Thursday, November 30, 2023

Deep sea mining could cause undue harm to local jellyfish populations, study suggests

By Joshua Hawkins
Published Nov 25th, 2023 

Image: donfiore / Adobe

Deep sea mining could pose a danger to local jellyfish populations, a new study suggests. The first-of-its-kind study was conducted by researchers and marine ecologists and aims to see just how much deep sea mining affects the wildlife that calls the sea floor home.

There are, of course, several benefits to mining the ocean floor, including access to rare minerals and elements that we can’t find in high concentrations above the ocean surface. However, mining under the sea could actually cause harm to deep sea jellyfish, as sediment stirred up from the mining sites could activate potentially damaging stress responses in the creatures, the researchers say.

When stressed, deep-sea jellyfish and other cnidarians like them excrete mucus. The study’s co-lead, Vannessa Stenvers, says that when sediment concentrations within the water are above 17 mg/l (milligrams per liter), any exposed jellyfish produce excessive amounts of mucus, covering their bodies in the gunk.

Image source: nikkytok / Adobe

This, the researchers say, is a sign of acute stress within the jellyfish, and that producing so much mucus can actually expend a ton of energy from the deep-sea jellyfish, making long-term excretion of high levels of mucus extremely damaging to their health, especially if they are exposed to high sediment levels for longer periods of time.

One of the biggest reasons the researchers are concerned about the effects of deep sea mining on these jellyfish populations is because food in the deep sea is extremely scarce. That means that any extra energy that is burned is undoubtedly harder to regain. And if there is no extra energy coming in, the jellyfish could potentially starve to death.


It’s a terrible revelation and one that will probably go unheeded by many companies too focused on the riches that deep sea mining could bring to the table. Still, it’s good to see researchers discovering the dangers deep sea mining could pose to these jellyfish. Hopefully, companies keep that in mind as they scour the bottom of our oceans for rare minerals and materials.

The study is published in Nature Communications.

Mucus-Covered Jellyfish Hint at Dangers of Deep-Sea Mining

Shipboard experiments suggested that sediment from the exploitation of metals in the ocean could be harmful to marine life.

Researchers approximated the effects of mining by pumping sediment into the tanks of helmet jellyfish to ask how the animals would cope with muddy water.
Credit...Helena Hauss


By Kate Golembiewski
Nov. 28, 2023

A treasure trove of metal is hiding at the bottom of the ocean. Potato-size nodules of iron and manganese litter the seafloor, and metal-rich crusts cover underwater mountains and chimneys along hydrothermal vents. Deep-sea mining companies have set their sights on these minerals, aiming to use them in batteries and electronics. Environmentalists warn that the mining process and the plumes of sediment it would dump back into the sea could affect marine life.

A series of shipboard experiments on jellyfish in the Norwegian fjords, published Tuesday in the journal Nature Communications, offer insights into those warnings. The scientists approximated the effects of mining by pumping sediment into the jellies’ tanks, essentially asking how the animals would cope with the muddy water. The answer? Not well.

The researchers selected helmet jellyfish as their research subjects because of the ubiquity and hardiness of the dinner-plate-size creatures. The idea was to choose an organism that the team could easily get hold of “and then expose it to conditions that we expect in the mid-water in the open ocean,” said Helena Hauss, a marine ecologist at the Norwegian Research Center who conducted the study while working at the GEOMAR Helmholtz Center for Ocean Research Kiel in Germany.

The jellies, which are found around the world in waters 1,500 to 2,000 feet deep, serve as representatives of the countless soft-bodied animals living in the open ocean that could be affected by mining.

The scientists caught the jellyfish, which are abundant in Norway’s fjords, with fine mesh nets and brought them below deck of their research vessel for study in dim rooms illuminated with red light.

“They really are adapted to live in eternal darkness,” said Vanessa Stenvers, an author of the paper and a doctoral candidate at GEOMAR. “And that’s why we had to be very careful when we observed and we always had to use red light to not disturb them.”

Helmet jellyfish were chosen for the study because they are hardier than many of their relatives. “You can catch this thing in a net and it doesn’t turn into goo,” said one researcher.
Credit...Vanessa Stenvers

The scientists exposed the jellies to plumes of sediment comparable to what they might experience around deep-sea mining sites. One response from the jellyfish was visible to the naked eye. They tried to rid themselves of the sediment by producing excess mucus, in white ropes that Ms. Stenvers likened to frosting.

Other stress responses occurred at the molecular level, with several genes associated with tissue repair and the immune system becoming active.

“One thing that worries me is that everything that these animals do to rid themselves of sediment or combat pathogens, it takes energy,” Dr. Hauss said. In the deep ocean where the jellyfish live, food is scarce, and dealing with the effects of muddy water might require more energy than the jellies can obtain from their diet. “It could lead to starvation, it could lead to lower reproduction rates,” Dr. Hauss said.

Jeffrey Drazen, a marine biologist at the University of Hawaii at Manoa who was not involved with the research, said that “this is a really welcome study” in light of the likelihood that deep-sea mining will release large amounts of sediment. “This is really the first study that has looked at a water column animal’s response to mud,” he said.

Dr. Drazen noted that the species the researchers chose for the study was hardier than many of its relatives. “This is a really robust jellyfish. You can catch this thing in a net and it doesn’t turn into goo,” he said, and its stress response to the sediment indicates that other soft-bodied sea creatures exposed to sediment for longer periods of time might fare even worse.

According to the researchers, their findings suggest that deep-sea mining could negatively affect not only marine life, but human life as well. Midocean animals like helmet jellyfish contribute to a biological cycle that keeps stores of carbon in the deep and not in the atmosphere. And fish that humans rely on for food, like tuna, feed on these midocean communities.

“It’s very important to us, even on land, even though we don’t deal with it on an everyday basis,” Ms. Stenvers said. The good that the open ocean does for our planet “could be lost if we don’t protect it.”

A version of this article appears in print on Nov. 28, 2023, Section D, Page 2 of the New York edition 

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