Remotely sensing the German Wadden Sea-a new approach to address national and international environmental legislation.

PubMed

Müller, Gabriele; Stelzer, Kerstin; Smollich, Susan; Gade, Martin; Adolph, Winny; Melchionna, Sabrina; Kemme, Linnea; Geißler, Jasmin; Millat, Gerald; Reimers, Hans-Christian; Kohlus, Jörn; Eskildsen, Kai

2016-10-01

The Wadden Sea along the North Sea coasts of Denmark, Germany, and the Netherlands is the largest unbroken system of intertidal sand and mud flats in the world. Its habitats are highly productive and harbour high standing stocks and densities of benthic species, well adapted to the demanding environmental conditions. Therefore, the Wadden Sea is one of the most important areas for migratory birds in the world and thus protected by national and international legislation, which amongst others requires extensive monitoring. Due to the inaccessibility of major areas of the Wadden Sea, a classification approach based on optical and radar remote sensing has been developed to support environmental monitoring programmes. In this study, the general classification framework as well as two specific monitoring cases, mussel beds and seagrass meadows, are presented. The classification of mussel beds profits highly from inclusion of radar data due to their rough surface and achieves agreements of up to 79 % with areal data from the regular monitoring programme. Classification of seagrass meadows reaches even higher agreements with monitoring data (up to 100 %) and furthermore captures seagrass densities as low as 10 %. The main classification results are information on area and location of individual habitats. These are needed to fulfil environmental legislation requirements. One of the major advantages of this approach is the large areal coverage with individual satellite images, allowing simultaneous assessment of both accessible and inaccessible areas and thus providing a more complete overall picture.

Can guild- or site-specific contrasts in trends or phenology explain the changed role of the Dutch Wadden Sea for fish?

NASA Astrophysics Data System (ADS)

Tulp, Ingrid; van der Veer, Henk W.; Walker, Paddy; van Walraven, Lodewijk; Bolle, Loes J.

2017-09-01

The Wadden Sea bordering the Dutch, German and Danish coast, is traditionally a region with important functions for many fish species: as a nursery area for juveniles (marine juveniles), as a feeding area, as a transit to and from fresh water, and resident species complete their whole life cycle there. Because of indications that the importance of the Dutch Wadden Sea has changed drastically for many species during the past decades, we analysed and classified trends of 24 common fish species in the last 45 years, which were assigned to 5 different ecological guilds. Trends were examined for three Wadden Sea regions and compared to trends in the adjacent two North Sea coastal regions. For these analyses we made a combined use of two longterm time series: an annual beamtrawl survey, the Demeral Fish Survey (DFS) with a high spatial but poor seasonal resolution and a fyke series with a high seasonal but poor spatial resolution. We investigated for which species the DFS survey was appropriate for trend analysis, and we evaluated whether a change in timing may contribute to patterns in DFS time trends. Total fish biomass showed a similar pattern in all tidal basins with an increase from 1970 to 1980, a peak in the mid-1980s and a strong decline from 1980 to 2000, with a subsequent stable trend. The pattern in the coastal region deviated especially in the past 10 years, with a further decline along the Dutch Wadden coast and an increase along the mainland coast. Most dramatic declines throughout the Wadden Sea occurred in species belonging to the marine juvenile guild, notably plaice, sole and dab. A declining trend in marine juveniles is on-going in the western part, while it recently stabilised or even increased in the central and eastern part and in the coastal regions. Resident species showed more variable trends in the Wadden Sea with less pronounced directions: both increases and decreases occurred. In the coastal regions, several resident species have increased

Abundance and tidal behaviour of pelagic fish in the gateway to the Wadden Sea

NASA Astrophysics Data System (ADS)

Couperus, Bram; Gastauer, Sven; Fässler, Sascha M. M.; Tulp, Ingrid; van der Veer, Henk W.; Poos, Jan Jaap

2016-03-01

The shallow coast of The Netherlands is an important habitat for small pelagic fish. They form one of the major links between plankton and the higher trophic levels. Predatory fish, sea mammals and birds rely on small pelagic fish as a major food source. Currently, monitoring of fish in the Dutch coastal zone mainly focuses on demersal species, using bottom trawls and fykes. Four hydro-acoustic surveys were carried out in May and October 2010/2011 in the Marsdiep area, a relatively deep tidal inlet in the western Wadden Sea, to quantify abundances of pelagic fish. The aims of this study were to (1) describe temporal and vertical variations in fish distribution and school dimensions in relation to tide, and (2) estimate biomass of pelagic fish and their proportion to total fish biomass. The biomass of pelagic fish in the Marsdiep area ranged between 23 and 411 kg/ha. These were mainly sprat, but also young herring, anchovy and pilchard. The fish was scattered in small schools with volumes smaller than 5m3 and concentrated in the top 10 m below the surface. There was a clear effect of tidal cycle on school volume and fish abundance, with larger densities and larger schools at high tide compared to low tide. In May, sandeel contributed substantially to the pelagic assemblage, whereas in October sandeel was absent in the trawl catches, most likely because they stayed buried in the seabed from late summer to spring. The presence of pilchard and anchovy confirmed their re-establishment in the Southern North Sea and Wadden Sea. The abundance of pelagic fish exceeded the biomass of demersal fish in the western Wadden Sea by an order of magnitude. This finding is relevant for ecosystem studies. The fact that this study suggests that small pelagics outnumber demersal species to such a large extent calls for a rethinking of the allocation of monitoring effort in the Dutch coastal zone.

Residual circulation and suspended sediment transport in the Dutch Wadden Sea

NASA Astrophysics Data System (ADS)

Duran-Matute, Matias; Sassi, Maximiliano; de Boer, Gerben; Grawë, Ulf; Gerkema, Theo; van Kessel, Thijs; Cronin, Katherine

2014-05-01

The Dutch Wadden Sea (DWS), situated between continental Europe and the Dutch Wadden Islands, is a semi enclosed basin connected to the North Sea by a series of tidal inlets and composed mainly of tidal flats and sea gullies. The DWS is of high ecological importance due to its biodiversity and has been declared a World Heritage site by UNESCO. It is a dynamic area subject to regional relative sea level rise due to global sea level rise, postglacial rebound and gas exploitation. For intertidal areas to continue to serve as feeding ground for migratory birds, a net import of sediment is required. Observations are crucial but provide only scarce information in space and time. Hence, to estimate the net influx of suspended sediment into the DWS, realistic high resolution three-dimensional numerical simulations have been carried out using the General Estuarine Transport Model (GETM). The hydrodynamics are mainly governed by the tides, the fresh water discharge from several sluices into the DWS and wind variability. It is expected that the transport of suspended particulate matter (SPM) is governed by the same factors, too, in combination with sediment sink and source terms. For validation, the results are compared against different observational data sets, such as tidal gauges, temperature and salinity at a fixed station, and the volumetric flux rate through one of the inlets obtained from an acoustic Doppler current profiler (ADCP) attached to a ferry. SPM transport is modeled for four different sediment classes each of which is defined by the critical shear stress and the settling velocity. Results show a clear net import of SPM through one of the inlets, which is in agreement with the observations. First estimates of the total sediment fluxes through the different inlets are presented together with an analysis on their variability and sensibility to the external forcing. Of particular importance is the net export of SPM during storms as well as the role of storms on

Diseases of flounder ( Platichthys Flesus L.) in the Dutch Wadden Sea, and their relation to stress factors

NASA Astrophysics Data System (ADS)

Dick Vethaak, A.

In 1988 a survey was conducted on the occurrence of gross pathologies in flounder ( Platichthys flesus L.) in the Dutch Wadden Sea in relation to stress factors, especially near fresh-water drainage sluices. A total of 9608 flounder were collected from 16 sites in June and September. Diseases recorded were: skin ulcers (affecting 7.7% of fish); fin rot (2.8%; only included in the study in September); lymphocystis (3.7%); skeletal deformities (0.3%); liver nematode infections (5.0%); intestinal cysts of the parasite Glugea sp. (0.4%); and liver nodules (pre-neoplastic and neoplastic lesions) (< 0.1%). Prevalences of skin ulcers and fin rot in Wadden Sea flounder are considerably higher than in those captured off the Dutch North Sea coast or in the Elbe estuary in Germany. These high disease levels in the Wadden Sea, however, are largely due to extremely high prevalences of skin ulcers observed near the drainage sluices of Lake IJssel, indicating a localized effect. Fin rot occurs at relatively high prevalences over the whole study area, but the data should be interpreted with some caution, due to diagnostic problems. Associations with possible disease determinants were investigated and causal hypotheses formulated. In general fish seem to develop skin diseases at sites with strong salinity fluctuations. Nutritional deficiencies possibly related to strong salinity fluctuations, high bacterial loads in the environment and obstacles to fish migration through sluices are amongst the most likely factors determining the locally high levels of skin ulcers. Although not established, it is possible that pollution-related factors and contaminant bioavailability are important. The stress imposed by a combination of these factors may adversely affect the immune system, making the fish vulnerable to opportunistic bacterial infection.

Reconstruction of the total N and P inputs from the IJsselmeer into the western Wadden Sea between 1935-1998

NASA Astrophysics Data System (ADS)

van Raaphorst, Wim; de Jonge, Victor N.

2004-03-01

In this paper we reconstruct the Total Nitrogen (TN) and Total Phosphorus (TP) inputs into the western Wadden Sea from its major freshwater source the lake IJsselmeer between 1935-1998. The reconstruction is based on the TN and TP loads of the river Rhine at the German/Dutch border and follows the aquatic continuum approach to calculate loads further downstream in (1) the river IJssel feeding the IJsselmeer, and (2) the discharge of this lake into the western Wadden Sea. Our objectives are to determine (1) how the signal of changing nutrient loads of the Rhine is transferred downstream, and (2) how hydrological changes in the rivers-and-lake system affected the TN and TP discharges into the western Wadden Sea. Observational data from which TN and TP loads of the river Rhine could be calculated date back to the 1960s and we used background loads for European rivers for the period before World War II. The period in between was interpolated using the historic scenarios of watershed land use and management tested for the hypothetical Phison river (Billen and Garnier, 1997, Aquat. Microb. Ecol. 13, 3-17), adapted for the hydrology of the Rhine. The interpolations were constrained by loads of dissolved inorganic N and P compounds, for which data go back to the 1930s. Using the reconstructed loads of the river Rhine, TN and TP loads of the river IJssel and the lake IJsselmeer were calculated with simple mass balance models that were calibrated against data available from 1972-1993 onwards. Results show a gradual 12-fold increase of the TN discharge of the IJsselmeer into the Wadden Sea from 1935 to 1988, after which it decreased to levels still ˜5 fold those in 1935. The discharge of TP increased more abruptly in the early 1960s to values in 1983 ˜10 fold those before 1965, followed by a sharp decrease to values still ˜2.5 fold those before 1965. These patterns resemble those in the river Rhine, but are modified due to (1) variability of other sources to the lake, and

Data access systems in the real world: How distributed environmental and socio-economic data from the Dutch Wadden Sea are being integrated and made accessible through one portal, using the SeaDataNet infrastructure as a basis

NASA Astrophysics Data System (ADS)

De Bruin, T.; Thijsse, P.

2013-12-01

The Wadden Sea, an UNESCO World Heritage Site along the Northern coasts of The Netherlands, Germany and Denmark, is a very valuable, yet also highly vulnerable tidal flats area. It is noted for its ecological diversity and value, being a stopover for large numbers of migrating birds. The Wadden Sea is also used intensively for economic activities by inhabitants of the surrounding coasts and islands, as well as by the many tourists visiting the area every year. A whole series of monitoring programmes of both ecological and socio-economic parameters is carried out by a range of governmental bodies and institutes, to study the natural processes occuring in the Wadden Sea ecosystems as well as the influence of human activities on those ecosystems. Yet, the monitoring programmes are scattered and it is difficult to get an overview of those monitoring activities or to get access to the data resulting from those monitoring programmes. The Wadden Sea Long Term Ecosystem Research (WaLTER) project aims to: 1. Provide access through one data portal to a base set of consistent, standardized, long-term data on changes in the Wadden Sea ecological and socio-economic systems, in order to model and understand interrelationships with human use, climate variation and possible other drivers. 2. Provide a research infrastructure, open access to commonly shared databases, educational facilities and one or more field sites in which experimental, innovative and process-driven research can be carried out. This presentation will, after a short introduction of the WaLTER-project (2011-2015), focus on the distributed data access infrastructure which is being developed and used for WaLTER. This is based on and makes use of the existing data access infrastructure of the Netherlands National Oceanographic Data Committee (NL-NODC), which has been operational since early 2009. The NL-NODC system is identical to and in fact developed by the European SeaDataNet project, furthering standardisation

Endoparasites in common eiders Somateria mollissima from birds killed by an oil spill in the northern Wadden Sea

NASA Astrophysics Data System (ADS)

Thieltges, David W.; Hussel, Birgit; Baekgaard, Henrik

2006-05-01

Mass mortalities of common eiders Somateria mollissima have been ascribed to high parasite loads. However, the actual role of parasites in mortalities is disputed as in the case of a mass mortality of eiders in the Wadden Sea in the winter of 1999/2000. A critical evaluation of the role of parasites in eider mass mortalities is hampered by (1) a lack of data on actual parasite loads of the birds involved, (2) missing regional data for comparison, and (3) a lack of unbiased samples: investigations are often based on dead beached individuals, which are presumably the more heavily infected birds of a population and thus more likely to die and be washed ashore. Although published data on parasite loads in birds of the winter 1999/2000 mortality are available, no data on background parasitism in eiders from the Wadden Sea exist, making an evaluation of the potential role of parasites in this mortality event difficult. By investigating endoparasites of 102 eiders affected by an oil spill in the northern Wadden Sea in winter 1998/1999, we provide a data set of background parasitism in wintering eiders from the Wadden Sea. We found 13 different parasite taxa with high prevalence values (% infected birds) in the acanthocephalan Profilicollis botulus, the nematode Amidostomum acutum, cestodes and trematodes. In some taxa we observed pronounced differences in prevalence values between juvenile eiders and adults, as well as between adult sexes. The parasite composition shows that bivalves, crabs ( Carcinus maenas) and other crustaceans are important sources of infections by being intermediate hosts. This is partly mirrored in the food content of eider stomachs where bivalves and crabs were predominantly found. Intensities of the acanthocephalan P. botulus, suspected of causing eider mortalities, were especially high in juveniles (1112 ± 416 ind per infected host), but lower in adult males (40 ± 7) and adult females (81 ± 18). However, no extraordinary mortality event was

Phosphorus limitation during a phytoplankton spring bloom in the western Dutch Wadden Sea

NASA Astrophysics Data System (ADS)

Ly, Juliette; Philippart, Catharina J. M.; Kromkamp, Jacco C.

2014-04-01

Like many aquatic ecosystems, the western Dutch Wadden Sea has undergone eutrophication. Due to changes in management policy, nutrient loads, especially phosphorus decreased after the mid-80s. It is still under debate, however, whether nutrients or light is limiting phytoplankton production in the western Wadden Sea, as studies using monitoring data delivered sometimes opposite conclusions and outcomes were related to years, seasons and approaches used. Clearly, the monitoring data alone were not sufficient. We therefore examined the limiting factors for the phytoplankton spring bloom using different experimental approaches. During the spring bloom in April 2010, we investigated several nutrient regimes on natural phytoplankton assemblages at a long term monitoring site, the NIOZ-Jetty sampling (Marsdiep, The Netherlands). Four bioassays, lasting 6 days each, were performed in controlled conditions. From changes in phytoplankton biomass, chlorophyll-a (Chla), we could conclude that the phytoplankton in general was mainly P-limited during this period, whereas a Si-P-co-limitation was likely for the diatom populations, when present. These results were confirmed by changes in the photosynthetic efficiency (Fv/Fm), in the expression of alkaline phosphatase activity (APA) measured with the fluorescent probe ELF-97, and in the 13C stable isotope incorporation in particulate organic carbon (POC). During our bioassay experiments, we observed a highly dynamic phytoplankton community with regard to species composition and growth rates. The considerable differences in net population growth rates, occurring under more or less similar environmental incubation conditions, suggest that phytoplankton species composition and grazing activity by small grazers were important structuring factors for net growth during this period.

Intra-tidal variability of the vertical current structure in the western Dutch Wadden Sea

NASA Astrophysics Data System (ADS)

de Vries, Jurre; Ridderinkhof, Herman; van Aken, Hendrik

2014-05-01

Long-term velocity measurements are presented which were collected during three different seasons at one single location in an estuarine basin of the western Dutch Wadden Sea. These data are used to investigate the processes that determine the variability of the vertical current structure in the western Dutch Wadden Sea, in combination with simplified model runs using the one-dimensional water column model GETM (http://www.getm.eu/). Jay and Musiak [1996] were the first to suggest that intra-tidal variations in the vertical current might be important in determining the residual circulation patterns. More research [e.g. Stacey et al., 2001; Burchard and Hetland, 2010] has supported this hypothesis. Recently, lateral processes have been shown to influence the vertical current structure of alongstream velocity and hence the residual circulation [e.g. Lerczak and Geyer, 2004; Burchard and Schuttelaars, 2012]. Therefore to better understand the tidal dynamics in the western Dutch Wadden Sea, it is crucial to understand the processes that determine the vertical current structure. The two main findings of this study are that the complex bathymetry at the study site seems to produce an intra-tidal asymmetry in near-bed velocities and secondly that cross-stream processes strongly modify the current structure during late flood. Near-bed velocity and the bed roughness are greater during ebb than during flood. The GETM simulations suggest that vertical mixing during ebb is sufficient to destroy vertical stratification generated by classical tidal straining. The cross-stream current during late flood generate vertical stratification and drive an early reversal of the flood current near the surface. Therefore, it is hypothesized that this processes might increase the residual estuarine circulation at the study site. References - Burchard, H., Hetland, R.D. (2010), Quantifying the contributions of tidal straining and gravitational circulation to residual circulation in

Interaction between birds and macrofauna within food webs of six intertidal habitats of the Wadden Sea.

PubMed

Horn, Sabine; de la Vega, Camille; Asmus, Ragnhild; Schwemmer, Philipp; Enners, Leonie; Garthe, Stefan; Binder, Kirsten; Asmus, Harald

2017-01-01

The determination of food web structures using Ecological Network Analysis (ENA) is a helpful tool to get insight into complex ecosystem processes. The intertidal area of the Wadden Sea is structured into diverse habitat types which differ in their ecological functioning. In the present study, six different intertidal habitats (i.e. cockle field, razor clam field, mud flat, mussel bank, sand flat and seagrass meadow) were analyzed using ENA to determine similarities and characteristic differences in the food web structure of the systems. All six systems were well balanced between their degree of organization and their robustness. However, they differed in their detailed features. The cockle field and the mussel bank exhibited a strong dependency on external imports. The razor clam field appeared to be a rather small system with low energy transfer. In the mud flat microphytobenthos was used as a main food source and the system appeared to be sensitive to perturbations. Bird predation was the most pronounced in the sand flat and the seagrass meadow and led to an increase in energy transfer and parallel trophic cycles in these habitats. Habitat diversity appears to be an important trait for the Wadden Sea as each subsystem seems to have a specific role in the overall functioning of the entire ecosystem.

Interaction between birds and macrofauna within food webs of six intertidal habitats of the Wadden Sea

PubMed Central

Horn, Sabine; de la Vega, Camille; Asmus, Ragnhild; Schwemmer, Philipp; Enners, Leonie; Garthe, Stefan; Binder, Kirsten; Asmus, Harald

2017-01-01

The determination of food web structures using Ecological Network Analysis (ENA) is a helpful tool to get insight into complex ecosystem processes. The intertidal area of the Wadden Sea is structured into diverse habitat types which differ in their ecological functioning. In the present study, six different intertidal habitats (i.e. cockle field, razor clam field, mud flat, mussel bank, sand flat and seagrass meadow) were analyzed using ENA to determine similarities and characteristic differences in the food web structure of the systems. All six systems were well balanced between their degree of organization and their robustness. However, they differed in their detailed features. The cockle field and the mussel bank exhibited a strong dependency on external imports. The razor clam field appeared to be a rather small system with low energy transfer. In the mud flat microphytobenthos was used as a main food source and the system appeared to be sensitive to perturbations. Bird predation was the most pronounced in the sand flat and the seagrass meadow and led to an increase in energy transfer and parallel trophic cycles in these habitats. Habitat diversity appears to be an important trait for the Wadden Sea as each subsystem seems to have a specific role in the overall functioning of the entire ecosystem. PMID:28489869

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

NASA Astrophysics Data System (ADS)

Lackschewitz, D.; Reise, K.

1998-06-01

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

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

PubMed

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

2006-06-01

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

Contribution of different generations of the brown shrimp Crangon crangon (L.) in the Dutch Wadden Sea to commercial fisheries: A dynamic energy budget approach

NASA Astrophysics Data System (ADS)

Campos, Joana; Van der Veer, Henk W.; Freitas, Vânia; Kooijman, Sebastiaan A. L. M.

2009-08-01

In this paper a contribution is made to the ongoing debate on which brown shrimp generation mostly sustains the autumn peak in coastal North Sea commercial fisheries: the generation born in summer, or the winter one. Since the two perspectives are based on different considerations on the growth timeframe from settlement till commercial size, the Dynamic Energy Budget (DEB) theory was applied to predict maximum possible growth under natural conditions. First, the parameters of the standard DEB model for Crangon crangon L. were estimated using available data sets. These were insufficient to allow a direct estimation, requiring a special protocol to achieve consistency between parameters. Next, the DEB model was validated by comparing simulations with published experimental data on shrimp growth in relation to water temperatures. Finally, the DEB model was applied to simulate growth under optimal food conditions using the prevailing water temperature conditions in the Wadden Sea. Results show clear differences between males and females whereby the fastest growth rates were observed in females. DEB model simulations of maximum growth in the Wadden Sea suggest that it is not the summer brood from the current year as Boddeke claimed, nor the previous winter generation as Kuipers and Dapper suggested, but more likely the summer generation from the previous year which contributes to the bulk of the fisheries recruits in autumn.

Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years

NASA Astrophysics Data System (ADS)

Reise, K.; Schubert, A.

1987-03-01

The benthic macrofauna of a tidal inlet in the northern Wadden Sea was sampled with grab and dredge in 1924 1926 (Hagmeier & Kändler, 1927), and again in 1985 and 1986. The comparison of surveys from consecutive years, as well as observations from an adjacent area, are employed to separate spurious from real long-term changes. Several epibenthic species of the 1920s became rare or absent in the 1980s. Oyster beds and reefs of the colonial polychaete Sabellaria spinulosa have disappeared completely. On the other hand, mussel beds have extended their range, and the abundance of mobile infauna has increased. The total number of species has remained approximately the same. Compared to surveys from consecutive years, the 60-year interval has doubled the species turnover rate, and has decreased the similarity in relative abundances by one third. The observed losses are best explained by the impact of dredging and trawling on the benthic fauna, while gains seem to indicate coastal eutrophication.

Long-term effects of mechanical harvesting of lugworms Arenicola marina on the zoobenthic community of a tidal flat in the Wadden Sea

NASA Astrophysics Data System (ADS)

Beukema, J. J.

More than half of the annual catch of about 30 million lugworms Arenicola marina from the Dutch Wadden Sea originates from digging machines which make 40-cm deep guilles in a few restricted tidal-flat areas (Texel, Balgzand) in the westernmost part of the Wadden Sea. Four successive years (1978-1982) of frequent disturbance by a lugworm dredge of one of the 15 sampling stations involved in a long-term study of the dynamics of the macrozoobenthos on Balgzand allowed a study of long-term effects of mechanical lugworm digging. Within an area of about 1 km 2, a near-doubling of the annual lugworm mortality rate resulted in a gradual and substantial decline of the local lugworm stock from more than twice the overall Balgzand mean at the start of the 4-year digging period to a value close to this mean at the end of the period (when the dredge moved to a richer area). Simultaneously, total zoobenthic biomass declined even more by the almost complete extinction of the population of larger gaper clams Mya arenaria that initially comprised half of the total biomass. Of the other, mostly short-lived, species only Heteromastus filiformis showed a clear reduction during the dredging period. Recovery of the biomass of the benthos took several years, particularly by the slow re-establishment of a Mya population with a normal size and age structure.

The influence of four macrozoobenthic species on the abundance of the amphipod Corophium volutator on tidal flats of the Wadden Sea

NASA Astrophysics Data System (ADS)

Flach, E. C.

On the tidal flats of the Wadden Sea, a zonation pattern can be found with Corophium volutator and Nereis diversicolor as the dominating species of the upper intertidal zone and Arenicola marina and Cerastoderma edule as the dominating species of the lower zone. As C. volutator can live under a great variety of physical conditions, its restriction to higher areas might result from biotic interactions. This was investigated by field experiments on a tidal flat in the westernmost part of the Wadden Sea. Within large depopulated areas, small plots were recolonized with different densities of N. diversicolor, A. marina, C. edule and Macoma balthica and the subsequent settlement and dynamics of C. volutator were studied. In addition, A. marina and/or C. edule were added to or removed from small plots within a natural benthic community. Neither the presence of M. balthica not that of N. diversicolor significantly affected the abundance of C. volutator. A strongly negative effect was found of C. edule when present in high densities, whereas A. marina negatively affected C. volutator abundance already at relatively low densities. Local removals of A. marina and C. edule from their own zone resulted in increases of Corophium numbers at these locations and local additions of these species within the Corophium zone resulted in decreases of Corophium numbers at these locations. It is suggested that the major species to restrict C. volutator effectively to the upper tidal zone is A. marina.

Helminth parasites of the digestive tract of the oystercatcher, Haematopus ostralegus, in the Wadden Sea, The Netherlands

NASA Astrophysics Data System (ADS)

Borgsteede, F. H. M.; Van den Broek, E.; Swennen, C.

The digestive tracts of 90 oystercatchers (equal numbers of males and females and of juveniles, subadults and adults) wintering in the Dutch Wadden Sea were examined for helminth parasites. The nematodes Capillaria sp. (36.7%) and Streptocara crassicauda (7.8%) were found in the stomach. Unidentified cestodes (76.7%) and the trematodes Psilostomum brevicolle (42.2%), Notocotylus sp. (81.1%), and unidentified gymnophallids (100%) were found in the intestine and caeca. Two birds were infected with Gymnophallidae only, while all other birds contained additional helminth species. Compared with subadult and adult birds, the juveniles had significantly more infections with Capillaria sp. and cestodes. Moreover, the juveniles were infected with a greater variety of species. No further relation was found between the presence of helminths or worm numbers and age groups or sexes of birds.

