Seagrass bubble sounds can be used to measure carbon storage

In coastal waters, hidden beneath the surface, seagrasses quietly play a vital role. They trap carbon dioxide more efficiently than tropical rainforests, acre for acre.

Professor Ken Dunton, a marine biologist at UT Austin, has spent decades studying these coastal meadows. He noted that most of the biomass of a seagrass plant is below ground. “That’s where all the tissues store carbon.”

The carbon is stored in roots and rhizomes buried in sediment. This makes seagrasses natural carbon banks, especially useful in a world heating up from excess atmospheric carbon.

Measuring seagrass carbon

To harness the carbon storage power of seagrass, we need accurate ways to measure it. Right now, measuring how much carbon seagrasses trap takes time and labor.

Researchers must dig up sediment, haul it to a lab, and analyze it. It is expensive and cannot scale easily.

But there’s good reason to want that data. Knowing how much carbon each seagrass bed stores could influence how governments and businesses manage these ecosystems. In the future, they might even earn carbon credits for maintaining or restoring seagrass meadows.

A simpler method emerges

With help from ARPA-E, Dunton and engineering professor Preston Wilson are trying something novel. They’re listening to bubbles. As seagrasses photosynthesize, they release oxygen, some of which forms bubbles. More bubbles mean more photosynthesis and more carbon storage.

“So just like us in air, if I breathe out… you can hear me. Well when the seagrass breathes out under water, it makes bubbles, and the bubbles make noise,” Wilson explained.

This noise offers a clue. With underwater microphones, called hydrophones, scientists can record these tiny bubble sounds. Then, they use sound levels to estimate how much carbon the seagrasses are locking away.

Collecting mud to test a new idea

At East Flats near Port Aransas, Texas, the research team works waist-deep in water. They collect sediment cores using a tool called a vibracore. It takes several people to push a long plastic tube into the mud and pull it back up.

Once back at the lab, the team slices these cores into hockey puck-sized disks. Each disk undergoes detailed analysis, acoustic scanning, drying, grinding, burning, and chemical testing. These methods reveal how much carbon each layer holds.

“What we want to learn out of these cores is: ‘What are the relationships between organic carbon in the sediment and the acoustic properties of the sediment?’” said Kevin Lee, from UT’s Applied Research Laboratories.

Bubble sounds and seagrass carbon

The lab work helps link bubble sound levels to carbon content. The sound profile of each core becomes a blueprint. Over time, scientists will calibrate models that predict carbon levels from sound alone.

It is like tuning a sensor. If a certain sound intensity equals a known amount of carbon, then future recordings can be read like a meter, with no digging needed.

“And to make a market, you need a meter. We would be the meter in a future global carbon market,” noted Professor Wilson.

Tracking global carbon storage

The ultimate goal of the research is to create low-cost hydrophone systems. These can stay underwater and record data continuously. The recordings could then be sent to computers onshore.

Study co-author Megan Ballard envisions a time when no one will need to visit the site just to check data.

“The whole goal of the project is to develop a low-cost network of sensors. We imagine something that can telemeter data back to shore,” said Ballard.

This would save time, reduce costs, and open the door to tracking carbon storage on a global scale.

Seagrass and the future of carbon markets

Imagine a future where a company restores a seagrass bed and gets credit for every ton of carbon stored. That future needs tools. Dunton, Wilson, and their team are building one, quietly listening to nature’s own signals.

The research might soon turn seagrasses into verifiable, scalable allies in the fight against climate change. Hidden under the waves, a bubbling meadow might someday power a carbon market.

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