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2M - Monitoring of function and structure (WEP/154) Acute toxicity of heavy metals and organic substances to Ceriodaphnia silvestrii (Cladocera) in the presence of polysaccharides excreted by phytoplanktonic algae. OLIVEIRA-NETO, Abilio1, VIEIRA, Armando2, BOTTA-PASCHOAL, Clarice3, MIRANDA, Viviane3, MASUTTI, Mariana3, SANTOS, Roseli1, 1 Santo Amaro University, São Paulo, SP, Brazil2 São Carlos Federal University, São Carlos, SP, Brazil3 São Paulo University, São Carlos, SP, Brazi ABSTRACT- Polysaccharides excreted by phytoplankton can interact with chemical toxicants, interfering with its toxicity on aquatic communities. Thus, toxicity of heavy metals and organic substances may vary according to lake and reservoir trophy and even between compartments in the same environment. Another important consequence of such phenomenon is that chronic toxicity tests utilizing planktonic algae as food, may show underestimated results related to polysaccharide excretion by the algae. Aiming to better understand metals toxicity in aquatic ecosystems, sensitivity of Ceriodaphnia silvestrii for cadmium, chromium and 1.4 chloraniline was tested in the presence and absence of polysaccharides from Microcystis aeruginosa and Anabaena spiralis (Cyanobacteria), Aulacoseira granulata (Bacillariophyceae) and Selenastrum capricornutum (Chlorophyceae) cultures. The polysaccharide concentrations utilized in the acute toxicity experiments were similar to the ones found in eutrophic reservoirs (0,30 mg/L. The results showed a decrease in toxicity of these chemical toxicants to C. silvestrii in the presence of polysaccharides, indicating that eutrophication may reduce toxicity effects on planktonic organisms and that chronic toxicity tests must be better monitored and understood, in order to avoid biased toxicity results. Key words: phytoplankton, polysaccharides, heavy metals, organics |
