It is increasingly suggested that deep-sea polymetallic sulphide (PMS) deposits could become an important source of mineral resources. These mining operations will remove the targeted substrate, producing potentially toxic sediment plumes both from the in situ seabed excavation and from the wastewater pumped from surface processing vessels back down to just above the seafloor. However, the extent and nature of ecosystem impacts resulting from these plumes has until now been unclear.
A series of studies carried out by iAtlantic researchers at IMAR/Okeanos University of the Azores set out to determine the extent of the area that would potentially be affected by these plumes, and the nature of the direct impacts on seafloor ecosystems such as cold-water corals. Results have recently been published in three peer-reviewed papers and are summarised in a new science brief, available to download now. The publications forming the basis for this science brief are also available as open access papers.
Key results highlighted in this science brief include the following:
- Modelling studies in the Azores region project that sediment plumes from seafloor polymetallic sulphide (PMS) mining operations may disperse beyond the licensed mining areas, reaching the flanks and summits of nearby topographic features and extending into the bathypelagic, mesopelagic, and epipelagic environments.
- Sediment particles contained within such plumes can have sub-lethal and lethal effects on benthic sessile suspension- and filter-feeding fauna (such as deep-water corals) by impairing feeding and respiration.
- Toxic metals within this suspended sediment – such as copper – bioaccumulate in coral tissues and skeletons. Subsequent coral death may be due to a combination of the toxic and mechanical effects of PMS particles.
- Delayed mortality in corals exposed even to low concentrations of copper in seawater indicates that some coral species may not recover from the effects of PMS mining plumes. Delayed ecosystem impacts must be considered when predicting the effects of environmental disturbances, such as deep-sea mining, on cold-water coral communities.
These results are particularly pertinent and timely as the International Seabed Authority prepares to convene its Council to continue discussions on the ISA’s Draft Regulations on Exploitation of Mineral Resources in the Area – informally known as the Mining Code. This meeting (Kingston, Jamaica, 31 October – 11 November 2022) includes a series of Informal Working Groups that focus on specific aspects of the draft Mining Code, including a group dedicated to The Protection and Preservation of the Marine Environment. Those interested in following negotiations can do so via the ISA’s webcast coverage: https://isa.org.jm/web-tv