Management of the Wadden Sea

NASA Astrophysics Data System (ADS)

Wolff, W. J.; Zijlstra, J. J.

1980-03-01

The Wadden Sea situated along the North Sea coasts of Denmark, the Federal Republic of Germany and The Netherlands represents one of the world's largest bar-built type of estuaries. The area is a typical sedimentation and mineralization basin, with a large influx of organic matter from the adjoining North Sea, consequently a delicate oxygen balance and a rich benthic macrofauna, poor in species, which serves as food for juveniles of some commercially important North Sea fishes and for large numbers of migrating and wintering waders and waterfowl. Past and present activities of the human society in the area include fisheries (mainly for shrimp and mussels, semi-culture), shipping, land reclamation, recreation, dredging for sand and shells, and waste discharge from industries and human communities. Until the present these activities, although sometimes conflicting, did not fundamentally affect the area and its biota (pollution excluded), but future claims, including the construction of large deep-sea harbours, drilling for natural gas and oil, large-scale land reclamation and increased industrialization etc., might gradually induce degradation. For instance, area reduction by continued land reclamation could lead to irreversible losses of specific biotopes (e. g. salt-marshes, mud-flats), which could affect the size of bird and fish populations in a much wider region. Increased pollution, which has already inflicted damage on bird and seal populations, could reduce the fauna and hence the value of the area as a natural sanctuary. In the event of a proposal for a new human activity in the area, the present standing practice in the countries concerned requires an evaluation of its safety and economic aspects and its environmental impact. However, the various plans are considered separately and there is a general need for integrated management of the area.

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.

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.

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

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.

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.

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.

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

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.

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.

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

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.

Impact of Land-Sea Thermal Contrast on Inland Penetration of Sea Fog over The Yellow Sea

NASA Astrophysics Data System (ADS)

Lee, H. Y.; Chang, E. C.

2017-12-01

Sea fog can be classified into a cold sea fog that occurs when sea surface temperature (SST) is colder than sea air temperature (SAT) and a warm sea fog that occurs when the SST is warmer than the SAT. We simulated two sea fog events over the Yellow Sea which is surrounded by Korean Peninsula and mainland China using Weather Research and Forecasting (WRF) model. Our first aim is to understand contributions of major factors for the sea fog formation. First, the two sea fog events are designated as cold and warm types, and cooling rates as well as moistening rates are calculated employing bulk aerodynamic methods. Both cases show cooling and moistening by turbulent fluxes play an important role in condensation either favorably or unfavorably. However, longwave radiative cooling is as or even stronger than turbulent cooling, suggesting it is the most decisive factor in formation of sea fogs regardless of their type. Our second purpose of the study is to understand inland penetration of sea fog in terms of thermal contrast (TC) and it was conducted through sensitivity tests of SST and land skin temperature (LST). In the SST sensitivity tests, increase of SSTs lead to that of upward turbulent heat fluxes so that SATs rise which are responsible for evaporation of cloud waters and it is common response of the two events. In addition, change of the SST induce that of the TC and may affect the inland penetration of sea fog. However, when the cloud waters over the sea evaporate, it is hard to fully determine the inland penetration. As a remedy for this limitation, LST is now modified instead of SST to minimize the evaporation effect, maintaining the equivalent TC. In the case of cold sea fog, land air temperature (LAT) is warmer than SAT. Here, decrease of the LAT leads to weakening of the TC and favors the inland penetration. On the other hand, LAT is colder than the SAT in the warm sea fog event. When the LAT decreases, the TC is intensified resulting in blocking of the

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.

Phytoplankton response to the contrasting physical regimes in the eastern Arabian Sea during north east monsoon

NASA Astrophysics Data System (ADS)

Chndrasekhararao, A. V.; Kurian, Siby; Vidya, P. J.; Gauns, Mangesh; Shenoy, Damodar M.; Mulla, Amara; Naik, Hema; Reddy, T. Venugopal; Naqvi, S. W. A.

2018-06-01

Phytoplankton abundance and composition in two contrasting physical regimes - convective mixing in the northeastern Arabian Sea (NEAS) and Arabian Sea mini warm pool (ASMWP) in the southeastern Arabian Sea (SEAS) - were investigated during the northeast monsoon (NEM) of 2015 and 2017. Observations in 2015 were carried out late during the season, and only one station in the north (at 21°N latitude) fell within the zone of convective mixing where microplankton was dominated by diatoms. In 2017, convective mixing occurred even at 16°N latitude, but the microplankton contribution was low, presumably due to low Si/N ratios. Within the convective mixing regime of the NEAS, chlorophyll (Chl) a concentrations were higher in 2015 (maximum 1080 ng L-1; average 493 ng L-1) than in 2017 (maximum 673 ng L-1; average 263 ng L-1). In contrast, picophytoplankton were dominant in the ASMWP of the SEAS with peak abundance associated with the subsurface chlorophyll maximum. A warm core eddy was present in 2015 in the SEAS where four times higher Prochlorococcus counts were found within the core of the eddy than at its periphery. This study provides the first description of the phytoplankton community in the ASMWP. Our results clearly demonstrate phytoplankton response to the contrasting physical conditions, highlighting the role of bio-physical coupling in the productivity of the Arabian Sea.

An increase in aerosol burden due to the land-sea warming contrast

NASA Astrophysics Data System (ADS)

Hassan, T.; Allen, R.; Randles, C. A.

2017-12-01

Climate models simulate an increase in most aerosol species in response to warming, particularly over the tropics and Northern Hemisphere midlatitudes. This increase in aerosol burden is related to a decrease in wet removal, primarily due to reduced large-scale precipitation. Here, we show that the increase in aerosol burden, and the decrease in large-scale precipitation, is related to a robust climate change phenomenon—the land/sea warming contrast. Idealized simulations with two state of the art climate models, the National Center for Atmospheric Research Community Atmosphere Model version 5 (NCAR CAM5) and the Geophysical Fluid Dynamics Laboratory Atmospheric Model 3 (GFDL AM3), show that muting the land-sea warming contrast negates the increase in aerosol burden under warming. This is related to smaller decreases in near-surface relative humidity over land, and in turn, smaller decreases in large-scale precipitation over land—especially in the NH midlatitudes. Furthermore, additional idealized simulations with an enhanced land/sea warming contrast lead to the opposite result—larger decreases in relative humidity over land, larger decreases in large-scale precipitation, and larger increases in aerosol burden. Our results, which relate the increase in aerosol burden to the robust climate projection of enhanced land warming, adds confidence that a warmer world will be associated with a larger aerosol burden.

Foraging behaviour of juvenile female New Zealand sea lions (Phocarctos hookeri) in contrasting environments.

PubMed

Leung, Elaine S; Augé, Amélie A; Chilvers, B Louise; Moore, Antoni B; Robertson, Bruce C

2013-01-01

Foragers can show adaptive responses to changes within their environment through morphological and behavioural plasticity. We investigated the plasticity in body size, at sea movements and diving behaviour of juvenile female New Zealand (NZ) sea lions (Phocarctos hookeri) in two contrasting environments. The NZ sea lion is one of the rarest pinnipeds in the world. Most of the species is based at the subantarctic Auckland Islands (AI; considered to be marginal foraging habitat), with a recolonizing population on the Otago Peninsula, NZ mainland (considered to be more optimal habitat). We investigated how juvenile NZ sea lions adjust their foraging behaviour in contrasting environments by deploying satellite-linked platform transmitting terminals (PTTs) and time-depth recorders (TDRs) on 2-3 year-old females at AI (2007-2010) and Otago (2009-2010). Juvenile female NZ sea lions exhibited plasticity in body size and behaviour. Otago juveniles were significantly heavier than AI juveniles. Linear mixed effects models showed that study site had the most important effect on foraging behaviour, while mass and age had little influence. AI juveniles spent more time at sea, foraged over larger areas, and dove deeper and longer than Otago juveniles. It is difficult to attribute a specific cause to the observed contrasts in foraging behaviour because these differences may be driven by disparities in habitat/prey characteristics, conspecific density levels or interseasonal variation. Nevertheless, the smaller size and increased foraging effort of AI juveniles, combined with the lower productivity in this region, support the hypothesis that AI are less optimal habitat than Otago. It is more difficult for juveniles to forage in suboptimal habitats given their restricted foraging ability and lower tolerance for food limitation compared to adults. Thus, effective management measures should consider the impacts of low resource environments, along with changes that can alter food

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

Foraging Behaviour of Juvenile Female New Zealand Sea Lions (Phocarctos hookeri) in Contrasting Environments

PubMed Central

Leung, Elaine S.; Augé, Amélie A.; Chilvers, B. Louise; Moore, Antoni B.; Robertson, Bruce C.

2013-01-01

Foragers can show adaptive responses to changes within their environment through morphological and behavioural plasticity. We investigated the plasticity in body size, at sea movements and diving behaviour of juvenile female New Zealand (NZ) sea lions (Phocarctos hookeri) in two contrasting environments. The NZ sea lion is one of the rarest pinnipeds in the world. Most of the species is based at the subantarctic Auckland Islands (AI; considered to be marginal foraging habitat), with a recolonizing population on the Otago Peninsula, NZ mainland (considered to be more optimal habitat). We investigated how juvenile NZ sea lions adjust their foraging behaviour in contrasting environments by deploying satellite-linked platform transmitting terminals (PTTs) and time-depth recorders (TDRs) on 2–3 year-old females at AI (2007–2010) and Otago (2009–2010). Juvenile female NZ sea lions exhibited plasticity in body size and behaviour. Otago juveniles were significantly heavier than AI juveniles. Linear mixed effects models showed that study site had the most important effect on foraging behaviour, while mass and age had little influence. AI juveniles spent more time at sea, foraged over larger areas, and dove deeper and longer than Otago juveniles. It is difficult to attribute a specific cause to the observed contrasts in foraging behaviour because these differences may be driven by disparities in habitat/prey characteristics, conspecific density levels or interseasonal variation. Nevertheless, the smaller size and increased foraging effort of AI juveniles, combined with the lower productivity in this region, support the hypothesis that AI are less optimal habitat than Otago. It is more difficult for juveniles to forage in suboptimal habitats given their restricted foraging ability and lower tolerance for food limitation compared to adults. Thus, effective management measures should consider the impacts of low resource environments, along with changes that can alter food

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

30-Year Satellite Record Reveals Contrasting Arctic and Antarctic Decadal Sea Ice Variability

NASA Technical Reports Server (NTRS)

Cavalieri, D. J.; Parkinson, C. L.; Vinnikov, K. Y.

2003-01-01

A 30-year satellite record of sea ice extents derived mostly from satellite microwave radiometer observations reveals that the Arctic sea ice extent decreased by 0.30+0.03 x 10(exp 6) square kilometers per 10 yr from 1972 through 2002, but by 0.36 plus or minus 0.05 x 10(exp 6) square kilometers per 10yr from 1979 through 2002, indicating an acceleration of 20% in the rate of decrease. In contrast, the Antarctic sea ice extent decreased dramatically over the period 1973-1977, then gradually increased. Over the full 30-year period, the Antarctic ice extent decreased by 0.15 plus or minus 0.08 x 10(exp 6) square kilometers per 10 yr. The trend reversal is attributed to a large positive anomaly in Antarctic sea ice extent in the early 1970's, an anomaly that apparently began in the late 1960's, as observed in early visible and infrared satellite images.

Identification of contrasting seasonal sea ice conditions during the Younger Dryas

NASA Astrophysics Data System (ADS)

Cabedo-Sanz, P.; Belt, S. T.; Knies, J.

2012-12-01

The presence of the sea ice diatom biomarker IP25 in Arctic marine sediments has been used in previous studies as a proxy for past spring sea ice occurrence and as an indicator of wider palaeoenvironmental conditions for different regions of the Arctic over various timescales [e.g. 1, 2]. The current study focuses on high-resolution palaeo sea ice reconstructions for northern Norway during the last ca. 15 cal. kyr BP. Within this study, particular emphasis has been placed on the identification of the sea ice conditions during the Younger Dryas and the application of different biomarker-based proxies to both identify and quantify seasonal sea ice conditions. Firstly, the appearance of the specific sea ice diatom proxy IP25 at ca. 12.9 cal. kyr BP in a marine sediment core (JM99-1200) obtained from Andfjorden has provided an unambiguous but qualitative measure of seasonal sea ice and thus the onset of the Younger Dryas stadial. The near continuous occurrence of IP25 for the next ca. 1400 yr demonstrates seasonal sea ice during this interval, although variable abundances suggest that the recurrent conditions in the early-mid Younger Dryas (ca. 12.9 - 11.9 cal. kyr BP) changed significantly from stable to highly variable sea ice conditions at ca. 11.9 cal. kyr BP and this instability in sea ice prevailed for the subsequent ca. 400 yr. At ca. 11.5 cal. kyr BP, IP25 disappeared from the record indicating ice-free conditions that signified the beginning of the Holocene. Similarly, a high resolution record from the Kveithola Through, western Barents Sea, showed clearly higher IP25 concentrations during the Younger Dryas stadial compared to the Holocene. For both marine records, the IP25 concentrations were also combined with those of the open water phytoplankton biomarker brassicasterol to generate PBIP25 data from which more quantitative measurements of sea ice were determined. The contrasting seasonal sea ice conditions during the Younger Dryas were further verified

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

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

Growing Land-Sea Temperature Contrast and the Intensification of Arctic Cyclones

NASA Astrophysics Data System (ADS)

Day, Jonathan J.; Hodges, Kevin I.

2018-04-01

Cyclones play an important role in the coupled dynamics of the Arctic climate system on a range of time scales. Modeling studies suggest that storminess will increase in Arctic summer due to enhanced land-sea thermal contrast along the Arctic coastline, in a region known as the Arctic Frontal Zone (AFZ). However, the climate models used in these studies are poor at reproducing the present-day Arctic summer cyclone climatology and so their projections of Arctic cyclones and related quantities, such as sea ice, may not be reliable. In this study we perform composite analysis of Arctic cyclone statistics using AFZ variability as an analog for climate change. High AFZ years are characterized both by increased cyclone frequency and dynamical intensity, compared to low years. Importantly, the size of the response in this analog suggests that General Circulation Models may underestimate the response of Arctic cyclones to climate change, given a similar change in baroclinicity.

Summertime land-sea thermal contrast and atmospheric circulation over East Asia in a warming climate—Part I: Past changes and future projections

NASA Astrophysics Data System (ADS)

Kamae, Youichi; Watanabe, Masahiro; Kimoto, Masahide; Shiogama, Hideo

2014-11-01

Land-sea surface air temperature (SAT) contrast, an index of tropospheric thermodynamic structure and dynamical circulation, has shown a significant increase in recent decades over East Asia during the boreal summer. In Part I of this two-part paper, observational data and the results of transient warming experiments conducted using coupled atmosphere-ocean general circulation models (GCMs) are analyzed to examine changes in land-sea thermal contrast and the associated atmospheric circulation over East Asia from the past to the future. The interannual variability of the land-sea SAT contrast over the Far East for 1950-2012 was found to be tightly coupled with a characteristic tripolar pattern of tropospheric circulation over East Asia, which manifests as anticyclonic anomalies over the Okhotsk Sea and around the Philippines, and a cyclonic anomaly over Japan during a positive phase, and vice versa. In response to CO2 increase, the cold northeasterly winds off the east coast of northern Japan and the East Asian rainband were strengthened with the circulation pattern well projected on the observed interannual variability. These results are commonly found in GCMs regardless of future forcing scenarios, indicating the robustness of the East Asian climate response to global warming. The physical mechanisms responsible for the increase of the land-sea contrast are examined in Part II.

Feedback attribution of the land-sea warming contrast in a global warming simulation of the NCAR CCSM4

DOE PAGES

Sejas, Sergio A.; Albert, Oriene S.; Cai, Ming; ...

2014-12-02

One of the salient features in both observations and climate simulations is a stronger land warming than sea. This paper provides a quantitative understanding of the main processes that contribute to the land-sea warming asymmetry in a global warming simulation of the NCAR CCSM4. The CO 2 forcing alone warms the surface nearly the same for both land and sea, suggesting that feedbacks are responsible for the warming contrast. Our analysis on one hand confirms that the principal contributor to the above-unity land-to-sea warming ratio is the evaporation feedback; on the other hand the results indicate that the sensible heatmore » flux feedback has the largest land-sea warming difference that favors a greater ocean than land warming. Furthermore, the results uniquely highlight the importance of other feedbacks in establishing the above-unity land-to-sea warming ratio. Particularly, the SW cloud feedback and the ocean heat storage in the transient response are key contributors to the greater warming over land than sea.« less

Feedback attribution of the land-sea warming contrast in a global warming simulation of the NCAR CCSM4

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

Sejas, Sergio A.; Albert, Oriene S.; Cai, Ming

One of the salient features in both observations and climate simulations is a stronger land warming than sea. This paper provides a quantitative understanding of the main processes that contribute to the land-sea warming asymmetry in a global warming simulation of the NCAR CCSM4. The CO 2 forcing alone warms the surface nearly the same for both land and sea, suggesting that feedbacks are responsible for the warming contrast. Our analysis on one hand confirms that the principal contributor to the above-unity land-to-sea warming ratio is the evaporation feedback; on the other hand the results indicate that the sensible heatmore » flux feedback has the largest land-sea warming difference that favors a greater ocean than land warming. Furthermore, the results uniquely highlight the importance of other feedbacks in establishing the above-unity land-to-sea warming ratio. Particularly, the SW cloud feedback and the ocean heat storage in the transient response are key contributors to the greater warming over land than sea.« less

Contrasting habitat selection amongst cephalopods in the Mediterranean Sea: When the environment makes the difference.

PubMed

Lauria, V; Garofalo, G; Gristina, M; Fiorentino, F

2016-08-01

Conservation of fish habitat requires a deeper knowledge of how species distribution patterns are related to environmental factors. Habitat suitability modelling is an essential tool to quantify species' realised niches and understand species-environment relationships. Cephalopods are important players in the marine food web and a significant resource for fisheries; they are also very sensitive to environmental changes. Here a time series of fishery-independent data (1998-2011) was used to construct habitat suitability models and investigate the influence of environmental variables on four commercial cephalopods: Todaropsis eblanae, Illex coindetii, Eledone moschata and Eledone cirrhosa, in the central Mediterranean Sea. The main environmental predictors of cephalopod habitat suitability were depth, seafloor morphology, chlorophyll-a concentration, sea surface temperature and surface salinity. Predictive maps highlighted contrasting habitat selection amongst species. This study identifies areas where the important commercial species of cephalopods are concentrated and provides significant information for a future spatial based approach to fisheries management in the Mediterranean Sea. Copyright © 2016 Elsevier Ltd. All rights reserved.

The contrasting response of Hadley circulation to different meridional structure of sea surface temperature in CMIP5

NASA Astrophysics Data System (ADS)

Feng, Juan; Li, Jianping; Zhu, Jianlei; Li, Yang; Li, Fei

2018-02-01

The response of the Hadley circulation (HC) to the sea surface temperature (SST) is determined by the meridional structure of SST and varies according to the changing nature of this meridional structure. The capability of the models from the phase 5 of the Coupled Model Intercomparison Project (CMIP5) is utilized to represent the contrast response of the HC to different meridional SST structures. To evaluate the responses, the variations of HC and SST were linearly decomposed into two components: the equatorially asymmetric (HEA for HC, and SEA for SST) and equatorially symmetric (HES for HC, and SES for SST) components. The result shows that the climatological features of HC and tropical SST (including the spatial structures and amplitude) are reasonably simulated in all the models. However, the response contrast of HC to different SST meridional structures shows uncertainties among models. This may be due to the fact that the long-term temporal variabilities of HEA, HES, and SEA are limited reproduced in the models, although the spatial structures of their long-term variabilities are relatively reasonably simulated. These results indicate that the performance of the CMIP5 models to simulate long-term temporal variability of different meridional SST structures and related HC variations plays a fundamental role in the successful reproduction of the response of HC to different meridional SST structures.

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.

Recruitment patterns, low cannibalism and reduced interspecific predation contribute to high invasion success of two Pacific crabs in northwestern Europe

NASA Astrophysics Data System (ADS)

Geburzi, Jonas C.; Brandis, Dirk; Buschbaum, Christian

2018-01-01

Life-history traits and interactions with native species play an important role for the successful establishment of non-native species in new habitats. We investigated the recent successful invasion of the Pacific crabs Hemigrapsus takanoi and H. sanguineus to the southeastern North Sea coast with respect to their recruitment patterns, as well as interactions of juvenile with sub-adult individuals among the Pacific crabs and with native shore crabs Carcinus maenas. A field survey of juvenile native and introduced crab abundances (carapace width 1.4-10 mm) was conducted in the northern Wadden Sea, spanning 24 months from 2014 to 2016. The survey revealed different seasonal recruitment patterns of native C. maenas and both introduced Hemigrapsus species. Native shore crabs showed a single recruitment peak from June to July, while Hemigrapsus spp. mainly recruited from August to early September, but recruits occurred in low densities throughout the winter until the end of the following spring season. Field experiments on the effects of larger crabs on the recruitment intensity showed that recruitment of H. takanoi was enhanced by the presence of larger congeners, but remained unaffected by larger C. maenas. Recruitment of juvenile C. maenas, by contrast, was reduced by the presence of larger Hemigrapsus spp. Additional laboratory experiments revealed high rates of cannibalism on newly recruited C. maenas by subadult conspecifics as well as strong predation by larger Hemigrapsus spp. In contrast, newly recruited Hemigrapsus spp. had a much lower risk of being preyed on by subadult conspecifics and native shore crabs. Our results suggest that the timing of recruitment in combination with low intraspecific competition and reduced predation pressure by native shore crabs are crucial for the rapid and ongoing establishment of Hemigrapsus spp. in the Wadden Sea.

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.

Contrasting population histories of the deep-sea demersal fish, Lycodes matsubarai, in the Sea of Japan and the Sea of Okhotsk.

PubMed

Sakuma, Kay; Ueda, Yuji; Hamatsu, Tomonori; Kojima, Shigeaki

2014-06-01

Recent studies have revealed the impact of the drastic climate change during the last glacial period on coastal marine and anadromous species in the marginal seas of the northwestern Pacific Ocean; however, its influence on deep-sea species remains poorly understood. To compare the effects of the last glacial period on populations from the Sea of Japan and the Sea of Okhotsk, we examined the mitochondrial control region and cytochrome b gene sequences of Lycodes matsubarai, a deepsea demersal fish that inhabits these two seas. Our results showed clear genetic differentiation of populations between the two seas. The populations may have diverged during the last glacial period, probably as a result of vicariance due to the drastic sea level change. The population in the Sea of Okhotsk was larger than that in the Sea of Japan, but suddenly decreased after the last glacial period. However, the Sea of Japan population expanded after the last glacial period, coincident with high levels of oxygenation in deep-sea areas. These results elucidate regional-scale impacts of climate change on deep-sea organisms.

Spatially Explicit Modeling Reveals Cephalopod Distributions Match Contrasting Trophic Pathways in the Western Mediterranean Sea

PubMed Central

Puerta, Patricia; Hunsicker, Mary E.; Quetglas, Antoni; Álvarez-Berastegui, Diego; Esteban, Antonio; González, María; Hidalgo, Manuel

2015-01-01

Populations of the same species can experience different responses to the environment throughout their distributional range as a result of spatial and temporal heterogeneity in habitat conditions. This highlights the importance of understanding the processes governing species distribution at local scales. However, research on species distribution often averages environmental covariates across large geographic areas, missing variability in population-environment interactions within geographically distinct regions. We used spatially explicit models to identify interactions between species and environmental, including chlorophyll a (Chla) and sea surface temperature (SST), and trophic (prey density) conditions, along with processes governing the distribution of two cephalopods with contrasting life-histories (octopus and squid) across the western Mediterranean Sea. This approach is relevant for cephalopods, since their population dynamics are especially sensitive to variations in habitat conditions and rarely stable in abundance and location. The regional distributions of the two cephalopod species matched two different trophic pathways present in the western Mediterranean Sea, associated with the Gulf of Lion upwelling and the Ebro river discharges respectively. The effects of the studied environmental and trophic conditions were spatially variant in both species, with usually stronger effects along their distributional boundaries. We identify areas where prey availability limited the abundance of cephalopod populations as well as contrasting effects of temperature in the warmest regions. Despite distributional patterns matching productive areas, a general negative effect of Chla on cephalopod densities suggests that competition pressure is common in the study area. Additionally, results highlight the importance of trophic interactions, beyond other common environmental factors, in shaping the distribution of cephalopod populations. Our study presents a valuable

Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea

PubMed Central

Kousteni, V; Kasapidis, P; Kotoulas, G; Megalofonou, P

2015-01-01

Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species' distribution, most notably a population growth trend in the western Mediterranean/Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the small-spotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed. PMID:25469687

Spatial contrast in phytoplankton, bacteria and microzooplankton grazing between the eutrophic Yellow Sea and the oligotrophic South China Sea

NASA Astrophysics Data System (ADS)

Zhang, Yafeng; Wang, Xutao; Yin, Kedong

2018-01-01

Three cruises were conducted to investigate the distributions of nutrients, chlorophyll a (Chl- a), new and regenerated primary production, bacterial abundance and production, and microzooplankton grazing rates in the Yellow Sea (YS) and the South China Sea (SCS) during March and May. As the water column moved from low to high temperature, weak to strong stratification and high to low nutrients from the YS to the SCS, Chl- a, primary production and bacterial biomass decreased. In contrast, bacterial production, microzooplankton grazing and size preference increased from the YS to the SCS. The increasing grazing activity and decreasing f-ratio from the YS to the SCS suggest roles of regenerated nutrients in the supporting the community increased and more bacteria played important roles in the carbon flow in the oligotrophic SCS than in the eutrophic YS. These variabilities force the classical food chain dominated community in the eutrophic waters into the microbial loop, which is dominant in oligotrophic waters. As nutrients decrease, temperature and grazing activity increase from the YS to the SCS. The increasing ratio of integrated bacterial production to integrated primary production indicates that communities change from autotrophy to heterotrophy and waters change from a carbon sink to a carbon source.

Contrasts Between Precipitation over Mediterranean Sea and Adjacent Continental Areas Based on Decadal Scale Satellite Estimates

NASA Technical Reports Server (NTRS)

Smith, Eric A.

2007-01-01

Most knowledge concerning the last century's climatology and climate dynamics of precipitation over the Mediterranean Sea basin is based on observations taken from rain gauges surrounding the sea itself. In turn, most of the observations come from Southern Europe, with many fewer measurements taken from widely scattered sites situated over North Africa, the Middle East, and the Balkans. This aspect of research on the Mediterranean Sea basin is apparent in a recent compilation of studies presented in book form concerning climate variability of the Mediterranean region [Lionello, P., P. Malanotte-Rizzoli, and R. Boscolo (eds.), 2006: Mediterranean Climate Variability. Elsevier, Amsterdam, 9 chapters.] In light of this missing link to over-water observations, this study (in conjunction with four companion studies by Z. Haddad, A. Mugnai, T. Nakazawa, and G. Stephens) will contrast the nature of precipitation variability directly over the Mediterranean Sea to precipitation variability over the surrounding land areas based on three decades of satellite-based precipitation estimates which have stood up well to validation scrutiny. The satellite observations are drawn from the Global Precipitation Climatology Project (GPCP) dataset extending back to 1979 and the TRMM Merged Algorithm 3b42 dataset extending back to 1998. Both datasets are mostly produced from microwave measurements, excepting the period from 1979 to mid-1987 when only infrared satellite measurements were available for the GPCP estimates. The purpose of this study is to emphasize how the salient properties of precipitation variability over land and sea across a hierarchy of space and time scales, and the salient differences in these properties, might be used in guiding short-term climate models to better predictions of future climate states under different regional temperature-change scenarios.

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.

On the role of inter-basin surface salinity contrasts in global ocean circulation

NASA Astrophysics Data System (ADS)

Seidov, D.; Haupt, B. J.

2002-08-01

The role of sea surface salinity (SSS) contrasts in maintaining vigorous global ocean thermohaline circulation (TOC) is revisited. Relative importance of different generalizations of sea surface conditions in climate studies is explored. Ocean-wide inter-basin SSS contrasts serve as the major controlling element in global TOC. These contrasts are shown to be at least as important as high-latitudinal freshwater impacts. It is also shown that intra-basin longitudinal distribution of sea surface salinity, as well as intra- and inter-basin longitudinal distribution of sea surface temperature, is not crucial to conveyor functionality if only inter-basin contrasts in sea surface salinity are retained. This is especially important for paleoclimate and future climate simulations.

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

Future anthropogenic sea-level rise and its impact on coastal regions is an important issue facing human civilizations. Due to the short nature of the instrumental record of sea-level change, development of proxies for sea-level change prior to the advent of instrumental records is essential to reconstruct long-term background sea-level changes on local, regional and global scales. Two of the most widely used approaches for past sea-level changes are: (1) exploitation of dated geomorphologic features such as coastal sands (e.g. Mauz and Hassler, 2000), salt marsh (e.g. Madsen et al., 2007), terraces (e.g. Chappell et al., 1996), and other coastal sediments (e.g. Zong et al., 2003); and (2) sea-level transfer functions based on faunal assemblages such as testate amoebae (e.g. Charman et al., 2002), foraminifera (e.g. Chappell and Shackleton, 1986; Horton, 1997), and diatoms (e.g. Horton et al., 2006). While a variety of methods has been developed to reconstruct palaeo-changes in sea level, many regions, including the Bohai Sea, China, still lack detailed relative sea-level curves extending back to the Pleistocene (Yi et al., 2012). For example, coral terraces are absent in the Bohai Sea, and the poor preservation of faunal assemblages makes development of a transfer function for a relative sea-level reconstruction unfeasible. In contrast, frequent alternations between transgression and regression has presumably imprinted sea-level change on the grain size distribution of Bohai Sea sediments, which varies from medium silt to coarse sand during the late Quaternary (IOCAS, 1985). Advantages of grainsize-based relative sea-level transfer function approaches are that they require smaller sample sizes, allowing for replication, faster measurement and higher spatial or temporal resolution at a fraction of the cost of detail micro-palaeontological analysis (Yi et al., 2012). Here, we employ numerical methods to partition sediment grain size using a combined database of

Surfactant control of air-sea gas exchange across contrasting biogeochemical regimes

NASA Astrophysics Data System (ADS)

Pereira, Ryan; Schneider-Zapp, Klaus; Upstill-Goddard, Robert

2014-05-01

Air-sea gas exchange is important to the global partitioning of CO2.Exchange fluxes are products of an air-sea gas concentration difference, ΔC, and a gas transfer velocity, kw. The latter is controlled by the rate of turbulent diffusion at the air-sea interface but it cannot be directly measured and has a high uncertainty that is now considered one of the greatest challenges to quantifying net global air-sea CO2 exchange ...(Takahashi et al., 2009). One important control on kw is exerted by sea surface surfactants that arise both naturally from biological processes and through anthropogenic activity. They influence gas exchange in two fundamental ways: as a monolayer physical barrier and through modifying sea surface hydrodynamics and hence turbulent energy transfer. These effects have been demonstrated in the laboratory with artificial surfactants ...(Bock et al., 1999; Goldman et al., 1988) and through purposeful surfactant releases in coastal waters .(.).........().(Brockmann et al., 1982) and in the open ocean (Salter et al., 2011). Suppression of kwin these field experiments was ~5-55%. While changes in both total surfactant concentration and the composition of the natural surfactant pool might be expected to impact kw, the required in-situ studies are lacking. New data collected from the coastal North Sea in 2012-2013 shows significant spatio-temporal variability in the surfactant activity of organic matter within the sea surface microlayer that ranges from 0.07-0.94 mg/L T-X-100 (AC voltammetry). The surfactant activities show a strong winter/summer seasonal bias and general decrease in concentration with increasing distance from the coastline possibly associated with changing terrestrial vs. phytoplankton sources. Gas exchange experiments of this seawater using a novel laboratory tank and gas tracers (CH4 and SF6) demonstrate a 12-45% reduction in kw compared to surfactant-free water. Seasonally there is higher gas exchange suppression in the summer

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.

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.

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.

Effect of Redox Conditions on Bacterial Community Structure in Baltic Sea Sediments with Contrasting Phosphorus Fluxes

PubMed Central

Steenbergh, Anne K.; Bodelier, Paul L. E.; Slomp, Caroline P.; Laanbroek, Hendrikus J.

2014-01-01

Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological processes that release or retain phosphorus in marine sediments. To gain more insight in the role of bacteria in phosphorus release from sediments, we assessed the effect of redox conditions on the structure of bacterial communities. To do so, we incubated surface sediments from four sampling sites in the Baltic Sea under oxic and anoxic conditions and analyzed the fingerprints of the bacterial community structures in these incubations and the original sediments. This paper describes the effects of redox conditions, sampling station, and sample type (DNA, RNA, or whole-cell sample) on bacterial community structure in sediments. Redox conditions explained only 5% of the variance in community structure, and bacterial communities from contrasting redox conditions showed considerable overlap. We conclude that benthic bacterial communities cannot be classified as being typical for oxic or anoxic conditions based on community structure fingerprints. Our results suggest that the overall structure of the benthic bacterial community has only a limited impact on benthic phosphate fluxes in the Baltic Sea. PMID:24667801

Effect of redox conditions on bacterial community structure in Baltic Sea sediments with contrasting phosphorus fluxes.

PubMed

Steenbergh, Anne K; Bodelier, Paul L E; Slomp, Caroline P; Laanbroek, Hendrikus J

2014-01-01

Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological processes that release or retain phosphorus in marine sediments. To gain more insight in the role of bacteria in phosphorus release from sediments, we assessed the effect of redox conditions on the structure of bacterial communities. To do so, we incubated surface sediments from four sampling sites in the Baltic Sea under oxic and anoxic conditions and analyzed the fingerprints of the bacterial community structures in these incubations and the original sediments. This paper describes the effects of redox conditions, sampling station, and sample type (DNA, RNA, or whole-cell sample) on bacterial community structure in sediments. Redox conditions explained only 5% of the variance in community structure, and bacterial communities from contrasting redox conditions showed considerable overlap. We conclude that benthic bacterial communities cannot be classified as being typical for oxic or anoxic conditions based on community structure fingerprints. Our results suggest that the overall structure of the benthic bacterial community has only a limited impact on benthic phosphate fluxes in the Baltic Sea.

Comparison of the effect of land-sea thermal contrast on interdecadal variations in winter and summer blockings

NASA Astrophysics Data System (ADS)

He, Yongli; Huang, Jianping; Li, Dongdong; Xie, Yongkun; Zhang, Guolong; Qi, Yulei; Wang, Shanshan; Totz, Sonja

2017-11-01

The influence of winter and summer land-sea surface thermal contrast on blocking for 1948-2013 is investigated using observations and the coupled model intercomparison project outputs. The land-sea index (LSI) is defined to measure the changes of zonal asymmetric thermal forcing under global warming. The summer LSI shows a slower increasing trend than winter during this period. For the positive of summer LSI, the EP flux convergence induced by the land-sea thermal forcing in the high latitude becomes weaker than normal, which induces positive anomaly of zonal-mean westerly and double-jet structure. Based on the quasiresonance amplification mechanism, the narrow and reduced westerly tunnel between two jet centers provides a favor environment for more frequent blocking. Composite analysis demonstrates that summer blocking shows an increasing trend of event numbers and a decreasing trend of durations. The numbers of the short-lived blocking persisting for 5-9 days significantly increases and the numbers of the long-lived blocking persisting for longer than 10 days has a weak increase than that in negative phase of summer LSI. The increasing transient wave activities induced by summer LSI is responsible for the decreasing duration of blockings. The increasing blocking due to summer LSI can further strengthen the continent warming and increase the summer LSI, which forms a positive feedback. The opposite dynamical effect of LSI on summer and winter blocking are discussed and found that the LSI-blocking negative feedback partially reduces the influence of the above positive feedback and induce the weak summer warming rate.

Contrasting Trends in Arctic and Antarctic Sea Ice Coverage Since the Late 1970s

NASA Astrophysics Data System (ADS)

Parkinson, C. L.

2016-12-01

Satellite observations have allowed a near-continuous record of Arctic and Antarctic sea ice coverage since late 1978. This record has revealed considerable interannual variability in both polar regions but also significant long-term trends, with the Arctic losing, the Antarctic gaining, and the Earth as a whole losing sea ice coverage. Over the period 1979-2015, the trend in yearly average sea ice extents in the Arctic is -53,100 km2/yr (-4.3 %/decade) and in the Antarctic is 23,800 km2/yr (2.1 %/decade). For all 12 months, trends are negative in the Arctic and positive in the Antarctic, with the highest magnitude monthly trend being for September in the Arctic, at -85,300 km2/yr (-10.9 %/decade). The decreases in Arctic sea ice extents have been so dominant that not a single month since 1986 registered a new monthly record high, whereas 75 months registered new monthly record lows between 1987 and 2015 and several additional record lows were registered in 2016. The Antarctic sea ice record highs and lows are also out of balance, in the opposite direction, although not in such dramatic fashion. Geographic details on the changing ice covers, down to the level of individual pixels, can be seen by examining changes in the length of the sea ice season. Results reveal (and quantify) shortening ice seasons throughout the bulk of the Arctic marginal ice zone, the main exception being within the Bering Sea, and lengthening sea ice seasons through much of the Southern Ocean but shortening seasons in the Bellingshausen Sea, southern Amundsen Sea, and northwestern Weddell Sea. The decreasing Arctic sea ice coverage was widely anticipated and fits well with a large array of environmental changes in the Arctic, whereas the increasing Antarctic sea ice coverage was not widely anticipated and explaining it remains an area of active research by many scientists exploring a variety of potential explanations.

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.

The South China sea margins: Implications for rifting contrasts

USGS Publications Warehouse

Hayes, D.E.; Nissen, S.S.

2005-01-01

Implications regarding spatially complex continental rifting, crustal extension, and the subsequent evolution to seafloor spreading are re-examined for the northern and southern-rifted margins of the South China Sea. Previous seismic studies have shown dramatic differences in the present-day crustal thicknesses as the manifestations of the strain experienced during the rifting of the margin of south China. Although the total crustal extension is presumed to be the same along the margin and adjacent ocean basin, the amount of continental crustal extension that occurred is much less along the east and central segments of the margin than along the western segment. This difference was accommodated by the early formation of oceanic crust (creating the present-day South China Sea basin) adjacent to the eastern margin segment while continued extension of continental crust was sustained to the west. Using the observed cross-sectional areas of extended continental crust derived from deep penetration seismics, two end-member models of varying rift zone widths and varying initial crustal thicknesses are qualitatively examined for three transects. Each model implies a time difference in the initiation of seafloor spreading inferred for different segments along the margin. The two models examined predict that the oceanic crust of the South China Sea basin toward the west did not begin forming until sometime between 6-12 my after its initial formation (???32 Ma) toward the east. These results are compatible with crustal age interpretations of marine magnetic anomalies. Assuming rifting symmetry with conjugate margin segments now residing along the southern portions of the South China Sea basin implies that the total width of the zone of rifting in the west was greater than in the east by about a factor of two. We suggest the most likely causes of the rifting differences were east-west variations in the rheology of the pre-rift crust and associated east-west variations in the

Key roles of sea ice in inducing contrasting modes of glacial AMOC and climate

NASA Astrophysics Data System (ADS)

Sherriff-Tadano, S.; Abe-Ouchi, A.

2017-12-01

Gaining a better understanding of glacial Atlantic meridional overturning circulation (AMOC) is important to interpret the glacial climate changes such as the Heinrich event. Recent studies suggest that changes in sea ice over the North Atlantic largely affect the surface wind. Since changes in surface wind have a large impact on the AMOC, this implies a role of sea ice in modifying the AMOC though surface wind. However, the impact of sea ice on the surface winds and the impact of changes in the winds on the AMOC remain unclear. In this study, we first assess the impact of sea ice expansion on the winds. We then explore whether the changes in winds play a role in modifying the AMOC and climate. For this purpose, results from MIROC4m are analyzed (Kawamura et al. 2017). To clarify the impact of changes in sea ice on the surface wind, sensitivity experiments are conducted with an atmospheric general circulation model (AGCM). In the AGCM experiments, we modify the sea ice to extract the impact of sea ice on the winds. Partial decouple experiments are conducted with the coupled model MIROC4m, which we modify the surface winds to assess the impact of changes in the surface wind due to sea ice expansion on the AMOC. Results show that expansion of sea ice substantially weakens the surface wind over the northern North Atlantic. AGCM experiments show that a drastic decrease in surface temperature duo to a suppression of sensible heat flux plays a dominant role in weakening the surface winds through increasing the static stability of the air column near the surface. Partial decouple experiments with MIROC4m show that the weakening of the surface wind due to the expansion of sea ice plays an important role in maintaining the weak AMOC. Thus, these experiments show that the weakening of the surface winds due to sea ice expansion plays a role in stabilizing the AMOC.

Contrasting effects of heterozygosity on survival and hookworm resistance in California sea lion pups.

PubMed

Acevedo-Whitehouse, Karina; Spraker, Terry R; Lyons, Eugene; Melin, Sharon R; Gulland, Frances; Delong, Robert L; Amos, William

2006-06-01

Low genetic heterozygosity is associated with loss of fitness in many natural populations. However, it remains unclear whether the mechanism is related to general (i.e. inbreeding) or local effects, in particular from a subset of loci lying close to genes under balancing selection. Here we analyse involving heterozygosity-fitness correlations on neonatal survival of California sea lions and on susceptibility to hookworm (Uncinaria spp.) infection, the single most important cause of pup mortality. We show that regardless of differences in hookworm burden, homozygosity is a key predictor of hookworm-related lesions, with no single locus contributing disproportionately. Conversely, the subsequent occurrence of anaemia due to blood loss in infected pups is overwhelmingly associated with homozygosity at one particular locus, all other loci showing no pattern. Our results suggest contrasting genetic mechanisms underlying two pathologies related to the same pathogen. First, relatively inbred pups are less able to expel hookworms and prevent their attachment to the intestinal mucosa, possibly due to a weakened immune response. In contrast, infected pups that are homozygous for a gene near to microsatellite Hg4.2 are strongly predisposed to anaemia. As yet, this gene is unknown, but could plausibly be involved in the blood-coagulation cascade. Taken together, these results suggest that pathogenic burden alone may not be the main factor regulating pathogen-related mortality in natural populations. Our study could have important implications for the conservation of small, isolated or threatened populations, particularly when they are at a risk of facing pathogenic challenges.

Contrasting behavior of tungsten and molybdenum in the Okinawa Trough, the East China Sea and the Yellow Sea

NASA Astrophysics Data System (ADS)

Sohrin, Yoshiki; Matsui, Masakazu; Nakayama, Eiichiro

1999-10-01

By using catalytic current polarography and high-resolution inductively coupled plasma mass spectrometry, W and Mo in seawater were determined in the Okinawa Trough, a backarc rift, and in the East China Sea and the Yellow Sea. Mo was distributed conservatively throughout the study area, and its salinity-normalized concentration was 104 ± 6 nM (n = 105). W was also uniformly distributed south of the Kuroshio Current (56 ± 7 pM, n = 51). Anomalous high concentrations of W (maximum 254 pM) were found in the Iheya Graben in the middle Okinawa Trough (>1000 m depth), which were probably supplied by hydrothermal activity. The concentrations of Mo and W in the East China Sea and the Yellow Sea showed linear correlation with salinity (26 < S < 35). The Mo data can be explained by mixing of seawater and river water of the Changjiang (Mo = 10 nM; Qu et al., 1993). However, the values of W extrapolated to S = 0 were largely different between two cruises (1200 pM in May-June 1987 and 540 pM in June 1994) and much higher than the reported concentrations of 160 pM for world rivers by Turekian (1969) and 30 pM for unpolluted Japanese rivers by Sohrin et al. (1989). Moreover, significantly high W was observed in the bottom water at stations near the Changjiang River estuary and the western Yellow Sea. While these data may suggest that W is released from the anoxic sediments of the continental shelf, we need more data to elucidate the mechanism controlling the distribution of W.

Contrasts in Sea Ice Formation and Production in the Arctic Seasonal and Perennial Ice Zones

NASA Technical Reports Server (NTRS)

Kwok, R.

2006-01-01

Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. 3-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the mid-winter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m) - this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by: local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and, the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice.

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.

Contribution of atmospheric circulation to recent off-shore sea-level variations in the Baltic Sea and the North Sea

NASA Astrophysics Data System (ADS)

Karabil, Sitar; Zorita, Eduardo; Hünicke, Birgit

2018-01-01

The main purpose of this study is to quantify the contribution of atmospheric factors to recent off-shore sea-level variability in the Baltic Sea and the North Sea on interannual timescales. For this purpose, we statistically analysed sea-level records from tide gauges and satellite altimetry and several climatic data sets covering the last century. Previous studies had concluded that the North Atlantic Oscillation (NAO) is the main pattern of atmospheric variability affecting sea level in the Baltic Sea and the North Sea in wintertime. However, we identify a different atmospheric circulation pattern that is more closely connected to sea-level variability than the NAO. This circulation pattern displays a link to sea level that remains stable through the 20th century, in contrast to the much more variable link between sea level and the NAO. We denote this atmospheric variability mode as the Baltic Sea and North Sea Oscillation (BANOS) index. The sea-level pressure (SLP) BANOS pattern displays an SLP dipole with centres of action located over (5° W, 45° N) and (20° E, 70° N) and this is distinct from the standard NAO SLP pattern in wintertime. In summertime, the discrepancy between the SLP BANOS and NAO patterns becomes clearer, with centres of action of the former located over (30° E, 45° N) and (20° E, 60° N). This index has a stronger connection to off-shore sea-level variability in the study area than the NAO in wintertime for the period 1993-2013, explaining locally up to 90 % of the interannual sea-level variance in winter and up to 79 % in summer. The eastern part of the Gulf of Finland is the area where the BANOS index is most sensitive to sea level in wintertime, whereas the Gulf of Riga is the most sensitive region in summertime. In the North Sea region, the maximum sea-level sensitivity to the BANOS pattern is located in the German Bight for both winter and summer seasons. We investigated, and when possible quantified, the contribution of several

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.

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.

Contrasts in Sea Ice Deformation and Production in the Arctic Seasonal and Perennial Ice Zones

NASA Technical Reports Server (NTRS)

Kwok, K.

2006-01-01

Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. Three-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the midwinter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is seen in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m): this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. Uncertainties in these estimates are discussed. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice. Divergence is shown to be negligibly correlated to cyclonic motion in summer and winter in both ice zones.

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.

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.

Latitudinal and Longitudinal Basin-scale Surface Salinity Contrasts and Freshwater Transport by Ocean Thermohaline Circulation

NASA Astrophysics Data System (ADS)

Seidov, D.; Haupt, B. J.

2003-12-01

The role of sea surface salinity (SSS) contrasts in maintaining vigorous global ocean thermohaline circulation (THC) is revisited. Relative importance of different generalizations of sea surface conditions in climate studies is explored. In numerical experiments using an ocean general circulation model, we have aggregated the observed sea surface temperature (SST) and SSS in several different ways: we used observed unchanged SST with SSS taken as constant (34.25 psu) everywhere; SST unchanged, and SSS zonally averaged globally, i.e., in the whole World Ocean; SST averaged globally, and SSS unchanged; SST zonally averaged globally and SSS zonally averaged basin-wide in individual basins, i.e., in the Atlantic, Indian, Pacific, and Southern Oceans separately; and, finally, both SST and SSS zonally averaged in individual basins. Global zonal averaging removes all longitudinal differences in sea surface climatology among ocean basins. However, latitudinal profiles of zonally averaged parameters preserve the main character of large-scale equator-to-pole sea surface variability. Basin-wide zonal averaging does an even better job of preserving latitudinal distributions within each basin. The results of the experiments could hardly be anticipated a priory. Surprisingly, SST could be used as a 2-D field, or as a zonally-averaged field without much difference in the THC dynamics. Moreover, SST could be averaged either globally, or basin-wide, and it also did not change the overall character of THC. At the same time, THC responded vigorously to how the SSS has been changed. It appeared that the THC structure with the globally averaged SST and basin-wide averaged SSS was very close to the one obtained in the control run (control run operates with 2-D observed SST and SSS). Our main conclusion is that ocean-wide inter-basin sea surface salinity contrasts serve as the major controlling element in global thermohaline circulation. Thermal inter-basin contrasts, as well as

Experiments in Reconstructing Twentieth-Century Sea Levels

NASA Technical Reports Server (NTRS)

Ray, Richard D.; Douglas, Bruce C.

2011-01-01

One approach to reconstructing historical sea level from the relatively sparse tide-gauge network is to employ Empirical Orthogonal Functions (EOFs) as interpolatory spatial basis functions. The EOFs are determined from independent global data, generally sea-surface heights from either satellite altimetry or a numerical ocean model. The problem is revisited here for sea level since 1900. A new approach to handling the tide-gauge datum problem by direct solution offers possible advantages over the method of integrating sea-level differences, with the potential of eventually adjusting datums into the global terrestrial reference frame. The resulting time series of global mean sea levels appears fairly insensitive to the adopted set of EOFs. In contrast, charts of regional sea level anomalies and trends are very sensitive to the adopted set of EOFs, especially for the sparser network of gauges in the early 20th century. The reconstructions appear especially suspect before 1950 in the tropical Pacific. While this limits some applications of the sea-level reconstructions, the sensitivity does appear adequately captured by formal uncertainties. All our solutions show regional trends over the past five decades to be fairly uniform throughout the global ocean, in contrast to trends observed over the shorter altimeter era. Consistent with several previous estimates, the global sea-level rise since 1900 is 1.70 +/- 0.26 mm/yr. The global trend since 1995 exceeds 3 mm/yr which is consistent with altimeter measurements, but this large trend was possibly also reached between 1935 and 1950.

The North Sea goes viral: Occurrence and distribution of North Sea bacteriophages.

PubMed

Garin-Fernandez, Alexa; Pereira-Flores, Emiliano; Glöckner, Frank Oliver; Wichels, Antje

2018-06-01

Marine viruses are dominated by phages and have an enormous influence on microbial population dynamics, due to lysis and horizontal gene transfer. The aim of this study is to analyze the occurrence and diversity of phages in the North Sea, considering the virus-host interactions and biogeographic factors. The virus community of four sampling stations were described using virus metagenomics (viromes). The results show that the virus community was not evenly distributed throughout the North Sea. The dominant phage members were identified as unclassified phage group, followed by Caudovirales order. Myoviridae was the dominant phage family in the North Sea, which occurrence decreased from the coast to the open sea. In contrast, the occurrence of Podoviridae increased and the occurrence of Siphoviridae was low throughout the North Sea. The occurrence of other groups such as Phycodnaviridae decreased from the coast to the open sea. The coastal virus community was genetically more diverse than the open sea community. The influence of riverine inflow and currents, for instance the English Channel flow affects the genetic virus diversity with the community carrying genes from a variety of metabolic pathways and other functions. The present study offers the first insights in the virus community in the North Sea using viromes and shows the variation in virus diversity and the genetic information moved from coastal to open sea areas. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Effect of water turbidity on the visual acuity of harbor seals (Phoca vitulina).

PubMed

Weiffen, Michael; Möller, Bettina; Mauck, Björn; Dehnhardt, Guido

2006-05-01

The underwater visual acuity (the angle subtended by the minimal resolvable line width of high contrast square wave gratings at a viewing distance of 2m) of two male harbor seals was determined at different levels of water turbidity. Starting with visual acuity angles of 5.5' and 12.7' in clear water we found visual acuity to decrease rapidly with increasing turbidity at rates of 7.4' and 6.0' per formazin nephelometric unit (FNU). Besides the individual differences in visual performance of the harbor seals tested, our results reveal a dramatic loss of visual acuity even at moderate levels of turbidity. At sites in the German Wadden Sea, where harbor seals are known to roam and forage, we measured turbidity levels exceeding 40FNU. These data suggest that turbidity has to be considered as an important factor in the sensory ecology of pinnipeds.

The influence of global sea surface temperature variability on the large-scale land surface temperature

NASA Astrophysics Data System (ADS)

Tyrrell, Nicholas L.; Dommenget, Dietmar; Frauen, Claudia; Wales, Scott; Rezny, Mike

2015-04-01

In global warming scenarios, global land surface temperatures () warm with greater amplitude than sea surface temperatures (SSTs), leading to a land/sea warming contrast even in equilibrium. Similarly, the interannual variability of is larger than the covariant interannual SST variability, leading to a land/sea contrast in natural variability. This work investigates the land/sea contrast in natural variability based on global observations, coupled general circulation model simulations and idealised atmospheric general circulation model simulations with different SST forcings. The land/sea temperature contrast in interannual variability is found to exist in observations and models to a varying extent in global, tropical and extra-tropical bands. There is agreement between models and observations in the tropics but not the extra-tropics. Causality in the land-sea relationship is explored with modelling experiments forced with prescribed SSTs, where an amplification of the imposed SST variability is seen over land. The amplification of to tropical SST anomalies is due to the enhanced upper level atmospheric warming that corresponds with tropical moist convection over oceans leading to upper level temperature variations that are larger in amplitude than the source SST anomalies. This mechanism is similar to that proposed for explaining the equilibrium global warming land/sea warming contrast. The link of the to the dominant mode of tropical and global interannual climate variability, the El Niño Southern Oscillation (ENSO), is found to be an indirect and delayed connection. ENSO SST variability affects the oceans outside the tropical Pacific, which in turn leads to a further, amplified and delayed response of.

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

Contrasting effect of Saharan dust and UVR on autotrophic picoplankton in nearshore versus offshore waters of Mediterranean Sea

NASA Astrophysics Data System (ADS)

González-Olalla, J. M.; Medina-Sánchez, J. M.; Cabrerizo, M. J.; Villar-Argáiz, Manuel; Sánchez-Castillo, Pedro M.; Carrillo, Presentación

2017-08-01

Autotrophic picoplankton (APP) is responsible for the vast majority of primary production in oligotrophic marine areas, such as the Alboran Sea. The increase in atmospheric dust deposition (e.g., from Sahara Desert) associated with global warming, together with the high UV radiation (UVR) on these ecosystems, may generate effects on APP hitherto unknown. We performed an observational study across the Alboran Sea to establish which factors control the abundance and distribution of APP, and we made a microcosm experiment in two distinct areas, nearshore and offshore, to predict the joint UVR × dust impact on APP at midterm scales. Our observational study showed that temperature (T) was the main factor explaining the APP distribution whereas total dissolved nitrogen positively correlated with APP abundance. Our experimental study revealed that Saharan dust inputs reduced or inverted the UVR damage on the photosynthetic quantum yield (ΦPSII) and picoplanktonic primary production (PPP) in the nearshore area but accentuated it in the offshore. This contrasting effect is partially explained by the nonphotochemical quenching, acting as a photorepair mechanism. Picoeukaryotes reflected the observed effects on the physiological and metabolic variables, and Synechococcus was the only picoprokaryotic group that showed a positive response under UVR × dust conditions. Our study highlights a dual sensitivity of nearshore versus offshore picoplankton to dust inputs and UVR fluxes, just at the time in which these two global-change factors show their highest intensities and may recreate a potential future response of the microbial food web under global-change conditions.

Satellite Remote Sensing: Passive-Microwave Measurements of Sea Ice

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

Satellite passive-microwave measurements of sea ice have provided global or near-global sea ice data for most of the period since the launch of the Nimbus 5 satellite in December 1972, and have done so with horizontal resolutions on the order of 25-50 km and a frequency of every few days. These data have been used to calculate sea ice concentrations (percent areal coverages), sea ice extents, the length of the sea ice season, sea ice temperatures, and sea ice velocities, and to determine the timing of the seasonal onset of melt as well as aspects of the ice-type composition of the sea ice cover. In each case, the calculations are based on the microwave emission characteristics of sea ice and the important contrasts between the microwave emissions of sea ice and those of the surrounding liquid-water medium.

