The world is your oyster, until it isn’t. 

​​On Sept. 1, the Centers for Disease Control and Prevention issued a health advisory about recent reports of severe Vibrio vulnificus infections, associated with warming coastal waters, especially in the Gulf of Mexico and along the East Coast. 

Vibrio vulnificus is a pathogenic bacteria found in warm seawater and may be on the rise in parts of the United States, causing a potentially life-threatening illness in humans known as vibriosis, with several reported deaths across the country.

Between the months of July and August of this year, at least six deaths from Vibrio infections were reported in three states along the East Coast. 

Infection can occur through various means, such as a cut or open wound. Interestingly, Vibrio can also lurk in floodwaters in coastal areas, due to hurricanes and other natural disasters. The most common, and most annoying, route to infection is through consuming raw and undercooked shellfish, especially oysters. 

For those of us in New England, aka the land of lobster rolls and clam chowder, abstaining from shellfish isn’t an option. We want our dollar oysters, and we want them now. Not to worry, there have been no reported cases in Massachusetts. 

The Massachusetts Division of Marine Fisheries has implemented safety measures against Vibrio parahaemolyticus since 2012, particularly monitoring oyster harvest conditions from May to October.

“[The regulations] have mainly to do with the cold chain—how quickly we chill the oysters and keep them covered and out of the sun and packed in ice.” said Bill Doyle, founder of Plymouth Rock Oysters and member of the Marine Fisheries Advisory Commission in Massachusetts.  

“We have to have that all done within an hour of harvest, and we have to record the harvest time and time of icing.”

Given the strict policies on the process of farming and harvesting oysters, oysters farms in Massachusetts first and foremost prioritize the safety of their products, and farmers must adhere to the city government’s policies in order to maintain their farming license.

“The city undergoes a monitoring program looking at water quality across the entire Massachusetts coastline, and classifies waters according to their degree of potential human pathogen,” said Dale Leavitt, PhD, professor of marine biology at Roger Williams University and partner at Blue Stream Shellfish, LLC. “The second line of defense occurs from May 19 to October 19, when our coastal waters are the warmest, and we are under very strict in terms of how we handle our oysters”

According to Dr. Andrew Rosenberg, a marine scientist, environmental and science policy expert, and chairman of the board for the Massachusetts Oyster Project, oyster farms are vigilant about the health of their oysters and conduct extensive testing.

“It does happen that people can catch and eat an oyster that is contaminated. But it’s not like that’s a regular occurrence.”

“However, you’re right to be concerned about climate change and diseases because warmer waters have been shown to increase the incidence of Vibrio viruses,” said Rosenberg. “And so that means that the surveillance systems checking any product that comes out has to be that much more intense that much more careful.”

As we selfishly fret about our ability to indulge in inexpensive oysters at a pub, a more ominous reality festers in the underbelly.

Oyster farming presents a sustainable alternative to wild oyster harvesting. When done properly, it reduces the pressure on wild oyster populations, protecting them from overfishing.

Improper oyster farming, however, can disrupt the seabed, reduce sunlight reaching the ocean floor, and interfere with sediment movement. Infected farmed oysters can spread disease to wild oyster populations, causing significant harm.

Oysters in the  U.S., have historically been caught wild in the Gulf of Mexico and farmed in the Northeast and Northwest. Chesapeake Bay has been an important center for oyster farming over roughly the last decade, in an effort to make up for a decline in the number of oysters being landed there that has gone on for over 50 years, caused in part by overfishing and other human activities. 

“There were massive harvests in most almost all areas of the coast over the last couple of 100 years, and in the latter half of 20th century, the populations were fairly depleted, with a few places where a wild oyster harvest still occurs into the 21st century Chesapeake Bay and down in the Gulf,” said Rosenberg.

“Now there’s a need to try and recover. There is a relationship to climate change because oysters filter water and reduce pollution. An oyster can filter 50 gallons of water a day,” said Rosenberg. 

Oysters are known for filtering seawater for nitrogen and sediment, which makes the water clearer and allows seagrasses to thrive by providing better access to sunlight. Oyster reefs protect beach habitats, provide housing for marine life, and in certain regions, oyster reefs act as natural shields against storms and tides, halting erosion and safeguarding the vital estuary waters.

As climate change progresses, ocean acidification becomes a growing concern, and human activity changes the way ocean water moves. Doyle explained that cargo tankers and cruise ships use ballast tanks to position themselves in water, taking in different seawaters from coasts around the world. Cross contamination of seawater leads to different species of marine life and bacteria ending up in different parts of the world.

“What we believe happened is that the strain of vibrio parahaemolyticus we have [on the East Coast] is a Pacific strain,” Doyle said. “We surmise that the ships going to different ports in the Pacific go all the way around the world and get into Boston Harbor.”

As water chemistry shifts due to human disruptions, oysters and other shelled species struggle to develop and maintain their shells. But climate change has a dual impact on oysters. While they are affected by it, they can also help mitigate its effects.

“Oysters have a calcium carbonate shell, and it’s harder to pull calcium out of water. So [acidification] does affect the growth rate,” said Rosenberg. “By the same token, [oysters] can sequester more carbon out of ocean water, which is one of the things that can happen by building a shell then you can also reduce potentially start to reduce acidification”

Oyster shells act as natural bicarbonates, reducing acidification as oceans heat up and become more acidic, preserving marine life. This vital role in reducing ocean acidification makes oyster farms an important part of conserving the environment.

The Massachusetts Oyster Project, along with local organizations and experts like Rosenberg, works on oyster restoration, maintains oyster upwellers across Massachusetts, and collaborates with local restaurants to gather and recycle oyster shells, effectively reducing ocean acidification.

Still, oyster farmers are concerned about the effects of severe weather on their businesses. 

“One of the things that we are noticing, at least in the last couple of years, is that there has been much lower occurrence of ice in the wintertime,” said Leavitt.

The taste of oysters is not just influenced by their origin but also by the time we consume them. Oysters in colder months are generally cleaner, more flavorful, and least likely to infect customers with a Vibrio infection. 

The oyster industry is one example of how climate change can affect industries and make a difference. Embracing sustainable practices and conservation efforts is crucial in addressing the challenges that climate change raises.

Oyster farms such as Cottage City Oysters, in Vineyard Haven on Martha’s Vineyard, are revolutionizing conservation efforts. By farming oysters, clams, and seaweed in an innovative way, they maximize surface area and productivity. Such farms act as carbon sinks, sequestering more carbon from ocean water, mitigating acidification, and making sure their products don’t give us life threatening infections. 

“Our farm is really unique in that we’re in the open ocean. We’re not in a salt pond like everybody else or an estuary,” said co-owner, Dan Martino. “The state uses our farm as a baseline testing against what normal bacteria levels should look like in the open ocean first, elevated one in ponds.”

This farm is sub-tidal, which means it’s always under water, allowing the ability to grow the seaweed above the oysters. Seaweed and kelp sequester and produce more carbon than rainforests. Moreover, each oyster shell has 12 grams of carbon in it and can clean 50 gallons of water each day. Farms like this are important in the future, because they act as a carbon sink. However, there is risk involved. 

“We’re not sheltered from [hurricanes]. And that’s why most people don’t try it,” says Martino. “I mean, your mortality rate goes way up when you start trying to farm in the open ocean. And infrastructure wise, like we have giant cages. It’s a lot more money upfront.”

The oyster industry illustrates the impact of climate change on various sectors and its potential for positive change. There’s more to oysters than just shucking and slurping those briny bivalves. As consumers, being mindful of the source of our oysters is essential, ensuring safety in a changing climate and promoting ethical consumption practices.