Abundance and size composition of ctenophore Mnemiopsis leidyi population in the Caspian Sea on 2001-06-24 to 2001-07-01

Abundance and size distribution of ctenophore Mnemiopsis leidyi in different parts of the Caspian Sea were studied in summer 2001 in relation to environmental conditions. In general, principal differences were found in M. leidyi abundance and population reproduction activity in northern-, middle- and southern Caspian waters. Ctenophore was practically absent in the northern Caspian. In the west of the middle Caspian Sea it penetrated far to the north demonstrating low reproduction activity. In the east the first single comb jellies were pointed out only in the most south of the region. In the warmest and most productive southern part of the Caspian Sea several zones of M. leidyi active breeding were found with total abundance exceeding 6000 #/m**2. Breeding activity and abundance of ctenophores increased here from the east to the west exceeding maximum values along the western coast of the southern Caspian Sea in regions of intensive sprat catching. Dependence of M. leidyi population development on temperature conditions was mentioned. On the base of remote sensed surface temperature, chlorophyll, and suspended mater distribution analysis possible ctenophore settling mechanisms by mesoscale dynamic structures were examined. Practical applications of obtained results are discussed for using effective biological methods to prevent catastrophic consequences of M. leidyi invasion to the Caspian Sea.

Composition of bottom sediments, rocks, and ores from the Tropical Atlantic

Geological features of some areas of the Tropical Atlantic (stratigraphy, tectonic structure, lithology, distribution of ore components in bottom sediments, petrography of bedrocks, etc.) are under consideration in the book. Regularities of concentration of trace elements in iron-manganese nodules, features of these nodules in bottom sediments, distribution of phosphorite nodules and other phosphorites have been studied. Much attention is paid to rocks of the ocean crust. A wide range of mineralization represented by magnetite, chromite, chalcopyrite, pyrite, pentlandite, and other minerals has been found.

Sea surface temperature and salinity reconstruction of sediment core GeoB3129-1

A sediment core from the western tropical Atlantic covering the last 21,000 yr has been analysed for centennial scale reconstruction of sea surface temperature (SST) and ice volume-corrected oxygen isotopic composition of sea water (delta18O(ivc-sw)) using Mg / Ca and delta18O of the shallow dwelling planktonic foraminifer Globigerinoides ruber (white). At a period between 15.5 and 17.5 kyr BP, the Mg / Ca SST and delta18O(ivc-sw), a proxy for sea surface salinity (SSS), reveals a warming of around 2.5 °C along with an increase in salinity. A second period of pronounced warming and SSS increase occurred between 11.6 and 13.5 kyr BP. Within age model uncertainties, both warming intervals were synchronous with air temperature increase over Antarctica and ice retreat in the southern South Atlantic and terminated with abrupt centennial scale SSS decrease and slight SST cooling in conjunction with interglacial reactivation of the meridional overturning circulation (MOC). We suggest that during these warm intervals, production of saline and warm water of the North Brazil Current resulted in pronounced heat and salt accumulation, and was associated with warming in the southern Atlantic, southward displacement of the intertropical convergence zone and weakened MOC. At the termination of the Younger Dryas and Heinrich event 1, intensification of cross-equatorial heat and salt transport caused centennial scale cooling and freshening of the western tropical Atlantic surface water. This study shows that the western tropical Atlantic served as a heat and salt reservoir during deglaciation. The sudden release of accumulated heat and salt at the end of Younger Drays and Heinrich event 1 may have contributed to the rapid reinvigoration of the Atlantic MOC.

Impact of elevated pCO2 on paralytic shellfish poisoning toxin content and composition in Alexandrium tamarense

Ocean acidification is considered a major threat to marine ecosystems and may particularly affect primary producers. Here we investigated the impact of elevated pCO2 on paralytic shellfish poisoning toxin (PST) content and composition in two strains of Alexandrium tamarense, Alex5 and Alex2. Experiments were carried out as dilute batch to keep carbonate chemistry unaltered over time. We observed only minor changes with respect to growth and elemental composition in response to elevated pCO2. For both strains, the cellular PST content, and in particular the associated cellular toxicity, was lower in the high CO2 treatments. In addition, Alex5 showed a shift in its PST composition from a nonsulfated analogue towards less toxic sulfated analogues with increasing pCO2. Transcriptomic analyses suggest that the ability of A. tamarense to maintain cellular homeostasis is predominantly regulated on the post-translational level rather than on the transcriptomic level. Furthermore, genes associated to secondary metabolite and amino acid metabolism in Alex5 were down-regulated in the high CO2 treatment, which may explain the lower PST content. Elevated pCO2 also induced up-regulation of a putative sulfotransferase sxtN homologue and a substantial down-regulation of several sulfatases. Such changes in sulfur metabolism may explain the shift in PST composition towards more sulfated analogues. All in all, our results indicate that elevated pCO2 will have minor consequences for growth and elemental composition, but may potentially reduce the cellular toxicity of A. tamarense.

