One of Southern California’s worst harmful algae blooms on record has finally subsided, after killing hundreds of dolphins and sea lions along the coast. 

Levels of toxic algae have dropped below dangerous thresholds, offering temporary relief—but scientists warn the threat isn’t over. This year’s bloom arrived unusually early and may return, fueled by nutrient-rich upwellings and possibly intensified by firestorm runoff. 

The outbreak featured four toxic algae species, including two that produce powerful neurotoxins, poisoning marine mammals through the food chain. Pregnant sea lions were hit especially hard, with none rescued delivering live pups. 

Experts say the full ecological impact—especially after four consecutive bloom years—remains unclear. With climate change shifting ocean patterns, these lethal events may become the new normal.