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.

Seasonal variations in physico-chemical characteristics of water, sediment and soil texture in arid zone mangroves of Kachchh-Gujarat.

The present study was carried out to determine the physicochemical characteristics of water and sediment and the textural aspects of sediments in western mangroves of Kachchh-Gujarat, west coast of India, for a period of two years during 1999-2000. Surface water and sediment temperatures varied from 17 degrees C to 37 degrees C and from 18.4 degrees C to 37 degrees C respectively. Tidal amplitude varied from 0.03 m to 3.78 m. Salinity varied from 34.0 to 44 per thousand and the pH in water and sediment ranged between 7.0 and 8.9 and 6.29 and 8.45 respectively. Variation in dissolved oxygen content was from 3.42 to 5.85 ml l(-1). Concentrations of nutrients viz. nitrate (0.23 to 7.26 microM), nitrite (0.04 to 0.87 microM), phosphate (0.13 to 3.12 microM) and reactive silicate (4.23 to 19.02 microM) also varied independently Total organic carbon varied from 0.29% to 2.56% and the total inorganic phosphorus ranged between 0.12 mg g(-1) and 1.97 mg g(-1). Total nitrogen varied from 0.02 mg g(-1) to 1.95 mg g(-1). Sediment textures ranges in terms of % of sand, clay and silt were: 0.26-19.2; 7.6-47 and 47-87.4 respectively in all the 3 stations. The nature of soil texture is characterized by the abundance of silty loam, silty clay and silty clay loam.

Abundance and seasonal variations of phytoplankton in the creek waters of western mangrove of Kachchh-Gujarat.

The phytoplankton was assessed quantitatively and qualitatively in regard to their abundance in creek waters at three sites along the western mangrove of Kachchh. In total one hundred and four species of phytoplankton were identified. Among them 82 species diatoms (Bacillariophyceae), 16 species dinoflagellates (Dinophyceae), 3 species blue greens (Cyanophyceae) and 2 species were green algae. The density in all the three sites varied from 94,166.67 to 2,44,500 cells l(-1). The salinity ranged from 36 to 44 per thousand, temperature 17 to 35 degrees C and pH ranged from 7 to 8.9 respectively. These semi arid zone mangrove creek area having high densities were recorded during monsoon and early winter season.