EVALUATION XENOBIOTIC EFFECTS BY ECOLOGICAL TECHNIQUES

To prevent deleterious environmental effects of chemicals to be releas ed into the market and thus into the environment, the (eco)-toxic pote ntials (hazard assessments) have to be evaluated by ecotoxicological s tandard tests. These mono-species standard tests include species from several trophic levels, such as bacteria, algae, herbivores, and carni vores. Due to insensitive and ecologically vague toxicity endpoints (e .g., death, immobilisation of Duphnia) and limitations of mono-species tests, this evaluation procedure, however, is not able to identify an d assess potentially harmful effects of real environmental exposures; e.g., in the presence of geochemical matrices, long term exposure, low concentration exposure, exposure to super-lipophilic organic chemical s, or multiple chemical exposure. The solution may be the application of more ecologically oriented tests as well as ecological toxicity end points. The identification of adverse effects should include evaluatio n of a combination of both ecosystem structure and ecosystem functioni ng. To evaluate ecosystem structure and to assess its integrity, class ical taxonomic procedures as well as new time and labor saving ataxono mic procedures, especially for microbial biocenoses, can be applied. A nother approach to assess ecosystem integrity is the application of fu nctional parameters, such as biomarkers. Biomarkers are molecular biol ogical or biochemical responses of organisms or populations to any kin d of stressors. One class of stressors may be persistent chemicals. Th ese approaches to evaluation of xenobiotic effects will be illustrated by recent studies in accord with recent ecosystem theories.