Evaluation of xenobiotic effects by ecological techniques.

To prevent deleterious environmental effects of chemicals to be released into the market and thus into the environment, the (eco)-toxic potentials (hazard assessments) have to be evaluated by ecotoxicological standard tests. These mono-species standard tests include species from several trophic levels, such as bacteria, algae, herbivores, and carnivores. Due to insensitive and ecologically vague toxicity endpoints (e.g., death, immobilisation of Daphnia) and limitations of mono-species tests, this evaluation procedure, however, is not able to identify and 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 chemicals, or multiple chemical exposure. The solution may be the application of more ecologically oriented tests as well as ecological toxicity endpoints. The identification of adverse effects should include evaluation of a combination of both ecosystem structure and ecosystem functioning. To evaluate ecosystem structure and to assess its integrity, classical taxonomic procedures as well as new time and labor saving ataxonomic procedures, especially for microbial biocenoses, can be applied. Another approach to assess ecosystem integrity is the application of functional parameters, such as biomarkers. Biomarkers are molecular biological or biochemical responses of organisms or populations to any kind of stressors. One class of stressors may be persistent chemicals. These approaches to evaluation of xenobiotic effects will be illustrated by recent studies in accord with recent ecosystem theories