Spatial variation of aerobic culturable heterotrophic bacterial population in sediments of the continental slope of western Bay of Bengal

Abstract

Culturable total heterotrophic bacterial populations from the sediments of the continental slope in the depth zone of 214-1000 m in western side of Bay of Bengal were enumerated. The physico-chemical parameters of overlying water and sediment were also recorded and correlated with the bacterial population. The sediment bacterial population ranged from 0.42 to 37.38 x 10⁴ CFU g⁻¹ (dry wt). The top section of the sediment (0-3 cm) had higher bacterial abundance in the range of 1.01-37.98 x 10⁴ CFU g⁻¹(dry wt) and the vertical bacterial population decreased through the middle (3-6 cm; 0.15-37.21 x 10⁴ CFU g⁻¹ (dry wt) to the bottom section (6-9 cm; 0.10-36.92 x 10⁴ CFU g⁻¹ (dry wt). The total heterotrophic bacterial population correlated significantly with sediment water (P<0.02), total organic carbon (P<0.02) and clay fraction (P<0.01). Vertical distribution of bacterial population showed regular trend of decreasing with increasing sediment depth and the higher population was observed in the northern transects. Lower counts of bacterial population may be attributed to the small-scale patchiness and presence of dormant or slow growing bacteria in the sediments of Bay of Bengal.