Disturbing the seabed, through activities such as trawling and deep-sea mining, could increase the scale and speed of climate change, according to new research.
In a paper published in the journal Frontiers in Marine Science, an international team of researchers detailed that they systematically surveyed animals living at 17 different sites on the Arctic Ocean floor. They found that they are storing more carbon than initially thought.
“Previous calculations have underestimated how much carbon is being removed by marine life because they were based on data from troughs on the ocean floor,” Terri Souster, the study’s lead author and a researcher at The Arctic University of Norway, said in a media statement. “We systematically assessed a wider range of seafloor sites and found that far more carbon is being removed in continental shelf waters.”
Souster and her colleagues looked at a variety of seabed habitats, including troughs and shallower water, during two cruises on board RRS James Clark Ross in 2017 and 2019. They took almost 1,000 photos of the seabed floor using an underwater camera and analyzed these to see what creatures were present in each habitat. The team also collected samples to see how much carbon they contain.
Seafloor animals, such as corals, sponges, snails and others, extract carbon from their food and the surrounding water to grow and build their skeletons. When they die, their bodies are buried in sediments on the ocean floor, permanently locking away much of the carbon they contain.
Carbon captured and stored by life in the world’s oceans and coastal wetlands is known as blue carbon and it plays a critical role in reducing the amount of greenhouse gases in the atmosphere. Polar coastal ecosystems store much less carbon than mangroves and seagrass meadows per unit area but are huge in area and some are increasing in response to ice loss. This means that they are important like terrestrial forests.
“This study highlights how little we know about the functionality of life in the deep, how it affects the global carbon cycle and the benefits nature in the ocean brings society,” Dave Barnes, paper co-author and a researcher at the British Antarctic Survey, said. “We don’t know which deeper seabed areas store most carbon, so we don’t know what areas we need to prioritize for conservation. Commercial exploitation is racing ahead before we even know what we will be damaging and losing.”
In the researchers’ view, the new study could inform current political debates about bottom trawling and deep-sea mining.
While some governments have called for an international moratorium on seabed mining until scientific gaps have been filled, others have started taking steps toward launching mining operations of their own. Earlier this month, Norway became the first country in the world to move forward with commercial-scale deep-sea mining, inviting companies to apply for mining permits in its national waters.
Meanwhile, the International Seabed Authority is currently drafting regulations that could eventually allow seabed mining in international waters.