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.

Contrasting Photophysiological Characteristics of Phytoplankton Assemblages in the Northern South China Sea.

PubMed

Jin, Peng; Gao, Guang; Liu, Xin; Li, Futian; Tong, Shanying; Ding, Jiancheng; Zhong, Zhihai; Liu, Nana; Gao, Kunshan

2016-01-01

The growth of phytoplankton and thus marine primary productivity depend on photophysiological performance of phytoplankton cells that respond to changing environmental conditions. The South China Sea (SCS) is the largest marginal sea of the western Pacific and plays important roles in modulating regional climate and carbon budget. However, little has been documented on photophysiological characteristics of phytoplankton in the SCS. For the first time, we investigated photophysiological characteristics of phytoplankton assemblages in the northern South China Sea (NSCS) using a real-time in-situ active chlorophyll a fluorometry, covering 4.0 × 105 km2. The functional absorption cross section of photosystem II (PSII) in darkness (σPSII) or under ambient light (σPSII') (A2 quanta-1) increased from the surface to deeper waters at all the stations during the survey period (29 July to 23 August 2012). While the maximum (Fv/Fm, measured in darkness) or effective (Fq'/Fm', measured under ambient light) photochemical efficiency of PSII appeared to increase with increasing depth at most stations, it showed inverse relationship with depth in river plume areas. The functional absorption cross section of PSII changes could be attributed to light-adapted genotypic feature due to niche-partition and the alteration of photochemical efficiency of PSII could be attributed to photo-acclimation. The chlorophyll a fluorometry can be taken as an analog to estimate primary productivity, since areas of higher photochemical efficiency of PSII coincided with those of higher primary productivity reported previously in the NSCS.

Limits on the adaptability of coastal marshes to rising sea level

USGS Publications Warehouse

Kirwan, Matthew L.; Guntenspergen, Glenn R.; D'Alpaos, Andrea; Morris, James T.; Mudd, Simon M.; Temmerman, Stijn

2010-01-01

Assumptions of a static landscape inspire predictions that about half of the world's coastal wetlands will submerge during this century in response to sea-level acceleration. In contrast, we use simulations from five numerical models to quantify the conditions under which ecogeomorphic feedbacks allow coastal wetlands to adapt to projected changes in sea level. In contrast to previous sea-level assessments, we find that non-linear feedbacks among inundation, plant growth, organic matter accretion, and sediment deposition, allow marshes to survive conservative projections of sea-level rise where suspended sediment concentrations are greater than ~20 mg/L. Under scenarios of more rapid sea-level rise (e.g., those that include ice sheet melting), marshes will likely submerge near the end of the 21st century. Our results emphasize that in areas of rapid geomorphic change, predicting the response of ecosystems to climate change requires consideration of the ability of biological processes to modify their physical environment.

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.

Re-initiation of bottom water formation in the East Sea (Japan Sea) in a warming world.

PubMed

Yoon, Seung-Tae; Chang, Kyung-Il; Nam, SungHyun; Rho, TaeKeun; Kang, Dong-Jin; Lee, Tongsup; Park, Kyung-Ae; Lobanov, Vyacheslav; Kaplunenko, Dmitry; Tishchenko, Pavel; Kim, Kyung-Ryul

2018-01-25

The East Sea (Japan Sea), a small marginal sea in the northwestern Pacific, is ventilated deeply down to the bottom and sensitive to changing surface conditions. Addressing the response of this marginal sea to the hydrological cycle and atmospheric forcing would be helpful for better understanding present and future environmental changes in oceans at the global and regional scales. Here, we present an analysis of observations revealing a slowdown of the long-term deepening in water boundaries associated with changes of water formation rate. Our results indicate that bottom (central) water formation has been enhanced (reduced) with more (less) oxygen supply to the bottom (central) layer since the 2000s. This paper presents a new projection that allows a three-layered deep structure, which retains bottom water, at least until 2040, contrasting previous results. This projection considers recent increase of slope convections mainly due to the salt supply via air-sea freshwater exchange and sea ice formation and decrease of open-ocean convections evidenced by reduced mixed layer depth in the northern East Sea, resulting in more bottom water and less central water formations. Such vigorous changes in water formation and ventilation provide certain implications on future climate changes.

Links between seawater flooding, soil ammonia oxidiser communities and their response to changes in salinity.

PubMed

Nacke, Heiko; Schöning, Ingo; Schindler, Malte; Schrumpf, Marion; Daniel, Rolf; Nicol, Graeme W; Prosser, James I

2017-11-01

Coastal areas worldwide are challenged by climate change-associated increases in sea level and storm surge quantities that potentially lead to more frequent flooding of soil ecosystems. Currently, little is known of the effects of inundation events on microorganisms controlling nitrification in these ecosystems. The goal of this study was to investigate the impact of seawater flooding on the abundance, community composition and salinity tolerance of soil ammonia oxidisers. Topsoil was sampled from three islands flooded at different frequencies by the Wadden Sea. Archaeal ammonia oxidiser amoA genes were more abundant than their betaproteobacterial counterparts, and the distribution of archaeal and bacterial ammonia oxidiser amoA and 16S rRNA gene sequences significantly differed between the islands. The findings indicate selection of ammonia oxidiser phylotypes with greater tolerance to high salinity and slightly alkaline pH (e.g. Nitrosopumilus representatives) in frequently flooded soils. A cluster phylogenetically related to gammaproteobacterial ammonia oxidisers was detected in all samples analysed in this survey. Nevertheless, no gammaprotebacterial amoA genes could be amplified via PCR and only betaproteobacterial ammonia oxidisers were detected in enrichment cultures. A slurry-based experiment demonstrated the tolerance of both bacterial and archaeal ammonia oxidisers to a wide range of salinities (e.g. Wadden Sea water salinity) in soil naturally exposed to seawater at a high frequency. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The role of ecological divergence in speciation between intertidal and subtidal Scoloplos armiger (Polychaeta, Orbiniidae)

NASA Astrophysics Data System (ADS)

Kruse, Inken; Strasser, Matthias; Thiermann, Frank

2004-02-01

The concept of ecological speciation implies that habitat differences may split a species by strong selection and rapid adaptation even under sympatric conditions. Studies on the polychaete Scoloplos armiger in the Wadden Sea (North Sea) indicate sibling species existing in sympatry: the intertidal 'Type I' with holobenthic development out of egg cocoons and the subtidal 'Type S' producing pelagic larvae. In the current study, Types I and S are compared in habitat-related traits of reproductive timing and physiological response to hypoxia and sulphide. Spawnings of Type I and Type S recorded over six years overlap in spring and both appear to be triggered by a rise in seawater temperature above 5 °C. Type S exhibits an additional autumn spawning (at seawater temperatures around 10 °C) which was previously unknown and is absent in Type I. The overall abundance of pelagic larvae in the Wadden Sea is higher in spring than in autumn. Tolerance of both sulphide and hypoxia was lower in Type S than in Type I. This correlates with a 5 to 10-fold lower sulphide concentration in the subtidal compared to the intertidal habitat. Physiological tolerance and divergence in developmental mode appear as traits which may have led to reproductive isolation between Type I and Type S. Their role in allopatric and sympatric speciation scenarios in S. armiger is discussed. Since the pelagic dispersal mode has been neglected so far, a reassessment of population dynamics models for S. armiger is suggested.

Eustatic sea level fluctuations induced by polar wander

NASA Technical Reports Server (NTRS)

Sabadini, Roberto; Doglioni, Carlo; Yuen, David A.

1990-01-01

It is shown here that polar wander of a viscoelastic, stratified earth can induce global sea level fluctuations comparable to the short-term component in eustatic sea-level curves. The sign of these fluctuations, which are very sensitive to the rheological stratification, depends on the geographical location of the observation point; rises and falls in sea level can thus be coeval in different parts of the world. This finding is a distinct contrast to the main assumption underlying the reconstruction of eustatic curves, namely that global sea-level events produce the same depositional sequence everywhere. It is proposed that polar wander should be added to the list of geophysical mechanisms that can control the third-order cycles in sea level.

30-Year Satellite Record Reveals Accelerated Arctic Sea Ice Loss, Antarctic Sea Ice Trend Reversal

NASA Technical Reports Server (NTRS)

Cavalieri, Donald J.; Parkinson, C. L.; Vinnikov, K. Y.

2003-01-01

Arctic sea ice extent decreased by 0.30 plus or minus 0.03 x 10(exp 6) square kilometers per decade from 1972 through 2002, but decreased by 0.36 plus or minus 0.05 x 10(exp 6) square kilometers per decade from 1979 through 2002, indicating an acceleration of 20% in the rate of decrease. In contrast to the Arctic, the Antarctic sea ice extent decreased dramatically over the period 1973-1977, then gradually increased, with an overall 30-year trend of -0.15 plus or minus 0.08 x 10(exp 6) square kilometers per 10yr. The trend reversal is attributed to a large positive anomaly in Antarctic sea ice extent observed in the early 1970's.

An inversion of the estuarine circulation by sluice water discharge and its impact on suspended sediment transport

NASA Astrophysics Data System (ADS)

Schulz, Kirstin; Gerkema, Theo

2018-01-01

The Wadden Sea is characterized by a complex topography of branching channels and intertidal flats, in which the interplay between fresh water discharges, wind forcing and the tidal current causes sediment transport rates and direction to be highly variable in space and time. During three field campaigns, indications of a negative estuarine circulation have been found in a channel adjacent to the coast in the Western Dutch Wadden Sea. Contrary to the classical picture of estuarine circulation, a periodic density stratification was observed that builds up during flood and breaks down during ebb. This can be related to a large freshwater source at the mouth of the channel, the sluice in Kornwerderzand. In this study, observations of this phenomenon are presented, and with the help of a numerical model the different drivers for residual suspended matter transport in this area, namely tidal asymmetries in the current velocity and the above mentioned periodic stratification, are investigated. It is found that the residual current in the area of interest points in ebb direction, caused by both the elongated ebb flow phase and the periodic stratification. On the contrary, the stronger flood currents cause a transport of suspended matter in flood direction. This transport is counteracted and therefore diminished by the effects of the sluice discharge.

The role of environmental variables in structuring landscape-scale species distributions in seafloor habitats.

PubMed

Kraan, Casper; Aarts, Geert; Van der Meer, Jaap; Piersma, Theunis

2010-06-01

Ongoing statistical sophistication allows a shift from describing species' spatial distributions toward statistically disentangling the possible roles of environmental variables in shaping species distributions. Based on a landscape-scale benthic survey in the Dutch Wadden Sea, we show the merits of spatially explicit generalized estimating equations (GEE). The intertidal macrozoobenthic species, Macoma balthica, Cerastoderma edule, Marenzelleria viridis, Scoloplos armiger, Corophium volutator, and Urothoe poseidonis served as test cases, with median grain-size and inundation time as typical environmental explanatory variables. GEEs outperformed spatially naive generalized linear models (GLMs), and removed much residual spatial structure, indicating the importance of median grain-size and inundation time in shaping landscape-scale species distributions in the intertidal. GEE regression coefficients were smaller than those attained with GLM, and GEE standard errors were larger. The best fitting GEE for each species was used to predict species' density in relation to median grain-size and inundation time. Although no drastic changes were noted compared to previous work that described habitat suitability for benthic fauna in the Wadden Sea, our predictions provided more detailed and unbiased estimates of the determinants of species-environment relationships. We conclude that spatial GEEs offer the necessary methodological advances to further steps toward linking pattern to process.

A case study of sea breeze blocking regulated by sea surface temperature along the English south coast

NASA Astrophysics Data System (ADS)

Sweeney, J. K.; Chagnon, J. M.; Gray, S. L.

2014-05-01

The sensitivity of sea breeze structure to sea surface temperature (SST) and coastal orography is investigated in convection-permitting Met Office Unified Model simulations of a case study along the south coast of England. Changes in SST of 1 K are shown to significantly modify the structure of the sea breeze immediately offshore. On the day of the case study, the sea breeze was partially blocked by coastal orography, particularly within Lyme Bay. The extent to which the flow is blocked depends strongly on the static stability of the marine boundary layer. In experiments with colder SST, the marine boundary layer is more stable, and the degree of blocking is more pronounced. Although a colder SST would also imply a larger land-sea temperature contrast and hence a stronger onshore wind - an effect which alone would discourage blocking - the increased static stability exerts a dominant control over whether blocking takes place. The implications of prescribing fixed SST from climatology in numerical weather prediction model forecasts of the sea breeze are discussed.

Epibenthic communities associated with unintentional artificial reefs (modern shipwrecks) under contrasting regimes of nutrients in the Levantine Sea (Cyprus and Lebanon)

PubMed Central

Andreou, Vasilis; Evriviadou, Marina; Munkes, Britta; Hadjioannou, Louis; Petrou, Antonis; Abu Alhaija, Rana

2017-01-01

Artificial reefs, in the Eastern Mediterranean (Cyprus,) became a popular and frequently used tool, in fisheries and biodiversity conservation management. Even though evaluation studies about the efficacy of artificial reefs are plentiful in the rest of the Mediterranean (Central and Western), in the Eastern Basin they are largely absent. As the Eastern part of the Mediterranean Sea is characterised by unique physical parameters, the necessity to study artificial reefs under these contrasting regimes increases. The epibenthic communities of two unintentional artificial reefs (modern shipwrecks) in Cyprus (Zenobia) and Lebanon (Alice-B) were evaluated in 2010. Both shipwrecks are at similar depth, type of sea bottom, made of the same material (steel) and were sunk approximately the same period of time. However, Alice-B shipwreck off the coast of Lebanon is constantly exposed to higher levels of nutrients than Zenobia in Cyprus. Significant dissimilarities were observed in the composition, percentage of benthic cover of predominant taxonomic groups and development of the epibenthic communities. Differences in physical and chemical parameters between sides lay mainly in the nutrient and thermal regimes affecting the shipwrecks and most likely bring about the differences in the observed community structure. The results of this study suggest that epibenthic communities could be highly impacted by eutrophication caused by anthropogenic activities, leading to less biodiverse communities dominated by specific species that are favoured by the eutrophic conditions. PMID:28850572

Simulation of an oil film at the sea surface and its radiometric properties in the SWIR

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Van Eijk, Alexander M. J.

2017-10-01

The knowledge of the optical contrast of an oil layer on the sea under various surface roughness conditions is of great interest for oil slick monitoring techniques. This paper presents a 3D simulation of a dynamic sea surface contaminated by a floating oil film. The simulation considers the damping influence of oil on the ocean waves and its physical properties. It calculates the radiance contrast of the sea surface polluted by the oil film in relation to a clean sea surface for the SWIR spectral band. Our computer simulation combines the 3D simulation of a maritime scene (open clear sea/clear sky) with an oil film at the sea surface. The basic geometry of a clean sea surface is modeled by a composition of smooth wind driven gravity waves. Oil on the sea surface attenuates the capillary and short gravity waves modulating the wave power density spectrum of these waves. The radiance of the maritime scene is calculated in the SWIR spectral band with the emitted sea surface radiance and the specularly reflected sky radiance as components. Wave hiding and shadowing, especially occurring at low viewing angles, are considered. The specular reflection of the sky radiance at the clean sea surface is modeled by an analytical statistical bidirectional reflectance distribution function (BRDF) of the sea surface. For oil at the sea surface, a specific BRDF is used influenced by the reduced surface roughness, i.e., the modulated wave density spectrum. The radiance contrast of an oil film in relation to the clean sea surface is calculated for different viewing angles, wind speeds, and oil types characterized by their specific physical properties.

Aircraft measurements of microwave emission from Arctic Sea ice

USGS Publications Warehouse

Wilheit, T.; Nordberg, W.; Blinn, J.; Campbell, W.; Edgerton, A.

1971-01-01

Measurements of the microwave emission from Arctic Sea ice were made with aircraft at 8 wavelengths ranging from 0.510 to 2.81 cm. The expected contrast in emissivities between ice and water was observed at all wavelengths. Distributions of sea ice and open water were mapped from altitudes up to 11 km in the presence of dense cloud cover. Different forms of ice also exhibited strong contrasts in emissivity. Emissivity differences of up to 0.2 were observed between two types of ice at the 0.811-cm wavelength. The higher emissivity ice type is tentatively identified as having been formed more recently than the lower emissivity ice. ?? 1971.

Aircraft measurements of microwave emission from Arctic Sea Ice

NASA Technical Reports Server (NTRS)

Wilheit, T. T.; Blinn, J.; Campbell, W. J.; Edgerton, A. T.; Nordberg, W.

1971-01-01

Measurements of the microwave emission from Arctic Sea ice were made with aircraft at 8 wavelengths ranging from 0.510 cm to 2.81 cm. The expected contrast in emissivities between ice and water was observed at all wavelengths. Distributions of sea ice and open water were mapped from altitudes up to 11 km in the presence of dense cloud cover. Different forms of ice also exhibited strong contrasts in emissivity. Emissivity differences of up to 0.2 were observed between two types of ice at 0.811 cm wavelength. The higher emissivity ice type is tentatively identified as having been formed more recently than the lower emissivity ice.

Genetic connectivity between land and sea: the case of the beachflea Orchestia montagui (Crustacea, Amphipoda, Talitridae) in the Mediterranean Sea.

PubMed

Pavesi, Laura; Tiedemann, Ralph; De Matthaeis, Elvira; Ketmaier, Valerio

2013-04-25

We examined patterns of genetic divergence in 26 Mediterranean populations of the semi-terrestrial beachflea Orchestia montagui using mitochondrial (cytochrome oxidase subunit I), microsatellite (eight loci) and allozymic data. The species typically forms large populations within heaps of dead seagrass leaves stranded on beaches at the waterfront. We adopted a hierarchical geographic sampling to unravel population structure in a species living at the sea-land transition and, hence, likely subjected to dramatically contrasting forces. Mitochondrial DNA showed historical phylogeographic breaks among Adriatic, Ionian and the remaining basins (Tyrrhenian, Western and Eastern Mediterranean Sea) likely caused by the geological and climatic changes of the Pleistocene. Microsatellites (and to a lesser extent allozymes) detected a further subdivision between and within the Western Mediterranean and the Tyrrhenian Sea due to present-day processes. A pattern of isolation by distance was not detected in any of the analyzed data set. We conclude that the population structure of O. montagui is the result of the interplay of two contrasting forces that act on the species population genetic structure. On one hand, the species semi-terrestrial life style would tend to determine the onset of local differences. On the other hand, these differences are partially counter-balanced by passive movements of migrants via rafting on heaps of dead seagrass leaves across sites by sea surface currents. Approximate Bayesian Computations support dispersal at sea as prevalent over terrestrial regionalism.

Genetic connectivity between land and sea: the case of the beachflea Orchestia montagui (Crustacea, Amphipoda, Talitridae) in the Mediterranean Sea

PubMed Central

2013-01-01

Introduction We examined patterns of genetic divergence in 26 Mediterranean populations of the semi-terrestrial beachflea Orchestia montagui using mitochondrial (cytochrome oxidase subunit I), microsatellite (eight loci) and allozymic data. The species typically forms large populations within heaps of dead seagrass leaves stranded on beaches at the waterfront. We adopted a hierarchical geographic sampling to unravel population structure in a species living at the sea-land transition and, hence, likely subjected to dramatically contrasting forces. Results Mitochondrial DNA showed historical phylogeographic breaks among Adriatic, Ionian and the remaining basins (Tyrrhenian, Western and Eastern Mediterranean Sea) likely caused by the geological and climatic changes of the Pleistocene. Microsatellites (and to a lesser extent allozymes) detected a further subdivision between and within the Western Mediterranean and the Tyrrhenian Sea due to present-day processes. A pattern of isolation by distance was not detected in any of the analyzed data set. Conclusions We conclude that the population structure of O. montagui is the result of the interplay of two contrasting forces that act on the species population genetic structure. On one hand, the species semi-terrestrial life style would tend to determine the onset of local differences. On the other hand, these differences are partially counter-balanced by passive movements of migrants via rafting on heaps of dead seagrass leaves across sites by sea surface currents. Approximate Bayesian Computations support dispersal at sea as prevalent over terrestrial regionalism. PMID:23618554

Contrasting seasonality in optical-biogeochemical properties of the Baltic Sea.

PubMed

Simis, Stefan G H; Ylöstalo, Pasi; Kallio, Kari Y; Spilling, Kristian; Kutser, Tiit

2017-01-01

Optical-biogeochemical relationships of particulate and dissolved organic matter are presented in support of remote sensing of the Baltic Sea pelagic. This system exhibits strong seasonality in phytoplankton community composition and wide gradients of chromophoric dissolved organic matter (CDOM), properties which are poorly handled by existing remote sensing algorithms. Absorption and scattering properties of particulate matter reflected the seasonality in biological (phytoplankton succession) and physical (thermal stratification) processes. Inherent optical properties showed much wider variability when normalized to the chlorophyll-a concentration compared to normalization to either total suspended matter dry weight or particulate organic carbon. The particle population had the largest optical variability in summer and was dominated by organic matter in both seasons. The geographic variability of CDOM and relationships with dissolved organic carbon (DOC) are also presented. CDOM dominated light absorption at blue wavelengths, contributing 81% (median) of the absorption by all water constituents at 400 nm and 63% at 442 nm. Consequentially, 90% of water-leaving radiance at 412 nm originated from a layer (z90) no deeper than approximately 1.0 m. With water increasingly attenuating light at longer wavelengths, a green peak in light penetration and reflectance is always present in these waters, with z90 up to 3.0-3.5 m depth, whereas z90 only exceeds 5 m at biomass < 5 mg Chla m-3. High absorption combined with a weakly scattering particle population (despite median phytoplankton biomass of 14.1 and 4.3 mg Chla m-3 in spring and summer samples, respectively), characterize this sea as a dark water body for which dedicated or exceptionally robust remote sensing techniques are required. Seasonal and regional optical-biogeochemical models, data distributions, and an extensive set of simulated remote-sensing reflectance spectra for testing of remote sensing algorithms are

Contrasting seasonality in optical-biogeochemical properties of the Baltic Sea

PubMed Central

Ylöstalo, Pasi; Kallio, Kari Y.; Spilling, Kristian; Kutser, Tiit

2017-01-01

Optical-biogeochemical relationships of particulate and dissolved organic matter are presented in support of remote sensing of the Baltic Sea pelagic. This system exhibits strong seasonality in phytoplankton community composition and wide gradients of chromophoric dissolved organic matter (CDOM), properties which are poorly handled by existing remote sensing algorithms. Absorption and scattering properties of particulate matter reflected the seasonality in biological (phytoplankton succession) and physical (thermal stratification) processes. Inherent optical properties showed much wider variability when normalized to the chlorophyll-a concentration compared to normalization to either total suspended matter dry weight or particulate organic carbon. The particle population had the largest optical variability in summer and was dominated by organic matter in both seasons. The geographic variability of CDOM and relationships with dissolved organic carbon (DOC) are also presented. CDOM dominated light absorption at blue wavelengths, contributing 81% (median) of the absorption by all water constituents at 400 nm and 63% at 442 nm. Consequentially, 90% of water-leaving radiance at 412 nm originated from a layer (z90) no deeper than approximately 1.0 m. With water increasingly attenuating light at longer wavelengths, a green peak in light penetration and reflectance is always present in these waters, with z90 up to 3.0–3.5 m depth, whereas z90 only exceeds 5 m at biomass < 5 mg Chla m-3. High absorption combined with a weakly scattering particle population (despite median phytoplankton biomass of 14.1 and 4.3 mg Chla m-3 in spring and summer samples, respectively), characterize this sea as a dark water body for which dedicated or exceptionally robust remote sensing techniques are required. Seasonal and regional optical-biogeochemical models, data distributions, and an extensive set of simulated remote-sensing reflectance spectra for testing of remote sensing algorithms

Coupled sea surface temperature-seawater δ18O reconstructions in the Arabian Sea at the millennial scale for the last 35 ka

NASA Astrophysics Data System (ADS)

Anand, Pallavi; Kroon, Dick; Singh, Arun Deo; Ganeshram, Raja S.; Ganssen, Gerald; Elderfield, Henry

2008-12-01

Two sediment cores from the western (905; 10.46°9'N, 51.56°4'E, water depth 1586 m) and eastern (SK17; 15°15'N, 72°58'E, water depth 840 m) Arabian Sea were used to study past sea surface temperatures (SST) and seawater δ18O (δ18Ow) variations for the past 35 ka. We used coupled Mg/Ca-δ18O calcite variability in two planktonic foraminiferal species: Globigerinoides ruber, which thrives throughout the year, and Globigerina bulloides, which occurs mainly when surface waters contain high nutrients during upwelling or convective mixing. SSTs in both areas based on Mg/Ca in G. ruber were ˜3 to 4°C lower during the Last Glacial Maximum (LGM; ˜21 ka) than today and the Holocene period. The SST records based on G. bulloides also indicate general cooling, down to 18°C in both areas. SSTs in the western Arabian Sea based on G. bulloides were always lower than those based on G. ruber, indicating the presence of strong seasonal temperature contrast during the Holocene and LGM. We interpret the consistent presence of this seasonal temperature contrast to reflect a combination of seasonal summer upwelling (SW monsoon) and winter convective mixing (NE monsoon) in the western Arabian Sea. In the eastern Arabian Sea, G. bulloides-based SSTs were slightly lower (about 1°C) than G. ruber-based SSTs during the Holocene, indicating the almost absence of a seasonal temperature gradient, similar to today. However, a large seasonal temperature contrast occurred during the LGM which favors the assumption that strong NE monsoon winds forced winter upwelling or convective mixing offshore Goa. SST and δ18Ow reconstructions reveal evidence of millennial-scale cycles, particularly in the eastern Arabian Sea. Here, the stadial periods (Northern Hemisphere cold periods such as Younger Dryas and Heinrich events) are marked by increasing SSTs and salty sea surface conditions relative to those during the interstadial periods. Indeed, the δ18Ow record shows evidence of low

Perception of airborne odors by loggerhead sea turtles.

PubMed

Endres, C S; Putman, N F; Lohmann, K J

2009-12-01

Sea turtles are known to detect chemical cues, but in contrast to most marine animals, turtles surface to breathe and thus potentially have access to olfactory cues both in air and in water. To determine whether sea turtles can detect airborne chemical cues, captive loggerhead turtles (Caretta caretta) were placed into a circular, water-filled arena in which odorants could be introduced to the air above the water surface. Air that had passed across the surface of a cup containing food elicited increased activity, diving and other behavior normally associated with feeding. By contrast, air that had passed across the surface of an identical cup containing distilled water elicited no response. Increases in activity during food odor trials occurred only after turtles surfaced to breathe and peaked in the first post-breath minute, implying that the chemical cues eliciting the responses were unlikely to have been detected while the turtles were under water. These results provide the first direct evidence that sea turtles can detect airborne odors. Under natural conditions, this sensory ability might function in foraging, navigation or both.

Indo-Pacific sea level variability during recent decades

NASA Astrophysics Data System (ADS)

Yamanaka, G.; Tsujino, H.; Nakano, H.; Urakawa, S. L.; Sakamoto, K.

2016-12-01

Decadal variability of sea level in the Indo-Pacific region is investigated using a historical OGCM simulation. The OGCM driven by the atmospheric forcing removing long-term trends clearly exhibits decadal sea level variability in the Pacific Ocean, which is associated with eastern tropical Pacific thermal anomalies. During the period of 1977-1987, the sea level anomalies are positive in the eastern equatorial Pacific and show deviations from a north-south symmetric distribution, with strongly negative anomalies in the western tropical South Pacific. During the period of 1996-2006, in contrast, the sea level anomalies are negative in the eastern equatorial Pacific and show a nearly north-south symmetric pattern, with positive anomalies in both hemispheres. Concurrently, sea level anomalies in the south-eastern Indian Ocean vary with those in the western tropical Pacific. These sea level variations are closely related to large-scale wind fields. Indo-Pacific sea level distributions are basically determined by wind anomalies over the equatorial region as well as wind stress curl anomalies over the off-equatorial region.

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.

Idealized WRF model sensitivity simulations of sea breeze types and their effects on offshore windfields

NASA Astrophysics Data System (ADS)

Steele, C. J.; Dorling, S. R.; von Glasow, R.; Bacon, J.

2012-06-01

The behaviour and characteristics of the marine component of sea breeze cells have received little attention relative to their onshore counterparts. Yet there is a growing interest and dependence on the offshore wind climate from, for example, a wind energy perspective. Using idealized model experiments, we investigate the sea breeze circulation at scales which approximate to those of the Southern North Sea, a region of major ongoing offshore wind farm development. We also contrast the scales and characteristics of the pure and the little known corkscrew and backdoor sea breeze types, where the type is pre-defined by the orientation of the synoptic scale flow relative to the shoreline. We find, crucially, that pure sea breezes, in contrast to corkscrew and backdoor types, can lead to substantial wind speed reductions offshore and that the addition of a second eastern coastline emphasises this effect through generation of offshore "calm zones". The offshore extent of all sea breeze types is found to be sensitive to both the influence of Coriolis acceleration and to the boundary layer scheme selected. These extents range, for example for a pure sea breeze produced in a 2 m s-1 offshore gradient wind, from 10 km to 40 km between the Mellor-Yamada-Nakanishi-Niino and the Yonsei State University schemes, respectively. The corkscrew type restricts the development of a backdoor sea breeze on the eastern coast and is also capable of traversing a 100 km offshore domain even under high gradient wind speed (>15 m s-1) conditions. Realistic variations in sea surface skin temperature during the sea breeze season do not significantly affect the circulation, suggesting that a thermal contrast is only needed as a precondition to the development of the sea breeze. We highlight how sea breeze impacts on circulation need to be considered in order to improve the accuracy of assessments of the offshore wind energy climate.

Idealized WRF model sensitivity simulations of sea breeze types and their effects on offshore windfields

NASA Astrophysics Data System (ADS)

Steele, C. J.; Dorling, S. R.; von Glasow, R.; Bacon, J.

2013-01-01

The behaviour and characteristics of the marine component of sea breeze cells have received little attention relative to their onshore counterparts. Yet there is a growing interest and dependence on the offshore wind climate from, for example, a wind energy perspective. Using idealized model experiments, we investigate the sea breeze circulation at scales which approximate to those of the southern North Sea, a region of major ongoing offshore wind farm development. We also contrast the scales and characteristics of the pure and the little known corkscrew and backdoor sea breeze types, where the type is pre-defined by the orientation of the synoptic scale flow relative to the shoreline. We find, crucially, that pure sea breezes, in contrast to corkscrew and backdoor types, can lead to substantial wind speed reductions offshore and that the addition of a second eastern coastline emphasises this effect through generation of offshore "calm zones". The offshore extent of all sea breeze types is found to be sensitive to both the influence of Coriolis acceleration and to the boundary layer scheme selected. These extents range, for example for a pure sea breeze produced in a 2 m s-1 offshore gradient wind, from 0 km to 21 km between the Mellor-Yamada-Nakanishi-Niino and the Yonsei State University schemes respectively. The corkscrew type restricts the development of a backdoor sea breeze on the opposite coast and is also capable of traversing a 100 km offshore domain even under high along-shore gradient wind speed (>15 m s-1) conditions. Realistic variations in sea surface skin temperature and initializing vertical thermodynamic profile do not significantly alter the resulting circulation, though the strengths of the simulated sea breezes are modulated if the effective land-sea thermal contrast is altered. We highlight how sea breeze impacts on circulation need to be considered in order to improve the accuracy of both assessments of the offshore wind energy climate and

Shellfish dredging pushes a flexible avian top predator out of a marine protected area.

PubMed

van Gils, Jan A; Piersma, Theunis; Dekinga, Anne; Spaans, Bernard; Kraan, Casper

2006-11-01

There is a widespread concern about the direct and indirect effects of industrial fisheries; this concern is particularly pertinent for so-called "marine protected areas" (MPAs), which should be safeguarded by national and international law. The intertidal flats of the Dutch Wadden Sea are a State Nature Monument and are protected under the Ramsar convention and the European Union's Habitat and Birds Directives. Until 2004, the Dutch government granted permission for ~75% of the intertidal flats to be exploited by mechanical dredgers for edible cockles (Cerastoderma edule). Here we show that dredged areas belonged to the limited area of intertidal flats that were of sufficient quality for red knots (Calidris canutus islandica), a long-distance migrant molluscivore specialist, to feed. Dredging led to relatively lower settlement rates of cockles and also reduced their quality (ratio of flesh to shell). From 1998 to 2002, red knots increased gizzard mass to compensate for a gradual loss in shellfish quality, but this compensation was not sufficient and led to decreases in local survival. Therefore, the gradual destruction of the necessary intertidal resources explains both the loss of red knots from the Dutch Wadden Sea and the decline of the European wintering population. This study shows that MPAs that do not provide adequate protection from fishing may fail in their conservation objectives.

Shellfish Dredging Pushes a Flexible Avian Top Predator out of a Marine Protected Area

PubMed Central

van Gils, Jan A; Piersma, Theunis; Dekinga, Anne; Spaans, Bernard; Kraan, Casper

2006-01-01

There is a widespread concern about the direct and indirect effects of industrial fisheries; this concern is particularly pertinent for so-called “marine protected areas” (MPAs), which should be safeguarded by national and international law. The intertidal flats of the Dutch Wadden Sea are a State Nature Monument and are protected under the Ramsar convention and the European Union's Habitat and Birds Directives. Until 2004, the Dutch government granted permission for ~75% of the intertidal flats to be exploited by mechanical dredgers for edible cockles (Cerastoderma edule). Here we show that dredged areas belonged to the limited area of intertidal flats that were of sufficient quality for red knots (Calidris canutus islandica), a long-distance migrant molluscivore specialist, to feed. Dredging led to relatively lower settlement rates of cockles and also reduced their quality (ratio of flesh to shell). From 1998 to 2002, red knots increased gizzard mass to compensate for a gradual loss in shellfish quality, but this compensation was not sufficient and led to decreases in local survival. Therefore, the gradual destruction of the necessary intertidal resources explains both the loss of red knots from the Dutch Wadden Sea and the decline of the European wintering population. This study shows that MPAs that do not provide adequate protection from fishing may fail in their conservation objectives. PMID:17105350

Marine bivalve geochemistry and shell ultrastructure from modern low pH environments

NASA Astrophysics Data System (ADS)

Hahn, S.; Rodolfo-Metalpa, R.; Griesshaber, E.; Schmahl, W. W.; Buhl, D.; Hall-Spencer, J. M.; Baggini, C.; Fehr, K. T.; Immenhauser, A.

2011-10-01

Bivalve shells can provide excellent archives of past environmental change but have not been used to interpret ocean acidification events. We investigated carbon, oxygen and trace element records from different shell layers in the mussels Mytilus galloprovincialis (from the Mediterranean) and M. edulis (from the Wadden Sea) combined with detailed investigations of the shell ultrastructure. Mussels from the harbour of Ischia (Mediterranean, Italy) were transplanted and grown in water with mean pHT 7.3 and mean pHT 8.1 near CO2 vents on the east coast of the island of Ischia. The shells of transplanted mussels were compared with M. edulis collected at pH ~8.2 from Sylt (German Wadden Sea). Most prominently, the shells recorded the shock of transplantation, both in their shell ultrastructure, textural and geochemical record. Shell calcite, precipitated subsequently under acidified seawater responded to the pH gradient by an in part disturbed ultrastructure. Geochemical data from all test sites show a strong metabolic effect that exceeds the influence of the low-pH environment. These field experiments showed that care is needed when interpreting potential ocean acidification signals because various parameters affect shell chemistry and ultrastructure. Besides metabolic processes, seawater pH, factors such as salinity, water temperature, food availability and population density all affect the biogenic carbonate shell archive.

Future sea-level rise in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Galassi, Gaia; Spada, Giorgio

2014-05-01

-eustatic values (i.e. they do not exceed the global average) and show little (but still significant) variations across the basin associated with the subsidence driven by the meltwater load. For year 2050, TIM calculations predict a sea-level rise of ~10 and ~30 cm for the mid range and the high end scenarios, respectively. Mainly because of the distinct mantle viscosity profiles adopted in ICE-5G(VM2) and KL05, the GIA patterns differ significantly and, in contrast with the TIM fingerprint, are both characterized by strong variations across the Mediterranean Sea, showing maximum values in the bulk of the basin. For the OR component, a significant geographical variation is observed across the Mediterranean sub-basins, corresponding to different Atlantic boundary conditionsAccording to this study, the total future sea-level rise for year 2050 will reach maximum values for the extreme scenario (hig-hend prediction for TIM, KL05 for GIA and EA1B2 for OR) of ˜ 27 cm in average with peak of ˜ 30 cm in the central sub-basins. Our results show that when these three components of future sea-level rise are simultaneously considered, the spatial variability is enhanced because of the neatly distinct geometry of the three fingerprints. References: Carillo, A., Sannino, G., Artale, V., Ruti, P., Calmanti, S., DellAquila, A., 2012, Clim. Dyn. 39 (9-10), 2167-2184; Fleming, K. and Lambeck, K., 2004, Quat. Sci. Rev. 23 (9-10), 1053-1077; Meehl, G.A., and 11 others, 2007, in Climate Change 2007: The Physical Science Basis, Cambridge University Press; Peltier W.R., 2004, Annu. Rev. Earth Pl. Sc., 32, 111-149; Spada, G. and Stocchi, P., 2007, Comput. and Geosci., 33(4), 538-562; Spada G., Bamber J. L., Hurkmans R. T. W. L., 2013, Geophys. Res. Lett., 1-5, 40.

Changes in sea urchins and kelp following a reduction in sea otter density as a result of the Exxon Valdez oil spill

USGS Publications Warehouse

Dean, Thomas A.; Bodkin, James L.; Jewett, Stephen C.; Monson, Daniel H.; Jung, D.

2000-01-01

Interactions between sea otters Enhydra lutris, sea urchins Strongylocentrotus droebachiensis, and kelp were investigated following the reduction in sea otter density in Prince William Sound, Alaska, after the Exxon Valdez oil spill in 1989. At northern Knight Island, a heavily oiled portion of the sound, sea otter abundance was reduced by a minimum of 50% by the oil spill, and from 1995 through 1998 remained at an estimated 66% lower than in 1973. Where sea otter densities were reduced, there were proportionally more large sea urchins. However, except in some widely scattered aggregations, both density and biomass of sea urchins were similar in an area of reduced sea otter density compared with an area where sea otters remained about 10 times more abundant. Furthermore, there was no change in kelp abundance in the area of reduced sea otter density. This is in contrast to greatly increased biomass of sea urchins and greatly reduced kelp density observed following an approximate 90% decline in sea otter abundance in the western Aleutian Islands. The variation in community response to a reduction in sea otters may be related to the magnitude of the reduction and the non-linear response by sea urchins to changes in predator abundance. The number of surviving sea otters may have been high enough to suppress sea urchin populations in Prince William Sound, but not in the Aleutians. Alternatively, differences in response may have been due to differences in the frequency or magnitude of sea urchin recruitment. Densities of small sea urchins were much higher in the Aleutian system even prior to the reduction in sea otters, suggesting a higher rate of recruitment.

Optical monitoring of film pollution on sea surface

NASA Astrophysics Data System (ADS)

Pavlov, Andrey; Konstantinov, Oleg; Shmirko, Konstantin

2017-11-01

The organic films form a brightness contrast on the sea surface. It makes possible to use cheap simple and miniature systems for video monitoring of pollution of coastal marine areas by oil products in the bunkering of ships, emergency situations at oil terminals, gas and oil pipelines, hydrocarbon production platforms on the shelf, etc.1-16 A panoramic video system with a polarization filter on the lens, located at an altitude of 90 m above sea level, can provide effective control of the water area within a radius of 7 kilometers,17-19 and modern photogrammetry technologies allow not only to register the fact of pollution and get a portrait of the offender, but also with a high Spatial and temporal resolution to estimate the dimensions and trace the dynamics of movement and transformation of the film in a geographic coordinate system. Of particular relevance is the optical method of controlling the pollution of the sea surface at the present time with the development of unmanned aerial vehicles that are already equipped with video cameras and require only a minor upgrade of their video system to enhance the contrast of images of organic films.

A primitive protostegid from Australia and early sea turtle evolution

PubMed Central

Kear, Benjamin P; Lee, Michael S.Y

2005-01-01

Sea turtles (Chelonioidea) are a prominent group of modern marine reptiles whose early history is poorly understood. Analysis of exceptionally well preserved fossils of Bouliachelys suteri gen. et sp. nov., a large-bodied basal protostegid (primitive chelonioid) from the Early Cretaceous (Albian) of Australia, indicates that early sea turtles were both larger and more diverse than previously thought. The analysis implies at least five distinct sea turtle lineages existed around 100 million years ago. Currently, the postcranially primitive Ctenochelys and Toxochelys are interpreted as crown-group sea turtles closely related to living cheloniids (e.g. Chelonia); in contrast, the new phylogeny suggests that they are transitional (intermediate stem-taxa) between continental testudines and derived, pelagic chelonioids. PMID:17148342

Contrasting fluvial styles across the mid-Pleistocene climate transition in the northern shelf of the South China Sea: Evidence from 3D seismic data

NASA Astrophysics Data System (ADS)

Zhuo, Haiteng; Wang, Yingmin; Shi, Hesheng; He, Min; Chen, Weitao; Li, Hua; Wang, Ying; Yan, Weiyao

2015-12-01

Multiple successions of buried fluvial channel systems were identified in the Quaternary section of the mid-shelf region of the northern South China Sea, providing a new case study for understanding the interplay between sea level variations and climate change. Using three commercial 3D seismic surveys, accompanied by several 2D lines and a few shallow boreholes, the sequence stratigraphy, seismic geomorphology and stratal architecture of these fluvial channels were carefully investigated. Based on their origin, dimensions, planform geometries and infill architectures, six classes of channel systems, from Class 1 to Class 6, were recognized within five sequences of Quaternary section (SQ1 to SQ5). Three types of fluvial systems among them are incised in their nature, including the trunk incised valleys (Class 1), medium incised valleys (Class 2) and incised tributaries (Class 3). The other three types are unincised, which comprise the trunk channels (Class 4), lateral migrating channels (Class 5) and the stable channels (Class 6). The trunk channels and/or the major valleys that contain braided channels at their base are hypothesized to be a product of deposition from the "big rivers" that have puzzled the sedimentologists for the last decade, providing evidence for the existence of such rivers in the ancient record. Absolute age dates from a few shallow boreholes indicate that the landscapes that were associated with these fluvial systems changed significantly near the completion of the mid-Pleistocene climate transition (MPT), which approximately corresponds to horizon SB2 with an age of ∼0.6 Ma BP. Below SB2, the Early Pleistocene sequence (SQ1) is dominated by a range of different types of unincised fluvial systems. Evidence of incised valleys is absent in SQ1. In contrast, extensive fluvial incision occurred in the successions above horizon SB2 (within SQ2-SQ5). Although recent studies call for increased incision being a product of climate

Observed and simulated changes in Antarctic sea ice and sea level pressure: anthropogenic or natural variability? (Invited)

NASA Astrophysics Data System (ADS)

Hobbs, W. R.

2013-12-01

Statistically-significant changes in Antarctic sea ice cover and the overlying atmosphere have been observed over the last 30 years, but there is an open question of whether these changes are due to multi-decadal natural variability or an anthropogenically-forced response. A number of recent papers have shown that the slight increase in total sea ice cover is within the bounds of internal variability exhibited by coupled climate models in the CMIP5 suite. Modelled changes for the same time period generally show a decrease, but again with a magnitude that is within internal variability. However, in contrast to the Arctic, sea ice tends in the Antarctic are spatially highly heterogeneous, and consideration of the total ice cover may mask important regional signals. In this work, a robust ';fingerprinting' approach is used to show that the observed spatial pattern of sea ice trends is in fact outside simulated natural variability in west Antarctic, and furthermore that the CMIP5 models consistently show decreased ice cover in the Ross and Weddell Seas, sectors which in fact have an observed increase in cover. As a first step towards understanding the disagreement between models and observations, modelled sea level pressure trends are analysed using and optimal fingerprinting approach, to identify whether atmospheric deficiencies in the models can explain the model-observation discrepancy.

Late Pleistocene Sea level on the New Jersey Margin: Implications to eustasy and deep-sea temperature

USGS Publications Warehouse

Wright, J.D.; Sheridan, R.E.; Miller, K.G.; Uptegrove, J.; Cramer, B.S.; Browning, J.V.

2009-01-01

We assembled and dated a late Pleistocene sea-level record based on sequence stratigraphy from the New Jersey margin and compared it with published records from fossil uplifted coral reefs in New Guinea, Barbados, and Araki Island, as well as a composite sea-level estimate from scaling of Red Sea isotopic values. Radiocarbon dates, amino acid racemization data, and superposition constrain the ages of large (20-80??m) sea-level falls from New Jersey that correlate with Marine Isotope Chrons (MIC) 2, 3b, 4, 5b, and 6 (the past 130??kyr). The sea-level records for MIC 1, 2, 4, 5e, and 6 are similar to those reported from New Guinea, Barbados, Araki, and the Red Sea; some differences exist among records for MIC 3. Our record consistently provides the shallowest sea level estimates for MIC3 (??? 25-60??m below present); it agrees most closely with the New Guinea record of Chappell (2002; ??? 35-70??m), but contrasts with deeper estimates provided by Araki (??? 85-95??m) and the Red Sea (50-90??m). Comparison of eustatic estimates with benthic foraminiferal ??18O records shows that the deep sea cooled ??? 2.5????C between MIC 5e and 5d (??? 120-110??ka) and that near freezing conditions persisted until Termination 1a (14-15??ka). Sea-level variations between MIC 5b and 2 (ca. 90-20??ka) follow a well-accepted 0.1???/10??m linear variation predicted by ice-growth effects on foraminiferal ??18O values. The pattern of deep-sea cooling follows a previously established hysteresis loop between two stable modes of operation. Cold, near freezing deep-water conditions characterize most of the past 130??kyr punctuated only by two warm intervals (the Holocene/MIC 1 and MIC 5e). We link these variations to changes in Northern Component Water (NCW). ?? 2009 Elsevier B.V. All rights reserved.

Processing of SeaMARC swath sonar imagery

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

Pratson, L.; Malinverno, A.; Edwards, M.

1990-05-01

Side-scan swath sonar systems have become an increasingly important means of mapping the sea floor. Two such systems are the deep-towed, high-resolution SeaMARC I sonar, which has a variable swath width of up to 5 km, and the shallow-towed, lower-resolution SeaMARC II sonar, which has a swath width of 10 km. The sea-floor imagery of acoustic backscatter output by the SeaMARC sonars is analogous to aerial photographs and airborne side-looking radar images of continental topography. Geologic interpretation of the sea-floor imagery is greatly facilitated by image processing. Image processing of the digital backscatter data involves removal of noise by medianmore » filtering, spatial filtering to remove sonar scans of anomalous intensity, across-track corrections to remove beam patterns caused by nonuniform response of the sonar transducers to changes in incident angle, and contrast enhancement by histogram equalization to maximize the available dynamic range. Correct geologic interpretation requires submarine structural fabrics to be displayed in their proper locations and orientations. Geographic projection of sea-floor imagery is achieved by merging the enhanced imagery with the sonar vehicle navigation and correcting for vehicle attitude. Co-registration of bathymetry with sonar imagery introduces sea-floor relief and permits the imagery to be displayed in three-dimensional perspectives, furthering the ability of the marine geologist to infer the processes shaping formerly hidden subsea terrains.« less

Late Pliocene Sea Surface Temperature contrast in the Benguela upwelling as recorded by foraminiferal Mg/Ca and alkenones

NASA Astrophysics Data System (ADS)

Leduc, G.; Garbe-Schoenberg, C.; Regenberg, M.; Schneider, R. R.

2011-12-01

Alkenone-based sea surface temperature (SST) in the Benguela region reveal quite warm and stable conditions between ~3.0 and 2.0 Ma, coinciding with a period of very high diatom production as revealed by mass accumulation rates (MAR) of biogenic opal (Marlow et al., 2000, Science; Etourneau et al., 2009, Geology). Such a pattern is difficult to believe with the general perception that high diatom productivity results from strong coastal upwelling associated with pronounced Surface Ocean cooling. Therefore we assessed whether different paleothermometers from the same sedimentary archive (i.e. ODP site 1082) provide different results for the Namibian upwelling system by performing a comparison between alkenone-derived temperatures and those from the planktonic foraminifera Globigerinoides bulloides, a species known to proliferate in upwelling regions. We used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for multiple in situ determination of Mg/Ca in single tests of G. bulloides. These measurements allow monitoring of contaminant phases linked to Mg-rich clays (monitored by Al/Ca) and Mn-rich foraminiferal tests, which contain substantial high Mg (monitored by Mn/Ca) (Pena et al., 2005, G-cubed). Moreover, using LA-ICP-MS measurements for Mg/Ca ratios on single specimens allows estimating the range of seasonal or vertical temperature variability by considering the intra-sample variance in the SST estimated from different specimens and/or different chambers within the same specimen. When compared to the Pliocene alkenone SST record, the Mg/Ca-ratios imply SSTs colder by ~10°C. A similar contrast in SST estimates between these two proxies was reported for the last 20 ka in the same region (Farmer et al., 2005, Paleoceanography). Such discrepancy can be reconciled by assuming that the two SST proxies are either strongly skewed towards warm (non-upwelling) and cold (upwelling) conditions for alkenones and Mg/Ca SST, respectively, or by the

Influences of terrestrial inorganic carbon on carbonate system in China Seas and the implication for China Seas' vulnerabilities to potentially negative effects of ocean acidification

NASA Astrophysics Data System (ADS)

Guo, X.; Zhai, W. D.; Guo, L. G.; Jiang, Z. P.; Qi, D.; Xu, Y.; Huang, X.

2017-12-01

We investigated sea surface carbonate system and ancillary parameters in the northern South China Sea (SCS), East China Sea (ECS), Yellow Sea, and Bohai Sea during a single cruise from late April to June 2011. In this transitional season between the dry/cold and wet/warm seasons, we observed ubiquitous terrestrial inorganic carbon signals in the Yellow Sea and Bohai Sea, as indicated by excess total alkalinity (TAlk) from 150 to 450 μmol kg-1 and excess Ca concentrations from 100 to 470 μmol kg-1, associated with relatively high DIC/TAlk ratios from 0.88 to 0.92. In contrast, these terrestrial inorganic carbon signals were limited to nearshore areas in the southern ECS and northern SCS. These results suggested that the Yellow Sea and Bohai Sea were dominated by terrestrial inputs all over the year, while the terrestrial signals in the southern ECS and northern SCS were highly diminished in dry seasons through water mixing with open ocean waters (likely introduced by Kuroshio). This study also showed that the terrestrial inorganic carbon inputs had diminished carbonate ion concentrations and CaCO3 saturation states in the Yellow Sea and Bohai Sea. This may contribute to recent findings that the North Yellow Sea represents one of the systems in the China seas most vulnerable to the potentially negative effects of ocean acidification.

Improving the spatial and temporal resolution with quantification of uncertainty and errors in earth observation data sets using Data Interpolating Empirical Orthogonal Functions methodology

NASA Astrophysics Data System (ADS)

El Serafy, Ghada; Gaytan Aguilar, Sandra; Ziemba, Alexander

2016-04-01

There is an increasing use of process-based models in the investigation of ecological systems and scenario predictions. The accuracy and quality of these models are improved when run with high spatial and temporal resolution data sets. However, ecological data can often be difficult to collect which manifests itself through irregularities in the spatial and temporal domain of these data sets. Through the use of Data INterpolating Empirical Orthogonal Functions(DINEOF) methodology, earth observation products can be improved to have full spatial coverage within the desired domain as well as increased temporal resolution to daily and weekly time step, those frequently required by process-based models[1]. The DINEOF methodology results in a degree of error being affixed to the refined data product. In order to determine the degree of error introduced through this process, the suspended particulate matter and chlorophyll-a data from MERIS is used with DINEOF to produce high resolution products for the Wadden Sea. These new data sets are then compared with in-situ and other data sources to determine the error. Also, artificial cloud cover scenarios are conducted in order to substantiate the findings from MERIS data experiments. Secondly, the accuracy of DINEOF is explored to evaluate the variance of the methodology. The degree of accuracy is combined with the overall error produced by the methodology and reported in an assessment of the quality of DINEOF when applied to resolution refinement of chlorophyll-a and suspended particulate matter in the Wadden Sea. References [1] Sirjacobs, D.; Alvera-Azcárate, A.; Barth, A.; Lacroix, G.; Park, Y.; Nechad, B.; Ruddick, K.G.; Beckers, J.-M. (2011). Cloud filling of ocean colour and sea surface temperature remote sensing products over the Southern North Sea by the Data Interpolating Empirical Orthogonal Functions methodology. J. Sea Res. 65(1): 114-130. Dx.doi.org/10.1016/j.seares.2010.08.002

Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications

NASA Astrophysics Data System (ADS)

DeWeaver, Eric T.; Bitz, Cecilia M.; Tremblay, L.-Bruno

This volume addresses the rapid decline of Arctic sea ice, placing recent sea ice decline in the context of past observations, climate model simulations and projections, and simple models of the climate sensitivity of sea ice. Highlights of the work presented here include • An appraisal of the role played by wind forcing in driving the decline; • A reconstruction of Arctic sea ice conditions prior to human observations, based on proxy data from sediments; • A modeling approach for assessing the impact of sea ice decline on polar bears, used as input to the U.S. Fish and Wildlife Service's decision to list the polar bear as a threatened species under the Endangered Species Act; • Contrasting studies on the existence of a "tipping point," beyond which Arctic sea ice decline will become (or has already become) irreversible, including an examination of the role of the small ice cap instability in global warming simulations; • A significant summertime atmospheric response to sea ice reduction in an atmospheric general circulation model, suggesting a positive feedback and the potential for short-term climate prediction. The book will be of interest to researchers attempting to understand the recent behavior of Arctic sea ice, model projections of future sea ice loss, and the consequences of sea ice loss for the natural and human systems of the Arctic.

Satellite Observations of Antarctic Sea Ice Thickness and Volume

NASA Technical Reports Server (NTRS)

Kurtz, Nathan; Markus, Thorsten

2012-01-01

We utilize satellite laser altimetry data from ICESat combined with passive microwave measurements to analyze basin-wide changes in Antarctic sea ice thickness and volume over a 5 year period from 2003-2008. Sea ice thickness exhibits a small negative trend while area increases in the summer and fall balanced losses in thickness leading to small overall volume changes. Using a five year time-series, we show that only small ice thickness changes of less than -0.03 m/yr and volume changes of -266 cu km/yr and 160 cu km/yr occurred for the spring and summer periods, respectively. The calculated thickness and volume trends are small compared to the observational time period and interannual variability which masks the determination of long-term trend or cyclical variability in the sea ice cover. These results are in stark contrast to the much greater observed losses in Arctic sea ice volume and illustrate the different hemispheric changes of the polar sea ice covers in recent years.

Synoptic evaluation of carbon cycling in Beaufort Sea during summer: contrasting river inputs, ecosystem metabolism and air-sea CO2 fluxes

NASA Astrophysics Data System (ADS)

Forest, A.; Coupel, P.; Else, B.; Nahavandian, S.; Lansard, B.; Raimbault, P.; Papakyriakou, T.; Gratton, Y.; Fortier, L.; Tremblay, J.-É.; Babin, M.

