities. A field experiment was carried out on Cairns Reef to collect information about

Tiit Kutser; Ian Miller; David L. B. Jupp

2006-01-01

334

A nutrient biotic index (NBI) for use with benthic macroinvertebrate communities  

Microsoft Academic Search

Aquatic macroinvertebrates have been among the principal biological communities used for freshwater monitoring and assessment for several decades, but macroinvertebrate biomonitoring has not incorporated nutrient measures into assessment strategies. Two nutrient biotic indices were developed for benthic macroinvertebrate communities, one for total phosphorus (NBI-P), and one for nitrate (NBI-N). Weighted averaging was used to assess the distributions of 164 macroinvertebrate

Alexander J. Smith; Robert W. Bode; Gary S. Kleppel

2007-01-01

335

Water quality in rivers of western Switzerland: Application of an adaptable index based on benthic invertebrates  

Microsoft Academic Search

Water quality was estimated from 205 samples of benthic invertebrates collected between 1982 and 1986 in 51 rivers of western Switzerland (canton of Vaud). Each sample consisted of the combined list of taxa resulting from one spring sample pooled with one summer sample. Water quality was indicated by total number of taxa and number of taxa intolerant of pollution: i.

Claude Lang; Geneviève l'Eplattenier; Olivier Reymond

1989-01-01

336

Hyperspectral discrimination of coral reef benthic communities in the western Caribbean  

Microsoft Academic Search

Determining a subset of wavelengths that best discriminates reef benthic habitats and their associated communities is essential for the development of remote sensing techniques to monitor them. This study measured spectral reflectance from 17 species of western Caribbean reef biota including coral, algae, seagrasses, and sediments, as well as healthy and diseased coral. It sought to extend the spectral library

Evanthia Karpouzli; Tim J. Malthus

2004-01-01

337

Biological Indicators of Marine Environmental Health: Meiofauna – A Neglected Benthic Component?  

Microsoft Academic Search

This paper considers the use of meiofauna (benthic metazoa 45 to 500 µm in size) as biological indicators for monitoring marine environmental health. To date, this abundant and ubiquitous group of invertebrates has been largely neglected in applied sampling programmes; instead, emphasis has been placed upon more conspicuous biological components such as seagrass, macrofauna and epiphytes. In an attempt to

Andrew D. Kennedy; Charles A. Jacoby

1999-01-01

338

Temporal variations of benthic diatom community and its main influencing factors in a subtropical river, China.  

PubMed

Benthic diatoms are the main component in many aquatic ecosystems such as streams, creeks and rivers, and they function as important primary producers and chemical modulators for other organisms in the ecosystems. In this study, the composition of benthic diatoms was investigated and further explored the primary physicals and chemicals affecting their temporal variations in the upper Han River, China. There were seasonal variations in physical and chemical variables in waters over the sampling period of 2007-2010. Water temperature (t), chemical oxygen demand, total nitrogen, dissolved organic carbon (DOC), silica and fluoride were much higher in the high flow season (i.e., July or August) than these in the base flow season. Three species Achnanthidium minutissimum (composed of 10.7% of the total diatom abundance), Achnanthidium pyrenaicum (11.9%), and Achnanthidium subatomus (12.7%) accounting for more than 5% of the total diatom abundance were persistently dominant in all seasons, while the other two prostrate and motile species including Eolimna minima and Nitzschia dissipata also dominant in the base flow season. The species richness always peaked in autumn with significant difference with summer (p?benthic diatom varied and peaked in April. Analyses indicated that the temporal variation in benthic diatom communities was strongly related to t, nitrogen, organic pollutants (indicated by COD and DOC), and hydrological regime. The research will expand the understanding of water chemistry monitoring, and improve watershed- scale management and conservation efforts in the upper Han River, China. PMID:23794080

Tan, Xiang; Xia, Xiaoling; Zhao, Qiaoling; Zhang, Quanfa

2014-01-01

339

Distribution of Benthic Foraminifers (< 125 mu m) in the Surface Sediments of the Arctic Ocean.  

National Technical Information Service (NTIS)

Census data on benthic foraminifers (>125 Micrometers) in surface sediment samples from 49 box cores are used to define four depth-controlled biofacies, which will aid in the pale-oceanographic reconstruction of the Arctic Ocean. The shelf biofacies conta...

L. E. Osterman R. Z. Poore K. M. Foley

1998-01-01

340

Application of a Eutrophic Condition Index to Benthic Macroalgal Accumulation in Pacific Northwest Estuaries  

EPA Science Inventory

Studies of benthic macroalgal accumulation in coastal estuaries of the Pacific Northwest, USA, were conducted over a 12-year period, including aerial mapping and ground surveys. The results were applied to an assessment framework for eutrophication developed by the European Unio...

341

Nutritional value of different food sources for the benthic Daphnidae Simocephalus vetulus : role of fatty acids  

Microsoft Academic Search

In this experimental study, growth, survival and fecundity of the benthic Cladoceran Simocephalus vetulus were measured when feeding on Cryptomonas ovata, Paraphysomonas vestita, Cyclidium glaucoma and particulate amorphous organic matter to investigate the nutritional value of these food sources. Cladocerans fed Cr. ovata (autotrophic flagellate) exhibited the highest fecundity and growth. Par- ticulate organic matter (POM, mainly composed of detrital

Alexandre Bec; Christian Desvilettes; Aurelie Véra; Dominique Fontvieille; Gilles Bourdier

2003-01-01

342

24. BENTHIC FORAMINIFERS AND PALEOBATHYMETRY OF THE JAPAN TRENCH AREA, LEG 57, DEEP SEA DRILLING PROJECT  

Microsoft Academic Search

Deep sea drilling in the Japan Trench area recovered a Late Cretaceous to Pleistocene sedimentary and biostratigraphic record unraveling the tectonic and paleobathymetric history of the conver- gent margin. Benthic foraminiferal assemblages spanning the Late Cretaceous to the late Pleistocene permit reconstruction of the paleo- bathymetric history of this area. During the Late Cretaceous a deep bathyal environment persisted, characterized

Gerta Keller

343

Development of Benthic Indicators for Nearshore Coastal Waters of New Jersey - A REMAP Project  

EPA Science Inventory

EPA's National Coastal Assessment (NCA) is providing the first complete, consistent dataset on the condition of benthic communities in the nation's estuaries. Prior to NCA, New Jersey based its evaluation of the ecological condition of its coastal waters solely on dissolved oxyg...

344

IMPERVIOUS SURFACE AREA AND BENTHIC MACROINVERTEBRATE RESPONSE AS INDEX OF IMPACT FROM URBANIZATION ON FRESHWATER WETLANDS  

EPA Science Inventory

The use of benthic macroinvertebrates to monitor water quality and ecological integrity is not as well established for wetlands as it is for rivers, streams and lakes where this form of biomonitoring is now a formalized procedure. he impact to wetlands from urbanization (as measu...

345

The development of a benthic foraminiferal quantitative transfer function in the Barents Sea  

Microsoft Academic Search

An important approach being utilised in paleoclimate research is the construction of mathematical transfer functions to quantitatively reconstruct the environmental variables of the past. Recent work within the Barents Sea region, based on the Steinsund and Hald (1994) benthic foraminferal database and with additional work by S. Korsun, attempted to establish a transfer function based on faunal data collated from

L. J. Wilson; M. Saher; D. Klitgaard Kristensen; M. Hald; L. L. Jørgensen

2009-01-01

346

Feedbacks between oceanic redox states and marine productivity: A model perspective focused on benthic phosphorus cycling  

Microsoft Academic Search

A new model for the marine cycles of particulate organic carbon (POC), oxygen, nitrate, and phosphorus has been developed and applied to explore the controls and constraints on marine productivity and nutrient inventories. The coupled benthic-pelagic model uses a new approach for the simulation of the reactive phosphorus turnover (Preac corresponding to the sum of organic P, authigenic P, and

K. Wallmann

2003-01-01

347

Evaluating Benthic Survey Techniques for Validating Maps of Coral Reefs Derived from Remotely Sensed Images  

Microsoft Academic Search

Field validation of maps derived from airborne or satellite imagery is essential to enable their use for monitoring and managing coral reef habitats. Methods of benthic survey in coral reef ecosystems have been documented elsewhere, yet a comparative evaluation of methods for integrating field data with remote sensing has not been completed. In addition to meeting standard field survey requirements,

Chris M. ROELFSEMA; Stuart R. PHINN

348

Surficial bioturbation and rapid benthic remineralization in the Cape Hatteras shelf/slope region. Final report.  

National Technical Information Service (NTIS)

This is a final report for the DOE of grant DE-FG02-92ER61464 'Surficial bioturbation and rapid benthic remineralization in the Cape Hatteras shelf slope region'. Over the past 6 years we have participated in a multidisciplinary field study called the Oce...

R. C. Aller J. Y. Aller C. Lee J. K. Cochran

1999-01-01

349

Benthic Responses to Wet-Weather Discharges in Urban Streams in Southern Ontario  

Microsoft Academic Search

Urban stormwater and combined sewer overflow (CSO) discharges are important sources of sediment and contaminants (trace metals, PAHs, nutrients and road salts), and cause changes in flow, sediment, chemical and thermal regimes of receiv- ing waters. Over the past several years, benthic conditions of streams representing a range of exposure environments were assessed in Hamilton, Toronto, Oshawa and Kingston, Ontario.

Lee Grapentine; Quintin Rochfort; Jiri Marsalek

2004-01-01

350

Benthic invertebrate population characteristics as affected by water quality in coal-bearing regions of Tennessee  

SciTech Connect

Linear regressions produced low correlation coefficients relating the number of taxa/sample, total number of organisms/sample, sample diversity, and percentage composition of selected orders of invertebrates, with average water quality parameter values available at sampling stations. Analyses of these data by linear regressions explained little of the variability in benthic invertebrate samples primarily because the distributions of benthic organisms along environmental gradients are nonlinear. Variability in substrate characteristics in the study area and seasonal insect emergence patterns also complicated interpretation of these data. However, analysis of variance tests did indicate significant trends towards reduced number of taxa, number of organisms, and sample diversity at stations with relatively poor water quality conditions. Decreasing percentage composition of Ephemeroptera was generally accompanied by an increase in percent Diptera at stations with higher water quality constituent concentrations and acidic pH. These trends indicate significant differences in benthic communities at sites with evidence of more severe land use impacts. Additional data on benthic invertebrates, water quality, and physical habitat conditions, along with analyses of data using multivariate statistical methods are needed to define ecological relations between specific groups of invertebrates and environmental conditions. 44 refs., 1 fig., 8 tabs.

Bradfield, A.D.