Integration of TerraSAR-X, RapidEye and airborne lidar for remote sensing of intertidal bedforms on the upper flats of Norderney (German Wadden Sea)

NASA Astrophysics Data System (ADS)

Adolph, Winny; Jung, Richard; Schmidt, Alena; Ehlers, Manfred; Heipke, Christian; Bartholomä, Alexander; Farke, Hubert

2017-04-01

The Wadden Sea is a large coastal transition area adjoining the southern North Sea uniting ecological key functions with an important role in coastal protection. The region is strictly protected by EU directives and national law and is a UNESCO World Heritage Site, requiring frequent quality assessments and regular monitoring. In 2014 an intertidal bedform area characterised by alternating crests and water-covered troughs on the tidal flats of the island of Norderney (German Wadden Sea sector) was chosen to test different remote sensing methods for habitat mapping: airborne lidar, satellite-based radar (TerraSAR-X) and electro-optical sensors (RapidEye). The results revealed that, although sensitive to different surface qualities, all sensors were able to image the bedforms. A digital terrain model generated from the lidar data shows crests and slopes of the bedforms with high geometric accuracy in the centimetre range, but high costs limit the operation area. TerraSAR-X data enabled identifying the positions of the bedforms reflecting the residual water in the troughs also with a high resolution of up to 1.1 m, but with larger footprints and much higher temporal availability. RapidEye data are sensitive to differences in sediment moisture employed to identify crest areas, slopes and troughs, with high spatial coverage but the lowest resolution (6.5 m). Monitoring concepts may differ in their remote sensing requirements regarding areal coverage, spatial and temporal resolution, sensitivity and geometric accuracy. Also financial budgets limit the selection of sensors. Thus, combining differing assets into an integrated concept of remote sensing contributes to solving these issues.

Tidal and subtidal exchange flows at an inlet of the Wadden Sea

NASA Astrophysics Data System (ADS)

Valle-Levinson, Arnoldo; Stanev, Emil; Badewien, Thomas H.

2018-03-01

Observations of underway velocity profiles during complete spring and neap tidal cycles were used to determine whether the spatial structures of tidal and subtidal flows at a tidal inlet in a multiple-inlet embayment are consistent with those observed at single-inlet embayments. Measurements were obtained at the Otzumer Balje, one of the multiple inlets among the East Frisian Islands of the Wadden Sea. The 1.5 km-wide inlet displayed a bathymetric profile consisting of a channel ∼15 m deep flanked by <5 m shoals. Neap tide observations spanned 36 h in the period May 11-12, 2011, while spring tide measurements exceeded 48 h from May 17 to May 19, 2011. Analysis of observations indicate that frictional effects from bathymetry molded tidal flows. Spatial distributions of semidiurnal tidal current amplitude and phase conform to those predicted by an analytical model for a basin with one inlet. Maximum semidiurnal flows appear at the surface in the channel, furthest away from bottom friction effects. Therefore, Otzumer Balje displays tidal hydrodynamics that are independent of the other inlets of the embayment. Subtidal exchange flows are laterally sheared, with residual inflow in the channel combined with outflow over shoals. The spatial distribution of these residual flows follow theoretical expectations of tidally driven flows interacting with bathymetry. Such distribution is similar to the tidal residual circulation at other inlets with only one communication to the ocean, suggesting that at subtidal scales the Otzumer Balje responds to tidal forcing independently of the other inlets.

Seasonal variation in the occurrence of planktic bivalve larvae in the Schleswig-Holstein Wadden Sea

NASA Astrophysics Data System (ADS)

Pulfrich, Andrea

1997-03-01

In the late 1980s, recruitment failures of the mussel Mytilus edulis led to economic problems in the mussel fishing and cultivation industries of northwestern Europe. As part of a collaborative study to gain a better understanding of the mechanisms affecting recruitment processes of mussels, plankton samples were collected regularly over a four-year period (1990-1993) from three stations in the Schleswig-Holstein Wadden Sea. The bivalve component of the plankton was dominated by the Solenidae, which was almost exclusively represented by Ensis americanus (= directus). M. edulis was the second most abundant species. Abundances of mussel larvae peaked 2 to 4 weeks after spawning maxima in the adult populations. Although variations in timing and amplitude of the total larval densities occurred, annual abundances of M. edulis larvae remained stable during the study period, and regional abundance differences were insignificant. A close relationship was found between peaks in larval abundance and phytoplankton blooms. Differences in larval concentrations in the ebb and the flow currents were insignificant. Planktic mussel larvae measured between 200 μm and 300 μm, and successive cohorts were recognizable in the majority of samples. Most larvae were found to originate from local stocks, although imports from outside the area do occur.

Seasonal dynamics and functioning of the Sylt-Rømø Bight, northern Wadden Sea

NASA Astrophysics Data System (ADS)

de la Vega, Camille; Horn, Sabine; Baird, Dan; Hines, David; Borrett, Stuart; Jensen, Lasse Fast; Schwemmer, Philipp; Asmus, Ragnhild; Siebert, Ursula; Asmus, Harald

2018-04-01

The Wadden Sea undergoes large seasonal changes in species abundance and biomass comprising its complex food web. This study examined four carbon food web models of the Sylt-Rømø Bight, one for each season. Each flow model consisted of 66 compartments depicting the respective biomass and energy budget of each ecosystem component and the flows between them. Ecological network analysis (ENA), a set of algorithms to evaluate the functioning of ecological networks, was used to assess the seasonal variability in the system properties of the Sylt-Rømø Bight food webs. We used an uncertainty analysis to quantitatively evaluate the significance of inter-seasonal differences. Clear seasonal variation was observed in most of the whole system indicators such as the flow diversity, the effective link density and the relative redundancy which varied by 12.8%, 17.3% and 10.3% respectively between the highest in summer and the lowest during fall and winter, whereas the relevant ascendency ratio was the highest in winter during the least active months. Other indices such as the average mutual information index, which fluctuated between 1.73 in fall and 1.79 in spring, showed no significant variation between seasons. Results from ENA have great potential for ecosystem management, as it provides a holistic assessment of the functioning of ecosystems.

The Skallingen spit, Denmark: birth of a back-barrier saltmarsh

NASA Astrophysics Data System (ADS)

Bartholdy, Jesper; Brivio, Lara; Bartholdy, Anders; Kim, Daehyun; Fruergaard, Mikkel

2018-04-01

The formation and evolution of a modern saltmarsh platform on the barrier spit Skallingen in the northernmost part of the Wadden Sea was investigated through historical map records, 12 orthophotos covering the period from 1945 to 2012, sediment cores and cross-sectional creek profiles. The barrier spit, which constitutes the foundation of the saltmarsh platform, formed in about 50 years in the seventeenth century. After its formation the spit was left as a bare sandflat for about 200 years. Along with the development of foredunes, an increased availability of fine-grained sediment and establishment of vegetation in the beginning of the 1890s, the saltmarsh area formed in about 100 years, while the development of a large system of saltmarsh creeks took place in just ca. 50 years. The development of the drainage network, saltmarsh creek morphology and sedimentology during the saltmarsh formation are described in detail and analysed with special attention to the transformation rate from bare sandflat to a genuine vegetation-covered back-barrier saltmarsh.

Advanced Water Quality Modelling in Marine Systems: Application to the Wadden Sea, the Netherlands

NASA Astrophysics Data System (ADS)

Boon, J.; Smits, J. G.

2006-12-01

There is an increasing demand for knowledge and models that arise from water management in relation to water quality, sediment quality (ecology) and sediment accumulation (ecomorphology). Recently, models for sediment diagenesis and erosion developed or incorporated by Delft Hydraulics integrates the relevant physical, (bio)chemical and biological processes for the sediment-water exchange of substances. The aim of the diagenesis models is the prediction of both sediment quality and the return fluxes of substances such as nutrients and micropollutants to the overlying water. The resulting so-called DELWAQ-G model is a new, generic version of the water and sediment quality model of the DELFT3D framework. One set of generic water quality process formulations is used to calculate process rates in both water and sediment compartments. DELWAQ-G involves the explicit simulation of sediment layers in the water quality model with state-of-the-art process kinetics. The local conditions in a water layer or sediment layer such as the dissolved oxygen concentration determine if and how individual processes come to expression. New processes were added for sulphate, sulphide, methane and the distribution of the electron-acceptor demand over dissolved oxygen, nitrate, sulphate and carbon dioxide. DELWAQ-G also includes the dispersive and advective transport processes in the sediment and across the sediment-water interface. DELWAQ-G has been applied for the Wadden Sea. A very dynamic tidal and ecologically active estuary with a complex hydrodynamic behaviour located at the north of the Netherlands. The predicted profiles in the sediment reflect the typical interactions of diagenesis processes.

Mapping species abundance by a spatial zero-inflated Poisson model: a case study in the Wadden Sea, the Netherlands.

PubMed

Lyashevska, Olga; Brus, Dick J; van der Meer, Jaap

2016-01-01

The objective of the study was to provide a general procedure for mapping species abundance when data are zero-inflated and spatially correlated counts. The bivalve species Macoma balthica was observed on a 500×500 m grid in the Dutch part of the Wadden Sea. In total, 66% of the 3451 counts were zeros. A zero-inflated Poisson mixture model was used to relate counts to environmental covariates. Two models were considered, one with relatively fewer covariates (model "small") than the other (model "large"). The models contained two processes: a Bernoulli (species prevalence) and a Poisson (species intensity, when the Bernoulli process predicts presence). The model was used to make predictions for sites where only environmental data are available. Predicted prevalences and intensities show that the model "small" predicts lower mean prevalence and higher mean intensity, than the model "large". Yet, the product of prevalence and intensity, which might be called the unconditional intensity, is very similar. Cross-validation showed that the model "small" performed slightly better, but the difference was small. The proposed methodology might be generally applicable, but is computer intensive.

Zoobenthic biomass limited by phytoplankton abundance: evidence from parallel changes in two long-term data series in the Wadden Sea

NASA Astrophysics Data System (ADS)

Beukema, J. J.; Cadée, G. C.; Dekker, R.

2002-10-01

We address the question of whether year-to-year variability in pelagic algal food supply can explain long-term variability in macrozoobenthic biomass in an estuarine area. Starting in the early 1970s, quantitative data were frequently collected in standardized ways in the western part of the Dutch Wadden Sea on (1) concentrations of phytoplankton species and chlorophyll (and rates of primary production) in the main tidal inlet (Marsdiep) and (2) numerical densities and biomass of macrozoobenthic animals (and growth rates in a few species) in a nearby extensive tidal-flat area (Balgzand). In both data series, the most distinctive feature was a sudden change that took place around 1980, viz. a rather sudden and persisting doubling of concentrations of chlorophyll and algal cells and of primary production rates, as well as of numerical densities and biomass of zoobenthos. From these parallel changes we hypothesise that algal food largely determines the abundance of zoobenthos in the Wadden Sea. The following observations substantiate this hypothesis: (1) the significant correlation between annual mean values of chlorophyll concentration and overall mean numerical density and biomass of zoobenthos (as estimated after an appropriate time lag), (2) the observed limitation of zoobenthic biomass doubling (after the doubling of food supply) to areas with already high biomass values (where food demand was high and food could therefore be in short supply), (3) the limitation of a strong response to changes in food supply to functional groups that are directly dependent on algal food, i.e. suspension and deposit feeders, as opposed to carnivores, (4) the significant correlation between annual growth rates in Macoma balthica and food supply in the growing season, particularly in areas close to the tidal inlet where food concentrations were monitored. Some other factors were identified that could decisively influence zoobenthic abundance locally and/or temporarily. Harsh

The Secret of the Svalbard Sea Ice Barrier

NASA Technical Reports Server (NTRS)

Nghiem, Son V.; Van Woert, Michael L.; Neumann, Gregory

2004-01-01

An elongated sea ice feature called the Svalbard sea ice barrier rapidly formed over an area in the Barents Sea to the east of Svalbard posing navigation hazards. The secret of its formation lies in the bottom bathymetry that governs the distribution of cold Arctic waters masses, which impacts sea ice growth on the water surface.

Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

PubMed Central

Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A.; Leorri, Eduardo

2016-01-01

The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches. PMID:27929122

Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction.

PubMed

Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A; Leorri, Eduardo

2016-12-08

The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

Seasonal variation in parasite infection patterns of marine fish species from the Northern Wadden Sea in relation to interannual temperature fluctuations

NASA Astrophysics Data System (ADS)

Schade, Franziska M.; Raupach, Michael J.; Mathias Wegner, K.

2016-07-01

Marine environmental conditions are naturally changing throughout the year, affecting life cycles of hosts as well as parasites. In particular, water temperature is positively correlated with the development of many parasites and pathogenic bacteria, increasing the risk of infection and diseases during summer. Interannual temperature fluctuations are likely to alter host-parasite interactions, which may result in profound impacts on sensitive ecosystems. In this context we investigated the parasite and bacterial Vibrionaceae communities of four common small fish species (three-spined stickleback Gasterosteus aculeatus, Atlantic herring Clupea harengus, European sprat Sprattus sprattus and lesser sand eel Ammodytes tobianus) in the Northern Wadden Sea over a period of two years. Overall, we found significantly increased relative diversities of infectious species at higher temperature differentials. On the taxon-specific level some macroparasite species (trematodes, nematodes) showed a shift in infection peaks that followed the water temperatures of preceding months, whereas other parasite groups showed no effects of temperature differentials on infection parameters. Our results show that even subtle changes in seasonal temperatures may shift and modify the phenology of parasites as well as opportunistic pathogens that can have far reaching consequences for sensitive ecosystems.

Are thermal barriers "higher" in deep sea turtle nests?

PubMed

Santidrián Tomillo, Pilar; Fonseca, Luis; Paladino, Frank V; Spotila, James R; Oro, Daniel

2017-01-01

Thermal tolerances are affected by the range of temperatures that species encounter in their habitat. Daniel Janzen hypothesized in his "Why mountain passes are higher in the tropics" that temperature gradients were effective barriers to animal movements where climatic uniformity was high. Sea turtles bury their eggs providing some thermal stability that varies with depth. We assessed the relationship between thermal uniformity and thermal tolerance in nests of three species of sea turtles. We considered that barriers were "high" when small thermal changes had comparatively large effects and "low" when the effects were small. Mean temperature was lower and fluctuated less in species that dig deeper nests. Thermal barriers were comparatively "higher" in leatherback turtle (Dermochelys coriacea) nests, which were the deepest, as embryo mortality increased at lower "high" temperatures than in olive ridley (Lepidochelys olivacea) and green turtle (Chelonia mydas) nests. Sea turtles have temperature-dependent sex determination (TSD) and embryo mortality increased as temperature approached the upper end of the transitional range of temperatures (TRT) that produces both sexes (temperature producing 100% female offspring) in leatherback and olive ridley turtles. As thermal barriers are "higher" in some species than in others, the effects of climate warming on embryo mortality is likely to vary among sea turtles. Population resilience to climate warming may also depend on the balance between temperatures that produce female offspring and those that reduce embryo survival.

Planting the SEED: Towards a Spatial Economic Ecological Database for a shared understanding of the Dutch Wadden area

NASA Astrophysics Data System (ADS)

Daams, Michiel N.; Sijtsma, Frans J.

2013-09-01

In this paper we address the characteristics of a publicly accessible Spatial Economic Ecological Database (SEED) and its ability to support a shared understanding among planners and experts of the economy and ecology of the Dutch Wadden area. Theoretical building blocks for a Wadden SEED are discussed. Our SEED contains a comprehensive set of stakeholder validated spatially explicit data on key economic and ecological indicators. These data extend over various spatial scales. Spatial issues relevant to the specification of a Wadden-SEED and its data needs are explored in this paper and illustrated using empirical data for the Dutch Wadden area. The purpose of the SEED is to integrate basic economic and ecologic information in order to support the resolution of specific (policy) questions and to facilitate connections between project level and strategic level in the spatial planning process. Although modest in its ambitions, we will argue that a Wadden SEED can serve as a valuable element in the much debated science-policy interface. A Wadden SEED is valuable since it is a consensus-based common knowledge base on the economy and ecology of an area rife with ecological-economic conflict, including conflict in which scientific information is often challenged and disputed.

Are thermal barriers "higher" in deep sea turtle nests?

PubMed Central

Santidrián Tomillo, Pilar; Fonseca, Luis; Paladino, Frank V.; Spotila, James R.; Oro, Daniel

2017-01-01

Thermal tolerances are affected by the range of temperatures that species encounter in their habitat. Daniel Janzen hypothesized in his “Why mountain passes are higher in the tropics” that temperature gradients were effective barriers to animal movements where climatic uniformity was high. Sea turtles bury their eggs providing some thermal stability that varies with depth. We assessed the relationship between thermal uniformity and thermal tolerance in nests of three species of sea turtles. We considered that barriers were “high” when small thermal changes had comparatively large effects and “low” when the effects were small. Mean temperature was lower and fluctuated less in species that dig deeper nests. Thermal barriers were comparatively “higher” in leatherback turtle (Dermochelys coriacea) nests, which were the deepest, as embryo mortality increased at lower “high” temperatures than in olive ridley (Lepidochelys olivacea) and green turtle (Chelonia mydas) nests. Sea turtles have temperature-dependent sex determination (TSD) and embryo mortality increased as temperature approached the upper end of the transitional range of temperatures (TRT) that produces both sexes (temperature producing 100% female offspring) in leatherback and olive ridley turtles. As thermal barriers are “higher” in some species than in others, the effects of climate warming on embryo mortality is likely to vary among sea turtles. Population resilience to climate warming may also depend on the balance between temperatures that produce female offspring and those that reduce embryo survival. PMID:28545092

Role of physical barriers in the control of sea lamprey (Petromyzon marinus)

USGS Publications Warehouse

Hunn, J.B.; Youngs, W.D.

1980-01-01

Mechanical and electromechanical barriers played a significant role in the initial attempts to control sea lamprey (Petromyzon marinus) populations in the upper Great Lakes. More recently electromechanical weirs have been used to assess the relative abundance of spawning-run sea lampreys in Lake Superior. Development of an integrated control approach to sea lamprey control has stimulated an ongoing research program to define structural and/or velocity criteria that can be used to design barrier dams that block spawning runs of sea lamprey

How the food supply harvestable by waders in the Wadden Sea depends on the variation in energy density, body weight, biomass, burying depth and behaviour of tidal-flat invertebrates

NASA Astrophysics Data System (ADS)

Zwarts, Leo; Wanink, Jan H.

For several reasons, waders in the Wadden Sea face a large seasonal and annual variation in their food supply. Observations on a tidal flat in the Dutch Wadden Sea have shown that: - (1) The average energy density of ten invertebrate prey species varies between 21 and 23 kJ·g -1 AFDW. In Scrobicularia plana and Mya arenaria, but not in Macoma balthica, the energy density is 10% lower in winter than in summer. - (2) Depending on the species, body weights of prey of similar size are 30 to 60% lower in winter than in summer. - (3) The year-to-year fluctuation in standing-crop biomass is larger in some species than in others, the difference depending mainly on the frequency of successful recruitment. The overall biomass of the macrobenthos in winter is half of that in summer, but the timing of the peak biomass differs per species. - (4) The burying depth varies per species: Cerastoderma edule live just beneath the surface, while M. balthica, S. plana, M. arenaria, Arenicola marina and Nereis diversicolor bury more deeply and the majority of these prey live out of reach of the bird's bill. In all six species, burying depth increases with size. There is no seasonal variation in depth of C. edule and M. arenaria, but the four other species live at most shallow depth in early summer and most deeply in midwinter. Burying depths in winter vary from year to year, but are unrelated to temperature. Neither has temperature any effect on depth within months. For knot Calidris canutus feeding on M. balthica, the fluctuation in the accessible fraction was the main source of variation in the biomass of prey that is actually harvestable, i.e. the biomass of prey of suitable size that is accessible. Accordingly, the paper reviews the available data on the temporal variations in accessibility, detectability, ingestibility, digestibility and profitability of prey for waders. Only a small part of the prey is harvestable since many accessible prey are ignored because of their low

Does small-scale vertical distribution of juvenile schooling fish affect prey availability to surface-feeding seabirds in the Wadden Sea?

NASA Astrophysics Data System (ADS)

Dänhardt, Andreas; Becker, Peter H.

2011-02-01

Food availability is a key variable influencing breeding performance and demography of marine top predators. Due to methodological problems, proportionality between fish abundance and availability is often assumed without being explicitly tested. More specifically, better breeding performance of surface-feeding seabirds at times of large prey stocks suggests that prey availability is also a function of prey abundance. Using vertically resolved stow net sampling we tested whether local abundance and length composition of pelagic fish are reliable predictors of the availability of these fish to surface-feeding Common Terns ( Sterna hirundo) breeding in the German Wadden Sea. Prey fish were found to concentrate below the maximum diving depth of the terns. Individuals caught close to the surface were in most cases smaller than conspecifics caught at greater depth. Correlations between fish abundance within and out of reach of the terns appeared to be both species- and site-specific rather than driven by overall fish abundance. Vertical distribution patterns of the terns' main prey fish could be explained as anti-predator behavior, reducing prey availability to the terns. In 2007, when breeding performance was much better than in 2006, herring and whiting were much more abundant, suggesting that overall prey abundance may also increase prey availability in habitats other than those represented by the stow net sampling.

Can barrier islands survive sea level rise? Tidal inlets versus storm overwash

NASA Astrophysics Data System (ADS)

Nienhuis, J.; Lorenzo-Trueba, J.

2017-12-01

Barrier island response to sea level rise depends on their ability to transgress and move sediment to the back barrier, either through flood-tidal delta deposition or via storm overwash. Our understanding of these processes over decadal to centennial timescales, however, is limited and poorly constrained. We have developed a new barrier inlet environment (BRIE) model to better understand the interplay between tidal dynamics, overwash fluxes, and sea-level rise on barrier evolution. The BRIE model combines existing overwash and shoreface formulations [Lorenzo-Trueba and Ashton, 2014] with alongshore sediment transport, inlet stability [Escoffier, 1940], inlet migration and flood-tidal delta deposition [Nienhuis and Ashton, 2016]. Within BRIE, inlets can open, close, migrate, merge with other inlets, and build flood-tidal delta deposits. The model accounts for feedbacks between overwash and inlets through their mutual dependence on barrier geometry. Model results suggest that when flood-tidal delta deposition is sufficiently large, barriers require less storm overwash to transgress and aggrade during sea level rise. In particular in micro-tidal environments with asymmetric wave climates and high alongshore sediment transport, tidal inlets are effective in depositing flood-tidal deltas and constitute the majority of the transgressive sediment flux. Additionally, we show that artificial inlet stabilization (via jetty construction or maintenance dredging) can make barrier islands more vulnerable to sea level rise. Escoffier, F. F. (1940), The Stability of Tidal Inlets, Shore and Beach, 8(4), 114-115. Lorenzo-Trueba, J., and A. D. Ashton (2014), Rollover, drowning, and discontinuous retreat: Distinct modes of barrier response to sea-level rise arising from a simple morphodynamic model, J. Geophys. Res. Earth Surf., 119(4), 779-801, doi:10.1002/2013JF002941. Nienhuis, J. H., and A. D. Ashton (2016), Mechanics and rates of tidal inlet migration: Modeling and application to

Modeling barrier island response to sea-level rise in the Outer Banks, North Carolina

USGS Publications Warehouse

Moore, Laura J.; List, Jeffrey H.; Williams, S. Jeffress; Stolper, David

2007-01-01

An 8500-year Holocene simulation developed in GEOMBEST provides a possible scenario to explain the evolution of barrier coast between Rodanthe and Cape Hatteras, NC. Sensitivity analyses suggest that in the Outer Banks, the rate of sea-level rise is the most important factor in determining how barrier islands evolve. The Holocene simulation provides a basis for future simulations, which suggest that if sea level rises up to 0.88 m by AD 2100, as predicted by the highest estimates of the Intergovernmental Panel on Climate Change, the barrier in the study area may migrate on the order of 2.5 times more rapidly than at present. If sea level rises beyond IPCC predictions to reach 1.4–1.9 m above modern sea level by AD 2100, model results suggest that barrier islands in the Outer Banks may become vulnerable to threshold collapse, disintegrating during storm events, by the end of the next century. Consistent with sensitivity analyses, additional simulations indicate that anthropogenic activities, such as increasing the rate of sediment supply through beach nourishment, will only slightly affect barrier island migration rates and barrier island vulnerability to collapse.

STS-32 Earth observation of the western Coral Sea and the Great Barrier Reef

NASA Technical Reports Server (NTRS)

1990-01-01

STS-32 Earth observation taken onboard Columbia, Orbiter Vehicle (OV) 102, is of the western Coral Sea and the Great Barrier Reef. The scene shows phytoplankton or algal bloom in the northwest Coral Sea. The western Coral Sea and the Great Barrier Reef waters offshore Queensland, Australia are the sites of some of the larger concentrations or 'blooms' of phytoplankton and algae in the open ocean. In the instance illustrated here, the leading edge of a probable concentration of algae or phytoplankton is seen as a light irregular line and sheen between the offshore Great Barrier Reef and the Queensland coast. Previous phytoplankton concentrations in this area have been reported by ships at sea as having formed floating mats as thick as two meters.

Annual variation in reproductive success and biomass of the major macrozoobenthic species living in a tidal flat area of the Wadden Sea

NASA Astrophysics Data System (ADS)

Beukema, J. J.

Annual variation in recruitment and biomass was studied during 13 years for the 5 species contributing most to total zoobenthic biomass in a tidal flat area in the westernmost part of the Wadden Sea. In all of these species annual biomass values tended to be more stable than numbers of recruits. In Cerastoderma edule and in Mytilus edulis recruitment variability was high, and was passed on almost completely to biomass, probably as a consequence of rapid juvenile growth and a high mortality, also in the adult stage, leaving few year-classes in the population. In Arenicola marina and in Mya arenaria biomass values varied much less than recruit numbers. Both species showed a low adult mortality rate with many year-classes present in the population, holding many old and heavy specimens that dominated biomass. Macoma balathica took an intermediate position in these respects. Recruitment was relatively stable in Arenicola and was probably controlled by the high numbers of adults. Recruitment variability was fairly low too in Macoma, but in this species juvenile mortality appeared to be directly related to their own density. Successful and poor years for recruitment were roughly the same for the 4 bivalve species. Particularly heavy spatfall was found during the summer following the severe 1978-1979 winter. Such synchronized recruitment does not fully add to variability in annual biomass values as the time needed for the recruted cohorts to reach maximum biomass values differs greatly between most of the high-biomass species.

Carbon, nitrogen and phosphorus dynamics in nine sub-systems of the Sylt-Rømø Bight ecosystem, German Wadden Sea

NASA Astrophysics Data System (ADS)

Baird, Dan; Asmus, Harald; Asmus, Ragnhild

2011-01-01

Flow networks of nine sub-systems consisting of 59 components each of the Sylt-Rømø Bight, German Wadden Sea, were constructed depicting the standing stocks and flows of material and energy within and between the sub-systems. Carbon, nitrogen and phosphorous were used as currencies for each sub-system, thus resulting in 27 network models, which were analyzed by ecological network analytical protocols. Results show substantial variability in the dynamics of these elements within and between the nine sub-systems, which differ in habitat structure, species diversity and in the standing stocks of their constituent living and non-living components. The relationship between the biodiversity and selected information indices and ratios, derived from ecological network analysis, of individual sub-systems is variable and differ substantially between them. Ecosystem properties such as the structure and magnitude of the recycling of these elements, number of cycles, and total sub-system activity were calculated and discussed, highlighting the differences between and complexity of the flow of C, N and P in a coastal marine ecosystem. The average number of cycles increase from 179 for C, to 16,923 and 20,580 for N and P respectively, while the average amount of recycled material, as measured by the Finn Cycling Index (FCI), increase from 17% for C, to 52% for P and to 61% for N. The number of cycles and the FCI vary considerably between the sub-systems for the different elements. The largest number of cycles of all three elements was observed in the muddy sand flat sub-system, but the highest FCIs were computed for both C (32%) and N (85%) in the Arenicola Flats, and in sparse Zostera noltii sea grass beds for P (67%). Indices reflecting on the growth, organization and resilience of the sub-systems also showed considerable variability between and within the inter-tidal ecosystems in the Bight. Indices such as, for example, the relative ascendency ratios increase on average

Benthic primary producers are key to sustain the Wadden Sea food web: stable carbon isotope analysis at landscape scale.

