(ORDO NEWS) — Hidden beneath the waves, the ocean holds huge reserves of sugar we didn’t even know we had, according to new research.
Scientists have discovered that seagrass meadows on the ocean floor can store vast amounts of the sweet substance under their waving leaves – and this has serious implications for carbon storage and climate change.
Sugar comes in the form of sucrose (the main ingredient in sugar used in the kitchen) and is released from the sea grasses into the soil below them – the area directly affected by the roots, known as the rhizosphere. This means that the concentration of sugar in the seabed is about 80 times higher than normal.
Globally, sea grasses can contain up to 1.3 million tons of sucrose, according to the research team. In other words, that’s enough for about 32 billion cans of Coca-Cola, so we’re talking about a significant find of hidden sugar.
“Sea grasses produce sugar through photosynthesis,” says marine microbiologist Nicole Dubilier of the Max Planck Institute for Marine Microbiology in Germany.
“Under medium light conditions, these plants use most of the sugars they produce for their own metabolism and growth. But under high light conditions, such as at noon or summer, plants produce more sugar than they can use or store. Then they release excess sucrose into the rhizosphere. Think it’s an overflow valve.”
Surprisingly, this excess sugar is not devoured by microorganisms in the environment. To stop this, sea grasses seem to send phenolic compounds in the same way that many other plants do.
Found in red wine, coffee and fruits, and many other places in nature, these chemicals are antimicrobials that inhibit the metabolism of most microorganisms, slowing down their development.
The researchers tested their hypothesis on a real underwater seagrass field to confirm that this is indeed the case using a mass spectrometry method.
“In our experiments, we added phenolic compounds isolated from seagrass to microorganisms in the seagrass rhizosphere,” says marine microbiologist Maggie Sogin of the Max Planck Institute for Marine Microbiology.
“Indeed, much less sucrose was consumed than in the absence of phenolic substances.”
A small subset of microbes thrived on sucrose despite the presence of phenolics: the researchers think these “specialist microbes” may be giving something back to the seagrass, such as the nutrients they need to grow.
Seagrasses are among the most important sinks of blue carbon (carbon captured by the world’s oceans and coastal ecosystems): a patch of seagrass can absorb twice as much carbon as a forest of the same size on land, and 35 times faster.
When calculating the loss of carbon captured by seagrass meadows – one of the most threatened habitats on the planet due to human activities and declining water quality – scientists can now account for both sucrose deposits and the seagrasses themselves.
“We don’t know as much about seagrass as we do about terrestrial habitat,” says Sogin.
“Our study contributes to our understanding of one of the most important coastal habitats on our planet and highlights the importance of conserving these blue carbon ecosystems.”
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