1986-01-01

351

Microcystin production in benthic mats of cyanobacteria in the Nile River and irrigation canals, Egypt  

Microsoft Academic Search

The present study describes for the first time the species composition and toxicity of benthic cyanobacteria forming mats on the Nile River and irrigation canal sediments in Egypt. A total of 19 species of cyanobacteria were isolated from these mats during this study. The toxicity of the extracts of these species was investigated using Artemia salina assay, mouse bioassay and

Zakaria A. Mohamed; Hassan M. El-Sharouny; Wafaa S. M. Ali

2006-01-01

352

Propagule transport as a key method of dispersal in benthic foraminifera (Protista)  

Microsoft Academic Search

The distributional patterns of benthic foraminifera provide key information for paleoclimatic, paleoecologic, and paleoceanographic studies. Yet the dispersal mechanisms that provide a crucial link between local populations and large-scale biogeographic patterns are not well documented. We experimentally demonstrate the dispersal of prop- agules, which include both sexually and asexually produced young (perhaps only the proloculus), though the sexually produced young

Elisabeth Alve; Susan T. Goldstein

2003-01-01

353

Structural responses of benthic macroinvertebrate communities from different stream orders to zinc  

SciTech Connect

It is well established that benthic invertebrate community structure and function shift in a predictable fashion along longitudinal stream gradients as a result of variation in environmental conditions. The authors research is concerned with experimentally testing whether this shift in community structure influences the response of benthic macroinvertebrates to heavy metals. Using artificial streams, they compared effects of Zn on natural assemblages of benthic macroinvertebrates communities collected from Little Beaver Creek (LBC; a third-order stream) and the Big South Fork of the Cache la Poudre, Colorado, catchment. Organisms collected from LBC and SFP were exposed to 0 or 130 [mu]g/L Zn in indoor experimental streams for 7 d. In general, similar taxa were found at both sites, but densities were generally higher at SFP than at LBC. They observed significant effects at the community and population level as a result of Zn, stream order, and the interaction between Zn and stream order. Specifically, mayflies from both sides were sensitive to Zn, but the magnitude of the response varied between sites. The results indicate that benthic macroinvertebrate communities from different stream order may vary in sensitivity to Zn.

Kiffney, P.M.; Clements, W.H. (Colorado State Univ., Fort Collins, CO (United States). Dept. of Fishery and Wildlife Biology)

1994-03-01

354

COMPARATIVE PERFORMANCE OF SIX DIFFERENT BENTHIC MACROINVERTEBRATE SAMPLING METHODS FOR RIVERINE ECOSYSTEMS  

EPA Science Inventory

At each of 60 sites, we collected benthic macroinvertebrates using six different protocols (including the EMAP methods for non-wadeable rivers) and physical habitat data using the USEPA-EMAP-SW protocols for non-wadeable rivers. We used PCA with physical habitat data and DCA wit...

355

Relative prawn production and benthic macroinvertebrate densities in unfed, organically fertilized, and fed pond systems  

Microsoft Academic Search

Relative prawn production rates in unfed, organically fertilized, and fed pond systems were evaluated. Populations of benthic macroinvertebrates that potentially serve as forage organisms in these systems were also evaluated and compared with ponds without prawns to evaluate forage preferences. Juvenile prawns (x? = 0.36 ± 0.02 g) were stocked into nine 0.04 ha ponds at a density of 39

James H Tidwell; Shawn D Coyle; Carl D Webster; John D Sedlacek; Paul A Weston; Wanda L Knight; Sankie J Hill; Louis R D'Abramo; William H Daniels; Marty J Fuller

1997-01-01

356

Effects of heavy metals on benthic macroinvertebrate communities in New Zealand streams  

SciTech Connect

The authors performed chemical analyses of heavy metals in water and periphyton, toxicity tests with Daphnia magna and an indigenous mayfly (Deleatidium sp.), and field surveys of benthic macroinvertebrates to estimate the degree of metal pollution in three catchments in the Coromandel Peninsula of New Zealand. Good agreement was found between toxicity tests and measures of benthic community structure, particularly at stations with the highest metal levels. Responses of benthic communities at stations with low or moderate levels of metal contamination were variable and were probably confounded by factors other than heavy metals. Effects of heavy metals on benthic communities in New Zealand streams were similar to those reported for metal-polluted streams in North America and Europe, suggesting that responses to metal contamination are predictable. Abundance and species richness of mayflies, number of taxa in the orders Ephemeroptera, Plecoptera, and Trichoptera, and total taxonomic richness were the best indicators of heavy metals in New Zealand streams. In contrast, the quantitative macroinvertebrate community index (QMCI), a biotic index proposed for assessing effects of organic enrichment in New Zealand streams, could not distinguish between reference and metal-polluted streams. The poor performance of the QMCI was primarily due to incorrect tolerance scores for some taxa to heavy metals. Because of concerns regarding the subjective assignment of tolerance values to species, the authors recommend that tolerance values for dominant species in New Zealand streams should be verified experimentally in stream microcosms.

Hickey, C.W. [National Inst. of Water and Atmospheric Research, Hamilton (New Zealand); Clements, W.H. [Colorado State Univ., Fort Collins, CO (United States). Dept. of Fishery and Wildlife Biology

1998-11-01

357

Benthic community response (primarily Chironomidae) to nutrient enrichment and alkalinization in shallow, soft water humic lakes  

Microsoft Academic Search

A comparison of the benthic fauna found in two shallow lakes in the New Jersey Pinelands (USA) illustrated the impact of elevated pH and nutrients caused by residential and agricultural disturbance on a naturally acidic, poorly buffered aquatic environment. Detailed community analysis suggested that change in community composition was a better indicator of response to disturbance than biological diversity indices.

John E. Dougherty; Mark D. Morgan

1991-01-01

358

Research of the Benthic Fauna of the Southern Adriatic Italian Coast.  

National Technical Information Service (NTIS)

A research on the benthic fauna of Puglie's littoral in the South Adriatic Sea, the first in this area, has been initiated and is carried out through diving and dredging. Various stations and different biotopes have been investigated along about 400 km of...

M. Sara

1966-01-01

359

Early Miocene benthic foraminifera and biostratigraphy of the Qom Formation, Deh Namak, Central Iran  

Microsoft Academic Search

A total of 165 samples were collected from the Qom Formation investigated in a stratigraphic section north of Deh Namak, in Central Iran. From these, 35 genera and 47 species of benthic foraminifera were identified. The age of the studied section is Early Miocene (Aquitanian to Early Burdigalian) based on the occurrence of Borelis melo curdica, Meandropsina anahensis, Meandropsina iranica,

Jahanbakhsh Daneshian; Leila Ramezani Dana

2007-01-01

360

Half-against-half structure in classification of benthic macroinvertebrate images.  

PubMed

Benthic macroinvertebrates play a key role when water quality assessments are made. Benthic macroinvertebrates are difficult to identify and their identification need special expertise. Furthermore, manual identification is slow and expensive process. This paper concerns benthic macroinverte-brate classification when Half-Against-Half (HAH) structure was applied to Support Vector Machine (SVM), Linear Discriminant Analysis (LDA), Quadratic Discriminant Analysis (QDA) and Minimum Mahalanobis Distance Classifier (MMDC) classifiers. Especially, LDA, QDA and MMDC classifiers were for first time applied with HAH structure to benthic macroinvertebrate classification. We performed thorough experiments altogether with ten methods. In the case of HAH-SVM we managed to improve classification results from the earlier research by using a different approach to class division problem. We obtained 96.1% classification accuracy with Radial Basis Function (RBF) kernel. Moreover, new variants of LDA, QDA and MMDC classification methods achieved 89.5% and 91.6% classification accuracies which can be considered as a good result in such a difficult classification task. PMID:24110520

Joutsijoki, Henry

2013-01-01

361

Residual concentrations of micropollutants in benthic mussels in the coastal areas of Bohai Sea, North China  

Microsoft Academic Search

Studies of heavy metals and organic pollutants in different benthic mussel species from Bohai Sea show that concentrations of Cd in mussels commonly exceed national biological quality standards. In addition, a site located in Laizhou Bay exhibits higher average concentrations of As, Hg and Pb with respect to the other sites. Residual levels of petroleum hydrocarbons at several sites in

WenXin Liu; JiangLin Chen; XiuMei Lin; YongSheng Fan; Shu Tao

2007-01-01

362

DEVELOPING AND APPLYING A BENTHIC INDEX OF ESTUARINE CONDITION FOR THE VIRGINIAN BIOGEOGRAPHIC PROVINCE  

EPA Science Inventory

A benthic index of estuarine condition was constructed for the Virginian Biogeographic Province (from Cape Cod, Massachusetts, to the mouth of Chesapeake Bay, Virginia) with data collected during summers of 1990 through 1993 by the US EPA's Environmental Monitoring and Assessment...

363

Subtidal benthic macroinfaunal assemblages in tropical estuaries: generality amongst highly variable gradients.  

PubMed

South American estuaries are frequently not included in the search for general ecological models and studies dealing with biological assemblages in estuaries frequently do not sample the entire salinity gradient. We sampled three tropical estuaries, two times each, on ten stations distributed along each system. Six replicates were collected in each station for the benthic macroinfauna and sediment samples for grain size and inorganic contaminant analyses. There were finer sediments at the lower than at the upper estuarine portions. There was a decrease in the diversity, at family level, from marine to freshwater and the differences on the structure of the benthic assemblages were mostly spatial. In spite of the many different characteristics of the three estuaries (e.g. catchment size, pollution levels, proximity with the inner continental shelf) several consistent patterns of benthic macrofauna distribution along these systems were still observed. It suggested a general empirical model regarding the distribution of different benthic invertebrates along tropical salinity gradients which can be tested in different estuaries around the world. PMID:22975382

Barros, Francisco; de Carvalho, Gilson Correia; Costa, Yuri; Hatje, Vanessa

2012-10-01

364

Effects of Benthic Barriers on Aquatic Habitat Conditions and Macroinvertebrate Communities  

Microsoft Academic Search

Physical and chemical conditions of sediments and benthic community composition were evaluated under syn- thetic fabric barriers, used to control aquatic macrophytes in confined areas. Macroinvertebrate density declined by 69% within 4 weeks at Eau Galle Reservoir, WI. Within a few weeks of placement at ponds near Dallas, TX, invertebrate densities declined by more than 90%. At Eau Galle Reservoir,

THOMAS A. USSERY; H. L. EAKIN; B. S. PAYNE; A. C. MILLER; J. W. BARKO

1997-01-01

365

Differential recruitment of benthic communities on neighboring artificial and natural reefs  

Microsoft Academic Search

Shedding light on the ability of benthic artificial reef (AR) communities to resemble those of a natural reef (NR) is of great importance if we are to harness ARs as tools for rehabilitation and restoration of degraded marine habitats. Studying recruitment processes to experimental settlement plates attached to ARs and NRs reveal the factors that shape community structure at the

S. Perkol-Finkel; Y. Benayahu

2007-01-01

366

Carbon and nitrogen stable isotopes in coastal benthic populations under multiple organic enrichment sources  

Microsoft Academic Search

In a dispersive coastal area under multiple organic enrichment sources, stable isotopes were used to trace organic sources of carbon and nitrogen in sediments and benthic macrofauna. The Bivalve Abra alba and the Polychaetes Nephtys sp. and Pectinaria (Lagis) koreni were reliable indicators of the input of terrestrial-derived organic matter into this coastal area, either originated in outfall sewage discharges

Leandro Sampaio; Ana Maria Rodrigues; Victor Quintino

2010-01-01

367

Sediment resuspension effects on the benthic microbial loop in experimental microcosms.  

