Impacts on deep-sea ecosystems

The extraction of deep-sea mineral resources will likely result in extensive habitat destruction, affecting not only the fauna living in or on the seafloor, but also those species that depend on benthic organisms for food and services.

The sediment plumes likely to be generated by mining could pose a serious threat, potentially spreading toxins, pollutants and acidic waters across wide areas of the ocean. Suspension feeders such as corals, bivalves and sponges may be smothered and the life cycles and larval migration of species may be affected. Extensive phytoplankton blooms could be triggered when cold, nutrient-rich water is brought from the deep up to the sea surface. Conversely, the fine particulate matter within a plume may depress primary production, disrupting the marine food chain.

Little is known about the tolerance and adaptability of marine organisms to such disturbance, and the ecotoxicological risks are complex and poorly understood. However, we do know that these ecosystems are complex, biodiverse and  can include very long-lived species. How will disturbance affect reproduction, dispersal, ecosystem functioning, genetic connectivity and diversity? How far afield will the impacts be felt? Can an ecosystem recover from disturbance, and how quickly? Is there a threshold beyond which recovery is impossible?

At present our scientific knowledge of the distribution of deep-sea ecosystems, their interconnections and resilience to disturbance is insufficient to answer these questions. MIDAS will undertake a series of field campaigns and laboratory experiments to gather data and evidence to address some of these unknowns. Field areas include potential mining sites such as active hydrothermal vents at mid-ocean ridges and nodule mining areas in the Pacific Ocean.

MIDAS will investigate areas of past seabed disturbance such as those used for test mining of nodules over 25 years ago at the DISCOL site in the Peru Basin, sites of mine waste disposal in fjords and coastal areas, and areas of natural disturbance such as recent submarine volcanic eruption sites in the Canary Islands.

Data will be collected on the geographic distribution and genetic connectivity of key species, the effects of direct physical disturbance and sediment smothering on ecosystem biodiversity, functioning and services, and the response of various taxa during exposure to mining-related toxins under deep-sea conditions. Experiments and observations will cover a range of spatial scales, and will consider the direct footprint effects as well as the far-field and long-term effects of disturbance on marine ecosystems.