The probable impact of nodule mining on benthic biota was studied by creating a benthic disturbance. During the predisturbance study in the Central Indian Basin, box core samples were analyzed for the distribution, composition and abundance of meiobenthos and macrobenthos. These studies were repeated on sediment samples collected from the same stations of Indian Basin immediately after the disturbance on a 3000m x 200m disturbance track and outside the disturbance track. Characteristic changes in the spatial and vertical distribution of macrobenthos were discernible after the disturbance particularly in disturbance track. The changes showed differential effects of disturbance within and out side the disturbance track. Significant reduction in the vertical distribution was recorded. Similarly the abundance of meiofauna, in particular, nematodes and copepods showed reduction up to 40% in the disturbance track. Density of meiofauna outside the disturbance track showed no significant changes although increases in density at some stations were noticed.
Investigations on the effect of manganese nodule mining in the deep-sea have been undertaken earlier under different programmes such as JET (Japan Deep-sea Impact Experiment), MMAJ (Metal Mining Agency of Japan), DISCOL (Disturbance and R~colonization), BIE (Benthic Impact Experiment) and KODOS (Korean Deep Ocean Studies). A similar programme INDEX (Indian Deep-sea. Experiment) was launched by India in 1996 in the Indian Basin (Anon, 1997). The research included baseline data collection, mining impact experiments and mining impact analysis. Bottom topography observations revealed that disturbance area is generally flat. In order to evaluate the impact of the mining operations a pre-disturbance study was carried out in the same area during May - June 1997. A benthic disturber (Deep-Sea sediment Resuspension system) was used to conduct a disturbance in July - Sept. 1997. This paper reports the effect of suspended sediment on bottQm fauna in the deep-sea disturbance area.