After heavy disturbance of the deep ocean floor sediment in a manganese nodule field the recolonization of the fauna was monitored in the DISCOL Experimental Area (DEA). Three sets of data, all randomly sampled in the same way, were collected during RV SONNE-cruises SO 61 (DISCOL 1-2, immediately after disturbance), SO 64 (DISCOL 2, 6 months after disturbance) and SO 77 (DISCOL 3, 3 years after disturbance). The results are comparable with the data gained immediately before the disturbance (SO 61, DISCOL 1-1). All faunal taxa were decreased significantly in numbers after the disturbance and, except bacteria, half a year later. Three years after the disturbance mega- and meiofauna numbers were significantly· higher than at the baseline study. This can be a normal situation of recolonization processes. The largescale DISCOL-experiment has presented first results on the recolonization process after anthropogenic disturbance. Nevertheless, during marine mining larger areas will be destroyed by towing the collector device track by track than during the DISCOL experiment.
The actual and planned uses of the deep sea requires the necessity of the protection of the largest environment on earth (Thiel und Schriever, 1993, Thiel, 1995). One of the future uses is the mining of manganese nodules. Low metal prices and the International Law of the Sea are responsible that deep-sea mining will not commence before the second decade of the next century. But already now pre- cautionary research is required to accumulate knowledge about the basic ecological situation in the deep sea to judge about the impact potential of mining (Thiel and Foell, 1993, Thiel, in press). The research project DISCOL was developed on the results of the MESEDA- (Metalliferous Sediments Atlantis II Deep) and the DOMES (Deep Ocean Mining Environmental Study) projects (Thiel und Schriever, 1990, Thiel, 1992).
