18 Nov
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Farming Filtration in RI Waters

Dr. Robert Rheault, Executive Director of the East Coast Shellfish Growers Association.

Dr. Robert Rheault, Executive Director of the East Coast Shellfish Growers Association.


Do oysters cause disease? Or, can oysters be the magic bullet that cleans up polluted waters? Which is better for fish habitat: an oyster bed, or one of eel grass? Dr. Robert Rheault, Executive Director of the East Coast Shellfish Growers Association (ecsga.org), discussed those questions in conjunction with the showing of the film “Shell Shocked: saving oysters to save ourselves” at URI recently. The event was sponsored by the Rhode Island Natural History Survey (RINHS) as part of Rhode Island Natural History Week, a statewide celebration of the outdoors.

Historically, the association between oysters and disease came in part from ignorance about the environment from which oysters were harvested. The film notes that in the mid-19th century, oyster harvesting was a thriving industry in Manhattan. In fact, two of the city’s most famous landmarks, Liberty Island and Ellis Island, were once called Great Oyster and Little Oyster. Harvesting oysters was big business, and supported large numbers of former slaves who came from the South to establish a new life. The film showed pictures of oyster carts lined up the same way hot dog vendors appear in cities today. Yet it was the expansion of the city that would contribute to the industry’s downfall.

In the mid-19th century, people began to get sick after eating oysters. Several people died, and the city was gripped in what became known as the “Oyster Panic”. Suddenly, one of the most popular foods in the city was not being eaten anywhere. Did the consumption of New York’s favorite food cause disease? A story that ran in the New York Timeson October 28, 1854 bemoaned the delicacy’s absence:

“How doleful the saloons seemed yesterday! At all great dinners the absence of one accustomed dish acted like a skeleton at the feast – nipping budding jokes, tempering cross humors, solemnizing men who hate to be serious.

“Now, the ground of all this panic is a rumor that there is a sickness caused by eating oysters prevalent, and that it has caused five deaths… We are unable to get facts enough out from behind the rumors to justify any panic at all.”

NY Times Oyster Panic Story full text.
But eventually, there would be enough facts to justify a panic. While the oysters as a species did not cause disease, what the mollusks ate certainly did. As New York continued to grow, the methods of dealing with its sewage did not. Effluent from the city was being dumped untreated directly into the Hudson River, home to so many oyster businesses. Oysters are filter feeders, which means they obtain their food by drawing in the surrounding waters, consuming the microorganisms found there, and then expelling the filtered water. And in 1854, the water those oysters were consuming was well and truly contaminated. Shellfish are capable of taking in a certain amount of pollution; once the pollution clears from the water, the oyster passes the toxins through its system and becomes edible again. But a relentless diet of sewage never gave the oysters the opportunity to regain their healthy systems. The oyster industry collapsed.

Fast forward to today. According to the film, wild oyster reefs have been declared the most impacted environment on earth, with 85% of them gone. Why should that matter? It turns out that oysters are not only tasty treats enjoyed by seafood connoisseurs; they contribute to keeping both fresh and salt water clean. One oyster will filter 50 gallons of water each day, helping to clean the environment. And their reefs are vital homes to a wide variety of aquatic life. When those reefs are destroyed, the life that existed within them disappear. Dr. Rheault made the case for reestablishing some of those reefs around Rhode Island.

“So eventually people finally discovered that eating the food that was grown in the midst of sewage wasn’t a good idea,” Rheault said. “But as people began to learn more about how oysters work, some people thought it would be like a magic bullet. If you have pollution, why not just put an oyster bed in and clean up the mess?” The trouble is, according to Rheault, it’s not that simple. The source of the pollution needs to be controlled first. Oysters will not simply grow in an area where they don’t exist (or have been killed off), particularly when there’s heavy pollution. The film, and the discussion that followed, addressed some of the work being done to achieve a balance.

Research is being done in New York, New Jersey, and Rhode Island to determine the ability of oysters to establish themselves in new locations, as well as ways in which they can contribute to cleaning a polluted area. Sewage, for example, leads to a process called eutrophication. According to the US Geologic Survey (usgs.gov), phosphates and nitrates become concentrated in sewage, which in turn creates an abundance of algae. Once the algae dies off, the oxygen in the water is consumed, and the water can kill off other organisms, such as fish, that had been living there. The right blend of sewage reduction and introduction of oysters can potentially restore these dead zones, according to Rheault. It isn’t a miracle cure, and the research is ongoing, but Rheault says the early results are positive, and points to a recent survey done by a grad student.

“This student surveyed some of the oyster beds we had established, in order to determine fish population. The comparison between those beds and eel grass beds (an area highly conducive to supporting organisms) showed that there was anywhere from a hundred to a thousand times more fish around the oyster beds than there were around the eel grass.” Rheault says this is at least partial justification for the need to continue the research. “If I’m going to take my kids fishing, I’m going to take them to the oyster beds!”

Shell Shocked Poster


  • So cool. Yet, it is sad that so many don’t recognize the human impact on the natural world. If we respected it more, nature could work for us and with us if we were more cognizant of the functions and factors that impact our environment and the natural world.

    • Well said, Meg. Shepherding the natural world requires endless work, particularly when the biggest threats come from ourselves. Still, the daily reward of nature – a beautiful sunset, a clean breeze, a feeding bird – fuels our efforts to carry on.

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