The researchers found that brown seaweed could remove carbon in the long term.
“The excretions of brown algae are very complex and therefore incredibly complicated to measure,” said lead author, Hagen Buck-Wiese from the Max Planck Institute for Marine Microbiology, in a press release. “However, we have managed to develop a method to analyze them in detail.”
The scientists scrutinized a large number of different substances found in the algae and discovered that the algae mucus fucoidan was particularly effective in carbon removal.
“Fucoidan made up about half of the excretions of the brown algae species we studied, the so-called bladderwrack,” said Buck-Wiese. “The fucoidan is so complex that it is very hard for other organisms to use it. No one seems to like it.”
This is why the CO2 from the fucoidan does not return back to the atmosphere fast, which could mean that the brown seaweed could store carbon dioxide for hundreds to thousands of years, Buck-Wiese said.
According to estimates, brown algae absorb approximately one gigaton (one billion metric tons) of CO2 annually. The results of the new study indicate that brown algae could sequester as much as 0.15 gigatons per year in the long term.
The fucoidan does not contain any nutrients such as nitrogen, and thus the growth of the brown seaweed is not affected by CO2 losses, Buck-Wiese said.
The experiments of the study were conducted at the Tvärminne Zoological Station in southern Finland.