Although the Alaska Department of Environmental Conservation last week shut down a Halibut Cove oyster farm because of increased paralytic shellfish poison (PSP) levels, oysters sold by the Kachemak Bay Shellfish Growers Cooperative remain safe to eat, Marie Bader, the president of the Kachemak Shellfish Mariculture Association said on Monday.

“We want the general public to have full faith in the co-op, and we will only sell product that is 100-percent safe for them to eat,” Bader said.

DEC tests through lot sampling oysters harvested from Kachemak Bay oyster farms. Bader said the Kachemak Bay Shellfish Growers Co-op submits weekly to DEC samples from each farm harvested. George Scanlan, DEC shellfish permit coordinator, said oysters will only be sold from lots that have been tested.

“If it’s a commercial harvest, it’s been tested,” he said last Friday. “If you’re going to a restaurant and oysters are served and it’s a commercial product, I’m good it’s been tested.”

Only one oyster farm in Halibut Cove tested above the PSP regulatory limit of 80 micrograms per milliliter or 80 parts per million, DEC said in the press release. The elevated levels were found in blue mussel and oyster samples collected on Sept. 13 from that oyster farm.

In a follow-up email to oyster farmers on Monday, Scanlan clarified that the closure only is for Halibut Cove oyster farms and does not affect farms elsewhere in Kachemak Bay. Those farms remain open to harvest on a lot-sampling plan, where product is held out of water and refrigerated until PSP-toxin test results are received. Scanlan said lots that test below 80 parts per million would be considered safe and may released for sale. The Halibut Cove area will remain closed to harvesting until three consecutive weekly samples test below the 80 ppm threshold.

Bader said that while DEC stops release of oysters that test higher than 80 parts per million, the co-op cuts off sales at 60 ppm. Until the Sept. 13 test, no shellfish had tested above 40 ppm this summer. That test wasn’t from a co-op farm, Bader said.

PSP toxins are caused by an increase in algae of the species Alexandrium. Shellfish store the toxin from the algae in its tissue.

In the press release, DEC also cautioned recreational and subsistence shellfish harvesters that no beaches are certified or designated as safe from PSP by DEC. All recreational or subsistence harvested shellfish, including clams, mussels, oysters, geoducks and scallops, may contain paralytic shellfish toxin that, if ingested, can cause death, DEC said in the press release. The toxins cannot be eliminated by cooking, cleaning or freezing.

The increase in PSP toxins could be related to above-average ocean temperatures in Kachemak Bay and the Pacific Northwest, part of a trend that also has seen a rise in domoic acid, another toxin produced by ocean algae, Pseudonitszchia. Kachemak Bay did see blooms of Pseudonitszchia, but not an increase in domoic acid.

Scanlan said the increase in PSP toxins is probably related to higher ocean temperatures.

“The general thinking is the evidence seems to point that way,” he said. “The warmer weather tends to provide the ideal conditions for the bloom of these organisms forming these toxins.”

The past two summers have seen above-average water temperatures in Kachemak Bay. Kachemak Bay Research Reserve analyst Steve Baird said in August that the 15-year average ocean temperature for July was 8.5 degrees Celsius or 47.4 degrees Fahrenheit. In July 2014, the average temperature was 9.27 C or 48.7 F and for July 2015 even higher, 10.33 C or 50.6 F.

In a KBRR report issued on Sept. 18 for the period of Sept. 1-15, Pseudonitszchia was present in plankton tows done in Halibut Cove, the Homer harbor, at the Homer ferry dock and in Seldovia harbor. Alexandrium was seen at the Homer harbor. Water temperatures ranged from 10 to 11.2 C, with an average of 11 C.

Bader said oyster farmers keep careful track of water temperatures and provide measurements to KBRR for its data collection. She said there is usually an increased danger of issues like PSP during neap tides and warmer ocean temperatures in late August. Neap tides tend not to flush bays and fjords as thoroughly.

“That would be a time when we are being extra vigilant,” Bader said. “We have been extra vigilant because it’s a warmer summer.”

Usually at this time of year water temperatures begin to drop, and thus the danger from harmful algal blooms also drops.

“With these dropping temperatures I’m just shocked it happened anyway,” Bader said.

From Oct. 1-April 1 when colder temperatures reduce the danger of PSP and other toxins, Kachemak Bay Shellfish Growers Co-op farms usually test once a month. As a precaution, Bader said co-op members will test weekly.

Recreational and subsistence shellfish harvesters should be aware of the signs of PSP, DEC said in its release. Initial symptoms include a tingling or numbness in the lips and tongue, often followed by tingling and numbness in the fingertips and toes. These symptoms may progress to loss of muscle coordination, dizziness, weakness, drowsiness and incoherence. The only treatment for severe cases is a mechanical respirator and supplemental oxygen. If symptoms are seen, call 911 or get to a medical facility immediately, DEC said.

Michael Armstrong can be reached at michael.armstrong@homernews.com.