California's coastal waters heat up 4 °C, pushing whales away and drawing sharks near shore

Data from NOAA show that sea surface temperatures along the California shoreline are up to 4 °C hotter than average, sustaining a half-year heatwave that now coincides with an El Niño pattern. The warmth drives anchovies and sardines to deeper or more northern waters, leading to a steep decline in whale and dolphin observations, as noted by naturalist Sara Lesser. Toxic algae blooms fueled by the heat have elevated domoic acid levels, killing two humpback whales in Monterey Bay and contributing to recent pelican and cormorant deaths near San Diego.

Researchers warn that sea-lion mothers may have to abandon pups longer to forage. Meanwhile, juvenile great white sharks are appearing near Malibu and Huntington Beach, prompting safety concerns and temporary beach closures. The heat also devastates kelp forests, allowing sea urchins to overrun reefs and harming salmon, crab and clam fisheries. Scientists stress that repeated heatwaves, intensified by climate change, could permanently alter California's marine ecosystem.