The use of marine bivalves in heavy metal monitoring near Vladivostok, Russia

The industrial and domestic wastes of Vladivostok, the biggest city in the Russian Far East, have led to the increasing pollution of neighbouring coastal waters by heavy metals (Zn, Cu, Pb and Cd). The seasonal and spatial variability of Zn, Cu, Pb and Cd concentrations in the common molluscs Mizuchopecten yessoensis, Crenomytilus grayanus and Modiolus kurilensis around Vladivostok were studied. There are large seasonal changes in the metal contents of the molluscs resulting from variations of filtration rate (for Zn and Cd) and differences in physiological state (for Cu and Pb). For Modiolus kurilensis the change in tissue weight during the reproductive cycle is also significant. Simultaneous sampling during the summer showed that agreement between pollution levels in sediments and in all molluscs was observed for Cu only. The Pb and Cd concentrations in molluscs reached maximum values in the outer zones of the polluted region, but Pb and Cd contents in the molluscs decreased in the harbour localities where sediment metal loads indicated heavy pollution. It is supposed that in such localities with high inputs of metals and organic substances, the molluscs may filter smaller volumes of the contaminated water and thus accumulate smaller quantities of metals.