Kelp emerges as powerful carbon storage solution in marine forests in Northern Portugal
Renaud de RICHTER
In marine forests in Northern Portugal, kelp emerges as powerful carbon storage solution
CIIMAR - Interdisciplinary Centre of Marine and Environmental Research 15/09/2025A pioneering study led by researchers from the Interdisciplinary Center of Marine and Environmental Research (CIIMAR) and the Marine and Environmental Sciences Center (MARE) identifies seaweed forests on the northern coast of Portugal as strategic allies in carbon capture and storage.
The new study published in the journal Scientific Reports reveals that kelp forests play a crucial role in capturing and storing carbon, offering a powerful natural tool for mitigating the effects of climate change. This work focused on the study of marine forests on the north coast of Portugal, particularly the species Laminaria hyperborea and Saccorhiza polyschides, the two predominant species in this area of the country.
The research, led by researchers Francisco Arenas from CIIMAR and João Franco from MARE, with contributions from a team of researchers from both centers, aimed to quantify for the first time the carbon stock stored by these habitats in northern Portugal.
The marine forests of Northern Portugal
Kelp forests are habitats formed by large brown algae that play a crucial role in maintaining biodiversity and local marine productivity.
"These habitats are common on the north coast of Portugal, where there are unique conditions for their development, and represent the southernmost frontier for some of the species found here," explains Arenas, leader of the research. However, these habitats are highly vulnerable to climate change.
"A process of tropicalization has already been detected in Portuguese waters, which puts the associated biodiversity at risk, as well as the ecological services that these forests provide, including the ability to capture and store carbon, known as Blue Carbon, contributing to climate change mitigation," he adds.
Impressive results
The study in question quantified for the first time the carbon stock stored by these habitats in northern Portugal through field measurements, including extent, biomass, growth, and carbon content. "It was the first assessment of the value of blue carbon associated with kelp forests in Portugal," says the study leader and CIIMAR researcher.
The results, published in the article "Potential blue carbon in the fringe of Southern European Kelp forests," show that these forests store around 16.48 gigagrams (Gg) of carbon in an area of 5,100 hectares, equivalent to more than 5,000 football pitches.
Although they cover a relatively small area compared to the size of the planet, these kelp forests demonstrate a carbon capture efficiency per square meter that is comparable to or greater than more extensive habitats. This figure corresponds to 14% of the blue carbon inventoried so far for Portugal, whose previous estimates were limited to marshes and seagrass beds.
Key allies in blue carbon
Thanks to their high productivity, it is estimated that these habitats are able to sequester and export around one third of the carbon captured annually by all marine plant habitats in the country. This exceptional rate of carbon sequestration highlights the essential, and until now largely undervalued, role of kelp forests in mitigating climate change.
According to Arenas, these marine forests are "often unknown and undervalued, despite their extremely important ecological and economic value on the north coast of Portugal." These habitats are fundamental both for their ability to mitigate climate change and as promoters of local biodiversity, providing shelter, food and breeding areas for countless marine species.
The study also recommends specific policies for monitoring, conserving and eventually restoring these areas, reinforcing their importance not only as carbon sinks but also as vital habitats for ocean health. In light of the current climate crisis, scientists argue that the inclusion of kelp forests in marine conservation and blue carbon policies should be a priority, both nationally and globally.
"With the European Union's Nature Restoration Law in its early stages of implementation, it is urgent to develop and implement effective ecological restoration techniques, particularly in habitats that are highly vulnerable but also have high potential for providing ecosystem services, such as marine forests," concludes Arenas.
More information: João N. Franco et al, Potential blue carbon in the fringe of Southern European Kelp forests, Scientific Reports (2025). DOI: 10.1038/s41598-025-09361-9
Tom Goreau
Brief comment. I’m actively working on regenerating shellfish in Galicia, the extension of Northern Portugal, and have worked on seaweed mariculture for decades.
This spectacular coast is extremely biologically productive, but is exposed to the full fury of North Atlantic storms, which are increasing in intensity, so there is little prospect of intensively farming seaweed in these waters. Kelp will grow but is hard to control or reap, and most production will be flushed by waves into deep North Atlantic abysses.
The world’s highest surfing waves hit Northern Portugal! It’s much better to see from a high cliff than in the water!
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Tom Goreau
Most of kelp biomass is consumed by microbes on the sea floor and only a small part ends up as long term sediment organic carbon storage.
If it were harvestable the carbon could be converted into biochar and bioplastics with longer lifetimes.
Thomas J. F. Goreau, PhD
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From:
Renaud de RICHTER <renaud.d...@gmail.com>
Date: Tuesday, September 16, 2025 at 09:06
To: Tom Goreau <gor...@globalcoral.org>
Subject: Re: [CDR] Kelp emerges as powerful carbon storage solution in marine forests in Northern Portugal
Tom,
If in this region Kelp will grow but is hard to control or reap, and most production will be flushed by waves into deep North Atlantic abysses.
Therefore their C content will be stored for > 1000 years ?