2013-10-01

The accelerated decline in Arctic sea ice combined with an ongoing trend toward a more dynamic atmosphere is modifying carbon cycling in the Arctic Ocean. A critical issue is to understand how net community production (NCP; the balance between gross primary production and community respiration) responds to changes and modulates air-sea CO2 fluxes. Using data collected as part of the ArcticNet-Malina 2009 expedition in southeastern Beaufort Sea (Arctic Ocean), we synthesize information on sea ice, wind, river, water column properties, metabolism of the planktonic food web, organic carbon fluxes and pools, as well as air-sea CO2 exchange, with the aim of identifying indices of ecosystem response to environmental changes. Data were analyzed to develop a non-steady-state carbon budget and an assessment of NCP against air-sea CO2 fluxes. The mean atmospheric forcing was a mild upwelling-favorable wind (~5 km h-1) blowing from the N-E and a decaying ice cover (<80% concentration) was observed beyond the shelf, the latter being fully exposed to the atmosphere. We detected some areas where the surface mixed layer was net autotrophic owing to high rates of primary production (PP), but the ecosystem was overall net heterotrophic. The region acted nonetheless as a sink for atmospheric CO2 with a mean uptake rate of -2.0 ± 3.3 mmol C m-2d-1. We attribute this discrepancy to: (1) elevated PP rates (>600 mg C m-2d-1) over the shelf prior to our survey, (2) freshwater dilution by river runoff and ice melt, and (3) the presence of cold surface waters offshore. Only the Mackenzie River delta and localized shelf areas directly affected by upwelling were identified as substantial sources of CO2 to the atmosphere (>10mmol C m-2d-1). Although generally <100 mg C m-2d-1, daily PP rates cumulated to a total PP of ~437.6 × 103 t C, which was roughly twice higher than the organic carbon delivery by river inputs (~241.2 × 103 t C). Subsurface PP represented 37.4% of total PP for the

On the relationship between sea level and Spartina alterniflora production

USGS Publications Warehouse

Kirwan, Matthew L.; Christian, Robert R.; Blum, Linda K.; Brinson, Mark M.

2012-01-01

A positive relationship between interannual sea level and plant growth is thought to stabilize many coastal landforms responding to accelerating rates of sea level rise. Numerical models of delta growth, tidal channel network evolution, and ecosystem resilience incorporate a hump-shaped relationship between inundation and plant primary production, where vegetation growth increases with sea level up to an optimum water depth or inundation frequency. In contrast, we use decade-long measurements of Spartina alterniflora biomass in seven coastal Virginia (USA) marshes to demonstrate that interannual sea level is rarely a primary determinant of vegetation growth. Although we find tepid support for a hump-shaped relationship between aboveground production and inundation when marshes of different elevation are considered, our results suggest that marshes high in the intertidal zone and low in relief are unresponsive to sea level fluctuations. We suggest existing models are unable to capture the behavior of wetlands in these portions of the landscape, and may underestimate their vulnerability to sea level rise because sea level rise will not be accompanied by enhanced plant growth and resultant sediment accumulation.

Deep-sea biodiversity in the Mediterranean Sea: the known, the unknown, and the unknowable.

PubMed

Danovaro, Roberto; Company, Joan Batista; Corinaldesi, Cinzia; D'Onghia, Gianfranco; Galil, Bella; Gambi, Cristina; Gooday, Andrew J; Lampadariou, Nikolaos; Luna, Gian Marco; Morigi, Caterina; Olu, Karine; Polymenakou, Paraskevi; Ramirez-Llodra, Eva; Sabbatini, Anna; Sardà, Francesc; Sibuet, Myriam; Tselepides, Anastasios

2010-08-02

Deep-sea ecosystems represent the largest biome of the global biosphere, but knowledge of their biodiversity is still scant. The Mediterranean basin has been proposed as a hot spot of terrestrial and coastal marine biodiversity but has been supposed to be impoverished of deep-sea species richness. We summarized all available information on benthic biodiversity (Prokaryotes, Foraminifera, Meiofauna, Macrofauna, and Megafauna) in different deep-sea ecosystems of the Mediterranean Sea (200 to more than 4,000 m depth), including open slopes, deep basins, canyons, cold seeps, seamounts, deep-water corals and deep-hypersaline anoxic basins and analyzed overall longitudinal and bathymetric patterns. We show that in contrast to what was expected from the sharp decrease in organic carbon fluxes and reduced faunal abundance, the deep-sea biodiversity of both the eastern and the western basins of the Mediterranean Sea is similarly high. All of the biodiversity components, except Bacteria and Archaea, displayed a decreasing pattern with increasing water depth, but to a different extent for each component. Unlike patterns observed for faunal abundance, highest negative values of the slopes of the biodiversity patterns were observed for Meiofauna, followed by Macrofauna and Megafauna. Comparison of the biodiversity associated with open slopes, deep basins, canyons, and deep-water corals showed that the deep basins were the least diverse. Rarefaction curves allowed us to estimate the expected number of species for each benthic component in different bathymetric ranges. A large fraction of exclusive species was associated with each specific habitat or ecosystem. Thus, each deep-sea ecosystem contributes significantly to overall biodiversity. From theoretical extrapolations we estimate that the overall deep-sea Mediterranean biodiversity (excluding prokaryotes) reaches approximately 2805 species of which about 66% is still undiscovered. Among the biotic components investigated

Deep-Sea Biodiversity in the Mediterranean Sea: The Known, the Unknown, and the Unknowable

PubMed Central

Danovaro, Roberto; Company, Joan Batista; Corinaldesi, Cinzia; D'Onghia, Gianfranco; Galil, Bella; Gambi, Cristina; Gooday, Andrew J.; Lampadariou, Nikolaos; Luna, Gian Marco; Morigi, Caterina; Olu, Karine; Polymenakou, Paraskevi; Ramirez-Llodra, Eva; Sabbatini, Anna; Sardà, Francesc; Sibuet, Myriam; Tselepides, Anastasios

2010-01-01

Deep-sea ecosystems represent the largest biome of the global biosphere, but knowledge of their biodiversity is still scant. The Mediterranean basin has been proposed as a hot spot of terrestrial and coastal marine biodiversity but has been supposed to be impoverished of deep-sea species richness. We summarized all available information on benthic biodiversity (Prokaryotes, Foraminifera, Meiofauna, Macrofauna, and Megafauna) in different deep-sea ecosystems of the Mediterranean Sea (200 to more than 4,000 m depth), including open slopes, deep basins, canyons, cold seeps, seamounts, deep-water corals and deep-hypersaline anoxic basins and analyzed overall longitudinal and bathymetric patterns. We show that in contrast to what was expected from the sharp decrease in organic carbon fluxes and reduced faunal abundance, the deep-sea biodiversity of both the eastern and the western basins of the Mediterranean Sea is similarly high. All of the biodiversity components, except Bacteria and Archaea, displayed a decreasing pattern with increasing water depth, but to a different extent for each component. Unlike patterns observed for faunal abundance, highest negative values of the slopes of the biodiversity patterns were observed for Meiofauna, followed by Macrofauna and Megafauna. Comparison of the biodiversity associated with open slopes, deep basins, canyons, and deep-water corals showed that the deep basins were the least diverse. Rarefaction curves allowed us to estimate the expected number of species for each benthic component in different bathymetric ranges. A large fraction of exclusive species was associated with each specific habitat or ecosystem. Thus, each deep-sea ecosystem contributes significantly to overall biodiversity. From theoretical extrapolations we estimate that the overall deep-sea Mediterranean biodiversity (excluding prokaryotes) reaches approximately 2805 species of which about 66% is still undiscovered. Among the biotic components investigated

Contrasted turbulence intensities in the Indonesian Throughflow: a challenge for parameterizing energy dissipation rate

NASA Astrophysics Data System (ADS)

Bouruet-Aubertot, Pascale; Cuypers, Yannis; Ferron, Bruno; Dausse, Denis; Ménage, Olivier; Atmadipoera, Agus; Jaya, Indra

2018-05-01

Microstructure measurements were performed along two sections through the Halmahera Sea and the Ombai Strait and at a station in the deep Banda Sea. Contrasting dissipation rates (𝜖) and vertical eddy diffusivities (K z ) were obtained with depth-averaged ranges of ˜ [9 × 10^{-10}-10^{-5}] W kg- 1 and of ˜ [1 × 10^{-5}-2 × 10^{-3}] m2 s- 1, respectively. Similarly, turbulence intensity, I={ɛ }/(ν N2) with ν the kinematic viscosity and N the buoyancy frequency, was found to vary seven orders of magnitude with values up to 107. These large ranges of variations were correlated with the internal tide energy level, which highlights the contrast between regions close and far from internal tide generations. Finescale parameterizations of 𝜖 induced by the breaking of weakly nonlinear internal waves were only relevant in regions located far from any generation area ("far field"), at the deep Banda Sea station. Closer to generation areas, at the "intermediate field" station of the Halmahera Sea, a modified formulation of MacKinnon and Gregg (2005) was validated for moderately turbulent regimes with 100 < I < 1000. Near generation areas marked by strong turbulent regimes such as "near field" stations within strait and passages, 𝜖 is most adequately inferred from horizontal velocities provided that part of the inertial subrange is resolved, according to Kolmogorov scaling.

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.

Identity and abundance of active sulfate-reducing bacteria in deep tidal flat sediments determined by directed cultivation and CARD-FISH analysis.

PubMed

Gittel, Antje; Mussmann, Marc; Sass, Henrik; Cypionka, Heribert; Könneke, Martin

2008-10-01

The identity and abundance of potentially active sulfate-reducing bacteria (SRB) in several metre deep sediments of a tidal sand flat in the German Wadden Sea were assessed by directed cultivation and cultivation-independent CARD-FISH analysis (catalysed reporter deposition fluorescence in situ hybridization). Presumably abundant SRB from different sediment layers between 0.5 and 4 m depth were selectively enriched in up to million-fold diluted cultures supplemented with lactate, acetate or hydrogen. Partial 16S rRNA gene sequences obtained from highest dilution steps showing sulfide formation indicated growth of deltaproteobacterial SRB belonging to the Desulfobulbaceae and the Desulfobacteraceae as well as of members of the Firmicutes. Subsequent isolation resulted in 10 novel phylotypes of both litho- and organotrophic sulfate-reducing Deltaproteobacteria. Molecular pre-screening identified six isolates as members of the Desulfobulbaceae, sharing highest identities with either candidatus 'Desulfobacterium corrodens' (95-97%) or Desulfobacterium catecholicum (98%), and four isolates as members of Desulfobacteraceae, being related to either Desulfobacter psychrotolerans (98%) or Desulfobacula phenolica (95-97%). Relatives of D. phenolica were exlusively isolated from 50 and 100 cm deep sediments with 10 and 2 mM of pore water sulfate respectively. In contrast, relatives of D. corrodens, D. psychrotolerans and D. catecholicum were also obtained from layers deeper than 100 cm and with less than 2 mM sulfate. The high in situ abundance of members of both families in sediment layers beneath 50 cm could be confirmed via CARD-FISH analysis performed with a set of six SRB-specific oligonucleotide probes. Moreover, SRB represented a numerically significant fraction of the microbial community throughout the sediment (up to 7%) and reached even higher cell numbers in deep, sulfate-poor layers than in the sulfate-rich surface sediment. This relatively large community size of

Echoes from the past: Regional variations in recovery within a harbour seal population

PubMed Central

Reijnders, Peter J. H.; Cremer, Jenny; Meesters, Erik; Kirkwood, Roger; Jensen, Lasse Fast; Jeβ, Armin; Galatius, Anders; Teilmann, Jonas; Aarts, Geert

2018-01-01

Terrestrial and marine wildlife populations have been severely reduced by hunting, fishing and habitat destruction, especially in the last centuries. Although management regulations have led to the recovery of some populations, the underlying processes are not always well understood. This study uses a 40-year time series of counts of harbour seals (Phoca vitulina) in the Wadden Sea to study these processes, and demonstrates the influence of historical regional differences in management regimes on the recovery of this population. While the Wadden Sea is considered one ecologically coupled zone, with a distinct harbour seal population, the area is divided into four geo-political regions i.e. the Netherlands, Lower Saxony including Hamburg, Schleswig-Holstein and Denmark. Gradually, seal hunting was banned between 1962 and 1977 in the different regions. Counts of moulting harbour seals and pup counts, obtained during aerial surveys between 1974 and 2014, show a population growth from approximately 4500 to 39,000 individuals. Population growth models were developed to assess if population growth differed between regions, taking into account two Phocine Distemper Virus (PDV) epizootics, in 1988 and 2002 which seriously affected the population. After a slow start prior to the first epizootic, the overall population grew exponentially at rates close to assumed maximum rates of increase in a harbour seal population. Recently, growth slowed down, potentially indicative of approaching carrying capacity. Regional differences in growth rates were demonstrated, with the highest recovery in Netherlands after the first PDV epizootic (i.e. 17.9%), suggesting that growth was fuelled by migration from the other regions, where growth remained at or below the intrinsic growth rate (13%). The seals’ distribution changed, and although the proportion of seals counted in the German regions declined, they remained by far the most important pupping region, with approximately 70% of all

Echoes from the past: Regional variations in recovery within a harbour seal population.

PubMed

Brasseur, Sophie M J M; Reijnders, Peter J H; Cremer, Jenny; Meesters, Erik; Kirkwood, Roger; Jensen, Lasse Fast; Jeβ, Armin; Galatius, Anders; Teilmann, Jonas; Aarts, Geert

2018-01-01

Terrestrial and marine wildlife populations have been severely reduced by hunting, fishing and habitat destruction, especially in the last centuries. Although management regulations have led to the recovery of some populations, the underlying processes are not always well understood. This study uses a 40-year time series of counts of harbour seals (Phoca vitulina) in the Wadden Sea to study these processes, and demonstrates the influence of historical regional differences in management regimes on the recovery of this population. While the Wadden Sea is considered one ecologically coupled zone, with a distinct harbour seal population, the area is divided into four geo-political regions i.e. the Netherlands, Lower Saxony including Hamburg, Schleswig-Holstein and Denmark. Gradually, seal hunting was banned between 1962 and 1977 in the different regions. Counts of moulting harbour seals and pup counts, obtained during aerial surveys between 1974 and 2014, show a population growth from approximately 4500 to 39,000 individuals. Population growth models were developed to assess if population growth differed between regions, taking into account two Phocine Distemper Virus (PDV) epizootics, in 1988 and 2002 which seriously affected the population. After a slow start prior to the first epizootic, the overall population grew exponentially at rates close to assumed maximum rates of increase in a harbour seal population. Recently, growth slowed down, potentially indicative of approaching carrying capacity. Regional differences in growth rates were demonstrated, with the highest recovery in Netherlands after the first PDV epizootic (i.e. 17.9%), suggesting that growth was fuelled by migration from the other regions, where growth remained at or below the intrinsic growth rate (13%). The seals' distribution changed, and although the proportion of seals counted in the German regions declined, they remained by far the most important pupping region, with approximately 70% of all pups

Contrasted demographic responses facing future climate change in Southern Ocean seabirds.

PubMed

Barbraud, Christophe; Rivalan, Philippe; Inchausti, Pablo; Nevoux, Marie; Rolland, Virginie; Weimerskirch, Henri

2011-01-01

1. Recent climate change has affected a wide range of species, but predicting population responses to projected climate change using population dynamics theory and models remains challenging, and very few attempts have been made. The Southern Ocean sea surface temperature and sea ice extent are projected to warm and shrink as concentrations of atmospheric greenhouse gases increase, and several top predator species are affected by fluctuations in these oceanographic variables. 2. We compared and projected the population responses of three seabird species living in sub-tropical, sub-Antarctic and Antarctic biomes to predicted climate change over the next 50 years. Using stochastic population models we combined long-term demographic datasets and projections of sea surface temperature and sea ice extent for three different IPCC emission scenarios (from most to least severe: A1B, A2, B1) from general circulation models of Earth's climate. 3. We found that climate mostly affected the probability to breed successfully, and in one case adult survival. Interestingly, frequent nonlinear relationships in demographic responses to climate were detected. Models forced by future predicted climatic change provided contrasted population responses depending on the species considered. The northernmost distributed species was predicted to be little affected by a future warming of the Southern Ocean, whereas steep declines were projected for the more southerly distributed species due to sea surface temperature warming and decrease in sea ice extent. For the most southerly distributed species, the A1B and B1 emission scenarios were respectively the most and less damaging. For the two other species, population responses were similar for all emission scenarios. 4. This is among the first attempts to study the demographic responses for several populations with contrasted environmental conditions, which illustrates that investigating the effects of climate change on core population dynamics

High resolution satellite observations of mesoscale oceanography in the Tasman Sea, 1978 - 1979

NASA Technical Reports Server (NTRS)

Nilsson, C. S.; Andrews, J. C.; Hornibrook, M.; Latham, A. R.; Speechley, G. C.; Scully-Power, P. (Principal Investigator)

1982-01-01

Of the Nearly 1000 standard infrared photographic images received, 273 images were on computer compatible tape. It proved necessary to digitally enhance the scene contrast to cover only a select few degrees K over the photographic grey scale appropriate to the scene-specific range of sea surface temperature (SST). Some 178 images were so enhanced. Comparison with sea truth show that SST, as seen by satellite, provides a good guide to the ocean currents and eddies off East Australia, both in summer and winter. This is in contrast, particularly in summer, to SST mapped by surface survey, which usually lacks the necessary spatial resolution.

Optical properties of melting first-year Arctic sea ice

NASA Astrophysics Data System (ADS)

Light, Bonnie; Perovich, Donald K.; Webster, Melinda A.; Polashenski, Christopher; Dadic, Ruzica

2015-11-01

The albedo and transmittance of melting, first-year Arctic sea ice were measured during two cruises of the Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment (ICESCAPE) project during the summers of 2010 and 2011. Spectral measurements were made for both bare and ponded ice types at a total of 19 ice stations in the Chukchi and Beaufort Seas. These data, along with irradiance profiles taken within boreholes, laboratory measurements of the optical properties of core samples, ice physical property observations, and radiative transfer model simulations are employed to describe representative optical properties for melting first-year Arctic sea ice. Ponded ice was found to transmit roughly 4.4 times more total energy into the ocean, relative to nearby bare ice. The ubiquitous surface-scattering layer and drained layer present on bare, melting sea ice are responsible for its relatively high albedo and relatively low transmittance. Light transmittance through ponded ice depends on the physical thickness of the ice and the magnitude of the scattering coefficient in the ice interior. Bare ice reflects nearly three-quarters of the incident sunlight, enhancing its resiliency to absorption by solar insolation. In contrast, ponded ice absorbs or transmits to the ocean more than three-quarters of the incident sunlight. Characterization of the heat balance of a summertime ice cover is largely dictated by its pond coverage, and light transmittance through ponded ice shows strong contrast between first-year and multiyear Arctic ice covers.

Extreme ecological response of a seabird community to unprecedented sea ice cover.

PubMed

Barbraud, Christophe; Delord, Karine; Weimerskirch, Henri

2015-05-01

Climate change has been predicted to reduce Antarctic sea ice but, instead, sea ice surrounding Antarctica has expanded over the past 30 years, albeit with contrasted regional changes. Here we report a recent extreme event in sea ice conditions in East Antarctica and investigate its consequences on a seabird community. In early 2014, the Dumont d'Urville Sea experienced the highest magnitude sea ice cover (76.8%) event on record (1982-2013: range 11.3-65.3%; mean±95% confidence interval: 27.7% (23.1-32.2%)). Catastrophic effects were detected in the breeding output of all sympatric seabird species, with a total failure for two species. These results provide a new view crucial to predictive models of species abundance and distribution as to how extreme sea ice events might impact an entire community of top predators in polar marine ecosystems in a context of expanding sea ice in eastern Antarctica.

Phase contrast and DIC instrumentation and applications in cell, developmental, and marine biology

NASA Astrophysics Data System (ADS)

Gundlach, Heinz

1994-05-01

Nomarski's differential interference contrast (DIC) microscopy is discussed in comparison to Zernike's phase contrast (PhC) microscopy. The possibilities and limits of both are demonstrated by various applications. The high contrast and the use of the full numerical aperture of the DIC optics makes it possible to obtain a series of 'optical sections' through rather thick living specimens (e.g. head of water flea, salivary gland of Drosophila, Xenopus nucleolus, sea urchen egg, mouse embryo). PhC and DIC optics are today available for high resolution light microscopy until N.A. 1.4 Oil as well as for long working distance (LWD) optics, mainly combined with inverted biological microscopes.

Antarctic Sea Ice Variability and Trends, 1979-2010

NASA Technical Reports Server (NTRS)

Parkinson, C. L.; Cavalieri, D. J.

2012-01-01

In sharp contrast to the decreasing sea ice coverage of the Arctic, in the Antarctic the sea ice cover has, on average, expanded since the late 1970s. More specifically, satellite passive-microwave data for the period November 1978 - December 2010 reveal an overall positive trend in ice extents of 17,100 +/- 2,300 square km/yr. Much of the increase, at 13,700 +/- 1,500 square km/yr, has occurred in the region of the Ross Sea, with lesser contributions from the Weddell Sea and Indian Ocean. One region, that of the Bellingshausen/Amundsen Seas, has, like the Arctic, instead experienced significant sea ice decreases, with an overall ice extent trend of -8,200 +/- 1,200 square km/yr. When examined through the annual cycle over the 32-year period 1979-2010, the Southern Hemisphere sea ice cover as a whole experienced positive ice extent trends in every month, ranging in magnitude from a low of 9,100 +/- 6,300 square km/yr in February to a high of 24,700 +/- 10,000 square km/yr in May. The Ross Sea and Indian Ocean also had positive trends in each month, while the Bellingshausen/Amundsen Seas had negative trends in each month, and the Weddell Sea and Western Pacific Ocean had a mixture of positive and negative trends. Comparing ice-area results to ice-extent results, in each case the ice-area trend has the same sign as the ice-extent trend, but differences in the magnitudes of the two trends identify regions with overall increasing ice concentrations and others with overall decreasing ice concentrations. The strong pattern of decreasing ice coverage in the Bellingshausen/Amundsen Seas region and increasing ice coverage in the Ross Sea region is suggestive of changes in atmospheric circulation. This is a key topic for future research.

Sun-stirred Kraken Mare: Circulation in Titan's seas induced by solar heating and methane precipitation

NASA Astrophysics Data System (ADS)

Tokano, T.; Lorenz, R. D.

2015-10-01

Density-driven circulation in Titan's seas forced by solar heating and methane evaporation/precipitation is simulated by an ocean circulation model. If the sea is transparent to sunlight, solar heating can induce anti-clockwise gyres near the sea surface and clockwise gyres near the sea bottom. The gyres are in geostrophic balance between the radially symmetric pressure gradient force and Coriolis force. If instead the sea is turbid and most sunlight is absorbed near the sea surface, the sea gets stratified in warm seasons and the circulation remains weak. Strong summer precipitation at high latitudes causes compositional stratification and increase of the nearsurface methane mole fraction towards the north pole. The resultant latitudinal density contrast drives a meridional overturning with equatorward currents near the sea surface and poleward currents near the sea bottom. Weak precipitation induces gyres rather than meridional overturning.

Challenging Oil Bioremediation at Deep-Sea Hydrostatic Pressure

PubMed Central

Scoma, Alberto; Yakimov, Michail M.; Boon, Nico

2016-01-01

The Deepwater Horizon accident has brought oil contamination of deep-sea environments to worldwide attention. The risk for new deep-sea spills is not expected to decrease in the future, as political pressure mounts to access deep-water fossil reserves, and poorly tested technologies are used to access oil. This also applies to the response to oil-contamination events, with bioremediation the only (bio)technology presently available to combat deep-sea spills. Many questions about the fate of petroleum-hydrocarbons within deep-sea environments remain unanswered, as well as the main constraints limiting bioremediation under increased hydrostatic pressures and low temperatures. The microbial pathways fueling oil bioassimilation are unclear, and the mild upregulation observed for beta-oxidation-related genes in both water and sediments contrasts with the high amount of alkanes present in the spilled oil. The fate of solid alkanes (tar), hydrocarbon degradation rates and the reason why the most predominant hydrocarbonoclastic genera were not enriched at deep-sea despite being present at hydrocarbon seeps at the Gulf of Mexico have been largely overlooked. This mini-review aims at highlighting the missing information in the field, proposing a holistic approach where in situ and ex situ studies are integrated to reveal the principal mechanisms accounting for deep-sea oil bioremediation. PMID:27536290

The Pursuit of Economic Strength Has Stabilizing Effects in the South China Sea

DTIC Science & Technology

2016-09-01

but opposing schools of thought regarding the security environment and potential for armed conflict between states with competing territory and...South China Sea and the corresponding reactions by Southeast Asian nations, particularly Vietnam and the Philippines .3 By contrast, the liberal school ...whether Vietnam and the Philippines are trending toward conflict or cooperation in managing their competing South China Sea territory and resource

Potential impacts of climate change on the primary production of regional seas: A comparative analysis of five European seas

NASA Astrophysics Data System (ADS)

Holt, Jason; Schrum, Corinna; Cannaby, Heather; Daewel, Ute; Allen, Icarus; Artioli, Yuri; Bopp, Laurent; Butenschon, Momme; Fach, Bettina A.; Harle, James; Pushpadas, Dhanya; Salihoglu, Baris; Wakelin, Sarah

2016-01-01

Regional seas are potentially highly vulnerable to climate change, yet are the most directly societally important regions of the marine environment. The combination of widely varying conditions of mixing, forcing, geography (coastline and bathymetry) and exposure to the open-ocean makes these seas subject to a wide range of physical processes that mediates how large scale climate change impacts on these seas' ecosystems. In this paper we explore the response of five regional sea areas to potential future climate change, acting via atmospheric, oceanic and terrestrial vectors. These include the Barents Sea, Black Sea, Baltic Sea, North Sea, Celtic Seas, and are contrasted with a region of the Northeast Atlantic. Our aim is to elucidate the controlling dynamical processes and how these vary between and within these seas. We focus on primary production and consider the potential climatic impacts on: long term changes in elemental budgets, seasonal and mesoscale processes that control phytoplankton's exposure to light and nutrients, and briefly direct temperature response. We draw examples from the MEECE FP7 project and five regional model systems each using a common global Earth System Model as forcing. We consider a common analysis approach, and additional sensitivity experiments. Comparing projections for the end of the 21st century with mean present day conditions, these simulations generally show an increase in seasonal and permanent stratification (where present). However, the first order (low- and mid-latitude) effect in the open ocean projections of increased permanent stratification leading to reduced nutrient levels, and so to reduced primary production, is largely absent, except in the NE Atlantic. Even in the two highly stratified, deep water seas we consider (Black and Baltic Seas) the increase in stratification is not seen as a first order control on primary production. Instead, results show a highly heterogeneous picture of positive and negative change

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

Synoptic evaluation of carbon cycling in the Beaufort Sea during summer: contrasting river inputs, ecosystem metabolism and air-sea CO2 fluxes

NASA Astrophysics Data System (ADS)

Forest, A.; Coupel, P.; Else, B.; Nahavandian, S.; Lansard, B.; Raimbault, P.; Papakyriakou, T.; Gratton, Y.; Fortier, L.; Tremblay, J.-É.; Babin, M.

2014-05-01

The accelerated decline in Arctic sea ice and an ongoing trend toward more energetic atmospheric and oceanic forcings are modifying carbon cycling in the Arctic Ocean. A critical issue is to understand how net community production (NCP; the balance between gross primary production and community respiration) responds to changes and modulates air-sea CO2 fluxes. Using data collected as part of the ArcticNet-Malina 2009 expedition in the southeastern Beaufort Sea (Arctic Ocean), we synthesize information on sea ice, wind, river, water column properties, metabolism of the planktonic food web, organic carbon fluxes and pools, as well as air-sea CO2 exchange, with the aim of documenting the ecosystem response to environmental changes. Data were analyzed to develop a non-steady-state carbon budget and an assessment of NCP against air-sea CO2 fluxes. During the field campaign, the mean wind field was a mild upwelling-favorable wind (~ 5 km h-1) from the NE. A decaying ice cover (< 80% concentration) was observed beyond the shelf, the latter being fully exposed to the atmosphere. We detected some areas where the surface mixed layer was net autotrophic owing to high rates of primary production (PP), but the ecosystem was overall net heterotrophic. The region acted nonetheless as a sink for atmospheric CO2, with an uptake rate of -2.0 ± 3.3 mmol C m-2 d-1 (mean ± standard deviation associated with spatial variability). We attribute this discrepancy to (1) elevated PP rates (> 600 mg C m-2 d-1) over the shelf prior to our survey, (2) freshwater dilution by river runoff and ice melt, and (3) the presence of cold surface waters offshore. Only the Mackenzie River delta and localized shelf areas directly affected by upwelling were identified as substantial sources of CO2 to the atmosphere (> 10 mmol C m-2 d-1). Daily PP rates were generally < 100 mg C m-2 d-1 and cumulated to a total PP of ~ 437.6 × 103 t C for the region over a 35-day period. This amount was about twice the

Going with the flow: Tidal influence on the occurrence of the harbour porpoise (Phocoena phocoena) in the Marsdiep area, The Netherlands

NASA Astrophysics Data System (ADS)

IJsseldijk, Lonneke L.; Camphuysen, Kees C. J.; Nauw, Janine J.; Aarts, Geert

2015-09-01

One of the most important factors explaining the distribution and behaviour of coastal marine mammals are tides. Tidal forces drive a large number of primary and secondary processes, such as changes in water depth, salinity, temperature, current velocity and direction. Unravelling which tidal process is the most influential for a certain species is often challenging, due to a lack of observations of all tide related covariates, strong correlation between them, and the elusive nature of most marine organisms which often hampers their detection. In the Marsdiep area, a tidal inlet between the North Sea and the Dutch Wadden Sea, the presence of harbour porpoises (Phocoena phocoena) was studied as a function of tide related covariates. Observations were carried out in early spring from a ferry crossing the inlet on a half hourly basis. Environmental and sightings data were collected by one observer, while an on-board Acoustic Doppler Current Profiler (ADCP) and temperature sensor continuously recorded current velocity profiles and temperature, respectively. Sea surface temperature and salinity were measured at a nearby jetty. Sightings (n = 134) were linked to tidal elevation, geographical position, local depth-averaged current velocity, water temperature (with and without trend correction) and salinity. Variation in sighting rate was best described by salinity, with highest sighting rate at high levels of salinity (> 30 g kg- 1), indicating that porpoises enter the area in bodies of (more saline) North Sea water. Second best variable was time of day, with the highest sighting rate early morning, and decreasing during the day. However, surveys in the morning happened to coincide more often with high water and hence, the apparent time of day effect could be due to collinearity. Most porpoises were present in the northern part of the Marsdiep, particularly during high tide. Tide dependent sighting rates confirmed that porpoises reside in the North Sea, and enter the

Organic matter controls of iron incorporation in growing sea ice

NASA Astrophysics Data System (ADS)

Janssens, Julie; Meiners, Klaus M.; Townsend, Ashley T.; Lannuzel, Delphine

2018-03-01

This study presents the first laboratory-controlled sea-ice growth experiment conducted under trace metal clean conditions. The role played by organic matter, in the incorporation of iron (Fe) into sea ice was investigated by means of laboratory ice-growth experiments using a titanium cold-finger apparatus. Experiments were also conducted to understand the role of extracellular polymeric substances (EPS) in the enrichment of ammonium in sea ice. Sea ice was grown from several seawater solutions containing different quantities and qualities of particulate Fe (PFe), dissolved Fe (DFe) and organic matter. Sea ice and seawater were analyzed for particulate organic carbon and nitrogen, macro-nutrients, extracellular EPS, PFe and DFe, and particulate aluminium. The experiments showed that biogenic PFe is preferentially incorporated into sea ice compared to lithogenic PFe. Furthermore, sea ice grown from ultra-violet (UV) and non-UV treated seawaters exhibits contrasting incorporation rates of organic matter and Fe. Whereas the effects of UV-treatments were not always significant, we do find indications that the type or organic matter controls the enrichment of Fe in forming sea ice.. Specifically, we come to the conclusion that the incorporation of DFe is favored by the presence of organic ligands in the source solution.

The role of feedbacks in Antarctic sea ice change

NASA Astrophysics Data System (ADS)

Feltham, D. L.; Frew, R. C.; Holland, P.

2017-12-01

The changes in Antarctic sea ice over the last thirty years have a strong seasonal dependence, and the way these changes grow in spring and decay in autumn suggests that feedbacks are strongly involved. The changes may ultimately be caused by atmospheric warming, the winds, snowfall changes, etc., but we cannot understand these forcings without first untangling the feedbacks. A highly simplified coupled sea ice -mixed layer model has been developed to investigate the importance of feedbacks on the evolution of sea ice in two contrasting regions in the Southern Ocean; the Amundsen Sea where sea ice extent has been decreasing, and the Weddell Sea where it has been expanding. The change in mixed layer depth in response to changes in the atmosphere to ocean energy flux is implicit in a strong negative feedback on ice cover changes in the Amundsen Sea, with atmospheric cooling leading to a deeper mixed layer resulting in greater entrainment of warm Circumpolar Deep Water, causing increased basal melting of sea ice. This strong negative feedback produces counter intuitive responses to changes in forcings in the Amundsen Sea. This feedback is absent in the Weddell due to the complete destratification and strong water column cooling that occurs each winter in simulations. The impact of other feedbacks, including the albedo feedback, changes in insulation due to ice thickness and changes in the freezing temperature of the mixed layer, were found to be of secondary importance compared to changes in the mixed layer depth.

Persuasive History: A Critical Comparison of Television's "Victory at Sea" and "The World at War."

ERIC Educational Resources Information Center

Mattheisen, Donald J.

1992-01-01

Discusses the television series "Victory at Sea" and "The World at War" and their use in teaching about World War II. Contrasts that war's glorious portrayal in "Victory at Sea" with the more ambiguous presentation of "The World at War." Suggests that students can learn a great deal about war and film itself…

South China Sea summer monsoon onset in relation to the off-equatorial ITCZ

NASA Astrophysics Data System (ADS)

Zhou, Wen; Chan, Johnny Chung-Leung; Li, Chongyin

2005-09-01

Observations of the South China Sea summer monsoon (SCSSM) demonstrate the different features between the early and late onsets of the monsoon. The determining factor related to the onset and the resultant monsoon rainfall might be the off-equatorial ITCZ besides the land-sea thermal contrast. The northward-propagating cumulus convection over the northern Indian Ocean could enhance the monsoon trough so that the effect of the horizontal advection of moisture and heat is substantially increased, thus westerlies can eventually penetrate and prevail over the South China Sea (SCS) region.

An inter-sensor comparison of the microwave signatures of Arctic sea ice

NASA Technical Reports Server (NTRS)

Onstott, R. G.

1986-01-01

Active and passive microwave and physical properties of Arctic sea ice in the marginal ice zone were measured during the summer. Results of an intercomparison of data acquired by an aircraft synthetic aperture radar, a passive microwave imager and a helicopter-mounted scatterometer indicate that early-to-mid summer sea ice microwave signatures are dominated by snowpack characteristics. Measurements show that the greatest contrast between thin first-year and multiyear sea ice occurs when operating actively between 5 and 10 GHz. Significant information about the state of melt of snow and ice is contained in the active and passive microwave signatures.

Functional structure of laminated microbial sediments from a supratidal sandy beach of the German Wadden Sea (St. Peter-Ording)

NASA Astrophysics Data System (ADS)

Bühring, Solveig I.; Kamp, Anja; Wörmer, Lars; Ho, Stephanie; Hinrichs, Kai-Uwe

2014-01-01

Hidden for the untrained eye through a thin layer of sand, laminated microbial sediments occur in supratidal beaches along the North Sea coast. The inhabiting microbial communities organize themselves in response to vertical gradients of light, oxygen or sulfur compounds. We performed a fine-scale investigation on the vertical zonation of the microbial communities using a lipid biomarker approach, and assessed the biogeochemical processes using a combination of microsensor measurements and a 13C-labeling experiment. Lipid biomarker fingerprinting showed the overarching importance of cyanobacteria and diatoms in these systems, and heterocyst glycolipids revealed the presence of diazotrophic cyanobacteria even in 9 to 20 mm depth. High abundance of ornithine lipids (OL) throughout the system may derive from sulfate reducing bacteria, while a characteristic OL profile between 5 and 8 mm may indicate presence of purple non-sulfur bacteria. The fate of 13C-labeled bicarbonate was followed by experimentally investigating the uptake into microbial lipids, revealing an overarching importance of cyanobacteria for carbon fixation. However, in deeper layers, uptake into purple sulfur bacteria was evident, and a close microbial coupling could be shown by uptake of label into lipids of sulfate reducing bacteria in the deepest layer. Microsensor measurements in sediment cores collected at a later time point revealed the same general pattern as the biomarker analysis and the labeling experiments. Oxygen and pH-microsensor profiles showed active photosynthesis in the top layer. The sulfide that diffuses from deeper down and decreases just below the layer of active oxygenic photosynthesis indicates the presence of sulfur bacteria, like anoxygenic phototrophs that use sulfide instead of water for photosynthesis.

Changes in the seasonality of Arctic sea ice and temperature

NASA Astrophysics Data System (ADS)

Bintanja, R.

2012-04-01

Observations show that the Arctic sea ice cover is currently declining as a result of climate warming. According to climate models, this retreat will continue and possibly accelerate in the near-future. However, the magnitude of this decline is not the same throughout the year. With temperatures near or above the freezing point, summertime Arctic sea ice will quickly diminish. However, at temperatures well below freezing, the sea ice cover during winter will exhibit a much weaker decline. In the future, the sea ice seasonal cycle will be no ice in summer, and thin one-year ice in winter. Hence, the seasonal cycle in sea ice cover will increase with ongoing climate warming. This in itself leads to an increased summer-winter contrast in surface air temperature, because changes in sea ice have a dominant influence on Arctic temperature and its seasonality. Currently, the annual amplitude in air temperature is decreasing, however, because winters warm faster than summer. With ongoing summer sea ice reductions there will come a time when the annual temperature amplitude will increase again because of the large seasonal changes in sea ice. This suggests that changes in the seasonal cycle in Arctic sea ice and temperature are closely, and intricately, connected. Future changes in Arctic seasonality (will) have an profound effect on flora, fauna, humans and economic activities.

Influence of the Yellow Sea Warm Current on phytoplankton community in the central Yellow Sea

NASA Astrophysics Data System (ADS)

Liu, Xin; Chiang, Kuo-Ping; Liu, Su-Mei; Wei, Hao; Zhao, Yuan; Huang, Bang-Qin

2015-12-01

In early spring, a hydrological front emerges in the central Yellow Sea, resulting from the intrusion of the high temperature and salinity Yellow Sea Warm Current (YSWC). The present study, applying phytoplankton pigments and flow cytometry measurements in March of 2007 and 2009, focuses on the biogeochemical effects of the YSWC. The nutrients fronts were coincident with the hydrological front, and a positive linear relationship between nitrate and salinity was found in the frontal area. This contrast with the common situation of coastal waters where high salinity values usually correlate with poor nutrients. We suggested nutrient concentrations of the YSWC waters might have been enhanced by mixing with the local nutrient-rich waters when it invaded the Yellow Sea from the north of the Changjiang estuary. In addition, our results indicate that the relative abundance of diatoms ranged from 26% to 90%, showing a higher value in the YSCC than in YSWC waters. Similar distributions were found between diatoms and dinoflagellates, however the cyanobacteria and prasinophytes showed an opposite distribution pattern. Good correlations were found between the pigments and flow cytometry observations on the picophytoplankton groups. Prasinophytes might be the major contributor to pico-eukaryotes in the central Yellow Sea as similar distributional patterns and significant correlations between them. It seems that the front separates the YSWC from the coastal water, and different phytoplankton groups are transported in these water masses and follow their movement. These results imply that the YSWC plays important roles in the distribution of nutrients, phytoplankton biomass and also in the community structure of the central Yellow Sea.

New Visualizations Highlight New Information on the Contrasting Arctic and Antarctic Sea-Ice Trends Since the Late 1970s

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.; DiGirolamo, Nicolo E.

2016-01-01

Month-by-month ranking of 37 years (1979-2015) of satellite-derived sea-ice extents in the Arctic and Antarctic reveals interesting new details in the overall trends toward decreasing sea-ice coverage in the Arctic and increasing sea-ice coverage in the Antarctic. The Arctic decreases are so definitive that there has not been a monthly record high in Arctic sea-ice extents in any month since 1986, a time period during which there have been 75 monthly record lows. The Antarctic, with the opposite but weaker trend toward increased ice extents, experienced monthly record lows in 5 months of 1986, then 6 later monthly record lows scattered through the dataset, with the last two occurring in 2006, versus 45 record highs since 1986. However, in the last three years of the 1979-2015 dataset, the downward trends in Arctic sea-ice extents eased up, with no new record lows in any month of 2013 or 2014 and only one record low in 2015,while the upward trends in Antarctic ice extents notably strengthened, with new record high ice extents in 4 months (August-November) of 2013, in 6 months (April- September) of 2014, and in 3 months (January, April, and May) of 2015. Globally, there have been only 3 monthly record highs since 1986 (only one since 1988), whereas there have been 43 record lows, although the last record lows (in the 1979-2015 dataset) occurred in 2012.

The Sea Level Fingerprints of Global Change

NASA Astrophysics Data System (ADS)

Mitrovica, J. X.; Hay, C.; Kopp, R. E., III; Morrow, E.

2014-12-01

It may be difficult to persuade those living in northern Europe that the sea level changes that their coastal communities face depends less on the total melting of polar ice sheets and glaciers than on the individual contributions to this total. In particular, melting of a specific ice sheet or mountain glacier drives deformational, gravitational and rotational perturbations to the Earth system that are manifest in a unique geometry, or fingerprint, of global sea level change. For example, melting from the Greenland Ice Sheet equivalent to 1 mm/yr of global mean sea level (GMSL) rise will lead to sea level rise of ~0 mm/yr in Dublin, ~0.2 mm/yr in Amsterdam, ~0.4 mm/yr in Boston and ~1.2 mm/yr in Cape Town. In contrast, if the same volume of ice melted from the West Antarctic Ice Sheet, all of the above sites would experience a sea level rise in the range 1.1-1.2 mm/yr. These fingerprints of modern ice melting, together with ocean thermal expansion and dynamic effects, and the ongoing signal from glacial isostatic adjustment in response to the last ice age, combine to produce a sea level field with significant geographic variability. In this talk I will highlight an analysis of global tide gauge records that takes full advantage of this variability to estimate both GMSL and the sources of meltwater over the last century, and to project GMSL to the end of the current century.

The Satellite Passive-Microwave Record of Sea Ice in the Ross Sea Since Late 1978

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.

2009-01-01

the highest rate of increase in sea ice coverage of any of five standard divisions of the Southern Ocean, although the Weddell Sea, Indian Ocean, and Western Pacific Ocean all also had sea ice increases, while only the Bellingshausen/Smundsen Seas experienced overall sea ice decreases. Overall, the Southern Ocean sea ice cover increased at an average rate of 10,800 plus or minus 2,500 square kilometers per year between November 1978 and December 2007, with every month showing positive values although with some of these values not being statistically significant. The sea ice increase since November 1978 was preceded by a sharp decrease in Southern Ocean ice coverage in the 1970's and is in marked contrast to the decrease in Arctic sea ice coverage that has occurred both in the period since November 1978 and since earlier in the 1970's. On a yearly average bases, for 1979-2007 the Southern Ocean sea ice extent increased at a rate of 1.0 plus or minus 0.4% per decade, whereas the Arctic ice extent decreased at the much greater rate of 4.0 plus or minus 0.4 percent per decade (closer to the % per decade rate of increase in the Ross Sea). Considerable research is ongoing to explain the differences.

Glacial conditions in the Red Sea

NASA Astrophysics Data System (ADS)

Rohling, Eelco J.

1994-10-01

In this paper, results from previous studies on planktonic foraminifera, δ18O, and global sea level are combined to discuss climatic conditions in the Red Sea during the last glacial maximum (18,000 B.P.). First, the influence of 120-m sea level lowering on the exchange transport through the strait of Bab-el-Mandab is considered. This strait is the only natural connection of the Red Sea to the open ocean. Next, glacial Red Sea outflow salinity is estimated (about 48 parts per thousand) from the foraminiferal record. Combined, these results yield an estimate of the glacial net water deficit, which appears to have been quite similar to the present (about 2 m yr-1). Finally, budget calculation of δ18O fluxes suggests that the glacial δ18O value of evaporation was about 50% of the present value. This is considered to have resulted from substantially increased mean wind speeds over the glacial Red Sea, which would have caused a rapid drop in the kinematic fractionation factor for 18O. The sensitivity of the calculated values for water deficit and isotopic fractionation to the various assumptions and estimates is evaluated in the discussion. Improvents are to be expected especially through research on the glacial salinity contrast between the Red Sea and Gulf of Aden. It is argued, however, that such future improvement will likely result in a worsening of the isotopic discrepancy, thus increasing the need for an additional mechanism that influenced fractionation (such as mean wind speed). This study demonstrates the need for caution when calculating paleosalinities from δ18O records under the assumption that the modern S∶δ18O relation has remained constant through time. Previously overlooked factors, such as mean wind speed, may have significantly altered that relation in the past.

Fish communities across a spectrum of habitats in the western Beaufort Sea and Chukchi Sea

NASA Astrophysics Data System (ADS)

Logerwell, E.; Busby, M.; Carothers, C.; Cotton, S.; Duffy-Anderson, J.; Farley, E.; Goddard, P.; Heintz, R.; Holladay, B.; Horne, J.; Johnson, S.; Lauth, B.; Moulton, L.; Neff, D.; Norcross, B.; Parker-Stetter, S.; Seigle, J.; Sformo, T.

2015-08-01

The increased scientific interest in the Arctic due to climate change and potential oil and gas development has resulted in numerous surveys of Arctic marine fish communities since the mid-2000s. Surveys have been conducted in nearly all Arctic marine fish habitats: from lagoons, beaches and across the continental shelf and slope. This provides an opportunity only recently available to study Arctic fish communities across a spectrum of habitats. We examined fish survey data from lagoon, beach, nearshore benthic, shelf pelagic and shelf benthic habitats in the western Beaufort Sea and Chukchi Sea. Specifically, we compare and contrast relative fish abundance and length (a proxy for age) among habitats and seas. We also examined ichthyoplankton presence/absence and abundance of dominant taxa in the shelf habitat. Our synthesis revealed more similarities than differences between the two seas. For example, our results show that the nearshore habitat is utilized by forage fish across age classes, and is also a nursery area for other species. Our results also indicated that some species may be expanding their range to the north, for example, Chinook Salmon. In addition, we documented the presence of commercially important taxa such as Walleye Pollock and flatfishes (Pleuronectidae). Our synthesis of information on relative abundance and age allowed us to propose detailed conceptual models for the life history distribution of key gadids in Arctic food webs: Arctic and Saffron Cod. Finally, we identify research gaps, such as the need for surveys of the surface waters of the Beaufort Sea, surveys of the lagoons of the Chukchi Sea, and winter season surveys in all areas. We recommend field studies on fish life history that sample multiple age classes in multiple habitats throughout the year to confirm, resolve and interpret the patterns in fish habitat use that we observed.

Coccolithophore assemblage response to Black Sea Water inflow into the North Aegean Sea (NE Mediterranean)

NASA Astrophysics Data System (ADS)

Karatsolis, B.-Th.; Triantaphyllou, M. V.; Dimiza, M. D.; Malinverno, E.; Lagaria, A.; Mara, P.; Archontikis, O.; Psarra, S.

2017-10-01

This study aims to presents the species composition of living coccolithophore communities in the NE Aegean Sea, investigating their spatial and temporal variations along a north-south transect in the area receiving the inflowing surface Black Sea Water (BSW) over the deeper Levantine Water (LW) layer. Coccolithophores in the area were relatively diverse and a total of 95 species over 3 sampling periods studied were recognized using Scanning Electron Microscope (SEM) techniques. R-mode hierarchical cluster analysis distinguished two coccolithophore Groups (I, IIa, IIb, IIc) with different ecological preferences. Emiliania huxleyi was the most abundant species of Group I, whereas Syracosphaera spp., Rhabdosphaera spp. and holococcolithophores were prevailing in the highly diversified Group II assemblages. Biometric analysis conducted on E. huxleyi coccoliths from Aegean water column and Black Sea sediment trap samples, indicated that during autumn, NE Aegean specimens in samples under BSW influence were featured by unimodal distribution concerning the coccolith relative tube width, with values similar to those provided by the Black Sea specimens. In early spring, coccoliths in the stations with increased BSW influx displayed a bimodal pattern of relative tube width with smaller values found mostly in the surface layers, while the distribution became again unimodal and dominated by larger values within the deeper LW layers. In the summer period, the typical LW holococcolithophore species (Group II) presented low cell numbers in the surface layer (<20 m), which is their usual ecological niche in the Aegean Sea, compared to greater depths, therefore marking LW mass flowing beneath the less saline BSW surface lid. In contrast to Black Sea early summer bloom conditions, E. huxleyi was almost absent in the NE Aegean during the summer sampling period.

Loki Patera: A Magma Sea Story

NASA Technical Reports Server (NTRS)

Veeder, G. J.; Matson, D. L.; Rathbun, A. G.

2005-01-01

We consider Loki Patera on Io as the surface expression of a large uniform body of magma. Our model of the Loki magma sea is some 200 km across; larger than a lake but smaller than an ocean. The depth of the magma sea is unknown, but assumed to be deep enough that bottom effects can be ignored. Edge effects at the shore line can be ignored to first order for most of the interior area. In particular, we take the dark material within Loki Patera as a thin solidified lava crust whose hydrostatic shape follows Io's isostatic surface (approx. 1815 km radius of curvature). The dark surface of Loki appears to be very smooth on both regional and local (subresolution) scales. The thermal contrast between the low and high albedo areas within Loki is consistent with the observed global correlation. The composition of the model magma sea is basaltic and saturated with dissolved SO2 at depth. Its average, almost isothermal, temperature is at the liquidus for basalt. Additional information is included in the original extended abstract.

Diatom evidence on Wisconsin and Holocene events in the Bering Sea

USGS Publications Warehouse

Sancetta, C.; Robinson, S.W.

1983-01-01

Previous work on surface (modern) sediments has defined diatom species which appear to be good indicators of various oceanographic/ecologic conditions in the North Pacific Ocean and marginal seas. Three long cores from the eastern and northern sides of the Aleutian Basin show changes in species assemblage which can be interpreted in terms of changes in the ocean environment during the last glaciation (Wisconsin) and the Holocene. The early and late Wisconsin maxima were times of prolonged annual sea-ice cover and a short cool period of phytoplankton productivity during the ice-free season. The middle Wisconsin interstade, at least in the southern Bering Sea, had greater seasonal contrast than today, with some winter sea-ice cover, an intensified temperature minimum, and high spring productivity. Variations in clastic and reworked fossil material imply varying degrees of transport to the basin by Alaskan rivers. The results of Jouse?? from the central Bering Sea generally correspond with those presented here, although there are problems with direct comparison. ?? 1983.

Contrasting Effects of Historical Sea Level Rise and Contemporary Ocean Currents on Regional Gene Flow of Rhizophora racemosa in Eastern Atlantic Mangroves.

PubMed

Ngeve, Magdalene N; Van der Stocken, Tom; Menemenlis, Dimitris; Koedam, Nico; Triest, Ludwig

2016-01-01

Mangroves are seafaring taxa through their hydrochorous propagules that have the potential to disperse over long distances. Therefore, investigating their patterns of gene flow provides insights on the processes involved in the spatial genetic structuring of populations. The coastline of Cameroon has a particular geomorphological history and coastal hydrology with complex contemporary patterns of ocean currents, which we hypothesize to have effects on the spatial configuration and composition of present-day mangroves within its spans. A total of 982 trees were sampled from 33 transects (11 sites) in 4 estuaries. Using 11 polymorphic SSR markers, we investigated genetic diversity and structure of Rhizophora racemosa, a widespread species in the region. Genetic diversity was low to moderate and genetic differentiation between nearly all population pairs was significant. Bayesian clustering analysis, PCoA, estimates of contemporary migration rates and identification of barriers to gene flow were used and complemented with estimated dispersal trajectories of hourly released virtual propagules, using high-resolution surface current from a mesoscale and tide-resolving ocean simulation. These indicate that the Cameroon Volcanic Line (CVL) is not a present-day barrier to gene flow. Rather, the Inter-Bioko-Cameroon (IBC) corridor, formed due to sea level rise, allows for connectivity between two mangrove areas that were isolated during glacial times by the CVL. Genetic data and numerical ocean simulations indicated that an oceanic convergence zone near the Cameroon Estuary complex (CEC) presents a strong barrier to gene flow, resulting in genetic discontinuities between the mangrove areas on either side. This convergence did not result in higher genetic diversity at the CEC as we had hypothesized. In conclusion, the genetic structure of Rhizophora racemosa is maintained by the contrasting effects of the contemporary oceanic convergence and historical climate change

Contrasting Effects of Historical Sea Level Rise and Contemporary Ocean Currents on Regional Gene Flow of Rhizophora racemosa in Eastern Atlantic Mangroves

PubMed Central

Ngeve, Magdalene N.; Van der Stocken, Tom; Menemenlis, Dimitris; Koedam, Nico; Triest, Ludwig

2016-01-01

Mangroves are seafaring taxa through their hydrochorous propagules that have the potential to disperse over long distances. Therefore, investigating their patterns of gene flow provides insights on the processes involved in the spatial genetic structuring of populations. The coastline of Cameroon has a particular geomorphological history and coastal hydrology with complex contemporary patterns of ocean currents, which we hypothesize to have effects on the spatial configuration and composition of present-day mangroves within its spans. A total of 982 trees were sampled from 33 transects (11 sites) in 4 estuaries. Using 11 polymorphic SSR markers, we investigated genetic diversity and structure of Rhizophora racemosa, a widespread species in the region. Genetic diversity was low to moderate and genetic differentiation between nearly all population pairs was significant. Bayesian clustering analysis, PCoA, estimates of contemporary migration rates and identification of barriers to gene flow were used and complemented with estimated dispersal trajectories of hourly released virtual propagules, using high-resolution surface current from a mesoscale and tide-resolving ocean simulation. These indicate that the Cameroon Volcanic Line (CVL) is not a present-day barrier to gene flow. Rather, the Inter-Bioko-Cameroon (IBC) corridor, formed due to sea level rise, allows for connectivity between two mangrove areas that were isolated during glacial times by the CVL. Genetic data and numerical ocean simulations indicated that an oceanic convergence zone near the Cameroon Estuary complex (CEC) presents a strong barrier to gene flow, resulting in genetic discontinuities between the mangrove areas on either side. This convergence did not result in higher genetic diversity at the CEC as we had hypothesized. In conclusion, the genetic structure of Rhizophora racemosa is maintained by the contrasting effects of the contemporary oceanic convergence and historical climate change

Soil Moisture, Coastline Curvature, and Sea Breeze Initiated Precipitation Over Florida

NASA Technical Reports Server (NTRS)

Baker, R. David; Lynn, Barry H.; Boone, Aaron; Tao, Wei-Kuo

1999-01-01

Land surface-atmosphere interaction plays a key role in the development of summertime convection and precipitation over the Florida peninsula. Land-ocean temperature contrasts induce sea-breeze circulations along both coasts. Clouds develop along sea-breeze fronts, and significant precipitation can occur during the summer months. However, other factors such as soil moisture distribution and coastline curvature may modulate the timing, location, and intensity of sea breeze initiated precipitation. Here, we investigate the role of soil moisture and coastline curvature on Florida precipitation using the 3-D Goddard Cumulus Ensemble (GCE) cloud model coupled with the Parameterization for Land-Atmosphere-Cloud Exchange (PLACE) land surface model. This study utilizes data from the Convection and Precipitation Electrification Experiment (CaPE) collected on 27 July 1991. Our numerical simulations suggest that a realistic distribution of soil moisture influences the location and intensity of precipitation but not the timing of precipitation. In contrast, coastline curvature affects the timing and location of precipitation but has little influence on peak rainfall rates. However, both factors (soil moisture and coastline curvature) are required to fully account for observed rainfall amounts.

