Brown algae take up large amounts of carbon dioxide from the air and release parts of the carbon contained therein back into the environment in mucous form. This mucus is hard to break down for other ocean inhabitants, thus the carbon is removed from the atmosphere for a long time, as researchers now show. They reveal that the algal mucus called fucoidan is particularly responsible for this carbon removal and estimate that brown algae could thus remove up to 550 million tons of carbon dioxide from the air every year -- almost the amount of Germany's entire annual greenhouse gas emissions.