Toxic blooms of blue-green algae are growing in many East Bay lakes because of unusually warm weather and California’s five-year drought.
Large amounts of blue-green algae, or cyanobacteria, have been recorded in multiple East Bay lakes, including Lake Anza in Tilden Regional Park and Lake Temescal in the Oakland Hills. This type of bacteria releases a toxin that can affect the nervous system if consumed, according to East Bay Regional Park District, or EBRPD, water management supervisor Hal MacLean.
EBRPD officials have begun treating affected lakes to reduce amounts of cyanobacteria, MacLean said. Although the algae is present in Lake Anza, toxins from the bacteria have not been detected, according to the EBRPD website.
According to MacLean, people who come into contact with the toxins in the water might get a rash, but the real danger comes from consuming the toxic algae.
“If you consume this toxin, that’s where they affect your nervous system, your liver, your kidneys,” MacLean said.
Mary Power, a professor in the campus department of integrative biology, agreed, saying that the cyanobacteria pose a greater risk to dogs than to humans. Carolyn Jones, a former EBPRD spokesperson, previously told The Daily Californian that a few dogs died after being exposed to toxic algae in Lake Chabot in Castro Valley.
“Dogs are attracted to the smell of these blooms,” Power said. “They like rolling in it and then licking their fur, then they ingest it and die with convulsions. That could also happen to people if they ingest it.”
According to MacLean, parks in the EBRPD always remain open, but bodies of water are sometimes closed for swimming because of algae growths.
“At one of the lakes, Lake Temescal, we’ve added a coagulant, something that binds up phosphorus, and we’ve been doing that to reduce the amount of phosphorus in the lake,” MacLean said. “This limits the amount of nutrients that the bacteria would have to grow.”
MacLean added that EBRPD has added an oxygenation system at Lake Anza. This system adds oxygen to sediments at the bottom of the lake, helping to keep nutrients in the sediments and deprive cyanobacteria of these nutrients.
According to Power, growth of blue-green algae in rivers and lakes increases when the weather becomes warmer and water becomes stagnant.
“(There are) two algae that are toxic in rivers — the species are Anabaena and Phormidium,” Power said. “Anabaena is present naturally, but when the flows keep moving, it’s a very delicate, almost wet, mucus-y Kleenex, that’ll be pulled apart and not get the chance to cover and blanket.”
MacLean said that earlier this year, Quarry Lakes in Fremont was closed for swimming. It is now open to water contact, but visitors are advised to take greater care, as the “water does not meet state standards,” according to the EBRPD website.
Power added that the levels of blue-green algae in East Bay lakes are “not surprising.”
“Since we’ve had the five-year drought in California, it’s been reported quite often,” Power said. “This year, it hasn’t been as bad as recent years. But I think with the trend, it’ll get worse.”