Hydrobiological studies in the gradient zone of the Vellar estuary. 4. Benthic fauna

Abstract

Benthic fauna in relation to some physico-chemical parameters and sediment composition was studied for a period of two years. The fauna comprised of polychaetes, bivalves, gastropods, crustaceans and other groups such as planarians, polyclads and phoronids. Among 47 species belonging to the above groups, 21 belonged to polychaetes, 4 to gastropods, 7 to bivalves, 9 to crustaceans and 6 to other groups. Among these, polychaetes predominated both in species composition and abundance. The total benthic population density varied from 0 to 900 Nos/m2. There was no significant variation in the population density between tides. Among the different environmental parameters studied, salinity and sediment composition appear to play an important role in the spatial and temporal variations of benthic population. A significant negative relationship was obtained between sand and benthic fauna while clay showed positive relationship. A complete change in the sediment composition and the dominance of different groups of benthic fauna was observed in 1978