PubMed

Sediment resuspension induced by anthropogenic disturbance is becoming a major threat of marine coastal ecosystems worldwide. The effects of sediment resuspension on the pelagic domain and on macro- and meiobenthos are well documented in the literature, whereas the effects on the benthic microbial components are nearly neglected. We have investigated the effects of sediment resuspension at two different disturbance levels on benthic bacterial abundance, biomass, and activities and on heterotrophic nanobenthos abundance in experimental microcosms. The results of our experiments pointed out that, independently from the amount of involved energy, sediment resuspension determined a general decrease of all benthic microbial components. The main effects consisted of a decreased abundance of the metabolically active bacterial fraction and of heterotrophic nanobenthos abundance. However, the amount of energy involved in sediment resuspension had differential effects on the structure and functioning of the benthic microbial loop, but only in the short term (i.e., within 36 h). Sediment resuspension had a stimulatory effect on activities of surviving bacterial cells, which, in turn, resulted in increased sediment organic C turnover rates. We hypothesize that such an effect, enhancing nutrient availability, might have relevant consequences on the trophic state of coastal marine ecosystem. PMID:16341638

Pusceddu, Antonio; Fiordelmondo, Carla; Danovaro, Roberto

2005-11-01

368

Benthic-pelagic coupling in the population dynamics of the harmful cyanobacterium Microcystis  

Microsoft Academic Search

SUMMARY 1. In eutrophic lakes, large amounts of the cyanobacterium Microcystis may overwinter in the sediment and re-inoculate the water column in spring. 2. We monitored changes in pelagic and benthic populations of Microcystis in Lake Volkerak, The Netherlands. In addition, sedimentation rates and the rate of recruitment from the sediment were measured using traps. These data were used to

JOLANDA M. H. V ERSPAGEN; KLAUS D. J OHNK; W. I BELINGS; LUUC R. M UR; J EF H UISMAN

369

Impacts of ocean acidification on large benthic foraminifers: Results from laboratory experiments  

Microsoft Academic Search

Ocean acidification has become recognized recently to be a major threat to calcifying organisms. Previous studies have reported that calcification rates of calcareous marine organisms (e.g., corals, foraminifers, coccolithophores, pteropods, mussels, and oysters) change in response to lowering pH levels even in waters oversaturated with respect to calcium carbonate. However, the impact of ocean acidification on large benthic foraminifers, which

Azumi Kuroyanagi; Hodaka Kawahata; Atsushi Suzuki; Kazuhiko Fujita; Takahiro Irie

2009-01-01

370

Benthic Marine Cypridinoidea from Bermuda (Ostracoda). Smithsonian Contributions to Zoology, Number 331.  

National Technical Information Service (NTIS)

Four species in four genera of benthic Cypridinoidea are reported from Bermuda. Two new species are described and illustrated, and a supplementary description is given of a previously described species. One of the species is described but left in open nom...

L. S. Kornicker

1981-01-01

371

The Paleocene-Eocene Benthic Foraminiferal Extinction and Stable Isotope Anomalies  

Microsoft Academic Search

In the late Paleocene to early Eocene, deep sea benthic foraminifera suffered their onlyglobal extinction of the last 75 million years and diversity decreased worldwide by 30-50% in a few thousand years. At Maud Rise (Weddell Sea, Antarctica; Sites 689 and 690, palaeodepths 1100 m and 1900 m) and Walvis Ridge (Southeastern Atlantic, Sites 525 and 527, palaeodepths 1600 m

Ellen Thomas; Nicholas J. Shackleton

1996-01-01

372

Assessing estuarine benthic quality conditions in Chesapeake Bay: A comparison of three indices  

Microsoft Academic Search

Legislation in US and Europe has been adopted to determine the ecological integrity of estuarine and coastal waters, including, as one of the most relevant elements, the benthic macroinvertebrate communities. It has been recommended that greater emphasis should be placed on evaluating the suitability of existing indices prior to developing new ones. This study compares two widely used measures of

A. Borja; D. M. Dauer; R. Díaz; R. J. Llansó; I. Muxika; J. G. Rodríguez; L. Schaffner

2008-01-01

373

Recent benthic foraminiferal associations and ecology of the Scotia Sea and Argentine Basin  

Microsoft Academic Search

We investigated 88 surface sediment samples taken with a multiple corer from the southwestern South Atlantic Ocean for their live (Rose Bengal stained) and dead benthic foraminiferal content. Using Q-Mode Principal Component Analysis six live and six dead associations are differentiated. Live and dead association distributions correspond fairly well; differences are mainly caused by downslope transport and selective test destruction.

J. Harloff; A. Mackensen

1997-01-01

374

Application of Multiple Index Development Approaches to Benthic Invertebrate Data from the Virginian Biogeographic Province, USA  

EPA Science Inventory

Previous work had indicated that the Virginian Province Index did not perform well in a smaller estuarine complex. While it was hoped that the existing Chesapeake Bay Benthic Index of Biotic Integrity, with its greater number of metrics and habitat separation would be more adapt...

375

Photosynthetic characteristics of benthic microalgae and seagrass in Lake Illawarra, Australia  

Microsoft Academic Search

Lake Illawarra, is a typical shallow intertidal coastal barrier lagoon in New South Wales, Australia. This paper reports the first examination of photosynthetic characteristics of benthic microalgae and seagrass in this lake by measuring the oxygen exchange procedure (flux) using sediment-core incubations in the laboratory.

Wenchuan Qu; Chenwei Su; R. J. West; R. J. Morrison

2004-01-01

376

Spectral reflectance of carbonate sediments and application to remote sensing classification of benthic habitats  

Microsoft Academic Search

Remote sensing is a valuable tool in marine research that has advanced to the point that images from shallow waters can be used to identify different seafloor types and create maps of benthic habitats. A major goal of this dissertation is to examine differences in spectral reflectance and create new methods of analyzing shallow water remote sensing data to identify

Eric Michael Louchard

2003-01-01

377

Benthic Bacterial Production and Protozoan Predation in a Silty Freshwater Environment  

Microsoft Academic Search

The interrelation of heterotrophic bacteria with bacterivorous protists has been widely studied in pelagic environments, but data on benthic habitats, especially in freshwater systems, are still scarce. We present a seasonal study focusing on bacterivory by heterotrophic nanoflagellates (HNF) and ciliates in the silty sediment of a temperate macrophyte-dominated oxbow lake. From January 2001 to February 2002 we monitored the

C. Wieltschnig; U. R. Fischer; A. K. T. Kirschner; B. Velimirov

2003-01-01

378

A PROBABILISTIC ASSESSMENT OF BENTHIC CONDITION OF CALIFORNIA ESTUARIES: RESULTS FROM THE NATIONAL COASTAL ASSESSMENT 1999  

EPA Science Inventory

As part of the National Coastal Assessment, the Environmental Monitoring and Assessment Program of EPA is conducting a three year evaluation of benthic habitat condition of California estuaries. In 1999, probabilistic sampling for a variety of biotic and abiotic condition indica...

379

BIOGEOGRAPHY OF BENTHIC MACROINVERTEBRATES IN ESTUARIES ALONG THE GULF OF MEXICO AND WESTERN ATLANTIC COASTS  

EPA Science Inventory

The community composition of benthic macroinvertebrates from 870 estuarine sites was examimed in order to either confirm or challenge established boundaries of biogeographical provinces along the Gulf of Mexico and western Atlantic coasts of the United States. The objective was t...

380

Spatial distribution of benthic microalgae on coral reefs determined by remote sensing  

NASA Astrophysics Data System (ADS)

Understanding the ecological role of benthic microalgae, a highly productive component of coral reef ecosystems, requires information on their spatial distribution. The spatial extent of benthic microalgae on Heron Reef (southern Great Barrier Reef, Australia) was mapped using data from the Landsat 5 Thematic Mapper sensor, integrated with field measurements of sediment chlorophyll concentration and reflectance. Field-measured sediment chlorophyll concentrations, ranging from 23-1,153 mg chl a m-2, were classified into low, medium, and high concentration classes (1-170, 171-290, and >291 mg chl a m-2) using a K-means clustering algorithm. The mapping process assumed that areas in the Thematic Mapper image exhibiting similar reflectance levels in red and blue bands would correspond to areas of similar chlorophyll a levels. Regions of homogenous reflectance values corresponding to low, medium, and high chlorophyll levels were identified over the reef sediment zone by applying a standard image classification algorithm to the Thematic Mapper image. The resulting distribution map revealed large-scale (>1 km2) patterns in chlorophyll a levels throughout the sediment zone of Heron Reef. Reef-wide estimates of chlorophyll a distribution indicate that benthic microalgae may constitute up to 20% of the total benthic chlorophyll a at Heron Reef, and thus contribute significantly to total primary productivity on the reef.

Roelfsema, C.; Phinn, S.; Dennison, W.

2002-09-01

381

BENTHIC MACROALGAE, DISSOLVED SULFIDES, AND AMPHIPODS IN SURFICIAL SEDIMENTS OF YAQUINA BAY ESTUARY, OREGON, USA  

EPA Science Inventory

Surveys of benthic green macroalgae at two sites in Yaquina Bay Estuary, Oregon, in 1999 showed that percent cover and biomass values in June were much higher at one site, Idaho Point, than at the other site, Coquille Point. The frequency of detectable hydrogen sulfide odor late...

382

Organic matter release by coral reef associated benthic algae in the Northern Red Sea  

Microsoft Academic Search

Recent research indicates that coral reef associated benthic algae may control important metabolic processes in reef ecosystems via organic matter release. Yet little information is available about quantity and chemical composition of these algae-derived exudates. Therefore first comprehensive studies on algal organic matter release were conducted at a fringing reef ecosystem in the Northern Red Sea. Dissolved organic carbon (DOC),

Andreas F. Haas; Malik S. Naumann; Ulrich Struck; Christoph Mayr; Mohammad el-Zibdah; Christian Wild

2010-01-01

383

Benthic diatom composition in isolated forested wetlands subject to drying: implications for monitoring and assessment  

EPA Science Inventory

The development of bioindicators for wetlands, especially ephemerally hydrated depressional and isolated wetlands, can be problematic because of seasonal hydrology and target organism biology. To determine if benthic diatoms could be used as a year-round biological indicator of w...

384

Benthic diatom composition in wet and dry isolated forested wetlands: implications for monitoring and assessment  

EPA Science Inventory

The development of bioindicators for wetlands, especially ephemerally hydrated depressional and isolated wetlands, can be problematic because of seasonal changes in hydrology and target organism biology. To determine if benthic diatoms could be used as a year-round biological ind...

385

The Influence of Coral Reef Benthic Condition on Associated Fish Assemblages  

PubMed Central

Accumulative disturbances can erode a coral reef’s resilience, often leading to replacement of scleractinian corals by macroalgae or other non-coral organisms. These degraded reef systems have been mostly described based on changes in the composition of the reef benthos, and there is little understanding of how such changes are influenced by, and in turn influence, other components of the reef ecosystem. This study investigated the spatial variation in benthic communities on fringing reefs around the inner Seychelles islands. Specifically, relationships between benthic composition and the underlying substrata, as well as the associated fish assemblages were assessed. High variability in benthic composition was found among reefs, with a gradient from high coral cover (up to 58%) and high structural complexity to high macroalgae cover (up to 95%) and low structural complexity at the extremes. This gradient was associated with declining species richness of fishes, reduced diversity of fish functional groups, and lower abundance of corallivorous fishes. There were no reciprocal increases in herbivorous fish abundances, and relationships with other fish functional groups and total fish abundance were weak. Reefs grouping at the extremes of complex coral habitats or low-complexity macroalgal habitats displayed markedly different fish communities, with only two species of benthic invertebrate feeding fishes in greater abundance in the macroalgal habitat. These results have negative implications for the continuation of many coral reef ecosystem processes and services if more reefs shift to extreme degraded conditions dominated by macroalgae.

Chong-Seng, Karen M.; Mannering, Thomas D.; Pratchett, Morgan S.; Bellwood, David R.; Graham, Nicholas A. J.

