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Harmful algae bloom spreading across San Francisco Bay, turning water brown

<i>KGO</i><br/>Experts say the reason is a potentially harmful algae bloom that's spreading in waters throughout the Bay Area.
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Experts say the reason is a potentially harmful algae bloom that's spreading in waters throughout the Bay Area.

By Liz Kreutz

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    SAN FRANCISCO (KGO) — Looking out across the San Francisco Bay, you might notice it’s looking a little murky.

Experts say the reason is a potentially harmful algae bloom that’s spreading in waters throughout the Bay Area. It’s called Heterosigma akashiwo and it’s what’s currently causing the water in the bay to look so dirty and brown.

“About three weeks ago, the last week of July, we started getting reports of a very unusual brown discoloration of the water,” Ian Wren, a scientist with San Francisco Baykeeper, told ABC7 News. “Soon thereafter we learned the Department of Public Health had taken samples around Jack London Square and they identified the species that’s causing this bloom.”

Scientists at San Francisco Baykeeper, including Wren and field investigator Aundi Mevoli, are studying the algae closely. They’ve been taking water samples from different parts of the bay and sending them to a lab in Richmond to be analyzed. He said they have seen the algae around San Francisco, Oakland, Emeryville, Berkeley and Richmond. It’s also been reported in other areas, including Lake Merritt.

“We’re not quite sure what’s causing it,” Wren said. “There are some physical factors that might have sparked this bloom. such as that it’s been relatively clear out, the winds have died down a little bit, we have warmer waters, however, it’s really hard to associate what causes this kind of bloom.”

According to San Francisco Baykeeper, the last time an algae bloom of this kind occurred in the San Francisco Bay was 2004. It’s unclear it’s growing again now, but Wren said the nutrients polluting the bay are a major factor.

“There’s about 40 wastewater treatment plants that discharge a lot of phosphorus and nitrogen into the water,” Wren said. “And that’s the building block for algae such as this.”

“Normally conditions are such that the bay is rather turbid, it’s hard for sunlight to penetrate it, the bay is very choppy and it prevents the growth of large blooms like this,” he added. “Right now we’re in this situation where they really took off and we don’t really know when it’s going to stop.”

Wren said the algae can kill shellfish and other marine life. It’s not believed to be harmful to humans or pets.

“However, the cities of Alameda, Oakland, County of Alameda, East Bay Parks have issued cautionary warning postings that advise against recreating in the water,” Wren said.

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