Seaweed carbon sink power revealed

Forests – under the ocean – are critical stores of carbon, a study has found.

While it’s commonly known that the world’s terrestrial forests – trees on land – can lock away carbon, the role of the world’s seaweed forests carrying out the same duties is less known.

Published in the journal Nature Geoscience, the new study led by the University of Western Australia has put the carbon transport capacity of ocean seaweed at 10-170 million tonnes per year.

That carbon, captured by seaweed forests, can be used to generate energy for the plants. About 15% of the carbon absorbed is transferred to deep ocean sinks.

Marine ecologist Karen Filbee-Dexter says the findings highlight the overlooked role of seaweed in carbon storage, and it’s particularly strong in select regions.

“The seaweed forests of Australia, the US, New Zealand, Indonesia and Chile [have] particularly high carbon removal capacity,” Filbee-Dexter says.

The carbon storage capacity of seaweed is something that the research group says should make conservation efforts for seaweed and other macroalgae a priority.

Albert Pessarrodona, who was the second author of the study, says restoration efforts would enhance the ability of ocean forests to support climate mitigation strategies.

“Seaweed forests… are being lost at alarming rates in many regions of the world due to a variety of human pressures such as ocean warming, marine heatwaves, nutrient pollution and overfishing,” says Pessarrodona.

“While not a standalone solution, the restoration of seaweed forests could aid in removing carbon from the atmosphere while simultaneously enhancing biodiversity and supporting fisheries.

“Sustainable management of seaweed forests therefore addresses the combined biodiversity, pollution and climate crisis.”