Bioaccumulation of some trace elements in the biota of the hydrothermal fields of the Guaymas Basin (Gulf of California)

Abstract

Data from the hydrothermally influenced Guaymas Basin of the Gulf of California are presented on the concentration and distribution of Ag, As, Au, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Pb, Sb, Se, and Zn in different tissues of dominant hydrothermal vent animals such as vestimentifera Riftia pachyptila and vesicomyid clams Archivesica gigas and other organisms, including Spongia, bivalve mollusks Nuculana grasslei, Phelliactis pabista, and crab Munidopsis alvisca. Chemical element content was measured by atomic absorption spectrometry (flame and graphite furnace methods) and instrumental neutron activation analysis. In the dominant specialized taxa, the main target organs of metals were the trophosome and obturaculae of Riftia pachyptila, the gills and mantle of Archivesica gigas. The other organisms also demonstrated high bioaccumulation of metals. Especially high levels of most of the metals (excluding Mn) were detected in the soft body of Nuculana grasslei. The highest Mn content was found in the whole body of Spongia. Bioconcentration factor of the trace metals studied varies within three orders of magnitude from 5 (Mn) to 3•104 (Cd). This testifies apparently a selectivity of trace metal bioaccumulation by the organisms which is determined by metal bioavailability independently of metal concentration in the water column. Variability in the molar ratio Fe/Mn allows us to assume that these metals undergo fractionation during migration from the hydrothermal fluids to the interior organs of animals. Insignificant differences between the Cd, Cu, Fe, Hg, Pb, and Zn levels in the Guaymas Basin vent clams versus that in the bivalve mollusks from polluted areas of the Gulf of California might suggest that the metal bioavailability play an important role in the bioaccumulation.