(Table 2) Rates of nitrate and ammonium uptake, concentrations of particulate organic nitrogen and carbon, and dissolved nitrate and ammonium in waters of the Black Sea August-September 1990 and November 1991

To study inorganic nitrogen uptake rates by microplankton in the Black Sea the first 15N-experiments were carried out in August-September 1990 and in November 1991. In surface waters nitrate uptake rates varied from 5.7 to 28.5 nM/l/h in summer and from 1.9 to 7.8 nM/l/h in autumn. In both seasons maximal and minimal rates were observed in frontal zones of shelf/slope areas and in open waters, respectively. In summer average nitrate uptake rate per unit of particulate organic nitrogen was 0.0037 1/h for all stations. In autumn it varied from 0.0007 1/h in the central part of the sea to 0.0033 1/h in the slope near the southeastern Crimean coast. In autumn ammonium uptake rate varied from 7.1 to 22.2 nM/l/h and from 0.0025 to 0.00094 1/h. Ammonium uptake correlated linearly with nitrate uptake, with new production being 22-36% of total summary nitrate and ammonium uptake. There was a linear correlation between nitrogen uptake and chlorophyll a concentrations in the Black Sea. In the water column in autumn both nitrate and ammonium uptake decreased as chlorophyll a concentration diminishes with depth.

Activity of ETS enzymes and phosphatase in the Sea of Okhotsk and Kuril region in summer 1992 and 1993

An estimate of rate of transformation of organic matter and regeneration of nutrients (in particular phosphorus) was calculated for different regions of the Sea of Okhotsk. The rate was estimated by means of rate of complete oxidation of organic matter to CO2 and H2O catalyzed by enzymes of the electron transport system (ETS) and rate of hydrolytic splitting of phosphate from organic phosphorus compounds catalyzed by alkaline phosphatase. Organic matter destruction rate was at its maximum on the shelf of Kamchatka and Sakhalin, as well as in the layer of maximum oxygen gradients in deep waters. It was found that zones of intensive primary production were characterized by high rates of phosphorus regeneration, which provided for 80% of primary production when concentration of mineral phosphorus was low.

K-Ar age and chemical composition of volcanites from the Sea of Okhotsk

Volcanogenic rocks from the Sea of Okhotsk are divided into seven age complexes: Late Jurassic, Early Cretaceous, Late Cretaceous, Eocene, Late Oligocene, Late Miocene, and Pliocene-Pleistocene. All these complexes are united into two groups - Late Mesozoic and Cenozoic. Each group reflects a certain stage of development of the Sea of Okhotsk region. Late Mesozoic volcanites build the geological basement of the Sea of Okhotsk, and their petrochemical features are similar to those of the volcanic rocks from the Okhotsk-Chukotka Volcanogen. Pliocene-Pleistocene volcanites reflect stages of tectono-magmatic activity; the latter destroyed the continental margin and produced riftogenic troughs. Geochemical features of volcanites from the Sea of Okhotsk indicate influence of the sialic crust on magma formation and testify formation of the Okhotsk Sea Basin on the destructive margin of the Asian continent.

Ostracodes in bottom sediments of the Laptev Sea

This work is the first detailed description of the Late Pleistocene-Holocene and Recent Ostracoda of the Laptev Sea. A total of 45 species in 22 genera and 13 families have been identified. All these species are described monographically. Three different ecological assemblages of ostracodes corresponding to different combinations of environmental parameters have been established; they are restricted to three regions of the sea: western-central, eastern, and southern. The recent ostracode assemblages of the Laptev Sea have been compared with those from other Arctic areas and are most similar to those of the Beaufort and Kara seas. Data on recent Ostracoda are used for paleoenvironmental reconstructions on the eastern shelf and western continental slope of the Laptev Sea. For this purpose, ostracodes from five sections obtained from these parts of the sea have been examined. The oldest sediments, which are of Late Pleistocene age (15.8 cal. ka BP), have been recovered in a core from the western continental slope. These yielded five ostracode assemblages, which correspond to different paleoenvironments and replaced each other in the course of the rapid postglacial sea-level rise, thus showing variations in the Atlantic water inflow from the west and freshwater discharge from the subaerially exposed shelf. On the outer shelf of the eastern part of the sea, the rapid sea-level rise in the Early Holocene (lowermost dating 11.3 cal. ka BP) led to a rapid transition from assemblages of brackish-water nearshore environments to those of modernlike normal marine environments; modern environments were established about 8.2 cal. ka ago. Since core sections from the inner shelf correspond to the time when the level of the sea had already reached its modern values, changes in taxonomic composition of ostracode assemblages primarily mirror variations in river runoff.

Vertical distribution of zooplankton biomass in the Sea of Japan

Vertical distribution of total zooplankton biomass and major taxonomic groups are investigated by layers to depths of 2500-3400 m on the basis of three series of net plankton collections. Zooplankton is most abundant above 1500-2000 m. Since true deep-water species do not occur in the Sea of Japan, biomass drops much more sharply at greater depths than it does in the ocean. Since few carnivores inhabit the deep layers, abundant remains of planktonic organisms fall to the bottom, and carnivorous detritovores feeding on these remains are dominant in deep water bottom fauna.