2012-01-01

386

Siphon size and burying depth in deposit- and suspension-feeding benthic bivalves  

Microsoft Academic Search

This paper analyses the significance of siphon investment in the life strategy of benthic bivalves. It describes the relationships between siphon weight, burying depth and shell size in Mya arenaria, Cerastoderma edule. Scrobicularia plana and Macoma balthica. All data were collected on an intertidal flat in the Dutch Wadden Sea during seven successive winter and summer periods. The four species

L. Zwarts; J. Wanink

1989-01-01

387

Influence of stability and fragmentation of a worm-reef on benthic macrofauna  

NASA Astrophysics Data System (ADS)

In coastal areas, reef-builder worms often are bio-engineers by structuring their physical and biological environment. Many studies showed that this engineering role is determined by the densities of the engineer species itself, the highest densities approximately corresponding to the most stable areas from a sedimentological point of view, and hosting the richest and the most diverse benthic fauna. Here, we tested the potential influence of the spatio-temporal dynamics and the spatial fragmentation of one of the largest European intertidal reefs generated by the marine worm Lanice conchilega (Pallas, 1766) (Annelida, Polychaeta) on the associated benthic macrofauna. We demonstrated that the worm densities do have a significant positive role on the abundance, biomass, species richness and species diversity of the benthic macrofauna and that the reef stability also significantly influences the biomass and species diversity. Moreover, the reef fragmentation has significant negative effects on the abundance, biomass and species richness. In addition to L. conchilega densities, the stability and the spatial fragmentation of the reef also significantly structure the associated benthic assemblages. This study demonstrates the interest of "benthoscape ecology" in understanding the role played by marine engineer species from a spatial point of view.

Godet, Laurent; Fournier, Jérôme; Jaffré, Mikaël; Desroy, Nicolas

2011-05-01

388

Cd in planktonic and benthic foraminiferal shells determined by thermal ionization mass spectrometry  

SciTech Connect

A highly sensitive method for Cd determination in foraminiferal shells by isotope-dilution TIMS has been developed and applied to (1) a more detailed reconstruction of seawater Cd depth profiles for the North Atlantic in the Holocene and at the Last Glacial Maximum (LGM); (2) the analysis of Cd/Ca in individual benthic foraminifera shells; and (3) determination of Cd/Ca in Holocene and glacial planktonic foraminifera. Although Ca has a high first ionization potential, through chemical separation of Cd from the Ca and optimization of the loading technique, it is possible to analyze routine sized samples (10 benthics) with a reproducibility in Cd/Ca of {+-}0.0025 {micro}mol/mol between replicate picks from a single sample. The blank of the method is 1.1 pg, permitting analysis of individual benthics and of planktonic foraminifera. The seawater Cd reconstruction for the LGM is consistent with previous work, but also suggests that depths >2,500 m were ventilated by a northern source of nutrient depleted deep water on the western side of the Mid Atlantic Ridge. Individual benthic Cd/Ca ratios show interspecimen variability which is averaged in routine analysis of multiple specimens. Planktonic Cd/Ca from N. Atlantic cores shows interspecific differences between Globigerina bulloides and Neogloboquadrina pachyderma and Holocene-LGM contrasts which offers potential for use of planktonic Cd/Ca as a palaeochemical tracer.

Rickaby, R.E.M.; Greaves, M.J.; Elderfield, H.

2000-04-01

389

Trace Element Contamination in Benthic Macroinvertebrates from a Small Stream Near a Uranium Mill Tailings Site  

Microsoft Academic Search

Direct measurement of the accumulation of non-radioactive traceelements in aquatic biota near uranium mining or processing sites has been relatively rare, with greater focus on the radiological activity in the adjacent soils and groundwater. To evaluate the potential ecological concern associated with trace elements at a former uranium mill site in southeasternUtah, benthic macroinvertebrates were collected and analyzed for 17

M. J. Peterson; J. G. Smith; G. R. Southworth; M. G. Ryon; G. K. Eddlemon

2002-01-01

390

Using an Acoustic Ground Discrimination System to map coral reef benthic classes  

Microsoft Academic Search

An Acoustic Ground Discrimination System (AGDS) can extract information on the nature of the seabed. Compared to satellite or airborne sensors, AGDS is rarely used in tropical environments but is easy to operate and produces a modest amount of digital data. This study aimed to assess acoustic surveys of coral reef benthic classes using a RoxAnn @ AGDS in the

W. H. White; A. R. Harborne; I. S. Sotheran; R. Walton; R. L. Foster-Smith

2003-01-01

391

Broad-scale factors influencing the biodiversity of coastal benthic communities of the Ross Sea  

NASA Astrophysics Data System (ADS)

Early ecological research in McMurdo Sound revealed local spatial gradients in community structure associated with variations in anchor ice disturbance, fast ice and snow cover, and the effects of predators. Research contrasting the east and west sides of McMurdo Sound has shown major differences in benthic communities, which have been attributed to oceanographic influences on the advection of water-column productivity and the frequency of fast ice break-out. Despite these regional and local differences, coastal benthic communities in McMurdo Sound show a high level of stability, and contain a variety of large and potentially very long-lived species. In Terra Nova Bay, about half way along the Victoria Land Coast of the western Ross Sea, the coastal benthic communities provide some insightful contrasts with those in McMurdo Sound. For example, the abundance and depth distribution of dominant species such as Sterechinus neumayeri and Adamussium colbecki are markedly different from McMurdo Sound. In both locations communities dominated by large sponges are most prolific in regions that are free from iceberg disturbance of the seabed. A recent assessment of northern Victoria Land coastal benthic communities, in conjunction with multibeam imagery of the seafloor, further highlights the importance of iceberg disturbance in structuring Antarctic benthic communities. A comparative synthesis of these coastal ecological studies enables us to generate hypotheses concerning the relative importance of different environmental drivers in structuring benthic communities. Overlain on the regular latitudinal shifts in physical factors such as light regime, are regional fluctuations that are controlled by atmospheric and oceanographic circulation patterns and coastal topography/bathymetry. Change in diversity along the western coast of the Ross Sea is predicted to be influenced by three main factors (1) ice disturbance (e.g., via anchor ice and advection of supercooled water or icebergs), (2) photosynthetically available radiation (affected by ice and snow cover and water clarity), (3) the locations of polynyas and advection of planktonic production and larvae. Interactions between these factors are expected to result in non-linear changes along the latitudinal gradient. While predictions generated from these hypotheses remain to be rigorously tested, they provide indications of how benthic communities may respond to changes in production, disturbance and the stability of coastal sea ice.

Thrush, Simon; Dayton, Paul; Cattaneo-Vietti, Riccardo; Chiantore, Mariachiara; Cummings, Vonda; Andrew, Neil; Hawes, Ian; Kim, Stacy; Kvitek, Rikk; Schwarz, Anne-Maree

2006-04-01

392

Comparison of Adjective vs. Benthic Sources of Nutrients to a Former Salt Pond under Restoration  

NASA Astrophysics Data System (ADS)

With the implementation of the South Bay Restoration Program in 2008, water quality in the Alviso Salt Ponds, California, has been monitored to document the effects of changing hydrologic connections among the ponds and the adjacent pond, slough and estuary. In 2010 and 2012, pore-water profilers (U.S. Patent 8,051,727 B1) were deployed in Pond A3W, a former salt pond just north of Moffett Federal Airfield that mixes hydrologically through culverts and weirs with Guadalupe Slough and neighboring ponds, to assess the magnitude of diffusive benthic flux, generated primarily by remobilization of surface-reactive solutes in bed sediment accumulated over annual to decadal time scales. The study, focusing on macronutrient sources that may stimulate harmful algal blooms, revealed that orthophosphate, ammonia, and silica benthic flux were consistently positive (out of the sediment) in both 2010 and 2012, while nitrate and nitrite fluxes were negligible. Because tidal height can affect the size and direction of flow, a diurnal study of nutrient advective flux into and out of the pond was measured during neap and spring tides. These advective fluxes (kg/yr) were compared to benthic flux estimates for the pond extrapolated over the 2.27 (km2) pond surface. Benthic flux of inorganic nitrogen species, averaged over all sites and dates, was about 80,000 + 48,000 kilograms per year (kg/yr), well above the adjective flux range of -50 to 1,500 kg/yr. By contrast, the average benthic flux of orthophosphate was about 12,000 + 4,400 kg/yr, well below the advective flux range of 21,500 to 30,000 kg/yr. Benthic flux estimates determined by porewater gradients do not include enhancement processes such as bioturbation, bioirrigation, wind resuspension, and potential groundwater inflows. However, they provide a conservative measure and can be an effective management screening tool. These results indicate that benthic transport may be an important source of biologically reactive solutes for both nutrients and toxicants, an important consideration during restoration since there are trophic transfer implications.

Topping, B.; Kuwabara, J. S.; Garrett, K.; Takekawa, J.; Piotter, S.; Parchaso, F.

2013-12-01

393

Importance of benthic production to fish populations in Lake Mead prior to the establishment of quagga mussels  

USGS Publications Warehouse

Limnologists recently have developed an interest in quantifying benthic resource contributions to higher-level consumers. Much of this research focuses on natural lakes with very little research in reservoirs. In this study, we provide a contemporary snapshot of the food web structure of Lake Mead to evaluate the contribution of benthic resources to fish consumers. In addition, we document the available food to fishes on soft sediments and changes to the invertebrate community over 2 time periods. Benthic invertebrate food availability for fishes is greater in Las Vegas Bay than Overton Arm. Las Vegas Bay is dominated by oligochaetes, whose biomass increased with depth, while Overton Arm is dominated by chironomids, whose biomass did not change with depth. Diet and isotopic measurements indicate the fish community largely relies on benthic resources regardless of basin (Las Vegas Bay >80%; Overton Arm >92%); however, the threadfin shad likely contribute more to largemouth and striped bass production in Overton Arm versus Las Vegas Bay. A 2-time period analysis, pre and post quagga mussel establishment and during lake level declines, suggests there is no change in the density of benthic invertebrates in Boulder Basin, but there were greater abundances of select taxa in this basin by season and depth than in other basins. Given the potential of alterations as a result of the expansion of quagga mussel and the reliance of the fishery on benthic resources, future investigation of basin specific, benthic processes is recommended.

Umek, John; Chandra, Sudeep; Rosen, Michael; Wittmann, Marion; Sullivan, Joe; Orsak, Erik

2010-01-01

394

Benthic habitat mapping: Concerns using a combined approach (acoustic, sediment and biological data)  

NASA Astrophysics Data System (ADS)

Near-shore benthic biotopes, in the 2-30 m depth range, were analyzed and mapped using a combination of biological, sedimentary and acoustic data to interrogate the utility of these methods. The surveyed area covered approximately 270 km 2, along 80 km of the Southeast coast of Portugal. The acoustic data were acquired with a single beam ground discrimination system (QTC VIEW, Series V), connected to a dual frequency echo sounder (50 and 200 kHz). Sediment grain size and macrofaunal community data were obtained by grab sampling at 88 sites. The sedimentary and the biological data were subjected to classification and ordination analysis and the acoustic data obtained with the two frequencies were analyzed individually with the QTC IMPACT (v3.4) software and classified into acoustic classes. The affinity groups obtained with the three datasets were mapped using a Geographic Information System. The study area showed an inshore-offshore pattern with sands ranging from very fine to very coarse, revealing a sediment distribution in the near-shore shelf comprised by two main areas; a very fine/fine sand area up to 7-10 m depth and a very coarse/coarse sand area offshore. In turn, the biological data also showed an inshore-offshore pattern, identifying two main biological assemblages: fine/very fine sand and coarse/very coarse sand communities. Furthermore, the biological pattern clearly reflected the hydrodynamic conditions of the area, from highly hydrodynamic shallow depth to the calmer deeper areas. Accordingly, species richness and densities were lower at shallow areas than at deeper depth. The acoustic data identified the prevailing biosedimentary gradients along the inshore-offshore direction. Overall, the results obtained here showed that the acoustic system could identify two main areas based on sediment grain size, which closely related to the two main biological communities (groups A and B). This study indicates the importance of combining several layers of information in order to increase the spatial resolution of the main biotope distribution (validating the acoustic data) and detail their sub-divisions (ground-truth sampling). Furthermore, we show that designing ground-truth samples on the basis of the acoustic diversity data allows the biological data to "speak" for itself. In general, acoustic techniques are used as a means to optimize ground-truth sampling. This will only be valid if acoustics can capture all the essence of biotope heterogeneity. If this is not the case, special attention should be given when using broad scale methods (acoustic remote sensing) devoted to biotope mapping.

