Dowd said there had not been many studies that looked at the mid-water, with others focusing on the impacts on the seafloor. Photo: Supplied
A new deep sea mining study says sediment plumes caused by the industry could disturb the food web which could impact bigger fish, like tuna.
The study by researchers at the University of Hawai'i at Mānoa published in Nature Communications shows sediment waste discharged from deep sea mining could disrupt marine life in the mid-water, between 200-1500 meters deep, known as the "twilight zone".
It is home to tiny animals, like zooplankton, that serve as the ocean's basic food building blocks.
Lead author of the study Michael Dowd said if full-scale mining happened there could be severe impacts on these animals' primary food source.
"We found that the plume material was 10 to 100 times less protein rich compared to background material," Dowd said.
"These animals serve as the food source for deep diving top predators that are important in commercial fisheries, such as tuna. So, impacts on these small marine animals at 1200 meters could turn into impacts for humans and the food served on our dinner table."
The study, Deep sea mining discharge can disrupt midwater food webs, looked at the effects mining waste had during a 2022 trial in the Clarion-Clipperton Zone.
It is an area in international waters in the north Pacific between Hawai'i and Mexico, that has garnered a lot of interest in nations and companies interested in deep sea mining.
Dowd said there had not been many studies that looked at the mid-water, with others focusing on the impacts on the seafloor.
"We're seeing that there are definitely potential impacts to this ecosystem," he said.
"The real question is, are we ready to risk ocean ecosystems for mineral extraction? That's a societal decision but it must be informed by our science. Our study helped provide that foundation.
"So far, we found ecological impacts, some areas might be more effective than others, but the pattern is consistent."
The waste from deep sea mining comes from sediment that is picked up through the collection of nodules. The excess sediment and seawater need to be returned to the ocean.
Seabed mining has not yet started and where the sediment will be released is still unknown, but some mining operators have proposed midwater mining discharge within the twilight zone.
Deep-sea mining frontrunner The Metals Company (TMC) is hoping to mine in Clarion-Clipperton Zone.
TMC environmental manager Dr Michael Clarke said the company's return water is released at 2000 meters, which is well below the 1000-meter zone where the study finds zooplankton life falls sharply.
"The sediment dilutes to background concentrations very rapidly on release as it disperses into the vastness of the Pacific," Clarke said.
"Concern about midwater impacts is understandable, but the data have moved on and so should the conversation."
