Are local oysters safe to eat after Florence flooding? Here’s what we know

When the flooding following Hurricane Florence hit a peak, people were worried about what pollutants were being washed into the water.

Even now, a month after Hurricane Florence, several major oyster beds are closed, especially in areas near where flooded waters emptied out to the ocean.

The South Carolina Department of Health and Environment Control has a GIS map on its website that is updated with which areas are safe to take the mollusks from. DHEC looks at a variety of factors to determine the safety of a particular reef, including if pollution events happened recently. Beds can close after regular rain events too, depending on if regulators find a reason to shut down a bed.

According to these maps, almost all of the oyster beds in Horry County are still listed as storm closures. While some areas in Georgetown County are available to harvest in, a majority of the oyster beds also are listed as close.

Further south in Hilton Head, fewer beds are closed.

Why beds close

The eastern oysters in South Carolina are filter feeders, eating and cleaning the water as they go, according to the South Carolina Department of Natural Resources.

Being a filter feeder means the oyster eats by taking nutrients from the water and converting it into energy. Through this process, they also can remove pollutants from the water.

Following Florence, however, receding floodwaters took all sorts of chemicals and debris back into the water supply and out toward the ocean. Yet, the local oyster population is going to be fine, according to Coastal Carolina professor Juliana Harding, an expert on oysters.

Oyster beds provide an important habitat to many creatures that live “between tides,” exposed to both land and sea predators. Even though water from the rivers dropped salinity during the flooding event, the tides quickly brought salt water back into the habitat.

“The oysters may have been less inclined to feed because they felt the water smelt funny or wasn’t quiet right,” Harding said. “The oysters have to be smart about that.”

Beyond the salt in the water, chemicals, pollutants or changes in water quality from the flood had the potential to threaten individual oysters, but only if an individual oyster decided to filter.

“It would depend on a case-by-case,” she said.

To make sure people are not harmed by a contaminated oyster, DHEC can decide that the threat of oysters filtering a contaminant is a reason they might close a bed.

DHEC randomly picks oysters to make sure they meet health standards and to see if there is evidence that some might be contaminated. Each month, the regulators check more than 400 sites in this process.

Even if the oyster filtered a pollutant and is deemed in an unsafe area, depending on what it was, the concentration of the pollutant will go down inside the oyster itself. Eventually it could be deemed safe for harvesting by regulators.

If the oyster is unable to get the chemicals out, then a human could potentially consume both the oyster and the contaminants.

“Not many of those are good things,” she said.

The circle of life

Even though flood events left oyster beds unharvested and potentially killed off some oysters, this isn’t the end of the eastern oyster by any means.

Harding said that the empty shells left by oysters that died will be refilled by the free swimming oyster larvae now maturing and looking for a new home. This process takes place during the fall and lasts until early November.

“There are plenty of little oysters out in the water,” she said. “It’s not the end of the world from the standpoint of the oyster.”

The crisp, fall weather in Horry County is a good thing for the oysters. It creates better water conditions for the oyster population to recover and for the baby oysters to find a new home.

“There’s plenty of food for them,” Harding said.

This story was originally published October 25, 2018 at 10:51 AM.