A numerical study of the effects of a large sandbar upon sea breeze development

NASA Technical Reports Server (NTRS)

Kessler, R. C.; Pielke, R. A.; Mcqueen, J.; Eppel, D.

1985-01-01

Two-dimensional numerical simulations of sea breeze development over a large sandbar on the North Sea coast of Germany are reported. The numerical model used in these experiments contains a detailed treatment of soil moisture, which allows evaluation of the effects of differential surface characteristics on the airflow pattern. Results of the simulations indicate that the contrast between the moist sandbar and adjacent dry land, the tidal inundation of the sandbar, and the westward penetration of the Baltic sea breeze play important roles in the development of mesoscale airflow patterns in the sandbar region.

Mechanisms of interannual- to decadal-scale winter Labrador Sea ice variability

NASA Astrophysics Data System (ADS)

Close, S.; Herbaut, C.; Houssais, M.-N.; Blaizot, A.-C.

2017-12-01

The variability of the winter sea ice cover of the Labrador Sea region and its links to atmospheric and oceanic forcing are investigated using observational data, a coupled ocean-sea ice model and a fully-coupled model simulation drawn from the CMIP5 archive. A consistent series of mechanisms associated with high sea ice cover are found amongst the various data sets. The highest values of sea ice area occur when the northern Labrador Sea is ice covered. This region is found to be primarily thermodynamically forced, contrasting with the dominance of mechanical forcing along the eastern coast of Baffin Island and Labrador, and the growth of sea ice is associated with anomalously fresh local ocean surface conditions. Positive fresh water anomalies are found to propagate to the region from a source area off the southeast Greenland coast with a 1 month transit time. These anomalies are associated with sea ice melt, driven by the enhanced offshore transport of sea ice in the source region, and its subsequent westward transport in the Irminger Current system. By combining sea ice transport through the Denmark Strait in the preceding autumn with the Greenland Blocking Index and the Atlantic Multidecadal Oscillation Index, strong correlation with the Labrador Sea ice area of the following winter is obtained. This relationship represents a dependence on the availability of sea ice to be melted in the source region, the necessary atmospheric forcing to transport this offshore, and a further multidecadal-scale link with the large-scale sea surface temperature conditions.

Light comfort zones of mesopelagic acoustic scattering layers in two contrasting optical environments

NASA Astrophysics Data System (ADS)

Røstad, Anders; Kaartvedt, Stein; Aksnes, Dag L.

2016-07-01

We make a comparison of the mesopelagic sound scattering layers (SLs) in two contrasting optical environments; the clear Red Sea and in murkier coastal waters of Norway (Masfjorden). The depth distributions of the SL in Masfjorden are shallower and narrower than those of the Red Sea. This difference in depth distribution is consistent with the hypothesis that the organisms of the SL distribute according to similar light comfort zones (LCZ) in the two environments. Our study suggest that surface and underwater light measurements ranging more than 10 orders of magnitude is required to assess the controlling effects of light on SL structure and dynamics.

Microsporidia-nematode associations in methane seeps reveal basal fungal parasitism in the deep sea

PubMed Central

Sapir, Amir; Dillman, Adler R.; Connon, Stephanie A.; Grupe, Benjamin M.; Ingels, Jeroen; Mundo-Ocampo, Manuel; Levin, Lisa A.; Baldwin, James G.; Orphan, Victoria J.; Sternberg, Paul W.

2013-01-01

The deep sea is Earth's largest habitat but little is known about the nature of deep-sea parasitism. In contrast to a few characterized cases of bacterial and protistan parasites, the existence and biological significance of deep-sea parasitic fungi is yet to be understood. Here we report the discovery of a fungus-related parasitic microsporidium, Nematocenator marisprofundi n. gen. n. sp. that infects benthic nematodes at methane seeps on the Pacific Ocean floor. This infection is species-specific and has been temporally and spatially stable over 2 years of sampling, indicating an ecologically consistent host-parasite interaction. A high distribution of spores in the reproductive tracts of infected males and females and their absence from host nematodes' intestines suggests a sexual transmission strategy in contrast to the fecal-oral transmission of most microsporidia. N. marisprofundi targets the host's body wall muscles causing cell lysis, and in severe infection even muscle filament degradation. Phylogenetic analyses placed N. marisprofundi in a novel and basal clade not closely related to any described microsporidia clade, suggesting either that microsporidia-nematode parasitism occurred early in microsporidia evolution or that host specialization occurred late in an ancient deep-sea microsporidian lineage. Our findings reveal that methane seeps support complex ecosystems involving interkingdom interactions between bacteria, nematodes, and parasitic fungi and that microsporidia parasitism exists also in the deep-sea biosphere. PMID:24575084

Steady as He Goes: At-Sea Movement of Adult Male Australian Sea Lions in a Dynamic Marine Environment

PubMed Central

Lowther, Andrew D.; Harcourt, Robert G.; Page, Bradley; Goldsworthy, Simon D.

2013-01-01

The southern coastline of Australia forms part of the worlds' only northern boundary current system. The Bonney Upwelling occurs every austral summer along the south-eastern South Australian coastline, a region that hosts over 80% of the worlds population of an endangered endemic otariid, the Australian sea lion. We present the first data on the movement characteristics and foraging behaviour of adult male Australian sea lions across their South Australian range. Synthesizing telemetric, oceanographic and isotopic datasets collected from seven individuals enabled us to characterise individual foraging behaviour over an approximate two year time period. Data suggested seasonal variability in stable carbon and nitrogen isotopes that could not be otherwise explained by changes in animal movement patterns. Similarly, animals did not change their foraging patterns despite fine-scale spatial and temporal variability of the upwelling event. Individual males tended to return to the same colony at which they were tagged and utilized the same at-sea regions for foraging irrespective of oceanographic conditions or time of year. Our study contrasts current general assumptions that male otariid life history strategies should result in greater dispersal, with adult male Australian sea lions displaying central place foraging behaviour similar to males of other otariid species in the region. PMID:24086338

Seaweeds in cold seas: evolution and carbon acquisition.

PubMed

Raven, John A; Johnston, Andrew M; Kübler, Janet E; Korb, Rebecca; McInroy, Shona G; Handley, Linda L; Scrimgeour, Charlie M; Walker, Diana I; Beardall, John; Clayton, Margaret N; Vanderklift, Mathew; Fredriksen, Stein; Dunton, Kenneth H

2002-10-01

Much evidence suggests that life originated in hydrothermal habitats, and for much of the time since the origin of cyanobacteria (at least 2.5 Ga ago) and of eukaryotic algae (at least 2.1 Ga ago) the average sea surface and land surface temperatures were higher than they are today. However, there have been at least four significant glacial episodes prior to the Pleistocene glaciations. Two of these (approx. 2.1 and 0.7 Ga ago) may have involved a 'Snowball Earth' with a very great impact on the algae (sensu lato) of the time (cyanobacteria, Chlorophyta and Rhodophyta) and especially those that were adapted to warm habitats. By contrast, it is possible that heterokont, dinophyte and haptophyte phototrophs only evolved after the Carboniferous-Permian ice age (approx. 250 Ma ago) and so did not encounter low (sea surface temperatures until the Antarctic cooled some 15 Ma ago. Despite this, many of the dominant macroalgae in cooler seas today are (heterokont) brown algae, and many laminarians cannot reproduce at temperatures above 18-25 degrees C. By contrast to plants in the aerial environment, photosynthetic structures in water are at essentially the same temperature as the fluid medium. The impact of low temperatures on photosynthesis by marine macrophytes is predicted to favour diffusive CO(2) entry rather than a CO(2)-concentrating mechanism. Some evidence favours this suggestion, but more data are needed.

Early Pliocene onset of modern Nordic Seas circulation related to ocean gateway changes.

PubMed

De Schepper, Stijn; Schreck, Michael; Beck, Kristina Marie; Matthiessen, Jens; Fahl, Kirsten; Mangerud, Gunn

2015-10-28

The globally warm climate of the early Pliocene gradually cooled from 4 million years ago, synchronous with decreasing atmospheric CO2 concentrations. In contrast, palaeoceanographic records indicate that the Nordic Seas cooled during the earliest Pliocene, before global cooling. However, a lack of knowledge regarding the precise timing of Nordic Seas cooling has limited our understanding of the governing mechanisms. Here, using marine palynology, we show that cooling in the Nordic Seas was coincident with the first trans-Arctic migration of cool-water Pacific mollusks around 4.5 million years ago, and followed by the development of a modern-like Nordic Seas surface circulation. Nordic Seas cooling precedes global cooling by 500,000 years; as such, we propose that reconfiguration of the Bering Strait and Central American Seaway triggered the development of a modern circulation in the Nordic Seas, which is essential for North Atlantic Deep Water formation and a precursor for more widespread Greenland glaciation in the late Pliocene.

Modeling land subsidence due to shallow-water hydrocarbon production: A case study in the northern Adriatic Sea

NASA Astrophysics Data System (ADS)

Gambolati, G.; Castelletto, N.; Ferronato, M.; Janna, C.; Teatini, P.

2012-12-01

One major environmental concern of subsurface fluid withdrawal is land subsidence. The issue of a reliable estimate and prediction of the expected anthropogenic land subsidence is particularly important whenever the production of hydrocarbon (oil and gas) occurs from large reservoirs located close to deltaic zones (e.g., Mississippi, Po, Nile, Niger, Yellow rivers) or shallow-water with low-lying coastlands (e.g., Northern Caspian sea, Dutch Wadden Sea). In such cases even a small reduction of the ground elevation relative to the mean sea level may impact seriously on human settlements and natural environment. The monitoring of the ongoing land subsidence has been significantly improved over the last decade by SAR-based interferometry. These measurements can be quite effectively used to map the process and calibrate geomechanical models for predicting the future event. However, this powerful methodology cannot be implemented off-shore. Although permanent GPS stations can be established to monitor the movement of the production facilities usually installed above the gravity center of a reservoir, an accurate characterization of the settlement bowl affecting the sea bottom, with a possible migration toward the shore, is a challenge still today. In the present communication the case study of the Riccione gas reservoir is discussed. The field is located in the near-shore northern Adriatic Sea, approximately 15 km far from the coastline, where the seawater height is about 20 m. The gas-bearing strata are 1100 m deep and are hydraulically connected to a relatively weak aquifer. Production of 70% of the cumulative reserves as of 2006 yielded a pore pressure decrease of 60 bars. Reliable geometry and geomechanical properties of the depleted formations were detected with the aid of a 3D seismic survey and a borehole equipped with radioactive markers, respectively. The latter pointed out that the Riccione formations are characterized by an unusually high oedometer

Spatial contrast sensitivity at twilight: luminance, monocularity, and oxygenation.

PubMed

Connolly, Desmond M

2010-05-01

Visual performance in dim light is compromised by lack of oxygen (hypoxia). The possible influence of altered oxygenation on foveal contrast sensitivity under mesopic (twilight) viewing conditions is relevant to aircrew flying at night, including when using night vision devices, but is poorly documented. Foveal contrast sensitivity was measured binocularly and monocularly in 12 subjects at 7 spatial frequencies, ranging from 0.5 to approximately 16 cycles per degree, using sinusoidal Gabor patch gratings. Hypoxic performance breathing 14.1% oxygen, equivalent to altitude exposure at 3048 m (10,000 ft), was compared with breathing air at sea level (normoxia) at low photopic (28 cd x m(-2)), borderline upper mesopic (approximately 2.1 cd x m(-2)) and midmesopic (approximately 0.26 cd x m(-2)) luminance. Mesopic performance was also assessed breathing 100% oxygen (hyperoxia). Typical 'inverted U' log/log plots of the contrast sensitivity function were obtained, with elevated thresholds (reduced sensitivity) at lower luminance. Binocular viewing enhanced sensitivity by a factor approximating square root of 2 for most conditions, supporting neural summation of the contrast signal, but had greater influence at the lowest light level and highest spatial frequencies (8.26 and 16.51 cpd). Respiratory challenges had no effect. Contrast sensitivity is poorer when viewing monocularly and especially at midmesopic luminance, with relevance to night flying. The foveal contrast sensitivity function is unaffected by respiratory disturbance when twilight conditions favor cone vision, despite known effects on retinal illumination (pupil size). The resilience of the contrast sensitivity function belies the vulnerability of foveal low contrast acuity to mild hypoxia at mesopic luminance.

Contrasting Decadal-Scale Changes in Elevation and ...

EPA Pesticide Factsheets

Northeastern US salt marshes face multiple co-stressors, including accelerating rates of relative sea level rise (RSLR), elevated nutrient inputs, and low sediment supplies. In order to evaluate how marsh surface elevations respond to such factors, we used surface elevation tables (SETs) and surface elevation pins to measure changes in marsh surface elevation in two eastern Long Island Sound salt marshes, Barn Island and Mamacoke marshes. We compare marsh elevation change at these two systems with recent rates of RSLR and find evidence of differences between the two sites; Barn Island is maintaining its historic rate of elevation gain (2.3 ± 0.24 mm year−1 from 2003 to 2013) and is no longer keeping pace with RSLR, while Mamacoke shows evidence of a recent increase in rates (4.2 ± 0.52 mm year−1 from 1994 to 2014) to maintain its elevation relative to sea level. In addition to data on short-term elevation responses at these marshes, both sites have unusually long and detailed data on historic vegetation species composition extending back more than half a century. Over this study period, vegetation patterns track elevation change relative to sea levels, with the Barn Island plant community shifting towards those plants that are found at lower elevations and the Mamacoke vegetation patterns showing little change in plant composition. We hypothesize that the apparent contrasting trend in marsh elevation at the sites is due to differences in sediment a

Prokaryotic degradation of high molecular weight dissolved organic matter in the deep-sea waters of NW Mediterranean Sea under in situ temperature and pressure conditions during contrasted hydrological conditions

NASA Astrophysics Data System (ADS)

Tamburini, C.; Boutrif, M.; Garel, M.; Sempéré, R.; Repeta, D.; Charriere, B.; Nerini, D.; Panagiotopoulos, C.

2016-02-01

The contribution of the semi-labile dissolved organic carbon (DOC) to the global prokaryotic production has been assessed in very few previous studies. Some experiments show rapid utilization of semi-reactive DOC by prokaryotes, while other experiments show almost no utilization at all. However, all these studies did not take into account the role of hydrostatic pressure for the degradation of organic matter. In this study, we investigate (1) the degradation of "natural" high molecular weight DOM HMW-DOM (obtained after ultrafiltration) and (2) the uptake of labeled extracellular polymeric substances (3H-EPS) incubated with deep-sea water samples (2000 m-depth, NW Mediterranean Sea) under in situ pressure conditions (HP) and under atmospheric compression after decompression of the deep samples (ATM) during stratified and mixed water conditions (deep sea convection). Our results indicated that during HP incubations DOC exhibited the highest degradation rates (kHP DOC = 0.82 d-1) compared to the ATM conditions were no or few degradation was observed (kATM DOC= 0.007 d-1). An opposite trend was observed for the HP incubations from mixed deep water masses. HP incubation measurements displayed the lowest DOC degradation (kHP DOC=0.031 d-1) compared to the ATM conditions (kATM DOC=0.62 d-1). These results imply the presence of allochthonous prokaryotic cells in deep-sea samples after a winter water mass convection. Same trends were found using 3H-EPS uptake rates which were higher at HP than at ATM conditions during stratified period conditions whereas the opposite patterns were observed during deep-sea convection event. Moreover, we found than Euryarchaea were the main contributors to 3H-EPS assimilation at 2000m-depth, representing 58% of the total cells actively assimilating 3H-EPS. This study demonstrates that remineralization rates of semi-labile DOC in deep NW Med. Sea are controlled by the prokaryotic communities, which are influenced by the hydrological

Arctic and Antarctic Sea Ice Changes and Impacts (Invited)

NASA Astrophysics Data System (ADS)

Nghiem, S. V.

2013-12-01

The extent of springtime Arctic perennial sea ice, important to preconditioning summer melt and to polar sunrise photochemistry, continues its precipitous reduction in the last decade marked by a record low in 2012, as the Bromine, Ozone, and Mercury Experiment (BROMEX) was conducted around Barrow, Alaska, to investigate impacts of sea ice reduction on photochemical processes, transport, and distribution in the polar environment. In spring 2013, there was further loss of perennial sea ice, as it was not observed in the ocean region adjacent to the Alaskan north coast, where there was a stretch of perennial sea ice in 2012 in the Beaufort Sea and Chukchi Sea. In contrast to the rapid and extensive loss of sea ice in the Arctic, Antarctic sea ice has a trend of a slight increase in the past three decades. Given the significant variability in time and in space together with uncertainties in satellite observations, the increasing trend of Antarctic sea ice may arguably be considered as having a low confidence level; however, there was no overall reduction of Antarctic sea ice extent anywhere close to the decreasing rate of Arctic sea ice. There exist publications presenting various factors driving changes in Arctic and Antarctic sea ice. After a short review of these published factors, new observations and atmospheric, oceanic, hydrological, and geological mechanisms contributed to different behaviors of sea ice changes in the Arctic and Antarctic are presented. The contribution from of hydrologic factors may provide a linkage to and enhance thermal impacts from lower latitudes. While geological factors may affect the sensitivity of sea ice response to climate change, these factors can serve as the long-term memory in the system that should be exploited to improve future projections or predictions of sea ice changes. Furthermore, similarities and differences in chemical impacts of Arctic and Antarctic sea ice changes are discussed. Understanding sea ice changes and

Spatially Mapped Reductions in the Length of the Arctic Sea Ice Season

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.

2014-01-01

Satellite data are used to determine the number of days having sea ice coverage in each year 1979-2013 and to map the trends in these ice-season lengths. Over the majority of the Arctic seasonal sea ice zone, the ice season shortened at an average rate of at least 5 days/decade between 1979 and 2013, and in a small area in the northeastern Barents Sea the rate of shortening reached over 65 days/decade. The only substantial non-coastal area with lengthening sea ice seasons is the Bering Sea, where the ice season lengthened by 5-15 days/decade. Over the Arctic as a whole, the area with ice seasons shortened by at least 5 days/decade is 12.4 × 10(exp 6) square kilimeters, while the area with ice seasons lengthened by at least 5 days/decade is only 1.1 × 10(exp 6) square kilometers. The contrast is even greater, percentage-wise, for higher rates.

Deep-sea diversity patterns are shaped by energy availability.

PubMed

Woolley, Skipton N C; Tittensor, Derek P; Dunstan, Piers K; Guillera-Arroita, Gurutzeta; Lahoz-Monfort, José J; Wintle, Brendan A; Worm, Boris; O'Hara, Timothy D

2016-05-19

The deep ocean is the largest and least-explored ecosystem on Earth, and a uniquely energy-poor environment. The distribution, drivers and origins of deep-sea biodiversity remain unknown at global scales. Here we analyse a database of more than 165,000 distribution records of Ophiuroidea (brittle stars), a dominant component of sea-floor fauna, and find patterns of biodiversity unlike known terrestrial or coastal marine realms. Both patterns and environmental predictors of deep-sea (2,000-6,500 m) species richness fundamentally differ from those found in coastal (0-20 m), continental shelf (20-200 m), and upper-slope (200-2,000 m) waters. Continental shelf to upper-slope richness consistently peaks in tropical Indo-west Pacific and Caribbean (0-30°) latitudes, and is well explained by variations in water temperature. In contrast, deep-sea species show maximum richness at higher latitudes (30-50°), concentrated in areas of high carbon export flux and regions close to continental margins. We reconcile this structuring of oceanic biodiversity using a species-energy framework, with kinetic energy predicting shallow-water richness, while chemical energy (export productivity) and proximity to slope habitats drive deep-sea diversity. Our findings provide a global baseline for conservation efforts across the sea floor, and demonstrate that deep-sea ecosystems show a biodiversity pattern consistent with ecological theory, despite being different from other planetary-scale habitats.

Quantifying model uncertainty in seasonal Arctic sea-ice forecasts

NASA Astrophysics Data System (ADS)

Blanchard-Wrigglesworth, Edward; Barthélemy, Antoine; Chevallier, Matthieu; Cullather, Richard; Fučkar, Neven; Massonnet, François; Posey, Pamela; Wang, Wanqiu; Zhang, Jinlun; Ardilouze, Constantin; Bitz, Cecilia; Vernieres, Guillaume; Wallcraft, Alan; Wang, Muyin

2017-04-01

Dynamical model forecasts in the Sea Ice Outlook (SIO) of September Arctic sea-ice extent over the last decade have shown lower skill than that found in both idealized model experiments and hindcasts of previous decades. Additionally, it is unclear how different model physics, initial conditions or post-processing techniques contribute to SIO forecast uncertainty. In this work, we have produced a seasonal forecast of 2015 Arctic summer sea ice using SIO dynamical models initialized with identical sea-ice thickness in the central Arctic. Our goals are to calculate the relative contribution of model uncertainty and irreducible error growth to forecast uncertainty and assess the importance of post-processing, and to contrast pan-Arctic forecast uncertainty with regional forecast uncertainty. We find that prior to forecast post-processing, model uncertainty is the main contributor to forecast uncertainty, whereas after forecast post-processing forecast uncertainty is reduced overall, model uncertainty is reduced by an order of magnitude, and irreducible error growth becomes the main contributor to forecast uncertainty. While all models generally agree in their post-processed forecasts of September sea-ice volume and extent, this is not the case for sea-ice concentration. Additionally, forecast uncertainty of sea-ice thickness grows at a much higher rate along Arctic coastlines relative to the central Arctic ocean. Potential ways of offering spatial forecast information based on the timescale over which the forecast signal beats the noise are also explored.

Investigating Climate at an Inland Sea During Snowball Earth

NASA Astrophysics Data System (ADS)

Campbell, A. J.; Bitz, C. M.; Warren, S. G.; Waddington, E. D.

2013-12-01

During the Neoproterozoic, the Earth's oceans may have been completely covered with thick ice, during periods commonly called Snowball Earth events. The Snowball Earth environment would seemingly have prohibited the survival of photosynthetic eukaryotic algae; however, these organisms were alive immediately prior to and immediate subsequent to these periods. Where on a Snowball Earth, or a Snowball-like exoplanet, could photosynthetic eukaryotic algae survive? Recent research, in attempt to reconcile this paradox, has demonstrated that narrow channels connected the ocean, called inland seas, could have provided refugia for photosynthetic eukaryotic algae during Snowball Earth events. Narrow channels could have restricted the flow of ocean-derived ice, called sea glaciers, diminishing sea-glacier penetration into these channels. Provided certain climate conditions and channel geometries, this diminished sea-glacier penetration would have allowed for either open water or thin sea ice, at the far end of these channels. A channel with open water or thin sea ice would provide the conditions needed for survival of photosynthetic eukaryotic algae. Here we test whether the climate needed to prevent sea-glacier penetration, could have existed in the special inland sea environment. Previous climate modeling of Snowball Earth has shown that tropical regions would have likely been warmer than the global average and would have experienced net sublimation at the surface. An inland sea located in the tropics would be surrounded by land that is bare and free from snow, while the inland sea itself would be either ice-covered or open water. With these conditions the inland sea would likely have a high albedo, while the surrounding bare land, would have a lower albedo. This albedo contrast could cause the climate over an inland sea to be warmer than the climate over the ice-covered ocean at the same latitude. We calculate the surface temperature and sublimation rate at an inland sea

Late Quaternary tephrostratigraphy of Baegdusan and Ulleung volcanoes using marine sediments in the Japan Sea/East Sea

NASA Astrophysics Data System (ADS)

Lim, Chungwan; Toyoda, Kazuhiro; Ikehara, Ken; Peate, David W.

2013-07-01

Only Ulleung and Baegdusan volcanoes have produced alkaline tephras in the Japan Sea/East Sea during the Quaternary. Little is known about their detailed tephrostratigraphy, except for the U-Oki and B-Tm tephras. Trace element analysis of bulk sediments can be used to identify alkaline cryptotephra because of the large compositional contrast. Five sediment cores spanning the interval between the rhyolitic AT (29.4 ka) and Aso-4 (87 ka) tephras were analyzed using an INAA scanning method. Source volcanoes for the five detected alkaline cryptotephra were identified from major element analyses of hand-picked glass shards: Ulleung (U-Ym, and the newly identified U-Sado), and Baegdusan (B-J, and the newly identified B-Sado and B-Ym). The eruption ages of the U-Ym, U-Sado, B-J, B-Sado, and B-Ym tephras are estimated to be 38 ka, 61 ka, 26 ka, 51 ka, 68-69 ka, and 86 ka, respectively, based on correlations with regional-scale TL (thinly laminated) layer stratigraphy (produced by basin-wide changes in bottom-water oxygen levels in response to millennium-scale paleoclimate variations). This study has allowed construction of an alkaline tephrostratigraphical framework for the late Quaternary linked to global environmental changes in the Japan Sea/East Sea, and improves our knowledge of the eruptive histories of Ulleung and Baegdusan volcanoes.

Subcellular distribution of trace elements in the liver of sea turtles.

PubMed

Anan, Yasumi; Kunito, Takashi; Sakai, Haruya; Tanabe, Shinsuke

2002-01-01

Subcellular distribution of Cu, Zn, Se, Rb, Mo, Ag, Cd and Pb was determined in the liver of green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) from Yaeyama Islands, Japan. Also, hepatic cytosol from sea turtles was applied on a Sephadex G-75 column and elution profiles of trace elements were examined. Copper, Zn, Se, Rb, Ag and Cd were largely present in cytosol in the liver of both species, indicating that cytosol was the significant site for the accumulation of these elements in sea turtles. In contrast, Mo and Pb were accumulated specifically in nuclear and mitochondrial fraction and microsomal fraction, respectively. Gel filtration analysis showed that Cu, Zn, Ag and Cd were bound to metallothionein (MT) in the cytosol of sea turtles. To our knowledge, this is the first report on the association of trace elements with MT in sea turtles.

Development of source specific diatom lipids biomarkers as Antarctic Sea Ice proxies

NASA Astrophysics Data System (ADS)

Smik, Lukas; Belt, Simon T.; Brown, Thomas A.; Lieser, Jan L.; Armand, Leanne K.; Leventer, Amy; Allen, Claire S.

2016-04-01

C25 highly branched isoprenoid (HBI) are lipid biomarkers biosynthesised by a relatively small number of diatom genera, but are, nonetheless, common constituents of global marine sediments. The occurrence and variable abundance of certain C25 highly branched isoprenoid (HBI) biomarkers in Antarctic marine sediments has previously been proposed as a proxy measure of paleo sea-ice extent in the Southern Ocean and a small number of paleo sea-ice reconstructions based on the variable abundances of these HBIs have appeared in recent years. However, the development of HBIs as proxies for Antarctic sea ice is much less advanced than that for IP25 (another HBI) in the Arctic and has been based on relatively small number of analyses in sea ice, water column and sediment samples. To provide further insights into the use of these HBIs as proxies for Antarctic sea ice, we here describe an assessment of their distributions in surface water, surface sediment and sea ice samples collected from a number of Antarctic locations experiencing contrasting sea ice conditions in recent years. Our study shows that distributions of a di-unsaturated HBI (diene II) and tri-unsaturated HBI (triene III) in surface water samples were found to be extremely sensitive to the local sea-ice conditions, with diene II detected for sampling sites that experienced seasonal sea ice and highest concentrations found in coastal locations with longer-lasting ice cover and a recurrent polynya. In contrast, triene III was observed in all of the samples analysed, but with highest concentrations within the region of the retreating sea ice edge, an observation consistent with significant environmental control over the biosynthesis of diene II and triene III by sea ice diatoms and open water phytoplankton, respectively. However, additional local factors, such as those associated with polynya formation, may also exert some control over the distribution of triene III and the relative concentrations of diene II and

Monitoring Arctic Sea ice using ERTS imagery. [Bering Sea, Beaufort Sea, Canadian Archipelago, and Greenland Sea

NASA Technical Reports Server (NTRS)

Barnes, J. C.; Bowley, C. J.

1974-01-01

Because of the effect of sea ice on the heat balance of the Arctic and because of the expanding economic interest in arctic oil and other minerals, extensive monitoring and further study of sea ice is required. The application of ERTS data for mapping ice is evaluated for several arctic areas, including the Bering Sea, the eastern Beaufort Sea, parts of the Canadian Archipelago, and the Greenland Sea. Interpretive techniques are discussed, and the scales and types of ice features that can be detected are described. For the Bering Sea, a sample of ERTS imagery is compared with visual ice reports and aerial photography from the NASA CV-990 aircraft.

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

PubMed

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

2012-01-01

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

Seismic stratigraphic interpretations suggest that sectors of the central and western Ross Sea were near or above sea level during earliest Oligocene time

NASA Astrophysics Data System (ADS)

Sorlien, C. C.; Sauli, C.; De Santis, L.; Luyendyk, B. P.; Wardell, N.; Davis, S. M.; Wilson, D. S.; Brazell, S.; Bartek, L., III; Bart, P. J.

2016-12-01

Most of West Antarctica has been interpreted as a high-elevation plateau that has subsided between about 100 Ma and present. Ross Sea was characterized by subaerial ridges and islands up to mid-Cenozoic time. It was in such an environment that Oligocene ice sheets and glaciers advanced and retreated within Ross Embayment. The extent to which Oligocene ice affected the embayment north of the current ice shelf has not been established, with either ice caps on islands, or broad glaciers affecting basins having been proposed. We used all available data from the Seismic Data Library System to interpret stratigraphic horizons through most of Ross Sea. A new 3D velocity model was constructed for the western 2/3 of Ross Sea. Stratigraphic age control was provided by deep scientific coring, including Deep Sea Drilling Program sites, the Cape Roberts Drilling Program, and published correlations to ANDRILL sites. The correlation with recent drill records and much additional seismic reflection data allowed a new interpretation of Ross Sea, which differs from the previous comprehensive seismic stratigraphic interpretation (ANTOSTRAT 1995). Sedimentary rocks of given ages are twice as deep within Terror Rift in westernmost Ross Sea in our interpretation. In contrast, acoustic basement is 1 km shallower in part of Central Trough. The 200 km-wide smooth acoustic basement on Central High eroded sub-aerially until it subsided differentially through sea level toward the centers of Cretaceous and Cenozoic rifts. If the subsiding basins were kept filled with sediment eroded by Oligocene ice sheets, then the age the strata aggrading above the planar rock platform date subsidence through sea level at each location. Using such an assumption, much of central and western Ross Sea was near or above sea level during earliest Oligocene time. These assumptions will be tested by backstripping and thermal subsidence models.

Trends in the Length of the Southern Ocean Sea Ice Season: 1979-1999

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

Satellite data can be used to observe the sea ice distribution around the continent of Antarctica on a daily basis and hence to determine how many days a year have sea ice at each location. This has been done for each of the 21 years 1979-1999. Mapping the trends in these data over the 21-year period reveals a detailed pattern of changes in the length of the sea ice season around Antarctica. Most of the Ross Sea ice cover has undergone a lengthening of the sea ice season, whereas most of the Amundsen Sea ice cover and almost the entire Bellingshausen Sea ice cover have undergone a shortening of the sea ice season. Results around the rest of the continent, including in the Weddell Sea, are more mixed, but overall, more of the Southern Ocean experienced a lengthening of the sea ice season than a shortening. For instance, the area experiencing a lengthening of the sea ice season by at least 1 day per year is 5.8 x 10(exp 6) sq km, whereas the area experiencing a shortening of the sea ice season by at least 1 day per year is less than half that, at 2.8 x 10(exp 6) sq km. This contrasts sharply with what is happened over the same period in the Arctic, where, overall, there has been some depletion of the ice cover, including shortened sea ice seasons and decreased ice extents.

On Sea Ice Characterisation By Multi-Frequency SAR

NASA Astrophysics Data System (ADS)

Grahn, Jakob; Brekke, Camilla; Eltoft, Torbjorn; Holt, Benjamin

2013-12-01

By means of polarimetric target decomposition, quad-pol SAR data of sea ice is analysed at two frequency bands. In particular, the non negative eigenvalue decomposition (NNED) is applied on L- and C-band NASA/JPL AIR- SAR data acquired over the Beaufort sea in 2004. The de- composition separates the scattered radar signal into three types, dominated by double, volume and single bounce scattering respectively. Using ground truth derived from RADARSAT-1 and meteorological data, we investigate how the different frequency bands compare in terms of these scattering types. The ground truth contains multi year ice and three types of first year ice of different age and thickness. We find that C-band yields a higher scattered intensity in most ice and scattering types, as well as a more homogeneous intensity. L-band on the other hand yields more pronounced deformation features, such as ridges. The mean intensity contrast between the two thinnest ice types is highest in the double scattering component of C- band, although the contrast of the total signal is greater in L-band. This may indicate that the choice of polarimetric parameters is important for discriminating thin ice types.

Phytoplankton of the North Sea and its dynamics: A review

NASA Astrophysics Data System (ADS)

Reid, P. C.; Lancelot, C.; Gieskes, W. W. C.; Hagmeier, E.; Weichart, G.

Phytoplankton is the major contributor to algal biomass and primary production of the North Sea, although crops of macroalgae can locally be up to 2000 g C.m -2 along the coast of the U.K. and Norway, and microphytobenthos dominates production in the shallow tidal flat areas bordering the coasts of England, the Netherlands, Germany and Denmark. Data collected since 1932 during the Continuous Plankton Recorder Survey show consistent patterns of geographical, seasonal and annual variation in the distribution of phytoplankton and its major taxonomic components. There is a trend of increased colouration in Recorder silks in the southern North Sea until approximately 1975 since when Colour levels (assumed to be indicative of algal biomass) have declined. In the eutrophic Dutch Wadden Sea the algal crop continued to increase; in Dutch coastal North Sea waters a trend of biomass increase reversed since 1984, apparently due to a reduction in Rhine river outflow. Long-term observations made at Helgoland since the 60's also show trends of increasing nutrients and phytoplankton biomass only to 1984. Adverse effects such as deoxygenation, foam formation and toxin production have been linked to mass concentrations of algae known as blooms. There is no evidence from existing reports for an increase in their frequency, although some years stand out with larger numbers. Occurrence of blooms can partly be explained by hydrographic conditions. More than 30 taxa are recognised as occurring in bloom proportions in the North Sea, approximately one third of which can be toxic. The crop of Bacillariophyceae (diatoms) is not likely to increase with eutrophication due to silicate limitation. An extensive subsurface maximum of armoured dinoflagellates, its abundance gouverned by hydrographic conditions, is the most characteristic feature of the central and northern North Sea in the summer months. Abundance, sometimes dominance, of picoplankton and of species that are not readily detected by

Comparison of Deep-Water Viromes from the Atlantic Ocean and the Mediterranean Sea

PubMed Central

Winter, Christian; Garcia, Juan A. L.; Weinbauer, Markus G.; DuBow, Michael S.; Herndl, Gerhard J.

2014-01-01

The aim of this study was to compare the composition of two deep-sea viral communities obtained from the Romanche Fracture Zone in the Atlantic Ocean (collected at 5200 m depth) and the southwest Mediterranean Sea (from 2400 m depth) using a pyro-sequencing approach. The results are based on 18.7% and 6.9% of the sequences obtained from the Atlantic Ocean and the Mediterranean Sea, respectively, with hits to genomes in the non-redundant viral RefSeq database. The identifiable richness and relative abundance in both viromes were dominated by archaeal and bacterial viruses accounting for 92.3% of the relative abundance in the Atlantic Ocean and for 83.6% in the Mediterranean Sea. Despite characteristic differences in hydrographic features between the sampling sites in the Atlantic Ocean and the Mediterranean Sea, 440 virus genomes were found in both viromes. An additional 431 virus genomes were identified in the Atlantic Ocean and 75 virus genomes were only found in the Mediterranean Sea. The results indicate that the rather contrasting deep-sea environments of the Atlantic Ocean and the Mediterranean Sea share a common core set of virus types constituting the majority of both virus communities in terms of relative abundance (Atlantic Ocean: 81.4%; Mediterranean Sea: 88.7%). PMID:24959907

Temporal and spatial variations of sea surface temperature in the East China Sea

NASA Astrophysics Data System (ADS)

Tseng, Chente; Lin, Chiyuan; Chen, Shihchin; Shyu, Chungzen

2000-03-01

Sea surface temperature of the East China Sea (ECS) were analyzed using the NOAA/AVHRR SST images. These satellite images reveal surface features of ECS including mainly the Kuroshio Current, Kuroshio Branch Current, Taiwan Warm Current, China coastal water, Changjiang diluted water and Yellow Sea mixed cold water. The SST of ECS ranges from 27 to 29°C in summer; some cold eddies were found off northeast Taiwan and to the south of Changjiang mouth. SST anomalies at the center of these eddies were about 2-5°C. The strongest front usually occurs in May each year and its temperature gradient is about 5-6°C over a cross-shelf distance of 30 nautical miles. The Yellow Sea mixed cold water also provides a contrast from China Coastal waters shoreward of the 50 m isobath; cross-shore temperature gradient is about 6-8°C over 30 nautical miles. The Kuroshio intrudes into ECS preferably at two locations. The first is off northeast Taiwan; the subsurface water of Kuroshio is upwelled onto the shelf while the main current is deflected seaward. The second site is located at 31°N and 128°E, which is generally considered as the origin of the Tsushima Warm Current. More quantitatively, a 2-year time series of monthly SST images is examined using EOF analysis to determine the spatial and temporal variations in the northwestern portion of ECS. The first spatial EOF mode accounts for 47.4% of total spatial variance and reveals the Changjiang plume and coastal cold waters off China. The second and third EOF modes account for 16.4 and 9.6% of total variance, respectively, and their eigenvector images show the intrusion of Yellow Sea mixed cold waters and the China coastal water. The fourth EOF mode accounts for 5.4% of total variance and reveals cold eddies around Chusan Islands. The temporal variance EOF analysis is less revealing in this study area.

Expression pattern of three-finger toxin and phospholipase A2 genes in the venom glands of two sea snakes, Lapemis curtus and Acalyptophis peronii: comparison of evolution of these toxins in land snakes, sea kraits and sea snakes.

PubMed

Pahari, Susanta; Bickford, David; Fry, Bryan G; Kini, R Manjunatha

2007-09-27

Snake venom composition varies widely both among closely related species and within the same species, based on ecological variables. In terrestrial snakes, such variation has been proposed to be due to snakes' diet. Land snakes target various prey species including insects (arthropods), lizards (reptiles), frogs and toads (amphibians), birds (aves), and rodents (mammals), whereas sea snakes target a single vertebrate class (fishes) and often specialize on specific types of fish. It is therefore interesting to examine the evolution of toxins in sea snake venoms compared to that of land snakes. Here we describe the expression of toxin genes in the venom glands of two sea snakes, Lapemis curtus (Spine-bellied Sea Snake) and Acalyptophis peronii (Horned Sea Snake), two members of a large adaptive radiation which occupy very different ecological niches. We constructed cDNA libraries from their venom glands and sequenced 214 and 192 clones, respectively. Our data show that despite their explosive evolutionary radiation, there is very little variability in the three-finger toxin (3FTx) as well as the phospholipase A2 (PLA2) enzymes, the two main constituents of Lapemis curtus and Acalyptophis peronii venom. To understand the evolutionary trends among land snakes, sea snakes and sea kraits, pairwise genetic distances (intraspecific and interspecific) of 3FTx and PLA2 sequences were calculated. Results show that these proteins appear to be highly conserved in sea snakes in contrast to land snakes or sea kraits, despite their extremely divergent and adaptive ecological radiation. Based on these results, we suggest that streamlining in habitat and diet in sea snakes has possibly kept their toxin genes conserved, suggesting the idea that prey composition and diet breadth may contribute to the diversity and evolution of venom components.

Expression pattern of three-finger toxin and phospholipase A2 genes in the venom glands of two sea snakes, Lapemis curtus and Acalyptophis peronii: comparison of evolution of these toxins in land snakes, sea kraits and sea snakes

PubMed Central

Pahari, Susanta; Bickford, David; Fry, Bryan G; Kini, R Manjunatha

2007-01-01

Background Snake venom composition varies widely both among closely related species and within the same species, based on ecological variables. In terrestrial snakes, such variation has been proposed to be due to snakes' diet. Land snakes target various prey species including insects (arthropods), lizards (reptiles), frogs and toads (amphibians), birds (aves), and rodents (mammals), whereas sea snakes target a single vertebrate class (fishes) and often specialize on specific types of fish. It is therefore interesting to examine the evolution of toxins in sea snake venoms compared to that of land snakes. Results Here we describe the expression of toxin genes in the venom glands of two sea snakes, Lapemis curtus (Spine-bellied Sea Snake) and Acalyptophis peronii (Horned Sea Snake), two members of a large adaptive radiation which occupy very different ecological niches. We constructed cDNA libraries from their venom glands and sequenced 214 and 192 clones, respectively. Our data show that despite their explosive evolutionary radiation, there is very little variability in the three-finger toxin (3FTx) as well as the phospholipase A2 (PLA2) enzymes, the two main constituents of Lapemis curtus and Acalyptophis peronii venom. To understand the evolutionary trends among land snakes, sea snakes and sea kraits, pairwise genetic distances (intraspecific and interspecific) of 3FTx and PLA2 sequences were calculated. Results show that these proteins appear to be highly conserved in sea snakes in contrast to land snakes or sea kraits, despite their extremely divergent and adaptive ecological radiation. Conclusion Based on these results, we suggest that streamlining in habitat and diet in sea snakes has possibly kept their toxin genes conserved, suggesting the idea that prey composition and diet breadth may contribute to the diversity and evolution of venom components. PMID:17900344

Retrieval of chlorophyll from remote-sensing reflectance in the china seas.

PubMed

He, M X; Liu, Z S; Du, K P; Li, L P; Chen, R; Carder, K L; Lee, Z P

2000-05-20

The East China Sea is a typical case 2 water environment, where concentrations of phytoplankton pigments, suspended matter, and chromophoric dissolved organic matter (CDOM) are all higher than those in the open oceans, because of the discharge from the Yangtze River and the Yellow River. By using a hyperspectral semianalytical model, we simulated a set of remote-sensing reflectance for a variety of chlorophyll, suspended matter, and CDOM concentrations. From this simulated data set, a new algorithm for the retrieval of chlorophyll concentration from remote-sensing reflectance is proposed. For this method, we took into account the 682-nm spectral channel in addition to the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) channels. When this algorithm was applied to a field data set, the chlorophyll concentrations retrieved through the new algorithm were consistent with field measurements to within a small error of 18%, in contrast with that of 147% between the SeaWiFS ocean chlorophyll 2 algorithm and the in situ observation.

Contrasting Holocene sedimentary geologies of lower Daly River, northern Australia, and lower Sepik-Ramu, Papua New Guinea

NASA Astrophysics Data System (ADS)

Chappell, John

1993-03-01

The estuarine plain of the macrotidal Daly River, in monsoonal northern Australia, is underlain by extensive mid-Holocene mangrove swamp sediments which accumulated during the last stages of Post-glacial sea-level rise. Sediment yield from the catchment is too low to account for the volume which accumulated during sea-level rise, and onshore transport is invoked. This is supported by radiocarbon ages and facies analysis of the transgressive sediment tract beneath the maximum flooding surface (MFS), and of the tract of vertical sedimentation which extends from the MFS to the surface of estuarine/fluvial transition (the EFT). The EFT occurred about 5000 to 6000 BP throughout the estuarine plain. A contrasting situation exists in the lowland Holocene basin of the microtidal Sepik and Ramu rivers in Papua New Guinea, which derive sediment from highly tectonic catchments. A tectonic basin, which was a shallow brackish inland sea after Post-glacial transgression, is separated by a low divide from a deltaic plain. Progradation of the deltaic plain commenced about 3500 BP after regressive sedimentation eclipsed the inland sea in the tectonic basin. Contrasting organic facies, mangrove in the Daly and freshwater swamp deposits in the Sepik-Ramu, highlight differences between facies models of the two systems. Differences between fluvio-tidal regimes are reflected by the EFT, which is synchronous in the Daly and diachronous in the Sepik-Ramu, and possibly by the MFS which is diachronous in the Daly and may be synchronous in the Sepik-Ramu.

Unique system of photoreceptors in sea urchin tube feet

PubMed Central

Ullrich-Lüter, Esther M; Dupont, Sam; Arboleda, Enrique; Hausen, Harald; Arnone, Maria Ina

2011-01-01

Different sea urchin species show a vast variety of responses to variations in light intensity; however, despite this behavioral evidence for photosensitivity, light sensing in these animals has remained an enigma. Genome information of the recently sequenced purple sea urchin (Strongylocentrotus purpuratus) allowed us to address this question from a previously unexplored molecular perspective by localizing expression of the rhabdomeric opsin Sp-opsin4 and Sp-pax6, two genes essential for photoreceptor function and development, respectively. Using a specifically designed antibody against Sp-Opsin4 and in situ hybridization for both genes, we detected expression in two distinct groups of photoreceptor cells (PRCs) located in the animal's numerous tube feet. Specific reactivity of the Sp-Opsin4 antibody with sea star optic cushions, which regulate phototaxis, suggests a similar visual function in sea urchins. Ultrastructural characterization of the sea urchin PRCs revealed them to be of a microvillar receptor type. Our data suggest that echinoderms, in contrast to chordates, deploy a microvillar, r-opsin–expressing PRC type for vision, a feature that has been so far documented only in protostome animals. Surprisingly, sea urchin PRCs lack any associated screening pigment. Indeed, one of the tube foot PRC clusters may account for directional vision by being shaded through the opaque calcite skeleton. The PRC axons connect to the animal internal nervous system, suggesting an integrative function beyond local short circuits. Because juveniles display no phototaxis until skeleton completion, we suggest a model in which the entire sea urchin, deploying its skeleton as PRC screening device, functions as a huge compound eye. PMID:21536888

Variability of sea salts in ice and firn cores from Fimbul Ice Shelf, Dronning Maud Land, Antarctica

NASA Astrophysics Data System (ADS)

Paulina Vega, Carmen; Isaksson, Elisabeth; Schlosser, Elisabeth; Divine, Dmitry; Martma, Tõnu; Mulvaney, Robert; Eichler, Anja; Schwikowski-Gigar, Margit

2018-05-01

Major ions were analysed in firn and ice cores located at Fimbul Ice Shelf (FIS), Dronning Maud Land - DML, Antarctica. FIS is the largest ice shelf in the Haakon VII Sea, with an extent of approximately 36 500 km2. Three shallow firn cores (about 20 m deep) were retrieved in different ice rises, Kupol Ciolkovskogo (KC), Kupol Moskovskij (KM), and Blåskimen Island (BI), while a 100 m long core (S100) was drilled near the FIS edge. These sites are distributed over the entire FIS area so that they provide a variety of elevation (50-400 m a.s.l.) and distance (3-42 km) to the sea. Sea-salt species (mainly Na+ and Cl-) generally dominate the precipitation chemistry in the study region. We associate a significant sixfold increase in median sea-salt concentrations, observed in the S100 core after the 1950s, to an enhanced exposure of the S100 site to primary sea-salt aerosol due to a shorter distance from the S100 site to the ice front, and to enhanced sea-salt aerosol production from blowing salty snow over sea ice, most likely related to the calving of Trolltunga occurred during the 1960s. This increase in sea-salt concentrations is synchronous with a shift in non-sea-salt sulfate (nssSO42-) toward negative values, suggesting a possible contribution of fractionated aerosol to the sea-salt load in the S100 core most likely originating from salty snow found on sea ice. In contrast, there is no evidence of a significant contribution of fractionated sea salt to the ice-rises sites, where the signal would be most likely masked by the large inputs of biogenic sulfate estimated for these sites. In summary, these results suggest that the S100 core contains a sea-salt record dominated by the proximity of the site to the ocean, and processes of sea ice formation in the neighbouring waters. In contrast, the ice-rises firn cores register a larger-scale signal of atmospheric flow conditions and a less efficient transport of sea-salt aerosols to these sites. These findings are a

Aral Sea basin: a sea dies, a sea also rises.

PubMed

Glantz, Michael H

2007-06-01

The thesis of this article is quite different from many other theses of papers, books, and articles on the Aral Sea. It is meant to purposely highlight the reality of the situation in Central Asia: the Aral Sea that was once a thriving body of water is no more. That sea is dead. What does exist in its place are the Aral seas: there are in essence three bodies of water, one of which is being purposefully restored and its level is rising (the Little Aral), and two others which are still marginally connected, although they continue to decline in level (the Big Aral West and the Big Aral East). In 1960 the level of the sea was about 53 m above sea level. By 2006 the level had dropped by 23 m to 30 m above sea level. This was not a scenario generated by a computer model. It was a process of environmental degradation played out in real life in a matter of a few decades, primarily as a result of human activities. Despite wishes and words to the contrary, it will take a heroic global effort to save what remains of the Big Aral. It would also take a significant degree of sacrifice by people and governments in the region to restore the Big Aral to an acceptable level, given that the annual rate of flow reaching the Amudarya River delta is less than a 10th of what it was several decades ago. Conferring World Heritage status to the Aral Sea(s) could spark restoration efforts for the Big Aral.

Measurement of spectral sea ice albedo at Qaanaaq fjord in northwest Greenland

NASA Astrophysics Data System (ADS)

Tanikawa, T.

2017-12-01

The spectral albedos of sea ice were measured at Qaanaaq fjord in northwest Greenland. Spectral measurements were conducted for sea ice covered with snow and sea ice without snow where snow was artificially removed around measurement point. Thickness of the sea ice was approximately 1.3 m with 5 cm of snow over the sea ice. The measurements show that the spectral albedos of the sea ice with snow were lower than those of natural pure snow especially in the visible regions though the spectral shapes were similar to each other. This is because the spectral albedos in the visible region have information of not only the snow but also the sea ice under the snow. The spectral albedos of the sea ice without the snow were approximately 0.4 - 0.5 in the visible region, 0.05-0.25 in the near-infrared region and almost constant of approximately 0.05 in the region of 1500 - 2500 nm. In the visible region, it would be due to multiple scattering by an air bubble within the sea ice. In contrast, in the near-infrared and shortwave infrared wavelengths, surface reflection at the sea ice surface would be dominant. Since a light absorption by the ice in these regions is relatively strong comparing to the visible region, the light could not be penetrated deeply within the sea ice, resulting that surface reflection based on Fresnel reflection would be dominant. In this presentation we also show the results of comparison between the radiative transfer calculation and spectral measurement data.

Genetic profiling links changing sea-ice to shifting beluga whale migration patterns

PubMed Central

Mahoney, Andrew R.; Suydam, Robert; Quakenbush, Lori; Whiting, Alex; Lowry, Lloyd; Harwood, Lois

2016-01-01

There is increasing concern over how Arctic fauna will adapt to climate related changes in sea-ice. We used long-term sighting and genetic data on beluga whales (Delphinapterus leucas) in conjunction with multi-decadal patterns of sea-ice in the Pacific Arctic to investigate the influence of sea-ice on spring migration and summer residency patterns. Substantial variations in sea-ice conditions were detected across seasons, years and sub-regions, revealing ice–ocean dynamics more complex than Arctic-wide trends suggest. This variation contrasted with a highly consistent pattern of migration and residency by several populations, indicating that belugas can accommodate widely varying sea-ice conditions to perpetuate philopatry to coastal migration destinations. However, a number of anomalous migration and residency events were detected and coincided with anomalous ice years, and in one case with an increase in killer whale (Orcinus orca) sightings and reported predation on beluga whales. The behavioural shifts were likely driven by changing sea-ice and associated changes in resource dispersion and predation risk. Continued reductions in sea-ice may result in increased predation at key aggregation areas and shifts in beluga whale behaviour with implications for population viability, ecosystem structure and the subsistence cultures that rely on them.

Rapid changes in surface water carbonate chemistry during Antarctic sea ice melt

NASA Astrophysics Data System (ADS)

Jones, Elizabeth M.; Bakker, Dorothee C. E.; Venables, Hugh J.; Whitehouse, Michael J.; Korb, Rebecca E.; Watson, Andrew J.

2010-11-01

ABSTRACT The effect of sea ice melt on the carbonate chemistry of surface waters in the Weddell-Scotia Confluence, Southern Ocean, was investigated during January 2008. Contrasting concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA) and the fugacity of carbon dioxide (fCO2) were observed in and around the receding sea ice edge. The precipitation of carbonate minerals such as ikaite (CaCO3.6H2O) in sea ice brine has the net effect of decreasing DIC and TA and increasing the fCO2 in the brine. Deficits in DIC up to 12 +/- 3 μmol kg-1 in the marginal ice zone (MIZ) were consistent with the release of DIC-poor brines to surface waters during sea ice melt. Biological utilization of carbon was the dominant processes and accounted for 41 +/- 1 μmol kg-1 of the summer DIC deficit. The data suggest that the combined effects of biological carbon uptake and the precipitation of carbonates created substantial undersaturation in fCO2 of 95 μatm in the MIZ during summer sea ice melt. Further work is required to improve the understanding of ikaite chemistry in Antarctic sea ice and its importance for the sea ice carbon pump.

First glimpse into Lower Jurassic deep-sea biodiversity: in situ diversification and resilience against extinction

PubMed Central

Thuy, Ben; Kiel, Steffen; Dulai, Alfréd; Gale, Andy S.; Kroh, Andreas; Lord, Alan R.; Numberger-Thuy, Lea D.; Stöhr, Sabine; Wisshak, Max

2014-01-01

Owing to the assumed lack of deep-sea macrofossils older than the Late Cretaceous, very little is known about the geological history of deep-sea communities, and most inference-based hypotheses argue for repeated recolonizations of the deep sea from shelf habitats following major palaeoceanographic perturbations. We present a fossil deep-sea assemblage of echinoderms, gastropods, brachiopods and ostracods, from the Early Jurassic of the Glasenbach Gorge, Austria, which includes the oldest known representatives of a number of extant deep-sea groups, and thus implies that in situ diversification, in contrast to immigration from shelf habitats, played a much greater role in shaping modern deep-sea biodiversity than previously thought. A comparison with coeval shelf assemblages reveals that, at least in some of the analysed groups, significantly more extant families/superfamilies have endured in the deep sea since the Early Jurassic than in the shelf seas, which suggests that deep-sea biota are more resilient against extinction than shallow-water ones. In addition, a number of extant deep-sea families/superfamilies found in the Glasenbach assemblage lack post-Jurassic shelf occurrences, implying that if there was a complete extinction of the deep-sea fauna followed by replacement from the shelf, it must have happened before the Late Jurassic. PMID:24850917

Observational analysis of air-sea fluxes and sea water temperature offshore South China Sea

NASA Astrophysics Data System (ADS)

Bi, X.; Huang, J.; Gao, Z.; Liu, Y.

2017-12-01

This paper investigates the air-sea fluxes (momentum flux, sensible heat flux and latent heat flux) from eddy covariance method based on data collected at an offshore observation tower in the South China Sea from January 2009 to December 2016 and sea water temperature (SWT) on six different levels based on data collected from November 2011 to June 2013. The depth of water at the tower over the sea averages about 15 m. This study presents the in-situ measurements of continuous air-sea fluxes and SWT at different depths. Seasonal and diurnal variations in air-sea fluxes and SWT on different depths are examined. Results show that air-sea fluxes and all SWT changed seasonally; sea-land breeze circulation appears all the year round. Unlike winters where SWT on different depths are fairly consistent, the difference between sea surface temperature (SST) and sea temperature at 10 m water depth fluctuates dramatically and the maximum value reaches 7 °C during summer.