Freitas, Rosa; Ricardo, Fernando; Pereira, Fábio; Sampaio, Leandro; Carvalho, Susana; Gaspar, Miguel; Quintino, Victor; Rodrigues, Ana Maria

2011-05-01

395

Relationship between the pore density in benthic foraminifera and bottom-water oxygen content  

NASA Astrophysics Data System (ADS)

Reliable estimates of bottom-water oxygen contents are crucial to understand the formation of past oxygen-depleted environments. Here, we investigate the relationship between pore density in calcareous benthic foraminiferal (BF) tests and measured oxygen concentrations of the surrounding bottom-waters (BW-O2) in living (Rose Bengal stained) specimens of the shallow-infaunal species Bolivina pacifica, and the three deep-infaunal species Fursenkoina mexicana, Globobulimina turgida, and Chilostomella oolina. Used samples span a wide oxygen-gradient across oxygen minimum zones (OMZ) off Namibia and Pakistan. Bolivina pacifica, F. mexicana and G. turgida display a significant negative exponential correlation between the pore density and BW-O2, indicating a morphological response of the foraminifers to decreasing oxygenation. Supporting previous results, we suggest that an increasing number of pores improves the ability of oxygen uptake in low-oxygen environments. This morphological response can be used to establish an independent proxy for BW-O2. The inter-specific comparison of the dependency of pore density and BW-O2 reveals a steeper gradient for B. pacifica than for F. mexicana, and G. turgida. We hypothesize that the inter-specific pore density-BW-O2-relationship may reflect their species-specific microhabitat preferences. The shallow-infaunal species B. pacifica is probably stronger affected by oxygen depletions than the two deep-infaunal species F. mexicana, and G. turgida. Our results for the deep-infaunal species C. oolina show no significant relationship between pore density and BW-O2. This suggests that C. oolina has another life-strategy to survive sustained low-oxic conditions than increasing its pore density. Overall, we propose that the pore density of individual BF species provides a valuable independent proxy to reconstruct ancient bottom-water oxygenation. To test the application of this proxy in fossil assemblages, we used the organic-carbon rich sapropel layer S1 in two cores from the North Agean Sea to illustrate the decrease in BW-O2 before and during the sapropel formation as well as the BW-O2 increase afterwards.

Kuhnt, T.; Friedrich, O.; Schmiedl, G.; Milker, Y.; Mackensen, A.; Schiebel, R.

2012-04-01

396

Benthic Primary Production Budget of a Caribbean Reef Lagoon (Puerto Morelos, Mexico)  

PubMed Central

High photosynthetic benthic primary production (P) represents a key ecosystem service provided by tropical coral reef systems. However, benthic P budgets of specific ecosystem compartments such as macrophyte-dominated reef lagoons are still scarce. To address this, we quantified individual and lagoon-wide net (Pn) and gross (Pg) primary production by all dominant functional groups of benthic primary producers in a typical macrophyte-dominated Caribbean reef lagoon near Puerto Morelos (Mexico) via measurement of O2 fluxes in incubation experiments. The photosynthetically active 3D lagoon surface area was quantified using conversion factors to allow extrapolation to lagoon-wide P budgets. Findings revealed that lagoon 2D benthic cover was primarily composed of sand-associated microphytobenthos (40%), seagrasses (29%) and macroalgae (27%), while seagrasses dominated the lagoon 3D surface area (84%). Individual Pg was highest for macroalgae and scleractinian corals (87 and 86 mmol O2 m?2 specimen area d?1, respectively), however seagrasses contributed highest (59%) to the lagoon-wide Pg. Macroalgae exhibited highest individual Pn rates, but seagrasses generated the largest fraction (51%) of lagoon-wide Pn. Individual R was highest for scleractinian corals and macroalgae, whereas seagrasses again provided the major lagoon-wide share (68%). These findings characterise the investigated lagoon as a net autotrophic coral reef ecosystem compartment revealing similar P compared to other macrophyte-dominated coastal environments such as seagrass meadows and macroalgae beds. Further, high lagoon-wide P (Pg: 488 and Pn: 181 mmol O2 m?2 lagoon area d?1) and overall Pg:R (1.6) indicate substantial benthic excess production within the Puerto Morelos reef lagoon and suggest the export of newly synthesised organic matter to surrounding ecosystems.

Naumann, Malik S.; Jantzen, Carin; Haas, Andreas F.; Iglesias-Prieto, Roberto; Wild, Christian

2013-01-01

397

Oxygenation episodes on the continental shelf of central Peru: Remote forcing and benthic ecosystem response  

NASA Astrophysics Data System (ADS)

The interplay between the oxygen minimum zone and remotely-forced oxygenation episodes determines the fate of the benthic subsystem off the Central Peruvian coast. We analyzed a 12 year monthly time-series of oceanographic and benthic parameters at 94 m depth off Callao, Central Peru (12°S), to analyze: (i) near-bottom oxygen level on the continental shelf in relation to dynamic height on the equator (095°W); and (ii) benthic ecosystem responses to oxygen change (macrobiotic infauna, meiofauna, and sulphide-oxidizing bacteria, Thioploca spp.). Shelf oxygenation episodes occurred after equatorial dynamic height increases one month before, consistent with the propagation of coastal trapped waves. Several but not all of these episodes occurred during El Niños. The benthic biota responded to oxygenation episodes by undergoing succession through three major ecological states. Under strong oxygen deficiency or anoxia, the sediments were nearly defaunated of macro-invertebrates and Thioploca was scarce, such that nematode biomass dominated the macro- and meiobiotas. When frequency of oxygenation events reduced the periods of anoxia, but the prevailing oxygen range was 10-20 ?mol L -1, mats of Thioploca formed and dominated the biomass. Finally, with frequent and intense (>40 ?mol L -1) oxygenation, the sediments were colonized by macrofauna, which then dominated biomass. The Thioploca state evolved during the 2002-2003 weak EN, while the macrofauna state was developed during the onset of the strong1997-1998 EN. Repeated episodes of strong oxygen deficiency during the summer of 2004, in parallel with the occurrence of red tides in surface waters, resulted in the collapse of Thioploca mats and development of the Nematode state. Ecological interactions may affect persistence or the transition between benthic ecosystem states.

Gutiérrez, Dimitri; Enríquez, E.; Purca, S.; Quipúzcoa, L.; Marquina, R.; Flores, G.; Graco, M.

2008-10-01

398

A survey of the benthic microfauna (foraminifera, Ostracoda) on the Basque shelf, southern Bay of Biscay  

NASA Astrophysics Data System (ADS)

In this work we describe by the first time the microfaunal content (foraminifers and ostracods) of the benthos of the Basque continental shelf, by studying the spatial distributions of benthic foraminifer and ostracod assemblages in relation to the environmental parameters affecting the sediments of this region of the Bay of Biscay. Most abundant benthic foraminifer species in the surface samples are Brizalina spathulata, Bulimina marginata, Cassidulina laevigata, Hyalinea balthica, Lobatula lobatula, Rosalina globularis, Textularia sagittula and Uvigerina peregrina. Most abundant and widespread ostracod species are Lindisfarnia guttata, Costa edwardsii and Pterygocythereis ceratoptera-jonesi group. Multivariate analyses (Cluster Q, R; DCA) of samples and species of these organisms have been performed to provide an accurate description of these distributions. Based on these analyses six different facies are characterised in this shelf, according to their microfaunal content as well as to the average values of environmental parameters (CaCO 3, POC, silt-clay and hypoxic biological markers). Of these facies, the eastern fringe and the mudpatch have a more pronounced hypoxic character relative to the western facies in this shelf. Results provided by benthic foraminifer and ostracod assemblages totally agree and indicate their dependence of the environmental parameters of the sediment. In the eastern area the influence of deeper waters has been detected, probably as upwelling through the canyons, evidenced by the occurrence of bathyal species of foraminifers ( Fontbotia wuellerstorfi, Hoeglundina elegans) and ostracods ( Krithe spp., Cytheropteron spp., Buntonia spp.). The noticeable oil-affection found in benthic specimens, very likely caused by the oil-spill of the "Prestige" in the benthonic environment of the Basque continental shelf, has been detected eight months after the spill. Despite the studied bathymetric range of 50 to 150 m, the depth interval of specimens affected by oil-spill is that of the outer shelf (93-150 m). Benthic microfauna evidence oil-pollution in the bottom sediments and demonstrate a wider affected area in the bottom of the Basque shelf than previously stated.

Pascual, Ana; Rodriguez-Lazaro, Julio; Martín-Rubio, Maite; Jouanneau, Jean-Marie; Weber, Olivier

2008-07-01

399

Benthic-Pelagic Coupling: Effects on Nematode Communities along Southern European Continental Margins  

PubMed Central

Along a west-to-east axis spanning the Galicia Bank region (Iberian margin) and the Mediterranean basin, a reduction in surface primary productivity and in seafloor flux of particulate organic carbon was mirrored in the in situ organic matter quantity and quality within the underlying deep-sea sediments at different water depths (1200, 1900 and 3000 m). Nematode standing stock (abundance and biomass) and genus and trophic composition were investigated to evaluate downward benthic-pelagic coupling. The longitudinal decline in seafloor particulate organic carbon flux was reflected by a reduction in benthic phytopigment concentrations and nematode standing stock. An exception was the station sampled at the Galicia Bank seamount, where despite the maximal particulate organic carbon flux estimate, we observed reduced pigment levels and nematode standing stock. The strong hydrodynamic forcing at this station was believed to be the main cause of the local decoupling between pelagic and benthic processes. Besides a longitudinal cline in nematode standing stock, we noticed a west-to-east gradient in nematode genus and feeding type composition (owing to an increasing importance of predatory/scavenging nematodes with longitude) governed by potential proxies for food availability (percentage of nitrogen, organic carbon, and total organic matter). Within-station variability in generic composition was elevated in sediments with lower phytopigment concentrations. Standing stock appeared to be regulated by sedimentation rates and benthic environmental variables, whereas genus composition covaried only with benthic environmental variables. The coupling between deep-sea nematode assemblages and surface water processes evidenced in the present study suggests that it is likely that climate change will affect the composition and function of deep-sea nematodes.

Pape, Ellen; Jones, Daniel O. B.; Manini, Elena; Bezerra, Tania Nara; Vanreusel, Ann

2013-01-01

400

An analysis of benthic biological dynamics in a North Sea ecosystem model  

NASA Astrophysics Data System (ADS)

This paper presents an overview and analysis of the benthic biological submodel of the European Regional Seas Ecosystem Model II (ERSEM II). This submodel consists of a detailed model description of the benthic system which is integrated with a marine ecosystem model which attempts to address the full range of pelagic and benthic biogeochemical and physical processes. The submodel simulates the seasonal dynamics of a number of functional groups, ranging from decomposers to predators and their interaction with detrital matter in the sediments. The improvements and extensions to the benthic biology submodel compared with the previous published version of the European Regional Seas Ecosystem Model are described. The improvements comprise: the reformulation of turbation and irrigation as functions of faunal activity, the inclusion of oxygen stress limitations and mortalities, a refinement of the description of detritus, additions to the diet of the filter feeders in line with the extensions to the primary production module and an extensive re-parameterisation. Using the 1° × 1° North Sea application, the submodel predictions are compared with data and the performance of the submodel assessed. Using the results of the submodel, the relation between benthic biological dynamics and its principal determinants, depth and overlying production is examined. The model is found to give qualitatively correct results. The transition in community type from anaerobe/deposit feeder in the south to a more mixed community in the north, involving aerobes and meiobenthos is also correctly predicted by the model. The biology is demonstrated to have a strong influence on nutrient efflux. The lack of resuspension/deposition processes is identified as the most significant omission from the current model.

