10M BIE Revisited: Meiobenthos At the IOM BIE Site 5 Years After the Experimental Disturbance

In July 1995, Interoceanmetal Joint Organization (10M) carried out its Benthic Impact Experiment at an abyssal site located within the 10M pioneer area in the NE Pacific's Clarion-Clipperton Fracture Zone. Meiobenthos, selected as a key biotic variable with which to assess effects of experimental sediment disturbance mimicking that produced by a nodule miner, was sampled immediately before and immediately after the disturbance. The results of that sampling yielded evidence of purported seasonal effects on the sea floor, produced by sedimentation of phytodetritus. The original 10M Benthic Impact Experiment (10M BIE) test location was visited for the third time in June 2000 and meiobenthos samples were collected from 9 stations, representing the former control, disturbed, and resedimentation areas of the test site. No phytodetritus deposition on the seafloor was observed. Results of the three series of sampling the abyssal meiobenthos within the 10M BIE test site (1995, 1997, and 2000) showed the control area to have been affected by some processes occurring in between the temporally widely spaced sampling events. The meiobenthos in the impacted zone, moderately disturbed, was greatly enhanced as a result of the 1997 phytodetritus input and the enhancement persisted in time. The meiobenthic communities in the area outside the impacted zone, which was originally affected by the redeposition of sediment suspended during the disturbance, showed a pronounced enhancement caused by the 1997 phytodetritus sedimentation. In the 10M 2000 series, the abundance of those communities was observed to revert to the level shown by the control area of that series.