Deep sea mining can cause ocean animals such as fish and shrimp to leave surrounding areas for at least a year.
Some countries and companies are eager to tap the seabed as a rich source of minerals and precious metals, such as nickel, manganese and cobalt, that could be useful in the production of goods like batteries for electric cars.
However, not much is known about how the extraction of these materials on the seafloor could affect surrounding wildlife. Commercial deep-sea mining operations have yet to commence, and talks are currently underway at the International Seabed Authority in Jamaica to formalize regulations governing the industry.
In 2020, Japan conducted a deep-sea mining test at the Takuyo-Daigo Seamount, a seamount about 900 meters below the surface of the northwestern Pacific Ocean. In the test, a crustal excavator machine scraped the crust across 129 meters for a total of 109 minutes over seven days, spreading plumes of sediment across the surrounding waters as it went.
Travis Washburn at the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, and his colleagues took the opportunity to investigate the impact of the test on local marine wildlife.
One month before the test, the researchers deployed a remote underwater vehicle to record video of the megafauna (animals larger than 1 centimeter) present in the 300-square-meter area around the test site. They he then repeated this one month and 13 months after the completion of the trial.
For stationary organisms, such as sea sponges, sea anemones, and corals, their populations remained stable throughout the study period.
For highly mobile organisms, such as fish, shrimp and jellyfish, their numbers more than a year after the test were 43 percent lower in areas that were directly affected by sediment displacement compared to before the test. They were also 53 percent lower in areas adjacent to sediment columns, suggesting that the more mobile animals may avoid even the periphery of mining areas, Washburn says.
“Considering that this was a very small mining test in area and time, directly impacting a few hundred square meters over a period of days, large-scale mining covering 10 to 100 square kilometers and lasting for years could cause the disruption of mobile megafauna over entire seamounts for prolonged periods,” says craig smith at the University of Hawaii at Manoa, who was not involved in the study.
The outlook for deep sea mining remains uncertain, with some countries including Canada, New Zealand and France calling for a ban or moratorium on the practice.
It’s crucial to understand how deep-sea mining will affect marine ecosystems, Washburn says. “For mining regulations, you need to know to what extent an area is affected,” he says. “You have to have preserve zones, which could extend that mining footprint by a decent amount.”
“That swimming animals were kept away from test sites and adjacent areas for so long is a worrying sign that commercial mining would have an even worse and broader environmental impact than previously thought,” says the author and biologist. Marine. helen scales. “This study highlights how important it will be to do much more scientific research to fully understand how mining will alter deep-sea ecosystems.”