Blackford, J. C.

1997-12-01

401

Effects of heavy metals pollution on benthic foraminifera assemblage: the Gulf of Gabes, Tunisia  

NASA Astrophysics Data System (ADS)

Benthic foraminifera are amongst the most abundant protists found in huge marine and brackish water habitat. During the last few decades, many researches had been focused on using benthic foraminifera as bioindicators of marine pollution caused by industrial, domestic and agricultural waste, oil or heavy metal contamination. The aim of this research is to investigate heavy metals pollution in superficial sediments in two industrial locations at the Gulf of Gabes and to examine the reaction of benthic foraminifera towards metallic concentration. The Gulf of Gabes, located on the eastern coast of Tunisia, is regarded as an extremely vital zone and considered as one of the most important area for fishing in the country. During last years, the coastal area of this region had known an important demographic and industrial development, leading to the presence of uncontrolled discharge. Fifteen superficial sediment samples were collected along the coastline of Skhira and Ghannouch- Gabes. They have been analyzed for Al, Cd, Cr, Cu, Pb, and Zn concentrations as well as for the species composition of benthic foraminifera. Results show three levels of metallic contamination with high concentration of cadmium and zinc. Thirty five benthic foraminifera species were identified. Ammonia parkinsoniana, Ammonia beccarii, Peneroplis planatus, Triloculina trigonula and Adelosina longirostraare are the most abundant and common species. Increasing pollution results in a lower species diversity as well as population density, with the presence of a barren zone, and more frequent abnormal specimens. A complementary statistical analysis (PCA/FA and matrix correlation) shows that heavy metals are resulting from the same anthropogenic source and negative correlation between faunal parameters (density and diversity) and pollutants concentrations.

Ayadi, Najla; Zghal, Ihsen; Bouzid, Jalel; Abdennaceur Ouali, Jamel

2014-05-01

402

Layered Slopes  

NASA Technical Reports Server (NTRS)

4 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows exposures of layered material on slopes in the south polar region near 81.9oS, 72.2oW. Layers record the history of a place, but accessing the information contained in these layers may one day require a visit by a human or robotic explorer. The south polar layers, in general, are believed to be accumulations of dust and ice that were built up in the most recent billion years or so. However, they could just as easily be sedimentary rocks from much earlier in martian history. The picture covers an area about 3 km (1.9 mi) across. The scene is illuminated by sunlight from the upper left.

2004-01-01

403

Factors influencing the spatio-temporal distribution of benthic Microcystis aeruginosa colonies (Cyanobacteria) in the hypertrophic Grangent Reservoir (Loire, France).  

PubMed

The spatio-temporal distribution of benthic colonies of Microcystis aeruginosa in Grangent Reservoir (France) in 2000 was not homogeneous and appeared to be controlled by many external factors: lake depth, station morphometry, substratum and hydraulic regime (lacustrine or fluvial). A most important concentration of benthic colonies was found at deep sites with fine sediment or at sites where the sediment was rich in organic matter. In spite of a stable water level and a minimum flow during summer, the number of benthic colonies showed great variation in the lacustrine downstream part of the reservoir. These variations may be explained by the dynamics of planktonic cyanobacteria. PMID:15506524

Latour, Delphine; Giraudet, Hervé

2004-08-01

404

Effect of benthic-pelagic coupling on dissolved organic carbon concentrations in permeable sediments and water column in the northeastern Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Large areas of the continental shelf are covered by permeable sand beds that filter substantial volumes of coastal water. This study investigated the temporal changes in and coupling between dissolved organic carbon (DOC) concentrations in the water column and pore water of nearshore permeable sediments in the northeastern Gulf of Mexico. Time series samples, collected in the nearshore environments at an exposed and a nearby protected site, showed very similar patterns of sedimentary DOC concentrations at both sites indicating that large-scale, seasonal, and weather-related processes controlled these distributions. A summer situation, with the sediment surface layer depleted in DOC and upward diffusion of recalcitrant DOC from deeper layers, was separated by a fall transition phase, where increasing winds and waves caused a mixing of the sedimentary DOC, resulting in relatively even concentrations over the investigated sediment depth (0-12 cm). The subsequent winter situation was characterized by increased DOC in the surface layer caused by filtration of degradable organic material into the sands and subsurface removal of degradable DOC. A second transition phase in early spring marked the end of the winter situation, with strong winds and waves and thorough pore water mixing, leading again to even DOC distribution in the investigated sediment layer. This transition phase initiated the next summer situation with depletion of DOC in the sediment surface layers. Our results indicate that DOC in the upper layer (?12 cm) of the shallow sands is controlled by benthic-pelagic coupling facilitated by relatively rapid solute and particle exchange in the highly permeable sediments at our study sites. The prompt responses of the surface layer DOC concentrations to the changes in the overlying water underline the dynamic character of substrate supply in the permeable sediments, setting them apart from fine-grained cohesive beds characterized by relatively stable DOC distributions.

Chipman, Lindsay; Huettel, Markus; Laschet, Matthias

2012-08-01

405

Do bottom mixed layers influence 234Th dynamics in the abyssal near-bottom water column?  

Microsoft Academic Search

Dynamics of the natural radioactive particle tracer 234Th (half-life: 24.1 days) within the abyssal water column up to 1000m above bottom and within surface sediments of the northeast Atlantic (Porcupine Abyssal Plain; depth: ?4845m) were investigated. Distributions of transmissometer voltages and potential temperature indicated a subdivision of the near-bottom water column into a benthic mixed layer (BML; thickness: ?10–65m) and

Robert Turnewitsch; Barbara M Springer

2001-01-01

406

Experimental evidence of biomineralisation for three benthic foraminiferal species under different redox conditions: implications for paleo-redox proxies interpretation  

NASA Astrophysics Data System (ADS)

Foraminifera are among the most used group of organisms for paleoceanographic and paleoenvironmental reconstructions thanks to their ability to fossilize and the preservation potential in marine sediments. Calibrations of foraminiferal-based proxies are therefore of crucial importance for precise reconstructions together with uncertainty estimates of paleoenvironments; experimental approaches are increasingly used to deepen the understanding of biological and ecological aspects of biomineralization that can influence shell geochemistry. Some of the most important and still unanswered questions are: under which circumstances can foraminiferal biomineralization take place? Can their shells record different oxygenation levels and redox fronts migrations at the sediment-water interface? The hypothesis of their ability to biomineralise even in absence of oxygen was investigated in an experimental study. Calcein-labeled specimens of three benthic foraminiferal species, Ammonia tepida, Bulimina marginata and Cassidulina laevigata were introduced in different sediment layers of reconstituted cores (up to 10 cm depth). The sediment layers were separated by 100 µm mesh-size nets preventing specimen migrations. We could therefore evaluate the ability of the species to calcify at different redox fronts in the sediment. The results show that all species were able to calcify within 2 months in hypoxic. Two of them (Ammonia tepida and Bulimina marginata) are also able to calcify in completely anoxic conditions. The result suggests that foraminifera could register in their calcareous shells the migration of redox fronts associated to bottom-water oxygen depletions and anoxic events. With the help of microanalytical tools it will potentially be possible to reconstruct past oxygen levels with much higher accuracy and precision and to obtain proxies of completely anoxic conditions.

Nardelli, Maria Pia; Barras, Christine; Metzger, Edouard; Filipsson, Helena; Jorissen, Frans; Geslin, Emmanuelle

2014-05-01

407

Linking the toxic metals to benthic community alteration: A case study of ecological status in the Bohai Bay.  

PubMed

Ecological effects and quality status of sediments in the Bohai Bay (North China) were studied by incorporating the traditional chemical analysis and benthic community structure. In the present study, paired sediments from 20 stations were sampled for chemical analysis and benthic assemblages. The overall results demonstrated that sediment impairment mainly appeared in the southern part of the Bay. The results obtained from the principal component analysis regarding benthic data and potential explanatory factors indicated that As, Hg and petroleum hydrocarbons (PHs) were responsible for the distribution of macrofaunal assemblages. Canonical correspondence analysis further showed As was significantly correlated to the benthic alteration, which provided evidence of ecological relevance to chemical substances of concern. Overall, this study revealed the metal contamination in the Bohai Bay was not as severe as previously regarded. Yet, further investigation is still needed considering the complexity of sediment matrices. PMID:24768175

Wu, Bin; Song, Jinming; Li, Xuegang

2014-06-15

408

Relationships among levels of benthic vegetation and pore-water sulfides, burrowing shrimp and infaunal amphipods in Yaquina estuary, Oregon  

EPA Science Inventory

Benthic amphipods are an important component of estuarine food webs, which in turn support ecological services provided by near shore commercial and recreational fisheries. In this study relationships among biological and geochemical aspects of the intertidal community were inve...

409

Comparison of marine productivity among Outer Continental Shelf planning areas. Supplement: An evaluation of benthic habitat primary productivity. Final report  

SciTech Connect

Literature on current primary productivity was reviewed and evaluated for each of nine benthic communities or habitats, estimates of daily and annual benthic primary productivity were derived within each community, the benthic primary estimates were related to an estimate of areal extent of each community within or adjacent to each OCS planning area. Direct comparisons between habitats was difficult because of the varying measures and methodologies used. Coastal marshes were the most prevalent habitat type evaluated. Mangrove and coral reef habitats were highly productive but occur within few planning areas. Benthic diatoms and blue-green algae are less productive in terms of estimated annual productivity on a per square meter basis; these habitats have the potential to occur across wide areas of the OCS and should not be overlooked.

Balcom, B.J.; Foster, M.A.; Fourqurean, J.J.; Heine, J.N.; Leonard, G.H.

1991-01-01

410

DEVELOPMENT OF A STREAM BENTHIC MACROINVERTEBRATE INTEGRITY INDEX (SBMII) FOR WADEABLE STREAMS IN THE MID-ATLANTIC HIGHLANDS REGION  

EPA Science Inventory

The Stream Benthic Macroinvertebrate Integrity Index (SBMII), a multimetric biotic index for assessing biological conditions of wadeable streams, was developed using seven macroinvertebrate metrics (Ephemeroptera richness, Plecoptera richness, Trichoptera richness, Collector-Filt...

411

Benthic foraminiferal response to the emergence of the Isthmus of Panama and coincident paleoceanographic changes  

USGS Publications Warehouse

Late Cenozoic benthic foraminiferal faunas from the Caribbean Deep Sea Drilling Project (DSDP) Site 502 (3052 m) and East Pacific DSDP Site 503 (3572 m) were analyzed to interpret bottom-water masses and paleoceanographic changes occurring as the Isthmus of Panama emerged. Major changes during the past 7 Myr occur at 6.7-6.2, 3.4, 2.0, and 1.1 Ma in the Caribbean and 6.7-6.4, 4.0-3.2, 2.1, 1.4, and 0.7 Ma in the Pacific. Prior to 6.7 Ma, benthic foraminiferal faunas at both sites indicate the presence of Antarctic Bottom Water (AABW). After 6.7 Ma benthic foraminiferal faunas indicate a shift to warmer water masses: North Atlantic Deep Water (NADW) in the Caribbean and Pacific Deep Water (PDW) in the Pacific. Flow of NADW may have continued across the rising sill between the Caribbean and Pacific until 5.6 Ma when the Pacific benthic foraminiferal faunas suggest a decrease in bottom-water temperatures. After 5.6 Ma deep-water to intermediate-water flow across the sill appears to have stopped as the bottom-water masses on either side of the sill diverge. The second change recorded by benthic foraminiferal faunas occurs at 3.4 Ma in the Caribbean and 4.0-3.2 Ma in the Pacific. At this time the Caribbean is flooded with cold AABW, which is either gradually warmed or is replaced by Glacial Bottom Water (GBW) at 2.0 Ma and by NADW at 1.1 Ma. These changes are related to global climatic events and to the depth of the sill between the Caribbean and Atlantic rather than the rising Isthmus of Panama. Benthic foraminiferal faunas at East Pacific Site 503 indicate a gradual change from cold PDW to warmer PDW between 4.0 and 3.2 Ma. The PDW is replaced by the warmer, poorly oxygenated PIW at 2.1 Ma. Although the PDW affects the faunas during colder intervals between 1.4 and 0.7 Ma, the PIW remains the principal bottom- water mass in the Guatemala Basin of the East Pacific.

