This study discerned the causes of cyanobacteria blooms in Lake Naivasha (Kenya). We hypothesized that phytoplankton and cyanobacteria biomass respond to hydrologic cycles, peaking during the wet season, and that microcystin (MC) concentrations are highest following the bloom collapse. Hydrologic loading (inferred from rainfall and lake level changes) and phytoplankton responses in two basins of the lake were monitored over a wet season followed by a dry season between September 2010 and March 2011. Results show that both phytoplankton and cyanobacteria biomass peaked in both basins during the wet season, with associated peaks in particulate MC concentrations. Even though phytoplankton and cyanobacteria biomass were higher in the smaller deep basin, MC concentrations were lower than in the large shallow basin. The high-MC levels during the wet season were followed by a greater MC production per cyanobacteria biomass unit in the dry season in both basins. The timing of the cyanobacteria bloom suggests that its formation was likely controlled by large nutrient influxes from the contributing catchment to the lake associated with intense rainfall following an intense drought, posing a risk to the health of the community due to increased MC levels.

中文翻译：

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评估肯尼亚奈瓦沙湖蓝藻和蓝藻毒素的潜在健康风险

这项研究确定了奈瓦沙湖（肯尼亚）蓝藻大量繁殖的原因。我们假设浮游植物和蓝藻生物量对水文循环有反应，在雨季达到峰值，并且微囊藻毒素 (MC) 浓度在水华崩溃后最高。在 2010 年 9 月至 2011 年 3 月的雨季和旱季期间，监测了湖泊两个盆地的水文负荷（从降雨量和湖泊水位变化推断）和浮游植物响应。 结果表明，两个盆地的浮游植物和蓝藻生物量均达到峰值在雨季，与颗粒 MC 浓度相关的峰值。尽管较小深盆中的浮游植物和蓝藻生物量较高，但 MC 浓度低于大型浅盆中。在雨季高 MC 水平之后，两个盆地在旱季每个蓝藻生物量单位的 MC 产量更高。蓝藻水华的时间表明，它的形成可能是由大量养分流入湖控制的，这与严重干旱后的强降雨有关，由于 MC 水平增加，对社区的健康构成风险。