Habitat Preference and Community Assemblage of Bivalves in the Intertidal Zone

Abstract

This study investigates the ecological dynamics of mollusk communities across four intertidal zones in Capiz. A total of 7,869 individual mollusks representing 11 families were collected from September 2024 to December 2024. Results showed that Veneridae was the most abundant and diverse family across all sites. Marked spatial variation was observed, with Guise recording the highest abundance (≈4,727–4,872 individuals), dominated by Meretrix lyrata, while Lonoy and Culasi exhibited significantly lower abundances due to anthropogenic disturbance and unfavorable environmental conditions. Bungkayaw showed moderate abundance but was constrained by very low dissolved oxygen levels, while Culasi experienced high temperature stress. Diversity indices revealed that Culasi had the highest Shannon diversity (H’ = 1.38), whereas Guise had low diversity despite high abundance, indicating species dominance. Sediment analysis indicated that nutrient-rich substrates with higher organic matter supported greater productivity, while calcium-rich sediments favored shell formation. However, extreme physicochemical conditions such as low dissolved oxygen, high temperature, and low pH negatively affected species distribution and survival. Overall, results demonstrate that mollusk community structure is strongly shaped by the interaction of water quality, sediment characteristics, and human disturbance. The study highlights the sensitivity of intertidal mollusks to environmental changes and emphasizes the need for coastal habitat conservation to maintain biodiversity and ecosystem stability in intertidal zones, especially under increasing anthropogenic pressures.