Qualidade da água e estrutura da comunidade zooplanctônica em uma lagoa com atividade de piscicultura em tanques-rede no médio Rio Doce MG

Abstract

Fish farming activity in net cages has expanded in several countries, including Brazil, as an alternative income generation for the population and animal protein supply of high value. However, depending on management, farming intensity and water body characteristics, this type of fish farming can negatively change the environment. This study investigated the potential impact on water quality and the zooplankton community structure (in terms of diversity, richness and total density) of growing tilapia (Oreochromis niloticus) in net cages in an oligotrophic lake in the middle Rio Doce (MG). The physical and chemical water properties, together with zooplankton community structure, were compared along a distance gradient from the cages. There was no significant spatial variation in temperature, pH, electrical conductivity, dissolved oxygen, turbidity, total nitrogen, nitrite, nitrate, ammonium, total phosphorus and orthophosphate. In the rainy season, the concentration of chlorophyll-a was inversed correlated with nitrate concentration, with the highest concentration of chlorophyll-a recorded in areas close to the ponds. One hundred taxa were identified and Rotifera was the most representative group (67 species). The composition and diversity of zooplankton community did not change along the gradient, although it was observed in the dry season lower specie richness near the net cages. Spatial variations were not recorded, but there were evidences of short-term change in zooplankton communities. The long-term effects of this activity remain unknown.