Response of deep-sea macrobenthos to a small-scale environmental disturbance

To assess the possible effect of nodule mining on deep-sea environment, the Indian deep-sea environment experiment (INDEX) was undertaken in the Indian Basin. The present investigation is a part of the disturbance and recolonization study. Pre- and post-disturbance sediment samples were collected from 21 stations between 10° 01′–10° 03′ S and 75° 59′–76° 02′ E at water depths of 5300–5350 m to assess the effect of benthic disturbance. There was a significant change in the composition and biomass of macrofauna after the disturbance. Post-disturbance vertical profiles indicated a 63% reduction in the numerical count in the top 0–2-cm layer and high aggregation of macrofauna in deeper (5–10-cm) sediment layer. The impact of the disturbance was severe, as the mean biomass of macrofauna was significantly reduced in the disturbed area, probably due to the displacement and /or mortality caused by the benthic disturber.