Abundance and Diversity of Intertidal Molluscs along the Coastline of Lagos

Intertidal molluscs play important roles in coastal ecosystems as filter feeders, grazers, and prey items for higher trophic levels, and their community structure reflects environmental quality. This study examined the abundance, species diversity, and zonation patterns of intertidal molluscs along the rocky and sandy shorelines of the Lagos coastline, South West Nigeria. Sampling was conducted at three intertidal sites using quadrat sampling at high, mid, and low tidal zones during three seasons. Molluscs were collected, identified to species level, and counted within 50 by 50 centimetre quadrats. Community diversity metrics were calculated, and environmental variables including wave exposure, substrate type, moisture, and surface temperature were recorded. A total of 28 molluscan species belonging to three classes were identified: Gastropoda (17 species), Bivalvia (9 species), and Polyplacophora (2 species). Gastropods dominated all tidal zones. Species richness and abundance increased from the high tide zone to the low tide zone at all sites. Nerita senegalensis and Thais haemastoma were the most widespread gastropod species. Bivalve abundance was highest at the low tidal zone of sandy shores. Site comparison revealed significantly lower diversity at the site adjacent to the Lagos port, likely attributable to chronic disturbance and substrate modification. The study provides a comprehensive inventory of intertidal molluscs in Lagos and recommends the establishment of intertidal monitoring plots as part of coastal environmental surveillance programmes. Keywords: intertidal molluscs, species diversity, tidal zonation, Lagos coastline, gastropods.