PubMed

Christianen, M J A; Middelburg, J J; Holthuijsen, S J; Jouta, J; Compton, T J; van der Heide, T; Piersma, T; Sinninghe Damsté, J S; van der Veer, H W; Schouten, S; Olff, H

2017-06-01

Coastal food webs can be supported by local benthic or pelagic primary producers and by the import of organic matter. Distinguishing between these energy sources is essential for our understanding of ecosystem functioning. However, the relative contribution of these components to the food web at the landscape scale is often unclear, as many studies lack good taxonomic and spatial resolution across large areas. Here, using stable carbon isotopes, we report on the primary carbon sources for consumers and their spatial variability across one of the world's largest intertidal ecosystems (Dutch Wadden Sea; 1460 km 2 intertidal surface area), at an exceptionally high taxonomic (178 species) and spatial resolution (9,165 samples from 839 locations). The absence of overlap in δ 13 C values between consumers and terrestrial organic matter suggests that benthic and pelagic producers dominate carbon input into this food web. In combination with the consistent enrichment of benthic primary producers (δ 13 C -16.3‰) relative to pelagic primary producers (δ 13 C -18.8) across the landscape, this allowed the use of a two-food-source isotope-mixing model. This spatially resolved modelling revealed that benthic primary producers (microphytobenthos) are the most important energy source for the majority of consumers at higher trophic levels (worms, molluscs, crustaceans, fish, and birds), and thus to the whole food web. In addition, we found large spatial heterogeneity in the δ 13 C values of benthic primary producers (δ 13 C -19.2 to -11.5‰) and primary consumers (δ 13 C -25.5 to -9.9‰), emphasizing the need for spatially explicit sampling of benthic and pelagic primary producers in coastal ecosystems. Our findings have important implications for our understanding of the functioning of ecological networks and for the management of coastal ecosystems. © 2017 by the Ecological Society of America.

On the dynamics of compound bedforms in high-energy tidal channels: field observations in the German Bight and the Danish Wadden Sea

NASA Astrophysics Data System (ADS)

Ernstsen, Verner B.; Winter, Christian; Becker, Marius; Bartholdy, Jesper

2010-05-01

Tidal inlets are a common feature along much of the world's coastlines. They interrupt the alongshore continuity of shoreline processes, and by being exposed to both wave and current forcing, tidal inlets belong to the morphologically most dynamic and complex coastal systems on Earth. The tidal channels in these inlets are characterized by high flow velocities and, accordingly, the channel beds are typically sandy and covered with bedforms. The bedform fields in nature are often complex systems with larger primary-bedforms superimposed by smaller secondary-bedforms (cf. Bartholdy et al., 2002). There is a considerable amount of detailed field investigations on the dynamics of primary-bedforms at various temporal scales, ranging from short- to long-term tide-related cycles to flood hydrographs to seasonality. However, Julien et al. (2002) stated that a composite analysis of primary- and secondary-bedforms is recommended for future studies on resistance to flow. Such knowledge on the behaviour of compound bedforms is still deficient. In this study, we combine the findings on the dynamics of primary- and secondary-bedform height from detailed field investigations carried out in two high-energy tidal channels during 2007 and 2008: the Knudedyb tidal inlet channel in the Danish Wadden Sea and the Innenjade tidal channel in the Jade Bay, German Bight (both survey areas being ebb-dominated). We provide process-based explanations of the bedform behaviour and present a conceptual model of compound bedform dynamics. The conducted field investigations comprised repetitive, simultaneous measurements of high-resolution swath bathymetry (using a multibeam echosounder system) and flow velocity (using an acoustic Doppler current profiler) in combination with detailed spatial mapping of bed material characteristics (from grab sampling of bed material). For an objective and discrete analysis of primary- and secondary-bedforms a modified version of the bedform tracking tool

Modeling Holocene Barrier Island Morphodynamics and Potential Future Response to Sea- Level Rise, Outer Banks, North Carolina

NASA Astrophysics Data System (ADS)

Moore, L. J.; List, J. H.; Williams, S. J.; Stolper, D.

2006-12-01

A morphological-behavior model, GEOMBEST, which simulates the evolution of coastal morphology and stratigraphy resulting from changes in sea level and sediment supply provides insight into how barriers evolve over time scales ranging from decades to millenia. The model is based upon behavior rules originating from "Bruun rule" concepts, with additional parameters to allow simulation of more complex real-world scenarios. Morphological evolution in the model is driven by disequilibrium between the shoreface and a user-specified theoretical equilibrium profile that maintains its vertical position relative to sea level. As sea level continues rising to an estimated 48 cm above current MSL by AD 2100 (IPCC 2001) and hurricanes of potentially greater intensity impact the coast, barrier islands will respond either by transgressing across underlying strata or by disintegrating and ultimately submerging. Recent studies suggest that some barriers along the U.S. East Coast will break up and become submerged within decades. Other studies show that barriers in Louisiana have already submerged while others are in the process of narrowing in place and submerging. Several factors determine barrier island response to sea-level rise. These include initial topography and morphology of the barrier, underlying geologic framework, availability and supply of sediment, rate of sea-level rise, frequency and intensity of coastal storms, and anthropogenic modifications to the coast. Sensitivity analyses conducted in GEOMBEST suggest that of these factors, barrier-island response is most sensitive to the rate of sea-level rise. The Holocene evolution of the Outer Banks and potential future responses to sea-level rise are explored for a 25-km stretch of coast between Rodanthe and Cape Hatteras, NC using GEOMBEST. An 8500-year hindcast simulation for the study area reproduces closely the morphology and stratigraphy of the modern barrier with approximately 5 x 109 m3 excavated from the

Interannual variability of mean sea level and its sensitivity to wind climate in an inter-tidal basin

NASA Astrophysics Data System (ADS)

Gerkema, Theo; Duran-Matute, Matias

2017-12-01

The relationship between the annual wind records from a weather station and annual mean sea level in an inter-tidal basin, the Dutch Wadden Sea, is examined. Recent, homogeneous wind records are used, covering the past 2 decades. It is demonstrated that even such a relatively short record is sufficient for finding a convincing relationship. The interannual variability of mean sea level is largely explained by the west-east component of the net wind energy, with some further improvement if one also includes the south-north component and the annual mean atmospheric pressure. Using measured data from a weather station is found to give a slight improvement over reanalysis data, but for both the correlation between annual mean sea level and wind energy in the west-east direction is high. For different tide gauge stations in the Dutch Wadden Sea and along the coast, we find the same qualitative characteristics, but even within this small region, different locations show a different sensitivity of annual mean sea level to wind direction. Correcting observed values of annual mean level for meteorological factors reduces the margin of error (expressed as 95 % confidence interval) by more than a factor of 4 in the trends of the 20-year sea level record. Supplementary data from a numerical hydrodynamical model are used to illustrate the regional variability in annual mean sea level and its interannual variability at a high spatial resolution. This study implies that climatic changes in the strength of winds from a specific direction may affect local annual mean sea level quite significantly.

Complexities in barrier island response to sea level rise: Insights from numerical model experiments, North Carolina Outer Banks

USGS Publications Warehouse

Moore, Laura J.; List, Jeffrey H.; Williams, S. Jeffress; Stolper, David

2010-01-01

Using a morphological-behavior model to conduct sensitivity experiments, we investigate the sea level rise response of a complex coastal environment to changes in a variety of factors. Experiments reveal that substrate composition, followed in rank order by substrate slope, sea level rise rate, and sediment supply rate, are the most important factors in determining barrier island response to sea level rise. We find that geomorphic threshold crossing, defined as a change in state (e.g., from landward migrating to drowning) that is irreversible over decadal to millennial time scales, is most likely to occur in muddy coastal systems where the combination of substrate composition, depth-dependent limitations on shoreface response rates, and substrate erodibility may prevent sand from being liberated rapidly enough, or in sufficient quantity, to maintain a subaerial barrier. Analyses indicate that factors affecting sediment availability such as low substrate sand proportions and high sediment loss rates cause a barrier to migrate landward along a trajectory having a lower slope than average barrier island slope, thereby defining an “effective” barrier island slope. Other factors being equal, such barriers will tend to be smaller and associated with a more deeply incised shoreface, thereby requiring less migration per sea level rise increment to liberate sufficient sand to maintain subaerial exposure than larger, less incised barriers. As a result, the evolution of larger/less incised barriers is more likely to be limited by shoreface erosion rates or substrate erodibility making them more prone to disintegration related to increasing sea level rise rates than smaller/more incised barriers. Thus, the small/deeply incised North Carolina barriers are likely to persist in the near term (although their long-term fate is less certain because of the low substrate slopes that will soon be encountered). In aggregate, results point to the importance of system history (e

Possible causes for growth variability and summer growth reduction in juvenile plaice Pleuronectes platessa L. in the western Dutch Wadden Sea

NASA Astrophysics Data System (ADS)

van der Veer, Henk W.; Jung, Alexa Sarina; Freitas, Vânia; Philippart, Catharina J. M.; Witte, Johannes IJ.

2016-05-01

Growth variability within individuals and among groups and locations and the phenomenon of summer growth reduction has been described for juvenile flatfish in a variety of European coastal areas whereby the underlying causes still remain elusive. Potential mechanisms were tested for juvenile plaice Pleuronectes platessa L. in the western Dutch Wadden Sea, by analysing published and unpublished information from long-term investigations (1986-present). Growth variability did occur and could be explained by differences induced by environmental variability (water temperature), and by non-genetic irreversible adaptation and sex. Dynamic Energy Budget analysis indicated that especially sexually-dimorphic growth in combination with variability in sex ratio could explain most of the variability in growth and the increase in the range of the size of individuals within the population over time. Summer growth reduction was not only observed among 0-group plaice in the intertidal, but also in the subtidal and tidal gullies as well as among I- and II-group plaice. Intraspecific competition for food was not detected but some support for interspecific competition with other predators was found. Also resource competition (due to crowding) with the other abundant epibenthic species (0-, I- and II-group flounder Platichthys flesus; the brown shrimp Crangon crangon; the shore crab Carcinus maenas; the goby species Pomatoschistus minutus and Pomatoschistus microps) could not explain the summer growth reduction. The observed growth reduction coincided with a decrease in stomach content, especially of regenerating body parts of benthic prey items. It is hypothesised that macrozoobenthos becomes less active after the spring phytoplankton bloom, reducing prey availability for juvenile plaice in summer, causing a reduction in food intake and hence in growth.

STS-32 Earth observation of the western Coral Sea and the Great Barrier Reef

NASA Image and Video Library

1990-01-20

STS032-520-014 (9-20 Jan. 1990) --- STS-32 astronauts took this 70mm scene showing phytoplankton oralgal bloom in the northwest Coral Sea. The Western Coral Sea and the Great Barrier Reef waters offshore Queensland, Australia are the sites of some of the larger concentrations or "blooms" of phytoplankton and algae in the open ocean. In the instance illustrated here, the leading edge of a probable concentration of algae or phytoplankton is seen as a light irregular line and sheen between the offshore Great Barrier Reef and the Queensland coast. Previous phytoplankton concentrations in this area have been reported by ships at sea as having formed floating mats as thick as two meters. This picture was used by the STS-32 astronauts at their Jan. 30, 1990 post-flight press conference.

Barriers to and enablers of evidence-based practice in perinatal care in the SEA-ORCHID project.

PubMed

Turner, Tari; Short, Jacki

2013-08-01

The South-East Asia Optimising Reproductive and Child Health in Developing Countries (SEA-ORCHID) project aimed to improve health outcomes for mothers and babies in nine hospitals in South-East Asia by supporting evidence-based perinatal health care. In this research, we aimed to identify and explore the factors that may have acted as barriers to or enablers of evidence-based practice change at each of the hospitals. During the final 6 months of the intervention phase of the project, semi-structured, face-to-face interviews were undertaken with 179 nurses, midwives and doctors from the maternal and neonatal departments at each of the nine participating South-East Asian hospitals. The interviews identified several factors that participants believed had a substantial impact on the effectiveness of the SEA-ORCHID intervention. These included knowledge, skills, hierarchy, multidisciplinarity and leadership, beliefs about consequences, resources, and the nature of the behaviours. The success of the SEA-ORCHID intervention in improving practice may reflect the extent to which tailored strategies were effective in overcoming these barriers. Effective interventions to align practice with evidence rely on identifying and addressing barriers to practice change. The barriers identified in this study may be useful for those designing similar clinical practice improvement projects, as well as for continued efforts to improve practice in the SEA-ORCHID hospitals. © 2011 John Wiley & Sons Ltd.

Natural and Human-Induced Variability in Barrier-Island Response to Sea Level Rise

NASA Astrophysics Data System (ADS)

Miselis, Jennifer L.; Lorenzo-Trueba, Jorge

2017-12-01

Storm-driven sediment fluxes onto and behind barrier islands help coastal barrier systems keep pace with sea level rise (SLR). Understanding what controls cross-shore sediment flux magnitudes is critical for making accurate forecasts of barrier response to increased SLR rates. Here, using an existing morphodynamic model for barrier island evolution, observations are used to constrain model parameters and explore potential variability in future barrier behavior. Using modeled drowning outcomes as a proxy for vulnerability to SLR, 0%, 28%, and 100% of the barrier is vulnerable to SLR rates of 4, 7, and 10 mm/yr, respectively. When only overwash fluxes are increased in the model, drowning vulnerability increases for the same rates of SLR, suggesting that future increases in storminess may increase island vulnerability particularly where sediment resources are limited. Developed sites are more vulnerable to SLR, indicating that anthropogenic changes to overwash fluxes and estuary depths could profoundly affect future barrier response to SLR.

Natural and human-induced variability in barrier-island response to sea level rise

USGS Publications Warehouse

Miselis, Jennifer L.; Lorenzo-Trueba, Jorge

2017-01-01

Storm-driven sediment fluxes onto and behind barrier islands help coastal barrier systems keep pace with sea level rise (SLR). Understanding what controls cross-shore sediment flux magnitudes is critical for making accurate forecasts of barrier response to increased SLR rates. Here, using an existing morphodynamic model for barrier island evolution, observations are used to constrain model parameters and explore potential variability in future barrier behavior. Using modeled drowning outcomes as a proxy for vulnerability to SLR, 0%, 28%, and 100% of the barrier is vulnerable to SLR rates of 4, 7, and 10 mm/yr, respectively. When only overwash fluxes are increased in the model, drowning vulnerability increases for the same rates of SLR, suggesting that future increases in storminess may increase island vulnerability particularly where sediment resources are limited. Developed sites are more vulnerable to SLR, indicating that anthropogenic changes to overwash fluxes and estuary depths could profoundly affect future barrier response to SLR.

Barriers on the brink? The complex intertwined roles of geologic framework, sediment availability and sea-level rise in island evolution

USGS Publications Warehouse

Moore, Laura; List, Jeffrey H.; Williams, S. Jeffress; Patsch, Kiki; Rosati, Julie D.; Wang, Ping; Roberts, Tiffany M.

2011-01-01

Sensitivity experiments in the North Carolina Outer Banks (OBX) have previously revealed that substrate sand proportion, followed by substrate slope, sea-level rise rate and sediment-loss rate are the most important factors in determining how barrier islands respond to sea-level rise. High sediment-loss rates and low substrate sand proportions cause barriers to be smaller and more deeply incised. Thus, as sea level rise rates increase, more deeply incised barriers do not need to migrate as far landward as larger, less-incised barriers to liberate sand from the shoreface. However, if the combination of sand losses and substrate sand proportions requires a barrier to migrate landward faster than the shoreface can erode to replenish losses, a barrier will change state and begin to disintegrate. Because the substrate of the OBXis sand-rich, these barriers are likely to persist in the near-term. In contrast, model simulations for the Chandeleur Islands, Louisiana suggest sediment loss rates are too high and/or substrate sand proportions are too low to be matched by liberation of shoreface sand. These simulations further suggest that a state change, from a landward-migrating barrier system to a subaqueous shoal complex, is either already underway or imminent.

Effects of sea-level rise on barrier island groundwater system dynamics: ecohydrological implications

USGS Publications Warehouse

Masterson, John P.; Fienen, Michael N.; Thieler, E. Robert; Gesch, Dean B.; Gutierrez, Benjamin T.; Plant, Nathaniel G.

2014-01-01

We used a numerical model to investigate how a barrier island groundwater system responds to increases of up to 60 cm in sea level. We found that a sea-level rise of 20 cm leads to substantial changes in the depth of the water table and the extent and depth of saltwater intrusion, which are key determinants in the establishment, distribution and succession of vegetation assemblages and habitat suitability in barrier islands ecosystems. In our simulations, increases in water-table height in areas with a shallow depth to water (or thin vadose zone) resulted in extensive groundwater inundation of land surface and a thinning of the underlying freshwater lens. We demonstrated the interdependence of the groundwater response to island morphology by evaluating changes at three sites. This interdependence can have a profound effect on ecosystem composition in these fragile coastal landscapes under long-term changing climatic conditions.

Barrier Island Sensitivity to Sea-Level Rise: Insights from Numerical Model Experiments, North Carolina Outer Banks and Chandeleur Islands, LA U.S.A

NASA Astrophysics Data System (ADS)

Moore, L. J.; List, J. H.; Williams, S.; Patsch, K.

2009-12-01

As dynamic and low-lying coastal landforms, barrier islands are especially vulnerable to sea level rise, changes in sediment supply and coastal storms. Changes in these factors may ultimately result in new conditions that are sufficiently different from present to cause a shift in equilibrium state from landward-migrating to submerging, i.e., a threshold crossing. Because the loss of barrier islands would be extremely disruptive of human activities, an understanding of how barrier islands evolve under conditions of rising sea level is vital to the development of wise coastal management practices. To advance understanding of barrier island response to changing conditions, we apply the morphological-behavior model GEOMBEST (GEOmorphic Model of Barrier and EStuarine Translations; Stolper et al., 2005, Moore et al., 2007 and Moore et al., accepted pending minor revisions) to field sites in the North Carolina Outer Banks and the Chandeleur Islands of southeastern Louisiana. Sensitivity analyses reveal that, in general, substrate sand proportion, substrate slope, sea-level rise rate and sediment-supply rate are the most important factors in determining barrier island response to sea-level rise while shoreface erosion rates, substrate erodibility, and shoreface depth are often less important. More specifically, substrate composition appears to be the most important factor in muddy coastal environments, such as the Chandeleur Islands, where model results suggest that a threshold crossing may occur on the order of decades to a century from present, while the other three factors appear to be most important in North Carolina and other similar environments. When substrate sand proportions are low and/or sediment-loss rates are high, shoreface erosion rate and substrate erodibility may become important in limiting the rate at which sand can be liberated from the substrate, thereby increasing barrier island vulnerability to threshold crossing. Barrier system history (e

The potential for sea-level-rise-induced barrier island loss: Insights from the Chandeleur Islands, Louisiana, USA

USGS Publications Warehouse

Moore, Laura J.; Patsch, Kiki; List, Jeffrey H.; Williams, S. Jeffress

2014-01-01

As sea level rises and hurricanes become more intense, barrier islands around the world become increasingly vulnerable to conversion from self-sustaining migrating landforms to submerging or subaqueous sand bodies. To explore the mechanism by which such state changes occur and to assess the factors leading to island disintegration, we develop a suite of numerical simulations for the Chandeleur Islands in Louisiana, U.S.A., which appear to be on the verge of this transition. Our results suggest that the Chandeleurs are likely poised to change state, leading to their demise, within decades depending on future storm history. Contributing factors include high rates of relative sea level rise, limited sediment supply, muddy substrate, current island position relative to former Mississippi River distributary channels, and the effects of changes in island morphology on sediment transport pathways. Although deltaic barrier islands are most sensitive to disintegration because of their muddy substrate, the importance of relative sea level rise rate in determining the timing of threshold crossing suggests that the conceptual models for deltaic barrier island formation and disintegration may apply more broadly in the future.

Barriers to and opportunities for landward migration of coastal wetlands with sea-level rise

USGS Publications Warehouse

Enwright, Nicholas M.; Griffith, Kereen T.; Osland, Michael J.

2016-01-01

In the 21st century, accelerated sea-level rise and continued coastal development are expected to greatly alter coastal landscapes across the globe. Historically, many coastal ecosystems have responded to sea-level fluctuations via horizontal and vertical movement on the landscape. However, anthropogenic activities, including urbanization and the construction of flood-prevention infrastructure, can produce barriers that impede ecosystem migration. Here we show where tidal saline wetlands have the potential to migrate landward along the northern Gulf of Mexico coast, one of the most sea-level rise sensitive and wetland-rich regions of the world. Our findings can be used to identify migration corridors and develop sea-level rise adaptation strategies to help ensure the continued availability of wetland-associated ecosystem goods and services.

Habitat management affects soil chemistry and allochthonous organic inputs mediating microbial structure and exo-enzyme activity in Wadden Sea salt-marsh soils

NASA Astrophysics Data System (ADS)

Mueller, Peter; Granse, Dirk; Thi Do, Hai; Weingartner, Magdalena; Nolte, Stefanie; Hoth, Stefan; Jensen, Kai

2016-04-01

The Wadden Sea (WS) region is Europe's largest wetland and home to approximately 20% of its salt marsh area. Mainland salt marshes of the WS are anthropogenically influenced systems and have traditionally been used for livestock grazing in wide parts. After foundation of WS National Parks in the late 1980s and early 1990s, artificial drainage has been abandoned; however, livestock grazing is still common in many areas of the National Parks and is under ongoing discussion as a habitat-management practice. While studies so far focused on effects of livestock grazing on biodiversity, little is known about how biogeochemical processes, element cycling, and particularly carbon sequestration are affected. Here, we present data from a recent field study focusing on grazing effects on soil properties, microbial exo-enzyme activity, microbial abundance and structure. Exo-enzyme activity was studied conducting digestive enzyme assays for various enzymes involved in C- and N cycling. Microbial abundance and structure was assessed measuring specific gene abundance of fungi and bacteria using quantitative PCR. Soil compaction induced by grazing led to higher bulk density and decreases in soil redox (Δ >100 mV). Soil pH was significantly lower in grazed parts. Further, the proportion of allochthonous organic matter (marine input) was significantly smaller in grazed vs. ungrazed sites, likely caused by a higher sediment trapping capacity of the taller vegetation in the ungrazed sites. Grazing induced changes in bulk density, pH and redox resulted in reduced activity of enzymes involved in microbial C acquisition; however, there was no grazing effect on enzymes involved in N acquisition. While changes in pH, bulk density or redox did not affect microbial abundance and structure, the relative amount of marine organic matter significantly reduced the relative abundance of fungi (F:B ratio). We conclude that livestock grazing directly affects microbial exo-enzyme activity, thus

Nitrate consumption in sediments of the German Bight (North Sea)

NASA Astrophysics Data System (ADS)

Neumann, Andreas; van Beusekom, Justus E. E.; Holtappels, Moritz; Emeis, Kay-Christian

2017-09-01

Denitrification on continental margins and in coastal sediments is a major sink of reactive N in the present nitrogen cycle and a major ecosystem service of eutrophied coastal waters. We analyzed the nitrate removal in surface sediments of the Elbe estuary, Wadden Sea, and adjacent German Bight (SE North Sea) during two seasons (spring and summer) along a eutrophication gradient ranging from a high riverine nitrate concentrations at the Elbe Estuary to offshore areas with low nitrate concentrations. The gradient encompassed the full range of sediment types and organic carbon concentrations of the southern North Sea. Based on nitrate penetration depth and concentration gradient in the porewater we estimated benthic nitrate consumption rates assuming either diffusive transport in cohesive sediments or advective transport in permeable sediments. For the latter we derived a mechanistic model of porewater flow. During the peak nitrate discharge of the river Elbe in March, the highest rates of diffusive nitrate uptake were observed in muddy sediments (up to 2.8 mmol m- 2 d- 1). The highest advective uptake rate in that period was observed in permeable sediment and was tenfold higher (up to 32 mmol m- 2 d- 1). The intensity of both diffusive and advective nitrate consumption dropped with the nitrate availability and thus decreased from the Elbe estuary towards offshore stations, and were further decreased during late summer (minimum nitrate discharge) compared to late winter (maximum nitrate discharge). In summary, our rate measurements indicate that the permeable sediment accounts for up to 90% of the total benthic reactive nitrogen consumption in the study area due to the high efficiency of advective nitrate transport into permeable sediment. Extrapolating the averaged nitrate consumption of different sediment classes to the areas of Elbe Estuary, Wadden Sea and eastern German Bight amounts to an N-loss of 3.1 ∗ 106 mol N d- 1 from impermeable, diffusion

The possible physical barrier and coastal dispersal strategy for Japanese grenadier anchovy, Coilia nasus in the East China Sea and Yellow Sea: evidence from AFLP markers.

PubMed

Han, Zhi-Qiang; Han, Gang; Wang, Zhi-Yong; Gao, Tian-Xiang

2015-02-03

In order to ascertain the taxonomic status of the Ariake Sea population of Japanese grenadier anchovy, Coilia nasus, and assess the contemporary possible genetic barrier between the west and east coastal waters of the East China Sea, we used amplified fragment length polymorphism (AFLP) markers to detect the genetic structure of C. nasus, in the East China Sea and Yellow Sea. Eighty-one individuals of C. nasus were collected from five locations and 12 individuals of Coilia mystus were sampled from the Yangtze River Estuary. A total of 371 loci were detected by five primer combinations, 310 of which were polymorphic (83.56%). Analysis of molecular variation (AMOVA) and pairwise fixation index (FST) revealed significant genetic differentiation among five samples, indicating limited gene flow among populations. The dendrogram for populations by neighbor-joining (NJ) cluster analysis provided evidence of a clear relationship between genetic and geographic patterns, supporting significant genetic differentiation between China coastal populations and Ariake Sea populations. Compared to the genetic divergence between C. nasus and C. mystus, the level of genetic differentiation between China and the Ariake Sea populations of C. nasus is obvious below the species level, indicating isolated populations of C. nasus in the Ariake Sea. Isolation by distance analysis revealed that direct ocean distance with deep-water at the continental slope and high salinity between west and east coastal waters of the East China Sea served as major physical barrier to C. nasus, supporting the coastal dispersal pattern in this estuarine species, and rejecting offshore dispersal strategy.

Biological effect of low-head sea lamprey barriers: Designs for extensive surveys and the value of incorporating intensive process-oriented research

USGS Publications Warehouse

Hayes, D.B.; Baylis, J.R.; Carl, L.M.; Dodd, H.R.; Goldstein, J.D.; McLaughlin, R.L.; Noakes, D.L.G.; Porto, L.M.

