Sea lions are stranding themselves on a long stretch of the California coast in what experts say could be a sign of widespread poisoning by a harmful algae bloom this summer.

The Channel Islands Marine & Wildlife Institute said that since 26 July, it has been inundated by daily reports of sick sea lions along the shoreline in Santa Barbara and Ventura counties.

The marine mammals are suffering from domoic acid, a neurotoxin that affects the brain and heart, the institute said in a statement. The poisoning event is largely affecting adult female California sea lions, it said.

The nonprofit said it had rescued 23 animals so far. Coastal Vandenberg Space Force Base released photos of sea lions being rescued from one of its beaches this week.

“Rising ocean temperatures and excess nutrients are fueling these blooms, producing toxins that enter the food chain through small fish,” Vanderberg Space Force said in an Instagram caption that accompanied photos of a stranded seal being treated by wildlife officials.

“Local efforts, including monitoring and rescue initiatives, are in place to mitigate the impact.”