Strontium-90 concentration in waters of the eastern Carribbean Sea

Vertical structure of the strontium-90 concentration field and its relation to hydrology of waters are described on the basis of investigations in the Caribbean Sea during Cruises 6 and 7 of R/V Akademik Vernadsky (1972-1973). Vertical velocity and the coefficient of vertical turbulent diffusion are calculated for the eastern Caribbean Sea from strontium-90 concentration and salinity data.

Ice and chlorophyll a concentration and mesozooplankton characteristics during two 'On Thin Ice' cruises, northern Svalbard waters

The spatial variation in mesozooplankton biomass, abundance and species composition in relation to oceanography was studied in different climatic regimes (warm Atlantic vs. cold Arctic) in northern Svalbard waters. Relationships between the zooplankton community and various environmental factors (salinity, temperature, sampling depth, bottom depth, sea-ice concentrations, algal biomass and bloom stage) were established using multivariate statistics. Our study demonstrated that variability in the physical environment around Svalbard had measurable effect on the pelagic ecosystem. Differences in bottom depth and temperature-salinity best explained more than 40% of the horizontal variability in mesozooplankton biomass (DM/m**2) after adjusting for seasonal variability. Salinity and temperature also explained much (21% and 15%, respectively) of the variability in mesozooplankton vertical distribution (ind./m**3) in August. Algal bloom stage, chlorophyll-a biomass, and depth stratum accounted for additional 17% of the overall variability structuring vertical zooplankton distribution. Three main zooplankton communities were identified, including Atlantic species Fritillaria borealis, Oithona atlantica, Calanus finmarchicus, Themisto abyssorum and Aglantha digitale; Arctic species Calanus glacialis, Gammarus wilkitzkii, Mertensia ovum and Sagitta elegans; and deeper-water inhabitants Paraeuchaeta spp., Spinocalanus spp., Aetideopsis minor, Mormonilla minor, Scolecithricella minor, Gaetanus (Gaidius) tenuispinus, Ostracoda, Scaphocalanus brevicornis and Triconia borealis. Zooplankton biomasses in Atlantic- and Arctic-dominated water masses were similar, but biological ''hot-spots'' were associated with Arctic communities.

Area-averaged mean seasonal cycles of chlorophyll-a concentration, sea surface temperature, alongshore wind stress, westward wind speed and dust component of the aerosol optical depth at 550 nm

Nutrient supply in the area off Northwest Africa is mainly regulated by two processes, coastal upwelling and deposition of Saharan dust. In the present study, both processes were analyzed and evaluated by different methods, including cross-correlation, multiple correlation, and event statistics, using remotely sensed proxies of the period from 2000 to 2008 to investigate their influence on the marine environment. The remotely sensed chlorophyll-a concentration was used as a proxy for the phytoplankton biomass stimulated by nutrient supply into the euphotic zone from deeper water layers and from the atmosphere. Satellite-derived alongshore wind stress and sea-surface temperature were applied as proxies for the strength and reflection of coastal upwelling processes. The westward wind and the dust component of the aerosol optical depth describe the transport direction of atmospheric dust and the atmospheric dust column load. Alongshore wind stress and induced upwelling processes were most significantly responsible for the surface chlorophyll-a variability, accounting for about 24% of the total variance, mainly in the winter and spring due to the strong north-easterly trade winds. The remotely sensed proxies allowed determination of time lags between biological response and its forcing processes. A delay of up to 16 days in the surface chlorophyll-a concentration due to the alongshore wind stress was determined in the northern winter and spring. Although input of atmospheric iron by dust storms can stimulate new phytoplankton production in the study area, only 5% of the surface chlorophyll-a variability could be ascribed to the dust component in the aerosol optical depth. All strong desert storms were identified by an event statistics in the time period from 2000 to 2008. The 57 strong storms were studied in relation to their biological response. Six events were clearly detected in which an increase of chlorophyll-a was caused by Saharan dust input and not by coastal upwelling processes. Time lags of <8 days, 8 days, and 16 days were determined. An increase in surface chlorophyll-a concentration of up to 2.4 mg m**3 after dust storms in which the dust component of the aerosol optical depth was up to 0.9 was observed.

