Biodiversity of intertidal mollusks in Surigao City, Philippines

Abstract

Intertidal zones are crucial ecological interfaces, but there is a lack of comprehensive studies on mollusk communities in Surigao City, Philippines. This research aimed to assess intertidal mollusk profiles, including species density, diversity, evenness, and richness, addressing a knowledge gap in regional mollusk biodiversity. Using a belt transect quadrat method in three sampling areas during 2021, the study employed a descriptive correlation design to investigate relationships between mollusk profiles and seawater physico-chemical parameters (conductivity, dissolved oxygen, pH, salinity, and temperature). In Surigao City's Day-asan, Hikdop Island, and Sibale, 44 gastropod species (19 families) and 11 bivalve species (9 families) were identified. Conidae and Strombidae families dominated. Average seawater parameters were conductivity 51.33, dissolved oxygen 7.45, pH 7.84, salinity 32, and temperature 28.52. Day-asan exhibited the highest species count (49), followed by Hikdop Island (42) and Sibale Island (37). Hikdop Island had the highest species density and evenness, Day-asan had the highest species diversity index, and Sibale Island had the highest species richness. Mollusk profiles showed no significant differences between sampling areas, and a strong negative correlation between pH and species evenness was observed. Surigao City displayed diverse mollusk biodiversity, but a declining trend in diversity indices was noted. This study fills a critical knowledge gap in understanding mollusk community dynamics, providing essential baseline data for future conservation and management strategies in the region, while also shedding light on the impact of environmental factors on intertidal mollusk populations in Surigao City.