Mangrove snail diversity as a tool for biomonitoring the mangrove based coastal habitats

Mangrove forests play a pivotal role in supporting mangrove associated snails by offering essential functions such as breeding grounds, nursery areas, food sources, and protection from predators. They play a particularly important role in nutrient cycling within mangrove ecosystems. Despite their significance, there has been a lack of studies conducted in Sri Lanka to explore the diversity of mangrove snails. Thus, the objective of this study was to assess the significance of snail species diversity in mangrove ecosystems on the western coast of Kandakuliya, Kalpitiya, Sri Lanka. Five sites were selected using purposive sampling technique at each location, and the sampling was conducted during low tide in daylight hours in both the non-rainy (February) and rainy (September) seasons of 2023. Transects (30 m) were established at each location, with six 1 m² quadrats placed along each transect at 5 m intervals as replicates. The study identified six snail species from three families, with Pirenella cingulata being the most widely distributed across all sites and exhibiting the highest abundance at site 3. Temporally, Pirenella cingulata displayed the highest number of individuals in both the rainy and dry seasons. Diversity indices indicated the highest values at site 1 for the Shannon-Wiener index (H´=1.14), site 5 for Pielou's evenness index (J=0.96), and site 1 for Simpson's diversity index (D=0.67). Pirenella cingulata recorded the highest total abundance at 85,840 individuals. Variations in these findings may be attributed to water quality factors such as temperature and dissolved oxygen, as well as mangrove dominance and climatic conditions. The study suggests that incorporation of environmental parameters could support to draw a more comprehensive understanding of the correlation of dynamics of environmental variables for mangrove snail population changes.