Thousands of Mysterious Blue Creatures Wash Up on Bay Area Beaches After Warmer Winters

Blue, jellyfish-like creatures called Velella velella have been washing up along California’s coast recently, captivating beachgoers and worrying climate scientists tracking stranding patterns.

Gabriel Speyer, who is a member of the South End Rowing Club, was swimming near Aquatic Park near San Francisco’s Ghirardelli Square on Wednesday when he noticed these peculiar creatures — also known as “by-the-wind-sailors” — stranded on the shore.

“There were thousands of dead jellyfish all over the beach,” Speyer said, adding that he also noticed them in the water while he was swimming. “They were all over the beach and in the water too. They’re like little rubbery blue-black discs, and when you’re swimming, they just float out of the way.”

Speyer said he had heard of these sightings occasionally but had never seen them for himself, especially in these amounts. “The trippy part was that so many of them had washed ashore. I’ve never seen something like that before,” Speyer continued.

These translucent organisms, related to the Portuguese man o’ war — a species of siphonophore closely related to jellyfish — use their small, stiff sails to ride the ocean waves. Unlike their venomous relatives, V. velella stings are relatively mild, according to Steven Haddock, a senior scientist at Monterey Bay Aquarium Research Institute.

When beachgoers see them on the shore, they’ve usually been washed up and have dried out, turning them even more translucent. But when they’re alive, the V. velella is a bright blue, purple or indigo. “They’re beautiful when they’re alive,” Haddock told KQED in 2023.

They mainly feed on plankton, including tiny fish larvae and zooplankton, by using their tentacle-like polyps, which dangle beneath their floating bodies, to capture prey. These polyps contain special cells called nematocysts that help them break down their food before digesting them.

V. velella are most commonly found on Northern California beaches in spring or early summer, according to Raphael Kudela, professor of ocean science at UC Santa Cruz.

“That’s because in the spring is when we have upwelling. Upwelling brings lots of nutrients and lots of nutrients bring phytoplankton and zooplankton.” Kudela said.

The upwelling concentrates the animals offshore, and then a change in wind patterns or ocean currents can push them ashore.

Recent rain storms and winds coming from the south and moving north have blown them ashore. “They don’t wanna be on the beach particularly, but they end up there because they can’t control where they go,“ Kudela said.

His forecast for continuing to see them in the coming weeks is rosy.

“I would say if we get a nice high pressure system, which is generally associated with nice clear skies, but also upwelling, it’s going to really concentrate them just offshore,” Kudela added. “And then all we need is a break in that — a low [pressure system] coming through or the high weakening — and then we would probably see a nice big raft of them come washing into the beaches. It’s kind of cool to see, they’re really beautiful.”

If it feels that they’re being seen more often along the coast, there’s a good reason.

They’ve always been around and they’re not particularly unusual, Kudela said. However, some research indicates that the frequency of seeing them is increasing over time. Scientists think climate change may be influencing these strandings.

Julia K. Parrish, marine biologist and professor at the University of Washington, studied Velella velella in 2021. Through community science data, she found a possible link between rising sea surface temperatures and increased strandings. “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,’” she told KQED in 2023.

While there is still a lack of concrete evidence, the rising sea temperatures linked to human-caused climate change may lead to more sightings of these disc-like creatures.

“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.”