Deep-Sea Mining: A New Frontier of Ocean Disturbance

What is it?

The deep-sea has long been susceptible to human-caused disturbances of various identities, such as: plastic pollution, climate change, oil exploitation, and overfishing. Unfortunately, a different disturbance type is on the horizon named Deep-Sea Mining. These operations are designed to extract Manganese nodules from the seabed, which are generally located within 4,000 – 6,000 meters depth. These nodules contain valuable minerals that are necessary for the development of lithium-ion batteries, such as: cobalt, nickel, and manganese. Historically, cobalt has been mined from the Republic of Congo where greater than 70% of the “mineable” cobalt is believed to be. However, current cobalt mining operations are surrounded by human rights issues and located in an unstable geopolitical climate. The current demand for nickel is greater than the supply, as pointed out by Tesla CEO, Elon Musk. In order to mine the deep sea in the high seas, approval must be granted by the International Seabed Authority, but within national waters, nations can sell off rights to land use similar to mining on terrestrial property. So, the economic reasons exist for deep-sea mining operations to commence and it may be possible for corporations to do so, but at what cost?

Impacts on the benthic environment

A deep-sea mining operation is essentially a giant lawnmower that will overturn the top few centimeters of the sediment in the abyssal plain (area of the deep seabed that is generally flat). In abyssal plain, any crack, mound of sediment, rock, or other animals, can be seen as essential habitat for a species. Once this ecosystem is disturbed, it does not regrow rapidly. Manganese nodules, which should be considered as essential habitat, only grow ~10 millimeters per million years. The removal of structure or reshaping of the benthos (bottom of the ocean) can have major negative impacts on food web structure and biodiversity of these ecosystems. The deep-benthic environment is incredibly food-limited, meaning that disruptions to the animals that live in and on the sediment could drastically affect the rest of the food web. Furthermore, there is likely a connection between the deep-benthic and deep-pelagic (water column deeper than 200 meters) environments, which could extend the direct effects of deep-sea mining further.

Impacts on the pelagic zone

Once the machine stirs up the sediment and collects the nodules, the material will be moved to a ship at the surface. The mining operation and the transport of material through a pipe will cause vibrations and create noise in the water column. Marine mammals are susceptible to human-caused noise in the environment, as it can disorient them to the point where they leave their natural environments or beach themselves. These pipes will not just be carrying manganese nodules, but also sediment and other pieces of unwanted material. This excess supply will have to go somewhere, and the current plan is over the side of the ship. In practice, this will create a plume in the open-ocean water column. In a previous blog post, I discussed diel vertical migration and how it is an important day/night process in the open ocean. This environment is extremely light-driven and any cloud of sediment could hypothetically affect animal behavior and the ability for predators to successfully find food.

Once this sediment is in the water column, it is at the mercy of the ocean currents. The plume created by tossing sediment overboard would therefore be pushed around the oceans and have a larger impact than the immediate area surrounding the mining operation. A great example of this is what happened with the oil plume after the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. This sediment will also contain heavy metals, which are becoming more of a concern in marine environments, particularly when they end up as highly concentrated in human food. The combination of disruptions to animal behavior and inclusion of heavy metals in areas other than what will be directly sold in land-use rights indicates that deep-sea mining will impact the deep-pelagic zone as well as the deep-benthos.

Good news

Although there is not a ban on deep-sea mining in the high seas, there are some recent bright spots by independent nations. Indonesia, the world’s leading nickel producer, came forth and said they would not grant any more deep-sea mining permits for Indonesian waters. This is not a ban on already sold leases but is a step in the right direction for a potentially major contributor to deep-sea mining operations. Also noteworthy is that this action by the Indonesian government comes from pressure by a grassroots campaign to halt mining operations. In a nearby country, the Australian Northern Territory has once again placed a moratorium on deep-sea mining operations in the territorial waters. Eva Lawler, the environment minister for the territory, said “Our natural environment is one of our best assets and it’s a large part of what makes living in the territory so special”. Moving forward, we can hope that more countries follow the lead to limit or ban deep-sea mining practices in their national jurisdictions and put pressure on stopping mining in the high seas.

Suggested Reading

Dover, C.L. Van, 2011. Tighten Regulations on deep-sea mining. Nature 470, 31–33. https://doi.org/10.1038/470031a

Drazen, J.C., Smith, C.R., Gjerde, K.M., Haddock, S.H.D., Carter, G.S., Anela Choy, C., Clark, M.R., Dutrieux, P., Goetze, E., Hauton, C., Hatta, M., Anthony Koslow, J., Leitner, A.B., Pacini, A., Perelman, J.N., Peacock, T., Sutton, T.T., Watling, L., Yamamoto, H., 2020. Midwater ecosystems must be considered when evaluating environmental risks of deep-sea mining. Proc Natl Acad Sci U S A 117, 17455–17460. https://doi.org/10.1073/pnas.2011914117

Sharma, R., 2015. Environmental Issues of Deep-Sea Mining. Procedia Earth Planet Sci 11, 204–211. https://doi.org/10.1016/j.proeps.2015.06.026