2003-01-01

Four sampling designs for quantifying the effect of low-head sea lamprey (Petromyzon marinus) barriers on fish communities were evaluated, and the contribution of process-oriented research to the overall confidence of results obtained was discussed. The designs include: (1) sample barrier streams post-construction; (2) sample barrier and reference streams post-construction; (3) sample barrier streams pre- and post-construction; and (4) sample barrier and reference streams pre- and post-construction. In the statistical literature, the principal basis for comparison of sampling designs is generally the precision achieved by each design. In addition to precision, designs should be compared based on the interpretability of results and on the scale to which the results apply. Using data collected in a broad survey of streams with and without sea lamprey barriers, some of the tradeoffs that occur among precision, scale, and interpretability are illustrated. Although circumstances such as funding and availability of pre-construction data may limit which design can be implemented, a pre/post-construction design including barrier and reference streams provides the most meaningful information for use in barrier management decisions. Where it is not feasible to obtain pre-construction data, a design including reference streams is important to maintain the interpretability of results. Regardless of the design used, process-oriented research provides a framework for interpreting results obtained in broad surveys. As such, information from both extensive surveys and intensive process-oriented research provides the best basis for fishery management actions, and gives researchers and managers the most confidence in the conclusions reached regarding the effects of sea lamprey barriers.

Comparison of two feature selection methods for the separability analysis of intertidal sediments with spectrometric datasets in the German Wadden Sea

NASA Astrophysics Data System (ADS)

Jung, Richard; Ehlers, Manfred

2016-10-01

The spectral features of intertidal sediments are all influenced by the same biophysical properties, such as water, salinity, grain size or vegetation and therefore they are hard to separate by using only multispectral sensors. This could be shown by a previous study of Jung et al. (2015). A more detailed analysis of their characteristic spectral feature has to be carried out to understand the differences and similarities. Spectrometry data (i.e., hyperspectral sensors), for instance, have the opportunity to measure the reflection of the landscape as a continuous spectral pattern for each pixel of an image built from dozen to hundreds of narrow spectral bands. This reveals a high potential to measure unique spectral responses of different ecological conditions (Hennig et al., 2007). In this context, this study uses spectrometric datasets to distinguish between 14 different sediment classes obtained from a study area in the German Wadden Sea. A new feature selection method is proposed (Jeffries-Matusita distance bases feature selection; JMDFS), which uses the Euclidean distance to eliminate the wavelengths with the most similar reflectance values in an iterative process. Subsequent to each iteration, the separation capability is estimated by the Jeffries-Matusita distance (JMD). Two classes can be separated if the JMD is greater than 1.9 and if less than four wavelengths remain, no separation can be assumed. The results of the JMDFS are compared with a state-of-the-art feature selection method called ReliefF. Both methods showed the ability to improve the separation by achieving overall accuracies greater than 82%. The accuracies are 4%-13% better than the results with all wavelengths applied. The number of remaining wavelengths is very diverse and ranges from 14 to 213 of 703. The advantage of JMDFS compared with ReliefF is clearly the processing time. ReliefF needs 30 min for one temporary result. It is necessary to repeat the process several times and to average

Test of a non-physical barrier consisting of light, sound, and bubble screen to block upstream movement of sea lamprey in an experimental raceway

USGS Publications Warehouse

Miehls, Scott M.; Johnson, Nicholas S.; Hrodey, Pete J.

2017-01-01

Control of the invasive Sea Lamprey Petromyzon marinus is critical for management of commercial and recreational fisheries in the Laurentian Great Lakes. Use of physical barriers to block Sea Lampreys from spawning habitat is a major component of the control program. However, the resulting interruption of natural streamflow and blockage of nontarget species present substantial challenges. Development of an effective nonphysical barrier would aid the control of Sea Lampreys by eliminating their access to spawning locations while maintaining natural streamflow. We tested the effect of a nonphysical barrier consisting of strobe lights, low-frequency sound, and a bubble screen on the movement of Sea Lampreys in an experimental raceway designed as a two-choice maze with a single main channel fed by two identical inflow channels (one control and one blocked). Sea Lampreys were more likely to move upstream during trials when the strobe light and low-frequency sound were active compared with control trials and trials using the bubble screen alone. For those Sea Lampreys that did move upstream to the confluence of inflow channels, no combination of stimuli or any individual stimulus significantly influenced the likelihood that Sea Lampreys would enter the blocked inflow channel, enter the control channel, or return downstream.

Barrier island response to an elevated sea-level anomaly: Onslow Beach, North Carolina, USA

NASA Astrophysics Data System (ADS)

Theuerkauf, E. J.; Rodriguez, A. B.; Fegley, S. R.; Luettich, R.

2012-12-01

Variations in sea level over time scales ranging from hours to millennia influence coastal processes and evolution. At annual time scales, elevated sea-level anomalies produce coastal flooding and promote beach erosion. This study examines the coastal response of Onslow Beach, North Carolina to the summer 2009 East Coast sea-level anomaly. Onslow Beach is a 12-km-long wave-dominated barrier island with highly variable along-barrier morphology. The transgressive southern portion of the island is characterized by a narrow beach, low dunes, and multiple washover fans, while the regressive northern portion is characterized by a wide beach and continuous tall dunes. Hourly tide gauge data from adjacent NOAA stations (Beaufort and Wrightsville Beach) are used to determine the timing and extent of elevated water levels. The seasonal and longer term trends (relative sea level rise) are removed from both of the water level series and the sea-level anomaly is represented by a large residual between the observed and predicted water levels. Beach response is quantified using terrestrial laser scanning for morphology and from geoprobe cores to determine the maximum depth of erosion (MDOE). The mean high water (MHW) shoreline and dune toe are digitized from digital elevation models derived from the laser scans and analyzed using the Digital Shoreline Analysis System (DSAS). Landward (negative) movement of these contacts indicates erosion. Wave data collected from an Acoustic Wave and Current Meter (AWAC) located offshore of the southern end of Onslow Beach is used to characterize the wave regime throughout the study. Water level is elevated in the tide gauge data from June 2009 to March 2010. This sea-level anomaly corresponds with an increase in the maximum depth of erosion between 2009 and 2010. Landward movement of the MHW shoreline and the dunetoe increased during the period between September 2009 and May 2010 indicating an increase in beach erosion during the sea

Lower Mesophotic Coral Communities (60-125 m Depth) of the Northern Great Barrier Reef and Coral Sea

PubMed Central

Englebert, Norbert; Bongaerts, Pim; Muir, Paul R.; Hay, Kyra B.; Pichon, Michel; Hoegh-Guldberg, Ove

2017-01-01

Mesophotic coral ecosystems in the Indo-Pacific remain relatively unexplored, particularly at lower mesophotic depths (≥60 m), despite their potentially large spatial extent. Here, we used a remotely operated vehicle to conduct a qualitative assessment of the zooxanthellate coral community at lower mesophotic depths (60–125 m) at 10 different locations in the Great Barrier Reef Marine Park and the Coral Sea Commonwealth Marine Reserve. Lower mesophotic coral communities were present at all 10 locations, with zooxanthellate scleractinian corals extending down to ~100 metres on walls and ~125 m on steep slopes. Lower mesophotic coral communities were most diverse in the 60–80 m zone, while at depths of ≥100 m the coral community consisted almost exclusively of the genus Leptoseris. Collections of coral specimens (n = 213) between 60 and 125 m depth confirmed the presence of at least 29 different species belonging to 18 genera, including several potential new species and geographic/depth range extensions. Overall, this study highlights that lower mesophotic coral ecosystems are likely to be ubiquitous features on the outer reefs of the Great Barrier Reef and atolls of the Coral Sea, and harbour a generic and species richness of corals that is much higher than thus far reported. Further research efforts are urgently required to better understand and manage these ecosystems as part of the Great Barrier Reef Marine Park and Coral Sea Commonwealth Marine Reserve. PMID:28146574

Lower Mesophotic Coral Communities (60-125 m Depth) of the Northern Great Barrier Reef and Coral Sea.

PubMed

Englebert, Norbert; Bongaerts, Pim; Muir, Paul R; Hay, Kyra B; Pichon, Michel; Hoegh-Guldberg, Ove

2017-01-01

Mesophotic coral ecosystems in the Indo-Pacific remain relatively unexplored, particularly at lower mesophotic depths (≥60 m), despite their potentially large spatial extent. Here, we used a remotely operated vehicle to conduct a qualitative assessment of the zooxanthellate coral community at lower mesophotic depths (60-125 m) at 10 different locations in the Great Barrier Reef Marine Park and the Coral Sea Commonwealth Marine Reserve. Lower mesophotic coral communities were present at all 10 locations, with zooxanthellate scleractinian corals extending down to ~100 metres on walls and ~125 m on steep slopes. Lower mesophotic coral communities were most diverse in the 60-80 m zone, while at depths of ≥100 m the coral community consisted almost exclusively of the genus Leptoseris. Collections of coral specimens (n = 213) between 60 and 125 m depth confirmed the presence of at least 29 different species belonging to 18 genera, including several potential new species and geographic/depth range extensions. Overall, this study highlights that lower mesophotic coral ecosystems are likely to be ubiquitous features on the outer reefs of the Great Barrier Reef and atolls of the Coral Sea, and harbour a generic and species richness of corals that is much higher than thus far reported. Further research efforts are urgently required to better understand and manage these ecosystems as part of the Great Barrier Reef Marine Park and Coral Sea Commonwealth Marine Reserve.

Numerical modelling of climate change impacts on freshwater lenses on the North Sea Island of Borkum

NASA Astrophysics Data System (ADS)

Sulzbacher, H.; Wiederhold, H.; Siemon, B.; Grinat, M.; Igel, J.; Burschil, T.; Günther, T.; Hinsby, K.

2012-03-01

A numerical variable-density groundwater model is set up for the North Sea Island of Borkum to estimate climate change impacts on coastal aquifers and especially the situation of barrier islands in the Wadden Sea. The database includes information from boreholes, a seismic survey, a helicopter-borne electromagnetic survey (HEM), monitoring of the freshwater-saltwater boundary by vertical electrode chains in two boreholes, measurements of groundwater table, pumping and slug tests, as well as water samples. Based on a statistical analysis of borehole columns, seismic sections and HEM, a hydrogeological model is set up. The groundwater model is developed using the finite-element programme FEFLOW. The variable-density groundwater model is calibrated on the basis of hydraulic, hydrological and geophysical data, in particular spatial HEM and local monitoring data. Verification runs with the calibrated model show good agreement between measured and computed hydraulic heads. A good agreement is also obtained between measured and computed density or total dissolved solids data for both the entire freshwater lens on a large scale and in the area of the well fields on a small scale. For simulating future changes in this coastal groundwater system until the end of the current century we use the climate scenario A2, specified by the Intergovernmental Panel on Climate Change and in particular the data for the German North Sea coast. Simulation runs show proceeding salinization with time beneath the well fields of the two waterworks Waterdelle and Ostland. The modelling study shows that spreading of well fields is an appropriate protection measure against excessive salinization of the water supply until the end of the current century.

Increasing species richness of the macrozoobenthic fauna on tidal flats of the Wadden Sea by local range expansion and invasion of exotic species

NASA Astrophysics Data System (ADS)

Beukema, J. J.; Dekker, R.

2011-06-01

A 40-y series of consistently collected samples (15 fixed sampling sites, constant sampled area of 15 × 0.95 m2, annual sampling only in late-winter/early-spring seasons, and consistent sieving and sorting procedures; restriction to 50 easily recognizable species) of macrozoobenthos on Balgzand, a tidal flat area in the westernmost part of the Wadden Sea (The Netherlands), revealed significantly increasing trends of species richness. Total numbers of species annually encountered increased from ~28 to ~38. Mean species density (number of species found per sampling site) increased from ~13 to ~18 per 0.95 m2. During the 40 years of the 1970-2009 period of observation, 4 exotic species invaded the area: (in order of first appearance) Ensis directus, Marenzelleria viridis, Crassostrea gigas, and Hemigrapsus takanoi. Another 5 species recently moved to Balgzand from nearby (subtidal) locations. Together, these 9 new species on the tidal flats explained by far most of the increase in total species numbers, but accounted for only one-third of the observed increase in species density (as a consequence of the restricted distribution of most of them). Species density increased particularly by a substantial number of species that showed increasing trends in the numbers of tidal flat sites they occupied. Most of these wider-spreading species were found to suffer from cold winters. During the 40-y period of observation, winter temperatures rose by about 2°C and cold winters became less frequent. The mean number of cold-sensitive species found per site significantly increased by almost 2 per 0.95 m2. Among the other species (not sensitive to low winter temperatures), 6 showed a rising and 2 a declining trend in number of occupied sites, resulting in a net long-term increase in species density amounting to another gain of 1.6 per 0.95 m2. Half of the 50 studied species did not show such long-term trend, nor were invaders. Thus, each of 3 groups (local or alien invaders

Accelerated relative sea-level rise and rapid coastal erosion: Testing a causal relationship for the Louisiana barrier islands

USGS Publications Warehouse

List, J.H.; Sallenger, A.H.; Hansen, M.E.; Jaffe, B.E.

1997-01-01

The role of relative sea-level rise as a cause for the rapid erosion of Louisiana's barrier island coast is investigated through a numerical implementation of a modified Bruun rule that accounts for the low percentage of sand-sized sediment in the eroding Louisiana shoreface. Shore-normal profiles from 150 km of coastline west of the Mississippi delta are derived from bathymetric surveys conducted during the 1880s. 1930s and 1980s. An RMS difference criterion is employed to test whether an equilibrium profile form is maintained between survey years. Only about half the studied profiles meet the equilibrium Criterion this represents a significant limitation on the potential applicability of the Bruun rule. The profiles meeting the equilibrium criterion, along with measured rates of relative sea-level rise, are used to hindcast shoreline retreat rates at 37 locations within the study area. Modeled and observed shoreline retreat rates show no significant correlation. Thus in terms of the Bruun approach relative sea-level rise has no power for hindcasting (and presumably forecasting) rates of coastal erosion for the Louisiana barrier islands.

Terrestrial and Marine Foraging Strategies of an Opportunistic Seabird Species Breeding in the Wadden Sea.

PubMed

Garthe, Stefan; Schwemmer, Philipp; Paiva, Vitor H; Corman, Anna-Marie; Fock, Heino O; Voigt, Christian C; Adler, Sven

2016-01-01

Lesser black-backed gulls Larus fuscus are considered to be mainly pelagic. We assessed the importance of different landscape elements (open sea, tidal flats and inland) by comparing marine and terrestrial foraging behaviours in lesser black-backed gulls breeding along the coast of the southern North Sea. We attached GPS data loggers to eight incubating birds and collected information on diet and habitat use. The loggers recorded data for 10-19 days to allow flight-path reconstruction. Lesser black-backed gulls foraged in both offshore and inland areas, but rarely on tidal flats. Targets and directions were similar among all eight individuals. Foraging trips (n = 108) lasted 0.5-26.4 h (mean 8.7 h), and ranges varied from 3.0-79.9 km (mean 30.9 km). The total distance travelled per foraging trip ranged from 7.5-333.6 km (mean 97.9 km). Trips out to sea were significantly more variable in all parameters than inland trips. Presence in inland areas was closely associated with daylight, whereas trips to sea occurred at day and night, but mostly at night. The most common items in pellets were grass (48%), insects (38%), fish (28%), litter (26%) and earthworms (20%). There was a significant relationship between the carbon and nitrogen isotope signals in blood and the proportional time each individual spent foraging at sea/land. On land, gulls preferentially foraged on bare ground, with significantly higher use of potato fields and significantly less use of grassland. The flight patterns of lesser black-backed gulls at sea overlapped with fishing-vessel distribution, including small beam trawlers fishing for shrimps in coastal waters close to the colony and large beam-trawlers fishing for flatfish at greater distances. Our data show that individuals made intensive use of the anthropogenic landscape and seascape, indicating that lesser black-backed gulls are not a predominantly marine species during the incubation period.

Terrestrial and Marine Foraging Strategies of an Opportunistic Seabird Species Breeding in the Wadden Sea

PubMed Central

Schwemmer, Philipp; Paiva, Vitor H.; Corman, Anna-Marie; Fock, Heino O.; Voigt, Christian C.; Adler, Sven

2016-01-01

Lesser black-backed gulls Larus fuscus are considered to be mainly pelagic. We assessed the importance of different landscape elements (open sea, tidal flats and inland) by comparing marine and terrestrial foraging behaviours in lesser black-backed gulls breeding along the coast of the southern North Sea. We attached GPS data loggers to eight incubating birds and collected information on diet and habitat use. The loggers recorded data for 10–19 days to allow flight-path reconstruction. Lesser black-backed gulls foraged in both offshore and inland areas, but rarely on tidal flats. Targets and directions were similar among all eight individuals. Foraging trips (n = 108) lasted 0.5–26.4 h (mean 8.7 h), and ranges varied from 3.0–79.9 km (mean 30.9 km). The total distance travelled per foraging trip ranged from 7.5–333.6 km (mean 97.9 km). Trips out to sea were significantly more variable in all parameters than inland trips. Presence in inland areas was closely associated with daylight, whereas trips to sea occurred at day and night, but mostly at night. The most common items in pellets were grass (48%), insects (38%), fish (28%), litter (26%) and earthworms (20%). There was a significant relationship between the carbon and nitrogen isotope signals in blood and the proportional time each individual spent foraging at sea/land. On land, gulls preferentially foraged on bare ground, with significantly higher use of potato fields and significantly less use of grassland. The flight patterns of lesser black-backed gulls at sea overlapped with fishing-vessel distribution, including small beam trawlers fishing for shrimps in coastal waters close to the colony and large beam-trawlers fishing for flatfish at greater distances. Our data show that individuals made intensive use of the anthropogenic landscape and seascape, indicating that lesser black-backed gulls are not a predominantly marine species during the incubation period. PMID:27525661

Use of a Florida Gulf Coast Barrier Island by Spring Trans-Gulf Migrants and the Projected Effects of Sea Level Rise on Habitat Availability.

PubMed

Lester, Lori A; Gutierrez Ramirez, Mariamar; Kneidel, Alan H; Heckscher, Christopher M

2016-01-01

Barrier islands on the north coast of the Gulf of Mexico are an internationally important coastal resource. Each spring hundreds of thousands of Nearctic-Neotropical songbirds crossing the Gulf of Mexico during spring migration use these islands because they provide the first landfall for individuals following a trans-Gulf migratory route. The effects of climate change, particularly sea level rise, may negatively impact habitat availability for migrants on barrier islands. Our objectives were (1) to confirm the use of St. George Island, Florida by trans-Gulf migrants and (2) to determine whether forested stopover habitat will be available for migrants on St. George Island following sea level rise. We used avian transect data, geographic information systems, remote sensing, and simulation modelling to investigate the potential effects of three different sea level rise scenarios (0.28 m, 0.82 m, and 2 m) on habitat availability for trans-Gulf migrants. We found considerable use of the island by spring trans-Gulf migrants. Migrants were most abundant in areas with low elevation, high canopy height, and high coverage of forests and scrub/shrub. A substantial percentage of forest (44%) will be lost by 2100 assuming moderate sea level rise (0.82 m). Thus, as sea level rise progresses, less forests will be available for migrants during stopover. Many migratory bird species' populations are declining, and degradation of barrier island stopover habitat may further increase the cost of migration for many individuals. To preserve this coastal resource, conservation and wise management of migratory stopover areas, especially near ecological barriers like the Gulf of Mexico, will be essential as sea levels rise.

Use of a Florida Gulf Coast Barrier Island by Spring Trans-Gulf Migrants and the Projected Effects of Sea Level Rise on Habitat Availability

PubMed Central

Lester, Lori A.; Gutierrez Ramirez, Mariamar; Kneidel, Alan H.; Heckscher, Christopher M.

2016-01-01

Barrier islands on the north coast of the Gulf of Mexico are an internationally important coastal resource. Each spring hundreds of thousands of Nearctic-Neotropical songbirds crossing the Gulf of Mexico during spring migration use these islands because they provide the first landfall for individuals following a trans-Gulf migratory route. The effects of climate change, particularly sea level rise, may negatively impact habitat availability for migrants on barrier islands. Our objectives were (1) to confirm the use of St. George Island, Florida by trans-Gulf migrants and (2) to determine whether forested stopover habitat will be available for migrants on St. George Island following sea level rise. We used avian transect data, geographic information systems, remote sensing, and simulation modelling to investigate the potential effects of three different sea level rise scenarios (0.28 m, 0.82 m, and 2 m) on habitat availability for trans-Gulf migrants. We found considerable use of the island by spring trans-Gulf migrants. Migrants were most abundant in areas with low elevation, high canopy height, and high coverage of forests and scrub/shrub. A substantial percentage of forest (44%) will be lost by 2100 assuming moderate sea level rise (0.82 m). Thus, as sea level rise progresses, less forests will be available for migrants during stopover. Many migratory bird species’ populations are declining, and degradation of barrier island stopover habitat may further increase the cost of migration for many individuals. To preserve this coastal resource, conservation and wise management of migratory stopover areas, especially near ecological barriers like the Gulf of Mexico, will be essential as sea levels rise. PMID:26934343

Historical changes in the Mississippi-Alabama barrier-island chain and the roles of extreme storms, sea level, and human activities

USGS Publications Warehouse

Morton, R.A.

2008-01-01

Barrier-island chains worldwide are undergoing substantial changes, and their futures remain uncertain. An historical analysis of a barrier-island chain in the north-central Gulf of Mexico shows that the Mississippi barriers are undergoing rapid systematic land loss and translocation associated with: (1) unequal lateral transfer of sand related to greater updrift erosion compared to downdrift deposition; (2) barrier narrowing resulting from simultaneous erosion of shores along the Gulf and Mississippi Sound; and (3) barrier segmentation related to storm breaching. Dauphin Island, Alabama, is also losing land for some of the same reasons as it gradually migrates landward. The principal causes of land loss are frequent intense storms, a relative rise in sea level, and a sediment-budget deficit. Considering the predicted trends for storms and sea level related to global warming, it is certain that the Mississippi-Alabama (MS-AL) barrier islands will continue to lose land area at a rapid rate unless the trend of at least one causal factor reverses. Historical land-loss trends and engineering records show that progressive increases in land-loss rate correlate with nearly simultaneous deepening of channels dredged across the outer bars of the three tidal inlets maintained for deep-draft shipping. This correlation indicates that channel-maintenance activities along the MS-AL barriers have impacted the sediment budget by disrupting the alongshore sediment transport system and progressively reducing sand supply. Direct management of this causal factor can be accomplished by strategically placing dredged sediment where adjacent barrier-island shores will receive it for island nourishment and rebuilding.

Low-head sea lamprey barrier effects on stream habitat and fish communities in the Great Lakes basin

USGS Publications Warehouse

Dodd, H.R.; Hayes, D.B.; Baylis, J.R.; Carl, L.M.; Goldstein, J.D.; McLaughlin, R.L.; Noakes, D.L.G.; Porto, L.M.; Jones, M.L.

2003-01-01

Low-head barriers are used to block adult sea lamprey (Petromyzon marinus) from upstream spawning habitat. However, these barriers may impact stream fish communities through restriction of fish movement and habitat alteration. During the summer of 1996, the fish community and habitat conditions in twenty-four stream pairs were sampled across the Great Lakes basin. Seven of these stream pairs were re-sampled in 1997. Each pair consisted of a barrier stream with a low-head barrier and a reference stream without a low-head barrier. On average, barrier streams were significantly deeper (df = 179, P = 0.0018) and wider (df = 179, P = 0.0236) than reference streams, but temperature and substrate were similar (df = 183, P = 0.9027; df = 179, P = 0.999). Barrier streams contained approximately four more fish species on average than reference streams. However, streams with low-head barriers showed a greater upstream decline in species richness compared to reference streams with a net loss of 2.4 species. Barrier streams also showed a peak in richness directly downstream of the barriers, indicating that these barriers block fish movement upstream. Using S??renson's similarity index (based on presence/absence), a comparison of fish community assemblages above and below low-head barriers was not significantly different than upstream and downstream sites on reference streams (n = 96, P > 0.05), implying they have relatively little effect on overall fish assemblage composition. Differences in the frequency of occurrence and abundance between barrier and reference streams was apparent for some species, suggesting their sensitivity to barriers.

Historical changes in the Mississippi-Alabama barrier islands and the roles of extreme storms, sea level, and human activities

USGS Publications Warehouse

Morton, Robert A.

2007-01-01

westward sediment transport by alongshore currents, and Cat Island is being reshaped as it adjusts to post-formation changes in wave and current patterns associated with deposition of the St. Bernard lobe of the Mississippi delta. The principal causes of barrier island land loss are frequent intense storms, a relative rise in sea level, and a deficit in the sediment budget. The only factor that has a historical trend that coincides with the progressive increase in rates of land loss is the progressive reduction in sand supply associated with nearly simultaneous deepening of channels dredged across the outer bars of the three tidal inlets maintained for deep-draft shipping. Neither rates of relative sea level rise nor storm parameters have long-term historical rends that match the increased rates of land loss since the mid 1800s. The historical rates of relative sea level rise in the northern Gulf of Mexico have been relatively constant and storm frequencies and intensities occur in multidecal cycles. However, the most recent land loss accelerations likely related to the increased storm activity since 1995. Considering the predicted trends for storms and sea level related to global warming, it is clear that the barrier islands will continue to lose land area at a rapid rate without a reversal in trend of at least one of the causal factors. The reduction in sand supply related to disruption of the alongshore sediment transport system is the only factor contributing to land loss that can be managed directly. This can be accomplished by placing dredged material so that the adjacent barrier island shores revive it for island nourishment and rebuilding.

Numerical modelling of climate change impacts on freshwater lenses on the North Sea Island of Borkum using hydrological and geophysical methods

NASA Astrophysics Data System (ADS)

Sulzbacher, H.; Wiederhold, H.; Siemon, B.; Grinat, M.; Igel, J.; Burschil, T.; Günther, T.; Hinsby, K.

2012-10-01

A numerical, density dependent groundwater model is set up for the North Sea Island of Borkum to estimate climate change impacts on coastal aquifers and especially the situation of barrier islands in the Wadden Sea. The database includes information from boreholes, a seismic survey, a helicopter-borne electromagnetic (HEM) survey, monitoring of the freshwater-saltwater boundary by vertical electrode chains in two boreholes, measurements of groundwater table, pumping and slug tests, as well as water samples. Based on a statistical analysis of borehole columns, seismic sections and HEM, a hydrogeological model is set up. The groundwater model is developed using the finite-element programme FEFLOW. The density dependent groundwater model is calibrated on the basis of hydraulic, hydrological and geophysical data, in particular spatial HEM and local monitoring data. Verification runs with the calibrated model show good agreement between measured and computed hydraulic heads. A good agreement is also obtained between measured and computed density or total dissolved solids data for both the entire freshwater lens on a large scale and in the area of the well fields on a small scale. For simulating future changes in this coastal groundwater system until the end of the current century, we use the climate scenario A2, specified by the Intergovernmental Panel on Climate Change and, in particular, the data for the German North Sea coast. Simulation runs show proceeding salinisation with time beneath the well fields of the two waterworks Waterdelle and Ostland. The modelling study shows that the spreading of well fields is an appropriate protection measure against excessive salinisation of the water supply until the end of the current century.