Abundance of diatoms and foraminifers in the surface sediment layer of the southeastern Laptev Sea shelf

The study of diatoms and benthic foraminifers from the southeastern shelf of the Laptev Sea shows that their most diverse and abundant recent assemblages populate the peripheral underwater part of the Lena River delta representing the marginal filter of the sea. This area is characterized by intense interaction between fresh waters of Siberian rivers and basin seawater, Atlantic one included. Local Late Holocene (~last 2300 years) environments reflect the main regional and global paleoclimatic changes, the Medieval Warm Period (~600-1100 years B.P.) and the Little Ice Age (~100-600 years B.P.) inclusive. In addition, composition and distribution of planktonic foraminifers implies strong influence of Atlantic water during the Holocene optimum ~5100-6200 years B.P.

Weather conditions and phosphorus speciation in waters of the Western Sargasso Sea in October-November 1977

Forms of phosphorus were determined for the first time in the area under study. Based on the ratio between organic and inorganic forms of phosphorus, it is concluded that sorption processes in the thin surface layer and photosynthetic processes in surface water are of the same intensity. Extremely high values of total phosphorus in the thin layer may be indicators of water pollution.

Data on mineral composition of volcanic glass and radiocarbon age of Upper Quaternary sediments from the Sea of Okhotsk

Lithological horizons have been distinguished in sediments cores from different parts of the Sea of Okhotsk based on primary descriptions of sediments and smear slides, and analyses of contents of both calcium carbonate and organic carbon, and opal. Sediment lithology has been correlated with oxygen isotope records and the standard isotope scale and radiocarbon data by AMS method for three cores studied in detail. This allowed to determine in detail periods of carbonaceous and diatomaceous ooze accumulation in the Sea of Okhotsk. Changes in magnetic susceptibility and grain size composition of sediments have been also compared with oxygen-isotope curves and radiocarbon datings. Obtained results confirm that variations in magnetic susceptibility are related with oxygen-isotope stages and influenced by climatic changes. Tephra interlayers K0, TR, K2, K3 have been identified by mineralogical analyses in all studied cores. Stratigraphic location of these tephra interlayers in detailed studied cores and their radiocarbon ages (8.1, 8.05, 26.8, and about 60 ka, respectively) provided base correlation between the interlayers and volcanic eruptions on the Kamchatka Peninsula and the Kuril Islands. This allows to use the former ones as time markers for deep-sea sediments of the Sea of Okhotsk. New lithostratigraphic and tephrochronologic data obtained allowed to correlate Upper Quaternary sediments from the Sea of Okhotsk.

(Table 1) Biomass of plankton in the Sea of Japan at Station VITYAZ6674

Vertical distribution of zooplankton biomass from the surface to bottom layers (3400 m) is examined. Material was collected layer by layer by a BR 113/140 net at 41°59' N and 133°37' E on July 2 and 3, 1970. Quantity of plankton below 1000 m was found to be much less than at corresponding depths in the adjacent regions of the ocean. This impoverishment is due to absence of oceanic bathypelagic animals in deep layers of the Sea of Japan. Absence of specialized predators (plankton-feeders) deep in the Sea of Japan results in underconsumption of interzonal animals that sink to great depths. Upon dying they should reach the floor in larger quantities than in the ocean.

Rates of organic matter transformation within the production-destruction cycle of the White Sea

Rates of organic matter (OM) transformation within the production-destruction cycle of the White Sea were estimated on the basis of measured activity values of redox enzymes of the electron transport system and of hydrolytic enzymes (phosphatase and protease). It was found that OM oxidation processes were the most intensive in the Kandalaksha Bay, while minimum oxidation rates were characteristic of central parts of the Dvina and Onega bays. It was revealed that the highest rates of phosphate mineralization were characteristic of the central part of the sea and near-mouth areas of the Onega and Kandalaksha bays, with the lowest rates in the Dvina Bay. During the period of intense primary production when resources of inorganic phosphorus were practically depleted, high rates of phosphate regeneration were observed. It was shown that populations of micro- and zooplankton in the White Sea were characterized by low activation energies of the principal metabolism reactions (3-6 kcal/mol), which allowed these populations to provide exchange intensity comparable to that of inhabitants of warm waters during all the seasons.

(Table 1) Some structural characteristics of communities and detritus flux through the lower boundary of a given water column in different regions of the Kara Sea

Vertical fluxes of autochtonous detritus at different levels were estimated using the algorithm of structure-function analysis. The calculations are based on pelagic ecosystem parameters in the Kara Sea observed in September 1993 (temperature, primary production, biomass of phytoplankton, bacteria, protozoa, and zooplankton, trophic and size composition, etc.). At eight stations in different parts of the sea where sedimentation traps were set, the range of calculated fluxes of autochtonous detritus through the lower boundary of the water column was 13-90 mgC/m**2/day. The flux was much higher in the estuary of the Yenisey River (55-90 mgC/m**2/day) than in the northeastern regions (I8-50 mgC/m**2/day) and, especially, in the relatively deep southwestern part of the sea (13-35 mgC/m**2/day). The calculated fluxes of autochtonous detritus in shallow water regions (where conditions are variable and poorly known hydrologically and where outflow of allochtonous detritus is substantial) cannot be compared to data from sedimentation traps.