A toxic blue-green algae bloom is spreading in Spring Lake, where officials are warning dog owners to protect their pets by preventing them from swimming in the popular Santa Rosa lake.
The algae bloom was clearly evident Monday as a thick green scum on the top of stagnant water in a cove next to a popular trail that circles the lake, leaving a turquoise stain where it dried on the side of rocks.
"I hate to do it. I know how important this lake is to people, but their dogs are at risk," said Clayton Creager, a senior scientist with the North Coast Regional Water Quality Control Board, who recommended the lake be posted with warnings.
The levels of toxin could be potentially lethal to a dog that swam anywhere in the lake and then licked the water off its coat, Creager said.
The Sonoma County Parks Department on Monday afternoon was posting the lake as off-limits to dogs and to all wading, swimming and any water contact at the request of the water board.
"It is a health advisory to avoid contact with the water and we are doing it right now," said parks Operations Director Bert Whitaker.
The lake is already off-limits to swimmers, who could suffer rashes, eye irritation and even nausea, Creager said.
Boating is still allowed, and fishermen are warned to wash their fish thoroughly and not eat the innards.
The algae bloom does not affect the popular swim lagoon, which is chlorinated and has a liner that keeps its water separate from the lake.
Whitaker said this is the fourth year the algae has appeared.