The Environmental Impact Research on Marine Ecosystem for Deepsea Mining has been conducted from 1998 to 2002 for establishing quantitative methods to estimate environmental impacts on marine ecosystem on deep seabed likely to be caused by mining operations for mineral resources. This research program was composed of the baseline study, the artificial impact experiment by a scraper simulating the mining operation, the three-year monitoring after the impact, and the development of numerical simulation model. The results obtained through this program are very important not only for establishing the methods but also for gathering fundamental information about the environmental baseline of cobalt-rich manganese crust distribution area.
Manganese nodules and cobalt-rich manganese deposits, found on the deep-sea floor and the seamounts in the Pacific, are expected to be important supply sources for copper, nickel, cobalt, and manganese in the next generation (Mero, 1965; Cronan, 1980; Halbach, 1982; Manheim, 1985). It is impossible to avoid recovering deep-sea sediments while collecting manganese nodules, because the nodules are half buried in the deep-sea sediment layer. Separating the sediments in the mining system as quickly as possible would improve the transportation efficiency of the lift mechanism. Because this re-deposition will occur faster than natural sediment deposition rate, from tens of thousands to millions of times, it may cause a significant influence on the benthic ecosystem of the seafloor. In addition, wherever the nodule miner or collector will be used, sediment layers on the tracks will be destroyed to a considerable depth, and, moreover, the ecosystem there will be destroyed immediately. Understanding the extent of these benthic environmental impacts is important, because the deep ocean benthic ecosystem recovers very slowly after it is damaged, and measures to counter such damage must be taken (Thiel et al, 1991).
