Study accounts for the contribution of marine forests to carbon sequestration

In times of climate crisis, this is important news

A recently published study, in which Isabel Sousa Pinto, a professor from the Biology Department of the Faculty of Sciences of the University of Porto, participated, demonstrated that algal forests (sea forests) transport 56 million tons of carbon to the deep sea per year , playing a more important role than we imagined in these functions.

Brown algae that exist along the planet's coastal areas transport, every year, around 15% of the carbon captured to the bottom of the ocean, where part of this total can be retained for at least a century, reveals the paper published in the scientific journal Nature Geoscience.

“This is the first article that seeks to account, at a global level, the contribution of seaweed forests to carbon sequestration”, explains, in an interview with the newspaper Público, the FCUP professor, also a researcher at the Interdisciplinary Center for Marine and Environmental (Ciimar).

According to the authors of the work, it is estimated that large brown algae are capable of transporting around 56 million tons of carbon to the deep sea every year (between 10 and 170 million tons). Of this total, it is estimated that between four and 44 million tons could be trapped there for at least a century.

In times of climate crisis, this is important news, as the carbon that remains at the bottom of the ocean is not accumulating in the atmosphere.

Furthermore, highlights Isabel Sousa Pinto, still in an interview with this media outlet, these algae also provide several services in the ecosystem: they are “habitat for other species, absorbing nutrients that come from the land and which can cause environmental problems, cleaning, therefore, water.”

The authors of this study used global ocean models to simulate the fate of carbon contained in algae from the coast to the ocean floor. This theoretical work considered several factors such as global distribution maps of brown macroalgae species, the transport time of a brown algae species to the deep sea and the decomposition rate of these organisms.


Importance of including macroalgae in representations of the global oceanic carbon budget

Kelp forests, composed mainly of giant brown algae, such as the famous kelp, are the most extensive and productive vegetated coastal ecosystem on the planet. These forests can grow as quickly as terrestrial forests and are therefore highly efficient at capturing and storing carbon.

These organisms can be found mainly in waters rich in nutrients, colder and closer to the coast, since, as they depend on sunlight to carry out photosynthesis and grow, they do not thrive at great depths.

The study estimates that carbon export from algae below 200 meters depth totals three to four per cent of the ocean's carbon sink, according to a press release from CIMAR-LA, the associated laboratory that joins Ciimar and the CCMAR.

The results thus indicate the importance of including macroalgae in representations of the global oceanic carbon budget, which does not yet consider marine vegetation in the climate equation.

The study of Nature Geoscience was led by Karen Filbee-Dexter, a researcher at the Norwegian Institute of Marine Research and the University of Western Australia. In addition to Isabel Sousa Pinto, Jorge Assis and two other Portuguese-speaking scientists also participate in the study: Ana M. Queirós, professor at the Plymouth Marine Laboratory, in the United Kingdom, and Carlos M. Duarte, professor at King Abdullah University of Science and Technology, in Saudi Arabia.


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