Zooplâncton como indicador de estado trófico em reservatórios no semiárido

Abstract

Aiming to use zooplankton as a tool for indicating the trophic state of reservoirs in semiarid, we performed an analysis of the composition, density and spatial-temporal distribution of zooplankton in relation to trophic indicators in three reservoirs (Namorados, Taperoá II and Soledade) in the sub-basin of the Taperoá river. Samples were collected in Jan/12 and May/12 at three points (water catchment, central portion and amount). The Soledade reservoir was, generally, considered eutrophic. Taperoá II ranged from oligotrophic to eutrophic. Namorados was, generally, considered oligotrophic. We found 35 species of zooplankton, being 27 species of Rotifera, 3 species of Cladocera and 5 species of Copepoda. In relation to trophic state, 10 species were found exclusively in oligotrophic points, two species in mesotrophic and three species in eutrophic points. Seven species were absent for only one trophic state; these, two did not occur in oligotrophic points, one did not occur in mesotrophic and four did not occur in eutrophic points. Oligotrophic points had the lowest average density (419 ind.L1 ), followed by mesotrophic (857 ind.L-1) and eutrophic points (1202 ind.L-1). In different trophic states, Rotifera was the dominant group, followed by Copepoda and Cladocera, except in Jan/12 in the oligotrophic points where the relative abundance of Copepoda was higher than the Rotifera. The species B. calyciflorus, B. urceolaris and T. decipiens may be used as indicators of eutrophic environment, and the species H. mira and K. cochlearis may be used as indicators of oligotrophic and/or mesotrophic environment.