Abstract
This research represents an evaluation of the patterns of variation in the composition of the zooplankton community in the region of Porto Trombetas, State of Pará, Brazil. In all, 15 sampling stations were
established in the Trombetas River, Mussurá Lake and Batata Lake, at which four series of samples were
taken during the extremes of the regional hydrological cycle. At each station, basic limnological variables
and zooplankton community composition were determined. Collecting efforts were concentrated in Batata
Lake because this lake has received tailings generated from bauxite processing for ten years (1979-1989).
Among ambient variables only chlorophyll a, water transparency and suspended solids showed changes
attributed to the presence of these tailings. The rotifers were highest in number of species, followed by
cladocerans and copepods. The three environments differed in zooplankton community composition. These
changes were less evident during the filling period when rising water level acted most intensely to interlink
the systems, leading to the greatest faunistic homogeneity. Interference from the bauxite tailings could not
be clearly identified because for the zooplankton community such interference appears to be a sporadic
factor which occurs more intensely during periods such as drawdown.
