Assessment of Harmful Algal Bloom Potential in Kainji Lake, Niger State

Kainji Lake, situated in Niger State, North Central Nigeria, is the largest artificial lake in West Africa and serves critical functions in hydropower generation, irrigation, and inland fisheries. Increasing nutrient loading from agricultural runoff, domestic wastewater, and atmospheric deposition has raised concerns about the potential for harmful algal bloom development, which can disrupt aquatic ecosystems and compromise water supply safety. This study assesses the trophic status and harmful algal bloom potential of Kainji Lake through seasonal water quality monitoring and phytoplankton community analysis across six sampling stations during 2023 to 2024. Total nitrogen, total phosphorus, chlorophyll-a, Secchi depth, and dissolved oxygen are measured monthly to compute the Carlson Trophic State Index. Phytoplankton samples are preserved and identified to genus level using light microscopy, with special attention to cyanobacterial genera associated with toxin production, including Microcystis, Anabaena, and Cylindrospermopsis. Microcystin toxin concentrations are determined using enzyme-linked immunosorbent assay for samples collected during bloom events. Results are expected to indicate a shift towards mesotrophic to eutrophic conditions in northern lake sections receiving the greatest agricultural runoff. Findings inform lake management recommendations directed at the Kainji Lake National Park Authority and the Hadejia Jama are River Basin Development Authority. Keywords: harmful algal blooms, Kainji Lake, eutrophication, cyanobacteria, trophic state