Total and methyl-mercury content in bivalves, Mytilus galloprovincialis Lamarck and Ostrea edulis Linnaeus: relationship of biochemical composition and body size.

Abstract

Mussels and oysters are of interest to pollution ecologists because they are widely distributed, suspension feeding invertebrates and are likely to accumulate pollutants from their environment (Goldberg 1975). Many authors have estimated the relation between the concentration of metals in the flesh and various biotic and abiotic parameters. Body mass (estimated in dry weight) is evidently an important factor governing the uptake of metals by these organisms (Boyden 1974, 1977). Cossa et al. (1980) showed, furthermore, that the highest concentrations of certain metals were often found in the smallest individuals. The relation between metal content and body size can best be described using Boyden's model (Walne 1972; Boyden 1974) which is useful for quantifying any physiological activities in relation to the dry weight of the specimens. The regression coefficient b in Boyden's model is a measure of an organism's control over metal accumulation in its tissues. In practice, widely different values can be obtained for regression coefficient b when investigating the same metal. Cossa et al. (1979) suggested that this variability is primarily correlated with differing amount of gonad development. Gonad growth and maturation are accompanied by numerous biochemical changes in the flesh, especially in relation to glycogen content. Moreover, rapid changes in both wet and dry weights occur during the spawning period (Zandee et al. 1980). These changes are more profound in the largest individuals. Fortunately, the reproductive cycle of the mussel Mytilus galloprovincialis Lam. and Ostrea edulis L. have been thoroughly studied in Limski kanal by Hrs-Brenko (1971). In the present paper we describe our investigation into the relationship between total and methyl-mercury content and body mass in mussels and oysters collected in Send reprint requests to M. Najdek at the above address