Sourcing rare earth metals from the depths of the ocean may have consequences for Pacific Ocean tuna
Bigeye tuna Thunnus obesus caught with three-pole one-line rig (Tropical Pacific Ocean). ©NOAA Photo Library
In a specific section south of Hawaii and west of Mexico called the Clarion-Clipperton Zone in the Pacific Ocean, there are around 1.1 million kilometres of deep-sea mining exploration contracts. It also happens to be a territory for bigeye, skipjack and yellowfin tuna species. A recent study published in NPJ Ocean Sustainability tested the effects of two climate-change scenarios on the distribution of these tuna species in this area and found that these species’ populations are projected to rise as time goes on. However, with the projected increases in deep-sea mining prospects and contracts, there are likely going to be interactions between mining, fish populations, and climate change with the effects of these interactions still unknown.
Nearly two-thirds of the ocean are areas beyond national jurisdiction — also called “the high seas” —with different governance structures for non-living resources and living resources. In ocean areas beyond one national jurisdiction, legalities and governance structures blur and diffuse responsibility and create challenges for managing these areas, particularly under situations of conflicting interests.
“[Deep-sea mining], it’s an emerging technology. Companies are using the excuse of the electrification of cars, and batteries needed for other things, to justify exploring the deep sea,” said Juliano Palacios Abrantes, co-author of the study, and postdoctoral fellow in the Changing Oceans Research Unit at the Institute for the Oceans and Fisheries. “The tricky part is that we are very unaware of the impacts of deep-sea mining activities happening or projected to happen.”
The majority of marine mining efforts have been limited to shallow coastal water where sand, tin and diamonds are more readily accessible. However, deep sea mining is a growing subsection of mining, involving the retrieval of minerals and deposits from the ocean floor at depths of 200 metres to 6,500 metres. There are currently 17 deep-sea mining exploration contracts issues in this particular region, as the Clarion-Clipperton Zone has a high number of polymetallic nodules on the seafloor — mineral concentrations containing valuable metals — while also being the site of commercial fish stocks of tuna falling under the jurisdiction of two tuna regional fisheries management organizations.
The Metals Company — a Vancouver-based company — is one the main industry players to push for more deep-sea mining exploration, teaming up with the island nation of Nauru to get the first license to start industrial-scale deep-sea mining. This initiative was delayed recently, but may still go ahead in the future. However, while the ocean surface may look homogenous to the untrained eye, the biodiversity in it is unparalleled which brings up major concerns about the possible repercussions to the marine ecosystems in the area. Plumes sent up by deep-sea machinery may create sediment clouds that interfere with and harm filter-feeding apparatuses and gills of tuna and their prey, extending horizontally for tens to hundreds of kilometres and vertically for hundreds to thousands of metres.
Image from USGS
“We don’t really know what the effect of that plume is going to be on the environment, on other animals,” said Palacios-Abrantes. “There’s so much uncertainty on what these activities are going to do to the ecosystem, like noise pollution, water pollution. This is a pristine space where humans have little to no impact yet. And suddenly, you’re going to do a massive intervention.”
Particles from the plume may also be dissolved into seawater or get stuck to sediment or organic particles, creating a risk of ingestion and incorporation into deep-sea food webs which eventually make their way to human consumption through tuna. The two tuna fisheries organizations in the area oversee bigeye, skipjack and yellowfin tuna, capturing around 3.5 million tonnes of tuna a year — 66 per cent of global tuna catches reported in 2021. Some of the most profitable fisheries in the world are in these areas, with the two organizations bringing in around $5.5 billion USD every year.
Not only are the 3.5 million tonnes of tuna going to be affected, but as migratory species, tuna fish interact with marine ecosystems all around the world. This may lead to a possible domino effect on marine life. In addition, with an increase in mining vessels, tuna behaviour may change, impacting predators who depend on consistent tuna for survival. Under the climate change scenarios tested in the study, the three tuna species’ populations are projected to increase which raises big concerns for the future.
“So basically, there are no rules right now [for deep-sea mining in the region], and there are meetings currently going on to come up with some,” said Palacios-Abrantes. “There’s been a lot of countries calling for a moratorium. Ironically, Canada also made a call for putting a moratorium on deep-sea mining. We decided, in the context of global change, and in the context of species distributions, to research what may happen to tuna in the Pacific if industrial deep-sea mining goes forward.”
There are two main threats to tuna under climate change: increasing temperatures and oxygen levels which decrease with warmer waters, both posing huge threats to the red-blooded fish that need a lot of oxygen to swim. Any impacts on tuna also impact countries that fish in the Pacific region, such as Mexico, Venezuela, Nicaragua, Panama and Colombia — between 2009 and 2018, Mexico and Venezuela landed 250,000 tonnes of tuna generating $512 million USD. Any negative changes to tuna populations will have potentially devastating socioeconomic losses for tuna-dependent nations, including South Pacific Island States, Japan, Mexico, Indonesia, and the United States.
“There’s a lot we don’t know,” said Palacios-Abrantes. “But we need to keep an eye on [deep-sea mining] as it develops. It may have a lot of consequences.”
Climate change to drive increasing overlap between Pacific tuna fisheries and emerging deep-sea mining industry was published in NPJ Ocean Sustainability
Tags: deep sea mining, fish stocks, IOF postdoctoral fellows, Juliano Palacios-Abrantes, mineral deposits, tuna, Vancouver