Quantification of the role of organisms in the geochemical migration of trace metals in the ocean

Abstract

The contribution of biological processes to the geochemical migration of trace metals (Fe, Mn, Ni, Co, Cu, Zn, Cd, Pb, and As) was quantified for three geochemically distinctive areas of the ocean: continent—ocean boundary (marginal filter), euphotic zone of the open ocean, and deep-sea hydrothermal vent fields of the Mid-Atlantic Ridge. A new term “trace metal bioaccumulation potential” is introduced to compare the bioaccumulation intensity of different organisms. The bioaccumulation potential accounts for the ability of living matter to produce biomass. The bioaccumulation potential is calculated on the basis of mean whole-body concentrations of trace metals in the dominant communities and the biomass per unit area of the biotope. The results showed that the highest bioaccumulation potential is recorded in chemosynthesis-based benthic biota from deep-sea hydrothermal vent fields. At the same time, Fe, an essential heavy metal controlling a number of biochemical processes in organisms, was found to have the highest bioaccumulation potential, while Hg, a toxic heavy metal, has the lowest bioaccumulation potential. The bioaccumulation potential in the marginal filter and euphotic zone decreases in the following order Fe > Zn > Mn > Cu, whereas in deep-sea hydrothermal fields, the bioaccumulation potential of Mn is considerably lower, close to those of Pb, Co, Cr, and Cd. The order of trace metals bioaccumulation potential in biota is broadly similar in all three geochemically different regions. This implies that the bioaccumulation function of the biota is characterized by a geochemical resemblance in different parts of the ocean.