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(P614) Combining single-species bioavailability models to predict the toxic effects of copper to multi-species systems .
De Schamphelaere, Karel*,1, Janssen, Colin, 1 Laboratory of Environmental Toxicology and Aquatic Ecology, Gent, Belgium
ABSTRACT- In earlier studies, we have developed and validated bioavailability models predicting chronic copper toxicity to the cladoceran Daphnia magna and the green alga Pseudokirchneriella subcapitata in standard single-species toxicity tests. The major focus of this poster will be on how these bioavailability models can be integrated into ecological models describing the interactions between Daphnia magna and Pseudokirchneriella subcapitata in a hypothetical two-species grazer-alga system. This study demonstrates how various direct and indirect effects of copper, for which no predictive toxicity model is available, can be integrated into the ecological model. First, the original chronic copper BLM for D. magna only predicts effects on reproduction (number of offspring produced), the most sensistive endoint. However, the observed effects on long-term survival and growth (less sensitive endpoints) are also of major importance for the ecosystem dynamics. Decreased survival and growth not only result in a decrease of the daphnid population but also result in a decreased grazing pressure on the algae. Thus, the chronic BLM (based on reproduction) was adapted to also predict chronic effects on survival and growth. Second, the original copper toxicity model for P. subcapitata predicts the effects of copper on biomass production. This model was adapted to predict changes of the specific growth rate. By combining both modified models an initial predictive multi-species ecological model was obtained, in which the reproduction, survival and growth terms of the daphnids and the growth rate term of the algae are dependent on the bioavailability of copper. This model was subsequently used to predict long-term ecosystem responses as a function of copper concentration and bioavailability. Predicted time-dependent patterns of ecosystem responses were mainly affected by DOC concentration and pH of the simulated surface waters.
Key words: Biotic Ligand Model, Daphnia magna, Algae, foodwed approach
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