Seasonal Fluctuation of Organochlorines in Mytilus Edulis L. from the South West Baltic Sea

Seasonal and spatial variations in organochlorine concentrations in mussels Mytilus Edulis from the Baltic Sea were assessed The mussels from highly contaminated harbour areas showed a strong short term fluctuation in comparison to mussels from less contaminated beach areas. In all observed stations, PCB concentrations increased during autumn and decreased during early and late summer. Their change correlated positively with their lipid content. The reduction of the residue level during summer could be related with spawning activity. During winter the change in PCB concentration in observed stations were not uniform. The strongly elevated accumulation during winter, which was found at most harbour stations, may be caused by diminished Filtration activity due to increased stress. The pattern of seasonal change expressed on a dry weight and lipid weight basis was different. The change of PCB concentration on a lipid basis resulted from a dilution effect during seasonal lipid accumulation and a concentration effect during utilisation and release of body lipids. On a lipid weight basis therefore the actual exchange of organochlorines in mussel tissue can not be observed.