While what is being called a massive harmful algal bloom spreading across San Francisco Bay appears to have begun to subside as of last Saturday, state and regional water resource officials said the depleted oxygen levels caused ????by the algae could lead to large-scale aquatic die-offs in the coming days.
That's the warning, according to the California Water Resources Control Board, the San Francisco Regional Water Quality Control Board and the California Department of Fish and Wildlife.
Better known as "red tide" as the algae bloom has turned much of San Francisco Bay a reddish-brown color, the algae bloom was first detected in Alameda in late July and has grown to become the largest in the Bay's recorded history.
It has already been responsible for the deaths of thousands of fish, including large sturgeon, sharks, striped bass, bat rays and anchovies. While this type of algal bloom is not considered a threat to human health, it is recommended that people avoid swimming until further notice. The cause of the algal bloom remains unknown.
"It's very disturbing to see the extent of the damage to aquatic life and we know how disruptive this has been to the public," noted Eileen White, executive officer of the San Francisco Regional Water Board. "We are doing everything we can to monitor the situation, work with other agencies and look for solutions."
In Oakland's Lake Merritt, which is connected to San Francisco Bay, reports suggest that as many as 10,000 fish died in late August.
On August 29, San Francisco Bay Regional Water Board staff conducted a field investigation in the lake, where very low levels of dissolved oxygen were measured in the water. Water samples were collected for identification of algal species and toxins.
State Department of Fish and Wildlife officials will conduct shore-based and boat-based surveys this week at several locations around San Pablo and Suisun bays.
The objectives of these studies will be to determine the geographic extent of fish kills, any expansion into new areas, the species affected, and the number of fish killed in selected species such as white and green sturgeon.
Officials will also follow up on reports from community partners and scientists to determine where fish kills are occurring.
Due to the likelihood of increased fish mortality over the Labor Day weekend, fish and wildlife officials encourage people who may be recreating on nearby shorelines in affected areas to report sightings of dead fish through the iNaturalist smartphone app.
The water boards have worked with several agencies, including the city of Oakland, Alameda and San Mateo counties and the East Bay Regional Park District to post cautionary warning signs near affected waters, including Lake Merritt, the Oakland Estuary, Coyote Point and Crown Beach, to inform the public on how to avoid contact with discolored water caused by the red tide.
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