Warning: Oysters May Be Deadly

Photo: James Noble / Istock

related articles

Oysters are a true superfood, offering healthy portions of both iron and Vitamin B12, but oysters harvested from the Gulf Coast in summer can also be deadly. About 15 people die every year from eating oysters contaminated with the Vibrio vulnificus bacteria, according to the Center for Science in the Public Interest.

But they don't have to. To protect those vulnerable to death by infection -- people with liver or kidney disease, AIDS, cancer, diabetes or other conditions that can compromise the immune system -- techniques that costs pennies per oyster can kill the bacteria without affecting taste, according to the center. California banned the sale of Gulf Coast oysters that had not been treated, saving about six lives every year. Legal Sea Foods and Costco are among the retailers that refuse to sell untreated oysters. But the Food and Drug Administration doesn't require treatment, and neither do most states.

"Letting untreated Gulf Coast oysters reach consumers this summer will needlessly sentence several of them to death," said Sarah Klein, an attorney for Center for Science in the Public Interest. "Unfortunately the Food and Drug Administration has abdicated its responsibility to ensure shellfish safety and instead lets the industry police itself with minimal oversight. That’s proven to be a deadly mistake."

While human health is one concern for the oyster industry -- the health of the oysters themselves ought to be, too. Overharvesting, contamination, ocean acidification and a host of other environmental threats make their place on our plates perilous.

According to a recent study by the Nature Conservancy, 85% of oyster reefs have been lost worldwide. That's right: Only 15% of the world's oyster reefs remain. In most individual bays around the world, the rate of decline is even worse, exceeding 90%, and in many cases -- particularly in North America, Europe and Australia -- oysters are "functionally extinct."

Besides the obvious -- they're good to eat -- oyster reefs are important to shoreline ecology, filtering water, providing habitat for other fish and marine life, and buffering beaches from erosion.

A separate report, published today in PLos ONE by Smithsonian scientists, cites overfishing and disease as the prime causes of decline in shellfish -- but raises an alarm about a new and growing threat: ocean acidification.

Ocean acidification is caused by the absorption by the oceans of carbon dioxide pollution, which causes the pH to drop. The resulting carbonic acid inhibits the formation of carbonate shells and at highly acidic levels can even dissolve existing shells. Scientists have been trying to generate public awareness about this growing threat -- distinct from but related to global warming, because both issues share the common cause of burning fossil fuels. (A comprehensive report made this dire prediction: Oceans are returning to a primordial stew.)

Larval oysters -- particularly the Eastern oysters native to the east coast of North America -- are particularly susceptible to acidification, according to the report. Scientists grew oysters in water of varying acidity reflecting pre-industrial conditions as well as conditions expected in the next 100 years.

Under future acidic conditions, Eastern oysters experienced a 16% decrease in shell area and a 42% reduction in calcium content. Suminoe oysters, found in Asia, were more resilient.

COMMENTS ()