Responses of Deep-Sea Meiobenthic Communities to Sediment Disturbance Simulating Effects of Polymetallic Nodule Mining



During a benthic impact experiment (BIE) carried out during 1995–1997 by the Interoceanmetal Joint Organization (IOM) at an abyssal site in the North-East Pacific, sediment disturbance mimicking that resulting from polymetallic nodule extraction was created with a specialised device (the Benthic Disturber). The effects of the disturbance on meiobenthic communities were assessed immediately after disturbance and 22 months later. A reduction in meiobenthos abundance, observed immediately following impact, was not significant; neither were changes in composition of the meiobenthos which was dominated by nematodes and harpacticoids. The lack of any significant numerical response is probably accounted for by the moderate degree of disturbance in this study, compared with other BIE-type experiments. On the other hand, statistically significant changes in both meiofauna abundance and vertical distribution profiles in the changed sediment within the Disturber tracks were recorded. After 22 months, a significant increase in overall meiobenthos abundance was detected in that part of the test site affected by increased resuspended sediment settlement and receiving natural phytodetrital inputs. Certain taxon-specific responses on the part of nematodes and harpacticoids were noted both immediately after the disturbance and 22 months later. They were explained by the effects of sediment physical reworking and responses to phytodetrital enrichment. The results presented should aid in developing experimental designs, on both temporal and spatial scales, of future deep-sea tests aimed at assessing the scale and consequences of man-made impacts.