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Nutrients are essential for the growth of aquatic life; however, in excess, they can result in a decline in water quality, posing serious risks to both human and aquatic organisms. Human activities, such as urbanisation, industry, and farming, can increase the amount of nutrients and other elements that reach receiving waterbodies like Lake Victoria in Uganda, which can be problematic at elevated levels. There is therefore a strong need to evaluate recent changes in pollutant concentrations and their potential negative effects. To contribute to this gap and to explore the pollutant changes in Lake Victoria, a series of water chemistry data (phosphate, nitrate, potassium, ammonium, sodium, sulphate, silica and chlorine) was collected between 2016 and 2023 in Uganda’s Napoleon Gulf (NG) and Murchison Bay (MB), primarily by the Ministry of Water and Environment (MWE). These locations were chosen based on their vicinity to expanding urban centres and agriculture, and they are also areas where fishing frequently occurs. The datasets were collected at different water depths (0.5–24 m). Data were analysed with the use of IBM’s Statistical Package for the Social Sciences (SPSS 28.0) software and confirmed the excessive concentrations of pollutants within MB compared to NG. The analysis identified the different nutrient types that exceeded internationally recognised thresholds relating to acceptable water quality during the data collection period. Seasonal variations were observed, during the dry season; nutrient levels, however, in NG showed higher nutrient concentrations during the wet season. The study’s capacity to inform local authorities and policymakers about such potential major sources of pollution is of crucial importance for beginning to address the potential impacts on human health and aquatic life. Full article

Africa’s water needs are often supported by eutrophic water bodies dominated by cyanobacteria posing health threats to riparian populations from cyanotoxins, and Lake Victoria is no exception. In two embayments of the lake (Murchison Bay and Napoleon Gulf), cyanobacterial surveys were conducted to characterize the dynamics of cyanotoxins in lake water and water treatment plants. Forty-six cyanobacterial taxa were recorded, and out of these, fourteen were considered potentially toxigenic (i.e., from the genera Dolichospermum, Microcystis, Oscillatoria, Pseudanabaena and Raphidiopsis). A higher concentration (ranging from 5 to 10 µg MC-LR equiv. L⁻¹) of microcystins (MC) was detected in Murchison Bay compared to Napoleon Gulf, with a declining gradient from the inshore (max. 15 µg MC-LR equiv. L⁻¹) to the open lake. In Murchison Bay, an increase in Microcystis sp. biovolume and MC was observed over the last two decades. Despite high cell densities of toxigenic Microcystis and high MC concentrations, the water treatment plant in Murchison Bay efficiently removed the cyanobacterial biomass, intracellular and dissolved MC to below the lifetime guideline value for exposure via drinking water (<1.0 µg MC-LR equiv. L⁻¹). Thus, the potential health threats stem from the consumption of untreated water and recreational activities along the shores of the lake embayments. MC concentrations were predicted from Microcystis cell numbers regulated by environmental factors, such as solar radiation, wind speed in the N–S direction and turbidity. Thus, an early warning through microscopical counting of Microcystis cell numbers is proposed to better manage health risks from toxigenic cyanobacteria in Lake Victoria. Full article