Assessment of Zooplankton Community as Indicators of Pollution in Choba River, Rivers State, South South Nigeria

This study assesses the zooplankton community structure of the Choba River in Rivers State, located in Nigeria's South South geopolitical zone, with emphasis on its utility as a bioindicator of organic pollution arising from adjacent university and residential settlements. Zooplankton respond rapidly to environmental perturbations, making them effective early warning indicators of aquatic ecosystem degradation. Water samples were collected monthly for six months at four stations along a pollution gradient from a relatively clean upstream station to a downstream station receiving runoff from the University of Port Harcourt campus and adjacent settlements. Zooplankton were concentrated using a 55 micrometre mesh net and identified microscopically. Physicochemical parameters were measured in situ. A total of 34 zooplankton taxa were identified. Protozoa and Rotifera dominated at the most polluted stations, while Copepoda and Cladocera were more abundant at cleaner stations. The Margalef diversity index declined consistently from upstream (2.8) to downstream (0.9). Brachionus calyciflorus, a pollution-tolerant rotifer, was among the most abundant taxa at the most impacted stations. Dissolved oxygen and nitrate were the strongest predictors of zooplankton community composition in canonical correspondence analysis. The study demonstrates the diagnostic value of zooplankton community analysis for monitoring the Choba River and recommends its integration into environmental monitoring protocols around the University of Port Harcourt. Keywords: zooplankton, bioindicators, pollution, Choba River, Rotifera.