Abundance of Zooplankton in Relation to Environmental Variables in Oguta Lake, Imo State

Zooplankton communities are integral components of freshwater food webs, linking primary producers with higher trophic levels, and serve as sensitive bioindicators of environmental quality. This study investigates the abundance, composition, and diversity of zooplankton in relation to key environmental variables in Oguta Lake, Imo State, South East Nigeria, one of the largest natural lakes in the region. Zooplankton samples are collected monthly over twelve months during 2023 to 2024 using 60-micrometre mesh plankton tow nets at five sampling stations representing the open water, littoral, and riverine input zones. Simultaneously, water temperature, pH, dissolved oxygen, conductivity, transparency, total dissolved solids, nitrate, and phosphate are measured in situ. Preserved samples are counted and identified to the lowest practical taxonomic level using standard identification keys, with rotifers, cladocerans, and copepods constituting the primary groups of interest. Statistical analyses include Pearson correlation, principal component analysis, and redundancy analysis to relate zooplankton community structure to environmental gradients. Findings are expected to show maximum zooplankton density during the early rainy season and a positive correlation between phosphate concentration and rotifer dominance indicative of mesotrophic conditions. Copepod diversity peaks in the dry season when water transparency is highest. Recommendations address nutrient management in Oguta Lake's catchment area. Keywords: zooplankton, Oguta Lake, bioindicators, environmental variables, Imo State limnology