Seagrass plays an important role in our climate. They are one of the most efficient carbon dioxide sinks in the world. A team of scientists from the Max Planck Institute for Marine Microbiology now reports that seaweed releases large amounts of sugar, especially sucrose, in their soil – worldwide more than one million tons of sucrose, enough to 32 billion cans of coke. . Such a high level of sugar is amazing. Usually, microorganisms eat up any free sugar in their area. Scientists have discovered that seaweed releases phenolic compounds, and these prevent many microorganisms from damaging sucrose. This ensures that sucrose remains buried under the marshes and cannot be converted to CO2 and returned to the oceans and atmosphere. They now describe their findings in the journal Nature Ecology & Evolution.
Sea grasses form green meadows in many coastal areas around the world. These marine plants are one of the most effective ways to absorb carbon dioxide worldwide: One square mile [1 sq km] of seawater retains twice as much carbon as the earth’s forests, and quickly 35 times. Now scientists at the Max Planck Institute for Marine Microbiology in Bremen, Germany, have discovered that seaweed releases large amounts of sugar into their soil, called the rhizosphere. The level of sugar under the seagrass was about 80 times higher than previously estimated in the seas. “To understand this: We estimate that worldwide there are between 0.6 and 1.3 million tons of sugar, mainly in sucrose, seaweed,” explains Manuel Liebeke, head of the Metabolic Interactions Research Group at Max Planck Institute of Marine Microbiology. “That ‘s almost equal to the amount of sugar in 32 billion cans of coke!”
Polyphenols keep bacteria from eating sugar
Germs like sugar: They are easy to digest and full of energy. So why should sucrose not be consumed by a large community of microorganisms in the seagrass rhizosphere? “We’ve spent a lot of time trying to find this out,” said first author Maggie Sogin, who led research on the Italian island of Elba and the Max Planck Institute for Marine Microbiology. “When we realized that seaweed, like many other plants, releases phenolic compounds in their plant. Red wine, coffee and fruit are full of phenolics, and many people consider it a health ingredient. Little is known that phenolics are antibacterial drugs.” -phenolic is separated from seagrass to insects in the seagrass rhizosphere – and indeed, very little sucrose was consumed compared to when there was no phenolics. “
Some experts thrive on sugar in the seagrass rhizosphere
Why does seaweed produce such large amounts of sugar, and then dump it into their rhizosphere? Nicole Dubilier, Director of the Max Planck Institute for Marine Microbiology explains: “Seagrass produces sugar during photosynthesis. Under normal light conditions, these plants use more of the sugar they produce to work and grow. But under conditions of high light, for example. during the summer, the plants produce more sugar than they can use or store. Then they release more sucrose into their rhizosphere. Think of it as a dense valve. “
Interestingly, a small set of microbial specialists are able to thrive in sucrose despite challenging conditions. Sogin speculates that these sucrose experts can not only digest sucrose and destroy phenols, but may also provide benefits to seaweed by producing nutrients needed for growth, such as nitrogen. “Such beneficial relationships between plants and rhizosphere microorganisms are well known in the world’s vegetation, but we are still beginning to understand the deep and complex interactions of seaweed and microorganisms in the marine rhizosphere,” he adds.
Dangerous and critical settlements
Marine swamps are among the most endangered in our world. “Considering how much blue carbon – which is carbon dioxide and coastal ecosystems – is lost when marine communities are depleted, our research clearly shows: Not only marine vegetation itself, but also large amounts of sucrose. Our statistics show that if “Sucrose in the seagrass area is depleted of bacteria, and at least 1.54 million tons of carbon dioxide can be released into the atmosphere worldwide,” Liebeke said”That’s about the amount of carbon dioxide emitted by 330,000 cars a year.” Marine vegetation is declining rapidly in all oceans, and annual losses are estimated to rise by 7% in some areas, compared with the loss of coral reefs and rain forests. About a third of the world’s marine grasses may already be lost. “We do not know as much about seaweed as we do about the habitat of the earth,” Sogin emphasizes. “Our research contributes to our understanding of one of the world’s most critical coastal areas, and highlights the importance of conserving these areas of blue carbon.”
Source Journal Reference: Sogin, E.M., Michellod, D., Gruber-Vodicka, H.R. et al. Sugars dominate the seagrass rhizosphere. Nat Ecol Evol, 2022 DOI: 10.1038/s41559-022-01740-z
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