Ocean temperatures along the California coast have climbed up to 4°C above average, driving whales away from usual feeding spots, starving seabirds, and pushing great white sharks uncomfortably close to public beaches.Data from the US National Oceanic and Atmospheric Administration (NOAA) shows this marine heatwave has lasted for about six months. The heat is now linking up with El Niño, a weather pattern that warms surface waters across the central and eastern Pacific Ocean.Scientists worry this double hit could match or beat the damage seen during the 2015–2016 El Niño, which caused massive die-offs of ocean animals across the state.
A passenger on a whale watching excursion takes pictures of dolphins in the waters off Long Beach
Disappearing whales and hungry seabirds
When ocean waters stay warm, small fish like anchovies and sardines swim deeper or head north to find cold water. Bigger sea animals follow their food, leading to a sharp drop in whale and dolphin sightings near the coast.Sara Lesser, a 39-year-old naturalist at the Aquarium of the Pacific in Long Beach, watches these changes on daily tour boats.“The number of whales and dolphins we’re seeing is less than we would on a normal year,” Lesser told AFP, explaining that dolphins and whales “are going to follow their food, and so we’re seeing less sightings.”The problem goes far beyond missed boat tours. Nearby shores are already showing clear signs of trouble. Dozens of pelicans and cormorants were recently found dead near San Diego, matching the large bird die-offs from ten years ago.Andrew Leising, a research oceanographer at NOAA, warned that California’s sea lions could be next. During bad ocean heatwaves, mother sea lions have to leave their pups behind for longer periods to hunt for food further out at sea.
Toxic algae blooms and coastal shark sightings
Warm water also feeds big blooms of toxic algae that make a poison called domoic acid. The poison builds up inside sardines and anchovies, making the larger animals that eat them sick.In Monterey Bay, south of San Francisco, high poison levels caused two humpback whales to wash up dead on the beach in early June.Elliott Hazen, an adjunct professor at the University of California, Santa Cruz, said whale deaths from domoic acid poison had not happened in the area for ten years.“These are such large predators, it just highlights how much domoic acid there has to be in the ecosystem for it to affect them,” Hazen told AFP.While animals that need cold water swim away, young great white sharks are coming closer to shore to stay in warm, shallow water.During a recent boat trip run by the Aquarium of the Pacific, passengers saw a shark fin stick out of the water. “It’s not common for us to see them,” Lesser said. “But younger sharks like to be in warmer waters, and so we’re seeing sharks closer to shore.”These shark visits have made locals nervous. A Malibu resident filmed a young white shark swimming just a few feet from kids in the water, while Huntington Beach officers closed beaches three times this past spring due to aggressive sharks.
A juvenile humpback whale washed ashore after dying from domoic acid poisoning in Monterey Bay
Collapse of underwater forests and local fishing
Beyond animals you can see from the shore, the extreme heat is destroying plant life under the water. Giant kelp forests, which grow thick underwater canopies along the coast, break down and die in warm water.These kelp beds act as homes for hundreds of ocean species, giving young fish and crabs a safe place to hide. As the kelp dies, sea urchins multiply quickly and eat up the rest of the reef plants.Losing these kelp forests hurts local fishing towns. Salmon fishing is facing tough cuts because warm ocean water makes it much harder for young salmon to survive.At the same time, crab and clam fishermen face seasonal shutdowns because domoic acid poison builds up in shellfish, making them unsafe to eat.Even protected ocean parks cannot shield animals from rising temperatures. Research led by the University of California, Santa Barbara, shows that protected ocean areas are changing at the same rate as unprotected waters.As native cold-water fish disappear from coastal reefs, warm-water fish from the south are moving in to take their place, changing the state’s ocean food web.
Long-term climate pressure
California has seen marine heatwaves every single year since 2019, leaving little time for nature to recover between hot spells.“We know that climate change is adding more fuel to the fire,” Hazen said. “If we have these marine heat waves over and over again, and we lose the ability to sustain the ecosystem the way we have in the past, we’re going to lose some of the fish species that we rely on for food. So that’s the big concern.”
