Oysters are making a comeback on menus and in the water—for now

A 1913 issue of National Geographic called the Chesapeake Bay the “greatest oyster ground in the world,” declaring Baltimore its capital. The bay was once so densely populated by the eastern oyster, Crassostrea virginica, it’s said that the hulls of early European boats sailing up the Chesapeake were scraped by the shells. The oyster was a popular harvesting product in the mid-Atlantic more than a century ago. At the local oyster industry’s peak during the late 19th century, more than 20 million bushels of oysters were pulled from the Chesapeake Bay every year. In the decades that followed, oystermen harvested oysters faster than they could reproduce. They used large scraping tools to transform craggy reefs into muddy substrates that oysters couldn’t survive on.

By 2005, the National Marine Fisheries Service considered placing the eastern oyster on the endangered species list. Today, oyster populations are still less than one percent of their former numbers.

Climate change is a new threat. Climate change is being seen both as sudden and subtle changes. It is now settling in the Chesapeake with fingerprints from the sudden torrential rains and slowly changing ocean chemistry.

But the small and mighty bivalve is still making a comeback in the bay, the largest estuary in the United States.

This year, Maryland oyster fishers sold a half million bushels of wild oysters, the most since 1987, and in Virginia around half a million bushels have been consistently harvested annually since 2014, steadily ticking up from their record low in 1996, when just over 17,000 bushels came in. The bay has also seen a rise in aquaculture, which is the cultivation of oysters from farms.

In 1998, revenue generated by farmed oysters and clams in Virginia totaled around $10 million annually; in 2020 it was valued at over $30 million for oysters alone. Local environmental groups have an ambitious plan for restoring the reefs that once threatened ships, not only to support the oyster industry but also to improve the health of the bay. A single oyster can filter 50 gallons of water every day, removing pollution and improving water quality.

While the Chesapeake’s first oyster boom may have been a victim of human appetites, today’s oyster renaissance is being closely shepherded by human hands. “In Virginia, our oyster sector is doing really well. A lot of that is due to advances in aquaculture,” says Mike Schwartz, an oyster expert from Virginia Tech. “Keeping it growing and being sustainable is part of looking at climate change.”

Highlighting merroir

On a sunny summer afternoon, Patrick Oliver, Rappahannock Oyster Company’s director of farms, motors through rows of submerged oyster cages that bob just below the bay’s surface with the gentle current. He inspects ropes and knots to ensure that cages are secure. Oliver then ponders why the oyster is so beloved. “When it comes out the water, its heart beats… It’s dirty.” It’s primitive… It’s daring.”

Over the past 20 years, oysters have joined the ranks of wine and cheese as menu items for foodies. The Rappahannock’s tasting room on the shore is just a few hundred yards from the farm. Oyster enthusiasts from all over the region travel to the remote farm to enjoy raw oysters with a glass of bubbles. They purchase oysters by the case and wear Rappahannock-branded T-shirts and shucking knifes to show their loyalty to oysters.

One reason for this half-shell renaissance is that farmers market their raw oysters on restaurant menus like wine. Just as wine grapes can carry the terroir of the soils in which they grow, raw oysters have a signature merroir that reflects the water they grew in. Oysters are described as sweet, salty, buttery, or tender.

Oysters are also as trendy now as they were when they were slurped down in early 19th century New York city oyster cellars. Paired with a dirty martini, they were recently deemed by New York Magazine the “hot-girl meal of summer.”

And while the clever marketing has improved demand, genetic meddling helped guarantee supply from oyster farms.

In the wild, oysters spawn in the summer months. This snowstorm of eggs and sperm releases into the water. People are warned to avoid eating oysters in months without the letter R. This is because they can become thin and watery from the energy required to reproduce. The second reason is the public health risk of eating raw oysters before refrigeration and water quality testing.

But in the late 1990’s, scientists working at William and Mary’s Virginia Institute of Marine Science (VIMS) introduced a genetic mutant oyster for the bay by breeding one that doesn’t spawn. In the wild, the eastern Chesapeake oyster is a diploid. This means it has two sets chromosomes. However, scientists were able to create a triploid oyster by manipulating the breeding process. Triploids are infertile, created in a lab by crossing a wild female oyster with a farmed male one. They don’t shrink when they reproduce and can guarantee a steady supply of food for farmers all year. Farmers must be able to purchase triploid spat from growers who are experts in triploid spat. This is what baby oysters are called once they’re old enough that they can attach to a substrate. Over 90 percent of farmed Virginia oysters are triploids. One study even showed that triploids in the Chesapeake grew to market size almost a year faster than diploids, were more likely to survive, and yielded more meat.

Globally, aquaculture is a rapidly growing industry. An estimated 95 percent of all oysters consumed comes from farms, and the aquaculture industry is expected to provide two-thirds of the world’s seafood by 2030. Many of these farms raise finned shrimp or fish and expel fecal matter.

The bivalves are being promoted as a food of the future, a sustainable and clean product to invest in as the world’s oceans heat up and fish populations decrease.

