California marine mammal domoic acid poisoning

Marine mammals along the California coast are experiencing a health crisis linked to domoic acid, a neurotoxin produced by algae blooms. The Marine Mammal Center has reported receiving between 200 and 700 calls daily for sick or dying sea lions and fur seals across a 600-mile territory.

The toxin accumulates in small fish, such as sardines and anchovies, and causes severe neurological issues in mammals that consume them, including seizures, erratic behavior, and heart failure. In some instances, animals have died before rescue teams could intervene. The number of rescues this year has already exceeded the annual average for the region; the center reports having rescued more than 150 sea lions so far, which is more than double its typical annual total.

Recent reports highlight specific incidents of distress, such as a sea lion at San Francisco’s Crissy Field that exhibited ‘head weaving and bobbing behaviors’ before dying. Affected animals may also display lethargy, muscle twitching, and brain lesions. Environmental scientists, including UC Santa Cruz professor Dan Costa, suggest that warming ocean temperatures associated with El Niño may be contributing to the intensity of these blooms.

Beyond the impact on marine mammals, there are concerns regarding the commercial Dungeness crab season. Because crabs feed on similar algae debris, officials have scheduled formal testing for the crabs prior to the season opening in November to ensure they are not contaminated. Public health officials continue to monitor seafood safety, as consuming contaminated fish can cause severe illness or death in humans.