Estrutura da comunidade zooplanctônica em áreas de cultivo em tanques rede no reservatório da UHE de Furnas-MG, compartimento Rio Sapucaí

Abstract

The culture of fish in net cages is growing in the Furnas reservoir. The feed and antibiotics, used in fish farming, generate impacts to the environment and can negatively modify the aquatic ecosystem. Inventories on biological diversity of these ecosystems are fundamental to implement conservation programs, rational use of resources and pest control. Knowledge about the life cycle of zooplankton species allows us to understand the role of each species in the ecosystem and provides data for the calculation of secondary production. In this work used nonparametric richness estimators (ACE, Chao1, Jackknife1 and Bootstrap) aiming minimal sampling effort (hauls with net or pump, volume and number of samples) to reach the probable maximum number of species in the reservoir limnetic region. Monthly samplings in Furnas reservoir were performed for one year at five points in two areas where fish cultivation in net cage occurs, in order to observe the impact of this activity on zooplankton community and physical and chemical water variables. In the laboratory, the life cycle parameters of two species of Cladocera, Scapholeberis armata freyi and Oxyurella longicaudis, were analyzed. The analysis shows that 400 liters of water and eight monthly samplings throughout the year is satisfactory to access 90% the richness of the studied compartiments. The concentration of nitrite and nitrate are according to the established by CONAMA. The curves ABC of cumulative biomass and density and the value of W recorded for all sampling points indicate a moderate disturbance in the environment. Due to the large water volume of this reservoir, nutrients and organic matter resulting from fish farming are diluted and do not affect the ecosystem functioning. From laboratory culture, the longevity of S. armata freyi was higher than that observed for other species of the family Daphnidae, when the food source was algae only. The total production of eggs of O. longicaudis was lower than that observed for other species of the Chydoridae family, since it showed a longer duration of embryonic development, and reached the primiparous stage later. DNA barcode is also reported for O. longicaudis isolated in Brazil in order to facilitate future identification in zooplankton community studies.