Scientists have made a fascinating discovery: seagrass meadows beneath the ocean store colossal reserves of sugar. Seagrasses are the only flowering plants that grow in marine environments and are essential to coastal areas worldwide. They are carbon storage powerhouses, with one square kilometer of seagrass storing nearly twice as much carbon as land-based forests, and 35 times faster.

Seagrass meadows: carbon storage powerhouses and unique ecosystems

A study published in the journal Nature Eco­logy & Evol­u­tion by researchers from the Max Planck Institute for Marine Microbiology in Bremen, Germany, revealed that seagrasses release huge amounts of sugar into their soils, known as the rhizosphere. This sugar is produced during photosynthesis, with most of it used for the plants’ metabolism and growth. However, under high light conditions, excess sucrose is released into the rhizosphere.

This finding is significant as seagrasses hold roughly 32 billion cans of Coca-Cola’s worth of sugar hidden in the seabed. The sugar concentration is unexpectedly at least 80 times higher than previously measured in marine environments. Manuel Liebeke, the head of the Research Group Metabolic Interactions at the Max Planck Institute for Marine Microbiology, explained that there are approximately between 0.6 and 1.3 million tons of sugar worldwide in the seagrass rhizosphere, mainly in the form of sucrose, comparable to the amount of sugar in 32 billion cans of coke!

High concentrations of sugar found in the seagrass rhizosphere

The researchers were also puzzled about why sucrose is stored in the seabed rather than being consumed by microorganisms in the rhizosphere. The reason is that seagrass, like many other plants, releases phenolic compounds to their sediments. Phenolics are antimicrobials and inhibit the metabolism of most microorganisms. When phenolics isolated from seagrass were added to the microorganisms in the seagrass rhizosphere, much less sucrose was consumed than when no phenolics were present.

Seagrass meadows are essential coastal habitats that are among the most threatened on Earth. Although they are carbon storage powerhouses, they are disappearing at an alarming rate, with annual losses of up to seven percent in certain areas. Even though seagrass meadows help with our climate woes, they are also at risk of losing stored carbon. Seagrasses can store carbon for millennia, while rainforests do so for decades.

Looking at how much blue carbon (carbon captured by the world’s ocean and coastal ecosystems) is lost when seagrass communities are decimated, researchers found that it is not only the seagrass itself but also the large amounts of sucrose underneath live seagrasses that would result in a loss of stored carbon. If the sucrose in the seagrass rhizosphere was degraded by microbes, at least 1.54 million tons of carbon dioxide would be released into the atmosphere worldwide, equivalent to the amount of carbon dioxide emitted by 330,000 cars in a year.

The study highlights the sheer importance of seagrass meadows and how vital it is to preserve these blue carbon ecosystems. As Maggie Sogin, the study’s first author, remarked, “We do not know as much about seagrass as we do about land-based habitats.” Seagrass meadows are crucial for mitigating climate change, and their disappearance could have devastating consequences. The loss of these habitats could result in a massive release of stored carbon, leading to more carbon dioxide emissions and contributing to global warming.

In conclusion, the discovery of the sugar reserves hidden beneath seagrass meadows is a significant find that has implications for mitigating climate change and carbon storage. Seagrass meadows are essential coastal habitats that help with our climate woes, but they are disappearing at an alarming rate.