ZOOPLANKTON COMPOSITION IN EUTROPHIC RESERVOIRS OF THE SEMI-ARID REGION OF RIO GRANDE DO NORTE STATE (Northeast Brazil).

Abstract

Species composition and abundance of the zooplankton were studied in six eutrophic reservoirs of Rio Grande do Norte State, which showed high concentrations of total phosphorus, high phytoplankton biomass and dominance by cianobacteria. Sampling was carried out during dry, rainy and transitional periods. Zooplankton also showed quantitative patterns suggestive of eutrophic conditions, expressed by high densities. Moreover it was observed a spatial differentiation in the composition of zooplankton community. Rotifers (specially Keratella tropica, Brachionus havanensis e Keratella americana) were the dominant forms in the zooplanktonic community of Itans, Passagem das Traíras and Sabugi reservoirs, while Calanoid copepods (mainly Notodiaptomus cearensis) dominated in Armando Ribeiro, Gargalheiras and Parelhas reservoirs. The results obtained point out to new relationships in the composition of zooplanktonic community in eutrophic reservoirs of the tropical semi-arid, including the occurrence of large-sized herbivorous zooplankton such as Calanoid copepods, which must be considered in the establishment of zooplanktonic indicators of eutrophic conditions in reservoirs.