Condição trófica e qualidade das águas das lagoas da APA Carste de Lagoa Santa, Minas Gerais

Abstract

This research aimed to provide a set of suggestions of environmental actions and management with subsidies for the preservation of water resources and public health, in favor of the natural lakes system of the Carstic of Lagoa Santa Environmental Protected Area, using ecological metrics such as trophic indices, dissolved organic carbon content-DOC, phytoplankton assemblages, morphometric characteristics of the lakes and major uses soil occupation of the basin, in order to indicate the trophic state and environmental quality of these ecosystems. Basic limnological parameters were measured in four lakes (Confins, Olhos dÁgua, Sumidouro and Mares) during dry and rainy periods of 2009 and 2010. Surveys of land use and occupation and morphometric data were obtained specifically for Lake Sumidouro. The lakes trophic level ranged from oligotrophic to hypereutrophic according to the distinct trophic indices used which indicated Lake Confins as a hypereutrophic lake. The DOC concentration was higher in lakes Sumidouro and Confins. Moreover, it offered (through regression analysis) a logarithmic relationship with two of the evaluated trophic indices. The phytoplankton functional groups J, P, X1 e TC, which were associated with eutrophic environments, correlated positively with total-N, total-P, PO4-P and TSI, as well as most of the samples from lake Confins. DOC and phytoplankton assemblages proved to be valuable tools in evaluating trophic status, despite exhibiting limitations as any environmental evaluation methods, as demonstrated by the use of trophic indices in general. Morphology, land use and occupation of the basin and estimation of total phosphorus load indicted to be potential predictive tools to be used in environmental analyses of environments vulnerable to eutrophication events.