By Krista Almanzan

The menace lurking in Pinto Lake isn't always obvious. (Krista Almanzan)
The menace lurking in Pinto Lake isn’t always obvious. (Krista Almanzan/KAZU)

In the Central Coast town of Watsonville, Pinto Lake City Park is a fixture in the life of many locals, including 20-year-old Juan Perez. He’s been fishing off the jetty at the southern end of the lake since he was 8 years old. “I come out here whenever I can,” Perez said. He usually fishes for sport–catch and release–except late this summer when he caught more than 100 pounds of carp, winning Watsonville’s “Carpageddon” competition. The monthly $50 prize to the angler who removes the most carp from the lake is about all Watsonville can afford, to address the lake’s big problem.

Nasty stuff

Pinto Lake is plagued with chronic blooms of a toxic blue-green algae called cyanobacteria. The algae feed on phosphorus from decades-old deposits of sediment in the lake. Farm fertilizers and leaky septic systems are also contributors, and the bottom-feeding carp stir that phosphorus up into the lake waters.

Blue green algae near the shore of Pinto Lake in Watsonville. (Krista Almanzan)
Blue green algae near the shore of Pinto Lake in Watsonville. (Krista Almanzan/KAZU)

“So if we can reduce the amount of carp in the lake we can reduce the amount of phosphorus in the water column,” said Robert Ketley, a senior utilities engineer with the city of Watsonville. The algae stay green while they’re floating on the surface of the water and then turn blue where they’ve dried on shore.  “The problem really manifests in the fall months, and that’s when you come down here and the lake will look luminescent green and will have an odor that you will either distinguish as ‘gym bag’ or ‘manure,’” Ketley said.

Visitors may not always notice the small patches of algae floating on the lake but it’s hard to miss the signs along the shore warning people to avoid direct contact with the water. When it gets really bad, the lake has to be roped off. Patricia McQuade, who manages Pinto Lake City Park, including its RV campground and boat rentals, says she’s had to make changes to keep people from getting sick. For example, she no longer rents boats to families with kids. “Can’t do that,” McQuade told me on a recent visit. “We can’t let them on the water because a kid has to put their hands over the side of the boat, right? Then they’re going to have to put their hands in their mouth.”

Spiking the meter

Signs warn of the blue green algae at Watsonville's Pinto Lake. (Krista Almanzan)
Signs warn of the blue green algae at Watsonville’s Pinto Lake. (Krista Almanzan/KAZU)

The algae produce a toxin called microcystin that when touched or ingested can cause effects ranging from nausea to liver damage. The California health limit for the toxin is 0.8 parts-per-billion. Between 2009 and 2012, Pinto Lake averaged 84 ppb: 100 times the health limit. And one sample back in 2007 showed nearly 2.9 million ppb of microcystin. That’s the highest level of that toxin ever recorded in California: more than 3 million times the health limit. A new study sponsored by the National Wildlife Federation ranks Pinto Lake’s algae among the worst in the nation. The blooms have been linked to the deaths of birds, fish and even sea otters in nearby Monterey Bay. That’s because the lake’s waters eventually flow into the Pajaro River, which empties into the bay. Once Ketley and a researcher showed symptoms of exposure themselves. Otherwise there are no documented cases of people getting sick from the slime.

Ketley says the algae will get worse when the rainy season kicks in. That’s when runoff from nearby agricultural fields and neighborhoods gives the biggest boost to phosphorus levels in the lake. The city plans to educate homeowners and businesses in the watershed about the effects of runoff, but that will only go so far. It’s also considering treating the lake with a chemical compound called alum. “You put alum into the lake,” Ketley said, “it binds up the phosphorus in the water column, and you create a barrier on the bottom of the lake, over the sediment, so that the phosphorus from the sediments can’t get up in the water column.”

Watsonville engineer Robert Ketley wants Pinto Lake to be a successful laboratory for countering algae. (Krista Almanzan)
Watsonville engineer Robert Ketley wants Pinto Lake to be a successful laboratory for countering algae. (Krista Almanzan/KAZU)

He says the alum treatment will cost several hundred thousand dollars. It’s money Watsonville does not have. The city hasn’t recovered from the economic downturn, when it had to cut staff and services. So Ketley applied for a grant from the State Water Resources Control Board. He says Pinto is the perfect-sized laboratory lake for other California communities. “One of the things I really feel strongly about,” Ketley said, “is I want to make  sure people see this as an opportunity to have a success story rather than doom and gloom–‘Oh no, toxic lake, bad situation.’ We can fix this.”

McQuade and other community members say it must be fixed. They recently formed a group called Friends of Pinto Lake. “When you think of how hard we work to save a redwood, maybe 300 years old,” McQuade offers for perspective, “this is 8,000 years old, so we have to do it.”

It could be months before Watsonville knows if it will get any state money to help clean up the algae and preserve this treasured lake.

Krista Almanzan reports for public radio station KAZU in the Monterey Bay Area. She has also produced stories for NPR and KQED.

  • Izabella Zamora

    This article is very informational, I wasn’t aware of what is happening to water and wildlife. My favorite part was when you explained the dangers of the human body when around toxic algae, you provided support evidence which included the treatment if effected. what you also did, was give places where the algae is mostly seen (shore, little patches of green in the water) have the people in Watsonville taken action yet? is there organizations that are trying to solve the problem? What i’m concerned about is the wildlife in the water, they too are being effected by the toxic algae. Are there any ways to help them if effected by the algae? what animals are around the area and could possibly already have been effected by it. what causes so much algae to appear in the lake, and where did it begin? this article lets people know the dangers in Watsonville lakes, and what to look out for when going for a swim maybe. most lakes have signs that prevent people from entering because they might have chemicals or something dangerous in the waters for example the toxic blue-green algae called cyanobacteria. is this bacteria preventable and what could be done to clean the lakes as of now? good job in providing important details and explaing the causes and effects of the cyanobacteria.


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