A number of deep sea polychaets.
Wildlife in the deep sea consists mainly of polychaete worms that live down in the soft seabed. The majority of species are still unknown to science.
Photo: Helena Wiklund, Thomas Dahlgren & Adrian Glover.

Urgent need to map deep-sea biodiversity


In the search for battery metals, attention is now turning to the deepest parts of the world's oceans. But life in these areas is virtually unexplored and the effects of mining are therefore difficult to predict. The few inventories made so far reveal a large but unknown biodiversity - nine out of ten species are new to science.

Ongoing electrification means that the demand for various minerals is growing at record speed. The search is now focusing on the deepest parts of the world's oceans, as the soft and dark seabed contains large deposits of cobalt, nickel, copper and manganese. But we know almost nothing about what life is like on the really deep seabed and how it will be affected by mining.

"It is a big problem that these areas are so unexplored. We don't even know which species and ecosystems are there, so how can we describe what will happen?" says Helena Wiklund, researcher at the Department of Marine Sciences.

Portrait Helena Wiklund
Helena Wiklund at the Department of Marine Sciences is doing research on the deep sea wildlife.

Companies are lining up

Together with researchers at the Natural History Museum in London, Helena Wiklund and fellow researcher Thomas Dahlgren have examined seafloor samples from a large mineral-rich area in the eastern Pacific Ocean, the so-called Clarion-Clipperton zone between Mexico and Hawaii. Here, companies are currently queuing up to start mining operations. As the area is in international waters, the UN's International Seabed Authority issues mining licences. This has not yet been done, but it is probably only a matter of time, according to Helena Wiklund.

One characteristic of the wildlife in the zone is that it is very species-rich. In shallower seas, such as the North Sea, many individuals of the same species are often found in the samples. However, in the Clarion-Clipperton samples, the researchers found many different species, but few individuals of each species.

Of 339 annelids collected, mainly polychaetes, 129 were of different species – most of them completely new to science. Previous studies indicate that more than 90 percent of the fauna in the deep sea is undescribed, says Helena Wiklund.

Two women onboard a research ship.
Helena Wiklund sifts through bottom samples during a deep-sea expedition in the Pacific Ocean. Research colleague Diva Amon can also be seen in the picture.
Photo: Leon Moodley

Species at risk of extinction

A further characteristic is that the species composition varies greatly from one site to another. Some species have so far only been found in a single location. If that area is mined and the whole seabed is stirred up, species may become extinct.

"This is why it is important to know how widespread different species are. If a species is only found in a limited area, it is of course more likely to become extinct", says Helena Wiklund.

In order to start mining, an environmental impact assessment is required, which assesses how species and ecosystems will be affected. Knowing which species are present in the area is fundamental to such an assessment. And when it comes to deep seabeds in international waters, there is very little or no such information.

"There are no species lists for these deep areas, instead taxonomic literature from other areas is used, which often leads to incorrect identification. How can one then be able to predict how species and ecosystems will react? It is very important to know the true diversity, says Helena Wiklund.

Field guides are needed

The lack of information is due, among other things, to the fact that it is difficult and expensive to examine seabeds that are several thousand meters deep. Collecting a single sample from the seafloor can take hours, and once the animals come to the surface, they can be tattered and difficult to identify. Often you need to use DNA technology to be able to determine their species. In addition, many species are completely new to science.

"Describing new species takes a very long time. Therefore, we want to publish our results as soon as possible, so that other researchers can help. Partly by using photographs and DNA sequences from our investigations, and partly by gaining access to our collected samples that we have deposited at the Natural History Museum in London", says Helena Wiklund.

"We hope it can be a first step in producing the field guides that are so badly needed for these areas."

Global treaty opens up new opportunities

After 15 years of negotiations at the UN, a global agreement to protect marine areas in international waters was signed this spring. The agreement includes rules to limit environmental impacts and create marine protected areas.

"The agreement opens up opportunities to protect the deep sea in a way that did not exist before. But it also introduces a new layer of bureaucracy that risks hampering research if authorisation processes don't work, and in the worst case scenario provides incentives for corruption," says Thomas Dahlgren, researcher at the Department of Marine Sciences.

Text: Susanne Liljenström

Relevant scientific publications:

Global treaty to protect the ocean

Almost half of the Earth's surface consists of marine areas in international waters that no country owns or controls. In March, 67 countries, including Sweden, signed the UN High Seas Treaty to protect marine biodiversity in such areas. The agreement has four parts: rules for area-based management tools including marine protected areas, environmental impact assessments, marine genetic resources, and capacity building and technology transfer.

The treaty will enter into force once 60 countries have ratified it. It then remains for individual countries to take the necessary measures in their national legislation to fully implement the agreement.