Alkenone composition, UK'37 index, and carbon, sulphur, nitrogen and element oxides of ODP Site 186-1151

Ocean Drilling Program (ODP) Site 1151 (Sacks, Suyehiro, Acton, et al., 2000, doi:10.2973/odp.proc.ir.186.2000) is located in an area where the surface water mass is influenced by both the Kuroshio and Oyashio Currents. The site also receives a relatively high flux of detrital materials from riverine input from Honsyu Island and eolian input from Central and East Asia. We analyzed alkenones and alkenoates in the sediments to reconstruct alkenone unsaturation index (Uk'37)-based sea-surface temperature (SST), total organic carbon, and total nitrogen to estimate the terrigenous contribution by the C/N ratio during the last glacial-interglacial cycle. The major elements were also analyzed to examine the variation in terrigenous composition.

Effects of Ocean Acidification on the Ballast of Surface Aggregates Sinking through the Twilight Zone

The dissolution of CaCO3 is one of the ways ocean acidification can, potentially, greatly affect the ballast of aggregates. A diminution of the ballast could reduce the settling speed of aggregates, resulting in a change in the carbon flux to the deep sea. This would mean lower amounts of more refractory organic matter reaching the ocean floor. This work aimed to determine the effect of ocean acidification on the ballast of sinking surface aggregates. Our hypothesis was that the decrease of pH will increase the dissolution of particulate inorganic carbon ballasting the aggregates, consequently reducing their settling velocity and increasing their residence time in the upper twilight zone. Using a new methodology for simulation of aggregate settling, our results suggest that future pCO2 conditions can significantly change the ballast composition of sinking aggregates. The change in aggregate composition had an effect on the size distribution of the aggregates, with a shift to smaller aggregates. A change also occurred in the settling velocity of the particles, which would lead to a higher residence time in the water column, where they could be continuously degraded. In the environment, such an effect would result in a reduction of the carbon flux to the deep-sea. This reduction would impact those benthic communities, which rely on the vertical flow of carbon as primary source of energy.

Sediment composition in NE Greenland Fjords, Shelf, and Slope

In order to document changes in Holocene glacier extent and activity in NE Greenland (~73° N) we study marine sediment records that extend from the fjords (PS2631 and PS2640), across the shelf (PS2623 and PS2641), to the Greenland Sea (JM07-174GC). The primary bedrock geology of the source areas is the Caledonian sediment outcrop, including Devonian red beds, plus early Neoproterozoic gneisses and early Tertiary volcanics. We examine the variations in colour (CIE*), grain size, and bulk mineralogy (from X-ray diffraction of the <2 mm sediment fraction). Fjord core PS2640 in Sofia Sund, with a marked red hue, is distinct in grain size, colour and mineralogy from the other fjord and shelf cores. Five distinct grain-size modes are distinguished of which only one is associated with a coarse ice-rafting signal - this mode is rare in the mid- and late Holocene. A sediment unmixing program (SedUnMixMC) is used to characterize down-core changes in sediment composition based on the upper late Holocene sediments from cores PS2640 (Sofia Sund), PS2631 (Kaiser Franz Joseph Fjord) and PS2623 (south of Shannon Is), and surface samples from the Kara Sea (as an indicator of transport from the Russian Arctic shelves). Major changes in mineral composition are noted in all cores with possible coeval shifts centred c. 2.5, 4.5 and 7.5 cal. ka BP (±0.5 ka) but are rarely linked with changes in the grain-size spectra. Coarse IRD (>2 mm) and IRD-grain-size spectra are rare in the last 9-10 cal. ka BP and, in contrast with areas farther south (~68° N), there is no distinct IRD signal at the onset of neoglaciation. Our paper demonstrates the importance of the quantitative analysis of sediment properties in clarifying source to sink changes in glacial marine environments.

Dominant zooplankton species and microelements in plankton obtained from White Sea surface waters

Despite the fact that plankton plays an important role in biogeochemical processes in oceans, data on its elemental composition, particularly in shelf seas of the Arctic Ocean, have thus far been insufficient. This communication, which is devoted to a comparative analysis of the elemental composition of plankton and bottom sediments in the White Sea, is part of the comprehensive investigation of the region that is occurring in line with the International Project ''Land-Ocean Interaction in the Russian Arctic'' (LOIRA).

