Zależność koncentracji metali ciężkich i węgla organicznego w muszlach mięczaków środkowodnych: Lymnaea peregra (Müller, 1774), Lymnaea stagnalis (L.) i Dreissena polymorpha (Pallas, 1771) od ich wielkości

The shells of Lymnaea peregra and L.stagnalis were collected from a fishing pond in Kłemby near Nowogard (NW Poland), and those of Dreissena polymorpha came from the nearby Odra River estuary (Roztoka Odrzańska). The latter site had much higher concentrations of heavy metals, both in water and in bottom sediments. The study aimed at finding correlations between the concentrations of heavy metals and organic carbon and the shell size. In shells of freshwater snail Lymnaea peregra three second degree polynominal correlations were confirmed at the 0.05 significance level of between concentrations Co (positive), Corg. (negative) and Cd and height of shells. In the other three cases (Cu, Pb, Zn) there was no correlation significant at the 0.10 level. In shells of Lymnaea stagnalis three parameters shown significant (at the 0.05 level) correlation with shell size: concentrations of Zn (negative), Co (negative) and Corg. (positive). The other three (Cu, Pb, Cd) were insignificant even at the 0.10 level. In shells of a bivalve, zebra mussel Dreissena polymorpha, concentrations of four element shown significant (p=0.05) correlation with shell length: Pb (negative), Zn, As and Hg (all positive). Concentrations of Sr and Co were positively correlated and concentrations of Cd and Corg. Negatively correlated with shell size of this species at 0.10 significance level. Both in the case of snails and zebra mussels, no significant correlation was observed between their size and Cu concentrations. The results indicate that there the concentrations of heavy metals and Corg are indeed size-dependent, and the correlations differ among studied molluscs. Further research is necessary to establish standard procedures for measurements of these parameters for use in monitoring studies: whether the concentrations in shells of indicator species should be analysed in specimens of standard size or standard age to allow for comparisons of measurments taken in different sampling sites or habitats.