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Evaluation écotoxicologique du réservoir Guarapiranga, SP-Brésil, en relation avec le problème des algues toxiques et des algicides

Abstract : This biomonitoring study was carried out in Guarapiranga reservoir which is an important source for drinking water in Sao Paulo city, Brazil. Physico-chemical, biological and ecotoxicological results of the water and sediments from the Guarapiranga reservoir are hereby reported with the results of copper bioaccumulation. Toxicity of the algicides, hydrogen peroxide and copper sulfate, towards aquatic organisms and the proposition of the maximal allowable limits of the toxic algae in the water are presented too. Based on the total phosphate, orthophosphate, chlorophyll-a contents, as well as on the phytoplancktonic communities and water transparency, the Guarapiranga reservoir coulb be described as meso-hypereutrophic. Phosphate and copper levels exceeded the standards of water quality required for preservation of aquatic life. Among the isolated species of cyanophyces, Oscillatoria quadripunctulata, O. limnetica, O. amphibia, Phormidium sp, Microcystis incerta as well as one of three strains of M. aeruginosa, all were acutely toxic to mice. For Daphnia only O. redekei caused acute toxicity. Hydrogen peroxide and copper sulfate were then tested for their algicidal activities. Filamentous algae were more sensitive to the hydrogen peroxide than to copper. However, these two products were more toxic to microcrustaceans than to algae and fish species. The acute toxicity of these algicide mixtures is less than additive. Nevertheless, phancktonic organisms were good indicators for copper concentration in water. In fact, copper was slightly bioaccumulated in fish muscles. Fish could still be considerated as acceptable for human consumption.The retention capability of activated charcoal was tested for the algal toxins. 15 mg of the adsorbant was sufficient to retain up to 5 mg of toxic algae dry weight. The Guarapiranga sediments could be considered as moderately to highly polluted by copper, although the sediments did not cause toxicity to Hyallela. The highest polluted area of this reservoir is located near the water catchment. Our results show that the reservoir is characterized by a dystrophic process, high algicide concentrations and subsequent toxicity of the water
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Pedro Zagatto. Evaluation écotoxicologique du réservoir Guarapiranga, SP-Brésil, en relation avec le problème des algues toxiques et des algicides. Ecotoxicologie. Université Paul Verlaine - Metz, 1995. Français. ⟨NNT : 1995METZ052S⟩. ⟨tel-01777101⟩



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