Physical impacts on the seabed

Extraction of minerals from the deep sea presents a significant engineering challenge as many potential mining sites are located far from land and at great water depths. The mining methods employed will vary with the character and distribution of the resource: for example, nodules are spread across wide areas of the seabed surface in areas of very deep water, massive sulphides are hosted within sub-seafloor rock, crusts form hard, surficial layers on the flanks of seamounts, and gas hydrates form layers within the seabed sediment.

The likely physical impacts on the deep-sea environment include the widespread distrubance or loss of seafloor habitats, the generation of large plumes of fine particulate matter and the introduction of chemicals - some of which may be potentially toxic to marine life - into the water column. In the case of gas hydrate extraction, destabilisation of the seafloor is also a potential problem. Mining activities may bring cold, nutrient-rich and particle-heavy water from the deep sea to the sea surface, potentially creating significant impact on both the marine environment and atmosphere.

The physical impacts of mining are not just confined to the removal of ore from the deep sea; pre-processing of ore via mobile platforms at sea will generate waste material that may be discharged back into the water column or at the seabed. This waste material may contain substances that are directly toxic to marine life or can chemically alter the marine environment. The release of toxic substances through the extraction of sulphides, nodules and crusts from the seafloor will be unavoidable and its effects difficult to control.

MIDAS scientists will carry out field and laboratory research into the nature and scales of the potential impacts, including: 1) physical impact on the seabed by mining and the creation of mine waste; 2) the potential for catastrophic slope failures from methane hydrate exploitation; 3) the potential effects of particle-laden plumes in the water column and the fate of deep-sea contaminant discharge, and 4) the possible toxic chemicals that might be released by the mining process.