Concentrations of phosphates and silicon in near-bottom and interstitial waters of the Baltic Sea

Fine structure of vertical distributions of phosphorus and silicon in near-bottom layers and interstitial waters is studied in different regions of the Baltic Sea (Gulf of Finland, Bornholm area, Gotland trench). Data obtained are used to calculate fluxes of mineral forms of phosphorus and silicon in exchange processes between sediments and the near-bottom water layer. Depending on sediment types, values of nutrient fluxes vary from 9.8 to 632.6 µg-at/m**2/day for phosphorus and from 232.4 to 1881.1 µg-at/m**2/day for silicon. Fluxes calculated for different regions are compared.

Abundance and biomass of planktonic diatom Proboscia alata and associated species, chlorophyll a, organic carbon and nitrogen concentrations in waters over the Bering Sea middle shelf in August 2001

During most of the vegetation season from late May to early September large-sized diatom alga Proboscia alata forms local patches with high abundances and biomasses in different oceanographic domains of the eastern Bering Sea shelf. For 0-25 m layer average abundance and biomass of species in these patches are 700000 cells/l and 5 g/m**3 (wet weight), while corresponding estimates for the layer of maximal species concentrations are 40000000 cells/l and 38 g/m**3 (wet weight) or 1.6 g C/m**3. These levels of abundance and biomass are typical for the spring diatom bloom in the region. Outbursts of P. alata mass development are important for the carbon cycle in the pelagic zone of the shelf area in the summer season. The paradox of P. alata summertime blooms over the middle shelf lies in their occurrences against the background of the sharp seasonal pycnocline and deficiency in nutrients in the upper mixed layer. Duration of the outbursts in P. alata development is about two weeks and size of patches with high abundances can be as large as 200 km across. Degradation of the P. alata summertime outbursts may occur during 4-5 days. Rapid sinking of cells through the seasonal pycnocline results in intense transport of organic matter to bottom sediments. One of possible factors responsible for rapid degradation of the blooms is affect on the population by ectoparasitic flagellates. At terminal stages of the P. alata blooms percentage of infected cells can reach 70-99%.

Migration forms of hydrocarbons in waters and bottom sediments of the Gulf of Riga

It is found that hydrocarbons are constantly accumulated on the main geochemical barriers: water-atmosphere, river-sea, water-suspended matter, and water-bottom sediment interfaces. Degree of hydrocarbon accumulation reaches 13.5-17.6 in the surface microlayer and exceeds 1000 in bottom sediments. Hydrocarbon composition changes in this process. Local pollutant loads result in accumulation of polycyclic aromatic hydrocarbons by bottom sediments and benzo(a)pyrene concentration sometimes exceeds MPC. Content of hydrocarbon migratory forms is calculated.

(Table 1) Reduced compounds of sulfur in waters of the Baltic Sea

Concentrations of sulfide, S°, and thiosulfate were determined in waters of the Baltic Sea. Microquantities of these compounds were observed in oxic waters. Concentration levels of reduced sulfur compounds in Baltic oxic waters were very close to levels of the Black Sea oxic zone. Thiosulfate and S° were predominate compounds in oxic water whereas sulfide was a predominant compound of Baltic waters high in hydrogen sulfide. Conclusion was made that during sedimentation in oxic waters anaerobic microorganisms along with aerobic bacteria take part in mineralization of organic matter. They exist on surfaces and in microniches of particles of organic detritus.