Intertidal Macrobenthic Fauna of the Karnafuli Estuary: Relations with Environmental Variables

This study describes the influence of 19 hydropedological factors on macrobenthic faunal assemblages of the Karnafuli estuary, Bangladesh during the period from September, 2011 to August, 2012. A total of 33 macrobenthic species/taxa belonging to annelids, molluscs, arthropods and other minor phyla were recorded. Spearman rank correlation (using BIO-ENV procedure included in PRIMER, V.6) showed significant correlation between macrobenthic faunal assemblages and hydropedological variables. Dissolved oxygen showed the highest correlation (r=0.678) with macrobenthic faunal community. Soil particle density, bulk density, porosity, soil water salinity, soil PO -P, soil pH and total suspended solids of water were identified as 4 the best environmental variables that influenced the macrobenthic faunal assemblages at different range of rank correlations (r=0.442 to 0.537). The most influential factors predicting the variations of total number of individuals recorded in different sampling seasons was dissolved oxygen. Species richness of macrobenthic community was positively (p<0.05) influenced by dissolved oxygen and percentage of silt while it was negatively (p<0.05) influenced by percentage of sand and particle density. Dissolved oxygen showed higher contribution to explain the variance in species diversity in the present observations at 1% level of significance. The abundance of the most dominant molluscan fauna Cerithidea cingulata was significantly (p<0.05) influenced water salinity and bulk density of soil. The relatively of more important factor that could be able to positively influence the most abundant species Capitella sp. at a significant level of p<0.01 was soil pH while the abundance of Capitella sp. was negatively influenced by percentage of silt and positively influenced by bulk density at 5% level of significance.