Dissolved oxygen, nitrate, nitrite, and ammonum in waters of the Arabian Sea

Distribution of ammonium, nitrite and nitrate nitrogen is examined in a section along 65-67°E between 18°S and 23°N during the transition period from winter to summer monsoons. It is shown that, under conditions of very large oxygen deficit in the 200-400 m layer, denitrification process results in formation of the second deep-sea maximum of nitrites and the intermediate minimum of nitrate nitrogen.

Abundance and biomass of benthic foraminifera in bottom sediments from the Sea of Okhotsk and the Pacific Ocean

A study of distribution of live individuals of benthic foraminifera in sediments of the Sea of Okhotsk and of the Northwestern Basin of the Pacific Ocean shows that they can be present in sediments up to depth of 30 cm and probably can live there for long periods, sometimes forming high concentrations. Living individuals in the subsurface layer often account for more than 50% of total biomass, which varies from 1 to 21 g/m**2 in different morphological structures. The largest biomass values are attained in underwater rises embedded in relatively warm, oxygen-saturated Pacific waters. Minimum total biomass concentrations occur in deep-water depressions where stagnation phenomena are observed. Foraminifera biomass everywhere decreases gradually with increasing depth from the surface of sediments regardless of relief, depth, and nature of sediments.

(Table 2) Chemical composition of skeletons of scleractinian non-zooxanthelate corals

The first data on chemical composition of nonreef-building non-zooxanthellate deep-sea corals presented in this publication allow us to identify following tendencies manifested in the biomineralization process. Comparison of concentration levels of some chemical elements in scleractinian corals and ambient ocean waters suggests that corals do not accumulate K in the process of biomineralization and weakly accumulate Mg, whereas Ca, Sr, Si, Al, Ti, Mn, Zn, Cu, Cd, Pb, and Fe are concentrated in skeletons of corals with enrichment coefficients of 10**3 to 10**7. Correlations between components contained in the skeletons of scleractinian corals suggest that the source of Al, Si, Fe, and Ti in them is the clayey constituent of bottom sediments and zooplankton, while trace elements are likely accumulated via bioassimilation from seawater. Such elements as Mn, Sr, Pb, and Cd can structurally substitute Ca in calcite and aragonite. Variations in concentrations of the elements in coral skeletons depending on their habitat depths are fairly significant. As could be expected Ca and Mg concentrations are prone to decrease with depth (R = -0.55 and -0.51, respectively), which can possibly be caused by partial dissolution of carbonate skeletons with increasing depth, whereas the Sr/Ca ratio does not depend on depth.

Structural group composition of low-polarity organic matter dissolved in waters of the Northwest Indian Ocean and the Red Sea

Data on amounts of various functional groups, i.e. aldehyde, acid, ester, alcohol, thiol and aromatic groups in several fractions of low-polarity dissolved organic matter are presented. An assumption that this organic matter is part of the lipid fraction is not confirmed. Amount of aromatic compounds in waters of the Northwest Indian Ocean is estimated to be about 1000 times higher than quantity of aromatic hydrocarbons discharged into the ocean each year in petroleum and petroleum products.

Composition of recent carbonate bottom sediments from the Guiana shelf an off the West Africa

This work was based on a study of the upper layer of recent carbonate bottom sediments of the Atlantic Ocean. Biogenic carbonate of recent sediments is represented by metastable and stable minerals. In the ocean metastable phases can exist indefinitely long, but the structure of polymorphism determines inevitability of transformation of metastable phases into stable ones. This transformation occurs in the solid phase. In the absence of a critical point between the two phases of the transition process is not available for study by microscopic methods. It is estimated indirectly by studying the nature and extent of changes in mineral and chemical compositions. With aging of sediments their mineral composition alters in direction of increasing contents of resistant minerals. Fine grained sediments and fractions are subject to more intensive effects of early diagenesis processes, rather than coarse ones; this is reflected in their mineral composition. Regularities of distribution of carbonate minerals in size fractions consistent with the direction of polymorphic transformations in calcium carbonate. Such transformations can occur in a particular dimension of grains. Concrete grain size depends on environmental conditions. This situation explains presence of metastable biogenic carbonates at different depths of the ocean and suggests presence of diagenetic calcite in sediments occurring below expected for each case depth of the transition.

Lipids in ocean particulate matter and bottom sediments

Lipid contents both in particulate matter and bottom sediments decreases with passage from the shelf toward the open ocean. Lipid concentration in particulate matter collected by a separator (Ls) decreases by a factor of 7 (from 7.05 to 0.95 % of dry matter), while in particulate matter collected on filters (Lf) it decreases by a factor of 13 (from 78 to 6 µg/l) in the vicinity of the Limpopo River and by a factor of 6 (from 74 to 13 µg/l) in the vicinity of the Zambezi River. Concentration of Lf also decreased with depth. In the upper sediment layers lipid concentration was 0.0028-0.039% of dry matter; all mud samples were richer in lipids, than sand samples. During sedimentogenesis there is an increase in proportion of lipids relative to other classes of organic matter, proportion of low-polarity compounds increases among the lipids, and proportion of hydrocarbons rises among these compounds. Sediments inherit composition of particulate matter to the greatest degree in the vicinity of river mouths.