The ecology of two sandy beaches in south west India. I. Seasonal changes in physical and chemical factors,and in the macrofauna

Changes during one year in the fauna of two beaches in south India are described in relation to the nutrient content of the water and sand, and the physical changes brought about by the south-west monsoon. At both beaches, the most stable conditions were reached in the pre-monsoon months when the greatest number of species occurred and when there was marked zonation. During the monsoon, erosion took place and only actively migrating species remained to form a permanent element of the beach fauna. Data on population density and biomass indicate markedly seasonal recruitment and rapid growth of individual species, most of which are suspension feeders.