Brown algae can sequester huge amounts of CO2

The official publication of the National Academy of Sciences of the United States has made public a study related to the great capacity of brown algae to absorb carbon dioxide from the air, surpassing even that of terrestrial forests, for which reason they play a decisive role in the atmosphere and climate. 

The study by the Max Planck Institute for Marine Microbiology, in Germany, maintains that they are capable of removing up to 0.55 gigatonnes of carbon dioxide per year.

The study carried out by researchers from the Max Planck Institute for Marine Microbiology, in Germany, has been published in the journal "Proceedings of the National Academy of Sciences" (PNAS), and according to their conclusions, brown algae can remove large amounts of carbon dioxide of carbon from the global cycle in the long term and thus counteract global warming. Up to 0.55 gigatonnes of carbon dioxide per year, the publication maintains.

Researchers at the Max Planck Institute for Marine Microbiology in Germany now report that brown algae can remove large amounts of carbon dioxide from the global cycle in the long term and thus counteract global warming.

They use CO2 to grow

The algae absorb carbon dioxide from the atmosphere and use it to grow. They release up to a third of the carbon they absorb into seawater, for example in the form of sugary excretions. Depending on the structure of these excretions, they are quickly used by other organisms or sink to the seabed.

"Excretions from brown algae are very complex and therefore incredibly difficult to measure," explains first author Hagen Buck-Wiese of the Max Planck Institute. "However, we have managed to develop a method to analyze them in detail."

Using this method, the researchers examined a large number of different substances. The so-called fucoidan turned out to be especially interesting.

"Fucoidan made up about half of the excretions of the brown algae species we studied, the so-called bladderwrack," Buck-Wiese explains. "It's so complex that it's very difficult for other organisms to use it."

Carbon does not immediately return to the atmosphere

As a consequence, carbon from fucoidan does not quickly return to the atmosphere. "This makes brown algae especially good helpers in removing carbon dioxide from the atmosphere over the long term: hundreds or thousands of years," he adds.

Brown algae are extraordinarily productive. It is estimated that they absorb about 1 gigatonne (billion tons) of carbon per year from the air. Based on the results of the present study, this would mean that brown algae sequester up to 0.15 gigatons of carbon, equivalent to 0.55 gigatons of carbon dioxide, each year over the long term.

For comparison: Germany's annual greenhouse gas emissions currently amount to around 0.74 gigatonnes of carbon dioxide, according to the Federal Environment Agency (estimate for 2020).

"And even better: Fucoidan does not contain nutrients such as nitrogen," Buck-Wiese further notes. Therefore, the growth of brown algae is not affected by carbon losses.

For the current study, Buck-Wiese and colleagues from the MARUM MPG Bridge Group Marine Glycobiology, based at both the Max Planck Institute Bremen and the MARUM - Center for Marine and Environmental Sciences at the University of Bremen, conducted their experiments in the Tvärminne Zoological Station in southern Finland.

"Now we want to study other species of brown algae and other places," Buck-Wiese announces. "The great potential of brown algae for climate protection needs to be further investigated and harnessed."

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