Ecological impact of river impoundment on zooplankton

Abstract

The current study was carried out to assess the ecological impact of impoundment using zooplankton as indicators. Sampling was conducted at two stations Bui and Bamboi that are located upstream and downstream of the dam, respectively. Sixteen species of zooplankton belonging to the order Cladocera (suborder Copepoda) were identified. Cladocerans were dominated by Leptodora sp. while copepods by Cyclops sp. Cladoceran densities increased from 29.67 ind./m3 in the pre-impoundment period to 1179.4 ind./m3 in the immediate post-impoundment period with a significant difference (p < 0.05) between these periods recorded. Hence, the abundance of Cladocerans varied following the Bui dam impoundment on the Black Volta River. The study into seasonal zooplankton distribution showed that zooplankton abundance reached the highest values during the wet season. Abundance of zooplankton groups at the upstream station was significantly higher (p < 0.05) than that at the downstream station, indicating the impact of impoundment on zooplankton ecology downstream. Since zooplankton was more abundant during the wet season, factors such as climatic changes and/or dam construction that modify the flooding pattern of the river will also alter zooplankton community structure in the newly created Bui reservoir and may have serious implications for fish production in the entire Black Volta ecosystem.