Deep-sea mining risks disrupting the marine food web, study warns

Drilling for minerals deep in the ocean could have immense consequences for the tiny animals at the core of the vast marine food web — and ultimately affect fisheries and the food we find on our plates, according to a new study.

Drilling for minerals deep in the ocean could have immense consequences for the tiny animals at the core of the vast marine food web — and ultimately affect fisheries and the food we find on our plates, according to a new study.

Deep-sea mining means drilling the seafloor for “polymetallic nodules” loaded with critical minerals including copper, iron, zinc and more. While not yet commercialized, nations are pursuing deep-sea operations amid rising demand for these minerals in electric vehicles and other parts of the energy transition, as well as for technology and military use.

The researchers examined water and waste gathered from a deep-sea mining trial in 2022.

What the study discovered

University of Hawaii researchers studied an area of the Pacific Ocean called the “twilight zone,” about 650-5,000 feet (200-1,500 meters) below sea level. Their peer-reviewed findings, published Thursday in the Nature Communications scientific journal, say mining waste could affect anything from tiny shrimp smaller than .08 inches (2 millimeters) long to fish 2 inches (5 centimeters) long.

That’s because, after mining companies bring the mineral-rich nodules up to the surface, they have to release excess sea water, ocean floor dirt and sediment back into the ocean. That creates a murky plume of particles about the same size as the naturally occurring food particles normally eaten by the zooplankton that swim at that depth.

That’s a little more than half of the zooplankton in the ocean. If those organisms eat the waste particles — what senior study author Brian Popp called “junk food” — then that affects 60% of micronekton that eat the zooplankton.

“Surface fish can dive down deep into the water, they feed on organisms down at depth,” said Michael Dowd, study lead author and oceanography graduate student. “If these organisms down at depth are no longer present because their food web has collapsed, then that can impact higher food webs and more commercial interests.”