Distribution of sea snakes in the Great Barrier Reef Marine Park: observations from 10 yrs of baited remote underwater video station (BRUVS) sampling

NASA Astrophysics Data System (ADS)

Udyawer, Vinay; Cappo, Mike; Simpfendorfer, Colin A.; Heupel, Michelle R.; Lukoschek, Vimoksalehi

2014-09-01

The distributions of three species of sea snake (olive sea snake: Aipysurus laevis, spine-bellied sea snake: Lapemis curtus, and ornate sea snake: Hydrophis ocellatus) were estimated over 14° of latitude within the Great Barrier Reef Marine Park (GBRMP) using data from baited remote underwater video stations (BRUVS). A total of 2,471 deployments of BRUVS were made in a range of locations, in sites open and closed to trawl fishing. Sightings of sea snakes were analysed alongside six spatial factors [depth, relative distance across (longitude) and along (latitude) the GBRMP, proximity to land, proximity to the nearest reef, and habitat complexity] to determine the factors that most strongly influenced the distribution and abundance of sea snakes. The results showed a strong latitudinal effect on the distribution of all three sea snake species, with the highest densities and diversities occurring in central and southern GBRMP locations, while the northern Great Barrier Reef was relatively depauperate in terms of both occurrence and diversity. Shallow inshore areas were identified as key habitats for A. laevis and L. curtus, whereas deeper offshore habitats were most important for H. ocellatus. No significant difference was found in the mean number of snakes sighted per hour between sites open and closed to trawling. There was a high degree of congruence in the distribution of sea snakes estimated from the BRUVS data and results from previous trawl and underwater visual surveys, demonstrating the utility of BRUVS to estimate distribution and relative abundance in these species of sea snake at broad spatial scales in a non-extractive manner.

Major coastal impact induced by a 1000-year storm event

PubMed Central

Fruergaard, Mikkel; Andersen, Thorbjørn J.; Johannessen, Peter N.; Nielsen, Lars H.; Pejrup, Morten

2013-01-01

Extreme storms and storm surges may induce major changes along sandy barrier coastlines, potentially causing substantial environmental and economic damage. We show that the most destructive storm (the 1634 AD storm) documented for the northern Wadden Sea within the last thousand years both caused permanent barrier breaching and initiated accumulation of up to several metres of marine sand. An aggradational storm shoal and a prograding shoreface sand unit having thicknesses of up to 8 m and 5 m respectively were deposited as a result of the storm and during the subsequent 30 to 40 years long healing phase, on the eroded shoreface. Our results demonstrate that millennial-scale storms can induce large-scale and long-term changes on barrier coastlines and shorefaces, and that coastal changes assumed to take place over centuries or even millennia may occur in association with and be triggered by a single extreme storm event.

Modeling Catastrophic Barrier Island Dynamics

NASA Astrophysics Data System (ADS)

Whitley, J. W.; McNamara, D.

2012-12-01

Barrier islands, thin strips of sand lying parallel to the mainland coastline, along the U.S. Atlantic and Gulf Coasts appear to have maintained their form for thousands of years in the face of rising sea level. The mechanisms that allow barrier islands to remain robust are transport of sediment from the ocean side of barriers to the top and backside during storms, termed island overwash, and the growth and alongshore propagation of tidal deltas near barrier island inlets. Dynamically these processes provide the necessary feedbacks to maintain a barrier island in an attractor that withstands rising sea level within a phase space of barrier island geometrical characteristics. Current barrier island configurations along the Atlantic and Gulf coasts exist among a wide range of storm climate and underlying geologic conditions and therefore the environment that forces overwash and tidal delta dynamics varies considerably. It has been suggested that barrier islands in certain locations such as those between Avon and Buxton (losing 76% of island width since 1852) and Chandeleur islands (losing 85% of its surface area since 2005) along the Atlantic and Gulf coasts, respectively, may be subject to a catastrophic shift in barrier island attractor states - more numerous inlets cutting barriers in some locations and the complete disappearance of barrier islands in other locations. In contrast to common models for barrier islands that neglect storm dynamics and often only consider cross-shore response, we use an alongshore extended model for barrier island dynamics including beach erosion, island overwash and inlet cutting during storms, and beach accretion, tidal delta growth and dune and vegetation growth between storms to explore the response of barrier islands to a wide range of environmental forcing. Results will be presented that show how barrier island attractor states are altered with variations in the rate of sea level rise, storminess, and underlying geology. We will

Modeling vegetation community responses to sea-level rise on Barrier Island systems: A case study on the Cape Canaveral Barrier Island complex, Florida, USA

PubMed Central

Foster, Tammy E.; Stolen, Eric D.; Hall, Carlton R.; Schaub, Ronald; Duncan, Brean W.; Hunt, Danny K.; Drese, John H.

2017-01-01

Society needs information about how vegetation communities in coastal regions will be impacted by hydrologic changes associated with climate change, particularly sea level rise. Due to anthropogenic influences which have significantly decreased natural coastal vegetation communities, it is important for us to understand how remaining natural communities will respond to sea level rise. The Cape Canaveral Barrier Island complex (CCBIC) on the east central coast of Florida is within one of the most biologically diverse estuarine systems in North America and has the largest number of threatened and endangered species on federal property in the contiguous United States. The high level of biodiversity is susceptible to sea level rise. Our objective was to model how vegetation communities along a gradient ranging from hydric to upland xeric on CCBIC will respond to three sea level rise scenarios (0.2 m, 0.4 m, and 1.2 m). We used a probabilistic model of the current relationship between elevation and vegetation community to determine the impact sea level rise would have on these communities. Our model correctly predicted the current proportions of vegetation communities on CCBIC based on elevation. Under all sea level rise scenarios the model predicted decreases in mesic and xeric communities, with the greatest losses occurring in the most xeric communities. Increases in total area of salt marsh were predicted with a 0.2 and 0.4 m rise in sea level. With a 1.2 m rise in sea level approximately half of CCBIC’s land area was predicted to transition to open water. On the remaining land, the proportions of most of the vegetation communities were predicted to remain similar to that of current proportions, but there was a decrease in proportion of the most xeric community (oak scrub) and an increase in the most hydric community (salt marsh). Our approach provides a first approximation of the impacts of sea level rise on terrestrial vegetation communities, including important

Adaptation of benthic invertebrates to food sources along marine-terrestrial boundaries as indicated by carbon and nitrogen stable isotopes

NASA Astrophysics Data System (ADS)

Lange, G.; Haynert, K.; Dinter, T.; Scheu, S.; Kröncke, I.

2018-01-01

Frequent environmental changes and abiotic gradients of the Wadden Sea require appropriate adaptations of the local organisms and make it suitable for investigations on functional structure of macrozoobenthic communities from marine to terrestrial boundaries. To investigate community patterns and food use of the macrozoobenthos, a transect of 11 stations was sampled for species number, abundance and stable isotope values (δ13C and δ15N) of macrozoobenthos and for stable isotope values of potential food resources. The transect was located in the back-barrier system of the island of Spiekeroog (southern North Sea, Germany). Our results show that surface and subsurface deposit feeders, such as Peringia ulvae and different oligochaete species, dominated the community, which was poor in species, while species present at the transect stations reached high abundance. The only exception was the upper salt marsh with low abundances but higher species richness because of the presence of specialized semi-terrestrial and terrestrial taxa. The macrozoobenthos relied predominantly on marine resources irrespective of the locality in the intertidal zone, although δ13C values of the consumers decreased from - 14.1 ± 1.6‰ (tidal flats) to - 21.5 ± 2.4‰ (salt marsh). However, the ubiquitous polychaete Hediste diversicolor showed a δ15N enrichment of 2.8‰ (an increase of about one trophic level) from bare sediments to the first vegetated transect station, presumably due to switching from suspension or deposit feeding to predation on smaller invertebrates. Hence, we conclude that changes in feeding mode represent an important mechanism of adaptation to different Wadden Sea habitats.

Can human activities alter the drowning fate of barrier islands?

NASA Astrophysics Data System (ADS)

Lorenzo-Trueba, J.; Ashton, A. D.; Jin, D.; Hoagland, P.; Kite-Powell, H.

2012-12-01

Low-lying coastal barriers face an uncertain future over the coming century and beyond as sea levels rise, with many projections suggesting end-of-century rates of sea-level rise as high or higher than 1 cm/yr. Geologically, such rates of sea-level rise have been experienced several thousand years ago and we can use our understanding of geological processes and sedimentary evidence to help unravel the dynamics of natural barriers experiencing sea-level rise. Along many modern coastal barriers, however, anthropic change, such as beach nourishment, dune construction, and emplacement of hard structures, plays a dominant role in coastline dynamics. A fundamental question to be addressed is whether human activities intended to preserve infrastructure and beach recreation may make wholesale collapse, or 'drowning,' of barrier systems more likely. Here we present a numerical modeling tool that couples natural processes and the human responses to these changes (and the subsequent of human responses on natural processes). Recent theoretical model development suggests that barriers are intrinsically morphodynamic features, responding to sea-level rise in complex ways through the interactions of marine processes and barrier overwash. Undeveloped coastal barriers would therefore respond to an accelerated sea-level rise in complex, less predictable manners than suggested by existing long-term models. We have developed a model that examines non-equilibrium cross-shore evolution of barrier systems at decadal to centennial temporal scales, focusing on the interactions between processes of shoreface evolution and overwash deposition. Model responses demonstrate two means of barrier collapse during sea-level rise: 'height drowning', which occurs when overwash fluxes are insufficient to maintain the landward migration rate required to keep in pace with sea-level rise, and 'width drowning', which occurs when the shoreface response is insufficient to maintain the barrier geometry

Distributions and characteristics of dissolved organic matter in temperate coastal waters (Southern North Sea)

NASA Astrophysics Data System (ADS)

Lübben, Andrea; Dellwig, Olaf; Koch, Sandra; Beck, Melanie; Badewien, Thomas H.; Fischer, Sibylle; Reuter, Rainer

2009-04-01

The spatial and temporal distributions of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) was studied in the East-Frisian Wadden Sea (Southern North Sea) during several cruises between 2002 and 2005. The spatial distribution of CDOM in the German Bight shows a strong gradient towards the coast. Tidal and seasonal variations of dissolved organic matter (DOM) identify freshwater discharge via flood-gates at the coastline and pore water efflux from tidal flat sediments as the most important CDOM sources within the backbarrier area of the Island of Spiekeroog. However, the amount and pattern of CDOM and DOC is strongly affected by various parameters, e.g. changes in the amount of terrestrial run-off, precipitation, evaporation, biological activity and photooxidation. A decoupling of CDOM and DOC, especially during periods of pronounced biological activity (algae blooms and microbial activity), is observed in spring and especially in summer. Mixing of the endmembers freshwater, pore water, and open sea water results in the formation of a coastal transition zone. Whilst an almost conservative behaviour during mixing is observed in winter, summer data point towards non-conservative mixing.

Castaways can't be choosers - Homogenization of rafting assemblages on floating seaweeds

NASA Astrophysics Data System (ADS)

Gutow, Lars; Beermann, Jan; Buschbaum, Christian; Rivadeneira, Marcelo M.; Thiel, Martin

2015-01-01

After detachment from benthic habitats, the epibiont assemblages on floating seaweeds undergo substantial changes, but little is known regarding whether succession varies among different seaweed species. Given that floating algae may represent a limiting habitat in many regions, rafting organisms may be unselective and colonize any available seaweed patch at the sea surface. This process may homogenize rafting assemblages on different seaweed species, which our study examined by comparing the assemblages on benthic and floating individuals of the fucoid seaweeds Fucus vesiculosus and Sargassum muticum in the northern Wadden Sea (North Sea). Species richness was about twice as high on S. muticum as on F. vesiculosus, both on benthic and floating individuals. In both seaweed species benthic samples were more diverse than floating samples. However, the species composition differed significantly only between benthic thalli, but not between floating thalli of the two seaweed species. Separate analyses of sessile and mobile epibionts showed that the homogenization of rafting assemblages was mainly caused by mobile species. Among these, grazing isopods from the genus Idotea reached extraordinarily high densities on the floating samples from the northern Wadden Sea, suggesting that the availability of seaweed rafts was indeed limiting. Enhanced break-up of algal rafts associated with intense feeding by abundant herbivores might force rafters to recolonize benthic habitats. These colonization processes may enhance successful dispersal of rafting organisms and thereby contribute to population connectivity between sink populations in the Wadden Sea and source populations from up-current regions.

Dynamic simulation of storm-driven barrier island morphology under future sea level rise

NASA Astrophysics Data System (ADS)

Passeri, D. L.; Long, J.; Plant, N. G.; Bilskie, M. V.; Hagen, S. C.

2016-12-01

The impacts of short-term processes such as tropical and extratropical storms have the potential to alter barrier island morphology. On the event scale, the effects of storm-driven morphology may result in damage or loss of property, infrastructure and habitat. On the decadal scale, the combination of storms and sea level rise (SLR) will evolve barrier islands. The effects of SLR on hydrodynamics and coastal morphology are dynamic and inter-related; nonlinearities in SLR can cause larger peak surges, lengthier inundation times and additional inundated land, which may result in increased erosion, overwash or breaching along barrier islands. This study uses a two-dimensional morphodynamic model (XBeach) to examine the response of Dauphin Island, AL to storm surge under future SLR. The model is forced with water levels and waves provided by a large-domain hydrodynamic model. A historic validation of hurricanes Ivan and Katrina indicates the model is capable of predicting morphologic response with high skill (0.5). The validated model is used to simulate storm surge driven by Ivan and Katrina under four future SLR scenarios, ranging from 20 cm to 2 m. Each SLR scenario is implemented using a static or "bathtub" approach (in which water levels are increased linearly by the amount of SLR) versus a dynamic approach (in which SLR is applied at the open ocean boundary of the hydrodynamic model and allowed to propagate through the domain as guided by the governing equations). Results illustrate that higher amounts of SLR result in additional shoreline change, dune erosion, overwash and breaching. Compared to the dynamic approach, the static approach over-predicts inundation, dune erosion, overwash and breaching of the island. Overall, results provide a better understanding of the effects of SLR on storm-driven barrier island morphology and support a paradigm shift away from the "bathtub" approach, towards considering the integrated, dynamic effects of SLR.

Migrating Shoals on Ebb-tidal Deltas: Results from Numerical Simulations

NASA Astrophysics Data System (ADS)

van der Vegt, M.; Ridderinkhof, W.; De Swart, H. E.; Hoekstra, P.

2016-02-01

Many ebb-tidal deltas show repetitive patterns of channel- shoal generation, migration and attachment of shoals to the downdrift barrier coast. For the Wadden Sea coast along the Dutch, German en Danish coastline the typical time scale of shoal attachment ranges from several to hundred years. There is a weak correlation between the tidal prism and the typical time scale of shoal attachment. The main aim of this research is to clarify the physical processes that result in the formation of shoals on ebb-tidal deltas and to study what determines their propagation speed. To this end numerical simulations were performed in Delft3D. Starting from an idealized geometry with a sloping bed on the shelf sea and a flat bed in the back barrier basin, the model was spun up until an approximate morphodynamic steady state was realized. The model was forced with tides and constant wave forcing based on the yearly average conditions along the Dutch Wadden coast. The resulting ebb-tidal delta is called the equilibrium delta. Next, two types of scenarios were run. First, the equilibrium delta was breached by creating a channel and adding the removed sand volume to the downdrift shoal. Second, the wave climate was made more realistic by adding storms and subsequently its effect on the equilibrium delta was simulated. Based on the model results we conclude the following. First, the model is able to realistically simulate the migration of shoals and the attachment to the downdrift barrier island. Second, larger waves result in faster propagation of the shoals. Third, simulations suggest that shoals only migrate when they are shallower than a critical maximum depth with respect to the wave height. These shallow shoals can be `man-made' or be generated during storms. When no storms were added to the wave climate and the bed was not artificially disturbed, no migrating shoals were simulated. During the presentation the underlying physical processes will be discussed in detail.

First results from IODP Expedition 325 to the Great Barrier Reef: unlocking climate and sea level secrets since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Webster, J. M.; Yokoyama, Y.; Cotterill, C.; Expedition 325 Scientists

2010-12-01

Integrated Ocean Drilling Program (IODP) Exp. 325 (GBREC: Great Barrier Reef Environmental Change) that investigated fossil reefs on the shelf edge of the Great Barrier Reef (GBR), was the fourth IODP expedition to use a mission-specific platform, and was conducted by the European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO). The scientific objectives are to establish the course of sea level change, define sea-surface temperature variations, and to analyze the impact of these environmental changes on reef growth and geometry over the period of 20-10 ka. Exp.325 complements and extends the findings of the 2005 Exp. 310 (Tahiti Sea Level) that recovered Postglacial coral reef cores from the flanks of Tahiti from 41.6-117.5 meters below sea level and spanned ~16 to ~8 ka. Preliminary data confirms that Exp. 325 recovered truly unique and valuable fossil coral reef material from key periods in Earth's sea level and climate history from 30 to 9 ka. On Exp. 325 a succession of fossil reef structures preserved on the shelf edge seaward of the modern barrier reef were cored at three geographic locations (Hydrographers Passage, Noggin Pass and Ribbon Reef) from a dynamically positioned vessel in February-April 2010. A total of 34 boreholes were cored from 17 sites in four transects at depths ranging from 42.2 to 167.2 meters below sea level. Borehole logging of four boreholes provided continuous geophysical information about the drilled strata. The cores were split and described during the Onshore Science Party at the IODP Bremen Core Repository (Germany) in July 2010, where minimum and some standard measurements were made. Initial lithologic and biologic observations identified high-quality fossil coralgal frameworks, consistent with shallow, high energy reef settings - crucial for precise reconstructions of sea level and paleoclimate change. Preliminary C14-AMS and U-Th age interpretations from 60 core catcher samples confirmed that the cores span

Distribution and abundance of anadromous Sea Lamprey Spawners in a fragmented stream: Current status and potential range expansion following barrier removal

USGS Publications Warehouse

Zydlewski, Joseph D.; Gardner, Cory; Coghlan, Stephen M.

2012-01-01

Dams fragment watersheds and prevent anadromous fishes from reaching historic spawning habitat. Sedgeunkedunk Stream, a small tributary to the Penobscot River (Maine), has been the focus of efforts to reestablish marine-freshwater connectivity and restore anadromous fishes via the removal of two barriers to fish migration. Currently, Petromyzon marinus (Sea Lamprey) is the only anadromous fish known to spawn successfully in the stream downstream of the lowermost dam. Here, we describe the distribution and abundance of a spawning population of Sea Lamprey in Sedgeunkedunk Stream, prior to and in anticipation of habitat increase after the completion of one barrier removal. In 2008, we estimated the abundance of Sea Lamprey and its nests using daily stream surveys and an open-population mark-recapture model. We captured 47 Sea Lamprey and implanted each with a PIT tag so that we could track movements and nest associations of individual fish. The spawning migration began on 18 June, and the last living individual was observed on 27 June. We located 31 nests, distributed from head-of-tide to the lowermost dam; no spawners or nests were observed in the tidally influenced zone or upstream of this dam. Mean longevity in the stream and the number of nests attended were correlated with arrival date; early migrants were alive longer and attended more nests than later migrants. Males were more likely to be observed away from a nest, or attending three or more nests, than were females, which attended usually one or two nests. We observed a negative association between nest abundance and substrate cover by fine sediment. Based on their observed movements in the system, and the extent of their habitat use, we anticipate that spawning Sea Lamprey will recolonize formerly inaccessible habitat after dam removals.

Response of the Great Barrier Reef to sea-level and environmental changes over the past 30,000 years

NASA Astrophysics Data System (ADS)

Webster, Jody M.; Braga, Juan Carlos; Humblet, Marc; Potts, Donald C.; Iryu, Yasufumi; Yokoyama, Yusuke; Fujita, Kazuhiko; Bourillot, Raphael; Esat, Tezer M.; Fallon, Stewart; Thompson, William G.; Thomas, Alexander L.; Kan, Hironobu; McGregor, Helen V.; Hinestrosa, Gustavo; Obrochta, Stephen P.; Lougheed, Bryan C.

2018-06-01

Previous drilling through submerged fossil coral reefs has greatly improved our understanding of the general pattern of sea-level change since the Last Glacial Maximum, however, how reefs responded to these changes remains uncertain. Here we document the evolution of the Great Barrier Reef (GBR), the world's largest reef system, to major, abrupt environmental changes over the past 30 thousand years based on comprehensive sedimentological, biological and geochronological records from fossil reef cores. We show that reefs migrated seaward as sea level fell to its lowest level during the most recent glaciation ( 20.5-20.7 thousand years ago (ka)), then landward as the shelf flooded and ocean temperatures increased during the subsequent deglacial period ( 20-10 ka). Growth was interrupted by five reef-death events caused by subaerial exposure or sea-level rise outpacing reef growth. Around 10 ka, the reef drowned as the sea level continued to rise, flooding more of the shelf and causing a higher sediment flux. The GBR's capacity for rapid lateral migration at rates of 0.2-1.5 m yr-1 (and the ability to recruit locally) suggest that, as an ecosystem, the GBR has been more resilient to past sea-level and temperature fluctuations than previously thought, but it has been highly sensitive to increased sediment input over centennial-millennial timescales.

Emergent Behavior of Coupled Barrier Island - Resort Systems

NASA Astrophysics Data System (ADS)

McNamara, D. E.; Werner, B. T.

2004-12-01

Barrier islands are attractive sites for resorts. Natural barrier islands experience beach erosion and island overwash during storms, beach accretion and dune building during inter-storm periods, and migration up the continental shelf as sea level rises. Beach replenishment, artificial dune building, seawalls, jetties and groins have been somewhat effective in protecting resorts against erosion and overwash during storms, but it is unknown how the coupled system will respond to long-term sea level rise. We investigate coupled barrier island - resort systems using an agent-based model with three components: natural barrier islands divided into a series of alongshore cells; resorts controlled by markets for tourism and hotel purchases; and coupling via storm damage to resorts and resort protection by government agents. Modeled barrier islands change by beach erosion, island overwash and inlet cutting during storms, and beach accretion, tidal delta growth and dune and vegetation growth between storms. In the resort hotel market, developer agents build hotels and hotel owning agents purchase them using predictions of future revenue and property appreciation, with the goal of maximizing discounted utility. In the tourism market, hotel owning agents set room rental prices to maximize profit and tourist agents choose vacation destinations maximizing a utility based on beach width, price and word-of-mouth. Government agents build seawalls, groins and jetties, and widen the beach and build up dunes by adding sand to protect resorts from storms, enhance beach quality, and maximize resort revenue. Results indicate that barrier islands and resorts evolve in a coupled manner to resort size saturation, with resorts protected against small-to-intermediate-scale storms under fairly stable sea level. Under extended, rapidly rising sea level, protection measures enhance the effect of large storms, leading to emergent behavior in the form of limit cycles or barrier submergence

Mesoscale barrier estuary behaviour in response to sea-level rise, storms and sediment supply.

NASA Astrophysics Data System (ADS)

Hamilton, Christine; Kirby, Jason; Plater, Andrew; Lane, Timothy

2017-04-01

Future vulnerability and resilience of coastal landscapes, and their associated communities, infrastructure and nature conservation interests, is of increasing concern due to the combined effects of climate change and sea-level rise. The Suffolk coast, UK, characterised by gravel barrier beaches and a spit feature of international geomorphological interest, has changed dramatically. However, existing Holocene research in this respect is limited. Sediments preserved within the enclosed valleys and back-barrier wetlands of Suffolk provide an opportunity to improve understanding of the complex mesoscale (years-decades-centuries) behaviour of coastlines and their geomorphological response to changes in natural forcing. This research aims to reconstruct Holocene changes in coastline behaviour to develop reconstructions of coastal evolution relating to changes in relative sea level, sediment supply and storm incidence. Litho- and bio-stratigraphic analysis (sedimentology, particle size, and diatom analysis) has been undertaken on three marsh and wetland sites in a 5 km section between Walberswick and Dunwich. Though intra-site sediment variability is high, a consistent pattern of interbedded intertidal and freshwater units separated by transitional marsh deposits is seen at all sites. Diatom analysis from two sites (Westwood Marsh and Oldtown Marsh) indicates increased marine and brackish conditions across the organic-minerogenic transitions. The diatom assemblage from Great Dingle Hill, a more seaward site, is dominated by brackish species, with an increase in marine conditions across the main organic-minerogenic stratigraphic transition. Freshwater and salt tolerant species are minimal in this assemblage, indicating a constant saltwater input. The onset of peat deposition has been dated to 6950-6790 cal. BP at the base of the Westwood Marsh sequence. These results contrast with existing research from the Blyth estuary (5 km north) where peat deposition was dated to

Height system connection between island and mainland using a hydrodynamic model: a case study connecting the Dutch Wadden islands to the Amsterdam ordnance datum (NAP)

NASA Astrophysics Data System (ADS)

Slobbe, D. C.; Klees, R.; Verlaan, M.; Zijl, F.; Alberts, B.; Farahani, H. H.

2018-03-01

We present an efficient and flexible alternative method to connect islands and offshore tide gauges with the height system on land. The method uses a regional, high-resolution hydrodynamic model that provides total water levels. From the model, we obtain the differences in mean water level (MWL) between tide gauges at the mainland and at the islands or offshore platforms. Adding them to the MWL relative to the national height system at the mainland's tide gauges realizes a connection of the island and offshore platforms with the height system on the mainland. Numerical results are presented for the connection of the Dutch Wadden islands with the national height system (Normaal Amsterdams Peil, NAP). Several choices of the period over which the MWLs are computed are tested and validated. The best results were obtained when we computed the MWL only over the summer months of our 19-year simulation period. Based on this strategy, the percentage of connections for which the absolute differences between the observation- and model-derived MWL differences are ≤ 1 cm is about 34% (46 out of 135 possible leveling connections). In this case, for each Wadden island we can find several connections that allow the transfer of NAP with (sub-)centimeter accuracy.

Warm Rivers Play Role in Arctic Sea Ice Melt

NASA Image and Video Library

2014-03-05

Beaufort Sea surface temperatures where Canada Mackenzie River discharges into the Arctic Ocean, measured by NASA MODIS instrument; warm river waters had broken through a shoreline sea ice barrier to enhance sea ice melt.

Climate change and oceanic barriers: genetic differentiation in Pomatomus saltatrix (Pisces: Pomatomidae) in the North Atlantic Ocean and the Mediterranean Sea.

PubMed

Pardiñas, A F; Campo, D; Pola, I G; Miralles, L; Juanes, F; Garcia-Vazquez, E

2010-11-01

Nucleotide variation of partial cytochrome b sequences was analysed in the bluefish Pomatomus saltatrix to investigate the population-structuring roles of climate change and oceanic barriers. Western and eastern North Atlantic Ocean populations appeared to be totally isolated, with the latter connected to the Mediterranean Sea within which further structuring occurred. © 2010 The Authors. Journal of Fish Biology © 2010 The Fisheries Society of the British Isles.

Warm Rivers Play Role in Arctic Sea Ice Melt Animation

NASA Image and Video Library

2014-03-05

This frame from a NASA MODIS animation depicts warming sea surface temperatures in the Arctic Beaufort Sea after warm waters from Canada Mackenzie River broke through a shoreline sea ice barrier in summer 2012, enhancing the melting of sea ice.

Temporal changes in phytoplankton biomass and cellular properties; implications for the IMO ballast water convention.

PubMed

de Castro, Maria Cecilia Trindade; Veldhuis, Marcel J W

2018-01-24

In the Wadden Sea, the Netherlands, and at L4 in the English Channel, UK, the size class distribution of phytoplankton was investigated with respect to the size range >10-≤50 µm identified by the IMO Ballast Water Convention. Size fractionation using 10 µm mesh filtration showed considerable size bias; 23.1% of >10 µm cells were still present in the <10 µm, but 21.8% of the smaller size cells were also retained on the mesh, resulting in an overestimated number of cells/mL by as much as a factor of 5.4. Flowcytometry measurements indicated that the phytoplankton in the size range 2-50  µm was dominated by the smaller size (<10 µm) at both sites. For the >10-≤50 µm size, these were on average 3.6% and 2% in the Wadden Sea and at L4, respectively. In terms of chlorophyll biomass, they represented 28.7% and 12%, respectively. The filtration method resulted in much higher chlorophyll values for 10-50  µm size range: 53.7% in the Wadden Sea and 38% at L4. This overestimation appears to be caused by cells in 6-10  µm size range being retained on the mesh. These findings are relevant in the context of the size class distribution based on flowcytometry and semi-quantification using chlorophyll as proxy for cell density.

