Linking pollution-induced community tolerance (PICT) and community shifts induced by chronic exposure to metal contamination for microbial and nematode communities.

Due to human activities, the environment is increasingly exposed to chemicals at concentrations which are not naturally present. Consequently, organisms in ecosystems that are in close contact with the environment have to cope with increased levels of these chemicals. After a long exposure history it is to be expected that communities show adaptation mechanisms, for instance by shifts towards a composition which is able to effectively cope with increased contamination levels. Besides pollutants, environmental factors effect community structure also. Nowadays, environmental policy is directing towards site-specific approaches, in contrast to general risk assessment used for deriving environmental quality criteria. In this approach the assessment of hazardous field effects is the focus rather than the levels of contamination. Consequently, site-specific ecological information with respect to the contaminated area is the target. Therefore, it is extremely important to determine a causal relationship between the presence of a pollutant and an ecological effect in the field. The solution for this is to measure the pollution-induced community tolerance (PICT; see below) because there is a causal relationship between the presence of pollutants and the ecological effect. The aim of the project described in this proposal is to link PICT with methods for determining ecological effects on the level of community structure and ecosystem functioning in terrestrial systems. The target communities represent different trophic levels, i.e. bacteria and nematodes, in order to increase ecological relevancy. The target contamination type will be (mixtures of) heavy metals. The figure presents an overview of the objectives of the research programme with respect to the community shifts. So, PICT for metals (metal-contaminated sites are available in SSEO areas) will be established with microbial and nematode communities. Furthermore structural and functional Figure 1: Overview of the objectives of the programme community changes will be analyzed. The re- search strategy involves both the analysis of communities in field samples and monitoring effects in model terrestrial ecosystems (MTE). The integrated analysis will highlight the applicability and meaning of PICT with respect to ecosystem structure and functioning. Further- more, the relationship between ecosystem structure and ecosystem functioning will be studied, additionally. The analysis of com- munities at different trophic levels will broaden our view on the effects of toxic stress on eco- systems. Furthermore, this type of combinatory- information supplemented with data about eco- system functioning can be used in ecological and food web modeling.