ECOLOGICAL STANDARDS FOR EUTROPHICATION AND DESICCATION - PERSPECTIVES FOR A RISK ASSESSMENT

This paper describes an assessment of ecological standards for eutroph ication and desiccation using the ecotoxicological approach of standar d setting. In ecotoxicological risk assessment single-species toxicity data, such as No Observed Effect Concentration (NOEC), are used to ex trapolate maximum tolerable concentrations (MTC) which protect 95% of the ecosystem's species. In our approach single-species data consist o f the species-response function for both nutrient availability and soi l moisture. These data were used to calculate the maximum levels at wh ich 95% of the plant species are protected. A case study, using data o n 275 plant species of usable grasslands in the province of South Holl and, has been carried out. Ecological standards are calculated for max imum nitrogen load and changes in groundwater level. The influence of nitrogen limitation and moisture shortage on the 95% species protectio n level is considered. Differences in methodology between our approach and the assessment of ecological standards for micro-pollutants and c ritical loads are evaluated.