California sea lions are affected by domoic acid toxin produced during harmful algal blooms. Climate-driven bloom increases are causing neurological poisoning events that require extensive rescue responses.
Domoic acid poisoning causes acute and severe welfare harms to California sea lions. Affected animals experience seizures, disorientation, and inability to thermoregulate or self-care. Stranded sea lions are found thrashing on beaches, often injuring themselves in seizure activity. Animals that survive initial poisoning may have permanent hippocampal damage affecting their ability to navigate — a profound long-term welfare harm for animals that depend on spatial memory for foraging. The Marine Mammal Center treats hundreds of cases annually, providing acute anticonvulsant therapy and supportive care. Climate change is amplifying this welfare problem by warming coastal waters that fuel larger and more frequent harmful algal blooms. This is one of the clearest documented examples of climate change causing direct, measurable welfare harms to wild animals.