Strange sea 'sailors' wash ashore on Pacifica beaches

Some beachgoers were wary of the waterline — which was littered with the strange creatures — while a surfer trod barefoot over a few without concern. When asked if they had stung the bottoms of her feet, she just smiled and shook her head.

While many surfers seemed unfazed, other people stood far from the breaking waves. Do these beings deliver the sting of a jelly, for which they could easily be mistaken? Why have they appeared here, and why now?

The most pressing question is the most basic: What in the world are these oceanic aliens?

Readers who have spent more time along the water's edge might already know that these blue jelly-like creatures are named Velella velella, also known by their more colloquial name, "by-the-wind sailors." This is an apt description as a semi-translucent sail is one of its most immediately obvious features, and takes advantage of the wind to travel long distances across the open ocean.

“The part that people see washed up on the beach is a raft,” wrote Monterey Bay Aquarium marine biologist Steven Haddock in an email to the Tribune. “To reproduce, they also can bud off tiny ‘medusae’ jellyfish (from the raft) … A fertilized egg from one of these tiny jellies will develop into a raft of polyps, completing the life cycle.”

The rich, dark-blue color has been proposed to be both camouflage and a protective layer against the sun's rays, from which Velella can’t hide as they float along the open waters.

"The blue color is a pigment which reflects the short wavelengths of the sun,” Haddock said. “Shorter wavelengths — even if not truly ultraviolet — are more energetic and potentially more damaging to tissues.” This long trek is more about the voyage than the destination: Velella are at the mercy of the winds that clump them together and completely lack the ability to navigate in their raft form. According to Haddock, the Velella simply “drift passively with the wind” while in their raft form.

Velella spend their existence bobbing on the surface spawning jellies into the oceanic abyss below. This surface lifestyle earns Velella the designation of being labeled a hydrozoan, same as the dreaded man o' war (Physalia physalis), famous for its excruciatingly painful sting. They are a subset of the wider family of stinging Cnidarians that includes coral, sea anemones and normal jellyfish. While Velella are not harmful upon contact with human skin, Haddock stresses that “they can still irritate sensitive areas, like your lips or certainly your eyes.”

Mass beachings of Velella such as the one on Pacifica State Beach occur due to persistent springtime winds in conjunction with other chance environmental factors. Haddock explained that the temperature of the water and the consistency of winds are just two factors that can contribute to mass beachings. Climate.gov reports that El Niño is “knocking on the door” as the surface water of the Pacific warms. El Niño events occur about once every five years when a band of warm ocean water develops in the Pacific, creating freak weather events that wreak havoc all across the globe. 

Longtime residents will recall the powerful waves brought on by the 1983 El Niño that nearly swallowed houses along the shoreline of Pacifica State Beach. More recently, apartment buildings in the Manor neighborhood had to be demolished after the cliff they sat on threatened to collapse after the abuse of the 2016 El Niño storm season.

One week after their initial landing, all that was left of the Velella were colorless skeletons quickly being covered by the shifting sands. Their sudden appearance, however brief, provided Pacificans with a rare glimpse of life on the other side of that watery border, a peek into the vast and wondrous ecosystem of marine life that exists just off the coastline.