Immediate response of meio and macrobenthos to disturbance caused by a benthic disturber

Abstract

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 colleced 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. While a 68% decrease in the numerical abundance was noticed inside the track, outside stations were either not influenced or marginal increase in the numerical count was noticed. Organic carbon and nitrogen content of the sediment confirm the numerical abundance on the track, outside the track and along the depth up to 10-cm sediment column. 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.