Polymetallic nodules cover the seafloor throughout the Clarion-Clipperton area, and new research shows that each of these strange metallic potatoes contains an entire community of microscopic life unique to that habitat.
There’s a reason humans called them polymetallic nodules: we’re really interested in the metal part.
Our society’s dependence on metals like nickel, cobalt, and copper is rapidly increasing, and these nodules are full of them, as well as iron and manganese.
But polymetallic nodules are not an easily renewable resource. Although it only takes a few minutes to extract a nodule from the seafloor, it took millions of years for it to form.
Scientists fear that this speculative industry will destroy a unique ecosystem that we barely knew existed, before we have a chance to understand it.
“Our results show that commercial mining can lead to an irreversible loss of unique and undescribed biodiversity associated with nodules,” explains deep-sea biologist Sabine Gollner of the Royal Netherlands Institute for Marine Research.
“This needs to be considered in the environmental management of deep sea mining.”
The research is published in Scientific reports.
The nodules were collected in 2019 by a crew of scientists participating in an expedition to the Clarion-Clipperton area aboard the German research vessel RV Sonne, as part of the JPI Oceans Mining Impact II project.
The team carefully lowered a core barrel to depths of about 4 to 6 kilometers (2.5 to 3.7 miles) to sample a piece of seafloor sediment and the nodules embedded there.
For this study, researchers examined 244 individual nodules for signs of life in the cracks and pores.
The nodules – and their marine inhabitants – were then frozen and taken to a laboratory.
One hundred and fifty-three of the nodules came from an area where the German Federal Institute for Geosciences and Natural Resources (BGR) holds an exploration contract from the International Seabed Authority. 91 others were collected in an area where the Belgian company Global Sea Mineral Resources – a subsidiary of DEME – holds an exploration contract.
Until now, most biodiversity assessments in the Clarion-Clipperton area have focused on organisms living in sediments or clinging to the surface of nodules.
Much of the deep sea is covered in a fine mud, but many animals that live there need a more solid surface to attach themselves to: polymetallic nodules provide an ideal substrate for these creatures.
“We already knew that polymetallic nodules provide attachment surfaces for deep-sea organisms, but very little was known about the animals that lived there,” said marine genomicist Coral Diaz-Recio Lorenzo. Science alert.
By opening the nodules, scientists discovered miniature animated ecosystems in the nooks and crannies.
Roundworms and crustaceans were the most common inhabitants, and a species of armored amoeba, Thuramminadominated his species. In just a few nodules, they recorded bristle worms, mud dragons, tardigrades, and other less common creatures.
“What surprised us most was the difference between the communities living inside the nodules and those living in the neighboring sediments,” Diaz-Recio Lorenzo said.
“Remarkably, nodule communities collected in areas separated by approximately 1,000 kilometers were more similar to each other than to surrounding sediment communities.”
Using microscopes to take a closer look at the nodules, the researchers also found fossils of diatoms, radiolarians and sea sponges embedded in the ancient layers.
“The presence of…biogenic particles in crevices indicates that at least some cavity structures were colonized by ancient organisms, although this does not necessarily demonstrate in situ colonization at the time of incorporation,” the team writes.
“Sponge spicules were visible in the images (using a scanning electron microscope), and the presence of foraminiferal species Saccorhiza sp.which uses sponge spicules to construct its tests (shell-like structures), indicates that the nodules may have provided habitat on the seafloor for millions of years.
If the ISA allows deep-sea mining companies to collect nodules on a massive scale, these ancient ecosystems will be irreversibly destroyed.
“As their communities differ from those in the surrounding sediments, only protecting sedimentary habitats would not preserve this biodiversity,” added Diaz-Recio Lorenzo.
“Large-scale removal of nodules could therefore lead to irreversible losses of unique species and ecological communities that we are only beginning to understand.”
These distant, microscopic worlds may seem quite isolated from our own, but the reality is that we don’t yet have a sense of how they play into global networks of nutrients, carbon, and ecology.
Scientists are racing to find out before it’s too late.
The research was published in Scientific reports.
This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. Although we are proud of our process, we are only human. If you spot an error, please let us know.
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