Eutrophication of Lake Victoria led to changes in its phytoplankton communities. However, different levels of eutrophication exist in the open lake and the bays, and between embayments. This study utilized spatial and temporal sampling of Napoleon Gulf and Murchison Bay, exhibiting different trophic conditions. Over one year, we investigated phytoplankton biomass, richness, diversity and dissimilarity, and related the dynamics of the dominant species to the limnological and climatic conditions. The results confirmed that Napoleon Gulf and Murchison Bay showed large differences in eutrophication status, with lower nutrient concentrations in Napoleon Gulf than in Murchison Bay, where a strong gradient was observed from inshore to offshore areas. These nutrient dynamics resulted in a 4 to 10 fold higher chlorophyll-a in Murchison Bay than in Napoleon Gulf. From the embayments, 135 phytoplankton taxa were recorded with no significant differences in alpha diversity. However, high dissimilarity in community structure was observed in beta diversity, mostly due to a turnover among the dominant toxigenic species. Thus, from a similar species pool, there was a shift in the dominant toxigenic cyanobacteria from Microcystis flos-aquae and M. aeruginosa in Murchison Bay, Dolichospermum circinale and Planktolyngbya circumcreta in Napoleon Gulf to D. circinale in the offshore stations. These cyanobacteria are toxigenic taxa with known health hazards. Using partial least square models, we showed that both climatic variables (e.g. wind, solar radiation) and levels of inorganic dissolved nutrients (e.g. SRP, NO₃^–, and NH₄⁺) are the main drivers of differences and dominance in cyanobacteria communities in northern Lake Victoria.

维多利亚湖的富营养化导致其浮游植物群落发生变化。然而，在开阔的湖泊和海湾以及海湾之间存在不同程度的富营养化。本研究利用拿破仑湾和默奇森湾的空间和时间采样，表现出不同的营养条件。一年多来，我们调查了浮游植物的生物量、丰富度、多样性和差异性，并将优势物种的动态与湖沼学和气候条件联系起来。结果证实，拿破仑湾和默奇森湾的富营养化状况存在较大差异，拿破仑湾的养分浓度低于默奇森湾，后者从近海到近海地区观察到强梯度。这些营养动态导致默奇森湾的叶绿素 a 比拿破仑湾高 4 到 10 倍。从海湾记录到 135 个浮游植物分类群，α 多样性没有显着差异。然而，在β多样性中观察到群落结构的高度差异，主要是由于主要产毒物种之间的转换。因此，从相似的物种库中，主要产毒蓝藻从Murchison Bay的Microcystis flos-aquae和M. aeruginosa，拿破仑湾的Dolichospermum circinale和Planktolyngbya circlecreta到近海站的D. circinale。这些蓝藻是具有已知健康危害的产毒类群。使用偏最小二乘模型，我们表明气候变量（例如风、太阳辐射）和无机溶解养分水平（例如 SRP、NO ₃ ^–和 NH ₄ ⁺）是蓝藻群落差异和优势的主要驱动因素。维多利亚湖北部。