SPATIO-TEMPORAL STRUCTURE OF MOLLUSC COMMUNITIES IN LAKE ZIENKOLO: INFLUENCE OF PHYSICOCHEMICAL GRADIENTS (NORTHERN CÔTE D'IVOIRE)

Abstract

Aquatic molluscs play an essential role in the functioning of lakes and are commonly used as indicators of water quality. However, their diversity remains little studied in the reservoirs of northern Côte d'Ivoire. This study characterizes the composition and spatio-temporal structure of these communities in Lake Zienkolo (Korhogo). It also evaluates their relationships with the physico-chemical parameters of the water. Sampling was carried out monthly from January to December 2025 at three stations, using a hand net and a Van Veen grab. The collected specimens were then identified in the laboratory. The physicochemical parameters were measured in situ. In total, 15 taxa belonging to 8 families, 5 orders, and 2 classes were identified, with a clear dominance of gastropods (98.65%). The Shannon index (1.25–2.03) and Pielou’s evenness (0.52–0.84) varied between stations. Monthly variability in abundance and taxonomic richness was also observed during the sampling period. The structural parameters of the communities (abundance, frequency of occurrence, and taxonomic richness) were used to characterize the structure of mollusc communities. The redundancy analysis (RDA) revealed that temperature and dissolved oxygen were the physico-chemical parameters most strongly associated with the distribution of molluscs in Lake Zienkolo. These results highlight the role of environmental factors in structuring mollusc communities and underscore the importance of regular monitoring of the physico-chemical parameters of Lake Zienkolo.