Spatial Patterns in Diversity and Distribution of Benthic Molluscs in a Weak Tidal Tropical Lagoon

Abstract

Spatial patterns in diversity and distribution of benthic molluscs in a weak tidal tropical lagoon in south-west Nigeria were investigated from samples collected in eight study stations distributed along the stretch of the lagoon for two consecutive years. The study also investigated selected environmental conditions of overlying water and sediment of the lagoon to establish the roles played by environmental variables. There was a significant variation (p < 0.05) in salinity values along the study stretch which was predicated on the existing gradient in salinity of the lagoon. Higher values of mud and Total organic content (TOC) of sediment occurred in upstream compared to values observed in downstream stations. Mollusc communities were significantly influenced by the spatial gradient in salinity and variability in sediment parameters. The downstream stations had brackish conditions, while the upstream stations were typically freshwater, leading to differences in the composition and abundance of molluscs. The downstream stations recorded higher density and diversity of mollusc compared to upstream stations. Our results suggest that benthic molluscs in Epe Lagoon show spatial patterns related to differences in environmental parameters.