Zooplankton communities as eutrophication bioindicators in tropical reservoirs

Eutrophication is a process characterized by an increase in the aquatic system productivity, which causes profound changes in the structure of its communities. Owing to the high environmental sensitivity of planktonic species, the study of their communities can indicate the deterioration of the environment. The Jaguari and Jacarei reservoirs are part of the Cantareira System, supplying water to S (a) over tildeo Paulo inhabitants and that has been affected by several forms of continuous human interference. Here we analyze some properties of the zooplankton community as bioindicators of eutrophication and water quality change. In situ physical and chemical measurements were carried out, water was collected for analysis and quantitative zooplankton samples were taken at eight sites in the two reservoirs, in both seasons, dry and rainy. Species were identified and their numerical abundances and biomasses were determined and used to estimate two biological indices. The overall trophic state and zooplankton structure, the Calanoida/Cyclopoida ratio and the k-dominance curves were associated with the disturbance levels, mainly represented by nutrient river inputs and by water level fluctuations. The Jaguari Reservoir was more eutrophicated than the Jacarei Reservoir, as evidenced by the obtained indices values. The zooplankton community properties used as indicators of the reservoir trophic state were useful monitoring tools.