Thousands of fish in San Francisco have been killed following a harmful algae bloom, experts have said.
Last week, large numbers of carcasses washed up on the shores of Lake Merritt with locals reporting the the surrounding waters had turned rust-coloured.
According to Eileen White, executive officer of San Francisco Bay Regional Water Quality Control Board, a harmful algae has been spreading in the region since late July.
"We normally have algae blooms during the summertime. But what’s unusual about this one is how large it is and the fact that there are fish kills," White said.
"This was a natural occurrence of Mother Nature and so, we don’t know when it’s going to end.”
Due to a heatwave which is expected to hit this weekend, it is thought algae numbers may grow even more.
On Wednesday, teams began to extract the dead fish from the lake after locals reported the odour of the dead carcasses.
"It doesn’t smell very good right now, so it’s a bit of a nuisance," said Graham Webster, who jogs around the lake once or twice a week.
"But the bigger question is what’s happening to the lake and the bay? And what’s causing it? Is it our fault? Can it be fixed?" he asked.
Algae blooms produce a toxin that is lethal to fish and other marine life, and as they spread, bacteria in the water start to consume the algae.
As it decays, it depletes the water of oxygen, leading the fish to suffocate, Jon Rosenfield, a scientist with the San Francisco Baykeeper conservation group.
