“It’s pretty rare to have these visible red tides along the coast. … I don’t think we’ve had something in this order for many, many years,” said Gregg Langlois, California Department of Public Health senior environmental scientist.
Red tides manifest when algae plankton converge with an aquatic environment conducive to their growth. In general, the tiny organisms flourish under sunny weather in warmer, stratified, nutrient-rich water. The colorful events can last weeks or dissipate in hours, as was the case in El Granada.
  
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Moss Beach biologist William Van Peeters has witnessed red tides many times before, but was “startled” when he came upon last month’s vivid spectacle at Surfer’s Beach.
“That one was as strong as I’ve seen it anywhere – the most concentrated red tide I’ve seen,” Van Peeters said.
Beachgoers have been reporting the “spectacular bioluminescence” of algae blooms in waters from Monterey to Tomales Bay, Langlois said. “It's definitely widespread.”
That could be indicative of an influx of toxins in coastal waters that sully shellfish and cause sickness in swimmers and surfers, scientists say.
Langlois oversees the state’s Biotoxin Monitoring Program, an initiative aimed at keeping track of toxic coastal events and shellfish populations. Due to the potential for toxic algae blooms to occur in summer months, the state issues an annual quarantine prohibiting people from plucking mussels between May and October.
Swimming in the tides is also a bad idea, experts say. Eruptions of red algae aren't necessarily toxic, but they do serve as a kind of warning. In the past month, as reports of red tides roll in, researchers have simultaneously recorded a spike in toxin levels off the coast.
“Although the blooms appear to (consist of) nontoxic species, the environmental conditions are ripe for toxic species to be around. … They all like the same basic physical conditions,” Langlois said. “It tells us we’re in a higher risk period.”
John Ryan, an oceanographer with Monterey Bay Aquarium Research Institute, studies red tides for a living. He says the tides “can cause harm in a great diversity of ways” apart from their toxic impact.
Dense concentrations of plankton attract organisms and animals on the higher rungs of the food chain. It’s not uncommon to see a flurry of fish, seals and birds feeding in the area of a bloom, regardless of whether there is a distinct red tide. The plankton suck up oxygen in the water, which can be deadly for marine animals in the area.
Hundreds of pelicans and small pods of seals congregated for what appeared to be a feeding frenzy at Surfer’s Beach in the days before the waters ran red. And dozens of dead jellyfish washed up on the beach in the wake of the red tide.
Further, Ryan said, the plankton’s movement can whip the water into thick foam that penetrates birds’ feathers. The foam compromises birds’ natural insulation and can cause them to die from hypothermia.
Ryan is evaluating satellite images of Surfer’s Beach captured during the red tide in August. He hopes they might shed some light on the events and help guide researchers through ecological tests off the coast this fall.
“What we want to understand, ultimately, is, what are the factors controlling the spread of harmful species?” Ryan said.
Langlois says there is no way to mitigate red tides. For now, researchers at the department are making sure warnings are posted up and down the coast. With El Niño brewing, Langlois suspects this year might illuminate details about the patterns and systems of red tides. “In terms of implications, there may be some sort of cycle to these things,” Langlois said. “If so, it probably occurs over a very long timeframe. It’s something we don’t have a handle on.”
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