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.