SANTA CRUZ -- State officials are warning people to steer clear of eating recreationally harvested shellfish from the Monterey Bay because of a unseasonably high amount of toxins that could be fatal if ingested.
The warning from the California Department of Public Health applies to bivalve shellfish, such as mussels, clams and whole scallops, from Monterey Bay and inner Tomales Bay in Marin County.
The shellfish have a high amount of paralytic shellfish poisoning toxins, and if consumed, can cause severe sickness or death, according to the agency.
"In a nutshell, we do get increases in those toxins called PSP," said UC Santa Cruz ocean sciences professor Raphael Kudela, who works with a team of researchers to collect mussels from the Santa Cruz Wharf each week to send to the state for testing.
While there is normally a statewide quarantine on mussels from May to October when high toxin levels are expected, it is rare for the region this time of the year.
"But it's very unusual to get the high levels that we're getting at the Santa Cruz Wharf and in the Monterey Bay," Kudela said.
An additional quarantine on mussels for northern Humboldt County -- from the border of Del Norte and Humboldt counties to the northern jetty at the entrance of Humboldt County line -- was extended indefinitely Oct. 31.
Usually, rates of PSP toxin levels this time of the year do not exceed 100 micrograms per 100 grams in shellfish.
State health officials send out alerts when amounts exceed 80 micrograms. Current rates are being measured from 500 to 600 micrograms, Kudela said.
It's been years since the toxin levels have measured this level at this time of the year, Kudela said.
Though high amounts were detected Nov. 27 and again Dec. 4, officials waited to be sure the toxin amounts weren't a passing anomaly in the environment, said Greg Langlois, a senior environmental scientist for the state Department of Health.
"Just as we follow the trend downward to figure out when it's safe to open, we try to get enough data in a short amount of time to see when we're seeing an increasing trend," Langlois said.
In the week before the spike, the toxin was undetectable in shellfish samples.
"It could be just because of the natural rhythm in the ocean, but it's also quite possible that this same organism is expanding and the toxin is becoming more toxic because the oceans are warming up," Kudela said.
The toxin is produced by alexandrium dinoflagellates, a naturally occurring plant in the ocean that's known to cause red tide. While shellfish that eat dinoflagellates are not affected by the toxin, mammals are vulnerable.
"The shellfish are acting as a concentrator so they can concentrate the toxin 50 times greater than they could occur in the environment," Langlois said.
It's not likely people swimming or surfing will be affected by the toxin, Langlois said.
"You couldn't possibly ingest enough (dinoflagellate) cells to cause any problems," he said. "You'd drown or die of salt poisoning before that."
Symptoms for this severe type of shellfish poisoning symptoms usually appear 30 to 60 minutes after ingestion, according to the Centers for Disease Control and Prevention.
The toxin produces a tingling around the mouth and fingertips. Severe cases can result in complete muscular paralysis and potentially death from asphyxiation.
"There's no antidote to the toxin," Langlois said. "Anybody who suspects they are experiencing minor symptoms should get medical attention as soon as possible."
Shellfish lovers can get their fix from state-certified commercial shellfish harvesters who are subject to mandatory testing.
State officials urge anyone interested in information about the toxin to call the state shellfish information hot line at 800-553-4133.
Follow Sentinel reporter Calvin Men at Twitter.com/calvinmenatwork