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Data of Dissertation

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Author: Pedro Antonio Zagatto.

Title: Ecotoxicological evaluation of reservoir Guarapiranga - SP - Brazil regarding the problem of toxic algae and algaecides.

Year: 1995.    Full text (in French)

Abstract

This biomonitoring study was carried out in Guarapiranga reservoir which is an important source for drinking water in Sao Paulo city, Brazil. Physico-chernical, biological and ecotoxicological results of the water and sediments from the Guarapiranga reservoir are hereby reported with the results of copper bioaccumulation. Toxicity of cyanophyces isolated from this reservoir, toxin retention by active charbon, toxicity studies 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, cWorophyll-a contents, as well as on the phytoplancktonic communities and water transparency, the Guarapiranga reservoir could be described as meso-hypereutrophic. Phosphate and copper leveis exceeded the standards of water quality required for preservation of aquatic !ife. Among the isolated species of cyanophyces, Oscillatoria quaaripunctulata, O. limnetica, O. amphibia, Phormidium sp, Microcystis incena as well as one of three strains of M. aeruginosa, ali were acutely toxic to rnice. 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 rnicrocrustaceans than to algae and fish species . The acute toxicity of these algicide rnixtures is less than additive. Nevertheless, phancktonic organisrns were good indicators for copper concentration in water. ln 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. IS mg of the adsorbant was sufficient to retain up to 5mg 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 catchrnent. Qur results show that the reservo ir is characterized by a dystrophic process, high algicide concentrations and subsequent toxicity of the water.

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