Oysters use calcium carbonate to build their hard shells as they grow. The gray flesh inside contains their heart, stomach, intestines and stomach. If the oyster senses that water conditions are favorable, it relaxes one tiny adductor muscle and opens slightly. Sea water flows in, passing over the gills which trap and feed bacteria and algae. Oysters also feed on pollutants, such as nitrogen from fertilizer applied upstream. After removing the fertilizer from their mantle, they store it in their shell and flesh, then expel it.

Oliver walks down a dock that has concrete oyster tanks attached to its sides. He points out two tanks, one with six-month-old oysters, and one without.

” It takes just a day for these tanks turn crystal clear,” he said. The tank with oysters looks like spring water. It is strikingly cleaner than the tank without oysters.

The environmental potential has attracted new farmers–even as the number of all types of farmers declines nationwide–who see marketing potential in the bivalve. Sarah Matheson Harris, a former advertising associate turned oyster farmer, says that she believes they are the untold heroes of the environmental movement. She’s a former advertising associate turned oyster farmer who says she couldn’t imagine starting a business that lacked “an environmental backbone.”

With her husband and brother-in-law, she runs the Matheson Oyster Company, a five-year-old company in Guinea, Virginia, an hour south of Rappahannock. She sees evidence of oysters’ environmental potential at her farm, which is located in a marshy area surrounded by tall grasses and bald cypresses. Matheson said that the oysters are thriving ecosystems because smaller bait fish attract to the algae, and then larger fish will come. “They’re like the coral reef of this area.”

The plan to restore great oyster reefs

Globally, 85 percent of all oyster reefs have been lost, and some of the world’s last remaining wild oyster fisheries are along the East and Gulf Coasts.

When at their historic populations, the Chesapeake’s oysters could clean the entire bay–19 trillion gallons–in just a matter of days. To filter the same amount of water, today’s population would need to live for a year. However, this is slowly changing as environmentalists try to restore the oyster and the reefs that they once created.

Floating oyster larvae build towers of oyster clusters by layering old shell on top of old oysters in the wild. These habitats attract other shellfish such as barnacles, mussels, and sea anemones which provide nurseries for shrimp and fish. Restoring oyster reefs is a way to revive an entire ecosystem.

“This is an expensive endeavor,” says Allison Colden, a fisheries scientist with the Chesapeake Bay Foundation (CBF). “We are working to bring back a species challenged by lack of habitat, lack of adults for reproduction–it requires a lot of work.”

One challenge has been restoring a three-dimensional hard surface for baby oysters to settle on. Oysters that are dropped into the water do not have access to food-filled water currents. When rains push water into the bay, the sediment can easily smother the bivalves. Restoration groups are re-building reefs with old shells and other materials.

In New York, the Billion Oyster Project has replanted 100 living million oysters in New York Harbor since the project began in 2014. They have collected two million oyster shells from local restaurants to make substrate.

Environmental groups in Maryland and Virginia collectively plan to restore 10 times the oysters planned for New York, restoring 10 billion by 2025. They also use half-shells from restaurants, but they have also built artificial reefs out of concrete and granite.

Nestled into the marshy tendrils of Maryland’s Eastern Shore, Harris Creek‘s restoration–one of the largest ever undertaken in the Chesapeake–was completed in 2021. Two billion oysters have been planted on 350 acres of creek bottom. Colden says that the oyster density seen on these reefs is far higher than we expected. These projects can also remove a lot of nitrogen and phosphorous. We’re seeing tremendous returns so far in the ecosystem.”

Every year, the Harris Creek reefs remove nitrogen equal to 20,000 bags of fertilizer, estimates the CBF, a service worth about $1.7 million.

Oysters are such successful water cleaners that the state of Maryland is now helping oyster farmers cash in on their water purifying potential. To offset what they discharge into the bay, polluters can buy nutrient credits from oyster farmers, with larger farms offering more credits based on their larger potential to purify water.

” It was a way of starting cash flowing and getting the equipment out there while the new farming industry was taking place,” Jordan Shockley, from Blue Oyster Environmental, who brokers nutrient credit between farmers and businesses. Oysters can clean up more than just water pollution. Studies have shown that oyster reefs can help absorb excess carbon pollution and that aquaculture provides a low-carbon alternative to other sources of animal protein like chicken, pork, and beef. One study estimated that if 10 percent of U.S. beef consumption were replaced with oysters grown on farms, the reduction in greenhouse gasses would equal nearly 11 million cars taken off the road.

“Shellfish can have such a big impact on climate change if the right approach is taken,” says Shockley. “But on the flip side, climate change can really impact growth and revitalization in a negative way.”

How will a changing climate change the Chesapeake?

Crunching gravel underfoot, Mike Congrove, who runs Oyster Seed Holdings, LLC, walks to open-air tanks full of water teetering on a shore where the Rappahannock River opens into the bay. He dips his forearm in the tank’s brown water and pulls out a group of four-week-old oysters. The oysters are barely larger than a baby’s fingernail. He can fit dozens of them in his hand, with the teardrop outline of their shells already clearly visible.

