A Massive Seagrass Project Is Restoring a Lost Food Web for Wintering Geese

Robert Orth has a few nicknames. “Bob” and “JJ” are the more common, but to describe his work in the Chesapeake Bay for the past 20 years, one fits best: “The Gardener.” Orth, as a professor with the Virginia Institute of Marine Science, earned the moniker while spearheading a restoration project that more often requires a wetsuit than overalls and a trowel. His garden is entirely underwater.

In an October study published in Science Advances, Orth and a team of researchers from the institute detail the world's largest eelgrass restoration effort, situated in the southern Chesapeake Bay off the coast of Virginia. Their decades-long project has restored nearly 9,000 acres of eelgrass in a region where it was nearly extirpated while bringing back a once-lost food web to a wintering habitat for Atlantic Brant and other species.

Eelgrass, a type of submerged aquatic vegetation, is long and tubular and found in patches in tidal bays, resembling a swaying lawn of green spaghetti. These noodles are the foundation for fish habitats and waterfowl diets across the globe, and in the Chesapeake Bay, are part of an ecosystem making a comeback thanks in part to hands-on projects like this. 

Once found in abundance in coastal bays across the east coast, eelgrass coverage plummeted after a devastating plant disease and hurricanes in the 1930s decimated about 90 percent of the vegetation in the Atlantic. The clear water once cleaned by eelgrass became a more opaque and murky environment with little vegetation. Seed sources were washed out of their habitats, making recovery difficult across its range. Natural restoration was perhaps the hardest in the Chesapeake Bay, where narrow entrances to suitable sites precluded any seeds from taking hold. When Orth and others initially sought ways to restore eelgrass in the bay, marine scientists had low expectations. “The hypothesis was that, well, you know these bays are shallow, they’re muddy, maybe there was an ecosystem state change and these grasses would never come back,” Orth says. 

Knowing the value of that former ecosystem, Orth, with the help of employees, volunteers, and funding from conservation groups in the region, found a few errant patches of eelgrass remaining and began to harvest and spread seeds in the late 1990s, testing how the eelgrass would grow.

Over 20 years, the test regions expanded as the team collected and spread more than 70 million seeds. As the bays took on more eelgrass, the tides started helping to spread seeds as well, a sign of sustainable growth. “We tried out this idea, and ended up recovering a lot of eelgrass thanks in large part to what nature does best,'' Orth says. “It was that simple.”

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Over 20 years, the test regions expanded as the team collected and spread more than 70 million seeds. 
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The resurgence of eelgrass in the Chesapeake, so far seen in four bays along the Eastern Shore of Virginia, could increase the area's viability as a major Brant wintering habitat—the more food available, the more stable a wintering location becomes. 

“It’s hard to come up with any bird species that’s more tied to eelgrass than Brant,” Ted Nichols, a wildlife biologist with the New Jersey Division of Fish and Wildlife, says. Nichols is in the midst of a study on Brant in their primary wintering habitat today, the coastal bays of New Jersey and Long Island, New York, and has seen how a reduction in eelgrass can fluctuate the entire species’ population. “We had a few real brutal winters in the late 1970s, and that led to a massive die-off for birds,” Nichols says. “Brant really had no access to eelgrass and a lot of them starved to death and the population plummeted.”

Along the eastern seaboard, the species once relied on eelgrass for more than 80 percent of its diet but shifted to sea lettuce and other macroalgae as its preferred vegetation disappeared. While this food flexibility helped recover the population, eelgrass provides a richer, energy-dense diet than macroalgae. “Algae is the easiest thing for them to access,” Chase Colmorgen, a biologist with Ducks Unlimited in the Chesapeake Bay region, says. “I think ultimately, if the habitat is there, and it improves, I think they would switch back.” 

An increase in eelgrass doesn’t just make for a reliable wintering habitat for Brant—some populations of other wintering waterbirds have benefitted greatly from seagrass recovery in the bay. Bird surveys in Maryland found dramatic increases in Tundra Swans and Redhead ducks in the winter months since the mid-1980s that mirror an increase in submerged aquatic vegetation in coastal bays. Despite the encouraging results of other waterfowl, researchers aren’t certain yet about the effects of this eelgrass restoration on the Chesapeake's Brant populations. With the majority of wintering Brant flocking to New York and New Jersey bays, population and health studies tend to focus on those areas. While the future may offer more research opportunities to study the Chesapeake's wintering population, Colmorgen notes that a recovered ecosystem is undoubtedly beneficial for the birds. “With restoration ramping up, eelgrass being more plentiful is going to go a long way for [Brant],” Colmorgen says. 

As for the eelgrass project, Orth says the team plans to continue seed spreading and potentially even restore a sizeable habitat for bay scallops, another species reliant on eelgrass beds. It would be an important step toward fully restoring a food web now nearly a century gone. “It's a pretty rich ecosystem,” Orth says, “and we're pretty excited about the fact that we were able to accomplish something that no one had ever expected to see.”