Metal accumulation, speciation and toxicity relationships in freshwater fish: An experimental and field analysis

The current thesis situated itself within the framework of metal ecotoxicological studies and focused on the following research questions: (1) the importance of different exposure routes to the overall metal accumulation in fish, (2) the role of metallothionein (MT) in cytosolic metal speciation, and homeostasis and metal detoxification processes, (3) the relation between disturbances in cytosolic metal speciation and harmful effects of metal exposure.;In a first set of experiments the relative contribution of dietborne Cd and Zn (midge larvae) accumulation was studied in common carp. The results of the laboratory experiments clearly demonstrated that although metal uptake from water appeared to be less efficient than dietborne metal uptake, its contribution to the whole body metal accumulation was higher than the metal uptake from food. Moreover, they also demonstrated the major importance of metal assimilation efficiencies (AE) in dietborne Cd and Zn accumulation.;It has been demonstrated that the metal-binding protein metallothionein (MT) plays a dominating role in the subcellular metal compartmentalization and accumulation. Therefore the applicability of MT as biomarker for metal exposure was studied in combination with its role in the subcellular processes which control metal homeostasis and detoxification. MT has been shown to play a dominating role in the subcellular homeostasis of the essential metals Cu and Zn, and the detoxification of the non-essential metal Cd and this under laboratory conditions as well as in field studies. At the highest contaminated sampling sites however, a complete metal detoxification could not be guaranteed although the MT pool dominated the cytosolic metal speciation and a clear MT induction was measured. This resulted in important disturbances of the cytosolic distribution of the essential metals Cu and Zn and some physiological parameters in the sampled fish. (Abstract shortened by UMI.).