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(36-08) Assessing the toxicity of mixtures of pesticides and metals: Predicting ecological consequences using a Ceriodaphnia dubia feeding bioassay. Treuner, Anke*,1, Nogueira, Antonio2, Baird, Donald1, 1 Institute of Aquaculture, Stirling, Scotland2 Dept. Biologia da Universidade de Aveiro, Aveiro, Portugal ABSTRACT- Aquatic systems in or adjacent to agricultural landscapes in tropical systems can be exposed to continuous or intermittent pulses of a variety of toxic substances throughout the year, often at levels considered to have negligible impact as predicted by substance-specific risk assessments often carried out in temperate systems. Given the fragility of tropical ecosystems, and the possibility that co-occurring substances may have a joint additive effect, the question arises: are we underprotecting tropical habitats by failing to adequately consider this possibility? Evidence is accumulating that simple additivity models may be the most pragmatic approach to this problem, raising a second question: how should we quantify and predict mixture effects, particularly in the field? Our approach has been to assess the joint effects of combinations of substances on zooplankton grazing: a key component of productivity and nutrient cycling in many tropical aquatic ecosystems. To assess the suitability of feeding as an endpoint in mixture toxicity, the cladoceran Ceriodaphnia dubia feeding on microalgae was exposed to low concentrations of three commonly used pesticides with differing toxicological modes of action (chlorpyrifos, deltamethrin and atrazine) and a metal (cadmium). A further aim was to determine if the chemicals studied acted independently, by applying models of concentration addition and independent action to the data. For each compound, a feeding-response curve was established and concentrations around the feeding inhibition concentration (IC50 : Deltamethrin: 0.2 Key words: mixture toxicity, pesticides, Ceriodaphnia dubia, feeding bioassay |
g/L, Atrazine: 13mg/L, Cadmium: 10