Barrier Island Failure During Hurricane Katrina

NASA Astrophysics Data System (ADS)

Sallenger, A.; Howd, P.; Stockdon, H.; Wright, C. W.; Fauver, L.; Guy, K.

2006-12-01

Classical models of barrier-island response to storms predict that wave runup can periodically overtop an island and transport sand from its seaside to its bayside, forcing the island to migrate landward. While this process can destroy fixed human developments, the island survives with little net change in form or dimensions. In contrast, we find that Louisiana's Chandeleur Islands during Hurricane Katrina were not periodically overtopped by waves, but were continuously inundated by storm surge. When such inundation occurs locally on a barrier island, it can force the erosion of a narrow breach that connects sea and bay. However, little is known about the response of a barrier island when it is entirely submerged. Here, we show that the Chandeleur Islands approached complete failure, losing 84% of their surface area. Their Gulf of Mexico shorelines retreated landward an average of 268 m, the largest retreat ever reported for a storm. Sand was stripped from the islands, reducing their peak elevation from >6 m to <3 m and exposing them to further degradation and potential failure by future hurricanes of less intensity than Katrina. Further, the islands that survived Katrina were marsh remnants composed of mud and vegetation that relatively small waves diminished following the storm. The Chandeleur Islands are prone to failure because of their location on the Mississippi delta where small sand supply and large sea-level rise (induced locally by land subsidence) limit natural rebuilding of the islands following a storm. The response of the delta's barrier islands during Hurricane Katrina provides a warning of how the world's barrier islands might respond to storm-surge inundation should predictions of accelerated global sea level rise prove accurate.

Barriers to teaching ocean science in Greek schools

NASA Astrophysics Data System (ADS)

Papathanassiou, Martha; McHugh, Patricia; Domegan, Christine; Gotensparre, Susan; Fauville, Geraldine; Parr, Jon

2017-04-01

Most European citizens are not aware of the full extent of the medical, economic, social, political and environmental importance of the sea to Europe and beyond. Most citizens are not aware of how our day-to-day actions can have a cumulative effect on the health of the ocean - a necessary resource that must be protected for all life on the planet Earth to exist. In other words, European citizens lack a sense of "Ocean Literacy" - an understanding of the ocean's influence on us and our influence on the ocean. Sea Change, a 3.5 million EU-funded project started in March 2015, is designed to bring about a fundamental 'Sea Change' in the way European citizens view their relationship with the sea, by empowering them as 'Ocean Literate' citizens - to take direct and sustainable action towards healthy seas and ocean, healthy communities and ultimately, a healthy planet. The project involves 17 partners from nine countries across Europe and will bring about real actions using behavior change and social engagement methodologies. Building upon the latest research on citizen and stakeholder attitudes, perceptions and values, the Sea Change partnership will design and implement mobilisation activities focused on education, community, government agencies, policy makers and citizens. Eight consultations were held around Europe with regards to barriers to teaching ocean science at schools. All project partners used a Collective Intelligence (CI) methodology to involve target group(s) in active, direct participation for Sea Change. CI is a "barriers and value" structuring methodology, a process of critical learning and reflection followed by action, and then by more critical learning to enable mobilisation, design and development 'with' people rather than on their behalf. In Greece, the consultation was carried out by HCMR, the lead partner for Greece. Participants were recruited through personal contact and existing education networks that the HCMR has previously worked with. In

Changes over 50 years in fish fauna of a temperate coastal sea: Degradation of trophic structure and nursery function

NASA Astrophysics Data System (ADS)

van der Veer, Henk W.; Dapper, Rob; Henderson, Peter A.; Jung, A. Sarina; Philippart, Catharina J. M.; Witte, Johannes IJ.; Zuur, Alain F.

2015-03-01

The ongoing daily sampling programme of the fish fauna in the Dutch Wadden Sea using fixed gear was analysed for the years 1960-2011. Spring sampling caught immigrating fish from the coastal zone and autumn samples reflected emigration of young-of-the-year. In total 82 fish species were caught with no clear trend in biodiversity. In both spring and autumn total daily catch fluctuated and peaked in the late 1970s. From 1980 to the present catches of both pelagic and demersal species showed a 10-fold decrease in total biomass. Mean individual biomass decreased in spring between 1980 and the present from about 150 to 20 g wet weight. No trend was found in autumn mean individual biomass which fluctuated around 20 g wet weight. The trophic structure remained constant for both the demersal and benthopelagic fish fauna from 1980 to 2011, whilst the trophic position of pelagic fish in spring fell from about 3.9 to 3.1. Min/max auto-correlation factor analysis showed similar trends in spring and autumn species biomass time series: the first axis represented a decrease from the 1960s followed by stabilization from the mid-1990s. The second trend showed an increase with a maximum around 1980 followed by a steady decrease in spring and a decrease and stabilization from 2000 in autumn. It is argued that the most likely explanatory variables are a combination of external factors: increased water temperature, habitat destruction in the coastal zone (sand dredging and beach nourishment, fishing) and increased predation by top predators for the first trend, and large-scale hydrodynamic circulation for the second trend. We conclude that both the trophic structure of the coastal zone fauna and the nursery function of the Wadden Sea have been reduced since the 1980s. Our findings corroborate that ecological change in coastal ecosystems has not only occurred in the past but still continues.

Food intake and growth of Sarsia tubulosa (SARS, 1835), with quantitative estimates of predation on copepod populations

NASA Astrophysics Data System (ADS)

Daan, Rogier

In laboratory tests food intake by the hydromedusa Sarsia tubulosa, which feeds on copepods, was quantified. Estimates of maximum predation are presented for 10 size classes of Sarsia. Growth rates, too, were determined in the laboratory, at 12°C under ad libitum food conditions. Mean gross food conversion for all size classes averaged 12%. From the results of a frequent sampling programme, carried out in the Texelstroom (a tidal inlet of the Dutch Wadden Sea) in 1983, growth rates of Sarsia in the field equalled maximum growth under experimental conditions, which suggests that Sarsia in situ can feed at an optimum level. Two estimates of predation pressure in the field matched very closely and lead to the conclusion that the impact of Sarsia predation on copepod standing stocks in the Dutch coastal area, including the Wadden Sea, is generally negligible.

Amino acid racemization analysis (AAR) as a successful tool for dating Holocene coastal sediments: Stratigraphy of a barrier island spit (Southern Sylt/North Sea)

NASA Astrophysics Data System (ADS)

Tillmann, Tanja; Ziehe, Daniel

2014-05-01

Dating of Holocene sediments in shallow coastal areas of the German North Sea by conventional techniques is commonly problematic. In particular the marine reservoir effect of radiocarbon means that radiocarbon dating cannot be applied to sediments younger than about 400 years. Amino acid racemization dating (AAR) is a viable alternative for dating young sediments. The method is based on the determination of ratios of D and L amino acid enantiomers in organic matrices of biogenic carbonates. In this study we use AAR as a tool for dating Holocene barrier islands sediments. Based on an AAR derived chronological framework we develop a model of barrier spit accretion which describes the interaction between extreme events, fair weather coastal processes and sedimentary development that constrains the major episodes of barrier island evolution. The stratigraphy was defined using ground-penetrating radar (GPR) surveys complemented by sedimentological coring data. The stratigraphy is then conceptualised in a AAR chronostratigraphic framework to define a chronological order and allow the development of a stratigraphic model of the evolution of Southern Sylt. The AAR data provide high temporal resolution and have been used for dating stages of barrier spit accretion. The time lines are marked as storm surge generated erosion unconformities in the stratigraphic profile. Individual shells and shell fragments of Cerastoderma edule, Mya arenaria, Mytilus edulis and Scrobicularia plana have been accumulated by short-term storm events as shell layers associated with the erosion unconformities and have been dated by AAR. Time lines reveal that the barrier spit accretion occurred episodically, and is dependant on the provided rate of sand delivery. The general trend is that sequences young to the. South. The AAR derived time lines have been verified and correlated by historic maps and sea charts. It is apparent that spit enlargement at this site increased significantly during the

Tidal cycles of total particulate mercury in the Jade Bay, lower Saxonian Wadden Sea, southern North Sea.

PubMed

Jin, Huafang; Liebezeit, Gerd

2013-01-01

In this study, we evaluate the nature of the relationship between particulate matter and total mercury concentrations. For this purpose, we estimate both of the two values in water column over 12-h tidal cycles of the Jade Bay, southern North Sea. Total particulate mercury in 250 mL water samples was determined by oxygen combustion-gold amalgamation. Mercury contents varied from 63 to 259 ng/g suspended particulate matter (SPM) or 3.5-52.8 ng/L in surface waters. Total particulate mercury content (THg(p)) was positively correlated with (SPM), indicating that mercury in tidal waters is mostly associated with (SPM), and that tidal variations of total particulate mercury are mainly due to changes in (SPM) content throughout the tidal cycle. Maximum values for THg(p) were observed during mid-flood and mid-ebb, while the lowest values were determined at low tide and high tide. These data suggest that there are no mercury point sources in the Jade Bay. Moreover, the THg(p) content at low tide and high tide were significantly lower than the values recorded in the bottom sediment of the sampling site (>200 ng/g DW), while THg(p) content during the mid-flood and mid-ebb were comparable to the THg content in the surface bottom sediments. Therefore, changes in THg(p) content in the water column due to tidal forcing may have resulted from re-suspension of underlying surface sediments with relatively high mercury content.

Stratigraphic response of salt marshes to slow rates of sea-level change

NASA Astrophysics Data System (ADS)

Daly, J.; Bell, T.

2006-12-01

Conventional models of salt-marsh development show an idealized spatial relationship between salt-marsh floral and foraminiferal zones, where the landward margin of the marsh gradually migrates inland in response to sea-level rise. This model predicts that transgression will result in persistent and possibly expanded salt marshes at the surface, depending on a variety of factors including sediment supply, hydrologic conditions, tidal range, and rate of sea-level rise. However, in areas with abundant sediment supply and slow rates of sea- level rise, the extent of back-barrier salt marshes may decline over time as the barrier-spits mature. Sea level around the northeast coast of Newfoundland is rising at a very slow rate during the late Holocene (<0.5 mm/yr). Sandy barrier-spits and tombolos are common coastal features, but salt marshes are rare. The generalized stratigraphy of dutch cores collected in back-barrier settings in this region is a surface layer of sphagnum peat with abundant woody roots, underlain by sedge-dominated peat that transitions gradually to a thin layer of Juncus sp. peat with agglutinated foraminifera, dominantly Jadammina macrescens and Balticammina pseudomacrescens. These basal peats are interpreted as salt-marsh peats, characterized by the presence of foraminifera that are absent in overlying peat units. This sequence indicates that salt marshes developed in back-barrier environments during the initial stages of barrier progradation, then gradually transitioned to environments increasingly dominated by freshwater flora. These transitions are interpreted to reflect the progradation of the spit, decreased tidal exchange in the back-barrier, and increased influence of freshwater streams discharging into the back-barrier setting. Decreased marine influence on the back-barrier environment leads to a floral and faunal shift associated with a regressive stratigraphy in an area experiencing sea-level rise. For studies of Holocene sea-level change

Intestinal barrier function of Atlantic salmon (Salmo salar L.) post smolts is reduced by common sea cage environments and suggested as a possible physiological welfare indicator

PubMed Central

2010-01-01

Background Fish farmed under high intensity aquaculture conditions are subjected to unnatural environments that may cause stress. Therefore awareness of how to maintain good health and welfare of farmed fish is important. For Atlantic salmon held in sea cages, water flow, dissolved oxygen (DO) levels and temperature will fluctuate over time and the fish can at times be exposed to detrimentally low DO levels and high temperatures. This experimental study investigates primary and secondary stress responses of Atlantic salmon post smolts to long-term exposure to reduced and fluctuating DO levels and high water temperatures, mimicking situations in the sea cages. Plasma cortisol levels and cortisol release to the water were assessed as indicators of the primary stress response and intestinal barrier integrity and physiological functions as indicators of secondary responses to changes in environmental conditions. Results Plasma cortisol levels were elevated in fish exposed to low (50% and 60% saturation) DO levels and low temperature (9°C), at days 9, 29 and 48. The intestinal barrier function, measured as electrical resistance (TER) and permeability of mannitol at the end of the experiment, were reduced at 50% DO, in both proximal and distal intestine. When low DO levels were combined with high temperature (16°C), plasma cortisol levels were elevated in the cyclic 1:5 h at 85%:50% DO group and fixed 50% DO group compared to the control (85% DO) group at day 10 but not at later time points. The intestinal barrier function was clearly disturbed in the 50% DO group; TER was reduced in both intestinal regions concomitant with increased paracellular permeability in the distal region. Conclusions This study reveals that adverse environmental conditions (low water flow, low DO levels at low and high temperature), that can occur in sea cages, elicits primary and secondary stress responses in Atlantic salmon post smolts. The intestinal barrier function was significantly

Intestinal barrier function of Atlantic salmon (Salmo salar L.) post smolts is reduced by common sea cage environments and suggested as a possible physiological welfare indicator.

PubMed

Sundh, Henrik; Kvamme, Bjørn Olav; Fridell, Frode; Olsen, Rolf Erik; Ellis, Tim; Taranger, Geir Lasse; Sundell, Kristina

2010-11-09

Fish farmed under high intensity aquaculture conditions are subjected to unnatural environments that may cause stress. Therefore awareness of how to maintain good health and welfare of farmed fish is important. For Atlantic salmon held in sea cages, water flow, dissolved oxygen (DO) levels and temperature will fluctuate over time and the fish can at times be exposed to detrimentally low DO levels and high temperatures. This experimental study investigates primary and secondary stress responses of Atlantic salmon post smolts to long-term exposure to reduced and fluctuating DO levels and high water temperatures, mimicking situations in the sea cages. Plasma cortisol levels and cortisol release to the water were assessed as indicators of the primary stress response and intestinal barrier integrity and physiological functions as indicators of secondary responses to changes in environmental conditions. Plasma cortisol levels were elevated in fish exposed to low (50% and 60% saturation) DO levels and low temperature (9°C), at days 9, 29 and 48. The intestinal barrier function, measured as electrical resistance (TER) and permeability of mannitol at the end of the experiment, were reduced at 50% DO, in both proximal and distal intestine. When low DO levels were combined with high temperature (16°C), plasma cortisol levels were elevated in the cyclic 1:5 h at 85%:50% DO group and fixed 50% DO group compared to the control (85% DO) group at day 10 but not at later time points. The intestinal barrier function was clearly disturbed in the 50% DO group; TER was reduced in both intestinal regions concomitant with increased paracellular permeability in the distal region. This study reveals that adverse environmental conditions (low water flow, low DO levels at low and high temperature), that can occur in sea cages, elicits primary and secondary stress responses in Atlantic salmon post smolts. The intestinal barrier function was significantly affected by prolonged hypoxic stress

Dietary Cerebroside from Sea Cucumber (Stichopus japonicus): Absorption and Effects on Skin Barrier and Cecal Short-Chain Fatty Acids.

PubMed

Duan, Jingjing; Ishida, Marina; Aida, Kazuhiko; Tsuduki, Tsuyoshi; Zhang, Jin; Manabe, Yuki; Hirata, Takashi; Sugawara, Tatsuya

2016-09-21

Sphingolipids from marine sources have attracted more attention recently because of their distinctive structures and expected functions. In this study, the content and components of cerebroside from sea cucumber Stichopus japonicus were analyzed. The absorption of cerebroside from S. japonicus was investigated with an in vivo lipid absorption assay. The result revealed that S. japonicus is a rich source of cerebroside that contained considerable amounts of odd carbon chain sphingoid bases. The cumulative recoveries of d17:1- and d19:2-containing cerebrosides were 0.31 ± 0.16 and 0.32 ± 0.10%, respectively, for 24 h after administration. To the best of the authors' knowledge, this is the first work that shows sphingolipids from a marine source could be absorbed in vivo and incorporated into ceramides. In addition, dietary supplementation with sea cucumber cerebroside to hairless mouse improved the skin barrier function and increased short-chain fatty acids in cecal contents, which have shown beneficial effects on the host.

Barrier Effect of the Indo-Pacific Maritime Continent on the MJO

NASA Astrophysics Data System (ADS)

Ling, Jian; Zhang, Chidong

2017-04-01

Explanations for the barrier effect of the Indo-Pacific Maritime Continent (MC) on the MJO should satisfy two criteria. First, they should include specific features of the MC, namely, its intricate land-sea distributions and elevated terrains. Second, they should include mechanisms for both the barrier effect and its overcoming by some MJO events. Guided by these two criteria, we applied a precipitation-tracking method to identify MJO events that propagate across the MC (MJO-C) and those that are blocked by the MC (MJO-B). About a half of MJO events that form over the Indian Ocean propagate through the MC. Most of them (> 75%) become weakened over the MC. The barrier effect cannot be explained in terms of the strength, horizontal scale, or spatial distribution of MJO convection when it approaches the MC from the west. A distinction between MJO-B and MJO-C is their precipitation over the sea vs. land in the MC region. MJO-C events rain more over the sea than over land, whereas land rainfall dominates for MJO-B. This suggests that inhibiting convective development over the sea could be a possible mechanism for the barrier effect of the MC. Preceding conditions for MJO-C include stronger low-level zonal moisture flux convergence and higher SST higher in the MC region. Possible connections between these large-scale conditions and the land vs. sea distributions of MJO rainfall through the diurnal cycle are discussed.

A Bayesian Network to Predict Barrier Island Geomorphologic Characteristics

NASA Astrophysics Data System (ADS)

Gutierrez, B.; Plant, N. G.; Thieler, E. R.; Turecek, A.; Stippa, S.

2014-12-01

Understanding how barrier islands along the Atlantic and Gulf coasts of the United States respond to storms and sea-level rise is an important management concern. Although these threats are well recognized, quantifying the integrated vulnerability is challenging due to the range of time and space scalesover which these processes act. Developing datasets and methods to identify the physical vulnerabilities of coastal environments due to storms and sea-level rise thus is an important scientific focus that supports land management decision making. Here we employ a Bayesian Network (BN) to model the interactions between geomorphic variables sampled from existing datasets that capture both storm-and sea-level rise related coastal evolution. The BN provides a means of estimating probabilities of changes in specific geomorphic characteristics such as foredune crest height, beach width, beach height, given knowledge of barrier island width, maximum barrier island elevation, distance from an inlet, the presence of anthropogenic modifications, and long-term shoreline change rates, which we assume to be directly related to sea-level rise. We evaluate BN skill and explore how different constraints, such as shoreline change characteristics (eroding, stable, accreting), distance to nearby inlets and island width, affect the probability distributions of future morphological characteristics. Our work demonstrates that a skillful BN can be constructed and that factors such as distance to inlet, shoreline change rate, and the presence of human alterations have the strongest influences on network performance. For Assateague Island, Maryland/Virginia, USA, we find that different shoreline change behaviors affect the probabilities of specific geomorphic characteristics, such as dune height, which allows us to identify vulnerable locations on the barrier island where habitat or infrastructure may be vulnerable to storms and sea-level rise.

Abundance and diversity of anemonefishes and their host sea anemones at two mesophotic sites on the Great Barrier Reef, Australia

NASA Astrophysics Data System (ADS)

Bridge, T.; Scott, A.; Steinberg, D.

2012-12-01

Anemonefishes and their host sea anemones are iconic inhabitants of coral reef ecosystems. While studies have documented their abundance in shallow-water reef habitats in parts of the Indo-Pacific, none have examined these species on mesophotic reefs. In this study, we used autonomous underwater vehicle imagery to examine the abundance and diversity of anemones and anemonefishes at Viper Reef and Hydrographers Passage in the central Great Barrier Reef at depths between 50 and 65 m. A total of 37 host sea anemones (31 Entacmaea quadricolor and 6 Heteractis crispa) and 24 anemonefishes (23 Amphiprion akindynos and 1 A. perideraion) were observed. Densities were highest at Viper Reef, with 8.48 E. quadricolor and A. akindynos per 100 m2 of reef substratum. These results support the hypothesis that mesophotic reefs have many species common to shallow-water coral reefs and that many taxa may occur at depths greater than currently recognised.

A sea water barrier to coral gene flow.

PubMed

Lessios, H A

2012-11-01

Land is not the only barrier to dispersal encountered by marine organisms. For sedentary shallow water species, there is an additional, marine barrier, 5000 km of uninterrupted deep-water stretch between the central and the eastern Pacific. This expanse of water, known as the ‘Eastern Pacific Barrier’, has been separating faunas of the two oceanic regions since the beginning of the Cenozoic. Species with larvae that cannot stay in the plankton for the time it takes to cross between the two sides have been evolving independently. That the eastern Pacific does not share species with the rest of the Pacific was obvious to naturalists two centuries ago (Darwin 1860). Yet, this rule has exceptions. A small minority of species are known to straddle the Eastern Pacific Barrier. One such exception is the scleractinian coral Porites lobata (Fig. 1). This species is spread widely throughout the Indo-Pacific, where it is one of the major reef-builders, but it is also encountered in the eastern Pacific. Are eastern and central Pacific populations of this coral connected by gene flow? In this issue of Molecular Ecology, Baums et al. (2012) use microsatellite data to answer this question. They show that P. lobata populations in the eastern Pacific are cut off from genetic influx from the rest of the Pacific. Populations within each of the two oceanic regions are genetically connected (though those in the Hawaiian islands are also isolated). Significantly, the population in the Clipperton Atoll, the westernmost island in the eastern Pacific, genetically groups with populations from the central Pacific, suggesting that crossing the Eastern Pacific Barrier by P. lobata propagules does occasionally occur.

Sea lamprey abundance and management in Lake Superior 1957-1999

USGS Publications Warehouse

Heinrich, John W.; Mullett, Katherine M.; Hansen, Michael J.; Adams, Jean V.; Klar, Gerald T.; Johnson, David A.; Christie, Gavin C.; Young, Robert J.

2003-01-01

The international sea lamprey (Petromyzon marinus) control program successfully laid the foundation for rehabilitation of lake trout (Salvelinus namaycush) in Lake Superior and was well coordinated among management agencies during 1957–1999. The lampricide TFM was the primary control tool, with recurring treatments in 52 larval-producing streams. Barriers and sterile-male-release, as alternative control technologies, were significant elements of the program. Barriers blocked spawning sea lampreys from substantial areas of habitat for sea lamprey larvae during 1966–1999, and the sterile-male-release technique was used to reduce larval production during 1991–1996. Sea lamprey control resulted in the suppression of sea lamprey populations in Lake Superior, as evidenced by the linear decline in spawner abundance during 1962–1999. However, sea lamprey abundance was not as low as the targets specified in the fish community objectives. Most of the parasitic sea lampreys in Lake Superior probably originated from survivors of lampricide treatments. Self-sustaining populations of lake trout were restored in most of the lake by 1996, although many were killed annually by sea lampreys. Economic injury levels for damage to fish populations by sea lampreys are being developed and will be used to distribute sea lamprey control resources among the Great Lakes.

A coral reef refuge in the Red Sea.

PubMed

Fine, Maoz; Gildor, Hezi; Genin, Amatzia

2013-12-01

The stability and persistence of coral reefs in the decades to come is uncertain due to global warming and repeated bleaching events that will lead to reduced resilience of these ecological and socio-economically important ecosystems. Identifying key refugia is potentially important for future conservation actions. We suggest that the Gulf of Aqaba (GoA) (Red Sea) may serve as a reef refugium due to a unique suite of environmental conditions. Our hypothesis is based on experimental detection of an exceptionally high bleaching threshold of northern Red Sea corals and on the potential dispersal of coral planulae larvae through a selective thermal barrier estimated using an ocean model. We propose that millennia of natural selection in the form of a thermal barrier at the southernmost end of the Red Sea have selected coral genotypes that are less susceptible to thermal stress in the northern Red Sea, delaying bleaching events in the GoA by at least a century. © 2013 John Wiley & Sons Ltd.

The dynamics of biogeographic ranges in the deep sea.

PubMed

McClain, Craig R; Hardy, Sarah Mincks

2010-12-07

Anthropogenic disturbances such as fishing, mining, oil drilling, bioprospecting, warming, and acidification in the deep sea are increasing, yet generalities about deep-sea biogeography remain elusive. Owing to the lack of perceived environmental variability and geographical barriers, ranges of deep-sea species were traditionally assumed to be exceedingly large. In contrast, seamount and chemosynthetic habitats with reported high endemicity challenge the broad applicability of a single biogeographic paradigm for the deep sea. New research benefiting from higher resolution sampling, molecular methods and public databases can now more rigorously examine dispersal distances and species ranges on the vast ocean floor. Here, we explore the major outstanding questions in deep-sea biogeography. Based on current evidence, many taxa appear broadly distributed across the deep sea, a pattern replicated in both the abyssal plains and specialized environments such as hydrothermal vents. Cold waters may slow larval metabolism and development augmenting the great intrinsic ability for dispersal among many deep-sea species. Currents, environmental shifts, and topography can prove to be dispersal barriers but are often semipermeable. Evidence of historical events such as points of faunal origin and climatic fluctuations are also evident in contemporary biogeographic ranges. Continued synthetic analysis, database construction, theoretical advancement and field sampling will be required to further refine hypotheses regarding deep-sea biogeography.

How to structure and prioritize information needs in support of monitoring design for Integrated Coastal Management

NASA Astrophysics Data System (ADS)

Vugteveen, Pim; van Katwijk, Marieke M.; Rouwette, Etiënne; Hanssen, Lucien

2014-02-01

Integrated Coastal Management cannot operate effectively without reliable information and knowledge on changes in the environment and on the causes of those changes. Monitoring is essential to provide data needed for a real understanding of socio-economic and ecological functioning in multi-user nature areas. We present a web-based and comprehensive assessment methodology to articulate, structure and prioritize information needs and ensuing monitoring needs. We applied this methodology in the Dutch Wadden Sea Region, which includes a designated UNESCO World Heritage nature reserve. The methodology consists of the following steps: i) exploring social-ecological issues of concern and defining the monitoring scope; ii) articulating information needs expressed as tractable questions; iii) elaborating monitoring needs; iv) grounding in scientific models and current monitoring; v) synthesizing assessment findings into target entities, i.e. analysis variables for monitoring. In this paper we focus on the first three steps. As part of our methodology we performed two online surveys amongst a broad range of stakeholders and amongst monitoring professionals. In the case of the Dutch Wadden Sea Region, main monitoring questions were related to biodiversity and food web relations; effects of fisheries and its pressures on the ecosystem; channel and port dredging; spatial planning and multifunctional use; sustainable energy production; and effects of changing storm regimes due to climate change. Subsequently we elaborated these general issues into analysis variables within five themes. The presented methodology enables large scale and unbiased involvement of stakeholders in articulating information needs in a multi-user nature reserve like the Wadden Sea. In addition the methodology facilitates the input and feedback of monitoring professionals by providing a detailed elaboration of monitoring needs.

