Toxic algae bloom forces closure of lakes, reservoirs

Carl Nolte/The Chronicle

A bloom of toxic bluegreen algae has invaded lakes in the East Bay Regional Parks District, forcing the closure of half of its six swimming lakes.

According to the district website, “danger” advisories went into effect after the most recent testing at Quarry Lake in Fremont, Del Valle in Livermore and Shadow Cliffs in Pleasanton.

All three lakes were immediately closed to swimming for people and pets, and signs were posted indicating that people should avoid contact with the water in these lakes and keep their pets out.

A danger posting means that the water has a higher potential to get humans sick.

Posted under the less severe “caution” advisory are Lake Temescal in the Oakland hills, Lake Anza at Tilden Park in the Berkeley hills, and Contra Loma Reservoir in Antioch.

A caution advisory suggests that it is safe to touch the water with immediate rinsing, though pets should still be kept out of the water.

“You want to be sure to avoid allowing dogs into the water,” said Jen Vanya, acting public information supervisor for the district.

“It could be heat, it could be water stagnation, it could be for all kinds of reasons,” Vanya said. “We don’t know what causes the toxins to rise to an unsafe level.”

Blue-green algae, also called cyanobacteria, are natural organisms that tend to bloom in areas with low water levels, due to drought and warm temperatures.

The first toxic algae blooms in the parks district happened during the drought year of 2014, when blooms were detected in Lake Temescal and Lake Chabot.

A comprehensive monitoring program was put into effect, and the reservoirs in the system are constantly tested to ensure that the water is safe for drinking.

According to the California Department of Public Health, exposure to toxic bloom can cause skin irritation and eye irritation, allergic reactions and, in the most severe cases, death.

Several dog deaths in California during the last few years have been attributed to toxic algae blooms.

Officials urge park visitors to follow recommendations on signs posted there. If you see a bloom, stay away from areas with foam, scum or algae mats, and keep pets away from the water.

People and animals should not consume water with cyanobacteria, even if it is boiled or filtered.

People or pets exposed to cyanobacteria should rinse with fresh water immediately, monitor for unusual symptoms and, if they occur, get medical treatment.

On Tuesday, the first day of spring, an ABC7 TV sky camera was able to capture what looked to be toxic algae blooms discoloring the water at both Lake Del Valle in Livermore and Shadow Cliffs Lake in Pleasanton.

Vanya advised people interested in visiting lakes in the district to check its water quality webpage to find out the status, which changes frequently.