Off the coast of southwest Greenland, 8,000 floating seaweed rafts are quietly performing one of nature's most elegant carbon-capture tricks — a discovery that reveals how macroalgae forests may be far more powerful allies against climate change than scientists previously understood.
An international team of researchers from Germany, Portugal, Saudi Arabia, Denmark, and the UK has for the first time tracked these vast underwater forests using satellite imagery, computer modelling, and ocean current monitoring devices. What they found is a natural conveyor belt of remarkable efficiency: as seaweeds drift in offshore currents, they travel hundreds of kilometres across the ocean. When surface waters cool, the floating vegetation sinks below the surface, where it breaks down and carries carbon to the deep ocean — where it can remain locked away for at least a century.
The numbers are striking. Previous research suggested that between 4 million and 44 million tonnes of macroalgae-derived carbon sink annually to depths of up to 200 metres. Now this new tracking work shows just how far and how effectively this transport mechanism actually works. Large seaweeds, known as macroalgae, absorb vast amounts of atmospheric CO2 during their growth. Rather than returning that carbon to the atmosphere when they die — as happens with many organic matter — these forests have evolved a system that essentially packages carbon for long-term storage in the ocean's depths.
"Our findings illustrate a tangible oceanic conveyor belt that links thriving coastal macroalgal forests with the deep ocean's carbon reservoir," said Prof Ana Queirós, marine climate change ecologist and climate change lead at Plymouth Marine Laboratory. For policymakers and climate scientists, this is significant. It means that protecting and restoring coastal seaweed ecosystems isn't just about preserving marine biodiversity — it's about maintaining what amounts to a nature-powered carbon removal system operating at planetary scale.
The research methodology itself represents a leap forward in our ability to understand these hidden processes. By combining multiple data sources — satellite observation of seaweed distribution, computer models of how currents move, and direct measurements from ocean monitoring devices — the team built a detailed picture of how carbon actually moves through the ocean. This kind of integrated approach is becoming essential as scientists race to understand all the ways that natural systems can help us address climate change.
What makes this discovery particularly hopeful is that it points to a solution already built into nature, waiting to be harnessed. Unlike technological carbon capture systems that require enormous energy inputs and infrastructure, macroalgae forests have been doing this work for millennia. The challenge now is recognising their vital role and ensuring these ecosystems thrive. Coastal protection, reducing pollution, and preventing overharvesting all become climate action in this light.
As the world searches urgently for pathways to reduce atmospheric carbon, discoveries like this remind us that some of the most effective tools may already exist in our oceans. The underwater forests off Greenland are working, quietly and continuously, to draw down greenhouse gases and store them in the abyss — a process scientists are only now beginning to fully appreciate.