By Abbas Nazil
Seaweed farms could play a far larger role in long-term carbon storage than previously believed, according to a new scientific study examining how these systems alter ocean chemistry.
Researchers from the University of Connecticut and Yale University say seaweed aquaculture does more than temporarily absorb carbon dioxide as plants grow.
Instead, the farms trigger chemical processes in ocean sediments that lock carbon away for centuries or even thousands of years.
The findings challenge a long-held assumption that most carbon captured by seaweed is quickly released back into the atmosphere.
The study, published in Communications Sustainability, shows that seaweed farms function as dynamic blue carbon systems rather than short-lived carbon sinks.
Seaweeds grow rapidly and absorb large amounts of carbon dioxide from the atmosphere during photosynthesis.
Critics have long argued that this benefit is limited because harvested or decaying seaweed eventually breaks down and releases carbon dioxide.
The researchers found that this view overlooks what happens beneath seaweed farms on the ocean floor.
As seaweed grows and sheds organic matter, more material sinks into the sediments below the farms.
These sediments often become low-oxygen environments where microbes follow different chemical pathways.
Under these anaerobic conditions, microbes convert organic carbon into bicarbonate instead of carbon dioxide.
Bicarbonate increases seawater alkalinity and shifts the chemical balance of carbon in the ocean.
This shift reduces the tendency of carbon dioxide to return to the atmosphere.
The process creates a feedback loop that supports long-term carbon storage.
Unlike organic matter that can be disturbed and re-released, bicarbonate alters ocean chemistry in a more permanent way.
Researchers say these chemical changes can persist for thousands of years.
Using sediment models and global estimates, the study suggests existing seaweed farms may already sequester around seven million tonnes of carbon dioxide each year.
There are currently about 3.5 million hectares of seaweed aquaculture worldwide.
The industry is expected to expand significantly as demand for sustainable food and materials grows.
As seaweed farming scales up, its carbon sequestration potential is also likely to increase.
The researchers found that seaweed farms can match or exceed the carbon storage capacity of seagrasses.
Their performance is also comparable to mangroves, which are among the most effective natural carbon sinks.
Beyond climate benefits, seaweed farming offers food, economic opportunities and relatively low environmental controversy.
Scientists say more large-scale measurements are needed to refine carbon estimates and understand seasonal variations.
The findings may also open the door to carbon credit markets and new investment opportunities.
Researchers conclude that seaweed farms should be taken seriously as reliable tools for climate mitigation.
