Temporal Variations of Micro Benthic Assemblage in the Sangu River Estuary, Bangladesh

Abstract

Temporal distribution of shellfish assemblages, together with water quality data, was conducted in the Sangu river estuary of Bangladesh to assess shellfish's diversity index during winter, pre-monsoon, and monsoon and post-monsoon periods. A total of 15 species of shellfish belonging to 9 families was recorded of which  Acetes  sp. (25.18%),  Matuta victor  (18.77%),  Exopalaemon styliferus  (18.28%),  Parapenaeopsis sculptilis  (14.22%) were found to be most dominant species during the study period. Significant temporal differences were observed for water temperature, salinity, water transparency, P H  and DO. The diversity indices, Shannon-Wiener diversity index and Margalef richness index showed a significant difference among the seasons while no significant difference was observed in the Pielou’s evenness index and Simpson dominance index. The analysis of similarity (ANOSIM) was used to test for significant differences in species assemblages between sampling seasons. At the similarity of 74.8%, three groups were attained while winter and pre-monsoon showed separate clustering from other groups. The Non-metric Multidimensional Scaling (nMDS) showed 50% similarity in all seasons based on Bray-Curtis similarity matrix. The CCA ordination indicated that temperature was the most important environmental parameter shaping the shellfish assemblage structure.