UTTAR PRADESH JOURNAL OF ZOOLOGY

Background: The modification of the natural flow regime alters the habitat's natural and aquatic fauna. These alterations cause changes in the structure of benthic macroinvertebrate communities. In the Sassandra river basin, despite significant hydrological changes observed when electric turbine sluice gates were opened or closed, studies of the impact of these disturbances on benthic macroinvertebrates are non-existent. Following the inventory and characterisation of spawning grounds, it was important to assess the impact of closing and opening the Buyo dam gates on benthic macroinvertebrates, an essential and sensitive component in any environmental disturbance.

Aim: This work aimed to determine the impact of hydrological variations downstream of Buyo Lake on benthic macroinvertebrate communities.

Methodology: The study was conducted at the Climate Change and Biodiversity Department, Natural Environments and Biodiversity Conservation Laboratory, Hydrobiology Research Unit, between June 2018 and May 2019. Benthic macroinvertebrates were sampled using a Van Veen grab from June 2018 to May 2019 at three selected sites. Hydrological data were provided by the Ivorian Company of Electricity (CIE) of Buyo. These data concern the water flows released by the gates of the dam and the water flows generated from the hydroelectric plant.

Results: In total, 1011 individuals, distributed among 4 phyla, 7 classes, 12 orders, 16 families, and 23 taxa, were inventoried. The most represented families were Thiaridae (89.51%). This was followed by the Chironomidae (4.94%). Among species, Melanoides tuberculata was the most dominant (89.51%). The peak of species richness was observed in December when the water flow released was 108.59 m³/s. The low value of species richness was observed where the water flow was 1549.54 m³/s. As for abundance, the peak was observed in June when the turbid water flow was 291.61 m³/s. The lowest was observed in September at water flows released of 1139.17 m³/s. Student's t-test showed that taxonomic richness is greater during the overflow rates (p = 0.0001). 

Conclusion: This study allowed for the inventory of the benthic macrofauna downstream of the dam and showed the effect of water flows generated by the activities of the dam on benthic macroinvertebrates. These results will serve to the development of appropriate measures to ensure better management of aquatic organisms for future developments on the Sassandra River.