LEVELS OF HEAVY-METALS IN BIOTA FROM THE LA-PLATA RIVER

In this study levels of five heavy metals-Cd, Cu, Ni, Pb, and Zn-were quantified in selected tissues of aquatic organisms and in sediments from the La Plata River. Fishes (Odontesthes bonariensis and Pimelodus clarias), snails (Ampullaria insularum), and bivalve molluscs (Neocorbicula limosa) were collected from a Recreational Fishing Association, nearby Buenos Aires harbor, during 1988 and 1989. Samples of snail hepatopancreas showed higher levels of metal concentrations than samples of fish livers, regarding the five metals quantified. In general, lower levels of heavy metals were observed in whole body samples of bivalves, with or without the gut contents, except for Cd. Both species of macroinvertebrates have demonstrated a great ability to bioaccumulate Cd. Many physical, chemical, and biological factors regulate the intake and accumulation of heavy metals by aquatic organisms. Therefore, it is difficult to assess the extent of pollution in biota from the La Plata River by direct comparisons with data previously reported in the literature. However, our results may be useful as reference levels of heavy metal contamination in selected organisms from this particular aquatic system. (C) 1993 John Wiley & Sons, Inc.