Role of environmental heterogeneity in structuring the macrobenthic community in a tropical sandy beach,west coast of India

In most ecosystems, community structure emerges as a result of the complex interaction between biotic and environmental variables. Sandy beaches connected to adjacent ecosystem like estuaries/creeks provide an opportunity to understand the role of the environment on the community. Kalbadevi beach along the central west coast of India, invaded by creeks at the northern and southern ends, provides an opportunity to investigate the role of environmental heterogeneity in structuring the intertidal macrofaunal communities. Further, the annual tropical rainfall brings about drastic changes in the environmental parameters. Seasonal survey was carried out at 10 transects covering the entire ~5-km beach of Kalbadevi for environmental and macrofaunal studies. We quantified the abundance, biomass, assemblage structure and distribution of macrofauna at different spatio-temporal scales. The univariate and multivariate analyses showed significant spatio-temporal variability in the biotic and abiotic variables. BIOENV analyses showed the best correlation with OC, phaeopigment and grain size. High abundance of macrofauna in the north and south was due to food availability, influenced by the creek. The low abundance during monsoon and subsequent increase in the post-monsoon can be attributed to annual spawning and recruitment of tropical fauna. Therefore, the present research suggests that the other environmental variables also play an important role in structuring the macrofauna of sandy beach. This supports our hypothesis that environmental heterogeneity influences the structuring of macrofaunal community.