Ask Lookout: What’s the status of red tide at Santa Cruz County beaches?

Last week, several beaches in Santa Cruz County started to look a bit … off, as the shoreline washed up in shades of yellow, brown and rust red at some locations. 

Santa Cruz County officials are monitoring the red tide, or a phytoplankton bloom, that can cause a range of side effects, like skin irritation or coughing; depending on the severity, however, they haven’t yet issued a health advisory. 

Santa Cruz County Water Quality Specialist Eric Baugher told Lookout on Monday that, according to water samples, toxins in the water are still below harmful levels, but officials are continuing to test. 

“How long this persists depends on water conditions – warmth, nutrient status and life cycle of algal bloom. It’s too early in the cycle to predict when it will be over,” he wrote via email, adding that while the levels have been low, there also haven’t been any known reports of adverse health effects.  

Baugher said that red tide blooms occur when warming water mixes with nutrient-rich water. The phytoplankton, or algae, has “sunscreen” that protects it from the sun and is what creates the red color, according to UC San Diego’s Scripps Institution of Oceanography.

“The currents can also cause the bloom to gather in one location as we are observing right now,” Baugher wrote. “It dissipates as you travel north toward New Brighton [State Beach].” 

He said the red tide was first noticed last Wednesday and so far, county officials are reporting red tide activity at Rio Del Mar and Seacliff beaches. During testing, he said water samples were “rust red” at both locations. 

“I looked under the microscope to see if I could find the associated microorganisms,” Baugher said. He also ran tests for domoic acid and found a low concentration but didn’t see microorganisms. Domoic acid is a toxin produced by algae. 

Last Thursday, he ran additional tests and found Karenia brevis and Alexandrium, which are both red tide dinoflagellates (marine plankton) that produce brevetoxin and saxitoxin. Brevetoxin and saxitoxin are neurotoxins which are often found in contaminated shellfish and can cause symptoms such as stomach issues or headaches. 

Baugher said a health caution is issued when the level of saxitoxin is 0.8 parts per billion (ppb), but when he ran the sample, he found saxitoxin at 0.5 ppb. He added that 1.6 ppb is the level at which officials issue a health advisory alert and 3.0 ppb is the level for an adverse health warning alert.  

“We will continue to monitor concentration and spread of bloom to other beaches,” he wrote. 

On Thursday, the California Department of Public Health issued a warning to consumers to not eat recreationally harvested mussels, clams or scallops found in Santa Cruz and Monterey counties. The annual quarantine is in place through Oct. 31. 

Baugher said saxitoxin is the same toxin responsible for the mussels quarantine.  

“The seasonal ban on shellfish/mussel harvesting is in effect and recent tests showed that mussels are carrying a high concentration of saxitoxin and are dangerous to consume at this point,” he said. 

In a news release from the public health department, officials warned that consuming the toxins can cause serious illness or death and cooking doesn’t destroy the toxin. Officials say commercially sold clams, mussels, scallops or oysters from approved sources aren’t included in the warning. 

While county officials haven’t issued a health advisory due to the red tide toxins, they are reporting that cyanobacterial toxins are present in several lakes and lagoons including Corcoran Lagoon, Moran Lagoon, Kelly Lake and Pinto Lake. 

“Please avoid swimming, wading and other watersports in waterways that are experiencing  cyanobacterial bloom,” officials wrote, adding that the toxins can cause rashes, stomach upsets and eye irritation. “Pets are VERY vulnerable to toxicity and should be restrained from entering the water or drinking from the shore if a bloom is present.” 

To stay up to date on water quality and health advisories, visit the Santa Cruz County Environmental Health and Safety website. 

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