What’s in the Mud: Seagrasses Store 10% of Ocean’s Carbon

seagrass in Madagascar

A seagrass meadow in Madagascar's Vohemar Bay. (© Keith Ellenbogen/iLCP)

Off the Mediterranean coast of Spain, a green sea turtle (Chelonia mydas) gracefully glides over a seagrass bed, chomping a large green bite before the current swiftly takes him to the next patch of grass. Off the coast of Australia, schools of fish weave between the blades, hiding from predators and feeding on algae.

And then, off the Mid-Atlantic coast of the U.S., there’s me: an ungraceful human dragged by the salty current of a murky low tide. Unlike the sea turtle or school of fish, who are at home in the sea, I bob desperately; trying to decide which types of seagrass I will pull up and stuff in the mesh bag around my neck.

Last week, I traveled with three of my CI colleagues to volunteer with a seagrass restoration effort led by The Nature Conservancy (TNC), the Virginia Institute of Marine Science, and others — the largest project of its kind in the world. We snorkeled in Virginia’s South Bay for the afternoon, pulling up seagrass shoots and spades from the mud and hauling them back to shore, where TNC and its partners are raising seagrasses to plant in the fall. This is a massive project that has restored several thousand acres of eelgrass in four bays over 15 years.

CI staff at seagrass restoration project in Virginia

CI's Ginny Farmer, Ashton Jones, Laure Katz and Sarah Hoyt pause for a photo during a seagrass restoration project in Virginia organized by The Nature Conservancy. (Photo courtesy of Sarah Hoyt)

That afternoon, I learned the importance of seagrasses to the local marine life: these eelgrass beds are significant to bay scallops, fish, crabs, clams and other marine organisms. I also knew from my work with CI’s Marine division that seagrasses help filter ocean water for pollutants and protect coasts against floods and storms.

Listening to TNC project leaders talk about all the wonderful ecosystem services of seagrasses, I felt compelled to mention another important service: carbon storage.

Last week, a new study was published confirming that seagrass meadows have the ability to sequester carbon from the oceans and store it in their soils, helping to mitigate global climate change. Beneath the water, carbon accumulated over thousands of years lies locked in the mud.

This new study, “Seagrass Ecosystems as a Globally Significant Carbon Stock,” is the first global analysis of carbon stored in seagrasses and estimates that, although seagrass meadows occupy less than 0.2 percent of the world’s oceans, they are responsible for more than 10 percent of all carbon buried annually in the ocean. Not only that — but they bury carbon in their soils for thousands of years! I got to thinking of all the carbon storage potential of the eelgrass beds I was helping to create.

Many authors and contributors to this new research are expert scientists with the Blue Carbon Initiative — a collaborative effort led by CI, the International Union for Conservation of Nature, and the Intergovernmental Oceanic Commission of UNESCO. This initiative is the first program focused on mitigating climate change through the conservation and restoration of coastal “blue carbon” ecosystems, such as seagrasses, mangroves and salt marshes.

It seems that many initiatives around the world — including those close to home — are working hard to protect these ecosystems for their myriad benefits. No matter what the reason, it’s great to see that so many people are taking care of our coastal marine ecosystems, as they are so vital to our global climate health.

Sarah Hoyt is the executive coordinator for CI’s Global Marine division. Learn more about the Blue Carbon Initiative.


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  4. Tim Upham says

    For a long time, they were just seen as essential food for green sea turtles and dugongs. But now it has been expanded to how essential they are for crustaceans and molluscs. They also mitigate climatic change by storing carbon, and fish can hide from predators in the blades of grass, and feed on algae there. They are just as essential as mangrove forests.


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