This work shows the length-weight regressions established for the five most frequent and abundant cladoceran species (Bosmina hagmanni, Bosminopsis deitersi, Ceriodaphnia cornuta, Diaphanosoma birgei, and Moina minuta) in two stations at Lake Batata. This lake has received for 10 years very fine bauxite processing tailings, which is responsible for the thick layer over the natural sediment still observed in its western section (impacted station). The individuals were separated into size classes, the dry weight values were determined for each class and were used for establishing weight-length equations. Bosminopsis deitersi and Ceriodaphnia cornuta were the species showing the smallest size in the two sampled areas (0.152 to 0.322 mm) and Diaphanosoma birgei was the largest (0.284 to 0.722 mm). In the natural station, Moina minuta and Bosminopsis deitersi were the lightest species (0.174 to 0.334 and 0.074 to 0.278 µg, respectively) and in the impacted station, Bosmina hagmanni and Moina minuta were the lightest (0.248 to 1.555 and 0.210 to 0.566 µg, respectively). In general, individuals from the impacted station exhibited smaller body sizes (0.152- 0.684 mm) and higher weight (0.208 - 1.983 mm), which can be explained by the ingestion of tailing particles. The equations established were shown to be adequate for weight estimates of the analyzed species since the differences found between the observed and estimated weights values were not statistically significant.
Amazonian lake; zooplankton; cladoceran; length-weight relationships