McDougall, K.

1996-01-01

412

Pliocene-Pleistocene Benthic Foraminiferal assemblages in the Southern Bering Sea, (IODP Expedition 323).  

NASA Astrophysics Data System (ADS)

A primary objective of drilling at in the Bering Sea was to obtai high-resolution records of Pliocene-Pleistocene productivity and paleoceanography. Previous DSDP coring (Site 188) and subsequent piston coring in the region documented high sedimentation rates and the presence of appropriate microfossils for paleoceanographic studies. Drilling at Site U1341 —located at a water depth of 2177 m recovered nearly 600 m of diatomaceous sediment, and provides a record of past intermediate water conditions in the Bering Sea. The site is located just below the modern OMZ, which causes the formation of laminated sediments. Drilling at Site 1344A recovered a >700m high-resolution record of upper Pliocene to Pleistocene sediments, containing over 40 species of benthic foraminifera. Fluctuations in the intensity or depth of the OMZ should be captured by the benthic foraminiferal records at these sites. We present records of the benthic foraminiferal assemblages from 143 samples collected at approx. 3 m resolution in IODP Hole 1341B, and from 93 samples collected at 3 m resolution from Hole 1344A. Pliocene assemblages from the base of Hole 1341B to ~320 m consist entirely of agglutinated foraminifera dominated by the infaunal genera Eggerella, Karreriella, and Martinotiella. The ecological information gained from this assemblage supports other proxy information indicating high levels of organic productivity in the Bering Sea. Occasional horizons with calcareous benthic foraminifera dominated by buliminids are present, possibly owing to fluctuations in the CCD. Calcareous benthic foraminifers (mostly Bulimina, Globobulimina, Uvigerina, Melonis, nodosariids) show improved preservation in the upper part Hole 1341B starting at ~320 m (ca. 2.3 ma). This level coincides with abundant sea ice diatoms and radiolarians living in cold and oxygen-rich intermediate water masses. The fauna still indicates dysaerobic conditions, but productivity may have been reduced by seasonal sea ice coverage and an enhanced stratification of the water masses. The preservation and diversity improves again at ~150 m (ca. 1.1 ma), close to the "mid-Pleistocene transition". Benthic foraminifera assemblages from Hole 1344A display low diversity and abundance from the base of the hole until 300m (ca. 0.8 Ma), and consist mainly of Elphidium batialis, as well as Melonis, Elphidium, Globobulimina, and Cibicidoides. Above 320 m, abundance improves markedly, and the assemblage includes Uvigerina, Nonioninella, and Valvulineria. Fluctuations in the abundance of infauna are likely related to changes in productivity and deep ventilation.

Kaminski, M. A.; Kender, S.; Ciurej, A.; Balc, R.

2012-04-01

413

Major methodological constraints to the assessment of environmental status based on the condition of benthic communities  

NASA Astrophysics Data System (ADS)

The Marine Strategy Framework Directive (MSFD) was published in 2008 and requires Member States to take the necessary measures to achieve or maintain good environmental status in aquatic ecosystems by the year of 2020. The MSFD indicates 11 qualitative descriptors for environmental status assessment, including seafloor integrity, using the condition of the benthic community as an assessment indicator. Member States will have to define monitoring programs for each of the MSFD descriptors based on those indicators in order to understand which areas are in a Good Environmental Status and what measures need to be implemented to improve the status of areas that fail to achieve that major objective. Coastal and offshore marine waters are not frequently monitored in Portugal and assessment tools have only been developed very recently with the implementation of the Water Framework Directive (WFD). The lack of historical data and knowledge on the constraints of benthic indicators in coastal areas requires the development of specific studies addressing this issue. The major objective of the current study was to develop and test and experimental design to assess impacts of offshore projects. The experimental design consisted on the seasonal and interannual assessment of benthic invertebrate communities in the area of future implementation of the structures (impact) and two potential control areas 2 km from the impact area. Seasonal benthic samples were collected at nine random locations within the impact and control areas in two consecutive years. Metrics included in the Portuguese benthic assessment tool (P-BAT) were calculated since this multimetric tool was proposed for the assessment of the ecological status in Portuguese coastal areas under the WFD. Results indicated a high taxonomic richness in this coastal area and no significant differences were found between impact and control areas, indicating the feasibility of establishing adequate control areas in marine ecosystems. Nevertheless, significant differences were found between different seasons and different years, showing that the coastal benthic communities important temporal variations. Although those variations did not affect the status assessment based on metrics that considered the ratio between sensitive and tolerant taxa, diversity indices showed different classifications between seasons and years. These results indicate the need for a temporal stratification of the monitoring programs. That might be achieved by setting different thresholds for specific seasons or selecting specific monitoring seasons. It might also require a regular assessment of the environmental conditions that support the identification of outlier years, which monitoring results should be carefully considered.

Medeiros, João Paulo; Pinto, Vanessa; Sá, Erica; Silva, Gilda; Azeda, Carla; Pereira, Tadeu; Quintella, Bernardo; Raposo de Almeida, Pedro; Lino Costa, José; José Costa, Maria; Chainho, Paula

2014-05-01

414

Lava Layering  

NSDL National Science Digital Library

This is a lesson about geologic history. Learners will work together to create models of volcanic lava flows and analyze the layers that form on a planet's surface. They will sequence lava flows produced by multiple eruptions. Students will be asked to observe where the flows travel, make a model, and interpret the stratigraphy. Students will use their volcanic layering model to demonstrate the relative dating and geologic mapping principles to later be applied to satellite imagery. The lesson models scientific inquiry using the 5E instructional model and includes teacher notes and vocabulary.

415

Benthic invertebrates of fixed sites in the western Lake Michigan drainages, Wisconsin and Michigan, 1993-95  

USGS Publications Warehouse

This report describes the variability in family-level benthic-invertebrate population data and the reliability of the data as a water-quality indicator for 11 fixed surface-water sites in the Western Lake Michigan Drainages study area of the National Water-Quality Assessment Program. Benthic-invertebrate-community measures were computed for the following: number of individuals, Hilsenhoff's Family-Level Biotic Index, number and percent EPT (Ephemeroptera, Plecoptera, and Tricoptera), Margalef's Diversity Index, and mean tolerance value. Relations between these measures and environmental setting, habitat, and of chemical water quality are examined. Benthic-invertebrate communities varied greatly among fixed sites and within individual streams among multiple-reach and multiple-year sampling. The variations between multiple reaches and years were sometimes larger than those found between different fixed sites. Factors affecting benthic invertebrates included both habitat and chemical quality. Generally, fixed-site streams with the highest diversity, greatest number of benthic invertebrates, and those at which community measures indicated the best water quality also had the best habitat and chemical quality. Variations among reaches are most likely related to differences in habitat. Variations among years are most likely related to climatic changes, which create variations in flow and/or chemical quality. The variability in the data analyzed in this study shows how benthic invertebrates are affected by differences in both habitat and water quality, making them useful indicators of stream health; however, a single benthic-invertebrate sample alone cannot be relied upon to accurately describe water quality of the streams in this study. Benthic- invertebrate data contributed valuable information on the biological health of the 11 fixed sites when used as one of several data sources for assessing water quality.

Lenz, Bernard N.; Rheaume, S. J.

2000-01-01

416

The impact of a benthic filter feeder: limitations imposed by physical transport of algae to the benthos  

Microsoft Academic Search

We used an acoustic Doppler profiler to investigate the hydrodynamics of a nearshore site in western Lake Erie, and we incorporated the measured parameters in numerical simulations of phytoplankton consumption by benthic zebra mussels (Dreissena polymorpha) to examine the link between pelagic production and benthic filter feeders. Daily-averaged eddy diffusivities varied from 10-5 to 10-4 m2·s-1 at our site. Our

William J. Edwards; Chris R. Rehmann; Ellen McDonald; David A. Culver

2005-01-01

417

Simultaneous estimation of benthic fractional cover and shallow water bathymetry in coral reef areas from high-resolution satellite images  

Microsoft Academic Search

This article describes the development of a technique to estimate shallow water benthic cover and depth simultaneously from high-resolution satellite images of reef areas, specifically from the high-resolution sensor onboard IKONOS. The technique to derive the estimates of five bottom benthic cover types (sand, coral, seagrass, macroalgae and pavement) and depth from the four-band images uses a coupling of radiative

E. C. Paringit; K. Nadaoka

2012-01-01

418

Simultaneous estimation of benthic fractional cover and shallow water bathymetry in coral reef areas from high-resolution satellite images  

Microsoft Academic Search

This article describes the development of a technique to estimate shallow water benthic cover and depth simultaneously from high-resolution satellite images of reef areas, specifically from the high-resolution sensor onboard IKONOS. The technique to derive the estimates of five bottom benthic cover types (sand, coral, seagrass, macroalgae and pavement) and depth from the four-band images uses a coupling of radiative

E. C. Paringit; K. Nadaoka

2011-01-01

419

Petroleum hydrocarbons and limiting nutrients in Macura reptantia , Procambarus clarkii and benthic sediment from Qua Iboe Estuary, Nigeria  

Microsoft Academic Search

The levels of total petroleum hydrocarbons in two commonly consumed benthopelagic shellfishes, Macura reptantia and Procambarus clarkii, harvested from benthic sediment of Qua Iboe Estuary were determined using a gas chromatography with flame-ionization detector.\\u000a Seventy-two (72) samples each of benthic sediment and the shellfishes were collected monthly between June 2003 and February\\u000a 2004 covering the peak periods of the wet

Nsikak U. Benson; Joseph P. Essien; Godwin A. Ebong; Akan B. Williams

2008-01-01

420

The PROWQM physical–biological model with benthic–pelagic coupling applied to the northern North Sea  

Microsoft Academic Search

PROWQM, a 1-D depth resolving model which couples physical and microbiological processes in the water column with sedimentation\\/resuspension and benthic mineralisation processes, has been used to simulate seasonal changes of chlorophyll, nutrients and oxygen at the PROVESS north site (59°20?N 1°00?E) in the North Sea. PROWQM is derived from the 3-D model COHERENS, and improves COHEREN's benthic and pelagic biology.The

Jae-Young Lee; Paul Tett; Ken Jones; Sarah Jones; Patrick Luyten; Claire Smith; Karen Wild-Allen

2002-01-01

421

Benthic Algae as Monitors of Heavy Metals in Various Polluted Rivers by Energy Dispersive X-Ray Spectrometer  

Microsoft Academic Search

Benthic microalgae assemblages were used as monitors of copper (Cu), zinc (Zn), and chromium (Cr) in various polluted rivers of San-Yeh-Kong, in southern Taiwan, and analyzed using Scanning Electron Microscope and Energy Dispersive X-Ray Spectrometer (SEM-EDS). Under SEM-EDS, the benthic algae from seriously polluted rivers (dominant by the cyanobacteria Oscillatoria chalybea, green algae Euglena acus and diatom Nitzschia palea under

Sheue-Duan Lai; Pei-Chung Chen; Hoang-Kao Hsu

2003-01-01

422

Benthic community indicators over a long period of monitoring (2000-2012) of the Saronikos Gulf, Greece, Eastern Mediterranean.  