Mangrove sedimentation and response to relative sea-level rise

USGS Publications Warehouse

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

2016-01-01

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

Trophic interactions within the Ross Sea continental shelf ecosystem

PubMed Central

Smith, Walker O; Ainley, David G; Cattaneo-Vietti, Riccardo

2006-01-01

The continental shelf of the Ross Sea is one of the Antarctic's most intensively studied regions. We review the available data on the region's physical characteristics (currents and ice concentrations) and their spatial variations, as well as components of the neritic food web, including lower and middle levels (phytoplankton, zooplankton, krill, fishes), the upper trophic levels (seals, penguins, pelagic birds, whales) and benthic fauna. A hypothetical food web is presented. Biotic interactions, such as the role of Euphausia crystallorophias and Pleuragramma antarcticum as grazers of lower levels and food for higher trophic levels, are suggested as being critical. The neritic food web contrasts dramatically with others in the Antarctic that appear to be structured around the keystone species Euphausia superba. Similarly, we suggest that benthic–pelagic coupling is stronger in the Ross Sea than in most other Antarctic regions. We also highlight many of the unknowns within the food web, and discuss the impacts of a changing Ross Sea habitat on the ecosystem. PMID:17405209

Large-scale control of the Arabian Sea monsoon inversion in August

NASA Astrophysics Data System (ADS)

Wu, Chi-Hua; Wang, S.-Y. Simon; Hsu, Huang-Hsiung

2017-12-01

The summer monsoon inversion in the Arabian Sea is characterized by a large amount of low clouds and August as the peak season. Atmospheric stratification associated with the monsoon inversion has been considered a local system influenced by the advancement of the India-Pakistan monsoon. Empirical and numerical evidence from this study suggests that the Arabian Sea monsoon inversion is linked to a broader-scale monsoon evolution across the African Sahel, South Asia, and East Asia-Western North Pacific (WNP), rather than being a mere byproduct of the India-Pakistan monsoon progression. In August, the upper-tropospheric anticyclone in South Asia extends sideways corresponding with the enhanced precipitation in the subtropical WNP, equatorial Indian Ocean, and African Sahel while the middle part of this anticyclone weakens over the Arabian Sea. The increased heating in the adjacent monsoon systems creates a suppression effect on the Arabian Sea, suggesting an apparent competition among the Africa-Asia-WNP monsoon subsystems. The peak Sahel rainfall in August, together with enhanced heating in the equatorial Indian Ocean, produces a critical effect on strengthening the Arabian Sea thermal inversion. By contrast, the WNP monsoon onset which signifies the eastward expansion of the subtropical Asian monsoon heating might play a secondary or opposite role in the Arabian Sea monsoon inversion.

Loss of connectivity among island-dwelling Peary caribou following sea ice decline.

PubMed

Jenkins, Deborah A; Lecomte, Nicolas; Schaefer, James A; Olsen, Steffen M; Swingedouw, Didier; Côté, Steeve D; Pellissier, Loïc; Yannic, Glenn

2016-09-01

Global warming threatens to reduce population connectivity for terrestrial wildlife through significant and rapid changes to sea ice. Using genetic fingerprinting, we contrasted extant connectivity in island-dwelling Peary caribou in northern Canada with continental-migratory caribou. We next examined if sea-ice contractions in the last decades modulated population connectivity and explored the possible impact of future climate change on long-term connectivity among island caribou. We found a strong correlation between genetic and geodesic distances for both continental and Peary caribou, even after accounting for the possible effect of sea surface. Sea ice has thus been an effective corridor for Peary caribou, promoting inter-island connectivity and population mixing. Using a time series of remote sensing sea-ice data, we show that landscape resistance in the Canadian Arctic Archipelago has increased by approximately 15% since 1979 and may further increase by 20-77% by 2086 under a high-emission scenario (RCP8.5). Under the persistent increase in greenhouse gas concentrations, reduced connectivity may isolate island-dwelling caribou with potentially significant consequences for population viability. © 2016 The Author(s).

Variability in sea ice cover and climate elicit sex specific responses in an Antarctic predator

PubMed Central

Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D.; Massom, Rob A.; Reid, Phillip; Hobbs, William; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Authier, Matthieu; Bailleul, Frédéric; Hindell, Mark A.; Charrassin, Jean-Benoit

2017-01-01

Contrasting regional changes in Southern Ocean sea ice have occurred over the last 30 years with distinct regional effects on ecosystem structure and function. Quantifying how Antarctic predators respond to such changes provides the context for predicting how climate variability/change will affect these assemblages into the future. Over an 11-year time-series, we examine how inter-annual variability in sea ice concentration and advance affect the foraging behaviour of a top Antarctic predator, the southern elephant seal. Females foraged longer in pack ice in years with greatest sea ice concentration and earliest sea ice advance, while males foraged longer in polynyas in years of lowest sea ice concentration. There was a positive relationship between near-surface meridional wind anomalies and female foraging effort, but not for males. This study reveals the complexities of foraging responses to climate forcing by a poleward migratory predator through varying sea ice property and dynamic anomalies. PMID:28233791

Variability in sea ice cover and climate elicit sex specific responses in an Antarctic predator.

PubMed

Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D; Massom, Rob A; Reid, Phillip; Hobbs, William; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Authier, Matthieu; Bailleul, Frédéric; Hindell, Mark A; Charrassin, Jean-Benoit

2017-02-24

Contrasting regional changes in Southern Ocean sea ice have occurred over the last 30 years with distinct regional effects on ecosystem structure and function. Quantifying how Antarctic predators respond to such changes provides the context for predicting how climate variability/change will affect these assemblages into the future. Over an 11-year time-series, we examine how inter-annual variability in sea ice concentration and advance affect the foraging behaviour of a top Antarctic predator, the southern elephant seal. Females foraged longer in pack ice in years with greatest sea ice concentration and earliest sea ice advance, while males foraged longer in polynyas in years of lowest sea ice concentration. There was a positive relationship between near-surface meridional wind anomalies and female foraging effort, but not for males. This study reveals the complexities of foraging responses to climate forcing by a poleward migratory predator through varying sea ice property and dynamic anomalies.

Evidence for link between modelled trends in Antarctic sea ice and underestimated westerly wind changes

PubMed Central

Purich, Ariaan; Cai, Wenju; England, Matthew H.; Cowan, Tim

2016-01-01

Despite global warming, total Antarctic sea ice coverage increased over 1979–2013. However, the majority of Coupled Model Intercomparison Project phase 5 models simulate a decline. Mechanisms causing this discrepancy have so far remained elusive. Here we show that weaker trends in the intensification of the Southern Hemisphere westerly wind jet simulated by the models may contribute to this disparity. During austral summer, a strengthened jet leads to increased upwelling of cooler subsurface water and strengthened equatorward transport, conducive to increased sea ice. As the majority of models underestimate summer jet trends, this cooling process is underestimated compared with observations and is insufficient to offset warming in the models. Through the sea ice-albedo feedback, models produce a high-latitude surface ocean warming and sea ice decline, contrasting the observed net cooling and sea ice increase. A realistic simulation of observed wind changes may be crucial for reproducing the recent observed sea ice increase. PMID:26842498

Evidence for link between modelled trends in Antarctic sea ice and underestimated westerly wind changes.

PubMed

Purich, Ariaan; Cai, Wenju; England, Matthew H; Cowan, Tim

2016-02-04

Despite global warming, total Antarctic sea ice coverage increased over 1979-2013. However, the majority of Coupled Model Intercomparison Project phase 5 models simulate a decline. Mechanisms causing this discrepancy have so far remained elusive. Here we show that weaker trends in the intensification of the Southern Hemisphere westerly wind jet simulated by the models may contribute to this disparity. During austral summer, a strengthened jet leads to increased upwelling of cooler subsurface water and strengthened equatorward transport, conducive to increased sea ice. As the majority of models underestimate summer jet trends, this cooling process is underestimated compared with observations and is insufficient to offset warming in the models. Through the sea ice-albedo feedback, models produce a high-latitude surface ocean warming and sea ice decline, contrasting the observed net cooling and sea ice increase. A realistic simulation of observed wind changes may be crucial for reproducing the recent observed sea ice increase.

Low Carbon sink capacity of Red Sea mangroves.

PubMed

Almahasheer, Hanan; Serrano, Oscar; Duarte, Carlos M; Arias-Ortiz, Ariane; Masque, Pere; Irigoien, Xabier

2017-08-29

Mangroves forests of Avicennia marina occupy about 135 km 2 in the Red Sea and represent one of the most important vegetated communities in this otherwise arid and oligotrophic region. We assessed the soil organic carbon (C org ) stocks, soil accretion rates (SAR; mm y -1 ) and soil C org sequestration rates (g C org m -2 yr -1 ) in 10 mangrove sites within four locations along the Saudi coast of the Central Red Sea. Soil C org density and stock in Red Sea mangroves were among the lowest reported globally, with an average of 4 ± 0.3 mg C org cm -3 and 43 ± 5 Mg C org ha -1 (in 1 m-thick soils), respectively. Sequestration rates of C org , estimated at 3 ± 1 and 15 ± 1 g C org m -2 yr -1 for the long (millennia) and short (last century) temporal scales, respectively, were also relatively low compared to mangrove habitats from more humid bioregions. In contrast, the accretion rates of Central Red Sea mangroves soils were within the range reported for global mangrove forests. The relatively low C org sink capacity of Red Sea mangroves could be due to the extreme environmental conditions such as low rainfall, nutrient limitation and high temperature, reducing the growth rates of the mangroves and increasing soil respiration rates.

Genome size variation in deep-sea amphipods

PubMed Central

Jamieson, A. J.; Piertney, S. B.

2017-01-01

Genome size varies considerably across taxa, and extensive research effort has gone into understanding whether variation can be explained by differences in key ecological and life-history traits among species. The extreme environmental conditions that characterize the deep sea have been hypothesized to promote large genome sizes in eukaryotes. Here we test this supposition by examining genome sizes among 13 species of deep-sea amphipods from the Mariana, Kermadec and New Hebrides trenches. Genome sizes were estimated using flow cytometry and found to vary nine-fold, ranging from 4.06 pg (4.04 Gb) in Paralicella caperesca to 34.79 pg (34.02 Gb) in Alicella gigantea. Phylogenetic independent contrast analysis identified a relationship between genome size and maximum body size, though this was largely driven by those species that display size gigantism. There was a distinct shift in the genome size trait diversification rate in the supergiant amphipod A. gigantea relative to the rest of the group. The variation in genome size observed is striking and argues against genome size being driven by a common evolutionary history, ecological niche and life-history strategy in deep-sea amphipods. PMID:28989783

Sea level and turbidity controls on mangrove soil surface elevation change

USGS Publications Warehouse

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

2015-01-01

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

Distinct characteristics of the intermediate water observed off the east coast of Korea during two contrasting years

NASA Astrophysics Data System (ADS)

Nam, S.; Yoon, S.; Park, J. H.; Kim, Y. H.; Chang, K. I.

2016-02-01

The intermediate water known as `East Sea Intermediate Water' and its coastal mode `North Korea Cold Water' found south of the Subpolar Front (SF) is formed in the northern East (Japan) Sea, and its physical properties are known to be determined by wintertime air-sea interaction north of the SF. Hydrographic data collected off the coast bi-monthly from 1994 to 2011 show significant decadal oscillations in spiciness following isopycnals of intermediate water (27.1-27.2 sigma-theta typically corresponding to 150 m depth), which are explained by the Arctic Oscillation (AO) and consequent cold-air outbreaks. During positive AO phases over the decades, the cold-air outbreak and water formation are more active and the intermediate water having the same spiciness reaches higher density (higher spiciness following the same isopycnals). At interannual timescale, however, the spiciness variability is well beyond the relationship with the AO. Especially, significantly lower spiciness (or both less saline and lower temperature) intermediate water was observed in spring of 2010 than 2001 under the similar AO condition (negative peaks). Strong cooling with common negative peaks in surface net-heat flux (with different patterns) and common negative peaks in the AO index are prominent in winter of the two years over past two decades. Such contrasting characteristics of intermediate water between 2001 and 2010 are consistent with the HYCOM reanalysis results which, along with the satellite altimetry-derived sea surface height maps, indicates widespread extension of low (high) spiciness intermediate water in the southwestern East Sea in 2010 (2001). A clear contrast in circulation pattern, along with net-heat flux pattern, is suggested to derive the observational results in the distinctly different characteristics of the intermediate water.

Pairing in a dry Fermi sea

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

Maier, Thomas A.; Staar, Peter; Mishra, V.

In the traditional Bardeen–Cooper–Schrieffer theory of superconductivity, the amplitude for the propagation of a pair of electrons with momentum k and -k has a log singularity as the temperature decreases. This so-called Cooper instability arises from the presence of an electron Fermi sea. It means that an attractive interaction, no matter how weak, will eventually lead to a pairing instability. However, in the pseudogap regime of the cuprate superconductors, where parts of the Fermi surface are destroyed, this log singularity is suppressed, raising the question of how pairing occurs in the absence of a Fermi sea. In this paper, wemore » report Hubbard model numerical results and the analysis of angular-resolved photoemission experiments on a cuprate superconductor. Finally, in contrast to the traditional theory, we find that in the pseudogap regime the pairing instability arises from an increase in the strength of the spin–fluctuation pairing interaction as the temperature decreases rather than the Cooper log instability.« less

Pairing in a dry Fermi sea

DOE PAGES

Maier, Thomas A.; Staar, Peter; Mishra, V.; ...

2016-06-17

In the traditional Bardeen–Cooper–Schrieffer theory of superconductivity, the amplitude for the propagation of a pair of electrons with momentum k and -k has a log singularity as the temperature decreases. This so-called Cooper instability arises from the presence of an electron Fermi sea. It means that an attractive interaction, no matter how weak, will eventually lead to a pairing instability. However, in the pseudogap regime of the cuprate superconductors, where parts of the Fermi surface are destroyed, this log singularity is suppressed, raising the question of how pairing occurs in the absence of a Fermi sea. In this paper, wemore » report Hubbard model numerical results and the analysis of angular-resolved photoemission experiments on a cuprate superconductor. Finally, in contrast to the traditional theory, we find that in the pseudogap regime the pairing instability arises from an increase in the strength of the spin–fluctuation pairing interaction as the temperature decreases rather than the Cooper log instability.« less

Exchanges between the open Black Sea and its North West shelf

NASA Astrophysics Data System (ADS)

Shapiro, Georgy; Wobus, Fred; Zhou, Feng

2014-05-01

offshore flow over a large section of the shelf break. Due to the short duration of strong wind effects (4-7 days) the horizontal extent of cross-shelf-break exchanges is limited to the outer shelf. The effect of Ekman drift is confined to the upper layers. In contrast, eddies and meanders penetrate deep down to the bottom, but they are restricted laterally. During the strong wind events of April 15 - 22 and July 1 - 4, some 0.66×1012 and 0.44×1012 m3of water were removed from the northwestern shelf respectively. In comparison, the single long-lived Sevastopol Eddy generated a much larger offshore transfer of 2.84×1012 m3 over the period April 23 to June 30, which is equivalent to 102% of the volume of northwestern shelf waters. This result is consistent with the data obtained from satellite derived information (Shapiro et al, 2010). The open Black Sea is generally warmer and more saline than the northwest shelf. Hence the exchanges contribute to the increase in both salinity and temperature of shelf waters. Over the study period, salt exchanges increased the average density of the shelf waters by 0.67 kg m-3 and reduced the density contrast between the shelf and deep sea, while lateral heat exchanges reduced the density of the shelf waters by 0.16 kg m-3 and thus enhanced density contrast across the shelf break. This study was supported by the EU (via PERSEUS grant FP7-OCEAN-2011-287600 and MyOcean SPA.2011.1.5-01 grant 283367), Ministry of Science and Technology of China (Grant 2011CB409803), the Natural Science Foundation of China (Grant 41276031), Zhejiang Association for International Exchange of Personnel, and the University of Plymouth Marine Institute Innovation Fund. References Huthnance, J. M., 1995. Circulation, exchange and water masses at the ocean margin: the role of physical processes at the shelf edge, Prog Oceanogr, 35(4), 353-431, Ivanov L.I., Besiktepe S., Ozsoy E., 1997. In: E.Ozsoy and A.Mikaelyan (eds). Sensitivity to change: Black Sea , Baltic Sea

The distribution and diversity of sea cucumbers in the coral reefs of the South China Sea, Sulu Sea and Sulawesi Sea

NASA Astrophysics Data System (ADS)

Woo, Sau Pinn; Yasin, Zulfigar; Ismail, Siti Hasmah; Tan, Shau Hwai

2013-11-01

A study on the distribution and diversity of sea cucumbers in the coral reefs of the South China Sea, Sulu Sea and Sulawesi Sea was carried out in July 2009. The survey was done using wandering transect underwater with SCUBA. Twelve species of sea cucumber were found from four different families and nine genera. The most dominant family was Holothuriidae (five species), followed by Stichopodidae (three species), Synaptidae (three species) and Cucumariidae with only one species. The most dominant species found around the island was Pearsonothuria graffei, which can be found abundantly on substrate of dead corals in a wide range of depth (6-15 m). The Sulawesi Sea showed a higher diversity of sea cucumber with seven different species compared to the South China Sea with only six different species and Sulu Sea with only two species. Ordination by multidimensional scaling of Bray-Curtis similarities clustered the sampling locations to three main clusters with two outgroups. Previous studies done indicated a higher diversity of sea cucumber as compared to this study. This can be indication that the population and diversity of sea cucumbers in the reef is under threat.

Eiders Somateria mollissima scavenging behind a lugworm boat

NASA Astrophysics Data System (ADS)

Leopold, Mardik F.

2002-02-01

The eider is one of the most important molluscivorous birds in the Wadden Sea, where it feeds mainly on blue mussels Mytilus edulis and edible cockles Cerastoderma edule. These prey species are within reach of the birds at all times. Other potential prey of suitable size that are abundantly present, such as several polychaete worms, or the clam Mya arenaria, are taken to a much lesser extent, possibly because they live buried in the sediment and digging them out would take too much effort. Mya may pose another problem because they grow to sizes that prevent eiders from swallowing them. Large Mya also live too deep down in the sediment, but young (small) specimens should be available to eiders. Yet, even these have only rarely been found as prey in eiders in the Wadden Sea. However, diet studies in relation to food abundance have been few, and may have missed prey that do not leave large shell fragments (i.e. in faeces studies). This paper describes observations on eiders taking both Mya and polychaete worms. The eiders fed on these prey in a fashion reminiscent of gulls that scavenge behind fishing vessels: some eiders have learnt to follow professional worm-digging boats that supply a bycatch of molluscs (mainly Mya arenaria) and polychaete worms (mainly Arenicola marina and Nephtys hombergii) .Mya and worms were also the main targets of the eiders that fed in a dense flock close to the boat's stern. Faeces found on the flats at low tide comprised mainly cockle shell fragments, a prey rarely taken by the eiders behind the boat. Faeces studies may thus give a highly biased impression of local eider diet.

Deeply hidden inside introduced biogenic structures - Pacific oyster reefs reduce detrimental barnacle overgrowth on native blue mussels

NASA Astrophysics Data System (ADS)

Buschbaum, Christian; Cornelius, Annika; Goedknegt, M. Anouk

2016-11-01

In sedimentary coastal ecosystems shells of epibenthic organisms such as blue mussels (Mytilus edulis) provide the only major attachment surface for barnacle epibionts, which may cause detrimental effects on their mussel basibionts by e.g. reducing growth rate. In the European Wadden Sea, beds of native blue mussels have been invaded by Pacific oysters Crassostrea gigas, which transformed these beds into mixed reefs of oysters with mussels. In this study, we determined the spatial distribution of M. edulis and their barnacle epibionts (Semibalanus balanoides) within the reef matrix. Mean mussel density near the bottom was about twice as high compared to the mussel density near the top of an oyster reef, whereas barnacles on mussels showed a reversed pattern. Barnacle dry weight per mussel was on average 14 times higher near the top than at the bottom. This pattern was confirmed by experimentally placing clean M. edulis at the top and on the bottom of oyster reefs at two sites in the Wadden Sea (island of Texel, The Netherlands; island of Sylt, Germany). After an experimental period of five weeks (April and May 2015, the main settlement period of S. balanoides), the number of barnacles per mussel was at both sites significantly higher on mussels near the top compared to near the bottom. We conclude that the oyster reef matrix offers a refuge for M. edulis: inside reefs they are not only better protected against predators but also against detrimental barnacle overgrowth. This study shows that alien species can cause beneficial effects for native organisms and should not be generally considered as a risk for the recipient marine ecosystems.

Phocine distemper virus (PDV) seroprevalence as predictor for future outbreaks in harbour seals.

PubMed

Ludes-Wehrmeister, Eva; Dupke, Claudia; Harder, Timm C; Baumgärtner, Wolfgang; Haas, Ludwig; Teilmann, Jonas; Dietz, Rune; Jensen, Lasse F; Siebert, Ursula

2016-02-01

Phocine distemper virus (PDV) infections caused the two most pronounced mass mortalities in marine mammals documented in the past century. During the two outbreaks, 23,000 and 30,000 harbour seals (Phoca vitulina), died in 1988/1989 and 2002 across populations in the Wadden Sea and adjacent waters, respectively. To follow the mechanism and development of disease spreading, the dynamics of Morbillivirus-specific antibodies in harbour seal populations in German and Danish waters were examined. 522 serum samples of free-ranging harbour seals of different ages were sampled between 1990 and 2014. By standard neutralisation assays, Morbillivirus-specific antibodies were detected, using either the PDV isolate 2558/Han 88 or the related canine distemper virus (CDV) strain Onderstepoort. A total of 159 (30.5%) of the harbour seals were seropositive. Annual seroprevalence rates showed an undulating course: Peaks were seen in the post-epidemic years 1990/1991 and 2002/2003. Following each PDV outbreak, seroprevalence decreased and six to eight years after the epidemics samples were tested seronegative, indicating that the populations are now again susceptible to new PDV outbreak. After the last outbreak in 2002, the populations grew steadily to an estimated maximum (since 1975) of about 39,100 individuals in the Wadden Sea in 2014 and about 23,540 harbour seals in the Kattegat area in 2013. A re-appearence of PDV would presumably result in another epizootic with high mortality rates as encountered in the previous outbreaks. The current high population density renders harbour seals vulnerable to rapid spread of infectious agents including PDV and the recently detected influenza A virus. Copyright © 2015 Elsevier B.V. All rights reserved.

Combined analysis of field and model data: A case study of the phosphate dynamics in the German Bight in summer 1994

NASA Astrophysics Data System (ADS)

Pohlmann, Th.; Raabe, Th.; Doerffer, R.; Beddig, S.; Brockmann, U.; Dick, S.; Engel, M.; Hesse, K.-J.; König, P.; Mayer, B.; Moll, A.; Murphy, D.; Puls, W.; Rick, H.-J.; Schmidt-Nia, R.; Schönfeld, W.; Sündermann, J.

1999-09-01

The intention of this paper is to analyse a specific phenomenon observed during the KUSTOS campaigns in order to demonstrate the general capability of the KUSTOS and TRANSWATT approach, i.e. the combination of field and modelling activities in an interdisciplinary framework. The selected phenomenon is the increase in phosphate concentrations off the peninsula of Eiderstedt on the North Frisian coast sampled during four subsequent station grids of the KUSTOS summer campaign in 1994. First of all, a characterisation of the observed summer situation is given. The phosphate increase is described in detail in relation to the dynamics of other nutrients. In a second step, a first-order estimate of the dispersion of phosphate is discussed. The estimate is based on the box model approach and will focus on the effects of the river Elbe and Wadden Sea inputs on phosphate dynamics. Thirdly, a fully three-dimensional model system is presented, which was implemented in order to analyse the phosphate development. The model system is discussed briefly, with emphasis on phosphorus-related processes. The reliability of one of the model components, i.e. the hydrodynamical model, is demonstrated by means of a comparison of model results with observed current data. Thereafter, results of the German Bight seston model are employed to interpret the observed phosphate increase. From this combined analysis, it was possible to conclude that the phosphate increase during the first three surveys was due to internal transformation processes within the phosphorus cycle. On the other hand, the higher phosphate concentrations measured in the last station grid survey were caused by a horizontal transport of phosphate being remobilised in the Wadden Sea.

Crustacea in Arctic and Antarctic sea ice: distribution, diet and life history strategies.

PubMed

Arndt, Carolin E; Swadling, Kerrie M

2006-01-01

This review concerns crustaceans that associate with sea ice. Particular emphasis is placed on comparing and contrasting the Arctic and Antarctic sea ice habitats, and the subsequent influence of these environments on the life history strategies of the crustacean fauna. Sea ice is the dominant feature of both polar marine ecosystems, playing a central role in physical processes and providing an essential habitat for organisms ranging in size from viruses to whales. Similarities between the Arctic and Antarctic marine ecosystems include variable cover of sea ice over an annual cycle, a light regimen that can extend from months of total darkness to months of continuous light and a pronounced seasonality in primary production. Although there are many similarities, there are also major differences between the two regions: The Antarctic experiences greater seasonal change in its sea ice extent, much of the ice is over very deep water and more than 80% breaks out each year. In contrast, Arctic sea ice often covers comparatively shallow water, doubles in its extent on an annual cycle and the ice may persist for several decades. Crustaceans, particularly copepods and amphipods, are abundant in the sea ice zone at both poles, either living within the brine channel system of the ice-crystal matrix or inhabiting the ice-water interface. Many species associate with ice for only a part of their life cycle, while others appear entirely dependent upon it for reproduction and development. Although similarities exist between the two faunas, many differences are emerging. Most notable are the much higher abundance and biomass of Antarctic copepods, the dominance of the Antarctic sea ice copepod fauna by calanoids, the high euphausiid biomass in Southern Ocean waters and the lack of any species that appear fully dependent on the ice. In the Arctic, the ice-associated fauna is dominated by amphipods. Calanoid copepods are not tightly associated with the ice, while harpacticoids and

Climate change, water, and agriculture: a study of two contrasting regions

NASA Astrophysics Data System (ADS)

Kirilenko, A.; Dronin, N.; Zhang, X.

2009-12-01

We present a study of potential impacts of climate change on water resources and agriculture in two contrasting regions, the Aral Sea basin in Central Asia and the Northern Great Plains in the United States. The Aral Sea basin is one of the most anthropogenically modified areas of the world; it is also a zone of a water-related ecological crisis. We concentrate on studying water security of five countries in the region, which inherit their water regulation from the planned economy of USSR. Water management was targeted at maximizing agricultural output through diverting the river flow into an extensive and largely ineffective network of irrigation canals. The current water crisis is largely due to human activity; however the region is also strongly impacted by the climate. Climate change will contribute to water problems, escalating irrigation demand during the drought period, and increasing water loss with evaporation. The future of the countries of the Aral Sea basin then depends on both the regional scenario of water management policy and a global scenario of climate change, and is integrated with global socioeconomic scenarios. We formulate a set of regional policy scenarios (“Business as Usual”, “Falling Behind” and “Closing the Gap”) and demonstrate how each of them corresponds to IPCC SRES scenarios, the latter used as an input to the General Circulation Models (GCMs). Then we discuss the relative effectiveness of the introduced scenarios for mitigating water problems in the region, taking into account the adaptation through changing water demand for agriculture. Finally, we introduce the results of multimodel analysis of GCM climate projections, especially in relation to the change in precipitation and frequency of droughts, and discuss the impact of climate change on future development of the region. In the same way as the Aral Sea basin, the Northern Great Plains is expected to be a region heavily impacted by climate change. We concentrate on

7 CFR 1437.310 - Sea grass and sea oats.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 10 2012-01-01 2012-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310 Agriculture Regulations of the Department of Agriculture (Continued) COMMODITY CREDIT CORPORATION, DEPARTMENT... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss...

7 CFR 1437.310 - Sea grass and sea oats.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 10 2013-01-01 2013-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310 Agriculture Regulations of the Department of Agriculture (Continued) COMMODITY CREDIT CORPORATION, DEPARTMENT... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss...

7 CFR 1437.310 - Sea grass and sea oats.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 10 2014-01-01 2014-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310 Agriculture Regulations of the Department of Agriculture (Continued) COMMODITY CREDIT CORPORATION, DEPARTMENT... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss...

Feature long axis size and local luminance contrast determine ship target acquisition performance: strong evidence for the TOD case

NASA Astrophysics Data System (ADS)

Bijl, Piet; Toet, Alexander; Kooi, Frank L.

2016-10-01

Visual images of a civilian target ship on a sea background were produced using a CAD model. The total set consisted of 264 images and included 3 different color schemes, 2 ship viewing aspects, 5 sun illumination conditions, 2 sea reflection values, 2 ship positions with respect to the horizon and 3 values of atmospheric contrast reduction. In a perception experiment, the images were presented on a display in a long darkened corridor. Observers were asked to indicate the range at which they were able to detect the ship and classify the following 5 ship elements: accommodation, funnel, hull, mast, and hat above the bridge. This resulted in a total of 1584 Target Acquisition (TA) range estimates for two observers. Next, the ship contour, ship elements and corresponding TA ranges were analyzed applying several feature size and contrast measures. Most data coincide on a contrast versus angular size plot using (1) the long axis as characteristic ship/ship feature size and (2) local Weber contrast as characteristic ship/ship feature contrast. Finally, the data were compared with a variety of visual performance functions assumed to be representative for Target Acquisition: the TOD (Triangle Orientation Discrimination), MRC (Minimum Resolvable Contrast), CTF (Contrast Threshold Function), TTP (Targeting Task Performance) metric and circular disc detection data for the unaided eye (Blackwell). The results provide strong evidence for the TOD case: both position and slope of the TOD curve match the ship detection and classification data without any free parameter. In contrast, the MRC and CTF are too steep, the TTP and disc detection curves are too shallow and all these curves need an overall scaling factor in order to coincide with the ship and ship feature recognition data.

Holocene sea surface temperature and sea ice extent in the Okhotsk and Bering Seas

USGS Publications Warehouse

Harada, Naomi; Katsuki, Kota; Nakagawa, Mitsuhiro; Matsumoto, Akiko; Seki, Osamu; Addison, Jason A.; Finney, Bruce P.; Sato, Miyako

2014-01-01

Accurate prediction of future climate requires an understanding of the mechanisms of the Holocene climate; however, the driving forces, mechanisms, and processes of climate change in the Holocene associated with different time scales remain unclear. We investigated the drivers of Holocene sea surface temperature (SST) and sea ice extent in the North Pacific Ocean, and the Okhotsk and Bering Seas, as inferred from sediment core records, by using the alkenone unsaturation index as a biomarker of SST and abundances of sea ice-related diatoms (F. cylindrus and F. oceanica) as an indicator of sea ice extent to explore controlling mechanisms in the high-latitude Pacific. Temporal changes in alkenone content suggest that alkenone production was relatively high during the middle Holocene in the Okhotsk Sea and the western North Pacific, but highest in the late Holocene in the eastern Bering Sea and the eastern North Pacific. The Holocene variations of alkenone-SSTs at sites near Kamchatka in the Northwest Pacific, as well as in the western and eastern regions of the Bering Sea, and in the eastern North Pacific track the changes of Holocene summer insolation at 50°N, but at other sites in the western North Pacific, in the southern Okhotsk Sea, and the eastern Bering Sea they do not. In addition to insolation, other atmosphere and ocean climate drivers, such as sea ice distribution and changes in the position and activity of the Aleutian Low, may have systematically influenced the timing and magnitude of warming and cooling during the Holocene within the subarctic North Pacific. Periods of high sea ice extent in both the Okhotsk and Bering Seas may correspond to some periods of frequent or strong winter–spring dust storms in the Mongolian Gobi Desert, particularly one centered at ∼4–3 thousand years before present (kyr BP). Variation in storm activity in the Mongolian Gobi Desert region may reflect changes in the strength and positions of the Aleutian Low and Siberian

7 CFR 1437.310 - Sea grass and sea oats.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 10 2011-01-01 2011-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss... paragraphs (c) through (h) of this section, except to the extent that similar provisions apply to claims...

7 CFR 1437.310 - Sea grass and sea oats.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 10 2010-01-01 2010-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss... paragraphs (c) through (h) of this section, except to the extent that similar provisions apply to claims...

The Rate of Crude Oil Biodegradation in the Sea.

PubMed

Prince, Roger C; Butler, Josh D; Redman, Aaron D

2017-02-07

Various groups have studied the rate of oil biodegradation in the sea over many years, but with no consensus on results. This can be attributed to many factors, but we show here that the principal confounding influence is the concentration of oil used in different experiments. Because of dilution, measured concentrations of dispersed oil in the sea are sub-parts-per-million within a day of dispersal, and at such concentrations the rate of biodegradation of detectable oil hydrocarbons has an apparent half-life of 7-14 days. This can be contrasted with the rate of degradation at the higher concentrations found in oil slicks or when stranded on a shoreline; there the apparent half-life varies from many months to many years.

Thermal refugia against coral bleaching throughout the northern Red Sea.

PubMed

Osman, Eslam O; Smith, David J; Ziegler, Maren; Kürten, Benjamin; Conrad, Constanze; El-Haddad, Khaled M; Voolstra, Christian R; Suggett, David J

2018-02-01

Tropical reefs have been impacted by thermal anomalies caused by global warming that induced coral bleaching and mortality events globally. However, there have only been very few recordings of bleaching within the Red Sea despite covering a latitudinal range of 15° and consequently it has been considered a region that is less sensitive to thermal anomalies. We therefore examined historical patterns of sea surface temperature (SST) and associated anomalies (1982-2012) and compared warming trends with a unique compilation of corresponding coral bleaching records from throughout the region. These data indicated that the northern Red Sea has not experienced mass bleaching despite intensive Degree Heating Weeks (DHW) of >15°C-weeks. Severe bleaching was restricted to the central and southern Red Sea where DHWs have been more frequent, but far less intense (DHWs <4°C-weeks). A similar pattern was observed during the 2015-2016 El Niño event during which time corals in the northern Red Sea did not bleach despite high thermal stress (i.e. DHWs >8°C-weeks), and bleaching was restricted to the central and southern Red Sea despite the lower thermal stress (DHWs < 8°C-weeks). Heat stress assays carried out in the northern (Hurghada) and central (Thuwal) Red Sea on four key reef-building species confirmed different regional thermal susceptibility, and that central Red Sea corals are more sensitive to thermal anomalies as compared to those from the north. Together, our data demonstrate that corals in the northern Red Sea have a much higher heat tolerance than their prevailing temperature regime would suggest. In contrast, corals from the central Red Sea are close to their thermal limits, which closely match the maximum annual water temperatures. The northern Red Sea harbours reef-building corals that live well below their bleaching thresholds and thus we propose that the region represents a thermal refuge of global importance. © 2017 John Wiley & Sons Ltd.

Results from a lab study of melting sea ice

NASA Astrophysics Data System (ADS)

Wiese, M.; Griewank, P.; Notz, D.

2012-04-01

Sea-ice melting is a complex process which is not fully understood yet. In order to study sea-ice melt in detail we perform lab experiments in an approximately 2x0.7x1.2 m large tank in a cold room. We grow sea ice with different salinities at least 10 cm thick. Then we let the ice melt at different air temperatures and oceanic heat fluxes. During the melt period, we measure the evolution of ice thickness, internal temperature, salinity and surface temperature. We will present results from roughly five months of experiments. Topics will include the influence of bulk salinity on melt rates and the surface temperature. The effects of flushing on the salinity evolution and detailed thermal profiles will also be included. To investigate these processes we focus on the energy budget and the salinity evolution. These topics are linked since the thermodynamic properties of sea ice (heat capacity, heat conductivity and latent heat of fusion) are very sensitive to salinity variations. For example the heat capacity of sea ice increases greatly as the temperature approaches the melting point. This increase results in non-linear temperature profiles and enhances heat conduction into the ice. The salinity evolution during the growth phase has been investigated and measured in multiple studies over the last decades. In contrast there are no detailed lab measurements of melting ice available to quantify the effects of flushing melt water and ponding. This is partially due to the fact that the heterogeneity of melting sea ice makes it much more difficult to measure representative values.

Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice.

PubMed

Li, Xichen; Holland, David M; Gerber, Edwin P; Yoo, Changhyun

2014-01-23

In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming of any region on the planet, causing rapid changes in land ice. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution. Antarctic climate is influenced by, among other factors, changes in radiative forcing and remote Pacific climate variability, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen-Bellingshausen-Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation and sea-level change.

Sea-floor geology in northeastern Block Island Sound, Rhode Island

USGS Publications Warehouse

McMullen, Kate Y.; Poppe, Lawrence J.; Ackerman, Seth D.; Blackwood, Dann S.; Lewit, P.G.; Parker, Castle E.

2013-01-01

Multibeam-echosounder and sidescan-sonar data collected by the National Oceanic and Atmospheric Administration in northeastern Block Island Sound, combined with sediment samples and bottom photography collected by the U.S. Geological Survey, are used to interpret sea-floor features and sedimentary environments in this 52-square-kilometer-area offshore Rhode Island. Boulders, which are often overgrown with sessile fauna and flora, are mostly in water depths shallower than 20 meters. They are probably part of the southern flank of the Harbor Hill-Roanoke Point-Charlestown-Buzzards Bay moraine, deposited about 18,000 years ago. Scour depressions, areas of the sea floor with a coarser grained, rippled surface lying about 0.5 meter below the finer grained, surrounding sea floor, along with erosional outliers within the depressions are in a band near shore and also offshore in deep parts of the study area. Textural and bathymetric differences between areas of scour depressions and the surrounding sea floor or erosional outliers stand out in the sidescan-sonar imagery with sharp tonal contrasts. Also visible in the sidescan-sonar imagery are broad, low-profile bedforms with coarser grained troughs and finer grained crests.

Effects of livestock species and stocking density on accretion rates in grazed salt marshes

NASA Astrophysics Data System (ADS)

Nolte, Stefanie; Esselink, Peter; Bakker, Jan P.; Smit, Christian

2015-01-01

Coastal ecosystems, such as salt marshes, are threatened by accelerated sea-level rise (SLR). Salt marshes deliver valuable ecosystem services such as coastal protection and the provision of habitat for a unique flora and fauna. Whether salt marshes in the Wadden Sea area are able to survive accelerated SLR depends on sufficient deposition of sediments which add to vertical marsh accretion. Accretion rate is influenced by a number of factors, and livestock grazing was recently included. Livestock grazing is assumed to reduce accretion rates in two ways: (a) directly by increasing soil compaction through trampling, and (b) indirectly by affecting the vegetation structure, which may lower the sediment deposition. For four years, we studied the impact of two livestock species (horse and cattle) at two stocking densities (0.5 and 1.0 animal ha-1) on accretion in a large-scale grazing experiment using sedimentation plates. We found lower cumulative accretion rates in high stocking densities, probably because more animals cause more compaction and create a lower canopy. Furthermore, a trend towards lower accretion rates in horse-compared to cattle-grazed treatments was found, most likely because (1) horses are more active and thus cause more compaction, and (2) herbage intake by horses is higher than by cattle, which causes a higher biomass removal and shorter canopy. During summer periods, negative accretion rates were found. When the grazing and non-grazing seasons were separated, the impact of grazing differed among years. In summer, we only found an effect of different treatments if soil moisture (precipitation) was relatively low. In winter, a sufficiently high inundation frequency was necessary to create differences between grazing treatments. We conclude that stocking densities, and to a certain extent also livestock species, affect accretion rates in salt marshes. Both stocking densities and livestock species should thus be taken into account in management

Contrast normalization in colour vision: the effect of luminance contrast on colour contrast detection

PubMed Central

Mullen, Kathy T.; Kim, Yeon Jin; Gheiratmand, Mina

2014-01-01

While contrast normalization is well known to occur in luminance vision between overlaid achromatic contrasts, and in colour vision between overlaid colour contrasts, it is unknown whether it transfers between colour and luminance contrast. Here we investigate whether contrast detection in colour vision can be normalized by achromatic contrast, or whether this is a selective process driven only by colour contrast. We use a method of cross-orientation masking, in which colour detection is masked by cross-oriented achromatic contrast, over a range of spatio-temporal frequencies (0.375–1.5 cpd, 2–8 Hz). We find that there is virtually no cross-masking of colour by achromatic contrast under monocular or binocular conditions for any of the spatio-temporal frequencies tested, although we find significant facilitation at low spatio-temporal conditions (0.375 cpd, 2 Hz). These results indicate that the process of contrast nornalization is colour selective and independent of achromatic contrast, and imply segregated chromatic signals in early visual processing. Under dichoptic conditions, however, we find a strikingly different result with significant masking of colour by achromatic contrast. This indicates that the dichoptic site of suppression is unselective, responding similarly to colour and luminance contrast, and suggests that dichoptic suppression has a different origin from monocular or binocular suppression. PMID:25491564

Automated Video Quality Assessment for Deep-Sea Video

NASA Astrophysics Data System (ADS)

Pirenne, B.; Hoeberechts, M.; Kalmbach, A.; Sadhu, T.; Branzan Albu, A.; Glotin, H.; Jeffries, M. A.; Bui, A. O. V.

2015-12-01

Video provides a rich source of data for geophysical analysis, often supplying detailed information about the environment when other instruments may not. This is especially true of deep-sea environments, where direct visual observations cannot be made. As computer vision techniques improve and volumes of video data increase, automated video analysis is emerging as a practical alternative to labor-intensive manual analysis. Automated techniques can be much more sensitive to video quality than their manual counterparts, so performing quality assessment before doing full analysis is critical to producing valid results.Ocean Networks Canada (ONC), an initiative of the University of Victoria, operates cabled ocean observatories that supply continuous power and Internet connectivity to a broad suite of subsea instruments from the coast to the deep sea, including video and still cameras. This network of ocean observatories has produced almost 20,000 hours of video (about 38 hours are recorded each day) and an additional 8,000 hours of logs from remotely operated vehicle (ROV) dives. We begin by surveying some ways in which deep-sea video poses challenges for automated analysis, including: 1. Non-uniform lighting: Single, directional, light sources produce uneven luminance distributions and shadows; remotely operated lighting equipment are also susceptible to technical failures. 2. Particulate noise: Turbidity and marine snow are often present in underwater video; particles in the water column can have sharper focus and higher contrast than the objects of interest due to their proximity to the light source and can also influence the camera's autofocus and auto white-balance routines. 3. Color distortion (low contrast): The rate of absorption of light in water varies by wavelength, and is higher overall than in air, altering apparent colors and lowering the contrast of objects at a distance.We also describe measures under development at ONC for detecting and mitigating

Wind-sea surface temperature-sea ice relationship in the Chukchi-Beaufort Seas during autumn

NASA Astrophysics Data System (ADS)

Zhang, Jing; Stegall, Steve T.; Zhang, Xiangdong

2018-03-01

Dramatic climate changes, especially the largest sea ice retreat during September and October, in the Chukchi-Beaufort Seas could be a consequence of, and further enhance, complex air-ice-sea interactions. To detect these interaction signals, statistical relationships between surface wind speed, sea surface temperature (SST), and sea ice concentration (SIC) were analyzed. The results show a negative correlation between wind speed and SIC. The relationships between wind speed and SST are complicated by the presence of sea ice, with a negative correlation over open water but a positive correlation in sea ice dominated areas. The examination of spatial structures indicates that wind speed tends to increase when approaching the ice edge from open water and the area fully covered by sea ice. The anomalous downward radiation and thermal advection, as well as their regional distribution, play important roles in shaping these relationships, though wind-driven sub-grid scale boundary layer processes may also have contributions. Considering the feedback loop involved in the wind-SST-SIC relationships, climate model experiments would be required to further untangle the underlying complex physical processes.

Modelling Potential Consequences of Different Geo-Engineering Treatments for the Baltic Sea Ecosystem

NASA Astrophysics Data System (ADS)

Schrum, C.; Daewel, U.

2017-12-01

From 1950 onwards, the Baltic Sea ecosystem suffered increasingly from eutrophication. The most obvious reason for the eutrophication is the huge amount of nutrients (nitrogen and phosphorus) reaching the Baltic Sea from human activities. However, although nutrient loads have been decreasing since 1980, the hypoxic areas have not decreased accordingly. Thus, geo-engineering projects were discussed and evaluated to artificially ventilate the Baltic Sea deep water and suppress nutrient release from the sediments. Here, we aim at understanding the consequences of proposed geo-engineering projects in the Baltic Sea using long-term scenario modelling. For that purpose, we utilize a 3d coupled ecosystem model ECOSMO E2E, a novel NPZD-Fish model approach that resolves hydrodynamics, biogeochemical cycling and lower and higher trophic level dynamics. We performed scenario modelling that consider proposed geo-engineering projects such as artificial ventilation of Baltic Sea deep waters and phosphorus binding in sediments with polyaluminium chlorides. The model indicates that deep-water ventilation indeed suppresses phosphorus release in the first 1-4 years of treatment. Thereafter macrobenthos repopulates the formerly anoxic bottom regions and nutrients are increasingly recycled in the food web. Consequently, overall system productivity and fish biomass increases and toxic algae blooms decrease. However, deep-water ventilation has no long-lasting effect on the ecosystem: soon after completion of the ventilation process, the system turns back into its original state. Artificial phosphorus binding in sediments in contrast decreases overall ecosystem productivity through permanent removal of phosphorus. As expected it decreases bacterial production and toxic algae blooms, but it also decreases fish production substantially. Contrastingly to deep water ventilation, artificial phosphorus binding show a long-lasting effect over decades after termination of the treatment.

Tectonic evolution of the Salton Sea inferred from seismic reflection data

USGS Publications Warehouse

Brothers, D.S.; Driscoll, N.W.; Kent, G.M.; Harding, A.J.; Babcock, J.M.; Baskin, R.L.

2009-01-01

Oblique extension across strike-slip faults causes subsidence and leads to the formation of pull-apart basins such as the Salton Sea in southern California. The formation of these basins has generally been studied using laboratory experiments or numerical models. Here we combine seismic reflection data and geological observations from the Salton Sea to understand the evolution of this nascent pull-apart basin. Our data reveal the presence of a northeast-trending hinge zone that separates the sea into northern and southern sub-basins. Differential subsidence (10 mm yr 1) in the southern sub-basin suggests the existence of northwest-dipping basin-bounding faults near the southern shoreline, which may control the spatial distribution of young volcanism. Rotated and truncated strata north of the hinge zone suggest that the onset of extension associated with this pull-apart basin began after 0.5 million years ago. We suggest that slip is partitioned spatially and temporally into vertical and horizontal domains in the Salton Sea. In contrast to previous models based on historical seismicity patterns, the rapid subsidence and fault architecture that we document in the southern part of the sea are consistent with experimental models for pull-apart basins. ?? 2009 Macmillan Publishers Limited.

Speciated atmospheric mercury in the marine boundary layer of the Bohai Sea and Yellow Sea

NASA Astrophysics Data System (ADS)

Wang, Chunjie; Ci, Zhijia; Wang, Zhangwei; Zhang, Xiaoshan; Guo, Jia

2016-04-01

The objectives of this study are to identify the spatial and temporal distributions of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and fine particulate mercury (HgP2.5) in the marine boundary layer (MBL) of the Bohai Sea (BS) and Yellow Sea (YS), and to investigate the relationships between mercury species and meteorological parameters. The mean concentrations of GEM, RGM, and HgP2.5 were 2.03 ng m-3, 2.5 pg m-3, and 8.2 pg m-3 in spring, and 2.09 ng m-3, 4.3 pg m-3, and 8.3 pg m-3 in fall. Reactive mercury (RGM + HgP2.5) represented < 1% of total atmospheric mercury (GEM + RGM + HgP2.5), which indicated that most mercury export in the MBL was GEM and the direct outflow of reactive mercury was very small. Moreover, GEM concentrations over the BS were generally higher than those over the YS both in spring and fall. Although RGM showed a homogeneous distribution over the BS and YS both in spring and fall, the mean RGM concentration in fall was significantly higher than that in spring. In contrast, the spatial distribution of HgP2.5 generally reflected a gradient with high levels near the coast of China and low levels in the open sea, suggesting the significant atmospheric mercury outflow from China. Interestingly, the mean RGM concentrations during daytime were significantly higher than those during nighttime both in spring and fall, while the opposite results were observed for HgP2.5. Additionally, RGM positively correlates with air temperature while negatively correlates with relative humidity. In conclusion, the elevated atmospheric mercury levels in the BS and YS compared to other open seas suggested that the human activities had a significant influence on the oceanic mercury cycle downwind of China.

50 CFR 697.12 - At-sea sea sampler/observer coverage.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false At-sea sea sampler/observer coverage. 697... MANAGEMENT General Provisions § 697.12 At-sea sea sampler/observer coverage. (a) The Regional Administrator...-approved sea sampler/observer. If requested by the Regional Administrator to carry a sea sampler/observer...

50 CFR 697.12 - At-sea sea sampler/observer coverage.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false At-sea sea sampler/observer coverage. 697... MANAGEMENT General Provisions § 697.12 At-sea sea sampler/observer coverage. (a) The Regional Administrator...-approved sea sampler/observer. If requested by the Regional Administrator to carry a sea sampler/observer...

50 CFR 697.12 - At-sea sea sampler/observer coverage.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false At-sea sea sampler/observer coverage. 697... MANAGEMENT General Provisions § 697.12 At-sea sea sampler/observer coverage. (a) The Regional Administrator...-approved sea sampler/observer. If requested by the Regional Administrator to carry a sea sampler/observer...

Sea-Level Projections from the SeaRISE Initiative

NASA Technical Reports Server (NTRS)

Nowicki, Sophie; Bindschadler, Robert

2011-01-01

SeaRISE (Sea-level Response to Ice Sheet Evolution) is a community organized modeling effort, whose goal is to inform the fifth IPCC of the potential sea-level contribution from the Greenland and Antarctic ice sheets in the 21st and 22nd century. SeaRISE seeks to determine the most likely ice sheet response to imposed climatic forcing by initializing an ensemble of models with common datasets and applying the same forcing to each model. Sensitivity experiments were designed to quantify the sea-level rise associated with a change in: 1) surface mass balance, 2) basal lubrication, and 3) ocean induced basal melt. The range of responses, resulting from the multi-model approach, is interpreted as a proxy of uncertainty in our sea-level projections. http://websrv.cs .umt.edu/isis/index.php/SeaRISE_Assessment.

Teleconnection between sea ice in the Barents Sea in June and the Silk Road, Pacific-Japan and East Asian rainfall patterns in August

NASA Astrophysics Data System (ADS)

He, Shengping; Gao, Yongqi; Furevik, Tore; Wang, Huijun; Li, Fei

2018-01-01

In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes. Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east-west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific-Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.

Teleconnection between Sea Ice in the Barents Sea in June and the Silk Road, Pacific-Japan and East Asian Rainfall Patterns in August

NASA Astrophysics Data System (ADS)

He, S.; Gao, Y.; Furevik, T.; Huijun, W.; Li, F.

2017-12-01

In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes. Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east-west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific-Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.

Under the sea ice: Exploring the relationship between sea ice and the foraging behaviour of southern elephant seals in East Antarctica

NASA Astrophysics Data System (ADS)

Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D.; Massom, Robert A.; Reid, Phillip; Sumner, Michael; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Bailleul, Frédéric; Hindell, Mark A.; Charrassin, Jean-Benoit

2017-08-01

diurnal vertical migration) in the pack ice region, likely attracted by an ice algal autumn bloom that sustains an under-ice ecosystem. In contrast, male foraging effort increased when they remained deep within the sea ice (420-960 km from the ice edge) over the shelf. Males had a longer foraging activity (i) in the lowest sea ice concentration at their position, and (ii) when there were more patches of low concentration sea ice around their position (either in time or in space; 30 days & 50 km) presumably in polynyas or flaw leads between land fast and pack ice. This provides access to zones of enhanced resources in autumn or in early spring such as polynyas, the Antarctic shelf and slope. Our results suggest that some seals utilized a highly sea ice covered environment, which is key for their foraging effort, sustaining or concentrating resources during winter.

Isolating the Liquid Cloud Response to Recent Arctic Sea Ice Variability Using Spaceborne Lidar Observations

NASA Astrophysics Data System (ADS)

Morrison, A. L.; Kay, J. E.; Chepfer, H.; Guzman, R.; Yettella, V.

2018-01-01

While the radiative influence of clouds on Arctic sea ice is known, the influence of sea ice cover on Arctic clouds is challenging to detect, separate from atmospheric circulation, and attribute to human activities. Providing observational constraints on the two-way relationship between sea ice cover and Arctic clouds is important for predicting the rate of future sea ice loss. Here we use 8 years of CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) spaceborne lidar observations from 2008 to 2015 to analyze Arctic cloud profiles over sea ice and over open water. Using a novel surface mask to restrict our analysis to where sea ice concentration varies, we isolate the influence of sea ice cover on Arctic Ocean clouds. The study focuses on clouds containing liquid water because liquid-containing clouds are the most important cloud type for radiative fluxes and therefore for sea ice melt and growth. Summer is the only season with no observed cloud response to sea ice cover variability: liquid cloud profiles are nearly identical over sea ice and over open water. These results suggest that shortwave summer cloud feedbacks do not slow long-term summer sea ice loss. In contrast, more liquid clouds are observed over open water than over sea ice in the winter, spring, and fall in the 8 year mean and in each individual year. Observed fall sea ice loss cannot be explained by natural variability alone, which suggests that observed increases in fall Arctic cloud cover over newly open water are linked to human activities.

Estimating the extent of Antarctic summer sea ice during the Heroic Age of Antarctic Exploration

NASA Astrophysics Data System (ADS)

Edinburgh, Tom; Day, Jonathan J.

2016-11-01

In stark contrast to the sharp decline in Arctic sea ice, there has been a steady increase in ice extent around Antarctica during the last three decades, especially in the Weddell and Ross seas. In general, climate models do not to capture this trend and a lack of information about sea ice coverage in the pre-satellite period limits our ability to quantify the sensitivity of sea ice to climate change and robustly validate climate models. However, evidence of the presence and nature of sea ice was often recorded during early Antarctic exploration, though these sources have not previously been explored or exploited until now. We have analysed observations of the summer sea ice edge from the ship logbooks of explorers such as Robert Falcon Scott, Ernest Shackleton and their contemporaries during the Heroic Age of Antarctic Exploration (1897-1917), and in this study we compare these to satellite observations from the period 1989-2014, offering insight into the ice conditions of this period, from direct observations, for the first time. This comparison shows that the summer sea ice edge was between 1.0 and 1.7° further north in the Weddell Sea during this period but that ice conditions were surprisingly comparable to the present day in other sectors.

The future of ice sheets and sea ice: between reversible retreat and unstoppable loss.

PubMed

Notz, Dirk

2009-12-08

We discuss the existence of cryospheric "tipping points" in the Earth's climate system. Such critical thresholds have been suggested to exist for the disappearance of Arctic sea ice and the retreat of ice sheets: Once these ice masses have shrunk below an anticipated critical extent, the ice-albedo feedback might lead to the irreversible and unstoppable loss of the remaining ice. We here give an overview of our current understanding of such threshold behavior. By using conceptual arguments, we review the recent findings that such a tipping point probably does not exist for the loss of Arctic summer sea ice. Hence, in a cooler climate, sea ice could recover rapidly from the loss it has experienced in recent years. In addition, we discuss why this recent rapid retreat of Arctic summer sea ice might largely be a consequence of a slow shift in ice-thickness distribution, which will lead to strongly increased year-to-year variability of the Arctic summer sea-ice extent. This variability will render seasonal forecasts of the Arctic summer sea-ice extent increasingly difficult. We also discuss why, in contrast to Arctic summer sea ice, a tipping point is more likely to exist for the loss of the Greenland ice sheet and the West Antarctic ice sheet.

