Role of Lipids in the fate of organochlorine compounds in Aquatic Ecosystems

Abstract: Both results of laboratory experiments and material collected in the field have shown the lipid composition in organisms to have a significant effect on the bioaccumulation of pollutants and on the lipid steady-state concentrations of pollutants there. The redistribution of persistent organic pollutants which occurs in organisms as a consequence of the depletion of lipid depot, was studied in a population of migrating Pacific salmon (Oncorhynchus nerka). Concominant with an increase in lipid pollutant concentration during their river ascent, pollutants were shown to be redistributed from the muscle tissue to the lipid-rich gonads of the salmon Furthermore, the lipids were found to act as compartments for pollutant transportation, the salmon bringing pollutants to their spawning lake. Such 2biotransport2 can significantly influenced the pollutant levels in the biota of the spawning lake. This highlighted one route for pollutant transfer between ecosystems. In the assessment of lipid-pollutant interactions, the analytical methods employed are of great importance. Efficiency in extracting both total lipids and organic pollutants of varying lipophilicity from the fish muscle was shown to be related to the lipid composition of the sample in question. This reduces the comparability of results obtained by different extraction methods and from different species. A further ecotoxicological aspect of lipids that was discussed concerns altered lipids containing organic pollutants, specifically chlorinated fatty acids. These cause toxic effects and diverge from other anthropogenic organic pollutants in that responses of the organism aimed at excretion of them appeare not to occure. Such chlorinated fatty acids are incorporated into complex lipids within the organism and may be transferred then within the food-chain. They are suggested as being 2biologically stable2 pollutants. Based on the results presented in this thesis I conclude that lipids have a strong influence on the distribution of lipophilic organic pollutants at every level of organisation in an ecosystem and that they should be of major concern in analytical work and in data evaluation within ecotoxicology.