Spatial and Temporal Environmental Variable Affect of the Lower Meghna River & Its Estuary on Macrobenthic Fauna, Bangladesh

Present study was conducted in the lower Meghna River and its Estuary at Chandpur, Barisal, Bhola, Hatiya and Sandwip during monsoon and post-monsoon season. A total of 17 major taxa were identified of which 10 and 15 were recorded during monsoon and post-monsoon season respectively. Macrobenthos abundance was comparatively greater during post-monsoon than monsoon. The water at lower Meghna was slightly acidic in both seasons. Salinity, soil pH and water temperature were found to be responsible for the variations in benthos assemblage (p<0.05). Canonical Corresponding Analysis (CCA) also indicated that most of the macrobenthos had close dependency to salinity, water temperature, soil pH, organic carbon and organic matter both in monsoon and post-monsoon. Benthos diversity (H') did not show much temporal variation (0.92±0.52 and 0.85±0.40 for the monsoon and post-monsoon seasons respectively). The highest macrobenthos diversity (H') was 1.53 at Bhola and the lowest was 0.29 at Chandpur both during the monsoon season. The macrobenthos evenness (J') also showed less variation between seasons (0.64±0.32 and 0.51±0.26 during monsoon and post-monsoon respectively). The maximum evenness value was found at Sandwip (0.95) during the monsoon season whereas the minimum value was at Barisal (0.20) during the post-monsoon.