Blue, translucent Velella velella washed ashore on Ocean Beach in San Francisco on May 18, 2023. (Beth LaBerge/KQED)
Surfers and beachgoers across the California coast have recently been treated to a mesmerizing spectacle: countless blue jellyfish-like creatures riding waves and washing up on sandy beaches.
These captivating organisms, known as “by-the-wind sailors,” are Velella velella and they possess striking blue translucent bodies. They thrive in large numbers, primarily in the northern hemisphere.
“They have a little stiff sail that sticks up from their floats and they use these little sails to capture the wind,” said Chrissy Piotrowski, senior collections manager of invertebrate zoology at the California Academy of Sciences.
They are related to the fearsome Portuguese man o’ war, often mistakenly identified as jellyfish. Still, unlike their notorious cousins, Velella velella stings are relatively mild, according to Steven Haddock, a senior scientist at the Monterey Bay Aquarium Research Institute.
“From our human point of view, we think of them as invading our shorelines, but that doesn’t necessarily reflect the actual populations that are offshore,” he said.
These ethereal beings resemble little sailboats and wash up on shore when ocean temperatures warm up and onshore wind events occur. The recent surge in the strandings of the see-through blue sea creatures could be a consequence of human-caused climate change.
“When we see them a lot, it’s sort of like they’re putting up a huge billboard that says, ‘Hey, pay attention, things are changing,’” said Julia K. Parrish, a marine biologist and a professor at the University of Washington, who examined the creatures in a 2021 study.
Her research utilized community science data, analyzed stranding reports and found a potential association between rising ocean temperatures and the frequency of these events. Although concrete proof is yet to emerge, the warming trend in sea surface temperatures with links to human-caused climate change could mean more sightings of these azure, disc-like creatures.
“A warmer ocean along the coastline means that those organisms that normally live around California are going to start to move north,” she said.
She said one instance of a mass stranding isn’t enough to attach climate change as the reason behind the organism washing ashore. But when looking at an increase in strandings over the past two decades, Parrish said the case for the climate link is growing and more research is warranted to gain a greater understanding of the impact anthropogenic climate change has on the species.
“When we see signals coming from the ocean to the coast, we should pay attention,” she said. “The Velella velella is an early-warning bell that we may be seeing some shifts.”
Conditions for Velella velella strandings may increase over the next year. Brian Garcia, warning coordination meteorologist for the National Weather Service Bay Area and Monterey regions, said the current onshore wind events would likely become more robust.
“If you just pull back a little bit and blur your eyes, it’s been pretty much onshore for months,” he said. “We’ll see warm waters sticking around with us probably until next spring into next summer.”
KQED’s Sarah Mohamad contributed to this story.
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