Ocean heat wave brought 67 rare, warm-water species to North Coast
An extended ocean heat wave that spurred a series of ecological anomalies off the Northern California coast — including toxic algae, mass sea lion strandings and the collapse of the bull kelp forest — also promoted the northward migration of an unprecedented number of southern, warm-water species.
Sixty-seven rare, warm-water creatures, including 37 whose presence has never been documented so far north, were found in the region and points poleward, according to a UC Davis Bodega Marine Laboratory study published Tuesday in “Scientific Reports.” Everything from bottlenose dolphins to two kinds of sea turtles to barnacles and small sea snails were present during the study period between 2014 and early 2017.
One colorless, tiny snail cousin, the striated sea butterfly, hadn’t previously been seen north of the tip of Baja California. It turned up in sampling nets collecting whatever critters might be floating past the Bodega Bay lab, said lead author Eric Sanford, a UC Davis professor of ecology and evolution.
Similarly, pelagic red crabs — four still alive at the lab — that came ashore at Salmon Creek Beach in January 2017 normally would have been closer to Baja, he said. Also found in the bay was the molted shell of a spiny lobster more commonplace in Baja.
With the planet and the ocean warming, the recent, extended marine heat wave “provides a glimpse of what the Northern California coast might look like in the future,” as species move toward cooler environments to survive, Sanford said.
“We’re basically seeing these communities change before our eyes as more southern species become part of these communities,” he said. “That’s pretty dramatic.”
Most of the newcomers stayed temporarily in the north, departing the region once the water cooled. But a few stuck around off the Sonoma Coast, including the delicate-looking glass-spined brittle star — a leggy, bristled creature measuring about 2 inches tip-to-tip with deep orange markings that can still be found in local tide pools, researchers said.
Local tide pool explorers also might find for the first time blue-spotted chocolate porcelain crabs and sunburst sea anemones, which have radiating lines from their central discs, Sanford said.
Though marine heat waves already have increased in frequency and duration over the past century, the study period covers what’s believed to be the largest on record. It began with the formation of the “warm blob” in the winter of 2013-14 and later was reinforced by a strong El Niño driven north from the equatorial Pacific, according to the report.
What started as a persistent area of unusually warm water in the Gulf of Alaska expanded and spread south along the West Coast, raising water temperatures as much as 7 degrees and causing widespread upheaval.
While on land, Californians suffered unprecedented drought, the cold, nutrient-rich upwelling that traditionally makes the waters off the North Coast among the world’s most productive shut down. Reduced ocean circulation and warmer temperatures diminished the availability of tiny organisms that form the basis of the food web.
Scientists linked shifting migration patterns and mass mortality events among at least two kinds of seabirds to diminishing food supplies. Mass starvation also was evident among juvenile California sea lions. They were stranded by the thousands by mothers who, it was believed, could not find sufficient forage to feed their dependent offspring.