Mussels as bioindicators of trace metal pollution in the Danube Delta of Romania

Specimens of mussels species Anodonta anatina, Unio pictorum, U. tumidus an d surfical sediment samples were collected in the summers of 1994 and 1995 from twelve lakes in the Danube Delta, Romania. Whole mussel tissues were a nalyzed for metals (Ag, As, Cd, Co, Cu, Cr, Ni, Pb, Se and Zn), and sedimen t samples were subjected to weak acid extraction and to a sequential extrac tion procedure, and analyzed for Cr, Cu, Ni and Zn. Total mean Cu and Ag co ncentrations were statistically greater in Unio species than in Anodonta sp ecies, but other metal levels did not significantly differ between mussel s pecies. There was a ten fold variation for Cd and Pb and five fold variatio n for Zn, Ag and Co concentrations in mussels among lakes. Mean concentrati ons of As, Cu, Se and Zn in mussel tissues varied two fold among lakes. Zn, Co and Cd concentrations in mussels were significantly negatively correlat ed with distance gradients from the origin of the Delta and with distance f rom main channels of the Danube. Other metal concentrations in mussels did not correlate with either distance gradient. Trace metal levels in mussel t issues were correlated with those in weak acid and in sequential extraction s of sediment. Zn concentrations in the carbonate fraction was the best pre dictor of Zn concentrations in mussels. Cu and Ni levels in the organic mat ter and sulfide fraction were the best estimators of Cu and Ni concentratio ns in mussels.