“Let’s meet in Bodega Bay,” the seagrass researcher suggested. It wasn’t until I saw him waving from thigh-high waters that I realized he literally meant in the bay. Since that soggy first encounter, I’ve acquired both waterproof waders and a deep respect for an overlooked, underappreciated and vitally important marine habitat. Seagrass may, in fact, be a silent savior of the ocean—and the planet.
The only flowering plant that makes its home underwater, seagrass (unlike seaweed, a type of algae) has roots, stems, leaves and a vascular system for transporting nutrients. Like its terrestrial ancestors, it photosynthesizes, using light to convert carbon dioxide into oxygen and energy-rich sugars. More than seventy species grow along the rims of every continent except Antartica; the most common on North American coasts is eelgrass.
Like forests and prairies, submerged meadows teem with life, providing nurseries, shelter and food for an array of ocean citizens, including crustaceans, mollusks and fish, as well as sustenance for migrating and wintering birds, ducks and geese. Long, flat, slimy-to-the-touch blades of seagrass—rising two to three feet high–also filter pollutants, absorb toxic metals and oxygenate the water column. Their sturdy root systems trap sand, stabilize sediment, buffer against surging waves and reduce coastal erosion.
Seagrass’s most remarkable and critical superpower may be its ability to capture carbon—far faster and in greater amounts per unit area than a tropical rainforest. Although its meadows cover less than 0.1 percent of the seafloor, they account for 10 to 18 percent of the carbon stored in the sea.
Why does this matter? The ocean, our planet’s “blue lung,” supplies at least half of the oxygen we breathe. Since the Industrial Age began in the late 19th century, carbon dioxide in the atmosphere has increased exponentially, raising seawater temperatures and acidity and lowering the ocean’s ability to produce oxygen.
“We need seagrass more than ever,” says Alyssa Griffin, Ph.D., director of the Coastal Health and Nearshore Geochemistry Lab at the University of California, Davis Bodega Marine Laboratory and Reserve. “To prevent catastrophic climate change, we have to do more than cut emissions—although this remains essential. We also must remove carbon from the atmosphere and sequester it for as long as possible.”
Among the most efficient and effective “blue carbon sinks,” seagrass traps carbon in its stalks and roots and in the surrounding sediment, where it can remain for centuries. Its green groves also exert a “halo effect,” lowering the acidity of nearby waters and buffering the impact of climate change.
Yet seagrass itself is imperiled. Since 1879, about thirty percent of the world’s seagrass meadows have been lost and their stored carbon released back into the atmosphere. Every year, coastal development, pollution, dredging and other threats destroy approximately 1.5 percent of the remaining seagrass beds. The equivalent of two football fields of seagrass disappears every hour.
This unsung environmental hero has rarely been recognized for its outsized contributions. ”To raise awareness at all levels,” the United Nations has designated March 1 as World Seagrass Day. You can find more information and ways to help at organizations such as the Ocean Foundation’s Seagrass Grow Program, the Marine Conservation Institute and the Nature Conservancy’s Blue Carbon Initiative.
Here’s a final fun fact about the seagrass sonata: During photosynthesis, the blades generate very small bubbles of oxygen that grow and grow as they float up the water column. When they finally burst, they make a sound that divers compare to the tinkling of tiny bells. This serenade benefits not only citizens of the sea but all who breathe, above and below the waves—yet another reason to celebrate the splendors of seagrass.
