California sea lions, Zalophus californianus at Moss Landing in 2008.
Source – Brocken Inaglory, CC SA 2.0.
The recent growth of harmful algae along the southern California coast is producing high concentrations of a toxin that affects California sea lions.
The problem started around mid-August, according to The Guardian, when adult sea lions, mostly females, began turning up along the southern California coast with signs of poisoning: disoriented and agitated, with their heads bobbing and their mouths foaming.
Marine animal organizations say they were inundated with inquiries from alarmed beachgoers. “We are responding to 50-100 calls a day,” the Channel Islands Marine and Wildlife Institute, which works in the island region off the coast of Los Angeles, wrote on Instagram.
It was quickly determined that the culprit was domoic acid poisoning – a naturally occurring neurotoxin that’s produced by tiny single-celled marine algae. The neurotoxin accumulates in crustaceans, small fish, and squid, and then gets transferred to larger predators, such as sea lions.
According to the California Harmful Algae Risk Mapping (C-HARM) system, growth of the toxic algae Pseudo-nitzschia is expected to continue in the coming days, reports NOAA Fisheries.
Ocean conditions tend to favor the outbreaks, and seafood is regularly tested for domoic acid, which in humans can cause Amnesic Shellfish Poisoning.
Clarissa Anderson, a scientist who directs the Southern California Coastal Ocean Observing System, was among those receiving messages about sick sea lions. She immediately checked observation stations that take weekly sampling at piers up and down California’s coastline.
Anderson says having a bloom so late in the summer is unusual. “We expect that more to peak in April or May,” Anderson says because the organism is highly responsive to coastal upwelling – when high winds cause deep waters to rise to the surface, bringing up nutrients that the algae need to thrive – which typically happens in the spring.