Effects of physical disturbance on the cold-water megafaunal communities of the Faroe–Shetland Channel

Abstract

The response of a deep, cold-water benthic community to physical disturbance from offshore drilling was investigated using Remotely Operated Vehicle (ROV) video in the Faroe–Shetland Channel. This study presents a novel method for characterising changes in the ecosystem function of deep-water benthic megafaunal communities in response to physical disturbance. Ecosystem function is investigated using a range of community parameters, particularly abundance and diversity. High levels of physical disturbance, characterised by smothering of the seabed within a radius of 50 to 120 m around the drilling site, resulted in significant but variable reductions in megafaunal abundance (up to 92.3%). Reductions in diversity, particularly in species richness, were apparent between disturbed (Mao Tao estimated species richness of ES(500) = 12.9) and undisturbed areas (ES(500) = 20.6). The implications of selective removal of taxa on ecosystem function and recovery are discussed. Low level disturbance had comparatively little effect on the megafaunal communities; the effects varied in nature depending on motility and functional group (e.g. motile scavenger abundances were maximal at intermediate distances from disturbance). We conclude by comparing the functioning of the ecosystem under different regimes of disturbance and discuss implications for recovery of disturbed deep-sea habitats.