COMMUNITY STRUCTURE OF ROTIFERS IN 2 ENVIRONMENTS OF THE UPPER RIVER PARANA FLOODPLAIN (MS) - BRAZIL

We evaluate the influence of abiotic and biotic factors on the communi ty structure of rotifers across a regional hydrological cycle in lotic and lentic environments of the upper River Parana. Depth, transparenc y, temperature, pH, electrical conductivity, dissolved oxygen, chlorop hyll a and densities of rotifers were measured at two stations in Lake Guarana (littoral and open water regions) and at one station in the R iver Baia (open water region). Highest densities of rotifers were foun d at the lake littoral. Canonical correlation analysis related environ mental variables with the densities of the most abundant rotifers. The strongest relationship was with chlorophyll a, dissolved oxygen, hydr ological level and water temperature. Diversity of rotifers at each st ation was mainly explained by fluctuations in hydrological level. Resu lts of grouping analysis suggested the formation of groups according t o phases of the hydrological cycle.