The grassy meadows (ocean or seagrass meadows) found on the bottom of the oceans could be gigantic sugar stores. According to a study recently published in the journal Nature Ecology & Evolution , seagrasses could be accumulating up to 1.3 million tons of sucrose worldwide. This, so that we understand each other, would serve to sweeten about 32,000 cans of sugary soft drink.
Sugar comes in the form of sucrose, which is the main ingredient in the sugar we use in cooking, and it is released from seagrass beds into the soil below, an area directly affected by roots, known as the rhizosphere. This means that sugar concentrations on the seabed are about 80 times higher than normal.
“Seagrasses produce sugar during photosynthesis,” explains Nicole Dubilier, a marine microbiologist who participated in the study, from the Max Planck Institute for Marine Microbiology in Germany. “In medium light conditions, these plants use most of the sugars they produce for their own metabolism and growth. But in high light conditions, for example at midday or during the summer, the plants produce more sugar than they can handle.” use or store. Then they release excess sucrose into their rhizosphere. Think of it like an overflow valve.”
What is surprising is that this excess sugar is not absorbed by the microorganisms in the environment . To prevent this, it appears that seagrasses release phenolic compounds in the same way that many other plants do. These chemical compounds are also found in red wine, coffee, and fruit, as well as many other places in nature. They are antimicrobial, so they inhibit the metabolism of most microorganisms, slowing them down.
The researchers tested their hypothesis in a real underwater seagrass field to confirm that this was the case, using a mass spectrometry technique. “In our experiments we added phenolics isolated from seagrass beds to microorganisms in the rhizosphere of seagrass beds,” explains marine microbiologist Maggie Sogin, from the Max Planck Institute for Marine Microbiology, who has also participated in the research. “And sure enough, much less sucrose was consumed compared to when there were no phenolics .”
A small group of microbes thrived on sucrose despite the presence of phenolics. The researchers believe that these “microbial specialists” may be giving something back to the seagrass in return, such as the nutrients it needs to grow.
Seagrass beds are one of the most important sinks of blue carbon (carbon captured by the world’s ocean and coastal ecosystems) on the planet, and an area of seagrass beds can absorb twice as much carbon as a forest of the same size, and in addition 35 times faster.
When calculating the loss of carbon sequestration from seagrass meadows, which are among the most threatened habitats on the planet due to human activity and declining water quality, scientists can now account for deposits of sucrose, in addition to the seagrass beds themselves.
“We don’t know as much about seagrass meadows as we do about terrestrial habitats,” says Sogin. “Our study contributes to our understanding of one of the most critical coastal habitats on our planet, and highlights how important it is to preserve these high-carbon ecosystems.” blue,” says the researcher.
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Reference:
Sogin, E.M., Michellod, D., Gruber-Vodicka, H.R. et al. 2022. Sugars dominate the seagrass rhizosphere. Nat Ecol Evol. DOI: https://doi.org/10.1038/s41559-022-01740-z
