We investigated the spatio-temporal dynamics of phytoplankton composition, chlorophyll-a as a proxy for algal biomass, and abundance in relation to environmental parameters in four Ethiopian soda lakes: Arenguade, Beseka, Chittu, and Shala. Triplicate water samples were collected from each lake from January to December 2020, four times in different seasons. Lake Chittu had the highest chlorophyll-a concentration, followed by Lake Arenguade, Beseka and Shala. Chlorophyll-a concentrations generally increased during the post rainy and dry season. The results of LR models are high for lakes Arengude, Beseka and Chittu. Lakes Shala and Beseka had the highest number of phytoplankton taxa, with both taxa composition and abundance dominated by Bacillariophyceae. Cyanoprokaryota, particularly Limnospira fusiformis, predominated in the abundance of Lakes Arenguade and Chittu. Water temperature, Secchi depth, turbidity, electrical conductivity, soluble reactive phosphorus, nitrate and silica significantly influenced the phytoplankton community structure. Long-term trend analysis revealed changes in phytoplankton biomass and lake taxonomic composition. The alteration in phytoplankton biomass and species composition of the lakes could be attributed to three factors: (1) frequent high-velocity explosions conducted for seismological studies in the past. This impact caused a dramatic increase in lake level in the case of Lake Beseka leading to a drop in nutrient concentration; (2) climate change and (3) salt content. Overall, our findings suggest that phytoplankton composition, biomass, and abundance varied according to seasonal fluctuations, emphasizing the possible effects of anthropogenic and natural causes on their community structure.

中文翻译：

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埃塞俄比亚四个苏打湖的浮游植物动态和环境变量

我们研究了埃塞俄比亚四个苏打湖（阿伦瓜德湖、贝塞卡湖、奇图湖和沙拉湖）的浮游植物组成、作为藻类生物量代表的叶绿素-a 以及与环境参数相关的丰度的时空动态。2020年1月至12月，每个湖泊采集了三次水样，不同季节采集了四次。奇图湖的叶绿素a浓度最高，其次是阿伦瓜德湖、贝塞卡湖和沙拉湖。叶绿素 a 浓度在雨季和旱季期间普遍增加。Arengude、Beseka 和 Chittu 湖的 LR 模型结果较高。沙拉湖和贝塞卡湖的浮游植物类群数量最多，其类群组成和丰度均以硅藻类为主。蓝原核生物，特别是梭形藻旋体，在阿伦瓜德湖和奇图湖中占主导地位。水温、Secchi深度、浊度、电导率、可溶性活性磷、硝酸盐和硅对浮游植物群落结构影响显着。长期趋势分析揭示了浮游植物生物量和湖泊分类组成的变化。湖泊浮游植物生物量和物种组成的变化可归因于三个因素：（1）过去为地震研究而频繁进行的高速爆炸。这种影响导致贝塞卡湖水位急剧上升，导致养分浓度下降；（2）气候变化和（3）盐含量。总体而言，我们的研究结果表明，浮游植物的组成、生物量和丰度根据季节波动而变化，强调了人为和自然原因对其群落结构的可能影响。