The future of ice sheets and sea ice: Between reversible retreat and unstoppable loss

PubMed Central

Notz, Dirk

2009-01-01

We discuss the existence of cryospheric “tipping points” in the Earth's climate system. Such critical thresholds have been suggested to exist for the disappearance of Arctic sea ice and the retreat of ice sheets: Once these ice masses have shrunk below an anticipated critical extent, the ice–albedo feedback might lead to the irreversible and unstoppable loss of the remaining ice. We here give an overview of our current understanding of such threshold behavior. By using conceptual arguments, we review the recent findings that such a tipping point probably does not exist for the loss of Arctic summer sea ice. Hence, in a cooler climate, sea ice could recover rapidly from the loss it has experienced in recent years. In addition, we discuss why this recent rapid retreat of Arctic summer sea ice might largely be a consequence of a slow shift in ice-thickness distribution, which will lead to strongly increased year-to-year variability of the Arctic summer sea-ice extent. This variability will render seasonal forecasts of the Arctic summer sea-ice extent increasingly difficult. We also discuss why, in contrast to Arctic summer sea ice, a tipping point is more likely to exist for the loss of the Greenland ice sheet and the West Antarctic ice sheet. PMID:19884496

Vision in the deep sea.

PubMed

Warrant, Eric J; Locket, N Adam

2004-08-01

The deep sea is the largest habitat on earth. Its three great faunal environments--the twilight mesopelagic zone, the dark bathypelagic zone and the vast flat expanses of the benthic habitat--are home to a rich fauna of vertebrates and invertebrates. In the mesopelagic zone (150-1000 m), the down-welling daylight creates an extended scene that becomes increasingly dimmer and bluer with depth. The available daylight also originates increasingly from vertically above, and bioluminescent point-source flashes, well contrasted against the dim background daylight, become increasingly visible. In the bathypelagic zone below 1000 m no daylight remains, and the scene becomes entirely dominated by point-like bioluminescence. This changing nature of visual scenes with depth--from extended source to point source--has had a profound effect on the designs of deep-sea eyes, both optically and neurally, a fact that until recently was not fully appreciated. Recent measurements of the sensitivity and spatial resolution of deep-sea eyes--particularly from the camera eyes of fishes and cephalopods and the compound eyes of crustaceans--reveal that ocular designs are well matched to the nature of the visual scene at any given depth. This match between eye design and visual scene is the subject of this review. The greatest variation in eye design is found in the mesopelagic zone, where dim down-welling daylight and bio-luminescent point sources may be visible simultaneously. Some mesopelagic eyes rely on spatial and temporal summation to increase sensitivity to a dim extended scene, while others sacrifice this sensitivity to localise pinpoints of bright bioluminescence. Yet other eyes have retinal regions separately specialised for each type of light. In the bathypelagic zone, eyes generally get smaller and therefore less sensitive to point sources with increasing depth. In fishes, this insensitivity, combined with surprisingly high spatial resolution, is very well adapted to the

Occurrence of organohalogens at the Dead Sea Basin

NASA Astrophysics Data System (ADS)

Tubbesing, Christoph; Kotte, Karsten; Keppler, Frank; Krause, Torsten; Bahlmann, Enno; Schöler, Heinfried

2013-04-01

Most arid and semi-arid regions are characterized by evaporites, which are assured sources for volatile organohalogens (VOX) [1]. These compounds play an important role in tropospheric and stratospheric chemistry. The Dead Sea between Israel and Jordan is the world's most famous and biggest all-season water covered salt lake. In both countries chemical plants like the Dead Sea Works and the Arab Potash Company are located at the southern part of the Dead Sea and mine various elements such as bromine and magnesium. Conveying sea water through constructed evaporation pans multifarious salts are enriched and precipitated. In contrast, the Northern basin and main part of the Dead Sea has remained almost untouched by industrial salt production. Its fresh water supply from the Jordan River is constantly decreasing, leading to further increased salinity. During a HALOPROC campaign (Natural Halogenation Processes in the Environment) we collected various samples including air, soils, sediments, halophytic plants, ground- and seawater from the Northern and Southern basin of the Israeli side of the Dead Sea. These samples were investigated for the occurrence of halocarbons using different analytical techniques. Most samples were analyzed for volatile organohalogens such as haloalkanes using gas chromatography- mass spectrometry (GC-MS). Interestingly, there is a strong enrichment of trihalomethanes (THM), especially all chlorinated and brominated ones and also the iodinated compound dichloroiodomethane were found in the Southern basin. In addition, volatile organic carbons (VOC) such as ethene and some other alkenes were analyzed by a gas chromatography-flame ionisation detector (GC-FID) to obtain further information about potential precursors of halogenated compounds. Halophytic plants were investigated for their potential to release chloromethane and bromomethane but also for their stable carbon and hydrogen isotope composition. For this purpose, a plant chamber was

Detection and Genetic Analysis of Noroviruses and Sapoviruses in Sea Snail.

PubMed

Ozawa, Hiroki; Kumazaki, Makoto; Ueki, Satoshi; Morita, Masahiro; Usuku, Shuzo

2015-12-01

An outbreak of acute gastroenteritis occurred at a restaurant in Yokohama in December 2011. Because many of the customers had consumed raw sea snail, sea snail was suspected to be the source of this outbreak. To determine whether sea snail contains Norovirus (NoV) or Sapovirus (SaV), we analyzed 27 sea snail samples collected over 5 months (May, June, August, October, and December 2012) and 59.3% were positive for NoV and/or SaV. The levels of NoV ranged from 1.5 × 10(3) to 1.5 × 10(5) copies/g tissue, and those of SaV from 1.5 × 10(2) to 1.3 × 10(3) copies/g tissue. The highest levels were observed in sea snails collected in December. A phylogenetic analysis of the NoVs showed that the viral strains were NoV genotypes GI.4, GI.6, GII.4, GII.12, GII.13, and GII.14, and the SaV strains were genotypes GI.2 and GI.3. The NoV GII.4 Sydney 2012 variants were only detected in December. This variant was a major source of gastroenteritis in Japan in the winter of 2012/2013. In contrast, the NoV GII.4 strains detected in May and June 2012 were not the Sydney 2012 variant. This study demonstrates that sea snail contains multiple genogroups and genotypes of NoV and SaV strains. We conclude that the sea snail presents a risk of gastroenteritis when consumed raw.

North-western Mediterranean sea-breeze circulation in a regional climate system model

NASA Astrophysics Data System (ADS)

Drobinski, Philippe; Bastin, Sophie; Arsouze, Thomas; Béranger, Karine; Flaounas, Emmanouil; Stéfanon, Marc

2017-04-01

In the Mediterranean basin, moisture transport can occur over large distance from remote regions by the synoptic circulation or more locally by sea breezes, driven by land-sea thermal contrast. Sea breezes play an important role in inland transport of moisture especially between late spring and early fall. In order to explicitly represent the two-way interactions at the atmosphere-ocean interface in the Mediterranean region and quantify the role of air-sea feedbacks on regional meteorology and climate, simulations at 20 km resolution performed with WRF regional climate model (RCM) and MORCE atmosphere-ocean regional climate model (AORCM) coupling WRF and NEMO-MED12 in the frame of HyMeX/MED-CORDEX are compared. One result of this study is that these simulations reproduce remarkably well the intensity, direction and inland penetration of the sea breeze and even the existence of the shallow sea breeze despite the overestimate of temperature over land in both simulations. The coupled simulation provides a more realistic representation of the evolution of the SST field at fine scale than the atmosphere-only one. Temperature and moisture anomalies are created in direct response to the SST anomaly and are advected by the sea breeze over land. However, the SST anomalies are not of sufficient magnitude to affect the large-scale sea-breeze circulation. The temperature anomalies are quickly damped by strong surface heating over land, whereas the water vapor mixing ratio anomalies are transported further inland. The inland limit of significance is imposed by the vertical dilution in a deeper continental boundary-layer.

Probing safety of nanoparticles by outlining sea urchin sensing and signaling cascades.

PubMed

Alijagic, Andi; Pinsino, Annalisa

2017-10-01

Among currently identified issues presenting risks and benefits to human and ocean health, engineered nanoparticles (ENP) represent a priority. Predictions of their economic and social impact appear extraordinary, but their release in the environment at an uncontrollable rate is in striking contrast with the extremely limited number of studies on environmental impact, especially on the marine environment. The sea urchin has a remarkable sensing environmental system whose function and diversity came into focus during the recent years, after sea urchin genome sequencing. The complex immune system may be the basis wherefore sea urchins can adapt to a dynamic environment and survive even in hazardous conditions both in the adult and in the embryonic life. This review is aimed at discussing the literature in nanotoxicological/ecotoxicological studies with a focus on stress and innate immune signaling in sea urchins. In addition, here we introduce our current development of in vitro-driven probes that could be used to dissect ENP aftermaths, suggesting their future use in immune-nanotoxicology. Copyright © 2017 Elsevier Inc. All rights reserved.

Sea otter population structure and ecology in Alaska

USGS Publications Warehouse

Bodkin, James L.; Monson, Daniel H.

2002-01-01

environmental conditions. During the past decade, using molecular genetics, researchers have been trying to understand how sea otter populations might differ throughout the North Pacific and what effects population reductions and recovery have had on population genetics. Also, as a result of the varying degree of recovery among isolated populations, we have the opportunity to contrast life history attributes (such as condition, reproduction, and survival) among populations throughout their range. These contrasts may be useful in developing methods to assess the status of populations where traditional methods of surveying abundance are difficult and expensive.

Processes contributing to resilience of coastal wetlands to sea-level rise

USGS Publications Warehouse

Stagg, Camille L.; Krauss, Ken W.; Cahoon, Donald R.; Cormier, Nicole; Conner, William H.; Swarzenski, Christopher M.

2016-01-01

The objectives of this study were to identify processes that contribute to resilience of coastal wetlands subject to rising sea levels and to determine whether the relative contribution of these processes varies across different wetland community types. We assessed the resilience of wetlands to sea-level rise along a transitional gradient from tidal freshwater forested wetland (TFFW) to marsh by measuring processes controlling wetland elevation. We found that, over 5 years of measurement, TFFWs were resilient, although some marginally, and oligohaline marshes exhibited robust resilience to sea-level rise. We identified fundamental differences in how resilience is maintained across wetland community types, which have important implications for management activities that aim to restore or conserve resilient systems. We showed that the relative importance of surface and subsurface processes in controlling wetland surface elevation change differed between TFFWs and oligohaline marshes. The marshes had significantly higher rates of surface accretion than the TFFWs, and in the marshes, surface accretion was the primary contributor to elevation change. In contrast, elevation change in TFFWs was more heavily influenced by subsurface processes, such as root zone expansion or compaction, which played an important role in determining resilience of TFFWs to rising sea level. When root zone contributions were removed statistically from comparisons between relative sea-level rise and surface elevation change, sites that previously had elevation rate deficits showed a surplus. Therefore, assessments of wetland resilience that do not include subsurface processes will likely misjudge vulnerability to sea-level rise.

Sea ice in the Greenland Sea

NASA Image and Video Library

2017-12-08

As the northern hemisphere experiences the heat of summer, ice moves and melts in the Arctic waters and the far northern lands surrounding it. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite captured this true-color image of sea ice off Greenland on July 16, 2015. Large chunks of melting sea ice can be seen in the sea ice off the coast, and to the south spirals of ice have been shaped by the winds and currents that move across the Greenland Sea. Along the Greenland coast, cold, fresh melt water from the glaciers flows out to the sea, as do newly calved icebergs. Frigid air from interior Greenland pushes the ice away from the shoreline, and the mixing of cold water and air allows some sea ice to be sustained even at the height of summer. According to observations from satellites, 2015 is on track to be another low year for arctic summer sea ice cover. The past ten years have included nine of the lowest ice extents on record. The annual minimum typically occurs in late August or early September. The amount of Arctic sea ice cover has been dropping as global temperatures rise. The Arctic is two to three times more sensitive to temperature changes as the Earth as a whole. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Snow depth evolution on sea ice from Snow Buoy measurement

NASA Astrophysics Data System (ADS)

Nicolaus, M.; Arndt, S.; Hendricks, S.; Hoppmann, M.; Katlein, C.; König-Langlo, G.; Nicolaus, A.; Rossmann, H. L.; Schiller, M.; Schwegmann, S.; Langevin, D.

2016-12-01

Snow cover is an Essential Climate Variable. On sea ice, snow dominates the energy and momentum exchanges across the atmosphere-ice-ocean interfaces, and actively contributes to sea ice mass balance. Yet, snow depth on sea ice is one of the least known and most difficult to observe parameters of the Arctic and Antarctic; mainly due to its exceptionally high spatial and temporal variability. In this study; we present a unique time series dataset of snow depth and air temperature evolution on Arctic and Antarctic sea ice recorded by autonomous instruments. Snow Buoys record snow depth with four independent ultrasonic sensors, increasing the reliability of the measurements and allowing for additional analyses. Auxiliary measurements include surface and air temperature, barometric pressure and GPS position. 39 deployments of such Snow Buoys were achieved over the last three years either on drifting pack ice, on landfast sea ice or on an ice shelf. Here we highlight results from two pairs of Snow Buoys installed on drifting pack ice in the Weddell Sea. The data reveals large regional differences in the annual cycle of snow depth. Almost no reduction in snow depth (snow melt) was observed in the inner and southern part of the Weddell Sea, allowing a net snow accumulation of 0.2 to 0.9 m per year. In contrast, summer snow melt close to the ice edge resulted in a decrease of about 0.5 m during the summer 2015/16. Another array of eight Snow Buoys was installed on central Arctic sea ice in September 2015. Their air temperature record revealed exceptionally high air temperatures in the subsequent winter, even exceeding the melting point but with almost no impact on snow depth at that time. Future applications of Snow Buoys on Arctic and Antarctic sea ice will allow additional inter-annual studies of snow depth and snow processes, e.g. to support the development of snow depth data products from airborne and satellite data or though assimilation in numerical models.

Stable carbon isotope gradients in benthic foraminifera as proxy for organic carbon fluxes in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Theodor, Marc; Schmiedl, Gerhard; Jorissen, Frans; Mackensen, Andreas

2016-11-01

We have determined stable carbon isotope ratios of epifaunal and shallow infaunal benthic foraminifera in the Mediterranean Sea to relate the inferred gradient of pore water δ13CDIC to varying trophic conditions. This is a prerequisite for developing this difference into a potential transfer function for organic matter flux rates. The data set is based on samples retrieved from a well-defined bathymetric range (400-1500 m water depth) of sub-basins in the western, central, and eastern Mediterranean Sea. Regional contrasts in organic matter fluxes and associated δ13CDIC of pore water are recorded by the δ13C difference (Δδ13CUmed-Epi) between the shallow infaunal Uvigerina mediterranea and epifaunal species (Planulina ariminensis, Cibicidoides pachydermus, Cibicides lobatulus). Within epifaunal taxa, the highest δ13C values are recorded for P. ariminensis, providing the best indicator for bottom water δ13CDIC. In contrast, C. pachydermus reveals minor pore water effects at the more eutrophic sites. Because of ontogenetic trends in the δ13C signal of U. mediterranea of up to 1.04 ‰, only tests larger than 600 µm were used for the development of the transfer function. The recorded differences in the δ13C values of U. mediterranea and epifaunal taxa (Δδ13CUmed-Epi) range from -0.46 to -2.13 ‰, with generally higher offsets at more eutrophic sites. The measured δ13C differences are related to site-specific differences in microhabitat, depth of the principal sedimentary redox boundary, and TOC content of the ambient sediment. The Δδ13CUmed-Epi values reveal a consistent relation to Corg fluxes estimated from satellite-derived surface water primary production in open-marine settings of the Alboran Sea, Mallorca Channel, Strait of Sicily, and southern Aegean Sea. In contrast, Δδ13CUmed-Epi values in areas affected by intense resuspension and riverine organic matter sources of the northern to central Aegean Sea and the canyon systems of the Gulf of Lion

Hydroclimatic contrasts over Asian monsoon areas and linkages to tropical Pacific SSTs

PubMed Central

Xu, Hai; Lan, Jianghu; Sheng, Enguo; Liu, Bin; Yu, Keke; Ye, Yuanda; Shi, Zhengguo; Cheng, Peng; Wang, Xulong; Zhou, Xinying; Yeager, Kevin M.

2016-01-01

Knowledge of spatial and temporal hydroclimatic differences is critical in understanding climatic mechanisms. Here we show striking hydroclimatic contrasts between northern and southern parts of the eastern margin of the Tibetan Plateau (ETP), and those between East Asian summer monsoon (EASM) and Indian summer monsoon (ISM) areas during the past ~2,000 years. During the Medieval Period, and the last 100 to 200 years, the southern ETP (S-ETP) area was generally dry (on average), while the northern ETP (N-ETP) area was wet. During the Little Ice Age (LIA), hydroclimate over S-ETP areas was wet, while that over N-ETP area was dry (on average). Such hydroclimatic contrasts can be broadly extended to ISM and EASM areas. We contend that changes in sea surface temperatures (SSTs) of the tropical Pacific Ocean could have played important roles in producing these hydroclimatic contrasts, by forcing the north-south movement of the Intertropical Convergence Zone (ITCZ) and intensification/slowdown of Walker circulation. The results of sensitivity experiments also support such a proposition. PMID:27609356

Sedimentological imprint on subseafloor microbial communities in Western Mediterranean Sea Quaternary sediments

NASA Astrophysics Data System (ADS)

Ciobanu, M.-C.; Rabineau, M.; Droz, L.; Révillon, S.; Ghiglione, J.-F.; Dennielou, B.; Jorry, S.-J.; Kallmeyer, J.; Etoubleau, J.; Pignet, P.; Crassous, P.; Vandenabeele-Trambouze, O.; Laugier, J.; Guégan, M.; Godfroy, A.; Alain, K.

2012-09-01

An interdisciplinary study was conducted to evaluate the relationship between geological and paleoenvironmental parameters and the bacterial and archaeal community structure of two contrasting subseafloor sites in the Western Mediterranean Sea (Ligurian Sea and Gulf of Lion). Both depositional environments in this area are well-documented from paleoclimatic and paleooceanographic point of views. Available data sets allowed us to calibrate the investigated cores with reference and dated cores previously collected in the same area, and notably correlated to Quaternary climate variations. DNA-based fingerprints showed that the archaeal diversity was composed by one group, Miscellaneous Crenarchaeotic Group (MCG), within the Gulf of Lion sediments and of nine different lineages (dominated by MCG, South African Gold Mine Euryarchaeotal Group (SAGMEG) and Halobacteria) within the Ligurian Sea sediments. Bacterial molecular diversity at both sites revealed mostly the presence of the classes Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria within Proteobacteria phylum, and also members of Bacteroidetes phylum. The second most abundant lineages were Actinobacteria and Firmicutes at the Gulf of Lion site and Chloroflexi at the Ligurian Sea site. Various substrates and cultivation conditions allowed us to isolate 75 strains belonging to four lineages: Alpha-, Gammaproteobacteria, Firmicutes and Actinobacteria. In molecular surveys, the Betaproteobacteria group was consistently detected in the Ligurian Sea sediments, characterized by a heterolithic facies with numerous turbidites from a deep-sea levee. Analysis of relative betaproteobacterial abundances and turbidite frequency suggested that the microbial diversity was a result of main climatic changes occurring during the last 20 ka. Statistical direct multivariate canonical correspondence analyses (CCA) showed that the availability of electron acceptors and the quality of electron donors (indicated by age

50 CFR 648.11 - At-sea sea sampler/observer coverage.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false At-sea sea sampler/observer coverage. 648... Provisions § 648.11 At-sea sea sampler/observer coverage. (a) The Regional Administrator may request any vessel holding a permit for Atlantic sea scallops, NE multispecies, monkfish, skates, Atlantic mackerel...

A new subspecies of sea snake, Hydrophis platurus xanthos, from Golfo Dulce, Costa Rica

PubMed Central

Bessesen, Brooke L.; Galbreath, Gary J.

2017-01-01

Abstract We describe a distinctive new subspecies of sea snake from the occasionally anoxic inner-basin waters of Golfo Dulce, Costa Rica, based on combined data garnered between 2010 and 2017 for 154 specimens, 123 free-ranging and 31 museum-held. The yellow sea snake, Hydrophis platurus xanthos Bessesen & Galbreath, subsp. n., is diagnosed by a notably smaller body size and nearly uniform yellow coloration, which contrasts with the black and yellow striae and tail spots or bands typical of the species. Within the modest geographic range (circa 320 km2), nearly all specimens possess both diagnostic character states. Bathymetrics appear to restrict genetic flow between this allopatric population and conspecifics in the broader Eastern Pacific. In perspicuous contrast to typical H. platurus, H. p. xanthos shows no association with drift lines, and feeds at night in turbulent waters, assuming a sinusoidal ambush posture never previously reported for the species. This evolutionarily significant unit (ESU) warrants taxonomic recognition and active protection. PMID:29200918

The Impact of Sea Surface Temperature Front on Stratus-Sea Fog over the Yellow and East China Seas

NASA Astrophysics Data System (ADS)

Zhang, S.; Li, M.; Liu, F.

2013-12-01

A stratus-sea fog event occurred on 3 June 2011 over the Yellow and East China Seas (as shown in figure) is investigated observationally and numerically. Emphasis is put on the influences of the sea surface temperature front (SSTF) and of the synoptic circulations on the transition of stratus to sea fog. The southerly winds from a synoptic high pressure transport water vapor from the East China Sea to the Yellow Sea, while the subsidence induced by the high contributes to the formation of the temperature inversion on the top of the stratus or stratocumulus that appears mainly over the warm flank of a sea surface temperature front in the East China Sea. Forced by the SSTF, there is a secondary cell within the atmospheric boundary layer (ABL), with a sinking branch on the cold flank and a rising one on the warm flank of the SSTF. This sinking branch, in phase with the synoptic subsidence, forces the stratus or stratocumulus to lower in the elevation getting close to the sea surface as these clouds move northward driven by the southerly winds. The cloud droplets can either reach to the sea surface directly or evaporate into water vapor that may condense again when coming close to the cold sea surface to form fog. In this later case, the stratus and fog may separate. The cooling effect of cold sea surface counteracts the adiabatic heating induced by the subsidence and thus helps the transition of stratus to sea fog in the southern Yellow Sea. By smoothing the SSTF in the numerical experiment, the secondary cell weakens and the sea fog patches shrink obviously over the cold flank of the SSTF though the synoptic subsidence and moist advection still exist. A conceptual model is suggested for the transition of stratus to sea fog in the Yellow and East China Seas, which is helpful for the forecast of sea fog over these areas. The satellite visible image of the stratus-fog event. The fog appears in the Yellow Sea and the stratocumulus in the East China Sea.

Sea Surface Wakes Observed by Spaceborne SAR in the Offshore Wind Farms

NASA Astrophysics Data System (ADS)

Li, Xiaoming; Lehner, Susanne; Jacobsen, Sven

2014-11-01

In the paper, we present some X-band spaceborne synthetic aperture radar (SAR) TerraSAR-X (TS-X) images acquired at the offshore wind farms in the North Sea and the East China Sea. The high spatial resolution SAR images show different sea surface wake patterns downstream of the offshore wind turbines. The analysis suggests that there are major two types of wakes among the observed cases. The wind turbine wakes generated by movement of wind around wind turbines are the most often observed cases. In contrast, due to the strong local tidal currents in the near shore wind farm sites, the tidal current wakes induced by tidal current impinging on the wind turbine piles are also observed in the high spatial resolution TS-X images. The discrimination of the two types of wakes observed in the offshore wind farms is also described in the paper.

Comparative metagenomics of microbial communities inhabiting deep-sea hydrothermal vent chimneys with contrasting chemistries

PubMed Central

Xie, Wei; Wang, Fengping; Guo, Lei; Chen, Zeling; Sievert, Stefan M; Meng, Jun; Huang, Guangrui; Li, Yuxin; Yan, Qingyu; Wu, Shan; Wang, Xin; Chen, Shangwu; He, Guangyuan; Xiao, Xiang; Xu, Anlong

2011-01-01

Deep-sea hydrothermal vent chimneys harbor a high diversity of largely unknown microorganisms. Although the phylogenetic diversity of these microorganisms has been described previously, the adaptation and metabolic potential of the microbial communities is only beginning to be revealed. A pyrosequencing approach was used to directly obtain sequences from a fosmid library constructed from a black smoker chimney 4143-1 in the Mothra hydrothermal vent field at the Juan de Fuca Ridge. A total of 308 034 reads with an average sequence length of 227 bp were generated. Comparative genomic analyses of metagenomes from a variety of environments by two-way clustering of samples and functional gene categories demonstrated that the 4143-1 metagenome clustered most closely with that from a carbonate chimney from Lost City. Both are highly enriched in genes for mismatch repair and homologous recombination, suggesting that the microbial communities have evolved extensive DNA repair systems to cope with the extreme conditions that have potential deleterious effects on the genomes. As previously reported for the Lost City microbiome, the metagenome of chimney 4143-1 exhibited a high proportion of transposases, implying that horizontal gene transfer may be a common occurrence in the deep-sea vent chimney biosphere. In addition, genes for chemotaxis and flagellar assembly were highly enriched in the chimney metagenomes, reflecting the adaptation of the organisms to the highly dynamic conditions present within the chimney walls. Reconstruction of the metabolic pathways revealed that the microbial community in the wall of chimney 4143-1 was mainly fueled by sulfur oxidation, putatively coupled to nitrate reduction to perform inorganic carbon fixation through the Calvin–Benson–Bassham cycle. On the basis of the genomic organization of the key genes of the carbon fixation and sulfur oxidation pathways contained in the large genomic fragments, both obligate and facultative

Ice in Caspian Sea and Aral Sea, Kazakhstan

NASA Technical Reports Server (NTRS)

2002-01-01

In this MODIS image from December 3, 2001, winter sea ice can be seen forming in the shallow waters of the northern Caspian (left) and Aral (upper right) Seas. Despite the inflow of the Volga River (upper left), the northern portion of the Caspian Sea averages only 17 ft in depth, and responds to the region's continental climate, which is cold in winter and hot and dry in the summer. The southern part of the Sea is deeper and remains ice-free throughout the winter. The dirty appearance of the ice may be due to sediment in the water, but may also be due to wind-driven dust. The wind in the region can blow at hurricane-force strength and can cause the ice to pile up in hummocks that are anchored to the sea bottom. The eastern portion of the Aral Sea is also beginning to freeze. At least two characteristics of the Aral Sea 'compete' in determining whether its waters will freeze. The Sea is shallow, which increases the likelihood of freezing, but it is also very salty, which means that lower temperatures are required to freeze it than would be required for fresh water. With average December temperatures of 18o F, it's clearly cold enough to allow ice to form. As the waters that feed the Aral Sea continue to be diverted for agriculture, the Sea becomes shallower and the regional climate becomes even more continental. This is because large bodies of water absorb and retain heat, moderating seasonal changes in temperature. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

Seasonal variation of assemblage and feeding guild structure of fish species in a boreal tidal basin

NASA Astrophysics Data System (ADS)

Kellnreitner, Florian; Pockberger, Moritz; Asmus, Harald

2012-08-01

Species composition, abundance, feeding relationships and guild structure of the fish assemblage in the Sylt-Rømø bight, a tidal basin in the northern Wadden Sea, were investigated to show seasonal differences and the importance of functional groups in this area. The tidal flats and in shallow subtidal areas were sampled using a beach seine and a bottom trawl net was used for deeper subtidal areas and tidal gullies. Species richness of fish was highest in summer where 26 species were caught, while the lowest richness was recorded in winter (17 species). Clear differences in species richness and abundance were found between shallow areas and deeper parts of the bight. Clupea harengus and Ammodytes tobianus were the most abundant species in deeper areas, while Pomatoschistus microps and Pomatoschistus minutus dominated shallower waters. Gut contents of 27 fish species were identified and the guild structure analyzed by UPGMA clustering of niche overlaps. Calanoid copepods (19.9%), Crangon crangon (18.2%) and mysid shrimps (8.4%) were the most abundant prey items of all fish species combined. Seven feeding guilds were present in the fall and winter, and eight and six in spring and summer, respectively. Fish feeding on calanoid copepods and C. crangon were present year round, whereas the occurrence of other guilds varied between seasons. Species composition of prey changed through seasons and, for some fish species, even the feeding mode itself varied with season. Most noticeable, 11 fish species changed guilds between seasons. We found a convergence in summer towards abundant prey items, whereas in winter diet overlap was lower. This is the first investigation of guild structure of almost all fish species present in a Wadden Sea area, and shows that consideration of seasonal differences is essential when determining feeding relationships of fish in temperate areas.

A speeded-up saliency region-based contrast detection method for small targets

NASA Astrophysics Data System (ADS)

Li, Zhengjie; Zhang, Haiying; Bai, Jiaojiao; Zhou, Zhongjun; Zheng, Huihuang

2018-04-01

To cope with the rapid development of the real applications for infrared small targets, the researchers have tried their best to pursue more robust detection methods. At present, the contrast measure-based method has become a promising research branch. Following the framework, in this paper, a speeded-up contrast measure scheme is proposed based on the saliency detection and density clustering. First, the saliency region is segmented by saliency detection method, and then, the Multi-scale contrast calculation is carried out on it instead of traversing the whole image. Second, the target with a certain "integrity" property in spatial is exploited to distinguish the target from the isolated noises by density clustering. Finally, the targets are detected by a self-adaptation threshold. Compared with time-consuming MPCM (Multiscale Patch Contrast Map), the time cost of the speeded-up version is within a few seconds. Additional, due to the use of "clustering segmentation", the false alarm caused by heavy noises can be restrained to a lower level. The experiments show that our method has a satisfied FASR (False alarm suppression ratio) and real-time performance compared with the state-of-art algorithms no matter in cloudy sky or sea-sky background.

Between land and sea: divergent data stewardship practices in deep-sea biosphere research

NASA Astrophysics Data System (ADS)

Cummings, R.; Darch, P.

2013-12-01

centralized storage. In the laboratory, a scientist is his or her own curator. In contrast to the IODP research parties, laboratory research teams analyze diverse datasets, share them internally, implement ad hoc data management practices, optimize methods for their specific research questions, and release data on request through personal transactions. We discovered that while these workflows help small research teams retain flexibility and local control - crucial in exploratory deep-sea biosphere research - they also hinder data interoperability, discoverability, and consistency of methods from one research team to the next. Additional consequences of this contrast between IODP and lab practices are that it is difficult to track the provenance of data and to create linkages between laboratory findings, cruise data, and archived IODP samples. The ability to track provenance would add value to datasets and provide a clearer picture of the decisions made throughout the data lifecycle. Better linkages between the original data, laboratory data, and samples would allow secondary researchers to locate IODP data that may be useful to their research after laboratory findings are published. Our case study is funded by the Sloan Foundation and NSF.

Hsp90 and hepatobiliary transformation during sea lamprey metamorphosis.

PubMed

Chung-Davidson, Yu-Wen; Yeh, Chu-Yin; Bussy, Ugo; Li, Ke; Davidson, Peter J; Nanlohy, Kaben G; Brown, C Titus; Whyard, Steven; Li, Weiming

2015-12-01

Biliary atresia (BA) is a human infant disease with inflammatory fibrous obstructions in the bile ducts and is the most common cause for pediatric liver transplantation. In contrast, the sea lamprey undergoes developmental BA with transient cholestasis and fibrosis during metamorphosis, but emerges as a fecund adult. Therefore, sea lamprey liver metamorphosis may serve as an etiological model for human BA and provide pivotal information for hepatobiliary transformation and possible therapeutics. We hypothesized that liver metamorphosis in sea lamprey is due to transcriptional reprogramming that dictates cellular remodeling during metamorphosis. We determined global gene expressions in liver at several metamorphic landmark stages by integrating mRNA-Seq and gene ontology analyses, and validated the results with real-time quantitative PCR, histological and immunohistochemical staining. These analyses revealed that gene expressions of protein folding chaperones, membrane transporters and extracellular matrices were altered and shifted during liver metamorphosis. HSP90, important in protein folding and invertebrate metamorphosis, was identified as a candidate key factor during liver metamorphosis in sea lamprey. Blocking HSP90 with geldanamycin facilitated liver metamorphosis and decreased the gene expressions of the rate limiting enzyme for cholesterol biosynthesis, HMGCoA reductase (hmgcr), and bile acid biosynthesis, cyp7a1. Injection of hsp90 siRNA for 4 days altered gene expressions of met, hmgcr, cyp27a1, and slc10a1. Bile acid concentrations were increased while bile duct and gall bladder degeneration was facilitated and synchronized after hsp90 siRNA injection. HSP90 appears to play crucial roles in hepatobiliary transformation during sea lamprey metamorphosis. Sea lamprey is a useful animal model to study postembryonic development and mechanisms for hsp90-induced hepatobiliary transformation.

The importance of sea ice for exchange of habitat-specific protist communities in the Central Arctic Ocean

NASA Astrophysics Data System (ADS)

Hardge, Kristin; Peeken, Ilka; Neuhaus, Stefan; Lange, Benjamin A.; Stock, Alexandra; Stoeck, Thorsten; Weinisch, Lea; Metfies, Katja

2017-01-01

Sea ice is one of the main features influencing the Arctic marine protist community composition and diversity in sea ice and sea water. We analyzed protist communities within sea ice, melt pond water, under-ice water and deep-chlorophyll maximum water at eight sea ice stations sampled during summer of the 2012 record sea ice minimum year. Using Illumina sequencing, we identified characteristic communities associated with specific habitats and investigated protist exchange between these habitats. The highest abundance and diversity of unique taxa were found in sea ice, particularly in multi-year ice (MYI), highlighting the importance of sea ice as a unique habitat for sea ice protists. Melting of sea ice was associated with increased exchange of communities between sea ice and the underlying water column. In contrast, sea ice formation was associated with increased exchange between all four habitats, suggesting that brine rejection from the ice is an important factor for species redistribution in the Central Arctic. Ubiquitous taxa (e.g. Gymnodinium) that occurred in all habitats still had habitat-preferences. This demonstrates a limited ability to survive in adjacent but different environments. Our results suggest that the continued reduction of sea ice extent, and particularly of MYI, will likely lead to diminished protist exchange and subsequently, could reduce species diversity in all habitats of the Central Arctic Ocean. An important component of the unique sea ice protist community could be endangered because specialized taxa restricted to this habitat may not be able to adapt to rapid environmental changes.

Deglacial development of (sub) sea surface temperature and salinity in the subarctic northwest Pacific: Implications for upper-ocean stratification

NASA Astrophysics Data System (ADS)

Riethdorf, Jan-Rainer; Max, Lars; Nürnberg, Dirk; Lembke-Jene, Lester; Tiedemann, Ralf

2013-01-01

Based on models and proxy data, it has been proposed that salinity-driven stratification weakened in the subarctic North Pacific during the last deglaciation, which potentially contributed to the deglacial rise in atmospheric carbon dioxide. We present high-resolution subsurface temperature (TMg/Ca) and subsurface salinity-approximating (δ18Oivc-sw) records across the last 20,000 years from the subarctic North Pacific and its marginal seas, derived from combined stable oxygen isotopes and Mg/Ca ratios of the planktonic foraminiferal species Neogloboquadrina pachyderma (sin.). Our results indicate regionally differing changes of subsurface conditions. During the Heinrich Stadial 1 and the Younger Dryas cold phases, our sites were subject to reduced thermal stratification, brine rejection due to sea-ice formation, and increased advection of low-salinity water from the Alaskan Stream. In contrast, the Bølling-Allerød warm phase was characterized by strengthened thermal stratification, stronger sea-ice melting, and influence of surface waters that were less diluted by the Alaskan Stream. From direct comparison with alkenone-based sea surface temperature estimates (SSTUk'37), we suggest deglacial thermocline changes that were closely related to changes in seasonal contrasts and stratification of the mixed layer. The modern upper-ocean conditions seem to have developed only since the early Holocene.

Sea-ice evaluation of NEMO-Nordic 1.0: a NEMO-LIM3.6-based ocean-sea-ice model setup for the North Sea and Baltic Sea

NASA Astrophysics Data System (ADS)

Pemberton, Per; Löptien, Ulrike; Hordoir, Robinson; Höglund, Anders; Schimanke, Semjon; Axell, Lars; Haapala, Jari

2017-08-01

The Baltic Sea is a seasonally ice-covered marginal sea in northern Europe with intense wintertime ship traffic and a sensitive ecosystem. Understanding and modeling the evolution of the sea-ice pack is important for climate effect studies and forecasting purposes. Here we present and evaluate the sea-ice component of a new NEMO-LIM3.6-based ocean-sea-ice setup for the North Sea and Baltic Sea region (NEMO-Nordic). The setup includes a new depth-based fast-ice parametrization for the Baltic Sea. The evaluation focuses on long-term statistics, from a 45-year long hindcast, although short-term daily performance is also briefly evaluated. We show that NEMO-Nordic is well suited for simulating the mean sea-ice extent, concentration, and thickness as compared to the best available observational data set. The variability of the annual maximum Baltic Sea ice extent is well in line with the observations, but the 1961-2006 trend is underestimated. Capturing the correct ice thickness distribution is more challenging. Based on the simulated ice thickness distribution we estimate the undeformed and deformed ice thickness and concentration in the Baltic Sea, which compares reasonably well with observations.

A tale of two seas: contrasting patterns of population structure in the small-spotted catshark across Europe

PubMed Central

Gubili, Chrysoula; Sims, David W.; Veríssimo, Ana; Domenici, Paolo; Ellis, Jim; Grigoriou, Panagiotis; Johnson, Andrew F.; McHugh, Matthew; Neat, Francis; Satta, Andrea; Scarcella, Giuseppe; Serra-Pereira, Bárbara; Soldo, Alen; Genner, Martin J.; Griffiths, Andrew M.

2014-01-01

Elasmobranchs represent important components of marine ecosystems, but they can be vulnerable to overexploitation. This has driven investigations into the population genetic structure of large-bodied pelagic sharks, but relatively little is known of population structure in smaller demersal taxa, which are perhaps more representative of the biodiversity of the group. This study explores spatial population genetic structure of the small-spotted catshark (Scyliorhinus canicula), across European seas. The results show significant genetic differences among most of the Mediterranean sample collections, but no significant structure among Atlantic shelf areas. The data suggest the Mediterranean populations are likely to have persisted in a stable and structured environment during Pleistocene sea-level changes. Conversely, the Northeast Atlantic populations would have experienced major changes in habitat availability during glacial cycles, driving patterns of population reduction and expansion. The data also provide evidence of male-biased dispersal and female philopatry over large spatial scales, implying complex sex-determined differences in the behaviour of elasmobranchs. On the basis of this evidence, we suggest that patterns of connectivity are determined by trends of past habitat stability that provides opportunity for local adaptation in species exhibiting philopatric behaviour, implying that resilience of populations to fisheries and other stressors may differ across the range of species. PMID:26064555

The application of ERTS imagery to monitoring Arctic sea ice. [mapping ice in Bering Sea, Beaufort Sea, Canadian Archipelago, and Greenland Sea

NASA Technical Reports Server (NTRS)

Barnes, J. C. (Principal Investigator); Bowley, C. J.

1974-01-01

The author has identified the following significant results. Because of the effect of sea ice on the heat balance of the Arctic and because of the expanding economic interest in arctic oil and minerals, extensive monitoring and further study of sea ice is required. The application of ERTS data for mapping ice is evaluated for several arctic areas, including the Bering Sea, the eastern Beaufort Sea, parts of the Canadian Archipelago, and the Greenland Sea. Interpretive techniques are discussed, and the scales and types of ice features that can be detected are described. For the Bering Sea, a sample of ERTS-1 imagery is compared with visual ice reports and aerial photography from the NASA CV-990 aircraft. The results of the investigation demonstrate that ERTS-1 imagery has substantial practical application for monitoring arctic sea ice. Ice features as small as 80-100 m in width can be detected, and the combined use of the visible and near-IR imagery is a powerful tool for identifying ice types. Sequential ERTS-1 observations at high latitudes enable ice deformations and movements to be mapped. Ice conditions in the Bering Sea during early March depicted in ERTS-1 images are in close agreement with aerial ice observations and photographs.

Evidence for high salinity of Early Cretaceous sea water from the Chesapeake Bay crater.

PubMed

Sanford, Ward E; Doughten, Michael W; Coplen, Tyler B; Hunt, Andrew G; Bullen, Thomas D

2013-11-14

High-salinity groundwater more than 1,000 metres deep in the Atlantic coastal plain of the USA has been documented in several locations, most recently within the 35-million-year-old Chesapeake Bay impact crater. Suggestions for the origin of increased salinity in the crater have included evaporite dissolution, osmosis and evaporation from heating associated with the bolide impact. Here we present chemical, isotopic and physical evidence that together indicate that groundwater in the Chesapeake crater is remnant Early Cretaceous North Atlantic (ECNA) sea water. We find that the sea water is probably 100-145 million years old and that it has an average salinity of about 70 per mil, which is twice that of modern sea water and consistent with the nearly closed ECNA basin. Previous evidence for temperature and salinity levels of ancient oceans have been estimated indirectly from geochemical, isotopic and palaeontological analyses of solid materials in deep sediment cores. In contrast, our study identifies ancient sea water in situ and provides a direct estimate of its age and salinity. Moreover, we suggest that it is likely that remnants of ECNA sea water persist in deep sediments at many locations along the Atlantic margin.

Sea-Salt Aerosol Forecasts Compared with Wave and Sea-Salt Measurements in the Open Mediterranean Sea

NASA Astrophysics Data System (ADS)

Kishcha, P.; Starobinets, B.; Bozzano, R.; Pensieri, S.; Canepa, E.; Nickovie, S.; di Sarra, A.; Udisti, R.; Becagli, S.; Alpert, P.

2012-03-01

Sea-salt aerosol (SSA) could influence the Earth's climate acting as cloud condensation nuclei. However, there were no regular measurements of SSA in the open sea. At Tel-Aviv University, the DREAM-Salt prediction system has been producing daily forecasts of 3-D distribution of sea-salt aerosol concentrations over the Mediterranean Sea (http://wind.tau.ac.il/saltina/ salt.html). In order to evaluate the model performance in the open sea, daily modeled concentrations were compared directly with SSA measurements taken at the tiny island of Lampedusa, in the Central Mediterranean. In order to further test the robustness of the model, the model performance over the open sea was indirectly verified by comparing modeled SSA concentrations with wave height measurements collected by the ODAS Italia 1 buoy and the Llobregat buoy. Model-vs.-measurement comparisons show that the model is capable of producing realistic SSA concentrations and their day-today variations over the open sea, in accordance with observed wave height and wind speed.

Contrasting seasonal responses in dinitrogen fixation between shallow and deep-water colonies of the model coral Stylophora pistillata in the northern Red Sea.

PubMed

Bednarz, Vanessa N; Naumann, Malik S; Cardini, Ulisse; van Hoytema, Nanne; Rix, Laura; Al-Rshaidat, Mamoon M D; Wild, Christian

2018-01-01

Tropical corals are often associated with dinitrogen (N2)-fixing bacteria (diazotrophs), and seasonal changes in key environmental parameters, such as dissolved inorganic nitrogen (DIN) availability and seawater temperature, are known to affect N2 fixation in coral-microbial holobionts. Despite, then, such potential for seasonal and depth-related changes in N2 fixation in reef corals, such variation has not yet been investigated. Therefore, this study quantified seasonal (winter vs. summer) N2 fixation rates associated with the reef-building coral Stylophora pistillata collected from depths of 5, 10 and 20 m in the northern Gulf of Aqaba (Red Sea). Findings revealed that corals from all depths exhibited the highest N2 fixation rates during the oligotrophic summer season, when up to 11% of their photo-metabolic nitrogen demand (CPND) could be met by N2 fixation. While N2 fixation remained seasonally stable for deep corals (20 m), it significantly decreased for the shallow corals (5 and 10 m) during the DIN-enriched winter season, accounting for less than 2% of the corals' CPND. This contrasting seasonal response in N2 fixation across corals of different depths could be driven by 1) release rates of coral-derived organic matter, 2) the community composition of the associated diazotrophs, and/or 3) nutrient acquisition by the Symbiodinium community.

Estimation of Antarctic Land-Fast Sea Ice Algal Biomass and Snow Thickness From Under-Ice Radiance Spectra in Two Contrasting Areas

NASA Astrophysics Data System (ADS)

Wongpan, P.; Meiners, K. M.; Langhorne, P. J.; Heil, P.; Smith, I. J.; Leonard, G. H.; Massom, R. A.; Clementson, L. A.; Haskell, T. G.

2018-03-01

Fast ice is an important component of Antarctic coastal marine ecosystems, providing a prolific habitat for ice algal communities. This work examines the relationships between normalized difference indices (NDI) calculated from under-ice radiance measurements and sea ice algal biomass and snow thickness for Antarctic fast ice. While this technique has been calibrated to assess biomass in Arctic fast ice and pack ice, as well as Antarctic pack ice, relationships are currently lacking for Antarctic fast ice characterized by bottom ice algae communities with high algal biomass. We analyze measurements along transects at two contrasting Antarctic fast ice sites in terms of platelet ice presence: near and distant from an ice shelf, i.e., in McMurdo Sound and off Davis Station, respectively. Snow and ice thickness, and ice salinity and temperature measurements support our paired in situ optical and biological measurements. Analyses show that NDI wavelength pairs near the first chlorophyll a (chl a) absorption peak (≈440 nm) explain up to 70% of the total variability in algal biomass. Eighty-eight percent of snow thickness variability is explained using an NDI with a wavelength pair of 648 and 567 nm. Accounting for pigment packaging effects by including the ratio of chl a-specific absorption coefficients improved the NDI-based algal biomass estimation only slightly. Our new observation-based algorithms can be used to estimate Antarctic fast ice algal biomass and snow thickness noninvasively, for example, by using moored sensors (time series) or mapping their spatial distributions using underwater vehicles.

Tropical Marginal Seas: Priority Regions for Managing Marine Biodiversity and Ecosystem Function

NASA Astrophysics Data System (ADS)

McKinnon, A. David; Williams, Alan; Young, Jock; Ceccarelli, Daniela; Dunstan, Piers; Brewin, Robert J. W.; Watson, Reg; Brinkman, Richard; Cappo, Mike; Duggan, Samantha; Kelley, Russell; Ridgway, Ken; Lindsay, Dhugal; Gledhill, Daniel; Hutton, Trevor; Richardson, Anthony J.

2014-01-01

Tropical marginal seas (TMSs) are natural subregions of tropical oceans containing biodiverse ecosystems with conspicuous, valued, and vulnerable biodiversity assets. They are focal points for global marine conservation because they occur in regions where human populations are rapidly expanding. Our review of 11 TMSs focuses on three key ecosystems - coral reefs and emergent atolls, deep benthic systems, and pelagic biomes - and synthesizes, illustrates, and contrasts knowledge of biodiversity, ecosystem function, interaction between adjacent habitats, and anthropogenic pressures. TMSs vary in the extent that they have been subject to human influence - from the nearly pristine Coral Sea to the heavily exploited South China and Caribbean Seas - but we predict that they will all be similarly complex to manage because most span multiple national jurisdictions. We conclude that developing a structured process to identify ecologically and biologically significant areas that uses a set of globally agreed criteria is a tractable first step toward effective multinational and transboundary ecosystem management of TMSs.

Tropical marginal seas: priority regions for managing marine biodiversity and ecosystem function.

PubMed

McKinnon, A David; Williams, Alan; Young, Jock; Ceccarelli, Daniela; Dunstan, Piers; Brewin, Robert J W; Watson, Reg; Brinkman, Richard; Cappo, Mike; Duggan, Samantha; Kelley, Russell; Ridgway, Ken; Lindsay, Dhugal; Gledhill, Daniel; Hutton, Trevor; Richardson, Anthony J

2014-01-01

Tropical marginal seas (TMSs) are natural subregions of tropical oceans containing biodiverse ecosystems with conspicuous, valued, and vulnerable biodiversity assets. They are focal points for global marine conservation because they occur in regions where human populations are rapidly expanding. Our review of 11 TMSs focuses on three key ecosystems-coral reefs and emergent atolls, deep benthic systems, and pelagic biomes-and synthesizes, illustrates, and contrasts knowledge of biodiversity, ecosystem function, interaction between adjacent habitats, and anthropogenic pressures. TMSs vary in the extent that they have been subject to human influence-from the nearly pristine Coral Sea to the heavily exploited South China and Caribbean Seas-but we predict that they will all be similarly complex to manage because most span multiple national jurisdictions. We conclude that developing a structured process to identify ecologically and biologically significant areas that uses a set of globally agreed criteria is a tractable first step toward effective multinational and transboundary ecosystem management of TMSs.

Southeastern United States and Caribbean Sea from Apollo 8 spacecraft

NASA Technical Reports Server (NTRS)

1968-01-01

Most of the southeastern United States and Caribbean Sea, the U.S. coastline from Chesapeake Bay to the Florida peninsula can be seen from the Apollo 8 spacecraft in orbit above the Earth. The Bahamas and the Islands of Cuba, Jamaica, Hispiniola and Puerto Rico extend across the Caribbean. The light blue of the shallow Bahama banks contrasts with the darker hue of the deeper water especially in the Tongue of the Ocean area.

Pelagic sea snakes dehydrate at sea

PubMed Central

Lillywhite, Harvey B.; Sheehy, Coleman M.; Brischoux, François; Grech, Alana

2014-01-01

Secondarily marine vertebrates are thought to live independently of fresh water. Here, we demonstrate a paradigm shift for the widely distributed pelagic sea snake, Hydrophis (Pelamis) platurus, which dehydrates at sea and spends a significant part of its life in a dehydrated state corresponding to seasonal drought. Snakes that are captured following prolonged periods without rainfall have lower body water content, lower body condition and increased tendencies to drink fresh water than do snakes that are captured following seasonal periods of high rainfall. These animals do not drink seawater and must rehydrate by drinking from a freshwater lens that forms on the ocean surface during heavy precipitation. The new data based on field studies indicate unequivocally that this marine vertebrate dehydrates at sea where individuals may live in a dehydrated state for possibly six to seven months at a time. This information provides new insights for understanding water requirements of sea snakes, reasons for recent declines and extinctions of sea snakes and more accurate prediction for how changing patterns of precipitation might affect these and other secondarily marine vertebrates living in tropical oceans. PMID:24648228

Caspian Sea

NASA Technical Reports Server (NTRS)

2002-01-01

In this Moderate-resolution Imaging Spectroradiometer (MODIS) image from December 3, 2001, winter sea ice can be seen forming in the shallow waters of the northern Caspian (left) and Aral (upper right) Seas. Despite the inflow of the Volga River (upper left), the northern portion of the Caspian Sea averages only 17 feet in depth, and responds to the region's continental climate, which is cold in winter and hot and dry in the summer. The southern part of the Sea is deeper and remains ice-free throughout the winter. The dirty appearance of the ice may be due to sediment in the water, but may also be due to wind-driven dust. The wind in the region can blow at hurricane-force strength and can cause the ice to pile up in hummocks that are anchored to the sea bottom. The eastern portion of the Aral Sea is also beginning to freeze. At least two characteristics of the Aral Sea 'compete' in determining whether its waters will freeze. The Sea is shallow, which increases the likelihood of freezing, but it is also very salty, which means that lower temperatures are required to freeze it than would be required for fresh water. With average December temperatures of 18oF, it's clearly cold enough to allow ice to form. As the waters that feed the Aral Sea continue to be diverted for agriculture, the Sea becomes shallower and the regional climate becomes even more continental. This is because large bodies of water absorb and retain heat, moderating seasonal changes in temperature. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

The wind sea and swell waves climate in the Nordic seas

NASA Astrophysics Data System (ADS)

Semedo, Alvaro; Vettor, Roberto; Breivik, Øyvind; Sterl, Andreas; Reistad, Magnar; Soares, Carlos Guedes; Lima, Daniela

2015-02-01

A detailed climatology of wind sea and swell waves in the Nordic Seas (North Sea, Norwegian Sea, and Barents Sea), based on the high-resolution reanalysis NORA10, developed by the Norwegian Meteorological Institute, is presented. The higher resolution of the wind forcing fields, and the wave model (10 km in both cases), along with the inclusion of the bottom effect, allowed a better description of the wind sea and swell features, compared to previous global studies. The spatial patterns of the swell-dominated regional wave fields are shown to be different from the open ocean, due to coastal geometry, fetch dimensions, and island sheltering. Nevertheless, swell waves are still more prevalent and carry more energy in the Nordic Seas, with the exception of the North Sea. The influence of the North Atlantic Oscillation on the winter regional wind sea and swell patterns is also presented. The analysis of the decadal trends of wind sea and swell heights during the NORA10 period (1958-2001) shows that the long-term trends of the total significant wave height (SWH) in the Nordic Seas are mostly due to swell and to the wave propagation effect.

Gradient measurements of gaseous elemental mercury (Hg0) in the marine boundary layer of the northwest Sea of Japan (East Sea).

PubMed

Kalinchuk, Viktor; Lopatnikov, Evgeny; Astakhov, Anatoly

2018-06-01

Gaseous elemental mercury (Hg 0 ) is a prolific and persistent contaminant in the atmosphere. Atmospheric concentrations of Hg 0 were determined from 17 September to 7 October 2015 in the northwest Sea of Japan aboard the Russian research vessel Professor Gagarinsky. Simultaneous measurements of Hg 0 concentrations were performed 2 m and 20 m above the sea surface using automatic Hg 0 analysers RA-915M and RA-915+, respectively. Concentrations ranged from 0.3 to 25.9 ng/m 3 (n = 5207) and from 0.3 to 27.8 ng/m 3 (n = 4415), with medians of 1.7 and 1.6 ng/m 3 , respectively. Elevated Hg 0 was observed during three episodes from 19 to 22 September, likely caused by one or more of the following factors: 1) atmospheric transport of Hg 0 from the west and south-west (from N. Korea, China, and the Yellow Sea region); 2) Hg 0 emission from the sea due to pollution by water from the Tumannaya River; or 3) underwater geological activities. Increased Hg 0 concentration was observed during periods when air masses flowed from the south, and low concentrations were observed when air masses came from the north. A daytime increase of Hg 0 concentrations at a height of 2 m occurred simultaneously with decreasing Hg 0 at a height of 20 m. These diurnal variations suggest that two contrasting processes occur during the daytime in the marine boundary layer (MBL): Hg 0 emission from the sea surface and Hg 0 oxidation in the MBL by active halogens formed by photolysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Meteorological conditions influencing the formation of level ice within the Baltic Sea

NASA Astrophysics Data System (ADS)

Mazur, A. K.; Krezel, A.

2012-12-01

The Baltic Sea is covered by ice every winter and on average, the ice-covered area is 45% of the total area of the Baltic Sea. The beginning of ice season usually starts in the end of November, ice extent is the largest between mid-February and mid-March and sea ice disappears completely in May. The ice covered areas during a typical winter are the Gulf of Bothnia, the Gulf of Finland and the Gulf of Riga. The studies of sea ice in the Baltic Sea are related to two aspects: climate and marine transport. Depending on the local weather conditions during the winter different types of sea ice can be formed. From the point of winter shipping it is important to locate level and deformed ice areas (rafted ice, ridged ice, and hummocked ice). Because of cloud and daylight independency as well as good spatial resolution, SAR data seems to be the most suitable source of data for sea ice observation in the comparatively small area of the Baltic Sea. We used ASAR Wide Swath Mode data with spatial resolution 150 m. We analyzed data from the three winter seasons which were examples of severe, typical and mild winters. To remove the speckle effect the data were resampled to 250 m pixel size and filtred using Frost filter 5x5. To detect edges we used Sobel filter. The data were also converted into grayscale. Sea ice classification was based on Object-Based Image Analysis (OBIA). Object-based methods are not a common tool in sea ice studies but they seem to accurately separate level ice within the ice pack. The data were segmented and classified using eCognition Developer software. Level ice were classified based on texture features defined by Haralick (Grey Level Co-Occurrence Matrix homogeneity, GLCM contrast, GLCM entropy and GLCM correlation). The long-term changes of the Baltic Sea ice conditions have been already studied. They include date of freezing, date of break-up, sea ice extent and some of work also ice thickness. There is a little knowledge about the relationship of

Benthic community structures in the North Sea

NASA Astrophysics Data System (ADS)

Heip, C.; Craeymeersch, J. A.

