ABSTRACT
Cladocera zooplankton are acknowledged globally as vital indicator of water quality in rivers. In this study we evaluated the species composition, relative abundance, spatial and seasonal variation of Cladocera zooplankton populations at Orhionmwon and Ikhiogbe Rivers, Ikpe, Edo state, Nigeria. The aim of the study is to assess the abundance, diversity and distribution of cladoceran assemblage in Orhionmwon and Ikhiogbe Rivers in the river. Qualitative zooplankton samples were collected monthly in four distinct stations by filtering water through a 55μm mesh hydrobios net. A total of 340 Cladocera species were encountered from 16 taxa, 13 genera, 4 families namely, bosminidae, chydoridae, macrothricidae, and sididae. The most dominant species recorded was Kurzia longirostris followed by Camptocercus lilljeborgi, followed by Chydorus sphaericus, and then Diaphanosoma excisum. Across the stations, station 3 recorded the highest abundance, species richness, Shannon-Weiner and Margalef indices. Monthly variation reveals that the wet season month of August recorded the highest number of cladocera, followed by dry season month of November. The correlation matrix results revealed that some physico-chemical parameters including water temperature, water level, nitrate, chromium and lead were strongly correlated with cladocera species abundance. Conclusively, the results indicate that it is necessary to understand the taxonomic diversity and ecological indicators of zooplankton, considering their importance for the basis of inlandfood webs and biomonitoring.