(Table 1) Concentration of persistent organic pollutants in blood plasma of glaucous gulls (Larus hyperboreus) from Bjørnøya

Unpredictable changes in the environment stimulate the avian hypothalamo-pituitary-adrenal axis to produce corticosterone, which induces behavioural and metabolic changes that enhance survival in the face of adverse environmental conditions. In addition to profound environmental perturbations, such as severe weather conditions and unpredictable food shortages, many Arctic-breeding birds are also confronted with chronic exposure to persistent organic pollutants (POPs), some of which are known to disrupt endocrine processes. This study investigated the adrenocortical function of a top predator in the Arctic marine environment, the glaucous gull (Larus hyperboreus). High concentrations of organochlo-rines, brominated flame retardants and metabolically-derived products in blood plasma of incubating glaucous gulls were associated with high baseline corticosterone concentrations in both sexes and a reduced stress response in males. Contaminant-related changes in corticosterone concentration occurred over and above differences in body condition and seasonal variation. Chronically high corticosterone concentrations and/or a compromised adrenocortical response to stress can have negative effects on the health of an individual. The results of the present study suggest that exposure to POPs may increase the vulnerability of glaucous gulls to environmental stressors and thus could potentially compromise their ability to adapt to the rapidly changing environmental conditions associated with climate change that are currently seen in the Arctic.

Phytoplankton biomass, chlorophyll concentration, and variability of lipid content in Calanus euxinus in the Black Sea in June 1991

During field studies relationships between chlorophyll concentrations, phytoplankton biomass (total, individual sizes and species) and level of accumulation of total lipids, wax esters, triacylglycerols, and phospholipids in C. euxinus (copepodites V and females) were studied. These relationships allowed to display not only simple trophic relations between isolated parts of the C. euxinus population and phytoplankton, but also selective role of individual algae species in forming lipid reserves too. Besides it was found that geographical variability of chlorophyll concentration and phytoplankton biomass correlates closely only with those lipid fractions (wax esters and phospholipids) of C. euxinus, which accumulated and kept in a body for a fairly long time. No correlation was found between phytoplankton and for rapidly metabolized triacylglycerols, which have to be utilized within few hours.

(Table 1) Seasonal sea ice concentration and the observed changes from 1972 to 2007 for the Southern Beaufort Sea

A reliable data set of Arctic sea ice concentration based on satellite observations exists since 1972. Over this time period of 36 years western arctic temperatures have increased; the temperature rise varies significantly from one season to another and over multi-year time scales. In contrast to most of Alaska, however, on the North Slope the warming continued after 1976, when a circulation change occurred, as expressed in the PDO index. The mean temperature increase for Barrow over the 36-year period was 2.9°C, a very substantial change. Wind speeds increased by 18% over this time period, however, the increase were non-linear and showed a peak in the early 1990s. The sea ice extent of the Arctic Ocean has decreased strongly in recent years, and in September 2007 a new record in the amount of open water was recorded in the Western Arctic. We observed for the Southern Beaufort Sea a fairly steady increase in the mean annual amount of open water from 14% in 1972 to 39% in 2007, as deduced from the best linear fit. In late summer the decrease is much larger, and September has, on average, the least ice concentration (22%), followed by August (35%) and October (54%). The correlation coefficient between mean annual values of temperature and sea ice concentration was 0.84. On a monthly basis, the best correlation coefficient was found in October with 0.88. However, the relationship between winter temperatures and the sea ice break-up in summer was weak. While the temperature correlated well with the CO2 concentration (r=0.86), the correlation coefficient between CO2 and sea ice was lower (r=-0.68). After comparing the ice concentration with 17 circulation indices, the best relation was found with the Pacific Circulation Index (r=-0.59).

Age models and summer sea surface temperature and winter sea ice concentration for the EPILOG-LGM time slice in the Pacific Southern Ocean