Effects of Mackenzie River Discharge and Bathymetry on Sea Ice in the Beaufort Sea

NASA Technical Reports Server (NTRS)

Nghiem, S. V.; Hall, D. K.; Rigor, I. G; Li, P.; Neumann, G.

2014-01-01

Mackenzie River discharge and bathymetry effects on sea ice in the Beaufort Sea are examined in 2012 when Arctic sea ice extent hit a record low. Satellite-derived sea surface temperature revealed warmer waters closer to river mouths. By 5 July 2012, Mackenzie warm waters occupied most of an open water area about 316,000 sq km. Surface temperature in a common open water area increased by 6.5 C between 14 June and 5 July 2012, before and after the river waters broke through a recurrent landfast ice barrier formed over the shallow seafloor offshore the Mackenzie Delta. In 2012, melting by warm river waters was especially effective when the strong Beaufort Gyre fragmented sea ice into unconsolidated floes. The Mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the Arctic Ocean, constituting a stark contrast to the Antarctic that has no such rivers to affect sea ice.

Seroepidemiology of arboviruses among seabirds and island residents of the Great Barrier Reef and Coral Sea.

PubMed

Humphery-Smith, I; Cybinski, D H; Byrnes, K A; St George, T D

1991-10-01

Duplicate neutralization tests were done on 401 avian and 101 human sera from island residents collected in the Coral Sea and on Australia's Great Barrier Reef against 19 known arboviruses. Antibodies to a potentially harmful flavivirus, Gadget's Gully virus, were equally present (4%) in both avian and human sera. Antibodies to another flavivirus, Murray Valley Encephalitis, and an ungrouped isolate, CSIRO 1499, were also present in both populations with non-significantly different incidences. Antibodies to Upolu, Johnston Atoll, Lake Clarendon, Taggert, Saumarez Reef and CSIRO 264 viruses were restricted to seabirds. Island residents with antibodies to Ross River and Barmah Forest viruses are thought to have been exposed to these viruses on the mainland as antibody to both viruses was absent among seabirds. These results indicate that consideration should be given to tick-associated arboviruses as potential public health hazards on islands where both seabird and human activities interact.

Contrasts in Arctic shelf sea-ice regimes and some implications: Beaufort Sea versus Laptev Sea

USGS Publications Warehouse

Reimnitz, E.; Dethleff, D.; Nurnberg, D.

1994-01-01

The winter ice-regime of the 500 km) from the mainland than in the Beaufort Sea. As a result, the annual freeze-up does not incorporate old, deep-draft ice, and with a lack of compression, such deep-draft ice is not generated in situ, as on the Beaufort Sea shelf. The Laptev Sea has as much as 1000 km of fetch at the end of summer, when freezing storms move in and large (6 m) waves can form. Also, for the first three winter months, the polynya lies inshore at a water depth of only 10 m. Turbulence and freezing are excellent conditions for sediment entrainment by frazil and anchor ice, when compared to conditions in the short-fetched Beaufort Sea. We expect entrainment to occur yearly. Different from the intensely ice-gouged Beaufort Sea shelf, hydraulic bedforms probably dominate in the Laptev Sea. Corresponding with the large volume of ice produced, more dense water is generated in the Laptev Sea, possibly accompanied by downslope sediment transport. Thermohaline convection at the midshelf polynya, together with the reduced rate of bottom disruption by ice keels, may enhance benthic productivity and permit establishment of open-shelf benthic communities which in the Beaufort Sea can thrive only in the protection of barrier islands. Indirect evidence for high benthic productivity is found in the presence of walrus, who also require year-round open water. By contrast, lack of a suitable environment restricts walrus from the Beaufort Sea, although over 700 km farther to the south. We could speculate on other consequences of the different ice regimes in the Beaufort and Laptev Seas, but these few examples serve to point out the dangers of exptrapolating from knowledge gained in the North American Arctic to other shallow Arctic shelf settings. ?? 1994.

The dynamics of biogeographic ranges in the deep sea

PubMed Central

McClain, Craig R.; Hardy, Sarah Mincks

2010-01-01

Anthropogenic disturbances such as fishing, mining, oil drilling, bioprospecting, warming, and acidification in the deep sea are increasing, yet generalities about deep-sea biogeography remain elusive. Owing to the lack of perceived environmental variability and geographical barriers, ranges of deep-sea species were traditionally assumed to be exceedingly large. In contrast, seamount and chemosynthetic habitats with reported high endemicity challenge the broad applicability of a single biogeographic paradigm for the deep sea. New research benefiting from higher resolution sampling, molecular methods and public databases can now more rigorously examine dispersal distances and species ranges on the vast ocean floor. Here, we explore the major outstanding questions in deep-sea biogeography. Based on current evidence, many taxa appear broadly distributed across the deep sea, a pattern replicated in both the abyssal plains and specialized environments such as hydrothermal vents. Cold waters may slow larval metabolism and development augmenting the great intrinsic ability for dispersal among many deep-sea species. Currents, environmental shifts, and topography can prove to be dispersal barriers but are often semipermeable. Evidence of historical events such as points of faunal origin and climatic fluctuations are also evident in contemporary biogeographic ranges. Continued synthetic analysis, database construction, theoretical advancement and field sampling will be required to further refine hypotheses regarding deep-sea biogeography. PMID:20667884

When Might Barrier Island Chains 'Collapse'? An Initial Model Investigation

NASA Astrophysics Data System (ADS)

Slott, J. M.; Murray, A. B.

2007-12-01

There has been recent speculation that, in response to the accelerated sea-level rise and intensified storms expected over the coming century, barrier island chains such as those found on the US Atlantic and Gulf coastlines, could develop large (10-kilometer-scale) gaps in their most narrow stretches, or might disappear completely (Riggs, S. R., 2001). Such a collapse along the North Carolina Outer Banks barrier island chain, for example, would leave the mainland vulnerable to direct hits from Western Atlantic storm systems, and also would dramatically alter the estuarine system it encloses with potentially devastating effects to marine life. Concern for the future of the Outer Banks is also motivated by the decimation of the Chandeleur Islands in 2005 from Hurricane Katrina. We will present a series of initial numerical modeling experiments addressing how barrier island morphodynamics respond to the sudden creation of kilometer-scale gaps. Large-scale barrier island evolution is influenced by sea-level rise and barrier island overwash, alongshore sediment transport, tidal currents, and the availability of mobile sediment. Barrier islands transgress towards the mainland in response to sea-level rise through overwash: ocean-facing shorelines provide sediment that is transported onto the island to maintain its subaerial height and behind the island to maintain its width, while gradients in alongshore sediment transport typically dictate the large-scale shape of a coastline over long time frames (decades to millenia). Tidal currents also tend to scour inlet channels; the relative strength of this effect depends in part upon the width of the inlet channel. Our exploratory model includes both a one-line alongshore transport component and a cross-shore overwash component, as well as representations of underlying geology (weathering rates and material compositions). In our modeling experiments, we test the effects of perforating a 30 km barrier island chain with variable

Postglacial Fringing-Reef to Barrier-Reef conversion on Tahiti links Darwin's reef types

NASA Astrophysics Data System (ADS)

Blanchon, Paul; Granados-Corea, Marian; Abbey, Elizabeth; Braga, Juan C.; Braithwaite, Colin; Kennedy, David M.; Spencer, Tom; Webster, Jody M.; Woodroffe, Colin D.

2014-05-01

In 1842 Charles Darwin claimed that vertical growth on a subsiding foundation caused fringing reefs to transform into barrier reefs then atolls. Yet historically no transition between reef types has been discovered and they are widely considered to develop independently from antecedent foundations during glacio-eustatic sea-level rise. Here we reconstruct reef development from cores recovered by IODP Expedition 310 to Tahiti, and show that a fringing reef retreated upslope during postglacial sea-level rise and transformed into a barrier reef when it encountered a Pleistocene reef-flat platform. The reef became stranded on the platform edge, creating a lagoon that isolated it from coastal sediment and facilitated a switch to a faster-growing coral assemblage dominated by acroporids. The switch increased the reef's accretion rate, allowing it to keep pace with rising sea level, and transform into a barrier reef. This retreat mechanism not only links Darwin's reef types, but explains the re-occupation of reefs during Pleistocene glacio-eustacy.

Looking Back to the Future: Insight on Anthropocene beaches from Holocene and Pleistocene barriers

NASA Astrophysics Data System (ADS)

Dougherty, A. J.; Choi, J. H.; Turney, C. S.; Dosseto, A.

2017-12-01

`Super' storms and accelerated rates of sea-level rise are forecast in the Anthropocene, but how coasts will respond (or even if they have started to be impacted) remain uncertain. The onset of this new anthropogenic age is considered mid-1900s when multiple indices including sea level exceed previous Holocene measurements. Centuries of sea surface elevation data, used to project an increase of up to 2m by 2100, show that the current rise started 200 years ago. Similar records of storms or shoreline evolution over these centennial time-scales do not exist. With empirical studies of coastal morphodynamics concentrated during decades of accelerated sea-level rise, present-day beaches can be considered Anthropocene features. To determine the future of vulnerable sandy shorelines, climate change scenarios of increased sea level and storm intensity have been combined with computer models integrating short-term process data with large-scale coastal evolution. The uncertainty in these models can be reduced with longer sea level and storm records as well as filling the gap between detailed beach profile/wave buoy data and generalized barrier stratigraphy. High-resolution chronostratigraphic models necessary to achieve this can be constructed using Light Detection And Ranging (LiDAR), Ground Penetrating Radar (GPR), and Optically Stimulated Luminescence (OSL). Combined GPR, OSL and LiDAR (GOaL) on prograded barriers enables analysis of shorelines back through time, by comparing behaviour since the onset of anthropogenic global warming to that in the preceding millennia. Extracting a record of coastal evolution prior to and since seas began to rise two centuries ago offers the opportunity to detect any difference indicating if/how shorelines have responded. In double barrier systems with composite Holocene and Pleistocene components GOaL can extend the Anthropocene record back to when seas were known to have been higher than today. To demonstrate the potential of GOaL, data

Shifting baselines in the Ems Dollard estuary: A comparison across three decades reveals changing benthic communities

NASA Astrophysics Data System (ADS)

Compton, Tanya J.; Holthuijsen, Sander; Mulder, Maarten; van Arkel, Maarten; Schaars, Loran Kleine; Koolhaas, Anita; Dekinga, Anne; ten Horn, Job; Luttikhuizen, Pieternella C.; van der Meer, Jaap; Piersma, Theunis; van der Veer, Henk W.

2017-09-01

At a time when there is a growing discussion about the natural state of estuaries, a comparison of macrozoobenthos communities from two surveys conducted 30 years apart in the Ems Dollard estuary, in the eastern Wadden Sea, The Netherlands, provides a unique opportunity to compare changes over time. As expected, our comparison revealed a gradient in species composition from land (the Dollard) to sea (the Outer Ems) at both points in time, with brackish species in the Dollard and more marine species in the Outer Ems (Wadden Sea). Total richness increased over time; however, this mainly reflected the immigration of new species and sampling differences. In the Dollard, total biomass declined over time, most likely reflecting de-eutrophication in this area. Strikingly, at the meeting point between the sea and the brackish Dollard, i.e. the Inner Ems, the community composition changed from one dominated by bivalves (1970s) to one dominated by worms (since 2009). This change involved a reduction in total biomass, mainly of Mya arenaria, and immigration of polychaete worms (Marenzellaria viridis and Alitta succinea). In the Outer Ems, an increase in total biomass was observed, associated with the recent successful recruitment of Cerastoderma edule. This comparison highlights that historical data provides useful insights at large spatial scales. However, a full understanding of the complex dynamics of estuaries requires an analysis of continuous long-term monitoring series.

GODAE Inter-Comparisons in the Tasman and Coral Seas

DTIC Science & Technology

2012-08-01

sea surface temperature analysis over the Australian region. Submitted. 27. Steinberg C. 2007. Impacts of climate change on the physical...oceanography of the Great Barrier Reef. In: Climate Change and the Great Barrier Reef, Johnson JE and Marshall PA (eds), pp51–74, Great Barrier Reef Mar. Park...GB Brassington2, J Cummings3, M Martin4, F Hernandez5 1The Centre for Australian Weather and Climate Research (CAWCR), Commonwealth Scientific and

Morphology and stratigraphy of small barrier-lagoon systems in Maine

USGS Publications Warehouse

Duffy, W.; Belknap, D.F.; Kelley, J.T.

1989-01-01

The coast of Maine contains over 200 individual barrier-lagoon systems, most quite small, with an aggregate length of nearly 100 km. Although they represent less than 5% of the tidally influenced coastline of Maine, they are widely distributed and occur in a variety of dynamic regimes and physiographic regions. Their morphology and backbarrier stratigraphy are different from better studied coastal plain systems, and provide important clues to the Holocene evolution of the Maine coast. In a study of geomorphic form and backbarrier stratigraphy, inlet processes and Holocene sea-level rise have been identified as the principal controls on coarse-grained barrier stratigraphy. Barriers in Maine are found in five distinct geomorphic forms, identified herein as: barrier spits, pocket barriers, double tombolos, cuspate barriers and looped barriers. The few long sandy beaches in southwestern Maine are mostly barrier spits. The remainder of the barrier types is composed primarily of gravel or mixed sand and gravel. The barriers protect a variety of backbarrier environments: fresh and brackish ponds, lagoons and fresh- and saltwater marshes. The barriers may or may not have inlets. Normal wave action, coarse-grain size and a deeply embayed coast result in barriers with steep, reflective profiles several meters above MHW. Occasional storm events completely wash over the barriers, building steep, lobate gravel fans along their landward margin. Few, if any, extensive storm layers are recognized as extending into the distal backbarrier environments, however. During sea-level rise and landward barrier retreat, this abrupt, storm-generated transition zone inters the backbarrier sediments. Statistical comparisons of barrier morphology, location and backbarrier environment type with backbarrier stratigraphy show that Holocene backbarrier stratigraphy is best predicted by the modern backbarrier environment type. This, in turn, is influenced most by the absence or presence, and long

Water level response in back-barrier bays unchanged following Hurricane Sandy

USGS Publications Warehouse

Aretxabaleta, Alfredo L.; Butman, Bradford; Ganju, Neil K.

2014-01-01

On 28–30 October 2012, Hurricane Sandy caused severe flooding along portions of the northeast coast of the United States and cut new inlets across barrier islands in New Jersey and New York. About 30% of the 20 highest daily maximum water levels observed between 2007 and 2013 in Barnegat and Great South Bay occurred in 5 months following Hurricane Sandy. Hurricane Sandy provided a rare opportunity to determine whether extreme events alter systems protected by barrier islands, leaving the mainland more vulnerable to flooding. Comparisons between water levels before and after Hurricane Sandy at bay stations and an offshore station show no significant differences in the transfer of sea level fluctuations from offshore to either bay following Sandy. The post-Hurricane Sandy bay high water levels reflected offshore sea levels caused by winter storms, not by barrier island breaching or geomorphic changes within the bays.

Chattonella and Fibrocapsa (Raphidophyceae): First observation of, potentially harmful, red tide organisms in Dutch coastal waters

NASA Astrophysics Data System (ADS)

Vrieling, E. G.; Koeman, R. P. T.; Nagasaki, K.; Ishida, Y.; Pererzak, L.; Gieskes, W. W. C.; Veenhuis, M.

Species of the potentially toxic and red-tide-forming marine-phytoplankton genera Chattonella and Fibrocapsa (Raphidophyceae) were observed for the first time in 1991 in samples taken in Dutch coastal waters; they were again recorded and enumerated in the following years. Chattonella spp. cell numbers varied with the season, with a maximum in May or June in the Dutch Wadden Sea. Cell numbers of Chattonella and F. japonica Toriumi et Takano were up to 6.0·10 3 cells·dm -3 in the Dutch Wadden Sea, except at one station in June 1993 when over 10 4 cells·dm -3Chattonella were counted. In May 1993, a minor bloom (over 2.0·10 5 cells·dm -3) was observed at a station in the southern central North Sea, 100 km northwest of the island of Terschelling. The potentially neurotoxic species Chattonella marina (Subrahmanyan) Hara et Chihara was identified and discriminated from morphologically related species within the class of Raphidophyceae by immunofluorescence. F. japonica could only be clearly identified in live samples; in fixed samples cell morphology was severely affected. The identification of this species was supported by the presence of mucocysts, structures that can be observed readily by optical and electron microscopy.

Dynamics behind warming of the southeastern Arabian Sea and its interruption based on in situ measurements

NASA Astrophysics Data System (ADS)

Mathew, Simi; Natesan, Usha; Latha, Ganesan; Venkatesan, Ramasamy

2018-05-01

A study of the inter-annual variability of the warming of the southeastern Arabian Sea (SEAS) during the spring transition months was carried out from 2013 to 2015 based on in situ data from moored buoys. An attempt was made to identify the roles of the different variables in the warming of the SEAS (e.g., net heat flux, advection, entrainment, and thickness of the barrier layer during the previous northeast monsoon season). The intense freshening of the SEAS (approximately 2 PSU) occurring in each December, together with the presence of a downwelling Rossby wave, supports the formation of a thick barrier layer during the northeast monsoon season. It is known that the barrier layer thickness, varying each year, plays a major role in the spring warming of the SEAS. Interestingly, an anomalously thick barrier layer occurred during the northeast monsoon season of 2012-2013. However, the highest sea surface temperature (31 °C) was recorded during the last week of April 2015, while the lowest sea surface temperature (29.7 °C) was recorded during the last week of May 2013. The mixed layer heat budget analysis during the spring transition months proved that the intense warming has been mainly supported by the net heat flux, not by other factors like advection and entrainment. The inter-annual variability analysis of the net heat flux and its components, averaged over a box region of the SEAS, showed a substantial latent heat flux release and a reduction in net shortwave radiation in 2013. Both factors contributed to the negative net heat flux. Strong breaks in the warming were also observed in May due to the entrainment of cold sub-surface waters. These events are associated with the cyclonic eddy persisting over the SEAS during the same time. The entrainment term, favoring the cooling, was stronger in 2015 than that in 2013 and 2014. The surface temperatures measured in 2013 were lower than those in 2014 and 2015 despite the presence of a thick barrier layer. The

Chasing boundaries and cascade effects in a coupled barrier-marsh-lagoon system

NASA Astrophysics Data System (ADS)

Lorenzo-Trueba, Jorge; Mariotti, Giulio

2017-08-01

The long-term dynamic evolution of an idealized barrier-marsh-lagoon system experiencing sea-level rise is studied by coupling two existing numerical models. The barrier model accounts for the interaction between shoreface dynamics and overwash flux, which allows the occurrence of barrier drowning. The marsh-lagoon model includes both a backbarrier marsh and an interior marsh, and accounts for the modification of the wave regime associated with changes in lagoon width and depth. Overwash, the key process that connects the barrier shoreface with the marsh-lagoon ecosystems, is formulated to account for the role of the backbarrier marsh. Model results show that a number of factors that are not typically associated with the dynamics of coastal barriers can enhance the rate of overwash-driven landward migration by increasing backbarrier accommodation space. For instance, lagoon deepening could be triggered by marsh edge retreat and consequent export of fine sediment via tidal dispersion, as well as by an expansion of inland marshes and consequent increase in accommodation space to be filled in with sediment. A deeper lagoon results in a larger fraction of sediment overwash being subaqueous, which coupled with a slow shoreface response sending sediment onshore can trigger barrier drowning. We therefore conclude that the supply of fine sediments to the back-barrier and the dynamics of both the interior and backbarrier marsh can be essential for maintaining the barrier system under elevated rates of sea-level rise. Our results highlight the importance of considering barriers and their associated backbarriers as part of an integrated system in which sediment is exchanged.

Grain-size based sea-level reconstruction in the south Bohai Sea during the past 135 kyr

NASA Astrophysics Data System (ADS)

Yi, Liang; Chen, Yanping

2013-04-01

and sea level. Nature 324, 137-140. Charman, D.J., Roe, H.M., Roland Gehrels, W., 2002. Modern distribution of saltmarsh testate amoebae: regional variability of zonation and response to environmental variables. Journal of Quaternary Science 17, 387-409. Horton, B.P., 1997. Quantification of the indicative meaning of a range of Holocene sea-level index points from the western North Sea, Department of Geography. University of Durham, Durham City, UK, p. 509. Horton, B.P., Corbett, R., Culver, S.J., Edwards, R.J., Hillier, C., 2006. Modern saltmarsh diatom distributions of the Outer Banks, North Carolina, and the development of a transfer function for high resolution reconstructions of sea level. Estuarine, Coastal and Shelf Science 69, 381-394. IOCAS (Institute of Oceanology, Chinese Academy of Sciences), 1985. Bohai Sea Geology. Science Press, Beijing, China. Madsen, A.T., Murray, A.S., Andersen, T.J., Pejrup, M., 2007. Temporal changes of accretion rates on an estuarine salt marsh during the late Holocene -Reflection of local sea level changes? The Wadden Sea, Denmark. Marine Geology 242, 221-233. Mauz, B., Hassler, U., 2000. Luminescence chronology of Late Pleistocene raised beaches in southern Italy: new data of relative sea-level changes. Marine Geology 170, 187-203. Yi, L., Yu, H.J., Ortiz, J.D., Xu, X.Y., Qiang, X.K., Huang, H.J., Shi, X., Deng, C.L., 2012. A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis. Sedimentary Geology 281, 88-100. Zong, Y., Shennan, I., Combellick, R.A., Hamilton, S.L., Rutherford, M.M., 2003. Microfossil evidence for land movements associated with the AD 1964 Alaska earthquake. The Holocene 13, 7-20.

Frequent non-storm washover of barrier islands, Pacific coast of Colombia

USGS Publications Warehouse

Morton, R.A.; Gonzalez, J.L.; Lopez, G.I.; Correa, I.D.

2000-01-01

Barrier islands of the Pacific coast of Colombia repeatedly experience severe washover even when breaking waves in the eastern Pacific are low and onshore winds are calm. On the barrier island of El Choncho, recent non-storm washover events have breached a new inlet, caused rapid beach retreat, destroyed a shoreline protection structure, and flooded a small village of indigenous people so frequently that it had to be relocated. Barrier washover may be augmented by lowered land elevations associated with earthquake-induced subsidence or long-term beach retreat, but temporally it is most closely associated with a 20 to 30 cm regional increase in sea level caused by El Nino. The contradiction of a tranquil tropical island scene simultaneously disturbed by hostile turbulent washover may be unique at present, but it exemplifies how coastal plains throughout the world would be affected if sea level were to rise rapidly as a result of global warming.

Self-organization and forcing templates in coastal barrier response to storms

NASA Astrophysics Data System (ADS)

Lazarus, E.

2015-12-01

When a storm event pushes water up and over a coastal barrier, cross-shore flow transports sediment from the barrier face to the back-barrier environment. This natural physical process is called "overwash", and "washover" is the sedimentary deposit it forms. Overwash and washover support critical coastal habitats, and enable barriers to maintain their height and width relative to rising sea level. On developed barrier coasts, overwash constitutes a natural hazard, which sea-level rise will exacerbate. Overwash is also a prerequisite for barrier breaching and coastal flooding. Predicting occurrence and characteristics of overwash and washover has significant societal value. Hazard models typically assume that pre-storm barrier morphology determines how the barrier changes during a storm. However, classic work has documented the absence of a relationship between pre/post-storm topography in some cases, and has also identified rhythmic patterns in washover alongshore. Previous explanations for these spatial patterns have looked to forcing templates, forms that get imprinted in the barrier shape. An alternative explanation is that washover patterns self-organize, emerging from feedbacks between water flow and sediment transport. Self-organization and forcing templates are often framed as mutually exclusive, but patterns likely form across a continuum of conditions. Here, I use data from a new physical experiment to suggest that spatial patterns in washover can self-organize within the limit of a forcing template of some critical "strength", beyond which pre/post-storm morphologies are highly correlated. Quantifying spatial patterns in washover deposits opens exciting questions regarding coastal morphodynamic response to storms. Measurement of relative template strength over extended spatial (and temporal) scales has the potential to improve hazard assessment and prediction, particularly where template strength is low and self-organization dominates barrier change.

Joint Doctrine for Barriers, Obstacles, and Mine Warfare

DTIC Science & Technology

1999-02-24

of explosives. Typical tactical examples are barbed wire obstacles and tank ditches. Operational and strategic barriers and obstacles may also be...total of 10 ocean minesweepers, 9 amphibious ships, 6 fleet tugs, 3 salvage ships, and 19 destroyers. Twenty-four CH-53D Sea Stallions from Marine

North-Australian tropical seas circulation study

NASA Technical Reports Server (NTRS)

Burrage, Derek; Coleman, R.; Bode, L.; Inoue, M.

1991-01-01

This investigation is intended to fully address the stated objective of the TOPEX/POSEIDON mission (National Aeronautics and Space Administration, 1986). Hence, we intend to use TOPEX/POSEIDON altimetry data to study the large-scale circulation of the Coral Sea Basin and the Arafura Sea and the mass exchange between these and adjoining basins. We will obtain data from two such cruises in 1993 and 1994 and combine them with TOPEX/POSEIDON radar altimetry data to identify interannual and seasonal changes in: (1) the location of the major ocean currents and the South Equatorial Current bifurcation in the Coral Sea; (2) the source region of the South Tropical Counter Current (STCC); and (3) the water exchange between the Coral Sea and the adjoining seas. We will also estimate seasonal and interannual variations in the horizontal transport of mass and heat associated with near-surface geostrophic and wind-driven currents. In addition, the tidal components of the Coral Sea will be studied to provide a correction for altimetry subtidal sea level changes and to develop a regional numerical model for tidal forcing in the Great Barrier Reef (GBR) and Papua New Guinea Reef regions.

Diurnal warming in shallow coastal seas: Observations from the Caribbean and Great Barrier Reef regions

NASA Astrophysics Data System (ADS)

Zhu, X.; Minnett, P. J.; Berkelmans, R.; Hendee, J.; Manfrino, C.

2014-07-01

A good understanding of diurnal warming in the upper ocean is important for the validation of satellite-derived sea surface temperature (SST) against in-situ buoy data and for merging satellite SSTs taken at different times of the same day. For shallow coastal regions, better understanding of diurnal heating could also help improve monitoring and prediction of ecosystem health, such as coral reef bleaching. Compared to its open ocean counterpart which has been studied extensively and modeled with good success, coastal diurnal warming has complicating localized characteristics, including coastline geometry, bathymetry, water types, tidal and wave mixing. Our goal is to characterize coastal diurnal warming using two extensive in-situ temperature and weather datasets from the Caribbean and Great Barrier Reef (GBR), Australia. Results showed clear daily warming patterns in most stations from both datasets. For the three Caribbean stations where solar radiation is the main cause of daily warming, the mean diurnal warming amplitudes were about 0.4 K at depths of 4-7 m and 0.6-0.7 K at shallower depths of 1-2 m; the largest warming value was 2.1 K. For coral top temperatures of the GBR, 20% of days had warming amplitudes >1 K, with the largest >4 K. The bottom warming at shallower sites has higher daily maximum temperatures and lower daily minimum temperatures than deeper sites nearby. The averaged daily warming amplitudes were shown to be closely related to daily average wind speed and maximum insolation, as found in the open ocean. Diurnal heating also depends on local features including water depth, location on different sections of the reef (reef flat vs. reef slope), the relative distance from the barrier reef chain (coast vs. lagoon stations vs. inner barrier reef sites vs. outer rim sites); and the proximity to the tidal inlets. In addition, the influence of tides on daily temperature changes and its relative importance compared to solar radiation was quantified by

Barrier island facies models and recognition criteria

NASA Astrophysics Data System (ADS)

Mulhern, J.; Johnson, C. L.

