Abstract

This report summarises research carried out within the project 'functional biodiversity' on the relationship between toxicants, biodiversity and functioning of ecosystems. Chronic stress from persistent compounds may lead to community shifts: sensitive species become tolerant or are replaced by less-sensitive species. This does not necessarily lead to a significant loss of vital ecosystems. Chronic stress from persistent compounds may lead to community shifts: sensitive species become tolerant to a significant loss of vital ecosystem functions or overall biodiversity but may result in slow genetic erosion of communities: i.e. species composition changes. Multiple regression analysis of a large monitoring data set on abundance of species showed the shift in nematode species composition, predicted by a simple food chain model, to occur in metal-contaminated experimental fields. Additional regression analysis of monitoring data on nematodes and aquatic species has made plausible the notions: 1) that toxic stress is a relevant factor in the occurrence and abundance of species; and 2) that toxic stress on species can be expressed and analysed together with 'classic' habitat factors such as pH, nutrient levels and desiccation.