Composition, Density and Distribution of Zooplankton in South West and East Lakes of Beira Lake Soon after the Restoration of South West Lake

A study was carried out in restored South West Lake and non-restored East Lake, of Beira lake with the objective of determining the species composition, density and distribution of zooplankton. Water was sampled from the surface and at a depth of 1 m, from February to March, 2005 between 0900-1130 h. Three rotifers species; Brachinonus calyciflorus, Keratella tropica, Filinia sp., three cladocerans species; Diaphanosoma excisum, Ceriodaphnia cornuta, Moina micrura and one copepod species; Thermocyclops decipiens were recorded in both lake sections of Beira lake, while the rotifers Brachinonus angularis and Brachinonus falcatus were confined to East lake and the rotifer Anuraeopsis sp. was confined to South West lake. B. calyciflorus was the dominant species among the zooplankton. Among cladocerans, C. cornuta was the dominant species. Comparing the two lakes, densities of B. calyciflorus, M. micrura and C. cornuta was significantly higher (P<0.05) and Filinia sp. was significantly lower (P<0.05) in the East lake. No significant differences (P>0.05) were evident for T. decipiens, K. tropica and D. excisum. The exclusive occurrence of T. decipiens and the B. calyciflorus being the dominant rotifer and C. cornuta being the dominant cladoceran in the selected study areas of Beira lake indicate that the lake is in a highly eutrophic state. In addition, B. calyciflorus, B. angularis and B. falcatus which are indicator rotifer species of eutrophic condition signify that the non-restored East lake is at a higher trophic state compared to the restored South West Lake.