A strong El Niño event forecast for this winter is expected to have significant impacts on marine ecosystems along the California coast, bringing with it both unusual marine visitors and ecological challenges. El Niño is a climate phenomenon characterized by unusually warm waters in the tropical Pacific Ocean, which can alter weather patterns and ocean conditions globally. Its effects on coastal waters typically include elevated sea surface temperatures and rising sea levels, driven by long planetary waves pushing warm water toward the coast.
One notable effect of El Niño is the appearance of tropical and subtropical marine species in waters off Southern California. For example, a whale shark was recently observed between Malibu and Santa Barbara Island, an occurrence consistent with previous El Niño-related sightings of uncommon species such as certain tuna species and open-ocean red crabs. Researchers have also noted the unprecedented nesting of olive ridley sea turtles on the West Coast, with nests laid in Seal Beach and Huntington Beach—marking the first known occurrences of their kind in the region. These eggs have since been relocated to a Long Beach aquarium for protection. Experts suggest that strong northward currents associated with El Niño may be transporting these species beyond their typical ranges.
El Niño also disrupts the region’s normal upwelling processes, which usually occur in spring and summer. Upwelling brings cold, nutrient-rich water to the surface, supporting abundant marine life and providing essential food resources for seals, sea lions, seabirds, and dolphins during their reproductive seasons. During strong El Niño episodes, altered wind patterns reduce upwelling intensity, causing a decline in available food. While adult marine animals can often adapt by expanding their foraging ranges, younger animals, particularly pinniped pups, are more vulnerable. Officials at the Marine Mammal Care Center in San Pedro expressed concern about a possible repeat of the 2013–2016 El Niño period, when thousands of underfed and distressed California sea lion pups stranded along the coast.
Another issue linked to El Niño involves domoic acid poisoning, caused by toxin-producing algae that proliferate under stressful conditions related to warmer waters and altered nutrient availability. Recently, sea lions affected by domoic acid have been found stranded from Monterey County to Sonoma County, raising concerns about a broader toxic bloom event accelerating under the current warm water conditions.
The health of giant kelp forests, which thrive in cool, nutrient-rich waters, is also at risk. Researchers note that changing storm patterns and more frequent severe winter swells damage kelp canopies, particularly during ocean warming and strong El Niño events. The loss of kelp forests threatens species that depend on these habitats, such as rockfish. Some scientists warn that continued warming may lead to the near disappearance of Southern California’s kelp forests within the next generation.
Experts emphasize that the current ecosystem differs markedly from past decades, suggesting that historical El Niño events may not reliably predict future conditions due to ongoing climate change and ocean warming. This evolving marine environment presents challenges for understanding and managing coastal ecosystems affected by El Niño's complex influences.