Patterns of molluscan biodiversity and abundance following reservoir creation in Burkina Faso

Freshwater molluscs play crucial ecological roles and serve as key bio-indicators of aquatic ecosystem health, yet they can also act as vectors of parasitic diseases. This study assessed the taxonomic diversity, temporal dynamics, and environmental drivers of mollusc communities in a large reservoir in Burkina Faso. A total of 13 species were identified—9 gastropods and 4 bivalves—including five medically important species (Biomphalaria pfeiffer, Bilinus forskalii, Bilinus truncatus, Bilinus jousseaumei, and Bilinus senegalensis) and one invasive species, Melanoides tuberculata. Taxonomic composition was dominated by the family Planorbidae, particularly the genus Bulinus. Temporal analysis revealed three phases of community dominance: B. pfeifferi prevailed in cooler months (November 2020–January 2021), M. tuberculata dominated during warmer periods (March–May 2021), while a more balanced assemblage emerged in September 2021.Diversity indices varied seasonally, with Shannon diversity peaking in March and the Simpson index lowest in July, reflecting fluctuations in species evenness. The Canonical Correspondence Analysis indicated that temperature (λ = 0.47) and pH (λ = 0.39) were key environmental gradients shaping community structure. B. truncatus was strongly associated with high temperatures. Alkaline pH favored M. tuberculata and Coelatura aegyptiaca, whereas salinity and conductivity influenced species such as B. forskalii and Ligia natalensis. The co-occurrence of invasive and disease-vector species, combined with their environmental preferences, underscores the need for integrated water and health management. The findings contribute to baseline bio-diversity data and inform risk assessments related to waterborne parasitic diseases, especially in the context of urban agriculture and climate change. Key words: Freshwater molluscs, disease vector, invasive species, biodiversity dynamics.