Abundance, Distribution and Diversity of Macrobenthos in Chittagong Coast Bangladesh

Macrobenthos are an essential element of marine and coastal ecosystems. This study intends to examine the taxonomic seasonal structure of macrobenthos species and determine the physicochemical properties of sediments to understand their role in influencing macrobenthos communities in the coast of Chittagong, Bangladesh. A total of 66 species belonging to 30 families and 10 classes were recorded in the study areas. Their density was observed to be remarkably higher in the dry season, with major representation by polychaetes, especially Capitellidae and Nereididae. Capitellidae showed maximum densities at Salimpur Mudflat (787.04 ind. m−²) and Salimpur Salt-marsh (625.00 ind. m−²) during the dry season, while an exceptionally high peak was recorded at Salimpur Salt-marsh in the wet season (1180.55 ind m−²). Capitellidae remained dominant during the wet season. The values of biodiversity indices were higher in the dry season compare to the wet season in most of the sampling station during the study period. According to habitat their density was found to be higher in mudflat areas, especially in Salimpur, than in salt-marsh areas. Sediment properties showed noticeable seasonal variations. Electric conductivity, organic matters, and grain sizes were higher in the dry season sediments of mudflat areas, whereas sediments of salt-marsh areas were dominated by sands. It was revealed that macrobenthos density positively correlated with electric conductivity (r = 0.77), silt (r = 0.62), and clay (r = 0.45) contents, and strongly negatively correlated with sand contents (r = −0.79). Regression analysis also confirmed that sand percentage (R² = 0.56) with p = 0.048 and Electric Conductivity (R² = 0.49) with p = 0.053 are major governing factors of their density.