Summary and Keywords
Deep-sea mining pertains to underwater minerals such as polymetallic nodules, ferromanganese crusts, and hydrothermal sulfides that are considered as alternative sources for metals such as Cu, Ni, Co, Pb, Zn, Cd, Mn, Fe, and rare earths that could be exploited in the future by developing suitable technologies. Many of these deposits occur in international waters in which several “contractors” have staked claims over large tracts of the seafloor under the United Nations Law of the Sea, whereas attempts are also being made to develop the deposits within the Exclusive Economic Zone of some countries. However, several concerns have emerged over potential impacts of mining these deposits, leading to regulations being framed as well as measures being devised for conserving the marine ecosystems.
The likely sources of environmental impact of deep-sea mining include those from the mining ship where handling of ore, machinery, oil will take place; the lift mechanism that would transfer the minerals from the sea bottom to the surface through the entire water column; as well as the mining machine that would actually scrape the seafloor for minerals. This article describes the likely impacts that could be caused due to mining of three different types of deep-sea minerals, viz. polymetallic nodules, hydrothermal sulfides and ferromanganese crusts. It further shows the estimation of impacts in terms of mining area, volume and weight of associated substrates; and goes on to suggest mitigation measures to minimize the potential impacts of deep-sea mining. Finally, the national and international environmental regulations for deep-sea mining have been discussed.
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