The effects of water quality parameters, water level changes, and mixing on zooplankton community dynamics in a tropical high-mountain Lake Ardibo, Ethiopia

The diversity and abundance of the zooplankton community are affected by changes in physico-chemical parameters, trophic interactions, water level changes, and periodic mixing. In this study, the influence of environmental variables, water level changes, and periodic mixing on zooplankton distribution and abundance was seasonally studied for Lake Ardibo from October 2020 to September 2021 collected from 3 sites. Results on the physico-chemical variables indicated that all variables, except turbidity, varied significantly (p < 0.05) in all sampling seasons. A total of 33 zooplankton species were recorded, comprising 18 rotifers, 11 cladocerans, and 4 cyclopoid copepods. Zooplankton abundance significantly varied seasonally with peak abundance (4232.13 ind. L-1) recorded in the dry season and lowest numbers (402.42 ind. L-1) during the long rainy period. Redundancy analysis (RDA) results indicated that total phosphorus, ammonia, water temperature, silicon dioxide, and conductivity were the most significant driving forces for the seasonal successions in the abundance and distribution of zooplankton communities. Cyclopoid copepod abundance was significantly (p < 0.05) higher in the dry season, which could be correlated with the partial mixing (atelomixis) phenomenon that occurred during the dry period.