1995-03-01

Coherent assemblages of marine benthic species have been recognized from the early twentieth century, and the classical papers of Petersen (1914, 1918) were based on studies of limited areas in the North Sea. In 1986, a synoptic survey of the North Sea north to 57°N was undertaken by a group of ten laboratories from seven North Sea countries. The results of this survey have recently been published (Heip et al., 1992a, b; Künitzer et al., 1992; Huys et al., 1992), and some of the results are summarized in this paper. The analysis of the macrofauna is based on slightly more than 700 taxa. In general, the North Sea macrofauna consists of northern species extending south to the northern margins of the Dogger Bank, and southern species extending north to the 100 m depth line. The central North Sea is an area of overlap of southern and northern species, especially around the 70 m depth contour. Consistent groupings of species are recognized that were summarized in seven faunal groupings. Macrofaunal body weight, density and diversity increase linearly towards the north. Macrofaunal biomass for the whole area averages 7 g adwt. m-2 and decreases from south to north. Distribution patterns and trends within the meiofauna were very different. Nematodes, which are the dominant taxon overall, are least abundant in the sandy sediments of the Southern Bight, then increase to a maximum around 53° 30' N and slowly decrease again towards the north. Copepod density and diversity are highest in the Southern Bight, due to the presence of many interstitial species. A large number of species new to science were recorded by the North Sea Benthos Survey and about 1500 species are expected to occur. Copepods show very distinct assemblages according to water depth and sediment type. The contrasting patterns in latitudinal gradients of body weight and number of species of macro- and meiofauna can be only partially explained. Latitude and sediment characteristics, such as grain size and

Alaska: Beaufort Sea

Atmospheric Science Data Center

2014-05-15

... Imaging SpectroRadiometer (MISR), illustrate different methods that may be used to assess sea ice type. Sea ice in the Beaufort Sea ... March 19, 2001 - Illustration of different methods to assess sea ice type. project:  MISR ...

Sea ice dynamics across the Mid-Pleistocene transition in the Bering Sea.

PubMed

Detlef, H; Belt, S T; Sosdian, S M; Smik, L; Lear, C H; Hall, I R; Cabedo-Sanz, P; Husum, K; Kender, S

2018-03-05

Sea ice and associated feedback mechanisms play an important role for both long- and short-term climate change. Our ability to predict future sea ice extent, however, hinges on a greater understanding of past sea ice dynamics. Here we investigate sea ice changes in the eastern Bering Sea prior to, across, and after the Mid-Pleistocene transition (MPT). The sea ice record, based on the Arctic sea ice biomarker IP 25 and related open water proxies from the International Ocean Discovery Program Site U1343, shows a substantial increase in sea ice extent across the MPT. The occurrence of late-glacial/deglacial sea ice maxima are consistent with sea ice/land ice hysteresis and land-glacier retreat via the temperature-precipitation feedback. We also identify interactions of sea ice with phytoplankton growth and ocean circulation patterns, which have important implications for glacial North Pacific Intermediate Water formation and potentially North Pacific abyssal carbon storage.

Comparison of hospitalization among German coastal and deep sea fishermen.

PubMed

Oldenburg, M; Harth, V; Manuwald, U

2015-08-01

This study aims to compare the hospitalization of German fishermen employed on German-flagged fishing vessels with that of the general German population in consideration of differences between coastal and deep sea fishery. By means of a database from the health insurance company for seafarers, diagnoses of German fishermen treated in German hospitals were determined from January 1997 to December 2007. Compared with the general German population, the fishermen's risk for specific diseases leading to hospitalization was calculated as standardized hospitalization ratio (SHR). Compared with the German reference population, German fishermen showed a considerably high SHR for malignant neoplasms at all sites (SHR 1.46; 95% CI 1.37-1.56), for respiratory cancer, and for non-Hodgkin lymphoma (NHL). Furthermore, they had more often been hospitalized due to diabetes mellitus, diseases of the respiratory and digestive systems as well as due to injury and poisoning. The risk for respiratory cancer and NHL among coastal fishermen exceeded that of deep sea fishermen, whereas the latter displayed a considerably higher SHR for diabetes mellitus, diseases of the respiratory system and metabolic and nutritional disorders. In contrast, the SHR for hypertensive and ischemic heart diseases was decreased among deep sea fishermen. Less qualified deep sea fishermen displayed a considerably higher SHR for malignant neoplasms at all sites than more highly qualified ones. Fishery is still an occupation which poses a high risk for malignant neoplasms and injuries. This is likely due to lifestyle and work-related factors. Further studies are needed to evaluate the different working and living conditions of coastal and deep sea fishermen.

Recent 121-year variability of western boundary upwelling in the northern South China Sea

NASA Astrophysics Data System (ADS)

Liu, Yi; Peng, Zicheng; Shen, Chuan-Chou; Zhou, Renjun; Song, Shaohua; Shi, Zhengguo; Chen, Tegu; Wei, Gangjian; Delong, Kristine L.

2013-06-01

upwelling is typically related to the eastern boundary upwelling system, whereas the powerful southwest Asian summer monsoon can also generate significant cold, nutrient-rich deep water in western coastal zones. Here we present a sea surface temperature record (A.D. 1876-1996) derived from coral Porites Sr/Ca for an upwelling zone in the northern South China Sea. The upwelling-induced sea surface temperature anomaly record reveals prominent multidecadal variability driven by Asian summer monsoon dynamics with an abrupt transition from warmer to colder conditions in 1930, and a return to warmer conditions after 1960. Previous studies suggest the expected increase in atmospheric CO2 for the coming decades may result in intensification in the eastern boundary upwelling system, which could enhance upwelling of CO2-rich deep water thus exacerbating the impact of acidification in these productive zones. In contrast, the weakening trend since 1961 in the upwelling time series from the northern South China Sea suggests moderate regional ocean acidification from upwelling thus a stress relief for marine life in this region.

Silver nanoparticles and dissolved silver activate contrasting immune responses and stress-induced heat shock protein expression in sea urchin.

PubMed

Magesky, Adriano; de Oliveira Ribeiro, Ciro A; Beaulieu, Lucie; Pelletier, Émilien

2017-07-01

Using immune cells of sea urchin Strongylocentrotus droebachiensis in early development as a model, the cellular protective mechanisms against ionic and poly(allylamine)-coated silver nanoparticle (AgNPs; 14 ± 6 nm) treatments at 100 μg L -1 were investigated. Oxidative stress, heat shock protein expression, and pigment production by spherulocytes were determined as well as AgNP translocation pathways and their multiple effects on circulating coelomocytes. Sea urchins showed an increasing resilience to Ag over time because ionic Ag is accumulated in a steady way, although nanoAg levels dropped between 48 h and 96 h. A clotting reaction emerged on tissues injured by dissolved Ag (present as chloro-complexes in seawater) between 12 h and 48 h. Silver contamination and nutritional state influenced the production of reactive oxygen species. After passing through coelomic sinuses and gut, AgNPs were found in coelomocytes. Inside blood vessels, apoptosis-like processes appeared in coelomocytes highly contaminated by poly(allylamine)-coated AgNPs. Increasing levels of Ag accumulated by urchins once exposed to AgNPs pointed to a Trojan-horse mechanism operating over 12-d exposure. However, under short-term treatments, physical interactions of poly(allylamine)-coated AgNPs with cell structures might be, at some point, predominant and responsible for the highest levels of stress-related proteins detected. The present study is the first report detailing nano-translocation in a marine organism and multiple mechanisms by which sea urchin cells can deal with toxic AgNPs. Environ Toxicol Chem 2017;36:1872-1886. © 2016 SETAC. © 2016 SETAC.

Polar Seas Oceanography: An Integrated Case Study of the Kara Sea

NASA Astrophysics Data System (ADS)

Harms, Ingo

2004-02-01

What strikes first when browsing through this book is that the main title is misleading. Polar Seas Oceanography is, first of all, a book on ``an integrated case study of the Kara Sea,'' as the subtitle says. For readers who are interested more generally in polar oceanography, the book is probably the wrong choice. The Kara Sea is a rather shallow shelf sea within the Arctic Ocean, located between the Barents Sea to the west and the Laptev Sea to the east. The importance of the Kara Sea is manifold: climate change issues like ice formation and freshwater runoff, environmental problems from dumping of radioactive waste or oil exploitation, and finally, the Northern Sea route, which crosses large parts of the Kara Sea, underline the economical and ecological relevance of that region. In spite of severe climate conditions, the Kara Sea is relatively well investigated. This was achieved through intense oceanographic expeditions, aircraft surveys, and polar drift stations. Russian scientists from the Arctic and Antarctic Research Institute (AARI) carried out a major part of this outstanding work during the second half of the last century.

SIPEX 2012: Extreme sea-ice and atmospheric conditions off East Antarctica

NASA Astrophysics Data System (ADS)

Heil, P.; Stammerjohn, S.; Reid, P.; Massom, R. A.; Hutchings, J. K.

2016-09-01

In 2012, Antarctic sea-ice coverage was marked by weak annual-mean climate anomalies that consisted of opposing anomalies early and late in the year (some setting new records) which were interspersed by near-average conditions for most of the austral autumn and winter. Here, we investigate the ocean-ice-atmosphere system off East Antarctica, prior to and during the Sea Ice Physics and Ecosystems eXperiment [SIPEX] 2012, by exploring relationships between atmospheric and oceanic forcing together with the sea-ice and snow characteristics. During August and September 2012, just prior to SIPEX 2012, atmospheric circulation over the Southern Ocean was near-average, setting up the ocean-ice-atmosphere system for near-average conditions. However, below-average surface pressure and temperature as well as strengthened circumpolar winds prevailed during June and July 2012. This led to a new record (19.48×106 km2) in maximum Antarctic sea-ice extent recorded in late September. In contrast to the weak circum-Antarctic conditions, the East Antarctic sector (including the SIPEX 2012 region) experienced positive sea-ice extent and concentration anomalies during most of 2012, coincident with negative atmospheric pressure and sea-surface temperature anomalies. Heavily deformed sea ice appeared to be associated with intensified wind stress due to increased cyclonicity as well as an increased influx of sea ice from the east. This increased westward ice flux is likely linked to the break-up of nearly 80% of the Mertz Glacier Tongue in 2010, which strongly modified the coastal configuration and hence the width of the westward coastal current. Combined with favourable atmospheric conditions the associated changed coastal configuration allowed more sea ice to remain within the coastal current at the expense of a reduced northward flow in the region around 141°-145°E. In addition a westward propagating positive anomaly of sea-ice extent from the western Ross Sea during austral winter

Parasites and Holocene sea-level rise: Recurrent upsurges in trematode infestation linked to repeated flooding events in the Adriatic Sea

NASA Astrophysics Data System (ADS)

Scarponi, Daniele; Azzarone, Michele; Kowalewski, Michał; Huntley, John Warren

2017-04-01

The accelerating increase in global temperature and concomitant sea level rise may result in an increased prevalence (i.e. infestation frequency) of many pathogens and parasites. Using the Holocene brackish deposits of the Po Plain, we evaluate this issue from a historical perspective by documenting temporal changes in trematode infestation of mollusk hosts during high-frequency (102-103 yrs) sea-level fluctuations that took place over the most recent millennia. During that time interval, the dominant bivalve species, Abra segmentum, was frequently infested by trematodes. Median body size was significantly larger in infested individuals (p = 2.21*10-34), likely reflecting accumulation of parasites with ontogenetic age. Prevalence estimates were significantly elevated (p < 0.01) in samples of A. segmentum associated with flooding surfaces and significantly depressed (p < 0.01) in intervening samples. In contrast, temporal trends in host body size, host availability, salinity, diversity, turnover, and community structure did not correlate significantly with parasite prevalence. The results reported here reinforce the recently proposed hypothesis that increasing trematode prevalence is linked to flooding events, a pattern now documented in shallow marine and estuarine settings on two continents, in both modern and fossil taxa. Consequently, the ongoing anthropogenic warming and sea-level rise is expected to trigger a significant upsurge in trematode prevalence, resulting in suppressed fecundity of common benthic organisms and negative impacts on marine ecosystems and ecosystem services.

Conquered from the deep sea? A new deep-sea isopod species from the Antarctic shelf shows pattern of recent colonization.

PubMed

Riehl, Torben; Kaiser, Stefanie

2012-01-01

The Amundsen Sea, Antarctica, is amongst the most rapidly changing environments of the world. Its benthic inhabitants are barely known and the BIOPEARL 2 project was one of the first to biologically explore this region. Collected during this expedition, Macrostylis roaldi sp. nov. is described as the first isopod discovered on the Amundsen-Sea shelf. Amongst many characteristic features, the most obvious characters unique for M. roaldi are the rather short pleotelson and short operculum as well as the trapezoid shape of the pleotelson in adult males. We used DNA barcodes (COI) and additional mitochondrial markers (12S, 16S) to reciprocally illuminate morphological results and nucleotide variability. In contrast to many other deep-sea isopods, this species is common and shows a wide distribution. Its range spreads from Pine Island Bay at inner shelf right to the shelf break and across 1,000 m bathymetrically. Its gene pool is homogenized across space and depth. This is indicative for a genetic bottleneck or a recent colonization history. Our results suggest further that migratory or dispersal capabilities of some species of brooding macrobenthos have been underestimated. This might be relevant for the species' potential to cope with effects of climate change. To determine where this species could have survived the last glacial period, alternative refuge possibilities are discussed.

Acceleration of Sea Level Rise Over Malaysian Seas from Satellite Altimeter

NASA Astrophysics Data System (ADS)

Hamid, A. I. A.; Din, A. H. M.; Khalid, N. F.; Omar, K. M.

2016-09-01

Sea level rise becomes our concern nowadays as a result of variously contribution of climate change that cause by the anthropogenic effects. Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. Due to this change, sea level is now constantly rising and eventually will threaten many low-lying and unprotected coastal areas in many ways. This paper is proposing a significant effort to quantify the sea level trend over Malaysian seas based on the combination of multi-mission satellite altimeters over a period of 23 years. Eight altimeter missions are used to derive the absolute sea level from Radar Altimeter Database System (RADS). Data verification is then carried out to verify the satellite derived sea level rise data with tidal data. Eight selected tide gauge stations from Peninsular Malaysia, Sabah and Sarawak are chosen for this data verification. The pattern and correlation of both measurements of sea level anomalies (SLA) are evaluated over the same period in each area in order to produce comparable results. Afterwards, the time series of the sea level trend is quantified using robust fit regression analysis. The findings clearly show that the absolute sea level trend is rising and varying over the Malaysian seas with the rate of sea level varies and gradually increase from east to west of Malaysia. Highly confident and correlation level of the 23 years measurement data with an astonishing root mean square difference permits the absolute sea level trend of the Malaysian seas has raised at the rate 3.14 ± 0.12 mm yr-1 to 4.81 ± 0.15 mm yr-1 for the chosen sub-areas, with an overall mean of 4.09 ± 0.12 mm yr-1. This study hopefully offers a beneficial sea level information to be applied in a wide range of related environmental and climatology issue such as flood and global warming.

Filamentous phages prevalent in Pseudoalteromonas spp. confer properties advantageous to host survival in Arctic sea ice

PubMed Central

Yu, Zi-Chao; Chen, Xiu-Lan; Shen, Qing-Tao; Zhao, Dian-Li; Tang, Bai-Lu; Su, Hai-Nan; Wu, Zhao-Yu; Qin, Qi-Long; Xie, Bin-Bin; Zhang, Xi-Ying; Yu, Yong; Zhou, Bai-Cheng; Chen, Bo; Zhang, Yu-Zhong

2015-01-01

Sea ice is one of the most frigid environments for marine microbes. In contrast to other ocean ecosystems, microbes in permanent sea ice are space confined and subject to many extreme conditions, which change on a seasonal basis. How these microbial communities are regulated to survive the extreme sea ice environment is largely unknown. Here, we show that filamentous phages regulate the host bacterial community to improve survival of the host in permanent Arctic sea ice. We isolated a filamentous phage, f327, from an Arctic sea ice Pseudoalteromonas strain, and we demonstrated that this type of phage is widely distributed in Arctic sea ice. Growth experiments and transcriptome analysis indicated that this phage decreases the host growth rate, cell density and tolerance to NaCl and H2O2, but enhances its motility and chemotaxis. Our results suggest that the presence of the filamentous phage may be beneficial for survival of the host community in sea ice in winter, which is characterized by polar night, nutrient deficiency and high salinity, and that the filamentous phage may help avoid over blooming of the host in sea ice in summer, which is characterized by polar day, rich nutrient availability, intense radiation and high concentration of H2O2. Thus, while they cannot kill the host cells by lysing them, filamentous phages confer properties advantageous to host survival in the Arctic sea ice environment. Our study provides a foremost insight into the ecological role of filamentous phages in the Arctic sea ice ecosystem. PMID:25303713

The Cytotoxicity and Genotoxicity of Hexavalent Chromium in Steller Sea Lion Lung Fibroblasts Compared to Human Lung Fibroblasts

PubMed Central

Wise, John Pierce; Wise, Sandra S.; Holmes, Amie L.; LaCerte, Carolyne; Shaffiey, Fariba; Aboueissa, AbouEl-Makarim

2010-01-01

In this study we directly compared soluble and particulate chromate cytotoxicity and genotoxicity in human (Homo sapiens) and sea lion (Eumetopias jubatus) lung fibroblasts. Our results show that hexavalent chromium induces increased cell death and chromosome damage in both human and sea lion cells with increasing intracellular chromium ion levels. The data further indicate that both sodium chromate and lead chromate are less cytotoxic and genotoxic to sea lion cells than human cells, based on administered dose. Differences in chromium ion uptake explained some but not all of the reduced amounts of sodium chromate-induced cell death. By contrast, uptake differences could explain the differences in sodium chromate-induced chromosome damage and particulate chromate-induced toxicity. Altogether they indicate that while hexavalent chromium induces similar toxic effects in sea lion and human cells, there are different mechanisms underlying the toxic outcomes. PMID:20211760

Physical-biological coupling in the Amundsen Sea, Antarctica: Influence of physical factors on phytoplankton community structure and biomass

NASA Astrophysics Data System (ADS)

Lee, Youngju; Yang, Eun Jin; Park, Jisoo; Jung, Jinyoung; Kim, Tae Wan; Lee, SangHoon

2016-11-01

To understand the spatial distribution of phytoplankton communities in various habitats in the Amundsen Sea, western Antarctica, a field survey was conducted at 15 stations during the austral summer, from December 2013 to January 2014. Water samples were analyzed by microscopy. We found high phytoplankton abundance and biomass in the Amundsen Sea polynya (ASP). Their strong positive correlation with water temperature suggests that phytoplankton biomass accumulated in the surface layer of the stratified polynya. In the ASP, the predominant phytoplankton species was Phaeocystis antarctica, while diatoms formed a major group in the sea ice zone, especially Fragilariopsis spp., Chaetoceros spp., and Proboscia spp. Although this large diatom abundance sharply decreased just off the marginal sea ice zone, weakly silicified diatoms, due to their high buoyancy, were distributed at almost all stations on the continental shelf. Dictyocha speculum appeared to favor the area between the marginal sea ice zone and the ASP in contrast to cryptophytes and picophytoplankton, whose abundance was higher in the area between the continental shelf and the open ocean of Amundsen Sea. Several environmental factors were found to affect the spatial variation of phytoplankton species, but the community structure appeared to be controlled mainly by the seawater density related to sea-ice melting and water circulation in the Amundsen Sea.

Fast Response of the Tropics to an Abrupt Loss of Arctic Sea Ice via Ocean Dynamics

NASA Astrophysics Data System (ADS)

Wang, Kun; Deser, Clara; Sun, Lantao; Tomas, Robert A.

2018-05-01

The role of ocean dynamics in the transient adjustment of the coupled climate system to an abrupt loss of Arctic sea ice is investigated using experiments with Community Climate System Model version 4 in two configurations: a thermodynamic slab mixed layer ocean and a full-depth ocean that includes both dynamics and thermodynamics. Ocean dynamics produce a distinct sea surface temperature warming maximum in the eastern equatorial Pacific, accompanied by an equatorward intensification of the Intertropical Convergence Zone and Hadley Circulation. These tropical responses are established within 25 years of ice loss and contrast markedly with the quasi-steady antisymmetric coupled response in the slab-ocean configuration. A heat budget analysis reveals the importance of anomalous vertical advection tied to a monotonic temperature increase below 200 m for the equatorial sea surface temperature warming maximum in the fully coupled model. Ocean dynamics also rapidly modify the midlatitude atmospheric response to sea ice loss.

A near uniform basin-wide sea level fluctuation over the Japan/East Sea: A semienclosed sea with multiple straits

NASA Astrophysics Data System (ADS)

Kim, Seung-Bum; Fukumori, Ichiro

2008-06-01

Sea level of the Japan/East Sea observed by the TOPEX/Poseidon (T/P) satellite altimeter is analyzed using a 1/4°-resolution ocean general circulation model. A significant fraction of the Japan/East Sea sea level variability is found to be spatially uniform with periods ranging from 20 d to a year. The model simulation is consistent with T/P records in terms of the basin-wide sea level fluctuation's spectral energy and coherence. The simulation indicates that the changes are barotropic in nature and controlled, notably at high frequencies, by the net mass transport through the straits of the Japan/East Sea driven by winds in the vicinity of the Korea/Tsushima and Soya Straits. A series of barotropic simulations suggest that the sea level fluctuations are the result of a dynamic balance at the straits among near-strait winds, friction, and geostrophic control. The basin-wide sea level response is a linear superposition of changes due to winds near the individual straits. In particular, a basin-wide sea level response can be established by winds near either one of the straits alone. For the specific geometry and winds, winds near the Soya Strait have a larger impact on the Japan/East Sea mean sea level than those near the Korea/Tsushima Strait.

Red Sea

Atmospheric Science Data Center

2013-04-16

article title:  The Red Sea     View Larger Image ... Imaging SpectroRadiometer (MISR) image of the Red Sea was acquired on August 13, 2000. Located between the East African coast and the Saudi Arabian peninsula, the Red Sea got its name because the blooms of a type of algae,  Trichodesmium ...

Chemical Composition of Sea Fog Water Along the South China Sea

NASA Astrophysics Data System (ADS)

Yue, Yanyu; Niu, Shengjie; Zhao, Lijuan; Zhang, Yu; Xu, Feng

2012-12-01

The chemical and microphysical properties of sea fog were measured during a field experiment on Donghai Island, Zhanjiang of China from March 15 to April 18, 2010. The average pH and electrical conductivity (EC) value of the six sea fog cases during the experiment was 5.2 and 1,884 μS/cm. The observed total ion concentration of sea fog was four orders of magnitude higher than those in the North Pacific and other sea areas of China. The dominant anion and cation in all sea fog water samples were Cl- and Na+, respectively. From backward trajectory analysis and ion loading computation, it can be concluded that the ions in the samples were transported either from pollutants in distant industrial cities or from local ion deposition processes. The concentration of Ca2+ in the sea fog water samples in Case 2 suggested that a dust storm in the Inner Mongolia, a northern region of China several thousand kilometers away, could reach the South China Sea. The data also showed that the sea fog droplet spectrum over the South China Sea is unimodal. Through relationship analysis, it is illustrated that the evolution of microphysics (such as droplet concentration, diameter, and liquid water content) during fog process could affect the chemical properties of sea fog.

The Adriatic Sea: A Long-Standing Laboratory for Sea Level Studies

NASA Astrophysics Data System (ADS)

Vilibić, Ivica; Šepić, Jadranka; Pasarić, Mira; Orlić, Mirko

2017-10-01

The paper provides a comprehensive review of all aspects of Adriatic Sea level research covered by the literature. It discusses changes occurring over millennial timescales and documented by a variety of natural and man-made proxies and post-glacial rebound models; mean sea level changes occurring over centennial to annual timescales and measured by modern instruments; and daily and higher-frequency changes (with periods ranging from minutes to a day) that are contributing to sea level extremes and are relevant for present-day flooding of coastal areas. Special tribute is paid to the historic sea level studies that shaped modern sea level research in the Adriatic, followed by a discussion of existing in situ and remote sensing observing systems operating in the Adriatic area, operational forecasting systems for Adriatic storm surges, as well as warning systems for tsunamis and meteotsunamis. Projections and predictions of sea level and related hazards are also included in the review. Based on this review, open issues and research gaps in the Adriatic Sea level studies are identified, as well as the additional research efforts needed to fill the gaps. The Adriatic Sea, thus, remains a laboratory for coastal sea level studies for semi-enclosed, coastal and marginal seas in the world ocean.

Pitfalls in velocity analysis for strongly contrasting, layered media - Example from the Chalk Group, North Sea

NASA Astrophysics Data System (ADS)

Montazeri, Mahboubeh; Uldall, Anette; Moreau, Julien; Nielsen, Lars

2018-02-01

Knowledge about the velocity structure of the subsurface is critical in key seismic processing sequences, for instance, migration, depth conversion, and construction of initial P- and S-wave velocity models for full-waveform inversion. Therefore, the quality of subsurface imaging is highly dependent upon the quality of the seismic velocity analysis. Based on a case study from the Danish part of the North Sea, we show how interference caused by multiples, converted waves, and thin-layer effects may lead to incorrect velocity estimation, if such effects are not accounted for. Seismic wave propagation inside finely layered reservoir rocks dominated by chalk is described by two-dimensional finite-difference wave field simulation. The rock physical properties used for the modeling are based on an exploration well from the Halfdan field in the Danish sector of the North Sea. The modeling results are compared to seismic data from the study area. The modeling shows that interference of primaries with multiples, converted waves and thin-bed effects can give rise to strong anomalies in standard velocity analysis plots. Consequently, root-mean-square (RMS) velocity profiles may be erroneously picked. In our study area, such mis-picking can introduce errors in, for example, the thickness estimation of the layers near the base of the studied sedimentary strata by 11% to 26%. Tests show that front muting and bandpass filtering cannot significantly improve the quality of velocity analysis in our study. However, we notice that spiking deconvolution applied before velocity analysis may to some extent reduce the impact of interference and, therefore, reduce the risk of erroneous picking of the velocity function.

The impact of ENSO on regional chlorophyll-a anomaly in the Arafura Sea

NASA Astrophysics Data System (ADS)

Dewi, D. M. P. R.; Fatmasari, D.; Kurniawan, A.; Munandar, M. A.

2018-03-01

The El Niño-Southern Oscillation (ENSO) is a naturally occurring phenomenon that involves fluctuating ocean temperature in the equatorial Pacific. ENSO influences ocean climate variability in Indonesia including the Arafura Sea. The relationship between oceanic chlorophyll-a and ENSO has been the focus of study over the past decade. Here we examine the impact of ENSO on regional chlorophyll-a anomaly in the Papua waters using 14 years of chlorophyll-a and sea surface temperature (SST) data from AQUA MODIS and sea level anomaly data from AVISO. It is found that when El Niño events occur the negative SST anomaly in the Papua waters as well as the enhanced upwelling cause the increase of chlorophyll-a concentration. The highest chlorophyll-a concentration (> 1 mg–cm-3) occured during El Niño and observed around the Aru archipelago. In contrast during La Niña event, the positive SST anomaly in Papua waters and the suppressed upwelling cause the decrease of chlorophyll-a concentration. Our results suggest that during El Niño (La Niña), the enhanced (suppressed) upwelling related to the significant decreasing (increasing) of sea level anomaly.

First biological measurements of deep-sea corals from the Red Sea.

PubMed

Roder, C; Berumen, M L; Bouwmeester, J; Papathanassiou, E; Al-Suwailem, A; Voolstra, C R

2013-10-03

It is usually assumed that metabolic constraints restrict deep-sea corals to cold-water habitats, with 'deep-sea' and 'cold-water' corals often used as synonymous. Here we report on the first measurements of biological characters of deep-sea corals from the central Red Sea, where they occur at temperatures exceeding 20°C in highly oligotrophic and oxygen-limited waters. Low respiration rates, low calcification rates, and minimized tissue cover indicate that a reduced metabolism is one of the key adaptations to prevailing environmental conditions. We investigated four sites and encountered six species of which at least two appear to be undescribed. One species is previously reported from the Red Sea but occurs in deep cold waters outside the Red Sea raising interesting questions about presumed environmental constraints for other deep-sea corals. Our findings suggest that the present understanding of deep-sea coral persistence and resilience needs to be revisited.

High-contrast multilayer imaging of biological organisms through dark-field digital refocusing.

PubMed

Faridian, Ahmad; Pedrini, Giancarlo; Osten, Wolfgang

2013-08-01

We have developed an imaging system to extract high contrast images from different layers of biological organisms. Utilizing a digital holographic approach, the system works without scanning through layers of the specimen. In dark-field illumination, scattered light has the main contribution in image formation, but in the case of coherent illumination, this creates a strong speckle noise that reduces the image quality. To remove this restriction, the specimen has been illuminated with various speckle-fields and a hologram has been recorded for each speckle-field. Each hologram has been analyzed separately and the corresponding intensity image has been reconstructed. The final image has been derived by averaging over the reconstructed images. A correlation approach has been utilized to determine the number of speckle-fields required to achieve a desired contrast and image quality. The reconstructed intensity images in different object layers are shown for different sea urchin larvae. Two multimedia files are attached to illustrate the process of digital focusing.

Changes provoked by boiling, steaming and sous-vide cooking in the lipid and volatile profile of European sea bass.

PubMed

Nieva-Echevarría, Bárbara; Manzanos, María J; Goicoechea, Encarnación; Guillén, María D

2017-09-01

This study aims to shed light on the changes provoked by boiling, steaming and sous-vide cooking on the lipids and volatile profile of farmed and wild European sea bass meat. None of the cooking techniques provoked changes due to hydrolytic or oxidation processes detectable by 1 H NMR on sea bass lipids. The lipid profile of main and minor lipidic components was maintained after cooking. However, study by SPME-GC/MS evidenced that steaming and sous-vide cooking modified the volatile profile of sea bass meat, especially in farmed specimens. The compounds generated came from the occurrence, to a very small extent, of lipid and protein degradation. By contrast, boiling scarcely modified the initial characteristics of raw sea bass. Thus, from a sensory point of view and considering the odour-active compounds generated, steaming and sous-vide cooking provoked more noticeable changes than boiling, especially in farmed sea bass meat. Copyright © 2017. Published by Elsevier Ltd.

From Offshore to Onshore: Multiple Origins of Shallow-Water Corals from Deep-Sea Ancestors

PubMed Central

Lindner, Alberto; Cairns, Stephen D.; Cunningham, Clifford W.

2008-01-01

Shallow-water tropical reefs and the deep sea represent the two most diverse marine environments. Understanding the origin and diversification of this biodiversity is a major quest in ecology and evolution. The most prominent and well-supported explanation, articulated since the first explorations of the deep sea, holds that benthic marine fauna originated in shallow, onshore environments, and diversified into deeper waters. In contrast, evidence that groups of marine organisms originated in the deep sea is limited, and the possibility that deep-water taxa have contributed to the formation of shallow-water communities remains untested with phylogenetic methods. Here we show that stylasterid corals (Cnidaria: Hydrozoa: Stylasteridae)—the second most diverse group of hard corals—originated and diversified extensively in the deep sea, and subsequently invaded shallow waters. Our phylogenetic results show that deep-water stylasterid corals have invaded the shallow-water tropics three times, with one additional invasion of the shallow-water temperate zone. Our results also show that anti-predatory innovations arose in the deep sea, but were not involved in the shallow-water invasions. These findings are the first robust evidence that an important group of tropical shallow-water marine animals evolved from deep-water ancestors. PMID:18560569

Sea Surface Scanner: An advanced catamaran to study the sea surface

NASA Astrophysics Data System (ADS)

Wurl, O.; Mustaffa, N. I. H.; Ribas Ribas, M.

2016-02-01

The Sea Surface Scanner is a remote-controlled catamaran with the capability to sample the sea-surface microlayer in high resolution. The catamaran is equipped with a suite of sensors to scan the sea surface on chemical, biological and physical parameters. Parameters include UV absorption, fluorescence spectra, chlorophyll-a, photosynthetic efficiency, chromophoric dissolved organic matter (CDOM), dissolved oxygen, pH, temperature, and salinity. A further feature is a capability to collect remotely discrete water samples for detailed lab analysis. We present the first high-resolution (< 30 sec) data on the sea surface microlayer. We discuss the variability of biochemical properties of the sea surface and its implication on air-sea interaction.

Is the detection of accelerated sea level rise imminent?

DOE PAGES

Fasullo, J. T.; Nerem, R. S.; Hamlington, B.

2016-08-10

Global mean sea level rise estimated from satellite altimetry provides a strong constraint on climate variability and change and is expected to accelerate as the rates of both ocean warming and cryospheric mass loss increase over time. In stark contrast to this expectation however, current altimeter products show the rate of sea level rise to have decreased from the first to second decades of the altimeter era. Here, a combined analysis of altimeter data and specially designed climate model simulations shows the 1991 eruption of Mt Pinatubo to likely have masked the acceleration that would have otherwise occurred. This maskingmore » arose largely from a recovery in ocean heat content through the mid to late 1990 s subsequent to major heat content reductions in the years following the eruption. As a result, a consequence of this finding is that barring another major volcanic eruption, a detectable acceleration is likely to emerge from the noise of internal climate variability in the coming decade.« less

Is the detection of accelerated sea level rise imminent?

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

Fasullo, J. T.; Nerem, R. S.; Hamlington, B.

Global mean sea level rise estimated from satellite altimetry provides a strong constraint on climate variability and change and is expected to accelerate as the rates of both ocean warming and cryospheric mass loss increase over time. In stark contrast to this expectation however, current altimeter products show the rate of sea level rise to have decreased from the first to second decades of the altimeter era. Here, a combined analysis of altimeter data and specially designed climate model simulations shows the 1991 eruption of Mt Pinatubo to likely have masked the acceleration that would have otherwise occurred. This maskingmore » arose largely from a recovery in ocean heat content through the mid to late 1990 s subsequent to major heat content reductions in the years following the eruption. As a result, a consequence of this finding is that barring another major volcanic eruption, a detectable acceleration is likely to emerge from the noise of internal climate variability in the coming decade.« less

Results of the Sea Ice Model Intercomparison Project: Evaluation of sea ice rheology schemes for use in climate simulations

NASA Astrophysics Data System (ADS)

Kreyscher, Martin; Harder, Markus; Lemke, Peter; Flato, Gregory M.

2000-05-01

A hierarchy of sea ice rheologies is evaluated on the basis of a comprehensive set of observational data. The investigations are part of the Sea Ice Model Intercomparison Project (SIMIP). Four different sea ice rheology schemes are compared: a viscous-plastic rheology, a cavitating-fluid model, a compressible Newtonian fluid, and a simple free drift approach with velocity correction. The same grid, land boundaries, and forcing fields are applied to all models. As verification data, there are (1) ice thickness data from upward looking sonars (ULS), (2) ice concentration data from the passive microwave radiometers SMMR and SSM/I, (3) daily buoy drift data obtained by the International Arctic Buoy Program (IABP), and (4) satellite-derived ice drift fields based on the 85 GHz channel of SSM/I. All models are optimized individually with respect to mean drift speed and daily drift speed statistics. The impact of ice strength on the ice cover is best revealed by the spatial pattern of ice thickness, ice drift on different timescales, daily drift speed statistics, and the drift velocities in Fram Strait. Overall, the viscous-plastic rheology yields the most realistic simulation. In contrast, the results of the very simple free-drift model with velocity correction clearly show large errors in simulated ice drift as well as in ice thicknesses and ice export through Fram Strait compared to observation. The compressible Newtonian fluid cannot prevent excessive ice thickness buildup in the central Arctic and overestimates the internal forces in Fram Strait. Because of the lack of shear strength, the cavitating-fluid model shows marked differences to the statistics of observed ice drift and the observed spatial pattern of ice thickness. Comparison of required computer resources demonstrates that the additional cost for the viscous-plastic sea ice rheology is minor compared with the atmospheric and oceanic model components in global climate simulations.

Atmospheric forcing of sea ice anomalies in the Ross Sea Polynya region

NASA Astrophysics Data System (ADS)

Dale, Ethan; McDonald, Adrian; Rack, Wolfgang

2016-04-01

Despite warming trends in global temperatures, sea ice extent in the southern hemisphere has shown an increasing trend over recent decades. Wind-driven sea ice export from coastal polynyas is an important source of sea ice production. Areas of major polynyas in the Ross Sea, the region with largest increase in sea ice extent, have been suggested to produce the vast amount of the sea ice in the region. We investigate the impacts of strong wind events on polynyas and the subsequent sea ice production. We utilize Bootstrap sea ice concentration (SIC) measurements derived from satellite based, Special Sensor Microwave Imager (SSM/I) brightness temperature images. These are compared with surface wind measurements made by automatic weather stations of the University of Wisconsin-Madison Antarctic Meteorology Program. Our analysis focusses on the winter period defined as 1st April to 1st November in this study. Wind data was used to classify each day into characteristic regimes based on the change of wind speed. For each regime, a composite of SIC anomaly was formed for the Ross Sea region. We found that persistent weak winds near the edge of the Ross Ice Shelf are generally associated with positive SIC anomalies in the Ross Sea polynya area (RSP). Conversely we found negative SIC anomalies in this area during persistent strong winds. By analyzing sea ice motion vectors derived from SSM/I brightness temperatures, we find significant sea ice motion anomalies throughout the Ross Sea during strong wind events. These anomalies persist for several days after the strong wing event. Strong, negative correlations are found between SIC within the RSP and wind speed indicating that strong winds cause significant advection of sea ice in the RSP. This rapid decrease in SIC is followed by a more gradual recovery in SIC. This increase occurs on a time scale greater than the average persistence of strong wind events and the resulting Sea ice motion anomalies, highlighting the production

Highly variable Pliocene sea surface conditions in the Norwegian Sea

NASA Astrophysics Data System (ADS)

Bachem, Paul E.; Risebrobakken, Bjørg; De Schepper, Stijn; McClymont, Erin L.

2017-09-01

The Pliocene was a time of global warmth with small sporadic glaciations, which transitioned towards the larger-scale Pleistocene glacial-interglacial variability. Here, we present high-resolution records of sea surface temperature (SST) and ice-rafted debris (IRD) in the Norwegian Sea from 5.32 to 3.14 Ma, providing evidence that the Pliocene surface conditions of the Norwegian Sea underwent a series of transitions in response to orbital forcing and gateway changes. Average SSTs are 2 °C above the regional Holocene mean, with notable variability on millennial to orbital timescales. Both gradual changes and threshold effects are proposed for the progression of regional climate towards the Late Pliocene intensification of Northern Hemisphere glaciation. Cooling from 4.5 to 4.3 Ma may be linked to the onset of poleward flow through the Bering Strait. This cooling was further intensified by a period of cool summers due to weak obliquity forcing. A 7 °C warming of the Norwegian Sea at 4.0 Ma suggests a major increase in northward heat transport from the North Atlantic, leading to an enhanced zonal SST gradient in the Nordic Seas, which may be linked to the expansion of sea ice in the Arctic and Nordic Seas. A warm Norwegian Sea and enhanced zonal temperature gradient between 4.0 and 3.6 Ma may have been a priming factor for increased glaciation around the Nordic Seas due to enhanced evaporation and precipitation at high northern latitudes.

Sea ice concentration temporal variability over the Weddell Sea and its relationship with tropical sea surface temperature

USGS Publications Warehouse

Barreira, S.; Compagnucci, R.

2007-01-01

Principal Components Analysis (PCA) in S-Mode (correlation between temporal series) was performed on sea ice monthly anomalies, in order to investigate which are the main temporal patterns, where are the homogenous areas located and how are they related to the sea surface temperature (SST). This analysis provides 9 patterns (4 in the Amundsen and Bellingshausen Seas and 5 in the Weddell Sea) that represent the most important temporal features that dominated sea ice concentration anomalies (SICA) variability in the Weddell, Amundsen and Bellingshausen Seas over the 1979-2000 period. Monthly Polar Gridded Sea Ice Concentrations data set derived from satellite information generated by NASA Team algorithm and acquired from the National Snow and Ice Data Center (NSIDC) were used. Monthly means SST are provided by the National Center for Environmental Prediction reanalysis. The first temporal pattern series obtained by PCA has its homogeneous area located at the external region of the Weddell and Bellingshausen Seas and Drake Passage, mostly north of 60°S. The second region is centered in 30°W and located at the southeast of the Weddell. The third area is localized east of 30°W and north of 60°S. South of the first area, the fourth PC series has its homogenous region, between 30° and 60°W. The last area is centered at 0° W and south of 60°S. Correlation charts between the five Principal Components series and SST were performed. Positive correlations over the Tropical Pacific Ocean were found for the five PCs when SST series preceded SICA PC series. The sign of the correlation could relate the occurrence of an El Niño/Southern Oscillation (ENSO) warm (cold) event with posterior positive (negative) anomalies of sea ice concentration over the Weddell Sea.

Spatial heterogeneity in parasite infections at different spatial scales in an intertidal bivalve.

PubMed

Thieltges, David W; Reise, Karsten

2007-01-01

Spatial heterogeneities in the abundance of free-living organisms as well as in infection levels of their parasites are a common phenomenon, but knowledge on parasitism in invertebrate intermediate hosts in this respect is scarce. We investigated the spatial pattern of four dominant trematode species which utilize a common intertidal bivalve, the cockle Cerastoderma edule, as second intermediate host in their life cycles. Sampling of cockles from the same cohort at 15 sites in the northern Wadden Sea (North Sea) over a distance of 50 km revealed a conspicuous spatial heterogeneity in infection levels in all four species over the total sample as well as among and within sampling sites. Whereas multiple regression analyses indicated the density of first intermediate upstream hosts to be the strongest determinant of infection levels in cockles, the situation within sites was more complex with no single strong predictor variable. However, host size was positively and host density negatively correlated with infection levels and there was an indication of differential susceptibility of cockle hosts. Small-scale differences in physical properties of the habitat in the form of residual water at low tide resulted in increased infection levels of cockles which we experimentally transferred into pools. A complex interplay of these factors may be responsible for within-site heterogeneities. At larger spatial scales, these factors may be overridden by the strong effect of upstream hosts. In contrast to first intermediate trematode hosts, there was no indication for inter-specific interactions. In other terms, the recruitment of trematodes in second intermediate hosts seems to be largely controlled by pre-settlement processes both among and within host populations.

Global mapping of sea-ice production from the satellite microwaves

NASA Astrophysics Data System (ADS)

Ohshima, K. I.; Nihashi, S.; Iwamoto, K.; Tamaru, N.; Nakata, K.; Tamura, T.

2016-12-01

Global overturning circulation is driven by density differences. Saline water rejected by sea-ice production in coastal polynyas is the main source of dense water, and thus sea-ice production is a key factor in the overturning circulation. However, until recently sea-ice production and its interannual variability have not been well understood due to difficulties of in situ observation. The most effective means of detection of thin-ice area and estimation of sea-ice production on large scales is satellite remote sensing using passive microwave sensors, specifically the Special Sensor Microwave/Imager and Advanced Microwave Scanning Radiometer. This is based upon their ability to gain complete polar coverage on a daily basis irrespective of clouds and darkness. We have estimated sea-ice production globally based on heat flux calculations using the satellite-derived thin ice thickness data. The mapping demonstrates that ice production rate is high in Antarctic coastal polynyas, in contrast to Arctic coastal polynyas. This is consistent with the formation of Antarctic Bottom Water (AABW). The Ross Ice Shelf polynya has by far the highest ice production in the Southern Hemisphere. The mapping has revealed that the Cape Darnley polynya is the second highest production area, leading to the discovery of the missing (fourth) source of AABW in this region. In the region off the Mertz Glacier Tongue, sea-ice production decreased by as much as 40 %, due to the glacier calving in early 2010, resulting in a significant decrease in AABW production. The Okhotsk Northwestern polynya exhibits the highest ice production in the Northern Hemisphere, and the resultant dense water formation leads to overturning in the North Pacific. Estimates of its ice production show a significant decrease over the past 30-50 years, likely causing the weakening of the North Pacific overturning. The mapping also provides surface boundary conditions and validation data of heat- and salt-flux associated

Slab interactions in 3-D subduction settings: The Philippine Sea Plate region

NASA Astrophysics Data System (ADS)

Holt, Adam F.; Royden, Leigh H.; Becker, Thorsten W.; Faccenna, Claudio

2018-05-01

The importance of slab-slab interactions is manifested in the kinematics and geometry of the Philippine Sea Plate and western Pacific subduction zones, and such interactions offer a dynamic basis for the first-order observations in this complex subduction setting. The westward subduction of the Pacific Sea Plate changes, along-strike, from single slab subduction beneath Japan, to a double-subduction setting where Pacific subduction beneath the Philippine Sea Plate occurs in tandem with westward subduction of the Philippine Sea Plate beneath Eurasia. Our 3-D numerical models show that there are fundamental differences between single slab systems and double slab systems where both subduction systems have the same vergence. We find that the observed kinematics and slab geometry of the Pacific-Philippine subduction can be understood by considering an along-strike transition from single to double subduction, and is largely independent from the detailed geometry of the Philippine Sea Plate. Important first order features include the relatively shallow slab dip, retreating/stationary trenches, and rapid subduction for single slab systems (Pacific Plate subducting under Japan), and front slabs within a double slab system (Philippine Sea Plate subducting at Ryukyu). In contrast, steep to overturned slab dips, advancing trench motion, and slower subduction occurs for rear slabs in a double slab setting (Pacific subducting at the Izu-Bonin-Mariana). This happens because of a relative build-up of pressure in the asthenosphere beneath the Philippine Sea Plate, where the asthenosphere is constrained between the converging Ryukyu and Izu-Bonin-Mariana slabs. When weak back-arc regions are included, slab-slab convergence rates slow and the middle (Philippine) plate extends, which leads to reduced pressure build up and reduced slab-slab coupling. Models without back-arcs, or with back-arc viscosities that are reduced by a factor of five, produce kinematics compatible with present

Atmospheric influences on the anomalous 2016 Antarctic sea ice decay

NASA Astrophysics Data System (ADS)

Schlosser, Elisabeth; Haumann, F. Alexander; Raphael, Marilyn N.

2018-03-01

In contrast to the Arctic, where total sea ice extent (SIE) has been decreasing for the last three decades, Antarctic SIE has shown a small, but significant, increase during the same time period. However, in 2016, an unusually early onset of the melt season was observed; the maximum Antarctic SIE was already reached as early as August rather than the end of September, and was followed by a rapid decrease. The decay was particularly strong in November, when Antarctic SIE exhibited a negative anomaly (compared to the 1979-2015 average) of approximately 2 million km2. ECMWF Interim reanalysis data showed that the early onset of the melt and the rapid decrease in sea ice area (SIA) and SIE were associated with atmospheric flow patterns related to a positive zonal wave number three (ZW3) index, i.e., synoptic situations leading to strong meridional flow and anomalously strong southward heat advection in the regions of strongest sea ice decline. A persistently positive ZW3 index from May to August suggests that SIE decrease was preconditioned by SIA decrease. In particular, in the first third of November northerly flow conditions in the Weddell Sea and the Western Pacific triggered accelerated sea ice decay, which was continued in the following weeks due to positive feedback effects, leading to the unusually low November SIE. In 2016, the monthly mean Southern Annular Mode (SAM) index reached its second lowest November value since the beginning of the satellite observations. A better spatial and temporal coverage of reliable ice thickness data is needed to assess the change in ice mass rather than ice area.

Changes in ocean circulation and carbon storage are decoupled from air-sea CO2 fluxes

NASA Astrophysics Data System (ADS)

Marinov, I.; Gnanadesikan, A.

2011-02-01

The spatial distribution of the air-sea flux of carbon dioxide is a poor indicator of the underlying ocean circulation and of ocean carbon storage. The weak dependence on circulation arises because mixing-driven changes in solubility-driven and biologically-driven air-sea fluxes largely cancel out. This cancellation occurs because mixing driven increases in the poleward residual mean circulation result in more transport of both remineralized nutrients and heat from low to high latitudes. By contrast, increasing vertical mixing decreases the storage associated with both the biological and solubility pumps, as it decreases remineralized carbon storage in the deep ocean and warms the ocean as a whole.

Changes in ocean circulation and carbon storage are decoupled from air-sea CO2 fluxes

NASA Astrophysics Data System (ADS)

Marinov, I.; Gnanadesikan, A.

2010-11-01

The spatial distribution of the air-sea flux of carbon dioxide is a poor indicator of the underlying ocean circulation and of ocean carbon storage. The weak dependence on circulation arises because mixing-driven changes in solubility-driven and biologically-driven air-sea fluxes largely cancel out. This cancellation occurs because mixing driven increases in the poleward residual mean circulation results in more transport of both remineralized nutrients and heat from low to high latitudes. By contrast, increasing vertical mixing decreases the storage associated with both the biological and solubility pumps, as it decreases remineralized carbon storage in the deep ocean and warms the ocean as a whole.

STENCIL - Strategies and Tools for Environment-friendly Shore Nourishments as Climate Change Impact Low-Regret Measures

NASA Astrophysics Data System (ADS)

Schimmels, Stefan; Cofalla, Catrina; Deutschmann, Björn; Ganal, Caroline; Gijsman, Rik; Hass, H. Christian; Hollert, Henner; Mielck, Finn; Schlurmann, Thorsten; Schüttrumpf, Holger; Shiravani, Gholamreza; Staudt, Franziska; Strusinska, Agnieszka; Visscher, Jan; Wiltshire, Karen; Wolbring, Johanna

2017-04-01

Shore nourishments are regarded as an almost routine coastal protection measure and have been carried out worldwide for several decades. Recent studies generally conclude that "soft" coastal protection measures are an effective option for a sustainable coastal management. However, more research on economic sustainability, species-specific habitat demands and availability of sand deposits is required. Nowadays, the recent paradigm shifts to concepts like the Integrated Coastal Zone Management (ICZM) and the Ecosystem Approach to Management (EAM). For the German Wadden Sea these management objectives are an important issue of the "Wattenmeerstrategie 2100" (MELLUR-SH, 2015), a political strategy report that demands an adaption against the global change and the expected sea-level rise up to the year 2100. Hence, also new concepts and tools for the implementation of more sustainable, effective and environment-friendly shore nourishments are needed. The research project STENCIL joins the expertise of coastal engineers, geologists, biologists and toxicologists in order to make a first step towards the long-term goal of establishing an ICZM and EAM for shore nourishments in the German Wadden Sea. The project focuses on providing improved tools, models and methods for the prediction of coastal hydro- and morphodynamics. Furthermore, the impact of dredging and dumping activities on benthic habitats and their natural regeneration potentials will be evaluated. Since these impacts are still widely uninvestigated, monitoring of dredging areas and the surrounding sites using hydroacoustic devices, aerial photos and sediment samples for grain-size and benthos analysis remains of high importance. In order to develop standardized operative observation methods, analysis and decision-supporting tools, an implementation of field measurements, laboratory experiments as well as conceptual and numerical models is planned. These combined approaches will result in valuable data sets for

Opening of the South China Sea and Upwelling of the Hainan Plume

NASA Astrophysics Data System (ADS)

Yu, Mengming; Yan, Yi; Huang, Chi-Yue; Zhang, Xinchang; Tian, Zhixian; Chen, Wen-Huang; Santosh, M.

2018-03-01

Opening of the South China Sea and upwelling of the Hainan Plume are among the most challenging issues related to the tectonic evolution of East Asia. However, when and how the Hainan Plume affected the opening of the South China Sea remains unclear. Here we investigate the geochemical and isotopic features of the 25 Ma mid-ocean ridge basalt (MORB) in the Kenting Mélange, southern Taiwan, 16 Ma MORB drilled by the IODP Expedition 349, and 9 Ma ocean island basalt-type dredged seamount basalt. The 25 Ma MORBs reveal a less metasomatic depleted MORB mantle-like source. In contrast, the Miocene samples record progressive mantle enrichment and possibly signal the contribution of the Hainan Plume. We speculate that MORBs of the South China Sea which could have recorded plume-ridge source mixing perhaps appear since 23.8 Ma. On the contrary, the Paleocene-Eocene ocean island basalt-type intraplate volcanism of the South China continental margin is correlated to decompression melting of a passively upwelling fertile asthenosphere due to continental rifting.

Arctic Sea Ice Predictability and the Sea Ice Prediction Network

NASA Astrophysics Data System (ADS)

Wiggins, H. V.; Stroeve, J. C.

2014-12-01

Drastic reductions in Arctic sea ice cover have increased the demand for Arctic sea ice predictions by a range of stakeholders, including local communities, resource managers, industry and the public. The science of sea-ice prediction has been challenged to keep up with these developments. Efforts such as the SEARCH Sea Ice Outlook (SIO; http://www.arcus.org/sipn/sea-ice-outlook) and the Sea Ice for Walrus Outlook have provided a forum for the international sea-ice prediction and observing community to explore and compare different approaches. The SIO, originally organized by the Study of Environmental Change (SEARCH), is now managed by the new Sea Ice Prediction Network (SIPN), which is building a collaborative network of scientists and stakeholders to improve arctic sea ice prediction. The SIO synthesizes predictions from a variety of methods, including heuristic and from a statistical and/or dynamical model. In a recent study, SIO data from 2008 to 2013 were analyzed. The analysis revealed that in some years the predictions were very successful, in other years they were not. Years that were anomalous compared to the long-term trend have proven more difficult to predict, regardless of which method was employed. This year, in response to feedback from users and contributors to the SIO, several enhancements have been made to the SIO reports. One is to encourage contributors to provide spatial probability maps of sea ice cover in September and the first day each location becomes ice-free; these are an example of subseasonal to seasonal, local-scale predictions. Another enhancement is a separate analysis of the modeling contributions. In the June 2014 SIO report, 10 of 28 outlooks were produced from models that explicitly simulate sea ice from dynamic-thermodynamic sea ice models. Half of the models included fully-coupled (atmosphere, ice, and ocean) models that additionally employ data assimilation. Both of these subsets (models and coupled models with data

Assessment of Arctic and Antarctic Sea Ice Predictability in CMIP5 Decadal Hindcasts

NASA Technical Reports Server (NTRS)

Yang, Chao-Yuan; Liu, Jiping (Inventor); Hu, Yongyun; Horton, Radley M.; Chen, Liqi; Cheng, Xiao

2016-01-01

This paper examines the ability of coupled global climate models to predict decadal variability of Arctic and Antarctic sea ice. We analyze decadal hindcasts/predictions of 11 Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Decadal hindcasts exhibit a large multimodel spread in the simulated sea ice extent, with some models deviating significantly from the observations as the predicted ice extent quickly drifts away from the initial constraint. The anomaly correlation analysis between the decadal hindcast and observed sea ice suggests that in the Arctic, for most models, the areas showing significant predictive skill become broader associated with increasing lead times. This area expansion is largely because nearly all the models are capable of predicting the observed decreasing Arctic sea ice cover. Sea ice extent in the North Pacific has better predictive skill than that in the North Atlantic (particularly at a lead time of 3-7 years), but there is a reemerging predictive skill in the North Atlantic at a lead time of 6-8 years. In contrast to the Arctic, Antarctic sea ice decadal hindcasts do not show broad predictive skill at any timescales, and there is no obvious improvement linking the areal extent of significant predictive skill to lead time increase. This might be because nearly all the models predict a retreating Antarctic sea ice cover, opposite to the observations. For the Arctic, the predictive skill of the multi-model ensemble mean outperforms most models and the persistence prediction at longer timescales, which is not the case for the Antarctic. Overall, for the Arctic, initialized decadal hindcasts show improved predictive skill compared to uninitialized simulations, although this improvement is not present in the Antarctic.