Geochemistry of surface sediment samples from the equatorial Atlantic south of the Azores

In order to recognize the distribution of hydrothermal tracers south of the Azores, a series of cores has been sampled during the GEOFAR cruise. The distribution of the Mn concentrations shows that the hydrothermal influence is maximum within and to the north-west of the Lucky Strike segment. North of the East-Azores Fracture Zone the sediments are enriched in Ba which could be derived from different sources. The chemical composition of the interstitial water shows that water advection is limited. Mn, Cu, Ni fluxes evaluated in one site have increased during isotopic stages 4 and 2 and the deglaciation.

Abundance and biomass of near-surface ichthioplankton in the Western Pacific

During Cruise 50 of R/V Vityaz ichthyoplankton in surface waters was collected by a neuston otter trawl for many days in four study areas of the Western Tropical Pacific. Obtained results describe quantitative distribution of ichthyoplankton and small fishes in surface waters. The near-surface layer of the ocean (about 30-40 cm thick) can be considered as a special biotope, its population forms an independent biocoenosis - hyponeuston. Species composition of this community (particularly, composition of fish components) in the tropical zone has been studied to some degree, but structure of the biocoenosis as well as biomass and quantitative relationships of species have not been investigated at all. In this paper the authors discuss the method of collecting surface samples that is quite suitable for quantitative calculations and also present the first results obtained using this method, which described quantitative distribution of ichthyoplankton and small fishes in surface waters.

(Table 1) Composition of manganese-iron accumulates in the Kiel Bay, western Baltic Sea

Manganese-iron accumulates in the Kiel Bay were investigated with regard to their occurence, chemical composition and formation. Three morphologically different types were identified: a) growth on mussels, b) spherical nodules (ca. 1-3 cm) and c) disshaped symetrical and asymetrical nodules (up to 10 cm). Average values from 110 accumulates representing the three types were: Mn 29.3%, Fe 10.0%, Co 77 ppm, Ni 97 ppm, Cu 21 ppm and Zn 340 ppm. Accumulates on mussels showed the highest trace metal concentrations. A growth rate of ca. 0.6 mm/yr for type (a) was estimated. Heavy metal concentrations were determined in ca. 60 sediment and 30 pore water samples, and in 110 Baltic sea water samples. During certain periods, large increases in Mn values (up to 400 (µg/l) were found in the deeper waters. These concentrations develop during periods of strong stagnant conditions in the sediments where dissolution of Mn oxides, and diffusion mobilizes the Mn into the overlying waters. The manganese is then reprecipitated close to the boundary of the O2-enriched surface waters. This critical O2-concentration was found to be 40% saturation. In the Kiel Bay, Mn-Fe-accumulates are found in a zone which marks the upper limit sometimes reached by the deep waters of lower O2-concentration. Additionally, the availability of larger particles (especially stones or mussels) on the sediment surface is necessary. These conditions are met in the Kiel Bay in a water depth of 20-28 m at several places.

Hydrocarbons in surface waters of the Atlantic and Indian Oceans

Results of investigation of various forms of oil pollution, i.e. oil films, tar, and hydrocarbons in the Northeast Atlantic Ocean and North Indian Ocean during October-December 1980 and February-May 1981 are presented. Oil pollution was found only in regions of the heaviest ship traffic and was somewhat less than in 1976-1977. Background concentration of non-polar hydrocarbons was 8-10 ?g/l in surface waters and 14 ?g/l in the shelf zone. Infrared spectroscopy and gas-liquid chromatography indicate that hydrocarbons occurring at concentrations exceeding 50 ?g/l have composition differing from background hydrocarbons. There is considerable accumulation of hydrocarbons in the thin surface layer, and they exist in different forms close to pollution sources.

Composition and biomass of phytoplankton in the Northwest Pacific in summer 1990

According to results of Cruise 22 of R/V Akademik Mstislav Keldysh in the Northwest Pacific in July-August 1990, picophytoplankton represented mainly by cyanobacteria (up to 90%) comprised from 70 to 99% of total phytoplankton. Nanophytoplankton constituted substantial part of total biomass (22-37%) and consisted mainly of small phytoflagellates (2-4 ?m), cryptomonades, and coccolithophorids Emiliania huxleyi. Summer species such as Neodenticula seminae prevailed among large phytoplankton. Horizontal and vertical distribution of phytoplankton groups and species was described. Taxonomy and vertical distribution were related to nutrient concentrations in the upper mixed layer.