Tiger sharks helped discover the world’s largest seagrass prairie

Scientists have collaborated with tiger sharks to discover the world's largest expanse of seagrasses.

Tiger sharks outfitted with cameras (such as the one shown here) assisted researchers in mapping the world's largest seagrass ecosystem. FOR BENEATH THE WAVES, DIEGO CAMEJO

A massive survey of the Bahamas Banks — a cluster of underwater plateaus surrounding the Bahamas archipelago — uncovered 92,000 square kilometers of seagrasses, according to marine biologist Oliver Shipley and colleagues in Nature Communications on November 1. That territory is roughly half the size of Florida.

According to Shipley of the Herndon, Va.-based ocean conservation nonprofit Beneath The Waves, the discovery increases the estimated global area covered by seagrasses by 41%, which could benefit Earth's climate.

Austin Gallagher of ocean conservation nonprofit Beneath The Waves surveys a seagrass field in the Bahamas Banks. SEALEGACY AND CRISTINA MITTERMEIER

Austin Gallagher of ocean conservation nonprofit Beneath The Waves surveys a seagrass field in the Bahamas Banks.

Seagrasses can sequester carbon at a rate 35 times faster than tropical rainforests over millennia. According to the team, the newly mapped sea prairie could store 630 million metric tons of carbon or roughly a quarter of the carbon trapped by seagrasses worldwide.

According to Shipley, mapping that much seagrass was a monumental task. He and his colleagues dove into the sparkling blue waters 2,542 times to survey the meadows up close, guided by previous satellite observations. The team also enlisted the help of eight tiger sharks. Sharks patrol fields of wavy seagrasses for grazing animals to eat, similar to how lions stalk zebra through tall grasses on the African savanna (SN: 12918; SN: 5/ 21/ 19, SN: 21617).

"Without the assistance of tiger sharks, we would not have been able to map anywhere near the extent that we did," Shipley says.

The sharks were captured using drumlines and hauled onto a boat, where they were fitted with a camera and tracking device before being released. The sharks were usually back in the water in less than ten minutes. According to Shipley, the team operated like a "NASCAR pit crew."

Previously, researchers proposed tracking seagrass-grazing sea turtles and manatees to locate pastures. Tiger sharks, on the other hand, were a wise choice because they roam further and deeper, according to Marjolijn Christianen, a marine ecologist at Wageningen University & Research in the Netherlands who was not involved in the new research. "That's a benefit."

Tiger sharks equipped with cameras, such as this one, assisted in the discovery of the world's largest seagrass bed, penetrating areas too deep or remote for divers.

Shipley and colleagues intend to work with other animals, such as ocean sunfish, to discover more submarine meadows (SN: 5115). "With this approach," he says, "the world is our oyster."


A.J. Gallagher and colleagues Tiger sharks contribute to the understanding of the world's largest seagrass ecosystem. The journal Nature Communications. Vol. Page 6328, November 1, 2022. DOI: 10.1038/s41467-022-33926-1

G.C. Hays and colleagues Marine grazers as habitat indicators: new tools for locating seagrass meadows Marine Science Frontiers. Vol. February 5, 2018. doi: 10.3389/fmars.2018.0009

E. Mcleod and colleagues A Blue Carbon Roadmap: Towards a Better Understanding of the Role of Vegetated Coastal Habitats in CO2 Sequestration Ecology and the Environment at the Cutting Edge Vol. p. 552, January 20, 2011. doi: 10.1890/110004.


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