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The epifaunal assemblage was evaluated at three different depths (5, 15 and 25 m) in the inshore waters of Pazhayar, Parangipettai and Cuddalore apart from 5 m depth near SIPCOT covering totally 10 stations (11• 21 N to 11• 42 N; 79• 46 49 E to 79• 52 34 E) in the southeast coast of India, Bay of Bengal. The occurrence of as many as 112 species belonging to 6 groups was recorded. Among these, gastropods constituted the largest component (42.85%) with 48 species. Bivalves came next with the percentage contribution of 24.10% with 27 species. Crustaceans and polychaetes contributed with 16.96% (19 species) and 6.25% (7 species), respectively. Others contributed with 9.82% (11 species). The maximum number of species was recorded in Cuddalore transect (65 species) and the minimum in SIPCOT (20 species). The maximum abundance was recorded in SIPCOT (1363 ind./haul) but the diversity was found to be lower here than in the other stations. The bivalve, Scapharca inaequivalvis was abundant only in this station whereas the large sized polychaetes, Epidiopatra hupferiana monroi and Sternaspis scutata were found only in the Pazhayar transect during all the seasons. Multivariate analyses were done to define assemblages. The total number of species estimated by various extrapolators varied from 112 species to 169.73 species. The cluster analysis revealed the gradual change in species composition with increase in depth. In the principal coordinate analysis (PCO) the first two axes explained 49.8% of the total variability in the case of biota and 98.3% of the total variability in the case of environmental variables. The distance based linear model (DISTLM) was used to find out the relationship between the abundance of epifauna and environmental variables. Depth explained about 23.7% of the variability while temperature and pH explained 17.5 and 10.6%, respectively. The best solution suggested all the nine environmental variables to combinedly explain about 92.49% of the total variability

The levels of heavy metals copper and zinc were found to be high in the Vellar estuary. Therefore their effects on the larval development of the abundant hermit crab Clibanarius longitarsus were studied individually and in combination from hatching till moulting to glaucothoe stage in the laboratory using freshly hatched Artemia nauplii as food. The 96 h LC50 values found with 100 larvae each kept in 10 different concentrations of copper and zinc (350, 300, 250, 200, 150, 100, 50, 25, 10 and 5 ppb) were 50 ppb for copper and 90 ppb for zinc. Based on these 96 h LC50 values, three sublethal concentrations were chosen for the metals copper and zinc at 50%, 25% and 10% levels of the LC50 values. With increase in concentration of the test medium, the survival rate decreased and the time required for the completion of each zoeal stage increased. Copper was found to be more toxic than zinc as the survival rate in copper concentrations was lower than those in zinc concentrations. The survival rate in the mixed concentrations of metals was lower than in individual concentrations.