Impact of benthic disturbance on megafauna in Central Indian Basin

Deep-sea photographs and video data were studied to evaluate the effects of benthic disturbance on megafaunal distribution in the Central Indian Basin . Xenophyophores (41 %) and holothurians (30%) are the most abundant taxa, followed by other groups in the area before the disturbance. An overall red uction (32%) in the total megafaunal population after disturbance is direct evidence of the impact on benthic environment. Different groups such as xe nophyophores, sea anemones, shrimps, starfish, brittle stars, holothurians and fish show different degrees of reduction (21-48%) in their numbers, dep ending upon their ability to withstand increased turbidity and sedimentatio n rates due to disturbance. Faunal groups such as protobranch molluscs, polychaete worms, seafans and s quids, observed before the disturbance, were not seen after disturbance, wh ereas populations of some taxa increased after the disturbance. Increased n umbers of mobile taxa could be due to increased levels of organic carbon du e to resedimentation, whereas increase in sessile taxa may partly reflect t he difficulty in distinguishing live from dead specimens. The impact on fau nal assemblages is more severe in the disturbed area than the undisturbed a rea. Our results indicate that monitoring of megafauna can be used effectively t o evaluate the potential impacts of large-scale mining or other disturbance on the seafloor, and may therefore help in developing measures for conserv ation of the benthic environment. (C) 2001 Elsevier Science Ltd. All rights reserved.