Zooplâncton como bioindicadores do estado trófico na seleção de áreas aqüícolas para piscicultura em tanque-rede no reservatório da UHE Pedra no rio de Contas, Jequié – BA

Abstract

Zooplankton as bioindicator of trophic state in reservoir of the Pedra Hydroelectric Power Plant (BA). In the reservoir of the Pedra hydroelectric power plant (BA). In the Northeastern region of Brazil, few works have been developed about the use of zooplankton as bioindicator of trophic state. The usage of zooplankton bioindicator allow to determinate previously the changes in aquatic environment; as the zooplankton shows high sensibility for that changer, they are considered as an useful tool in evaluation of agnatic areas as they are directly relation with e trophic state. Samples of water were obtained in 79 stations along the euphotic zone of the reservoir of the Pedra Hydroelectric Power Plant (BA), distributed in the enclosures formed along the reservoir lotic, transitional and lentic regions, in January and February 2006. The results show that of the 24 taxa found, only five (Diaphnia gessneri, Diaphanosoma spinulosum, Notodiaptomus cearensis, N. iheringi e Lecane lunaris) were selected as bioindicator of trofic state. The Calanoida were more representative than Cyclopoida, in most stations. In addition of the high occurrence frequency of cladocerans may be regarded as an indicator of good water quality and the presence Hexarthra intermedia, a rotifer indicating oligotrophic waters. The correlation between zooplankton diversity and the trophic state of the enclosures evidences that amongst the 79 sampling stations, 21 (27%) of them had presented low diversity, 56 medium (71%) and two (3%) high. The enclosures of the lotic region of the reservoir have been characterized as presenting mesotrophic condition, most of them (73.7%) with medium diversity; while in the other regions of the reservoir, an oligotrophic condition prevailed, although also presenting medium diversity values.