Assessment of soft bottom polychaete diversity in Thondi, Palk bay, India.

Polychaete assemblages are relatively poorly known in comparison to other components from Indian waters. In the present study, the spatial and seasonal distributions of polychaetes were investigated in the Thondi coastal area. Polychaete assemblage structure seems to be influenced by environmental parameters, such as temperature, salinity, pH, dissolved oxygen and total organic carbon. A total of 34 polychaete species were found, of which 26 species were in station I while 22 species in station II. There was a pronounced variation in diversity of polychaetes between the studied sites. Among the families maximum percentage of species constituted by Glyceridae (12%) and minimum Owenidae (4%) at station I and in station II, the Eunicidae (14%) was maximum and Pisinidae as (4 %) minimum. The population density varied from 1456 to 2456 no m-2 in station I; 2120 to 4424 in station II and diversity index varied from 1.96 to 2.48 in station I; 2.01 to 2.53 in station II. Species richness varied from 1.21 to 1.65 in station I; 1.36 to 1.69 in station II and evenness index varied from 0.9 to 0.97 in station I; 0.91 to 0.98 in station II. BIO-ENV analysis showed that salinity, TOC and temperature as the key variables in influencing the faunal distribution.

Spatial and temporal variations in phytoplankton in coral reef and seagrass ecosystems of the Palk Bay, southeast coast of India.

Spatial and temporal behavior of distribution of phytoplankton of the coral reef and seagrass environment of the Palk Bay was studied during April 2002 to March 2003. A total of 133 species of phytoplankton was recorded during the study period, of which, 98 species belong to Bacillariophyceae, 15 species belong to Dinophyceae, 12 species belong to Cyanophyceae and 8 species belong to Chlorophyceae. Diatoms (57.14 to 94.10%) contributed more towards the percentage composition of different groups of phytoplankton at the two stations, followed by dinoflagellates (3.12 to 28.57%), blue-greens (2.43 to 12.5%) and greens (3.7 to 7.69%). Higher phytoplankton population density was recorded during the summer season at both stations (St.1. 62,000 cells l-1 and St.2. 55,000 cells l-1). Coral reef environment was two-fold more productive (2.10-130.21 mg C m-3 hr-1) than the seagrass environment (3.30 - 85.56 mg C m-3 hr -1). Chlorophyll ‘a’ concentration showed higher values at station 1, corresponding to the higher phytoplankton population density recorded at this station along with primary productivity.