Health officials urge caution after harmful algal blooms found in Bay Area waters

With temperatures sweltering, the water in many Bay Area lakes, bays and reservoirs might look inviting, but health officials are urging people to use caution while swimming, boating or fishing as the conditions are ripe for the creation of toxic blue-green algal blooms.

Harmful blue-green algal blooms have not only been increasing in frequency in recent years, but also in duration, here and elsewhere, said Marisa Van Dyke, a senior environmental scientist and harmful algal bloom manager with the state Water Resources Control Board.

“Before it was a few weeks to months” when the blooms would appear, she said. But now, “we’re also seeing blooms that occur in the winter months or year-round. We’re concerned, and that’s why we’re working toward getting the resources to monitor and get better data to inform what to do about it.”

Most harmful algal blooms are formed by cyanobacteria, which are small microbes that live nearly everywhere. Rising water temperatures, slow-moving water and excessive nutrients encourage cyanobacteria to grow and form these toxic blooms, scientists say.

In separate incidents last week in Discovery Bay, a person and a dog both developed minor symptoms after being exposed to the harmful blue-green algae. The blue-green algae can produce toxins that can kill or sicken animals and people, causing eye irritation, rashes, vomiting, diarrhea, or cold or flu-like symptoms, Contra Costa Health Services officials warn.

“People can get really sick, and if they have a lower immunity, it can be really serious,” Contra Costa Supervisor Diane Burgis, whose district includes Discovery Bay, said. “It’s fun to have your dogs be able to go jump in the water and go get the ball and all that, but it’s not worth it at this point, when you just never know if that’s going to be what makes your dog sick.”

The state Water Resources Control Board, which has been sampling the water in Discovery Bay, confirmed the presence of elevated levels of the blue-green algae bay-wide. Health officials this week placed the town’s waterways in the “caution” zone – the lowest advisory level – urging people to stay away from the blue-green scum and keep their pets out of the water, and not eat shellfish, or any part other than the filet of fish caught there.

“It’s more of an awareness thing,” Burgis said of the cyanobacteria blooms, which she called a growing issue. “For folks in Discovery Bay, it used to be that you could just jump into the water right off your deck or your pier, but now that’s not recommended because you just never know.”

Burgis called it the “new normal.”

“Similar to us having fire seasons that are starting sooner and more intense, we’ve been seeing blue-green algae in all kinds of water bodies over the last several years,” she said.

People will recognize the cyanobacteria by its bright and dark green colors, Van Dyke said.

“Normally the water is dark and does not have this bright or mid-level green discoloration to it,” she said of Discovery Bay’s waterways, noting one might also see a film of the scum that can form in the more stagnant areas.

Concerns about cyanobacteria first surfaced in 2015 in Discovery Bay when Contra Costa County environmental health officials, responding to complaints, tested the waters and found some harmful blooms. In 2016, the county began routine sampling of various parts of Discovery Bay where one child became sick after swimming near blue-green algae.

Discovery Bay isn’t the only place where cyanobacteria have been spotted as rising temperatures, the drought, and excess nutrient-rich agricultural runoff and lawn fertilizers have created the perfect recipe for growing the harmful blooms throughout the region in the past several years.

East Bay Regional Parks District, which collects its own water samples for testing, found cyanobacteria in high enough levels to warrant “danger” signs and the closing of the popular swimming lake at Del Valle Regional Park in Livermore just before Memorial Day weekend. When in the “danger” level, no person or animal should enter the water, nor drink or cook with it or eat fish from the waterway, according to state guidelines.

East Bay Regional Parks District tests regularly for water quality and posts information about closures and cyanobacteria on its website, spokesman Dave Mason said.

“If it’s deemed safe, it  (Del Valle) will open,” he said. “We obviously would love to have that facility open to the public. And we’re testing regularly to see if the situation changes.”

Mason said blue-green algae is challenging public agencies throughout the country as drought and climate change affect waterways. The district saw its first trouble with Lake Temescal in 2014, he said, but the park – closed for two years for reasons unrelated to algae – has now reopened, though the lake is in the caution zone, meaning people should avoid any algal blooms and pets should stay on shore.

The lake was treated this year and last year with a phosphorus-binding chemical that limits the nutrients cyanobacteria blooms need to grow, said Hal MacLean, an East Bay Parks water management supervisor.

“Sometimes it works better than other times,” he said of the chemical treatment. “Each water body is a little bit different. There’s different amounts of phosphorus in different areas of the lake, and it depends on where the cyanobacteria is growing.”

Also in the “caution” zone as of Thursday are some parts of Fremont’s Quarry Lakes, including Shinn Pond, Horseshoe Lake and Niles Swim Beach, and Keller Beach at Miller/Knox Regional Shoreline in Richmond.

The East Bay lakes are just some of dozens of lakes, rivers and other waterways in the state that have been labeled with “caution” or “danger” signs this year. The state began collecting voluntary reports of harmful algal blooms in 2016 and each year the numbers have risen, but some increases might be attributed to greater awareness, Van Dyke suggested.

The environmental scientist cautioned, however, that there’s a great variety of cyanobacteria and one can’t tell if they are producing toxins just by looking at them. Nor can one test all that is there, she said.

“Looking at a bloom, we can’t tell if there’s toxins or not; it’s something you have to measure,” the environmental scientist said, urging caution in dealing with the blooms, abiding by the posted advisory signs and staying away from potentially harmful blooms while in the water.

“We really want to get folks educated about those healthy water habits so that they can protect themselves and their pets,” Van Dyke said.

More information about harmful algae blooms can be found at cchealth.org/eh/hab

To report a suspicious bloom, go to https://mywaterquality.ca.gov/habs/index.html

To see which East Bay Regional parks have cyanobacteria and what is open, go to www.ebparks.org/natural-resources/water-quality

For a fact sheet related to pets and blue-green algae exposure, go to www.mywaterquality.ca.gov/habs/what/vet_habs_factsheet.pdf

For a map of reported harmful algal blooms, go to https://mywaterquality.ca.gov/habs/where/freshwater_events.html

For more on blue-green algae from the Calfornia Department of Water Resources, go to https://bit.ly/3QD9uzO.