Macrofaunal community structure in the Western Indian Continental Margin including

Patterns of macrofaunal distribution were studied along the western Indian continental margin to distinguish the role of habitat heterogeneity in generating and maintaining community structure. A transect perpendicular to the coast at 140 N latitude was selected for seabed sampling. Eight stations were sampled in the depth range 34 m to 2546 m and characterized with respect to macrofaunal composition, abundance, biomass, diversity and feeding type. The sediments in the shelf region (34, 48, 100 m) and upper slope (525 m) were characterized by silty and sandy facies, whereas the mid slope (1001 m), lower slope (1524 m) and basin (2001, 2546 m) consisted of clayey silts. The highest value of sediment chlorophyll-a (Chl-a) and total organic carbon (Corg) were recorded from the mid slope areas. Faunal abundance and biomass increased from the shallow to deeper depths in the shelf region, and decreased in the slope region (525-1001 m) due to the reduced bottom-water oxygen. The community parameters showed an overall increase in both the lower slope and basin areas. A total of 81 macro-invertebrate species belonging to 5 major groups represented the macrofauna of the area. Polychaeta was the major group at all depths. Among polychaete families, species of the Spionidae, particularly Prionospio pinnata, predominated at the oxygen minimum zone (OMZ) core and Cossurida