PubMed

An analysis of the results of the 12-year regular monitoring (2000-2012) of benthic communities in Saronikos Gulf and Elefsis Bay (Eastern Mediterranean, Greece) in relation to the functioning of the Psittalia Wastewater Treatment Plant (WWTP) and advances in treatment is presented. Benthic community indicators applied include the Bentix index adopted for the implementation of the Water Framework Directive (WFD); the diversity and species richness proposed in combination with the Bentix index for the evaluation of certain attributes of the Sea-floor Integrity descriptor for the marine waters of Greece, under the Marine Strategy Framework Directive (MSFD), and the evenness index. The benthic and environmental data were treated according to the distance from the outfall, largely accounting for the variance of the indicators, to investigate trends along the monitoring. Results showed an upgrade of the condition of the benthic communities of Saronikos Gulf throughout the monitoring period mostly demonstrated by the Bentix and diversity indices. A change in the trends of most indices was especially evident after 2004, especially in the areas more adjacent to the outfall zones, when the advanced secondary biological treatment plant was completed and commissioned. Sediment parameters' trend patterns indicate a delayed reaction to recovery processes in relation to benthic indices. An evaluation of the current status of the benthic communities based on the indices applied showed a gradient from a moderate ecological status at stations up to a distance of 8,000 m from the outfalls to good environmental and ecological status at more remote stations. At shallower stations located at a distance of more than 4,000 m from the outfall, benthic communities also present good environmental status. In Elefsis Bay, the enclosed physiography, shallower depth and local pressures result in more adverse environmental conditions for benthic communities and a more complex influence from WWTP advances. PMID:24522712

Simboura, N; Zenetos, A; Pancucci-Papadopoulou, M A

2014-06-01

423

Benthic oxygen fluxes on the Washington shelf and slope: A comparison of in situ microelectrode and chamber flux measurements  

Microsoft Academic Search

Benthic oxygen fluxes calculated from in situ microelectrode profiles arc compared with benthic flux chamber O2 uptake measurements on a transect of eight stations across the continental shelf and three stations on the slope of Washington State. Station depths ranged from 40 to 630 m and bottom-water oxygen concentrations were 127-38 FM. The fluxes measured by the two methods were

DAVID ARCHER; ALLAN DEVOL

1992-01-01

424

Benthic community respiration in the N.W. Atlantic Ocean: in situ measurements from 40 to 5200 m  

Microsoft Academic Search

Benthic community respiration was measured in situ at 9 stations along the Gay Head-Bermuda transect from depths of 40 to 5200 m. Three methods were used; bell jar respirometers, grab respirometers, and free vehicle respirometers. Benthic community respiration rates spanned three orders of magnitude, decreasing from 21.5 ml O2 m-2 h-1 at 40 m in November to 0.02 ml O2

K. L. Smith

1978-01-01

425

Leaky Layers  

NSDL National Science Digital Library

Figure from the Nature Geoscience article, Geodynamics: Layer cake or plum pudding? by Paul Tackley (Nature Geoscience 1, 157 - 158 (2008)). The figure shows the current understanding of the interaction between the 660 km discontinuity, the core-mantle boundary, downgoing slabs, upwelling plumes.

Tackley, Paul J.; Geoscience, Nature

426

Layered Liquids  

NSDL National Science Digital Library

This activity involves an exploration of density. Why does oil float on water? How does drain cleaner sink down into the clogged pipe right through standing water? These questions will be answered as students make a layered "parfait" of colored liquids ba

Eichinger, John

2009-05-30

427

Layered materials  

NASA Astrophysics Data System (ADS)

Layered compounds, materials with a large anisotropy to their bonding, electrical and/or magnetic properties, have been important in the development of solid state chemistry, physics and engineering applications. Layered materials were the initial test bed where chemists developed intercalation chemistry that evolved into the field of topochemical reactions where researchers are able to perform sequential steps to arrive at kinetically stable products that cannot be directly prepared by other approaches. Physicists have used layered compounds to discover and understand novel phenomena made more apparent through reduced dimensionality. The discovery of charge and spin density waves and more recently the remarkable discovery in condensed matter physics of the two-dimensional topological insulating state were discovered in two-dimensional materials. The understanding developed in two-dimensional materials enabled subsequent extension of these and other phenomena into three-dimensional materials. Layered compounds have also been used in many technologies as engineers and scientists used their unique properties to solve challenging technical problems (low temperature ion conduction for batteries, easy shear planes for lubrication in vacuum, edge decorated catalyst sites for catalytic removal of sulfur from oil, etc). The articles that are published in this issue provide an excellent overview of the spectrum of activities that are being pursued, as well as an introduction to some of the most established achievements in the field. Clusters of papers discussing thermoelectric properties, electronic structure and transport properties, growth of single two-dimensional layers, intercalation and more extensive topochemical reactions and the interleaving of two structures to form new materials highlight the breadth of current research in this area. These papers will hopefully serve as a useful guideline for the interested reader to different important aspects in this field and an overview of current areas of research interest.

Johnson, David; Clarke, Simon; Wiley, John; Koumoto, Kunihito

2014-06-01

428

The mobilisation of sediment and benthic infauna by scallop dredges.  

PubMed

We present the results of experiments to assess the immediate impact of scallop dredging on the seabed sediment and on the inhabiting infauna. The passage of the scallop dredge is shown to homogenise the seabed, flattening sand ripples. The turbulent wake entrains up to the equivalent of a 1 mm layer of sediment per unit of swept width, although an analysis of the finer particles material implies that the suspended silt material must originate from depths of at least 10 mm. The species most abundant in the sediment plume either swim actively in the water column or are found in, or on, the upper layers of the substrate, whereas those most abundant in core samples taken from the sediment, but not present in the net samples, are almost all tube-building or deep burrowing. The vertical stratification of sediment concentration and of animal numbers in the water column suggests that even if some of these species respond actively to the presence of the dredge, once entrained, they are transported more or less passively in the same way as the larger sediment particles. There was no difference between the core samples taken before or after towing suggesting that animals mobilised by the dredge resettle in the tow path. Our analysis does not provide any information regarding the fate of these animals. PMID:23871519

O'Neill, F G; Robertson, M; Summerbell, K; Breen, M; Robinson, L A

2013-09-01

429

PCDD/F release during benthic trawler-induced sediment resuspension.  

PubMed

Benthic trawling can cause the resuspension of large amounts of sediments. Such regular practice in the Grenland fjord system in the south of Norway has the potential to affect the fate, movement, and bioavailability of sediment-associated polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). A novel mode of exposing passive sampling devices consisting of towing semipermeable membrane devices attached to the trawl net was used to gauge in situ changes in the freely dissolved concentration of PCDD/Fs on benthic trawler-induced sediment resuspension. Significant accumulation of a number of PCDD/F congeners was observed despite the short (5 h) sampler exposure times. On average, a one order of magnitude increase in freely dissolved PCCD/F concentrations was seen within minutes of the sediment being resuspended. This observation was supported by similar changes in filtered PCDD/F concentrations measured by high-volume sampling prior to resuspension and in the sediment plume. PMID:22936523

Allan, Ian J; Nilsson, Hans C; Tjensvoll, Ingrid; Bradshaw, Clare; Naes, Kristoffer

2012-12-01

430

Fatty acid profiles of benthic environment associated with artificial reefs in subtropical Hong Kong.  

PubMed

Artificial reefs can enhance habitat heterogeneity, especially in seabed degraded by bottom-dredging and trawling. However, the trophodynamics of such reef systems are not well understood. This study provided baseline data on trophic relationships in the benthic environment associated with artificial reefs in late spring and mid summer of subtropical Hong Kong, using fatty acid profiles as an indicator. Data from sediments collected at the reef base, materials from sediment traps deployed on top and bottom of the reefs, total particulate matter from the water column and oyster tissues from reef surface were subjected to principal component analysis. Results showed variations of fatty acid profiles in the total particulate matter, upper sediment trap and oyster tissue samples collected in the two samplings, indicating seasonal, trophodynamic changes within the reef system. The wastes produced by fish aggregating at the reefs can also contribute a source of biodeposits to the nearby benthic environment. PMID:20034642

Cheung, Siu Gin; Wai, Ho Yin; Shin, Paul K S

2010-02-01

431

Nitrate Accumulation in Aerobic Hypolimnia: Relative Importance of Benthic and Planktonic Nitrifiers in an Oligotrophic Lake  

PubMed Central

Both nitrate and nitrous oxide accumulate in the hypolimnion of the oligotrophic Lake Taupo, New Zealand, throughout stratification. The two forms of oxidized nitrogen increase in concentration with increasing depth toward the sediments, where the dissolved concentrations of reduced nitrogen are two orders of magnitude higher than concentrations in the overlying water. Nitrification rates were measured by dark [14C]CO2 assays with and without the inhibitor nitrapyrin. The fastest rates were recorded for planktonic nitrifiers in the epilimnion and benthic species in the surficial 2.5 mm of the sediments. Nitrifying bacteria were least active in the deep hypolimnion. Deepwater accumulation of NO3? in Lake Taupo must therefore be a product of benthic rather than planktonic nitrification.

Vincent, Warwick F.; Downes, Malcolm T.

1981-01-01

432

Holocene melt-water variations recorded in Antarctic coastal marine benthic assemblages  

SciTech Connect

Climate changes can influence the input of meltwater from the polar ice sheets. In Antarctica, signatures of meltwater input during the Holocene may be recorded in the benthic fossils which exist at similar altitudes above sea level in emerged beaches around the continent Interpreting the fossils as meltwater proxy records would be enhanced by understanding the modern ecology of the species in adjacent marine environments. Characteristics of an extant scallop assemblage in West McMurdo Sound, Antarctica, have been evaluated across a summer meltwater gradient to provide examples of meltwater records that may be contained in proximal scallop fossils. Integrating environmental proxies from coastal benthic assemblages around Antarctica, over ecological and geological time scales, is a necessary step in evaluating the marginal responses of the ice sheets to climate changes during the Holocene.

Berkman, P.A.

1992-03-01

433

Analysis of selected benthic communities in Florida Everglades with reference to their physical and chemical environment  

USGS Publications Warehouse

Species diversity and numbers of benthic macroinvertebrates were determined at 12 sites, both canals and marshes, in the Everglades of south Florida. The values calculated are used to indicate long-term trends in water quality and variations between study areas. Species diversity at all sites was generally in a range indicative of degraded water quality. The number of organisms per square metre of bottom surface was highly variable ranging from 43 to 8,200 organisms. Chemical analysis of water and bottom material indicated no gross contamination from sewage or agricultural runoff in any of the canals where benthic organisms were collected. Other physical factors such as depth, velocity of flow, substrate type, and water-level fluctuation were responsible for the low species diversities and variable numbers of organisms, rather than contamination from urban or agricultural areas.

Waller, Bradley G.

1976-01-01

434

Preliminary observations on the benthic marine algae of the Gorringe seabank (northeast Atlantic Ocean)  

NASA Astrophysics Data System (ADS)

Examination of marine samples collected in 2006 from the Gettysburg and Ormonde seamounts on the Gorringe seabank southwest of Portugal has revealed 29 benthic Chlorophyta, Phaeophyceae (Ochrophyta), and Rhodophyta that were identified provisionally to genus and to species. Combining lists for the present and a previous expedition brings the total of algae thus far recorded to 48. The brown alga Zonaria tournefourtii and the red alga Cryptopleura ramosa were the most abundant specie