Combining uptake and subcellular partitioning/toxicokinetics and toxicodynamics in modelling Cu2+ toxicity to zebra mussels, taking into account water chemistry

• Applicant: Dr. Thi Thu Yen Le, Ph.D.
• Subject Area: Animal Physiology and Biochemistry ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 322918513

Metal toxicity to organisms is determined by various factors. Abiotic ligands in the environment might affect the amount of metals available for uptake. Dissolved organic carbon may complex metals, reducing the interactions of the metals with organisms. Major cations, e.g. Na+ and Ca2+, might compete with toxic ions for binding to sites on biological surfaces, influencing the uptake of toxic metals. Bioaccumulation is a prerequisite, but not always a reliable predictor of metal toxicity, attributed to the capacity of organisms to sequester and detoxify metals. Therefore, subcellular partitioning is another determinant of metal toxicity. These factors have separately been considered in different approaches. Effects of environmental chemistry on metal speciation as well as accumulation at biological surfaces have been included in the Biotic Ligand Model. Metal bioaccumulation has been predicted as a balance of influxes and effluxes in biodynamic models and related to toxic effects in the Critical Body Residue approach. Subcellular partitioning has been taken into account in modelling metal toxicity, but shortcomings are inherent in available approaches. For instance, the assessment of metal exposure based on the induction of metallothionein-like proteins does not account for other detoxification mechanisms. Dynamic subcellular partitioning of metals cannot effectively be described by a ratio between metal concentrations in the metal-sensitive and biologically detoxified fractions. Further delineation of subcellular partitioning does not consider metal accumulation in sensitive fractions when detoxification mechanisms are not overwhelmed whereas relationships between subcellular partitioning and biological responses are lacking.The zebra mussel Dreissena polymorpha has widely been used in biomonitoring programs, particularly because of its widespread distribution, high filtering efficiency, and high capacity to accumulate metals. The delineation of metal subcellular partitioning in the zebra mussel facilitates more accurate estimates of metals biomagnified in other aquatic organisms like fish and crustaceans. Although bioavailability and toxicity of Cu2+ to aquatic organisms have been extensively investigated, uncertainties are still remaining in available approaches, probably related to the exclusion of some of the factors mentioned above.The proposed research aims at developing a model for predicting Cu2+ toxicity to the zebra mussel, taking into account influence of environmental conditions, bioaccumulation, and the ability of the zebra mussel to detoxify and sequester Cu. The proposed model is a combination of uptake kinetics and subcellular partitioning dynamics while accounting for effects of environmental chemistry. The toxicity of Cu2+ will be related to the accumulation of Cu at the metabolically-active organs represented by the metal-sensitive fraction, which will be simulated based on uptake, elimination, and detoxification.

• DFG Programme: Research Grants