Annual cycles of apoptosis, DNA strand breaks, heat shock proteins, and metallothionen isoforms in dab (Limanda limanda): influences of natural factors and consequences for biological effect monitoring

The present study was undertaken to investigate the influence of natural an d anthropogenic stressors on the induction of apoptosis, metallothionein (M T) isoforms, heat shock proteins and DNA strand breaks in the marine flatfi sh dab (Limbanda limanda) Seasonal changes and possible physiological influ ences were evaluated over a 1-year period at a fixed location northwest of Helgoland in the German Bight. These results were compared with data from s ampling sites in the North Sea and the Baltic Sea. Annual cycles could be o bserved for all parameters except for Cd. The data revealed that changes in biomarker are not only linked to physiological processes related to reprod uction but also to factors like water temperature changes, lipid content an d zinc content. Cd and organochlorines had no influence on biomarkers where as an influence of Cd on MT levels revealed in the regional observations wa s possibly masked by the major changes in Zn content during the annual cycl e. Due to different abiotic factors we supposed that the annual cycles at e ach sampling site in the North and the Baltic Sea might be shifted temporal ly and therefore measurements at different locations during a small time wi ndow of a few weeks may lead to misinterpretation in biomarker research.