In the Chesapeake Bay, saving seagrasses can fight ocean acidification

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When scientist Wen Jun Ca and his colleagues boated across the waters of the upper Chesapeake Bay, water sampling kits and pH sensors in hand, they didn’t expect to find chemical magic at play. The scientists were taking stock of a looming problem facing the 200-mile-long bay: the acidification of its waters, a human-caused phenomenon that threatens the health of the crabs, oysters, and fish iconic to the large estuary.

When they rounded up their hundreds of data points and analyzed them, they found evidence of something surprising and encouraging: Gently waving seagrasses in the bay are performing a magnificent chemical trick. As they photosynthesize in the beating sunshine, they produce tiny granules of a carbon-based mineral that acts like a miniature antacid tablet.

“It’s like the seagrasses are producing antacids that counter the indigestion of the bay,” says Jeremy Testa, a marine ecologist at the University of Maryland and an author of the paper in Nature Geoscience describing the newly discovered phenomenon.

Without this acid-neutralizing trick, the bay’s waters and shelled creatures would be even more vulnerable to the human-caused threats, he says.

The Chesapeake gets its name from the Algonquin word for "great shellfish bay." For thousands of years, its rich ecology depended on the ways its shellfish, grasses, fish, and other species interacted; each influenced the chemistry and biology of the others, in a delicate biological dance.

Seagrasses and other underwater plants packed the bay’s shallows, stilling and smoothing the surrounding water, leaving it clear and clean for baby fish, crabs, and shellfish to populate.

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