Impact of sea-level rise on earthquake and landslide triggering offshore the Alentejo margin (SW Iberia)

NASA Astrophysics Data System (ADS)

Neves, M. C.; Roque, C.; Luttrell, K. M.; Vázquez, J. T.; Alonso, B.

2016-12-01

Earthquakes and submarine landslides are recurrent and widespread manifestations of fault activity offshore SW Iberia. The present work tests the effects of sea-level rise on offshore fault systems using Coulomb stress change calculations across the Alentejo margin. Large-scale faults capable of generating large earthquakes and tsunamis in the region, especially NE-SW trending thrusts and WNW-ESE trending dextral strike-slip faults imaged at basement depths, are either blocked or unaffected by flexural effects related to sea-level changes. Large-magnitude earthquakes occurring along these structures may, therefore, be less frequent during periods of sea-level rise. In contrast, sea-level rise promotes shallow fault ruptures within the sedimentary sequence along the continental slope and upper rise within distances of <100 km from the coast. The results suggest that the occurrence of continental slope failures may either increase (if triggered by shallow fault ruptures) or decrease (if triggered by deep fault ruptures) as a result of sea-level rise. Moreover, observations of slope failures affecting the area of the Sines contourite drift highlight the role of sediment properties as preconditioning factors in this region.

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: Mean seasonal cycle

NASA Astrophysics Data System (ADS)

Li, Linghan; McClean, Julie L.; Miller, Arthur J.; Eisenman, Ian; Hendershott, Myrl C.; Papadopoulos, Caroline A.

2014-12-01

The seasonal cycle of sea ice variability in the Bering Sea, together with the thermodynamic and dynamic processes that control it, are examined in a fine resolution (1/10°) global coupled ocean/sea-ice model configured in the Community Earth System Model (CESM) framework. The ocean/sea-ice model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and the Los Alamos Sea Ice Model (CICE). The model was forced with time-varying reanalysis atmospheric forcing for the time period 1970-1989. This study focuses on the time period 1980-1989. The simulated seasonal-mean fields of sea ice concentration strongly resemble satellite-derived observations, as quantified by root-mean-square errors and pattern correlation coefficients. The sea ice energy budget reveals that the seasonal thermodynamic ice volume changes are dominated by the surface energy flux between the atmosphere and the ice in the northern region and by heat flux from the ocean to the ice along the southern ice edge, especially on the western side. The sea ice force balance analysis shows that sea ice motion is largely associated with wind stress. The force due to divergence of the internal ice stress tensor is large near the land boundaries in the north, and it is small in the central and southern ice-covered region. During winter, which dominates the annual mean, it is found that the simulated sea ice was mainly formed in the northern Bering Sea, with the maximum ice growth rate occurring along the coast due to cold air from northerly winds and ice motion away from the coast. South of St Lawrence Island, winds drive the model sea ice southwestward from the north to the southwestern part of the ice-covered region. Along the ice edge in the western Bering Sea, model sea ice is melted by warm ocean water, which is carried by the simulated Bering Slope Current flowing to the northwest, resulting in the S-shaped asymmetric ice edge. In spring and fall, similar thermodynamic and dynamic

Sea otters are recolonizing southern California in fits and starts

USGS Publications Warehouse

Lafferty, Kevin D.; Tinker, M. Tim

2014-01-01

After near extinction as a result of the fur trade in the 1700s and 1800s, the southern sea otter slowly reoccupied the core of its range in central California. Range expansion beyond central California is seen as key to full recovery of otters, but the rate of expansion has been sporadic, raising concerns about habitat quality in southern California. To describe the range expansion of sea otters from central into southern California, we used skiff surveys, aerial surveys, and archival time-depth recorders from 2004 to 2013. These observations show that range expansion began when male otters swam southeast of Point Conception (Cojo Anchorage), perhaps to seek refuge from bad weather and to feed on unexploited resources. After several years of seasonal use by male groups, females began to use the area, leading to reproduction and a secondary increase in abundance. In contrast, a second male group that moved farther down the coast to Coal Oil Point stalled and retreated. Such range expansion and contraction can be explained by the social nature of sea otters, which acts to slow dispersal away from groups. Otter densities at Cojo Anchorage are now approaching equilibrium levels reported for central California. As in central California, otters rested in and near kelp forest habitat, but used deeper water for foraging. Together, these observations suggest habitat in the Santa Barbara Channel can still support sea otters, but range expansion of otters into southern California will be episodic due to social dynamics.

Thorium-230 ages of corals and duration of the last interglacial sea-level high stand on Oahu, Hawaii

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

Szabo, B.J.; Ludwig, K.R.; Muhs, D.R.

1994-10-07

Thorium-230 ages of emergent marine deposits on Oahu, Hawaii, have a uniform distribution of ages from {approximately}114,000 to {approximately}131,000 years, indicating a duration for the last interglacial sea-level high stand of {approximately}17,000 years, in contrast to a duration of {approximately}8000 years inferred from the orbitally tuned marine oxygen isotope record. Sea level on Oahu rose to {>=}1 to 2 meters higher than present by 131,000 years ago or {approximately}6000 years earlier than inferred from the marine record. Although the latter record suggests a shift back to glacial conditions beginning at {approximately}119,000 years ago, the Oahu coral ages indicate a nearmore » present sea level until {approximately}114,000 years ago.« less

Variability of Arctic Sea Ice as Viewed from Space

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.

1998-01-01

Over the past 20 years, satellite passive-microwave radiometry has provided a marvelous means for obtaining information about the variability of the Arctic sea ice cover and particularly about sea ice concentrations (% areal coverages) and from them ice extents and the lengths of the sea ice season. This ability derives from the sharp contrast between the microwave emissions of sea ice versus liquid water and allows routine monitoring of the vast Arctic sea ice cover, which typically varies in extent from a minimum of about 8,000,000 sq km in September to a maximum of about 15,000,000 sq km in March, the latter value being over 1.5 times the area of either the United States or Canada. The vast Arctic ice cover has many impacts, including hindering heat, mass, and y momentum exchanges between the oceans and the atmosphere, reducing the amount of solar radiation absorbed at the Earth's surface, affecting freshwater transports and ocean circulation, and serving as a vital surface for many species of polar animals. These direct impacts also lead to indirect impacts, including effects on local and perhaps global atmospheric temperatures, effects that are being examined in general circulation modeling studies, where preliminary results indicate that changes on the order of a few percent sea ice concentration can lead to temperature changes of 1 K or greater even in local areas outside of the sea ice region. Satellite passive-microwave data for November 1978 through December 1996 reveal marked regional and interannual variabilities in both the ice extents and the lengths of the sea ice season, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 km(2), while individual regions showed much greater percentage variations, e.g., with the Greenland Sea experiencing a range of 740,000 - 1,1110,000 km(2) in its yearly maximum ice coverage. Although variations from year to

Contemporary Arctic Sea Level

NASA Astrophysics Data System (ADS)

Cazenave, A. A.

2017-12-01

During recent decades, the Arctic region has warmed at a rate about twice the rest of the globe. Sea ice melting is increasing and the Greenland ice sheet is losing mass at an accelerated rate. Arctic warming, decrease in the sea ice cover and fresh water input to the Arctic ocean may eventually impact the Arctic sea level. In this presentation, we review our current knowledge of contemporary Arctic sea level changes. Until the beginning of the 1990s, Arctic sea level variations were essentially deduced from tide gauges located along the Russian and Norwegian coastlines. Since then, high inclination satellite altimetry missions have allowed measuring sea level over a large portion of the Arctic Ocean (up to 80 degree north). Measuring sea level in the Arctic by satellite altimetry is challenging because the presence of sea ice cover limits the full capacity of this technique. However adapted processing of raw altimetric measurements significantly increases the number of valid data, hence the data coverage, from which regional sea level variations can be extracted. Over the altimetry era, positive trend patterns are observed over the Beaufort Gyre and along the east coast of Greenland, while negative trends are reported along the Siberian shelf. On average over the Arctic region covered by satellite altimetry, the rate of sea level rise since 1992 is slightly less than the global mea sea level rate (of about 3 mm per year). On the other hand, the interannual variability is quite significant. Space gravimetry data from the GRACE mission and ocean reanalyses provide information on the mass and steric contributions to sea level, hence on the sea level budget. Budget studies show that regional sea level trends over the Beaufort Gyre and along the eastern coast of Greenland, are essentially due to salinity changes. However, in terms of regional average, the net steric component contributes little to the observed sea level trend. The sea level budget in the Arctic

Contrast induced nephropathy: updated ESUR Contrast Media Safety Committee guidelines.

PubMed

Stacul, Fulvio; van der Molen, Aart J; Reimer, Peter; Webb, Judith A W; Thomsen, Henrik S; Morcos, Sameh K; Almén, Torsten; Aspelin, Peter; Bellin, Marie-France; Clement, Olivier; Heinz-Peer, Gertraud

2011-12-01

The Contrast Media Safety Committee (CMSC) of the European Society of Urogenital Radiology (ESUR) has updated its 1999 guidelines on contrast medium-induced nephropathy (CIN). Topics reviewed include the definition of CIN, the choice of contrast medium, the prophylactic measures used to reduce the incidence of CIN, and the management of patients receiving metformin. Key Points • Definition, risk factors and prevention of contrast medium induced nephropathy are reviewed. • CIN risk is lower with intravenous than intra-arterial iodinated contrast medium. • eGFR of 45 ml/min/1.73 m (2) is CIN risk threshold for intravenous contrast medium. • Hydration with either saline or sodium bicarbonate reduces CIN incidence. • Patients with eGFR ≥ 60 ml/min/1.73 m (2) receiving contrast medium can continue metformin normally.

Sea Surface Temperature and Ocean Color Variability in the South China Sea

NASA Astrophysics Data System (ADS)

Conaty, A. P.

2001-12-01

The South China Sea is a marginal sea in the Southeast Asian region whose surface circulation is driven by monsoons and whose surface currents have complex seasonal patterns. Its rich natural resources and strategic location have made its small islands areas of political dispute among the neighboring nations. This study aims to show the seasonal and interannual variability of sea surface temperature and ocean color in South China Sea. It makes use of NOAA's Advanced Very High Resolution Radiometer (AVHRR) satellite data sets on sea surface temperature for the period 1981-2000 and NASA's Nimbus-7 Coastal Zone Color Scanner (CZCS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite data sets on pigment concentration (ocean color) for the period 1981-1996 and 1997-2000, respectively. Transect lines were drawn along several potential hotspot areas to show the variability in sea surface temperature and pigment concentration through time. In-situ data on sea surface temperature along South China Sea were likewise plotted to see the variability with time. Higher seasonal variability in sea surface temperature was seen at higher latitudes. Interannual variability was within 1-3 Kelvin. In most areas, pigment concentration was higher during northern hemisphere winter and autumn, after the monsoon rains, with a maximum of 30 milligrams per cubic meter.

Vulnerability of marginal seas to sea level rise

NASA Astrophysics Data System (ADS)

Gomis, Damia; Jordà, Gabriel

2017-04-01

Sea level rise (SLR) is a serious thread for coastal areas and has a potential negative impact on society and economy. SLR can lead for instance to land loss, beach reduction, increase of the damage of marine storms on coastal infrastructures and to the salinization of underground water streams. It is well acknowledged that future SLR will be inhomogeneous across the globe, with regional differences of up to 100% with respect to global mean sea level (GMSL). Several studies have addressed the projections of SLR at regional scale, but most of them are based on global climate models (GCMs) that have a relatively coarse spatial resolution (>1°). In marginal seas this has proven to be a strong limitation, as their particular configurations require spatial resolutions that are not reachable by present GCMs. A paradigmatic case is the Mediterranean Sea, connected to the global ocean through the Strait of Gibraltar, a narrow passage of 14 km width. The functioning of the Mediterranean Sea involves a variety of processes including an overturning circulation, small-scale convection and a rich mesoscale field. Moreover, the long-term evolution of Mediterranean sea level has been significantly different from the global mean during the last decades. The observations of present climate and the projections for the next decades have lead some authors to hypothesize that the particular characteristics of the basin could allow Mediterranean mean sea level to evolve differently from the global mean. Assessing this point is essential to undertake proper adaptation strategies for the largely populated Mediterranean coastal areas. In this work we apply a new approach that combines regional and global projections to analyse future SLR. In a first step we focus on the quantification of the expected departures of future Mediterranean sea level from GMSL evolution and on the contribution of different processes to these departures. As a result we find that, in spite of its particularities

Deep-sea Hexactinellida (Porifera) of the Weddell Sea

NASA Astrophysics Data System (ADS)

Janussen, Dorte; Tabachnick, Konstantin R.; Tendal, Ole S.

2004-07-01

New Hexactinellida from the deep Weddel Sea are described. This moderately diverse hexactinellid fauna includes 14 species belonging to 12 genera, of which five species and one subgenus are new to science: Periphragella antarctica n. sp., Holascus pseudostellatus n. sp., Caulophacus (Caulophacus) discohexactinus n. sp., C. ( Caulodiscus) brandti n. sp., C. ( Oxydiscus) weddelli n. sp., and C. ( Oxydiscus) n. subgen. So far, 20 hexactinellid species have been reported from the deep Weddell Sea, 15 are known from the northern part and 10 only from here, while 10 came from the southern area, and five of these only from there. However, this apparent high "endemism" of Antarctic hexactinellid sponges is most likely the result of severe undersampling of the deep-sea fauna. We find no reason to believe that a division between an oceanic and a more continental group of species exists. The current poor database indicates that a substantial part of the deep hexactinellid fauna of the Weddell Sea is shared with other deep-sea regions, but it does not indicate a special biogeographic relationship with any other ocean.

Sea Ice Drift Monitoring in the Bohai Sea Based on GF4 Satellite

NASA Astrophysics Data System (ADS)

Zhao, Y.; Wei, P.; Zhu, H.; Xing, B.

2018-04-01

The Bohai Sea is the inland sea with the highest latitude in China. In winter, the phenomenon of freezing occurs in the Bohai Sea due to frequent cold wave influx. According to historical records, there have been three serious ice packs in the Bohai Sea in the past 50 years which caused heavy losses to our economy. Therefore, it is of great significance to monitor the drift of sea ice and sea ice in the Bohai Sea. The GF4 image has the advantages of short imaging time and high spatial resolution. Based on the GF4 satellite images, the three methods of SIFT (Scale invariant feature - the transform and Scale invariant feature transform), MCC (maximum cross-correlation method) and sift combined with MCC are used to monitor sea ice drift and calculate the speed and direction of sea ice drift, the three calculation results are compared and analyzed by using expert interpretation and historical statistical data to carry out remote sensing monitoring of sea ice drift results. The experimental results show that the experimental results of the three methods are in accordance with expert interpretation and historical statistics. Therefore, the GF4 remote sensing satellite images have the ability to monitor sea ice drift and can be used for drift monitoring of sea ice in the Bohai Sea.

Estimating the Mediterranean Sea Water Budget: impact of RCM design

NASA Astrophysics Data System (ADS)

Somot, S.; Elguindi, N.; Sanchez-Gomez, E.; Herrmann, M.; Déqué, M.

2009-09-01

The Mediterranean Sea can be considered as a thermodynamic machine that exchanges water and heat with the Atlantic Ocean through the Strait of Gibraltar and with the atmosphere through its surface. Considering the Mediterranean Sea Water Budget (MSWB) multi-year mean, the Mediterranean basin looses water at the surface due to an excess of evaporation over freshwater input (precipitation, river runoff, Black Sea input). Moreover the MSWB largely drives the Mediterranean Sea water mass formation and therefore a large part of its thermohaline circulation. This could even have an impact on the characteristics of the Atlantic thermohaline circulation through the Mediterranean Outflow Waters that flow into the Atlantic at a depth of about 1000 m. From a climate point of view, the MSWB acts as a water source for the Mediterranean countries and therefore plays an important role on the water resources of the region. The regional physical characteristics of the Mediterranean basin (complex orography, strong land-sea contrast, land-atmosphere coupling, air-sea coupling, river inflow, Gibraltar Strait constraint and complex ocean bathymetry) strongly influence the various components of the MSWB. Moreover extreme precipitation events over land and strong evaporation events over the sea due to local winds can play a non-negligible role on the mean MSWB despite their small spatial and temporal scales. Therefore, modelling the mean behaviour, the interannual variability and the trends of the MSWB is a challenging task of the Regional Climate Model community in the context of climate change. It is actually one of the highlighted issues of the HyMex project planned for the 2010-2020 period. We propose here to start investigating some key scientific issues of the regional modelling of the Mediterranean Sea Water Budget using a wide range of regional climate simulations performed at Météo-France or in the framework of FP6 European projects (ENSEMBLES, CIRCE). The addressed

A long term glider study of shelf sea oxygen dynamics

NASA Astrophysics Data System (ADS)

Williams, Charlotte; Palmer, Matthew; Mahaffey, Claire; Davis, Clare

2017-04-01

Oxygen is involved in most biogeochemical processes in the ocean, and dissolved oxygen (DO) is a well-established indicator for biological activity via the estimate of apparent oxygen utilisation (AOU). In the deep waters of the open ocean, the AOU provides a valuable insight into the ocean's biological carbon pump. However, in the physically dynamic and highly productive shallow shelf seas, interpretation of the oxygen distribution and the magnitude of AOU is complex. Physical processes, such as diapycnal mixing, entrainment and horizontal advection act to ventilate waters below the thermocline and thus increase oxygen and decrease AOU. In contrast, biological remineralisation of organic material below the thermocline will consume oxygen and increase AOU. We aim to address the following: 1. Does AOU change seasonally in a shelf sea in response to seasonal changes in productivity? 2. How important is turbulence in redistributing oxygen in a shelf sea? Using 9 months of high-resolution data from >20 glider deployments in the seasonally stratified NW European Shelf Sea we identify and quantify the physical and biological processes that control the DO distribution and magnitude of AOU in shelf seas. A 200km transect between the shelf edge and the central Celtic Sea (CCS) was repeated between November 2014 and August 2015, thus capturing key periods in the seasonal cycling in shelf seas, specifically the onset of stratification, the spring bloom, stratified summer period and breakdown of stratification. The gliders collected data for DO, temperature, salinity, chlorophyll fluorescence, CDOM, backscatter and turbulence. In addition, direct measurements of turbulent dissipation from the Ocean Microstructure Glider deployed during the campaign provided estimates of mixing at CCS and the shelf break, allowing accurate quantification of the vertical fluxes of oxygen. We find that oxygen decreases ubiquitously across the shelf as soon as stratification takes hold, though BML

Life history plasticity and population regulation in sea otters

USGS Publications Warehouse

Monson, Daniel H.; Estes, James A.; Bodkin, James L.; Siniff, Donald B.

2000-01-01

We contrasted body condition, and age-specific reproduction and mortality between a growing population of sea otters (Enhydralutris) at Kodiak Island and a high-density near-equilibrium population at Amchitka Island, Alaska. We obtained data from marked individuals, population surveys, and collections of beach-cast carcasses. Mass:length ratios indicated that females (but not males) captured in 1992 at Amchitka were in poorer condition than those captured at Kodiak in 1986–1987. In 1993, the condition of females at Amchitka improved in apparent response to two factors: (1) an episodic influx of Pacific smooth lumpsuckers, Aptocyclus ventricocus, from the epi-pelagic zone, which otters consumed; and (2) an increase in the otters’ benthic invertebrate prey resulting from declining otter numbers. Reproductive rates varied with age (0.37 [CI=0.21 to 0.53] births female−1 yr−1 for 2–3-yr-olds, and 0.83 [CI=0.69 to 0.90] for females ≥4 yr old), and were similar at both areas. Weaning success (pups surviving to ≥120 d), in contrast, was almost 50% lower at Amchitka than at Kodiak and for females ≥4 yr of age was 0.52 (CI=0.38 to 0.66) vs 0.94 (CI=0.75 to 0.99), respectively. Sixty-two percent of the preweaning pup losses at Amchitka occurred within a month of parturition and 79% within two months. Postweaning survival was also low at Amchitka as only 18% of instrumented pups were known to be alive one year after mother-pup separation. Adult survival rates appeared similar at Amchitka and Kodiak. Factors affecting survival early in life thus are a primary demographic mechanism of population regulation in sea otters. By maintaining uniformly high reproductive rates over time and limiting investment in any particular reproductive event, sea otters can take advantage of unpredictable environmental changes favorable to pup survival. This strategy is consistent with predictions of “bet-hedging” life history models.

Contrast-enhanced peripheral MRA: technique and contrast agents.

PubMed

Nielsen, Yousef W; Thomsen, Henrik S

2012-09-01

In the last decade contrast-enhanced magnetic resonance angiography (CE-MRA) has gained wide acceptance as a valuable tool in the diagnostic work-up of patients with peripheral arterial disease. This review presents current concepts in peripheral CE-MRA with emphasis on MRI technique and contrast agents. Peripheral CE-MRA is defined as an MR angiogram of the arteries from the aortic bifurcation to the feet. Advantages of CE-MRA include minimal invasiveness and lack of ionizing radiation. The basic technique employed for peripheral CE-MRA is the bolus-chase method. With this method a paramagnetic MRI contrast agent is injected intravenously and T1-weighted images are acquired in the subsequent arterial first-pass phase. In order to achieve high quality MR angiograms without interfering venous contamination or artifacts, a number of factors need to be taken into account. This includes magnetic field strength of the MRI system, receiver coil configuration, use of parallel imaging, contrast bolus timing technique, and k-space filling strategies. Furthermore, it is possible to optimize peripheral CE-MRA using venous compression techniques, hybrid scan protocols, time-resolved imaging, and steady-state MRA. Gadolinium(Gd)-based contrast agents are used for CE-MRA of the peripheral arteries. Extracellular Gd agents have a pharmacokinetic profile similar to iodinated contrast media. Accordingly, these agents are employed for first-pass MRA. Blood-pool Gd-based agents are characterized by prolonged intravascular stay, due to macromolecular structure or protein binding. These agents can be used for first-pass, as well as steady-state MRA. Some Gd-based contrast agents with low thermodynamic stability have been linked to development of nephrogenic systemic fibrosis in patients with severe renal insufficiency. Using optimized technique and a stable MRI contrast agent, peripheral CE-MRA is a safe procedure with diagnostic accuracy close to that of conventional catheter X

STS-49 Earth observation of the Salton Sea and the Gulf of California

NASA Technical Reports Server (NTRS)

1992-01-01

STS-49 Earth observation taken aboard Endeavour, Orbiter Vehicle (OV) 105, shows the Salton Sea and the Gulf of California. The nearly cloud-free view follows the Colorado River Delta from the Gulf of California (Mexico) to the Salton Sea (California). The Colorado River enters its delta from the right (east), then turns directly south to form saline tidal flats at the edge of the gulf. Nearly all the water is used for irrigation. The United States (U.S.) / Mexican border shows clearly in the different field patterns and the intensity of the greenish color. The irrigated agricultural area offers a sharp contrast to the surrounding desert. The crew used a handheld HASSELBLAD camera with a 100-mm lens to record the image.

Contrasted phylogeographic patterns on mitochondrial DNA of shallow and deep brittle stars across the Atlantic-Mediterranean area

PubMed Central

Taboada, Sergi; Pérez-Portela, Rocío

2016-01-01

Previous studies on Ophiothrix in European waters demonstrated the existence of two distinct species, Ophiothrix fragilis and Ophiothrix sp. II. Using phylogenetic and species delimitation techniques based on two mitochondrial genes (cytochrome c oxidase I and 16S rRNA) we prove the existence of a new congeneric species (Ophiothrix sp. III), occurring in the deep Atlantic coast of the Iberian Peninsula and the Alboran Sea. We compared phylogeographic patterns of these three Ophiothrix species to test whether closely related species are differentially affected by past demographic events and current oceanographic barriers. We used 432 sequences (137 of O. fragilis, 215 of Ophiothrix sp. II, and 80 of Ophiothrix sp. III) of the 16S rRNA from 23 Atlantic-Mediterranean locations for the analyses. We observed different geographic and bathymetric distributions, and contrasted phylogeography among species. Ophiothrix fragilis appeared genetically isolated between the Atlantic and Mediterranean basins, attributed to past vicariance during Pleistocene glaciations and a secondary contact associated to demographic expansion. This contrasts with the panmixia observed in Ophiothrix sp. II across the Atlantic-Mediterranean area. Results were not conclusive for Ophiothrix sp. III due to the lack of a more complete sampling within the Mediterranean Sea. PMID:27585743

First biological measurements of deep-sea corals from the Red Sea

PubMed Central

Roder, C.; Berumen, M. L.; Bouwmeester, J.; Papathanassiou, E.; Al-Suwailem, A.; Voolstra, C. R.

2013-01-01

It is usually assumed that metabolic constraints restrict deep-sea corals to cold-water habitats, with ‘deep-sea’ and ‘cold-water’ corals often used as synonymous. Here we report on the first measurements of biological characters of deep-sea corals from the central Red Sea, where they occur at temperatures exceeding 20°C in highly oligotrophic and oxygen-limited waters. Low respiration rates, low calcification rates, and minimized tissue cover indicate that a reduced metabolism is one of the key adaptations to prevailing environmental conditions. We investigated four sites and encountered six species of which at least two appear to be undescribed. One species is previously reported from the Red Sea but occurs in deep cold waters outside the Red Sea raising interesting questions about presumed environmental constraints for other deep-sea corals. Our findings suggest that the present understanding of deep-sea coral persistence and resilience needs to be revisited. PMID:24091830

Influences of sea ice on eastern Bering Sea phytoplankton

NASA Astrophysics Data System (ADS)

Zhou, Qianqian; Wang, Peng; Chen, Changping; Liang, Junrong; Li, Bingqian; Gao, Yahui

2015-03-01

The influence of sea ice on the species composition and cell density of phytoplankton was investigated in the eastern Bering Sea in spring 2008. Diatoms, particularly pennate diatoms, dominated the phytoplankton community. The dominant species were Grammonema islandica (Grunow in Van Heurck) Hasle, Fragilariopsis cylindrus (Grunow) Krieger, F. oceanica (Cleve) Hasle, Navicula vanhoeffenii Gran, Thalassiosira antarctica Comber, T. gravida Cleve, T. nordenskiöeldii Cleve, and T. rotula Meunier. Phytoplankton cell densities varied from 0.08×104 to 428.8×104 cells/L, with an average of 30.3×104 cells/L. Using cluster analysis, phytoplankton were grouped into three assemblages defined by ice-forming conditions: open water, ice edge, and sea ice assemblages. In spring, when the sea ice melts, the phytoplankton dispersed from the sea ice to the ice edge and even into open waters. Thus, these phytoplankton in the sea ice may serve as a "seed bank" for phytoplankton population succession in the subarctic ecosystem. Moreover, historical studies combined with these results suggest that the sizes of diatom species have become smaller, shifting from microplankton to nannoplankton-dominated communities.

Type C botulism in pelicans and other fish-eating birds at the Salton Sea

USGS Publications Warehouse

Rocke, T.E.; Nol, P.; Pelizza, C.; Sturm, K.K.

2004-01-01

In 1996, type C avian botulism killed over 10,000 pelicans and nearly 10,000 other fish-eating birds at the Salton Sea in southern California. Although botulism had been previously documented in waterbirds at the Sea, this die-off was unusual in that it involved primarily fish-eating birds. The American White Pelican (Pelecanus erythrorynchos) was the species with the greatest mortality in 1996. Since 1996, mortality has recurred every year but losses have declined (<2,000 birds/year), with relatively more Brown Pelicans (P. occidentalis) than White Pelicans afflicted. In 2000, morbidity and mortality of Brown Pelicans with type C botulism (1311) approached the numbers afflicted in 1996 (2034). In recent years, mortality reached a peak earlier in the summer, July and August, in contrast to 1996 when mortality reached a peak in September. An exotic fish species, tilapia (Oreochromis mossambicus), has been implicated as the source of toxin for birds at Salton Sea, but the source of toxin for fish is unknown.

A study of oceanic surface heat fluxes in the Greenland, Norwegian, and Barents Seas

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa; Cavalieri, Donald J.

1989-01-01

This study examines oceanic surface heat fluxes in the Norwegian, Greenland, and Barents seas using the gridded Navy Fleet Numerical Oceanography Central surface analysis and the First GARP Global Experiment (FGGE) IIc cloudiness data bases. Monthly and annual means of net and turbulent heat fluxes are computed for the FGGE year 1979. The FGGE IIb data base consisting of individual observations provides particularly good data coverage in this region for a comparison with the gridded Navy winds and air temperatures. The standard errors of estimate between the Navy and FGGE IIb winds and air temperatures are 3.6 m/s and 2.5 C, respectively. The computations for the latent and sensible heat fluxes are based on bulk formulas with the same constant heat exchange coefficient of 0.0015. The results show extremely strong wintertime heat fluxes in the northern Greenland Sea and especially in the Barents Sea in contrast to previous studies.

Changes in Arctic and Antarctic Sea Ice as a Microcosm of Global Climate Change

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.

2014-01-01

Polar sea ice is a key element of the climate system and has now been monitored through satellite observations for over three and a half decades. The satellite observations reveal considerable information about polar ice and its changes since the late 1970s, including a prominent downward trend in Arctic sea ice coverage and a much lesser upward trend in Antarctic sea ice coverage, illustrative of the important fact that climate change entails spatial contrasts. The decreasing ice coverage in the Arctic corresponds well with contemporaneous Arctic warming and exhibits particularly large decreases in the summers of 2007 and 2012, influenced by both preconditioning and atmospheric conditions. The increasing ice coverage in the Antarctic is not as readily explained, but spatial differences in the Antarctic trends suggest a possible connection with atmospheric circulation changes that have perhaps been influenced by the Antarctic ozone hole. The changes in the polar ice covers and the issues surrounding those changes have many commonalities with broader climate changes and their surrounding issues, allowing the sea ice changes to be viewed in some important ways as a microcosm of global climate change.

Deep-sea geohazards in the South China Sea

NASA Astrophysics Data System (ADS)

Wu, Shiguo; Wang, Dawei; Völker, David

2018-02-01

Various geological processes and features that might inflict hazards identified in the South China Sea by using new technologies and methods. These features include submarine landslides, pockmark fields, shallow free gas, gas hydrates, mud diapirs and earthquake tsunami, which are widely distributed in the continental slope and reefal islands of the South China Sea. Although the study and assessment of geohazards in the South China Sea came into operation only recently, advances in various aspects are evolving at full speed to comply with National Marine Strategy and `the Belt and Road' Policy. The characteristics of geohazards in deep-water seafloor of the South China Sea are summarized based on new scientific advances. This progress is aimed to aid ongoing deep-water drilling activities and decrease geological risks in ocean development.

SeaRover: An Emerging Technology for Sea Surface Sensor Networks

NASA Astrophysics Data System (ADS)

Fong, T.; Kudela, R.; Curcio, J.; Davidson, K.; Darling, D.; Kirkwood, B.

2005-12-01

Introduction - SeaRover is envisioned as an autonomous surface vehicle (ASV) for coastal operations. It is intended to lower the cost of existing marine survey applications while enabling new science missions. The current conceptual design is a small vehicle with hull and propulsion system optimized to eliminate cavitation and EM noise. SeaRover will make significant advances over existing platforms by providing longer duration science missions, better positioning and mission control, larger power budgets for instrumentation and significantly lower operational costs than existing vehicles. Science Enabled by SeaRover - SeaRover's unique design and autonomous capability provides several advantages compared to traditional autonomous underwater vehicles (AUV's) and crewed surface vessels: (1) Near surface sampling: SeaRover can sample within the top 1-2 meters. This is difficult to do with crewed vessels because of draft and perturbations from the hull. (2) Adaptive monitoring of dynamic events: SeaRover will be capable of intelligent decision making, as well as real-time remote control. This will enable highly-responsive autonomous tracking of moving phenomena (e.g., algal bloom). (3) Long term monitoring: SeaRover can be deployed for extended periods of time, allowing it to be used for longitudinal baseline studies. SeaRover will represent an advance over existing platforms in terms of: (1) Mobility: operational range from 10-1000 km, GPS accuracy, trajectory control with meter precision, and launch in hours. (2) Duration: from days up to months. (3) Payload and Power: accommodate approximately 100 kg for a 6m hull. Its surface design will allow access to wind and sun energy. (4) Communication: radio, wireless, satellite, direct data return. (5) Operational Cost: target costs are $2K/day (24 hour operation), with no onboard operator. (6) Recovery/Reusability: autonomous return to safe harbor provides sample return and on-base maintenance. Large science and power

Ice2sea - the future glacial contribution to sea-level rise

NASA Astrophysics Data System (ADS)

Vaughan, D. G.; Ice2sea Consortium

2009-04-01

The melting of continental ice (glaciers, ice caps and ice sheets) is a substantial source of current sea-level rise, and one that is accelerating more rapidly than was predicted even a few years ago. Indeed, the most recent report from Intergovernmental Panel on Climate Change highlighted that the uncertainty in projections of future sea-level rise is dominated by uncertainty concerning continental ice, and that understanding of the key processes that will lead to loss of continental ice must be improved before reliable projections of sea-level rise can be produced. Such projections are urgently required for effective sea-defence management and coastal adaptation planning. Ice2sea is a consortium of European institutes and international partners seeking European funding to support an integrated scientific programme to improve understanding concerning the future glacial contribution to sea-level rise. This includes improving understanding of the processes that control, past, current and future sea-level rise, and generation of improved estimates of the contribution of glacial components to sea-level rise over the next 200 years. The programme will include targeted studies of key processes in mountain glacier systems and ice caps (e.g. Svalbard), and in ice sheets in both polar regions (Greenland and Antarctica) to improve understanding of how these systems will respond to future climate change. It will include fieldwork and remote sensing studies, and develop a suite of new, cross-validated glacier and ice-sheet model. Ice2sea will deliver these results in forms accessible to scientists, policy-makers and the general public, which will include clear presentations of the sources of uncertainty. Our aim is both, to provide improved projections of the glacial contribution to sea-level rise, and to leave a legacy of improved tools and techniques that will form the basis of ongoing refinements in sea-level projection. Ice2sea will provide exciting opportunities for many

Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins

NASA Astrophysics Data System (ADS)

Cronin, Thomas M.; O'Regan, Matt; Pearce, Christof; Gemery, Laura; Toomey, Michael; Semiletov, Igor; Jakobsson, Martin

2017-09-01

Deglacial (12.8-10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM; ˜ 24 kiloannum or ka) minimum sea level of ˜ 125-130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ˜ 400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42-47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.

Perception of global image contrast involves transparent spatial filtering and the integration and suppression of local contrasts (not RMS contrast)

PubMed Central

2017-01-01

When adjusting the contrast setting on a television set, we experience a perceptual change in the global image contrast. But how is that statistic computed? We addressed this using a contrast-matching task for checkerboard configurations of micro-patterns in which the contrasts and spatial spreads of two interdigitated components were controlled independently. When the patterns differed greatly in contrast, the higher contrast determined the perceived global contrast. Crucially, however, low contrast additions of one pattern to intermediate contrasts of the other caused a paradoxical reduction in the perceived global contrast. None of the following metrics/models predicted this: max, linear sum, average, energy, root mean squared (RMS), Legge and Foley. However, a nonlinear gain control model, derived from contrast detection and discrimination experiments, incorporating wide-field summation and suppression, did predict the results with no free parameters, but only when spatial filtering was removed. We conclude that our model describes fundamental processes in human contrast vision (the pattern of results was the same for expert and naive observers), but that above threshold—when contrast pedestals are clearly visible—vision's spatial filtering characteristics become transparent, tending towards those of a delta function prior to spatial summation. The global contrast statistic from our model is as easily derived as the RMS contrast of an image, and since it more closely relates to human perception, we suggest it be used as an image contrast metric in practical applications. PMID:28989735

Possible sea sediments due to glaciofluvial activity in Elysium Planitia, Mars

NASA Astrophysics Data System (ADS)

Nussbaumer, J.

Observations of fluvial morphologies in southern Elysium Planitia strongly supports the hypothesis that water substantially affected this region during the relatively recent geologic past. As of yet, however, the extent of a standing body of water has been speculative. The observation of zig-zag features potentially analogous to those observed near the Wadden Sea on Earth [see 1] may help show in more detail the origin, activity, and fate of water in this region of Mars. These terrestrial analogs could constrain environmental scenarios concerning the formation of these features. We present a geomorphologic map of central Elysium Planitia, that aids in our interpretation of potentially site-specific depositional/erosional morphologies. Positive relief zig-zag features within the Medusae Fossae Formation (Themis Image V05875001) resemble similar structures on Earth observed at shorelines of flat regions. Glaciofluvial activity is indicated by linear features resembling straight glacial flutings, which could form aeolian yardangs subsequently. The flutings are associated with branches of inverted fluvial channels (Images Themis V05588002, MOC e1800307). Their excavated positive relief (height ~40 m) indicates, that the adjacent material was eroded by sublimation or aeolian activity. The channels possibly resemble ice marginal channels. A high resolution Digital Terrain Model of one of the channels suggests, that one channel is possibly running upslope. Fluvial processes could have operated at one location at one time, and glacial processes at another location at another time [2]. A glacial drainage system [see 3] is a possible terrestrial analog for one inverted fluvial channel on Mars (Themis Image V05875001). Flutings occur on the foreland of many glaciers and their length may provide important evidence for rapid advance over substantial distances. Flutings are the product of subglacial erosion and transport processes [4]. By assigning the different environmental

SEAS Classroom to Sea Labs: New Directions for Ridge 2000 Communitywide Education Outreach

NASA Astrophysics Data System (ADS)

Goehring, L.

2005-12-01

Lessons learned from the two year SEAS pilot program emphasize that student participation in deep-sea research is an important motivator in student learning. Further, SEAS students experience a paradigm shift in understanding evidence-based reasoning and the process of scientific discovery. At the same time, we have learned that fostering authentic student investigations within the confines of the academic year is challenging and only fits classrooms with some academic flexibility. As a result, this year, SEAS will focus on the new Classroom to Sea Lab as a means to help foster student inquiry in the secondary school science classroom. The Classroom to Sea Lab invites student participation in deep-sea research but does so without requiring students to identify and propose suitable sea-going experiments. Classroom to Sea labs are designed to feature current deep-sea research, and emphasize critical skills in laboratory techniques, data collection and analysis, and scientific reporting. Labs are conducted in the classroom (by students) and at sea (by scientists for the students), resulting in parallel datasets for comparison. Labs also feature the work of practicing scientists. An annual Classroom to Sea Report Fair invites students to summarize their findings and submit written analyses for scientist feedback and prizes, emphasizing the importance of communications skills in science. This year, the SEAS program will feature the Shallow-water vs. Deep-sea Vent Mussel Classroom to Sea lab. In this lab, students explore differences in mussel anatomy and feeding strategies, and understand how chemosynthetic symbionts function in this animal. The lab instructs students to dissect shallow-water mussels and measure the proportion of gill tissue to total body tissue. Students are also instructed to download a dataset of vent mussel measurements and compare average proportions. Finally, students are invited to submit their analyses of the lab to the on-line Report Fair

Two Sea-Level Challenges

NASA Astrophysics Data System (ADS)

Galvin, C.

2008-12-01

"No place on the sandy ocean shores of the world has been shown to be eroding because of sea level rise." This statement appeared nearly 19 years ago in bold print at the top of the page in a brief article published in Shore and Beach (Galvin,1990). The term "sea level rise" was defined in 1990 as follows: "In this statement, "sea level rise" has the meaning that the average person on the street usually attaches to that term. That is, sea level is rising; not, as in some places like the Mississippi River delta, land level is sinking." While still a subject of controversy, it is now (2008) increasingly plausible (Tornqvist et al,2008) that damage from Hurricane Katrina was significantly worse on the Mississippi River delta because floodwaters exploited wetlands and levees whose elevations had been lowered by decades of compaction in the underlying soil. (1) "Sea level" commonly appears in the literature as "relative sea level rise", occurring that way in 711 publications between 1980 and 2009 (GeoRef database on 8 Sep 08). "Relative sea level rise" does not appear in the 2005 AGI Glossary. The nearest Glossary term is "relative change in sea level", but that term occurs in only 12 publications between 1980 and 2009. The Glossary defines this term in a sequence stratigraphy sense, which infers that "relative sea level rise" is the sum of bottom subsidence and eustatic sea level rise. In plain English, "relative sea level rise" means "water depth increase". For present day coastal environments, "relative sea level rise" is commonly used where eustatic sea level rise is less than subsidence, that is, where the magnitude of actual sea level rise is smaller than the magnitude of subsidence. In that situation, "relative sea level rise" misleads both the average person and the scientist who is not a coastal geologist. Thus, the first challenge is to abandon "relative sea level rise" in favor of "water depth increase", in order that the words accurately descibe what happens

Revisiting venom of the sea anemone Stichodactyla haddoni: Omics techniques reveal the complete toxin arsenal of a well-studied sea anemone genus.

PubMed

Madio, Bruno; Undheim, Eivind A B; King, Glenn F

2017-08-23

More than a century of research on sea anemone venoms has shown that they contain a diversity of biologically active proteins and peptides. However, recent omics studies have revealed that much of the venom proteome remains unexplored. We used, for the first time, a combination of proteomic and transcriptomic techniques to obtain a holistic overview of the venom arsenal of the well-studied sea anemone Stichodactyla haddoni. A purely search-based approach to identify putative toxins in a transcriptome from tentacles regenerating after venom extraction identified 508 unique toxin-like transcripts grouped into 63 families. However, proteomic analysis of venom revealed that 52 of these toxin families are likely false positives. In contrast, the combination of transcriptomic and proteomic data enabled positive identification of 23 families of putative toxins, 12 of which have no homology known proteins or peptides. Our data highlight the importance of using proteomics of milked venom to correctly identify venom proteins/peptides, both known and novel, while minimizing false positive identifications from non-toxin homologues identified in transcriptomes of venom-producing tissues. This work lays the foundation for uncovering the role of individual toxins in sea anemone venom and how they contribute to the envenomation of prey, predators, and competitors. Proteomic analysis of milked venom combined with analysis of a tentacle transcriptome revealed the full extent of the venom arsenal of the sea anemone Stichodactyla haddoni. This combined approach led to the discovery of 12 entirely new families of disulfide-rich peptides and proteins in a genus of anemones that have been studied for over a century. Copyright © 2017 Elsevier B.V. All rights reserved.

Impact of Desiccation of Aral Sea on the Regional Climate of Central Asia Using WRF Model

NASA Astrophysics Data System (ADS)

Sharma, Ashish; Huang, Huei-Ping; Zavialov, Peter; Khan, Valentina

2018-01-01

This study explores the impacts of the desiccation of the Aral Sea and large-scale climate change on the regional climate of Central Asia in the post-1960 era. A series of climate downscaling experiments for the 1960's and 2000's decades were performed using the Weather Research and Forecast model at 12-km horizontal resolution. To quantify the impacts of the changing surface boundary condition, a set of simulations with an identical lateral boundary condition but different extents of the Aral Sea were performed. It was found that the desiccation of the Aral Sea leads to more snow (and less rain) as desiccated winter surface is relatively much colder than water surface. In summer, desiccation led to substantial warming over the Aral Sea. These impacts were largely confined to within the area covered by the former Aral Sea and its immediate vicinity, although desiccation of the Sea also led to minor cooling over the greater Central Asia in winter. A contrasting set of simulations with an identical surface boundary condition but different lateral boundary conditions produced more identifiable changes in regional climate over the greater Central Asia which was characterized by a warming trend in both winter and summer. Simulations also showed that while the desiccation of the Aral Sea has significant impacts on the local climate over the Sea, the climate over the greater Central Asia on inter-decadal time scale was more strongly influenced by the continental or global-scale climate change on that time scale.

Multi-model seasonal forecast of Arctic sea-ice: forecast uncertainty at pan-Arctic and regional scales

NASA Astrophysics Data System (ADS)

Blanchard-Wrigglesworth, E.; Barthélemy, A.; Chevallier, M.; Cullather, R.; Fučkar, N.; Massonnet, F.; Posey, P.; Wang, W.; Zhang, J.; Ardilouze, C.; Bitz, C. M.; Vernieres, G.; Wallcraft, A.; Wang, M.

2017-08-01

Dynamical model forecasts in the Sea Ice Outlook (SIO) of September Arctic sea-ice extent over the last decade have shown lower skill than that found in both idealized model experiments and hindcasts of previous decades. Additionally, it is unclear how different model physics, initial conditions or forecast post-processing (bias correction) techniques contribute to SIO forecast uncertainty. In this work, we have produced a seasonal forecast of 2015 Arctic summer sea ice using SIO dynamical models initialized with identical sea-ice thickness in the central Arctic. Our goals are to calculate the relative contribution of model uncertainty and irreducible error growth to forecast uncertainty and assess the importance of post-processing, and to contrast pan-Arctic forecast uncertainty with regional forecast uncertainty. We find that prior to forecast post-processing, model uncertainty is the main contributor to forecast uncertainty, whereas after forecast post-processing forecast uncertainty is reduced overall, model uncertainty is reduced by an order of magnitude, and irreducible error growth becomes the main contributor to forecast uncertainty. While all models generally agree in their post-processed forecasts of September sea-ice volume and extent, this is not the case for sea-ice concentration. Additionally, forecast uncertainty of sea-ice thickness grows at a much higher rate along Arctic coastlines relative to the central Arctic ocean. Potential ways of offering spatial forecast information based on the timescale over which the forecast signal beats the noise are also explored.

Impact of Albedo Contrast Between Cirrus and Boundary-Layer Clouds on Climate Sensitivity

NASA Technical Reports Server (NTRS)

Chou, Ming-Dah; Lindzen, R. S.; Hou, A. Y.; Lau, William K. M. (Technical Monitor)

2001-01-01

In assessing the iris effect suggested by Lindzen et al. (2001), Fu et al. (2001) found that the response of high-level clouds to the sea surface temperature had an effect of reducing the climate sensitivity to external radiative forcing, but the effect was not as strong as LCH found. This weaker reduction in climate sensitivity was due to the smaller contrasts in albedos and effective emitting temperatures between cirrus clouds and the neighboring regions. FBH specified the albedos and the outgoing longwave radiation (OLR) in the LCH 3.5-box radiative-convective model by requiring that the model radiation budgets at the top of the atmosphere be consistent with that inferred from the Earth Radiation Budget Experiment (ERBE). In point of fact, the constraint by radiation budgets alone is not sufficient for deriving the correct contrast in radiation properties between cirrus clouds and the neighboring regions, and the approach of FBH to specifying those properties is, we feel inappropriate for assessing the iris effect.

Recognition memory reveals just how CONTRASTIVE contrastive accenting really is

PubMed Central

Fraundorf, Scott H.; Watson, Duane G.; Benjamin, Aaron S.

2010-01-01

The effects of pitch accenting on memory were investigated in three experiments. Participants listened to short recorded discourses that contained contrast sets with two items (e.g. British scientists and French scientists); a continuation specified one item from the set. Pitch accenting on the critical word in the continuation was manipulated between non-contrastive (H* in the ToBI system) and contrastive (L+H*). On subsequent recognition memory tests, the L+H* accent increased hits to correct statements and correct rejections of the contrast item (Experiments 1–3), but did not impair memory for other parts of the discourse (Experiment 2). L+H* also did not facilitate correct rejections of lures not in the contrast set (Experiment 3), indicating that contrastive accents do not simply strengthen the representation of the target item. These results suggest comprehenders use pitch accenting to encode and update information about multiple elements in a contrast set. PMID:20835405

Collaborative, International Efforts at Estimating Arctic Sea Ice Processes During IPY (Invited)

NASA Astrophysics Data System (ADS)

Overland, J. E.; Eicken, H.; Wiggins, H. V.

2009-12-01

Planning for the fourth IPY was conducted during a time of moderate decadal change in the Arctic. However, after this initial planning was completed, further rapid changes were seen, including a 39 % reduction in summer sea ice extent in 2007 and 2008 relative to the 1980s-1990s, loss of multi-year sea ice, and increased sea ice mobility. The SEARCH and DAMOCLES Programs endeavored to increase communication within the research community to promote observations and understanding of rapidly changing Arctic sea ice conditions during IPY. In May 2008 a web-based Sea Ice Outlook was initiated, an international collaborative effort that synthesizes, on a monthly basis throughout the summer, the community’s projections for September arctic sea ice extent. Each month, participating investigators provided a projection for the mean September sea ice extent based on spring and early summer data, along with a rationale for their estimates. The Outlook continued in summer of 2009. The Outlook is a method of rapidly synthesizing a broad range of remote sensing and field observations collected at the peak of the IPY, with analysis methods ranging from heuristic to statistical to ice-ocean model ensemble runs. The 2008 Outlook was a success with 20 groups participating and providing a median sea ice extent projection from June 2008 data of 4.4 million square kilometers (MSQK)—near the observed extent in September 2008 of 4.7 MSQK, and well below the 1979-2007 climatological extent of 6.7 MSQK. More importantly, the contrast of sea ice conditions and atmospheric forcing in 2008 compared to 2007 provided clues to the future fate of arctic sea ice. The question was whether the previous loss of multi-year ice and delay in autumn freeze-up in 2007 would allow sufficient winter thickening of sea ice to last through the summer 2008, promoting recovery from the 2007 minimum, or whether most first-year sea ice would melt out as in 2005 and 2007, resulting in a new record minimum extent

Integrative study of a new cold-seep mussel (Mollusca: Bivalvia) associated with chemosynthetic symbionts in the Marmara Sea

NASA Astrophysics Data System (ADS)

Ritt, Bénédicte; Duperron, Sébastien; Lorion, Julien; Sara Lazar, Cassandre; Sarrazin, Jozée

2012-09-01

Recently, small Idas-like mussels have been discovered living on carbonate crusts associated with cold-seeps in the Marmara Sea. These mussels, here referred to as Idas-like nov. sp., differ morphologically and genetically from another species identified as Idas aff. modiolaeformis, living in the same type of ecosystem in the Nile Deep-Sea Fan (eastern Mediterranean Sea). A phylogenetic analysis confirms the distinction between the two species, which belong to highly divergent lineages. Carbon stable isotope values, as well as the detection of thiotroph-related bacteria in the gill tissue, support the presence of a symbiotic, thiotroph-derived nutrition. In contrast, Idas aff. modiolaeformis displays six different types of symbionts. Finally our size-frequency data suggest that the recruitment is continuous in the examined area. The present study extends the documented distribution of symbiont-bearing mussels to the Marmara Sea, and contributes to the characterisation of biological communities in this recently explored area.

Impact of High Seas Closure on Food Security in Low Income Fish Dependent Countries

PubMed Central

Teh, Louise S. L.; Lam, Vicky W. Y.; Cheung, William W. L.; Miller, Dana; Teh, Lydia C. L.; Sumaila, U. Rashid

2016-01-01

We investigate how high seas closure will affect the availability of commonly consumed food fish in 46 fish reliant, and/or low income countries. Domestic consumption of straddling fish species (fish that would be affected by high seas closure) occurred in 54% of the assessed countries. The majority (70%) of countries were projected to experience net catch gains following high seas closure. However, countries with projected catch gains and that also consumed the straddling fish species domestically made up only 37% of the assessed countries. In contrast, much fewer countries (25%) were projected to incur net losses from high seas closure, and of these, straddling species were used domestically in less than half (45%) of the countries. Our findings suggest that, given the current consumption patterns of straddling species, high seas closure may only directly benefit the supply of domestically consumed food fish in a small number of fish reliant and/or low income countries. In particular, it may not have a substantial impact on improving domestic fish supply in countries with the greatest need for improved access to affordable fish, as only one third of this group used straddling fish species domestically. Also, food security in countries with projected net catch gains but where straddling fish species are not consumed domestically may still benefit indirectly via economic activities arising from the increased availability of non-domestically consumed straddling fish species following high seas closure. Consequently, this study suggests that high seas closure can potentially improve marine resource sustainability as well as contribute to human well-being in some of the poorest and most fish dependent countries worldwide. However, caution is required because high seas closure may also negatively affect fish availability in countries that are already impoverished and fish insecure. PMID:28033359

Impact of High Seas Closure on Food Security in Low Income Fish Dependent Countries.

PubMed

Teh, Louise S L; Lam, Vicky W Y; Cheung, William W L; Miller, Dana; Teh, Lydia C L; Sumaila, U Rashid

2016-01-01

We investigate how high seas closure will affect the availability of commonly consumed food fish in 46 fish reliant, and/or low income countries. Domestic consumption of straddling fish species (fish that would be affected by high seas closure) occurred in 54% of the assessed countries. The majority (70%) of countries were projected to experience net catch gains following high seas closure. However, countries with projected catch gains and that also consumed the straddling fish species domestically made up only 37% of the assessed countries. In contrast, much fewer countries (25%) were projected to incur net losses from high seas closure, and of these, straddling species were used domestically in less than half (45%) of the countries. Our findings suggest that, given the current consumption patterns of straddling species, high seas closure may only directly benefit the supply of domestically consumed food fish in a small number of fish reliant and/or low income countries. In particular, it may not have a substantial impact on improving domestic fish supply in countries with the greatest need for improved access to affordable fish, as only one third of this group used straddling fish species domestically. Also, food security in countries with projected net catch gains but where straddling fish species are not consumed domestically may still benefit indirectly via economic activities arising from the increased availability of non-domestically consumed straddling fish species following high seas closure. Consequently, this study suggests that high seas closure can potentially improve marine resource sustainability as well as contribute to human well-being in some of the poorest and most fish dependent countries worldwide. However, caution is required because high seas closure may also negatively affect fish availability in countries that are already impoverished and fish insecure.

Detecting genotypic changes associated with selective mortality at sea in Atlantic salmon: polygenic multilocus analysis surpasses genome scan.

PubMed

Bourret, Vincent; Dionne, Mélanie; Bernatchez, Louis

2014-09-01

Wild populations of Atlantic salmon have declined worldwide. While the causes for this decline may be complex and numerous, increased mortality at sea is predicted to be one of the major contributing factors. Examining the potential changes occurring in the genome-wide composition of populations during this migration has the potential to tease apart some of the factors influencing marine mortality. Here, we genotyped 5568 SNPs in Atlantic salmon populations representing two distinct regional genetic groups and across two cohorts to test for differential allelic and genotypic frequencies between juveniles (smolts) migrating to sea and adults (grilses) returning to freshwater after 1 year at sea. Given the complexity of the traits potentially associated with sea mortality, we contrasted the outcomes of a single-locus F(ST) based genome scan method with a new multilocus framework to test for genetically based differential mortality at sea. While numerous outliers were identified by the single-locus analysis, no evidence for parallel, temporally repeated selection was found. In contrast, the multilocus approach detected repeated patterns of selection for a multilocus group of 34 covarying SNPs in one of the two populations. No significant pattern of selective mortality was detected in the other population, suggesting different causes of mortality among populations. These results first support the hypothesis that selection mainly causes small changes in allele frequencies among many covarying loci rather than a small number of changes in loci with large effects. They also point out that moving away from the a strict 'selective sweep paradigm' towards a multilocus genetics framework may be a more useful approach for studying the genomic signatures of natural selection on complex traits in wild populations. © 2014 John Wiley & Sons Ltd.

Oceanization starts from below during continental rupturing in the northern Red Sea