Coastwide
Janolus Nudibranch, National Science Foundation

Species by the dozen moved north during marine heatwaves

SAN FRANCISCO — Dozens of species of sea slugs, jellyfish and other marine life from toastier southern waters migrated into the Northern California region over an unusually long two-year period of severe heatwaves, says a new scientific report.

The 67 species identified in the report include a carnivorous sea slug that preys on other sea slugs and a sea snail "butterfly" usually spotted hundreds of miles away off the coast of Mexico. The study by the University of California, Davis is to be published Tuesday in Scientific Reports.

Not all the species stuck around, but the abundance of migration provides a glimpse of what the Northern California coast might look like in the future, said Eric Sanford, lead author and UC Davis professor.

"I've been working here for 14 years and before our very eyes we are seeing a shift in the local marine communities," he said.

The 2014-2016 period studied by researchers began in the Gulf of Alaska as a persistently warm patch in 2013 known as the "warm-water Blob" that spread south. Later, an El Nino event along the equator moved north, and the two factors led to unusually warm waters.

Temperatures in Northern California waters, which normally range from 50 to 55 degrees Fahrenheit (10 to 13 Celsius), increased 3.5 to 7 degrees Fahrenheit.

Larry Crowder, a professor at Stanford University's Hopkins Marine Station who is not affiliated with the study, said the report is impressive in documenting how species respond to change differently and, in some cases, dramatically.

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