Brown algae: A powerful but little known tool against global warming

UP to 0.55 gigatons each year: This is the potential for eliminating atmospheric CO2 that brown algae would possess, according to a recent study by German scientists. Here's the lowdown.

Composed of chlorophyll and a pigment called "fucoxanthin," brown algae grow in a marine environment and are capable of absorbing large quantities of carbon dioxide, which they then release into the water in the form of carbohydrates.

While the significant capacity of brown algae to absorb CO2 makes them naturally important allies in the fight against global warming, it is difficult to determine the exact quantity of carbon dioxide these marine plants are able to eliminate from the atmosphere.

To obtain more precise data on the subject, a team of researchers from the Max Planck Institute for Marine Microbiology (Bremen, Germany) closely studied "bladderwrack," a species of brown algae that lives in rocks and can grow up to 30 centimeters in length.

The work was carried out at the Tvärminne Zoological Station in southwest Finland. The scientists used a substance separation technique (chromatography) and found that the rockweeds studied, located on the coast of the Baltic Sea, secreted about 0.3% of their biomass per day in the form of fucoidan, a nutritional supplement with multiple benefits.

While secretion rate is measured yearly, brown algae has been observed to convert about 0.55 gigatons (550 million tons) of CO2 into carbohydrates each year. “Fuc­oidan made up about half of the ex­cre­tions of the brown al­gae spe­cies we stud­ied, the so-called blad­der­wrack," says Hagen Buck-Wiese, a researcher at the Max Planck Institute and co-author of the study, in a statement.

In comparison, Germany's annual greenhouse gas emissions in 2020 amounted to 0.74 gigatons of carbon dioxide, according to estimates by the German Federal Environment Agency.

Published in the journal Proceedings of the National Academy of Sciences (PNAS), the study also states that the brown algae Fucus vesiculosus has the advantage of being able to sequester atmospheric CO2, without interfering with its growth.

"This makes brown algae particularly good helpers in removing carbon dioxide from the atmosphere in the long term -- for hundreds to thousands of years," the researchers argue. The researchers plan to study other species of brown algae in other locations, with the goal of further utilizing "the great po­ten­tial of brown al­gae for cli­mate pro­tec­tion."