Benthic Macroinvertebrates Structure of Two Agropastoral Dams, Nanan and Zatta: Yamoussoukro, Cote d’Ivoire

Aims: We are investigating benthic macroinvertebrates in two rice-growing dams and assessing their pollution levels. 
Place and Duration of Study: Nanan and Zatta Dams of Yamoussoukro in Côte d’Ivoire from April 2021 to March 2022. 
Methodology: Samples were collected monthly with a Van Veen bucket and a dip net and the environmental variables measured. 
Results: The values of the physico-chemical variables show that the waters are warm and more mineralized at Nanan than at Zatta. The species richness is higher at Zatta with 75 taxa present against 42 taxa at Nanan. The population is globally dominated by insects at Zatta, but a strong representation of Molluscs is observed at Nanan. The abundance of Molluscs indicates organic pollution in the Nanan dam. The water pollution tolerance index between the two dams showed a predominance at Zatta, of the Ephemeroptera group which are polluo-sensitive organisms against a predominance at Nanan, of the Diptera group which are polluo-resistant. The Shannon index and the others indexes of the two sites confirm a clear water pollution in Nanan compared to Zatta. 
Conclusion: These results suggest that the Zatta dam is in better condition than the Nanan dam. However, these two dams must be bio-monitored.