New research reveals how Greenland seaweed helps lock away ocean carbon

New evidence published by an international research team, including scientists from Plymouth Marine Laboratory, has identified how floating macroalgae — commonly known as seaweed — can transport carbon from coastal zones to deep-ocean sinks, where it may be stored for centuries. The findings help clarify a previously uncertain pathway in the ocean’s role in long-term carbon sequestration, with potential implications for water quality, coastal ecosystems and broader climate regulation.

The study focused on macroalgae mats off southwest Greenland and tracked their movement hundreds of kilometres offshore using a combination of satellite imagery, ocean drifters and numerical modelling. Researchers found that currents can carry buoyant seaweed far from shore, where strong vertical mixing and deep convection events eventually cause it to sink to depths around or below 200 metres. In these deep waters, carbon contained in the algae may remain sequestered for extended periods, effectively removing it from the atmosphere and surface ocean.

Lead author Dr Daniel Carlson noted that the research “highlights not only the importance of macroalgae in the ocean carbon cycle, but also the critical role of international scientific collaboration and support for long-term, open-access datasets.”