Sediment redistribution during simulated benthic disturbance and its implications on deep seabed mining

A benthic disturbance experiment was conducted in the Central Indian Basin to evaluate the possible effects of sediment redistribution on marine ecosystem during deep-sea mining. The analyses of disturbance features on the seafloor and particle resettlement indicate that the most intense impact is created within the experiment site, and some of the resuspended sediments that remain in the near-bottom water after the disturbance are transported away from the site, changing the physico-chemical conditions in the area. Resedimentation is observed on either side of the disturbance zone, with an increase in suspended particles by 300% (from 49 to 150 mg/m(2)/day) during the disturbance and a reduction by 33% (to 95 mg/m(2)/day) immediately after the experiment. Higher collection of particles as well as an increase in organic carbon in seafloor sediments S-SW of the disturbance zone indicates directional migration of suspended material and redeposition in the adjacent areas. The implications of increase in turbidity and sedimentation rates in the near bottom water column due to sediment re-suspension, as well as lateral migration of sediment, on the benthic ecosystem have been discussed. These parameters provide important inputs in ascertaining longterm effects of deep-sea mining. (C) 2001 Elsevier Science Ltd. All rights reserved.