The distributions of Fe, Mn, Zn, Cu, Ni, Co, Cr, Pb, As, Ag, Cd, Se, Sb, and Hg in 128 samples of tissues of the organisms that inhabit hydrothermal vent fields of the Mid-Atlantic Ridge (Menez Gwen, Snake Pit, and Rainbow) depending on the abiotic environmental parameters were studied. The majority of the elements studied showed direct correlations between their concentrations in the fluids released and in the tissues of hydrothermal organisms. A higher degree of bioaccumulation of metals was revealed in the Bathymodiolus mussels and Rimicaris shrimps from the Rainbow hydrothermal vent field as compared to their analogues from Menez Gwen and Snake Pit. This corresponds to the maximum concentrations of the majority of the metals studied in the Rainbow high-temperature hydrothermal fluids. The highest degree of bioaccumulation of heavy metals was found in gills of the symbiotrophic mussels Bathymodiolus and in maxillipeds of the ectosymbiotic shrimps Rimicaris, i.e., in the organs that function in dependence on chemosynthetic bacteria. Within the Rainbow vent field, the shrimps, which inhabit in biotopes with more high-temperature conditions and therefore are more strongly subjected to the influence of fluids, were found to contain higher metal contents than mollusks. The Fe-Mn hydroxide films that cover mussel shells might serve as important reservoirs of other metals related to Fe and Mn.

The biogeochemical behavior of the group of heavy metals and metalloids in the water (including their dissolved and suspended particulate forms), bottom sediments, and zoobenthos was studied in the Ob River estuary-Kara Sea section on the basis of the data obtained during cruise 54 of the R/V Akademik Mstislav Keldysh in September–October 2007. The changes in the ratios of the dissolved and suspended particulate forms of Fe, Mn, Zn, Cu, Pb, Cd, and As were shown, as well as the growth of the fraction of adsorbed forms in the near-bottom suspended particulate matter under the mixing of the riverine and marine waters. The features of the metals’ accumulation in the typical benthic organisms of the Ob River estuary and the Kara Sea were revealed, and their concentrating factors were calculated based on the specific conditions of the environment. It was shown that the shells of the bivalves possessing a higher biomass compared to the other groups of organisms in the Ob River estuary play an important role in the deposition of heavy metals. The mollusks of the Ob River estuary accumulate Cd and Pb at the background level, whereas the Cu and Zn contents appear to be over the background level.

The bioaccumulation of trace metals in the carbonate shells of mussel and clams was investigated at seven hydrothermal vent fields of the Mid-Atlantic Ridge (Menez Gwen, Snake Pit, Rainbow, and Broken Spur) and the Eastern Pacific (9°N and 21°N at the East Pacific Rise and the southern trough of Guaymas Basin). Mineralogical analysis showed that the carbonate skeletons of the mytilid mussel Bathymodiolus sp. and the vesicomyid clam Calyptogena m. are composed mainly of calcite and aragonite, respectively. The first data were obtained for the content of a variety of elements in the bivalve carbonate shells from various hydrothermal vent sites. The analysis of the chemical compositions (including Fe, Mn, Zn, Cu, Cd, Pb, Ag, Ni, Cr, Co, As, Se, Sb, and Hg) of 35 shell samples and 14 water samples from the mollusk biotopes revealed the influences of environmental conditions and some biological parameters on the bioaccumulation of metals. Bivalve shells from hydrothermal fields with black smokers are enriched in Fe and Mn by a factor of 20–30 relative to the same species from the Menez Gwen low-temperature vent site. It was shown that the essential elements Fe, Mn, Ni, and Cu were more actively accumulated during the early ontogeny of the shells. The high concentration factors of most metals (n × 10²−n × 10⁴) indicate an efficient accumulation function of bivalve carbonate shells. Passive metal accumulation owing to adsorption on the shell surface was estimated to be no higher than 50% of the total amount, varying from 14% for Fe to 46% for Mn.

Specific features of the concentration of a group of chemical elements in the dominant bottom organisms are analyzed. The studied organisms inhabit geochemically different hydrothermal fields: Menez-Gwen, Broken-Spur, and Rainbow on the Mid Atlantic Ridge (MAR), as well as 9°50′N and Guyamas on the East Pacific Rise (EPR). It was revealed for the first time that bottom organisms accumulate 10² to 10⁵ times less the macro-ions of marine water Na and K from the water of biotopes than heavy metals. The intensive concentration of chemical elements, especially of heavy metals, and the high biomasses of bottom organisms associated with hydrothermal vents suggest that this fauna serves as a powerful deepwater biofilter. The absence of pronounced differences between values of coefficients of accumulation for the same metals in the benthos of various MAR and EPR fields evidences the uniformity of the concentration function of the hydrothermal fauna.

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