Microbial biomass and organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer ar ea. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10(10)-10(11) cells per g(-1) dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cares indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of fetal counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their. stable nature and suggests that they can serve as useful parameters for long-term monitoring of rite ar ea after the benthic disturbance. Further studies on temporal variability in this legion would not only verify the observed nor ms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.