2017-12-01

Barrier island outcrops record transgressive shoreline motion at geologic timescales, providing integral clues to understanding how coastlines respond to rising sea levels. However, barrier island deposits are difficult to recognize. While significant progress has been made in understanding the modern coastal morphodynamics, this insight is not fully leveraged in existing barrier island facies models. Excellent outcrop exposures of the paralic Upper Cretaceous Straight Cliffs Formation of southern Utah provide an opportunity to revise facies models and recognition criteria for barrier island deposits. Preserved barrier islands are composed of three main architectural elements (shorefaces, tidal inlets, and tidal channels) which occur independently or in combination to create larger-scale barrier island deposits. Barrier island shorefaces record progradation, while barrier island tidal inlets record lateral migration, and barrier island tidal channels record aggradation within the tidal inlet. Four facies associations are used to describe and characterize these barrier island architectural elements. Barrier islands occur in association with backarrier fill and internally contain lower and upper shoreface, high-energy upper shoreface, and tidal channel facies. Barrier islands bound lagoons or estuaries, and are distinguished from other shoreface deposits by their internal facies and geometry, association with backbarrier facies, and position within transgressive successions. Tidal processes, in particular tidal inlet migration and reworking of the upper shoreface, also distinguish barrier island deposits. Existing barrier island models highlight the short term heterogeneous and dynamic nature of barrier island systems, yet overlook processes tied to geologic time scales, such as multi-directional motion, erosion, and reworking, and their expressions in preserved barrier island strata. This study uses characteristic outcrop expressions of barrier island successions to

Recurrence intervals for the closure of the Dutch Maeslant surge barrier

NASA Astrophysics Data System (ADS)

van den Brink, Henk W.; de Goederen, Sacha

2017-09-01

The Dutch Maeslant Barrier, a movable surge barrier in the mouth of the river Rhine, closes when there is a surge in the North Sea and the water level in the river at Rotterdam exceeds 3 m above mean sea level. An important aspect of the failure probability is that the barrier might get damaged during a closure and that, within the time needed for repair, a second critical storm surge may occur. With an estimated closure frequency of once in 10 years, the question of how often the barrier has to be closed twice within one month arises.Instead of tackling this problem by the application of statistical models on the (short) observational series, we solve the problem by combining the surge model WAQUA/DCSMv5 with the output of all seasonal forecasts of the European Centre of Medium-Range Weather Forecasting (ECMWF) in the period 1981-2015, whose combination cumulates in a pseudo-observational series of more than 6000 years.We show that the Poisson process model leads to wrong results as it neglects the temporal correlations that are present on daily, weekly and monthly timescales.By counting the number of double events over a threshold of 2.5 m and assuming that the number of events is exponentially related to the threshold, it is found that two closures occur on average once in 150 years within a month, and once in 330 years within a week. The large uncertainty in these recurrence intervals of more than a factor of two is caused by the sensitivity of the results to the Gumbel parameters of the observed record, which are used for bias correction.Sea level rise has a significant impact on the recurrence time for both single and double closures. The recurrence time of single closures doubles with every 18 cm mean sea level rise (assuming that other influences remain unchanged) and double closures double with every 10 cm rise. This implies a 3-14 times higher probability of a double closure for a 15-40 cm sea level rise in 2050 (according to the KNMI climate scenarios).

Morphology and ecology of the kalyptorhynch Typhlopolycystis rubra (Plathelminthes), an inmate of lugworm burrows in the Wadden Sea

NASA Astrophysics Data System (ADS)

Noldt, U.; Reise, K.

1987-06-01

Typhlopolycystis rubra, a new species of the taxon Polycystididae (Plathelminthes, Kalyptorhynchia), is described. The red species is characterized by copulatory hard structures which consist of a proximal girdle and 2 similar sized stylets. T. rubra occurs in intertidal sand near the island of Sylt in the North Sea. Here, it is virtually confined to the lowest parts of lugworm ( Arenicola marina) burrows, where it aggregates in the coarse grained sand around the feeding pocket areas. This is an extremely narrow spatial niche within the sulfide layer of sediment. Population size over a period of 7 years is the most constant one among all species of Plathelminthes living on the tidal flat. The ability of T. rubra to endure unsuitable conditions inside a cyst may contribute to this remarkably low population variability.

Synthetic Eelgrass Oil Barrier

NASA Astrophysics Data System (ADS)

Curtis, T. G.

2013-05-01

Although surviving in situ micro-organisms eventually consume spilled oil, extensive inundation of shore biota by oil requires cleanup to enable ecological recovery within normal time scales. Although effective in calm seas and quiet waters, oil is advected over and under conventional curtain oil booms by wave actions and currents when seas are running. Most sorbent booms are not reusable, and are usually disposed of in landfills, creating excessive waste. A new concept is proposed for a floating oil barrier, to be positioned off vulnerable coasts, to interdict, contain, and sequester spilled oil, which can then be recovered and the barrier reused. While conventional oil boom designs rely principally on the immiscibility of oil in water and its relative buoyancy, the new concept barrier avoids the pitfalls of the former by taking advantage of the synergistic benefits of numerous fluid and material properties, including: density, buoyancy, elasticity, polarity, and surface area to volume ratio. Modeled after Zostera marina, commonly called eelgrass, the new barrier, referred to as synthetic eelgrass (SE), behaves analogously. Eelgrass has very long narrow, ribbon-like, leaves which support periphyton, a complex matrix of algae and heterotrophic microbes, which position themselves there to extract nutrients from the seawater flowing past them. In an analogous fashion, oil on, or in, seawater, which comes in contact with SE, is adsorbed on the surface and sequestered there. Secured to the bottom, in shoal waters, SE rises to the surface, and, if the tide is low enough, floats on the sea surface down wind, or down current to snare floating oil. The leaves of SE, called filaments, consist of intrinsically buoyant strips of ethylene methyl acrylate, aka EMA. EMA, made of long chain, saturated, hydrocarbon molecules with nearly homogeneous electron charge distributions, is a non-polar material which is oleophilic and hydrophobic. Oil must be in close proximity to the

Characterization of Sea Lamprey stream entry using dual‐frequency identification sonar

USGS Publications Warehouse

McCain, Erin L.; Johnson, Nicholas; Hrodey, Peter J.; Pangle, Kevin L.

2018-01-01

Effective methods to control invasive Sea Lampreys Petromyzon marinus in the Laurentian Great Lakes often rely on knowledge of the timing of the Sea Lamprey spawning migration, which has previously been characterized using data gathered from traps. Most assessment traps are located many kilometers upstream from the river mouth, so less is known about when Sea Lampreys enter spawning streams and which environmental cues trigger their transition from lakes to rivers. To decide how to develop barriers and traps that target Sea Lampreys when they enter a stream, the stream entry of Sea Lampreys into a Lake Huron tributary during 2 years was assessed using dual‐frequency identification sonar (DIDSON). Sea Lampreys entered the stream in low densities when temperatures first reached 4°C, which was up to 6 weeks and a mean of 4 weeks earlier than when they were first captured in traps located upstream. The probability of stream entry was significantly affected by stream temperature and discharge, and stream entry timing peaked when stream temperatures rose to 12°C and discharge was high. Examination of the entry at a finer temporal resolution (i.e., minutes) indicated that Sea Lampreys did not exhibit social behavior (e.g., shoaling) during stream entry. Our findings indicate that Sea Lampreys may be vulnerable to alternative trap types near river mouths and hydraulic challenges associated with traditional traps. Also, seasonal migration barriers near stream mouths may need to be installed soon after ice‐out to effectively block the entire adult Sea Lamprey cohort from upstream spawning habitat.

Sea level driven marsh expansion in a coupled model of marsh erosion and migration

USGS Publications Warehouse

Kirwan, Matthew L.; Walters, David C.; Reay, William G.; Carr, Joel

2016-01-01

Coastal wetlands are among the most valuable ecosystems on Earth, where ecosystem services such as flood protection depend nonlinearly on wetland size and are threatened by sea level rise and coastal development. Here we propose a simple model of marsh migration into adjacent uplands and couple it with existing models of seaward edge erosion and vertical soil accretion to explore how ecosystem connectivity influences marsh size and response to sea level rise. We find that marsh loss is nearly inevitable where topographic and anthropogenic barriers limit migration. Where unconstrained by barriers, however, rates of marsh migration are much more sensitive to accelerated sea level rise than rates of edge erosion. This behavior suggests a counterintuitive, natural tendency for marsh expansion with sea level rise and emphasizes the disparity between coastal response to climate change with and without human intervention.

Strong genetic divergence among populations of a marine fish with limited dispersal, Acanthochromis polyacanthus, within the Great Barrier Reef and the Coral Sea.

PubMed

Planes, S; Doherty, P J; Bernardi, G

2001-11-11

Acanthochromis polyacanthus is an unusual tropical marine damselfish that uniquely lacks pelagic larvae and has lost the capacity for broad-scale dispersal among coral reefs. On the modern Great Barrier Reef (GBR), three color morphs meet and hydridize at two zones of secondary contact. Allozyme electrophoreses revealed strong differences between morphs from the southern zone but few differences between morphs from the northern counterpart, thus suggesting different contact histories. We explore the phylogeography of Acanthochromis polyacanthus with mitochondrial cytochrome b region sequences (alignment of 565 positions) obtained from 126 individuals representing seven to 12 fish from 13 sites distributed over 12 reefs of the GBR and the Coral Sea. The samples revealed three major clades: (1) black fish collected from the southern GBR; (2) bicolored fish collected from the GBR and one reef (Osprey) from the northern Coral Sea; (3) black and white monomorphs collected from six reefs in the Coral Sea. All three clades were well supported (72-100%) by bootstrap analyses. Sequence divergences were very high between the major clades (mean = 7.6%) as well as within them (2.0-3.6%). Within clades, most reefs segregated as monophyletic assemblages. This was revealed both by phylogenetic analyses and AMOVAs that showed that 72-90% of the variance originated from differences among groups, whereas only 5-13% originated within populations. These patterns are discussed in relation to the known geological history of coral reefs of the GBR and the Coral Sea. Finally, we ask whether the monospecific status of Acanthochromis should be revisited because the sequence divergences found among our samples is substantially greater than those recorded among well-recognized species in other reef fishes.

Chasing boundaries and cascade effects in a coupled barrier - marshes - lagoon system

NASA Astrophysics Data System (ADS)

Lorenzo Trueba, J.; Mariotti, G.

2015-12-01

Low-lying coasts are often characterized by barriers islands, shore-parallel stretches of sand separated from the mainland by marshes and lagoons. We built an exploratory numerical model to examine the morphological feedbacks within an idealized barrier - marshes -lagoon system and predict its evolution under projected rates of sea level rise and sediment supply to the backbarrier environment. Our starting point is a recently developed morphodynamic model, which couples shoreface evolution and overwash processes in a dynamic framework. As such, the model is able to capture dynamics not reproduced by morphokinematic models, which advect geometries without specific concern to processes. These dynamics include periodic barrier retreat due to time lags in the shoreface response to barrier overwash, height drowning due to insufficient overwash fluxes as sea level rises, and width drowning, which occurs when the shoreface response rate is insufficient to maintain the barrier geometry during overwash-driven landward migration. We extended the model by coupling the barrier model with a model for the evolution of the marsh platform and the boundary between the marsh and the adjacent lagoon. The coupled model explicitly describes marsh edge processes and accounts for the modification of the wave regime associated with lagoon width (fetch). Model results demonstrate that changes in factors that are not typically associated with the dynamics of coastal barriers, such as the lagoon width and the rate of export/import of sediments from and to the lagoon, can lead to previously unidentified complex responses of the coupled system. In particular, a wider lagoon in the backbarrier, and/or a reduction in the supply of muddy sediments to the backbarrier, can increase barrier retreat rates and even trigger barrier drowning. Overall, our findings highlight the importance of incorporating backbarrier dynamics in models that aim at predicting the response of barrier systems.

Effect of DGPS failures on dynamic positioning of mobile drilling units in the North Sea.

PubMed

Chen, Haibo; Moan, Torgeir; Verhoeven, Harry

2009-11-01

Basic features of differential global positioning system (DGPS), and its operational configuration on dynamically positioned (DP) mobile offshore drilling units in the North Sea are described. Generic failure modes of DGPS are discussed, and a critical DGPS failure which has the potential to cause drive-off for mobile drilling units is identified. It is the simultaneous erroneous position data from two DGPS's. Barrier method is used to analyze this critical DGPS failure. Barrier elements to prevent this failure are identified. Deficiencies of each barrier element are revealed based on the incidents and operational experiences in the North Sea. Recommendations to strengthen these barrier elements, i.e. to prevent erroneous position data from DGPS, are proposed. These recommendations contribute to the safety of DP operations of mobile offshore drilling units.

Impact of sea-level rise and coral mortality on the wave dynamics and wave forces on barrier reefs.

PubMed

Baldock, T E; Golshani, A; Callaghan, D P; Saunders, M I; Mumby, P J

2014-06-15

A one-dimensional wave model was used to investigate the reef top wave dynamics across a large suite of idealized reef-lagoon profiles, representing barrier coral reef systems under different sea-level rise (SLR) scenarios. The modeling shows that the impacts of SLR vary spatially and are strongly influenced by the bathymetry of the reef and coral type. A complex response occurs for the wave orbital velocity and forces on corals, such that the changes in the wave dynamics vary reef by reef. Different wave loading regimes on massive and branching corals also leads to contrasting impacts from SLR. For many reef bathymetries, wave orbital velocities increase with SLR and cyclonic wave forces are reduced for certain coral species. These changes may be beneficial to coral health and colony resilience and imply that predicting SLR impacts on coral reefs requires careful consideration of the reef bathymetry and the mix of coral species. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Bayesian network approach to predicting nest presence of thefederally-threatened piping plover (Charadrius melodus) using barrier island features

USGS Publications Warehouse

Gieder, Katherina D.; Karpanty, Sarah M.; Fraser, James D.; Catlin, Daniel H.; Gutierrez, Benjamin T.; Plant, Nathaniel G.; Turecek, Aaron M.; Thieler, E. Robert

2014-01-01

Sea-level rise and human development pose significant threats to shorebirds, particularly for species that utilize barrier island habitat. The piping plover (Charadrius melodus) is a federally-listed shorebird that nests on barrier islands and rapidly responds to changes in its physical environment, making it an excellent species with which to model how shorebird species may respond to habitat change related to sea-level rise and human development. The uncertainty and complexity in predicting sea-level rise, the responses of barrier island habitats to sea-level rise, and the responses of species to sea-level rise and human development necessitate a modelling approach that can link species to the physical habitat features that will be altered by changes in sea level and human development. We used a Bayesian network framework to develop a model that links piping plover nest presence to the physical features of their nesting habitat on a barrier island that is impacted by sea-level rise and human development, using three years of data (1999, 2002, and 2008) from Assateague Island National Seashore in Maryland. Our model performance results showed that we were able to successfully predict nest presence given a wide range of physical conditions within the model’s dataset. We found that model predictions were more successful when the range of physical conditions included in model development was varied rather than when those physical conditions were narrow. We also found that all model predictions had fewer false negatives (nests predicted to be absent when they were actually present in the dataset) than false positives (nests predicted to be present when they were actually absent in the dataset), indicating that our model correctly predicted nest presence better than nest absence. These results indicated that our approach of using a Bayesian network to link specific physical features to nest presence will be useful for modelling impacts of sea-level rise- or human

Examples of storm impacts on barrier islands: Chapter 4

USGS Publications Warehouse

Plant, Nathaniel G.; Doran, Kara; Stockdon, Hilary F.

2017-01-01

This chapter focuses on the morphologic variability of barrier islands and on the differences in storm response. It describes different types of barrier island response to individual storms, as well as the integrated response of barrier islands to many storms. The chapter considers case study on the Chandeleur Island chain, where a decadal time series of island elevation measurements have documented a wide range of barrier island responses to storms and long-term processes that are representative of barrier island behaviour at many other locations. These islands are low elevation, extremely vulnerable to storms and exhibit a diversity of storm responses. Additionally, this location experiences a moderately high rate of relative sea-level rise, increasing its vulnerability to the combined impacts of storms and long-term erosional processes. Understanding how natural processes, including storm impacts and intervening recovery periods interact with man-made restoration processes is also broadly relevant to understand the natural and human response to future storms.

Ocean barrier layers' effect on tropical cyclone intensification.

PubMed

Balaguru, Karthik; Chang, Ping; Saravanan, R; Leung, L Ruby; Xu, Zhao; Li, Mingkui; Hsieh, Jen-Shan

2012-09-04

Improving a tropical cyclone's forecast and mitigating its destructive potential requires knowledge of various environmental factors that influence the cyclone's path and intensity. Herein, using a combination of observations and model simulations, we systematically demonstrate that tropical cyclone intensification is significantly affected by salinity-induced barrier layers, which are "quasi-permanent" features in the upper tropical oceans. When tropical cyclones pass over regions with barrier layers, the increased stratification and stability within the layer reduce storm-induced vertical mixing and sea surface temperature cooling. This causes an increase in enthalpy flux from the ocean to the atmosphere and, consequently, an intensification of tropical cyclones. On average, the tropical cyclone intensification rate is nearly 50% higher over regions with barrier layers, compared to regions without. Our finding, which underscores the importance of observing not only the upper-ocean thermal structure but also the salinity structure in deep tropical barrier layer regions, may be a key to more skillful predictions of tropical cyclone intensities through improved ocean state estimates and simulations of barrier layer processes. As the hydrological cycle responds to global warming, any associated changes in the barrier layer distribution must be considered in projecting future tropical cyclone activity.

Wave trapping by dual porous barriers near a wall in the presence of bottom undulation

NASA Astrophysics Data System (ADS)

Kaligatla, R. B.; Manisha; Sahoo, T.

2017-09-01

Trapping of oblique surface gravity waves by dual porous barriers near a wall is studied in the presence of step type varying bottom bed that is connected on both sides by water of uniform depths. The porous barriers are assumed to be fixed at a certain distance in front of a vertical rigid wall. Using linear water wave theory and Darcy's law for flow past porous structure, the physical problem is converted into a boundary value problem. Using eigenfunction expansion in the uniform bottom bed region and modified mild-slope equation in the varying bottom bed region, the mathematical problem is handled for solution. Moreover, certain jump conditions are used to account for mass conservation at slope discontinuities in the bottom bed profile. To understand the effect of dual porous barriers in creating tranquility zone and minimum load on the sea wall, reflection coefficient, wave forces acting on the barrier and the wall, and surface wave elevation are computed and analyzed for different values of depth ratio, porous-effect parameter, incident wave angle, gap between the barriers and wall and slope length of undulated bottom. The study reveals that with moderate porosity and suitable gap between barriers and sea wall, using dual barriers an effective wave trapping system can be developed which will exert less wave force on the barriers and the rigid wall. The proposed wave trapping system is likely to be of immense help for protecting various facilities/ infrastructures in coastal environment.

Data Management Challenges in a National Scientific Program of 55 Diverse Research Projects

NASA Astrophysics Data System (ADS)

De Bruin, T.

2016-12-01

In 2007-2015, the Dutch funding agency NWO funded the National Ocean and Coastal Research Program (in Dutch: ZKO). This program focused on `the scientific analysis of five societal challenges related to a sustainable use of the sea and coastal zones'. These five challenges were safety, economic yield, nature, spatial planning & development and water quality. The ZKO program was `set up to strengthen the cohesion and collaboration within Dutch marine research'. From the start of the program, data management was addressed, to allow data to be shared amongst the, diverse, research projects. The ZKO program was divided in 4 different themes (or regions). The `Carrying Capacity' theme was subdivided into 3 `research lines': Carrying capacity (Wadden Sea) - Policy-relevant Research - Monitoring - Hypothesis-driven Research Oceans North Sea Transnational Wadden Sea Research 56 Projects were funded, ranging from studies on the governance of the Wadden Sea to expeditions studying trace elements in the Atlantic Ocean. One of the first projects to be funded was the data management project. Its objectives were to allow data exchange between projects, to archive all relevant data from all ZKO projects and to make the data and publications publicly available, following the ZKO Data Policy. This project was carried out by the NIOZ Data Management Group. It turned out that the research projects had hardly any interest in sharing data between projects and had good (?) arguments not to share data at all until the end of the projects. A data portal was built, to host and make available all ZKO data and publications. When it came to submitting the data to this portal, most projects obliged willingly, though found it occasionally difficult to find time to do so. However, some projects refused to submit data to an open data portal, despite the rules set up by the funding agency and agreed by all. The take-home message of this presentation is that data sharing is a cultural and

A Powerful Method of Measuring Sea Wave Spectra and their Direction

NASA Astrophysics Data System (ADS)

Blasi, Christoph; Mai, Stephan; Wilhelmi, Jens; Zenz, Theodor; Barjenbruch, Ulrich

2014-05-01

Besides the need of precise measurements of water levels of the sea, there is an increasing demand for assessing waves in height and direction for different purposes like sea-wave modelling and coastal engineering. The design of coastal structures such as piles, breakwaters, and offshore structures like wind farms must take account of the direction of the impacting waves. To date, records of wave directions are scarce. The reason for this might be the high costs of purchasing and operating such measuring devices. These are usually buoys, which require regular maintenance. Against this background, the German Federal Institute of Hydrology (BfG) developed a low-cost directional sea-wave monitoring system that is based on commercially available liquid-level radar sensors. These sensors have the advantage that they have no contact to the fluid, i.e. the corrosive sea water. The newly developed device was tested on two sites. One is the tide gauge 'Borkum Südstrand' that is located in the southern North Sea off the island of Borkum. The other one is the 'Research Platform FINO1' approximately 45 km north of the island of Borkum. The main focus of these tests is the comparison of the data measured by the radar-based system with those of a conventional Directional Wave Rider Buoy. The general conditions at the testing sites are good for the tests. At the tide gauge 'Borkum Südstrand' waves propagate in different directions, strongly influenced by the morphological conditions like shallow waters of the Wadden Seas and the coast of the island of Borkum. Whereas on the open sea, at the site FINO1, the full physical conditions of the sea state, like heavy storms etc. play an important role. To determine and measure the direction of waves, the device has to be able to assess the wave movements in two dimensions. Therefore, an array of several radar sensors is required. Radar sensors are widely used and well established in measuring water levels, e.g. in tanks and basins

Evidence for abiotic sulfurization of marine dissolved organic matter in sulfidic environments

NASA Astrophysics Data System (ADS)

Pohlabeln, A. M.; Niggemann, J.; Dittmar, T.

2016-02-01

Sedimentary organic matter abiotically sulfurizes in sulfidic marine environments. Here we hypothesize that sulfurization also affects dissolved organic matter (DOM), and that sulfidic marine environments are sources of dissolved organic sulfur (DOS) to the ocean. To test these hypotheses we studied solid-phase extractable (SPE) DOS in the Black Sea at various water column depths (oxic and anoxic) and in sediment porewaters from the German Wadden Sea. The concentration and molecular composition of SPE-DOS from these sites and from the oxic water columns of the North Sea (Germany) and of the North Pacific were compared. In support of our hypotheses, SPE-DOS concentrations were elevated in sulfidic waters compared to oxic waters. For a detailed molecular characterization of SPE-DOS, selective wet-chemical alteration experiments targeting different sulfur-containing functional groups were applied prior to Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). These experiments included harsh hydrolysis, selective derivatization of thiols, oxidation, and deoxygenation to test for thioesters, sulfonic acid esters, alkylsulfates, thiols, non-aromatic thioethers, and sulfoxides. Additionally, collision-induced fragmentation experiments were applied to test for sulfonic acids. The tests revealed that the sulfonic acid group was the main structural feature in SPE-DOS, independent of the environmental conditions of the sampling site. Only in Wadden Sea anoxic porewater also non-aromatic thioethers were found which are presumably not stable in oxic waters. The findings from our field studies were confirmed in laboratory experiments, where we abiotically sulfurized marine and algal-derived DOM under conditions similar to that in anoxic marine sediments.

Cyclone-induced rapid creation of extreme Antarctic sea ice conditions

PubMed Central

Wang, Zhaomin; Turner, John; Sun, Bo; Li, Bingrui; Liu, Chengyan

2014-01-01

Two polar vessels, Akademik Shokalskiy and Xuelong, were trapped by thick sea ice in the Antarctic coastal region just to the west of 144°E and between 66.5°S and 67°S in late December 2013. This event demonstrated the rapid establishment of extreme Antarctic sea ice conditions on synoptic time scales. The event was associated with cyclones that developed at lower latitudes. Near the event site, cyclone-enhanced strong southeasterly katabatic winds drove large westward drifts of ice floes. In addition, the cyclones also gave southward ice drift. The arrival and grounding of Iceberg B9B in Commonwealth Bay in March 2011 led to the growth of fast ice around it, forming a northward protruding barrier. This barrier blocked the westward ice drift and hence aided sea ice consolidation on its eastern side. Similar cyclone-induced events have occurred at this site in the past after the grounding of Iceberg B9B. Future events may be predictable on synoptic time scales, if cyclone-induced strong wind events can be predicted. PMID:24937550

A submesoscale coherent vortex in the Ligurian Sea: From dynamical barriers to biological implications

NASA Astrophysics Data System (ADS)

Bosse, Anthony; Testor, Pierre; Mayot, Nicolas; Prieur, Louis; D'Ortenzio, Fabrizio; Mortier, Laurent; Le Goff, Hervé; Gourcuff, Claire; Coppola, Laurent; Lavigne, Héloïse; Raimbault, Patrick

2017-08-01

In June 2013, a glider equipped with oxygen and fluorescence sensors has been used to extensively sample an anticyclonic Submesoscale Coherent Vortex (SCV) in the Ligurian Sea (NW Mediterranean Sea). Those measurements are complemented by full-depth CTD casts (T, S, and oxygen) and water samples documenting nutrients and phytoplankton pigments within the SCV and outside. The SCV has a very homogeneous core of oxygenated waters between 300 and 1200 m formed 4.5 months earlier during the winter deep convection event. It has a strong dynamical signature with peak velocities at 700 m depth of 13.9 cm s-1 in cyclogeostrophic balance. The eddy has a small radius of 6.2 km corresponding to high Rossby number of -0.45. The vorticity at the eddy center reaches -0.8f. Cross-stream isopycnic diffusion of tracers between the eddy core and the surroundings is found to be very limited due to dynamical barriers set by the SCV associated with a diffusivity coefficient of about 0.2 m2 s-1. The deep core is nutrients-depleted with concentrations of nitrate, phosphate, and silicate, 13-18% lower than the rich surrounding waters. However, the nutriclines are shifted of about 20-50 m toward the surface thus increasing the nutrients availability for phytoplankton. Chlorophyll-a concentrations at the deep chlorophyll maximum are subsequently about twice bigger as compared to outside. Pigments further reveal the predominance of nanophytoplankton inside the eddy and an enhancement of the primary productivity. This study demonstrates the important impact of postconvective SCVs on nutrients distribution and phytoplankton community, as well as on the subsequent primary production and carbon sequestration.