The reservoirs of the Cantareira System (Brazil, São Paulo): the relations between bioindicators benthic organisms and the heavy metals contamination.

Abstract

The potentially toxic metals are among the pollutants of most concern to aquatic environments. The Cantareira System is the main supplier of water for the Metropolitan Region of São Paulo. In recent years, there has been systematic application of copper in Atibainha downstream, leading to the hypothesis that the Paiva Castro reservoir is contaminated. It is recognized that contaminants tend to accumulate in the sediments and organisms living therein as macroinvertebrates (MIB). This research aims to: detect changes in the composition and structure of MIB in areas with different concentrations of metals; verify the occurrence of bioaccumulation of Cu in the MIB; verify relationships between morphological changes and concentrations of metals in sediments as well as perform a diagnosis of the quality of the system with the use of bioindicators. Samples were collected at nine points over three reservoirs: Jaguari-Jacarei; Cachoeira and Paiva Castro. Lectures of transparency, pH, temperature, dissolved oxygen and conductivity of the water was measured. Water samples were collected for the determination of metals. Regarding sediment concentrations were determined for Cd, Ni, Zn, Pb, Cu, Cr, As, Fe and Al and the proportions between fine, coarse fractions and organic matter content. We determined the proportions of changes in mouthparts of Chironomidae. Data obtained to date indicate the possibility of contamination. Statistical analysis indicated reduced diversity and density of organisms with increasing concentrations of Cr and an increase in the proportion of changes in the mouthparts against the concentrations of Cu. To confirm the effects of sediments on the Paiva Castro chironomid larvae, one in situ experiment with C. riparius larvae will be held. An experiment ex situ evaluate the effects of different concentrations of Cu over organisms