Zooplankton community comparisons among four tropical soda lakes: Insights into habitat preferences

Tropical soda lakes are unique ecosystems characterized by extreme environmental conditions that shape their biological communities. This study investigated the spatio-temporal variations in zooplankton communities in relation to key environmental variables across four Ethiopian soda lakes: Arenguade, Beseka, Chittu, and Shala. Samples were collected from each lake during four seasons: dry (January), pre-rainy (June), rainy (July), and post-rainy (November). In situ measurements were conducted using a multi-metric probe (HQ40d) and nutrients were analyzed at Addis Ababa University laboratory. Zooplankton samples were collected using vertical hauls with 30μm plankton net to ensure representative sampling. The study revealed dynamic seasonal changes in the lakes' physicochemical parameters, which were influenced by dominant environmental factors specific to each lake. Lake Shala exhibited the highest zooplankton species richness, followed by Lakes Beseka, Chittu, and Arenguade. Rotifers were the most species-rich within zooplankton communities, while cladocerans were rare at all sites. Seasonal abundance patterns varied among the lakes; peaks occurred during the rainy season in Arenguade and Chittu, but during post-rainy and dry seasons in Beseka and Shala, respectively. Redundancy analysis (RDA) identified water temperature, dissolved oxygen, electrical conductivity, nitrate, soluble reactive phosphorus, and turbidity as the major environmental drivers of variation in zooplankton communities. This study highlights the critical role of zooplankton, particularly rotifers, in shaping aquatic ecosystems, emphasizing their adaptability to environmental conditions and significance as indicators of ecosystem health. Understanding the intricate relationships between nutrient dynamics, species interactions, and environmental stressors is essential for developing effective conservation and management strategies for these ecosystems.