The hatchery–an operation where oysters are carefully bred, fed, and grown–produces 100 million baby oysters every year. After six weeks, when the oysters have grown to a sixteenth inch, they are shipped off to farms along the East Coast. There, they are placed in wire mesh cages that are anchored just offshore. They will spend two years growing large enough to be market-ready, which is approximately three inches. The oysters will then be sold to restaurants all across the country.

At even younger stages, as larvae, baby oysters can be as tiny as 1/150 of an inch and nearly transparent. They are especially vulnerable to changes in pH and salinity without a hard shell. Congrove is the first step in many oyster supply chains. Without success at the hatchery oyster farmers don’t have any food to grow. Nature must cooperate in order to run a hatchery.

Congrove walks back to the warehouse and points out the “miles” of plumbing that pipe water to the many tanks and tubs inside. It’s balmy inside, which is what oysters love, and there’s a loud whirring of machinery in the background. It’s more like a science lab than a farm. One wing is dedicated to growing bright green algae under fluorescent lights, which is the oysters’ food.

The bay water flowing in is brackish, a mix of salty and fresh, which oysters need to fight off harmful bacteria and parasites. An oyster’s immune system and respiratory system can be affected if the right mix is used. This can make them more vulnerable to disease and death. On average, says Congrove, healthy salinity measures about 15 parts per thousands (ppt). When it drops below 10 ppt, and especially if it stays there, oysters can get sick, which is why in the 2018-19 winter, he worried when salinity clocked in at five to six ppt for months. Over half of the larvae failed to make it. “Sales were at 50 percent of normal… I’m not sure we’d be able to manage two [low salinity] years financially,” says Congrove.

One of the most destructive effects of climate change’s influence on rainfall is For every degree Fahrenheit the atmosphere warms, it can hold 7 percent more moisture, which can unleash the kinds of deluges experienced this year from Yellowstone National Park to Pakistan. The northeastern U.S. has seen a 70 percent increase in extreme rainfall since the 1950s. One study analyzing Virginia rainfall trends from 1947 to 2016 found some parts of the state saw rainfall rise by as much as an inch, and it was more likely to fall in quick bursts. Oyster growers and scientists are closely monitoring the water and trying to figure out when the acidity will rise.

Oceans absorb about a third of the world’s carbon emissions, setting off a chemical reaction that lowers pH levels and results in “ocean acidification.” More acidic conditions can be deadly for animals like oysters because it reduces the availability of the calcium molecules they use to build their shells. A warning sign that oysters may be endangered by ocean acidification was detected more than a decade ago in the Pacific Northwest. Between 2005 and 2009, billions of baby oysters were mysteriously dying. One hatchery in Oregon reported that oyster larvae were disappearing from their tanks.

Last year, VIMS began a $1.1 million research project to study how ocean acidification will impact oysters and other shellfish growing in the Chesapeake by the year 2050. Already, the bay has experienced acidification from polluted runoff. This leads to massive algal blooms and acidic waters. Scientists fear that this localized pollution will increase the acidification threat from climate change.

Research is still ongoing, but trends pointing to a more acidic future are already emerging in preliminary data.

“[Ocean acidification] has been significant in the past, but as temperatures increase, we’re expecting what we’ve seen already to be more dramatic,” says Marjy Friedrichs, a climate scientist at VIMS.

Scientists trying to restore the bay’s former glory need to make climate change a priority. This means that the small revival the oyster population has seen so far must be accelerated.

“Climate change impacts are going to make restoration harder. Colden says, “We need to do everything we can now to restore their habitat.” “There are some areas in the upper part of the bay where there were once really robust populations historically that now cannot support oysters.”

Oysters chart a course for the future

In a dimly lit corner at the back of Congrove’s hatchery, a cluster of tanks form the alcove he calls the research and development department. Working with VIMS and Virginia Tech, he’s testing out a system that would recirculate treated seawater throughout the hatchery, rather than relying on water straight from the bay that might hurt the oysters. Although the system is only three-years old, Virginia scientists hope that it will serve as a model for other oyster hatcheries in a similar uncertain climate. Farmers in Washington State and Maine have invested millions in similar technological solutions.

” I am always amazed by the industry’s resilience. There are some people that have to go, and that’s understandable. But there are so many that just keep going and make it work,” says Karen Hudson (VIMS science advisor who acts as a liaison between researchers and farmers). “The industry is not done growing yet.”

The parking lot of the Rappahannock Oyster Company is nearly full when Oliver docks his boat, securing rope around a barnacle-encrusted piling. He is proud of what he does (“just maintaining these things alive”) and that he can produce something people love that also benefits the environment where he grew up.

“People my age didn’t have a chance to eat oysters. Oliver says that there was a time when you didn’t have oysters. “Now it’s the younger generation’s chance to dive into that world.”