CRAMMED IN WIRE CAGES on a Duxbury mudflat, the life of an Island Creek oyster is humble and predictable. Destined for a restaurant menu, nothing in their upbringing would indicate that these delicious bivalves might one day fulfill another purpose as the unsung hero of Massachusetts' coastal clean-up efforts.
An Island Creek oyster's journey begins at the farm's on-site hatchery, where they are bred and spawned from a carefully selected stock of adult shellfish. These spat — juvenile oysters the size of a grain of sand — spend their first months in giant buckets before moving on to a tank-like machine called an upweller. There, they will receive water and food constantly before being loaded into floating mesh bags and placed in the bay for their first taste of the open ocean. In just a few months, the oysters will possess their characteristic brown shells and briny meat, prepared to live out their adulthood in cages further away from the shore.
When they finally reach market size after about two years, they will be lifted from their underwater homes, tested for quality and packaged with hundreds of their relatives. The shellfish will be sent to restaurants in Boston, where a happy customer will enjoy them shucked and raw, accompanied by a side of vinegar and horseradish. But these oysters aren't just a local delicacy; they're environmental powerhouses, too. Scientists believe that cultivating these shellfish may offer the key to long-term water quality management, especially in communities like Cape Cod, where coastal water pollution has become a pressing concern.
"Our coastal waters are being inundated with excess nitrogen," says Dan Rogers, a biochemist and professor at Stonehill College. Nitrogen, although essential to a well-functioning ecosystem, can be harmful in too high quantities, leading to events like algae blooms and health risks for people living nearby. It's caused primarily by runoff from coastal development, fertilizers used in farming and, in Cape Cod's case, improper septic infrastructure.
In Nov. 2022, the Massachusetts Department of Environmental Protection , or MassDEP, proposed extending current regulations to require residents near the coast to trade in their septic systems for nitrogen-filtering options. The transition would be expensive — one repair can cost between $17,000 and $36,000, according to MassDEP — and scientists argue that replacing septic systems is not the only possible solution.
SINCE 2017, at an experimental oyster farm in East Falmouth's Waquoit Bay National Estuarine Research Reserve&mdashone of the areas most impacted by excess nitrogen—Rogers has been cultivating oysters in a way that models a commercial farm. His studies have shown that oysters can be an effective way to remove excess nitrogen in coastal waters. It's not just cultured oysters that can do this job. Wild or native oysters are master water cleaners, too.
Crassostrea virginica, the eastern or Atlantic oyster, is a filter feeder — when it takes in water to eat, it uses its gills to sort through particles, absorbing what it needs and expelling the rest. This process is something oysters are naturally designed to do, and expertly at that. Research from the Chesapeake Bay Foundation shows that a single oyster can filter 50 gallons of water a day. When that number is multiplied to reflect the real number of shellfish found on a farm, Rogers says the impact is even greater.
"They grow with hundreds of thousands of their closest friends," he says. "So, you can see how it scales up quite rapidly."
Nitrogen is a crucial ingredient in an oyster's shell and muscle. Absorbing it through filter feeding is one way they manage to keep their estuaries clear. Vivian Mara is a marine microbiologist at the Woods Hole Oceanographic Institute, and a colleague of Rogers' on the Waquoit Bay project. She says that by consuming nitrogen and excreting compounds called nitrates, oysters foster the perfect conditions for certain bacteria to thrive. Over time, these bacteria will take in excess nutrients, creating a healthy ecosystem for other wildlife.
The results have been promising; data collected by the researchers in a 2021 study points to significant denitrification thanks to the oysters in the area, as well as changes in the genetic ability of other life in the ecosystem to regulate nitrogen. The research is made easier by the fact that oysters take well to these waters. After all, they are native to the area and were once so plentiful that they were said to present a hazard to sailors navigating Massachusetts Bay.
TODAY, THE NUMBER OF OYSTERS in the wild is drastically smaller, which poses a challenge for those relying on them for their cleaning power. In one study published in "BioScience," experts from The Nature Conservancy estimate that nearly 90% of native oyster populations globally have disappeared. In the shallow waters off the coast of Massachusetts, this loss has been tremendous. Surveys of local estuaries have found that less than 6% of wild oyster populations remain.
Like with coral reefs, the effect of climate change on oceans, primarily the acidification and increased temperature of coastal waters, plays a big part in that. But those in the business of oyster growing note that human interactions with oyster ecosystems are equally at fault for the decrease in wild populations.
"The two main drivers for the loss of wild oyster populations have been overharvesting [by] wild harvesters… coastal development and the changes to the water chemistry that coastal development drives," says Chris Sherman, CEO of Island Creek Oysters.
Oysters' ability to remove harmful nitrogen from the ecosystem hinges on a thriving population. Across the Bay State, non-profit organizations are working to restore wild populations while supporting the local aquaculture industry. Theresa Baybutt is the president of the Massachusetts Oyster Project, also known as Mass Oyster. Powered by donations and a network of volunteers, her team cultivates oysters on reefs made partially of recycled shells to revitalize the wild oyster population, educating the community on the importance of native shellfish while doing it.
"If they survive, they can reproduce rapidly," she says. "One oyster spawns a million seeds, so if the substrate area where you're putting your oysters down allows for the spawning spat to settle, then the potential for growing is really great."
Baybutt estimates that the organization has introduced at least two million oysters back into the ecosystem, but the actual number of oysters growing in the wild where Mass Oyster operates is likely much larger. And they aren't the only group making an impact. Baybutt's work is part of a collaborative effort which includes state-level initiatives like the Massachusetts Bays National Estuary Partnership and programs like the National Oceanic and Atmospheric Administration's Sea Grant.
Organizations like these are making a major dent in the oyster population problem, but Baybutt notes that oysters cultivated in aquaculture businesses like Island Creek are just as effective in cleaning marine ecosystems and keeping oyster populations alive. "Because of the amount of oysters that are in [Duxbury Bay]," she says, "the entire bay filters every nine days."
This is why it's important for consumers to eat local shellfish, aquaculturists say. Choosing local oysters doesn't just pay the bills for farmers and small businesses; it also helps ensure that coastal ecosystems in the region are better off.
"We take a use it or lose it approach to environmentalism here," Sherman says about Island Creek. "We find that through our use and participation out in the marine environment, in estuaries here in Duxbury but also with all the other growers we work with, it really builds the value of that environment and the consciousness of the environment in the communities."
BACK IN WAQUOIT BAY, Rogers and Mara continue to study oyster cultures, hoping to build a model that communities across the state can implement for their own nitrogen cleanup projects. But Rogers cautions that oysters are only one part of the solution.
"We tend to focus on these single solution pathways because that's easy for us to think about — and that's not how the environment works," he says. "It does not deal with the problem of actually introducing the nutrients into the water, and that's what we need to take care of—hthe sources. Then, oysters might have a role in fixing what we've already done, restoring it to what it should be."
Produced by students at the Northeastern University School of Journalism. © 2023