Sea surface temperatures and sea-ice extent are the most critical variables to evaluate the Southern Ocean paleoceanographic evolution in relation to the development of the global carbon cycle, atmospheric CO2 variability and ocean-atmosphere circulation. In contrast to the Atlantic and the Indian sectors, the Pacific sector of the Southern Ocean has been insufficiently investigated so far. To cover this gap of information we present diatom-based estimates of summer sea surface temperature (SSST) and winter sea-ice concentration (WSI) from 17 sites in the polar South Pacific to study the Last Glacial Maximum (LGM) at the EPILOG time slice (19,000-23,000 cal. years BP). Applied statistical methods are the Imbrie and Kipp Method (IKM) and the Modern Analog Technique (MAT) to estimate temperature and sea-ice concentration, respectively. Our data display a distinct LGM east-west differentiation in SSST and WSI with steeper latitudinal temperature gradients and a winter sea-ice edge located consistently north of the Pacific-Antarctic Ridge in the Ross sea sector. In the eastern sector of our study area, which is governed by the Amundsen Abyssal Plain, the estimates yield weaker latitudinal SSST gradients together with a variable extended winter sea-ice field. In this sector, sea-ice extent may have reached sporadically the area of the present Subantarctic Front at its maximum LGM expansion. This pattern points to topographic forcing as major controller of the frontal system location and sea-ice extent in the western Pacific sector whereas atmospheric conditions like the Southern Annular Mode and the ENSO affected the oceanographic conditions in the eastern Pacific sector. Although it is difficult to depict the location and the physical nature of frontal systems separating the glacial Southern Ocean water masses into different zones, we found a distinct temperature gradient in latitudes straddled by the modern Southern Subtropical Front. Considering that the glacial temperatures north of this zone are similar to the modern, we suggest that this represents the Glacial Southern Subtropical Front (GSSTF), which delimits the zone of strongest glacial SSST cooling (>4K) to its North. The southern boundary of the zone of maximum cooling is close to the glacial 4°C isotherm. This isotherm, which is in the range of SSST at the modern Antarctic Polar Front (APF), represents a circum-Antarctic feature and marks the northern edge of the glacial Antarctic Circumpolar Current (ACC). We also assume that a glacial front was established at the northern average winter sea ice edge, comparable with the modern Southern Antarctic Circumpolar Current Front (SACCF). During the glacial, this front would be located in the area of the modern APF. The northward deflection of colder than modern surface waters along the South American continent leads to a significant cooling of the glacial Humboldt Current surface waters (4-8K), which affects the temperature regimes as far north as into tropical latitudes. The glacial reduction of ACC temperatures may also result in the significant cooling in the Atlantic and Indian Southern Ocean, thus may enhance thermal differentiation of the Southern Ocean and Antarctic continental cooling. Comparison with temperature and sea ice simulations for the last glacial based on numerical simulations show that the majority of modern models overestimate summer and winter sea ice cover and that there exists few models that reproduce our temperature data rather well.

Adenylate concentration and energy charge in different thallus regions and after UV radiation in brown, red and green algae

A method was developed to extract adenine nucleotides AMP, ADP, and ATP from marine macroalgal tissue to gain information on the cellular energy charge. Quantification was carried out by high performance liquid chromatography (HPLC). Three species from the rocky shore of the island of Helgoland (German Bight) were examined: Laminaria saccharina (Phaeophyta), Chondrus crispus (Rhodophyta), and Ulva lactuca (Chlorophyta). In L. saccharina and C. crispus, the adenylate energy charge (AEC) was determined in different thallus regions. AEC varied in relation to tissue age and function. Higher AEC values typically occurred in thallus regions with meristematic activity. Furthermore, L. saccharina and U. lactuca were exposed to UV-A and elevated UV-B radiation. The AEC was calculated and the maximal quantum yield of photosystem II (Fv/Fm) was determined as indicators for UV stress. In both species, the AEC remained at high values (0.72 ± 0.04), while Fv/Fm dropped rapidly. The results show that the photosynthesis of the phaeophyte is more resistant to UV radiation than the chlorophyte.

Under-ice fauna, sea-ice concentration, sea-ice thickness and under-ice water parameters from the Eurasian central Arctic Ocean during POLARSTERN cruise ARK-XXVII/3 (PS80) in August-September 2012

Arctic sea-ice decline is expected to have a significant impact on Arctic marine ecosystems. Ice-associated fauna play a key role in this context because they constitute a unique part of Arctic biodiversity and transmit carbon from sea-ice algae into pelagic and benthic food webs. Our study presents the first regional-scale record of under-ice faunal distribution and the environmental characteristics of under-ice habitats throughout the Eurasian Basin. Sampling was conducted with a Surface and Under-Ice Trawl, equipped with a sensor array recording ice thickness and other physical parameters during trawling. We identified 2 environmental regimes, broadly coherent with the Nansen and Amundsen Basins. The Nansen Basin regime was distinguished from the Amundsen Basin regime by heavier sea-ice conditions, higher surface salinities and higher nitrate + nitrite concentrations. We found a diverse (28 species) under-ice community throughout the Eurasian Basin. Change in community structure reflected differences in the relative contribution of abundant species. Copepods (Calanus hyperboreus and C. glacialis) dominated in the Nansen Basin regime. In the Amundsen Basin regime, amphipods (Apherusa glacialis, Themisto libellula) dominated. Polar cod Boreogadus saida was present throughout the sampling area. Abrupt changes from a dominance of ice-associated amphipods at ice-covered stations to a dominance of pelagic amphipods (T. libellula) at nearby ice-free stations emphasised the decisive influence of sea ice on small-scale patterns in the surface-layer community. The observed response in community composition to different environmental regimes indicates potential long-term alterations in Arctic marine ecosystems as the Arctic Ocean continues to change.