Ecosystem responses to heavy metal pollution: analysis of foodchain transfer and effects on structure and functioning in herbivore-plant-detrivore communities in contaminated terrestrial sediments in the Biesbosch.

The sediment of the Rhine Meuse delta (Biesbosch) is strongly polluted with heavy metals. Heavy metals accumulated in below-ground or aerial parts of plants may be taken up by leaf of root herbivores or by detritivores. Due to exposure to heavy metal pollution, the community structure or composition may change, which in turn is altering ecosystem processes. Possible effects of heavy metals on the community might arise directly from contamination of the basal resources or soil solution or indirectly due to a decrease in the amount of resources. We therefore aim at determining food-chain transfer of heavy metals and the effects of heavy metals in the above and below-ground parts of two terrestrial food chains in tidal sediments the Biesbosch area, one dominated by Phragmites australis, the other by Urtica dioica and Glechoma hederacea. These activities will be performed in two closely related subprojects. In these projects, the following activities will be carried out: I. Field inventory of food chain structure in a number of polluted and non-polluted reed flats in the Rhine Meuse delta. This inventory will include a time series, to measure/quantify primary productivity (above and below-ground), detritus production, and biotic decomposition and functioning. In addition, heavy metal levels will be measured in all components of the two food chains under study. I. Mesocosm studies to further investigate mechanisms of food-chain transfer of heavy metals in the two food chains. In these mescocosm studies, effects of inundation frequency and degree of pollution on the food-chain transfer of heavy metals and the structure and functioning of both food chains will be quantified. I. Additional laboratory studies to investigate the relative importance of different routes of exposure (soil, detritus) for detritivores. An important aim of these mesocosm and field studies is also to determine to what extent effects of heavy metal pollution on the structure and/or functioning of the below-ground community may affect the structure and/or functioning of the above-ground community and vise versa.