Prince might have been inspired by a beach visit this weekend at Point Reyes, where purple waves baffled beachgoers over the past week. The West Marin Feed, a local news source, shared a photograph from Point Reyes artist Marilyn Beck and suggested the hue might have emerged from a bloom of juvenile salps—a small, squishy ocean creature that uses jet propulsion to corkscrew in cloned chains across the ocean.
But is that what it was? “That’s not salp purple,” says Alejandro Damián-Serrano, a marine taxonomist in Spain who studied salps for years at the University of Oregon.
Various things can cause purple(ish) waves to crash this time of year, including Velella velella, everyone’s favorite sailor jelly, which has been washing up en masse. But while the surest bet is to pop samples under a microscope, Damián-Serrano and other ocean scientists who saw photos believe the culprit may instead be another ocean squishy—a weird little chordate called a doliolid that can upend marine food webs when it peaks.
Tidepool titan Eric Sanford, a UC Davis marine biology professor who runs a lab at Bodega Bay, told us that the waves at Point Reyes look familiar. Around the same time of year in 2015 and 2016, he and Jackie Sones (author of the blog The Natural History of Bodega Head, and research coordinator at the UC Davis Bodega Marine Reserve) saw similar purple waves off the Sonoma coast—and identified the translucent, centimeter-long critters in the water. Meanwhile, ocean researchers sampling right now off the California coast for the Applied California Current Ecosystem Studies program (ACCESS) scooped up enormous volumes of what they think are doliolids every time they’ve dropped a net into the surface waters. They’ve collected so much, says Jaime Jahncke, the director of the California Current Group at Point Blue Conservation Science, they can’t bring everything back to the lab for analysis.
The purple waves—and the mats of stinking purple goo they’ve deposited on Drakes Beach—are a mushy end for a delicate creature of extraordinary complexity. “They’re probably the hardest animal anyone can ask me to explain,” says Damián-Serrano. A doliolid goes through five different life stages before it gets to its adult form. This begins in a pretty standard fashion—one doliolid’s eggs are fertilized by another doliolid’s sperm, though every adult has both eggs and sperm—but gets rapidly weirder from there. The tadpole turns into a form called a “nurse,” which sprouts a tail-like structure that in turn buds off two more varieties of doliolid. Together, the three doliolid forms—nurse and the two kinds of buds—“become a super organism,” explains Damián-Serrano. The first kind of bud, which an article describes as “spoon children,” is in charge of foraging. The other feeds off that nutrition to eventually break off; each one eventually buds in turn into dozens more of the translucent, vaguely purple, barrel-shaped adults. Damián-Serrano says it’s the bud that breaks off, and the adults it produces, that look purple and make up the blooms.
All in all, egg to adult takes about 23 days. One doliolid can turn into several thousand in that period. They can completely reshape the ecology of the places they swarm: they eat almost anything, from microbes to small eggs to phytoplankton sucking carbon dioxide out of the atmosphere. (“They are pooping machines,” according to Damián-Serrano, and their pellets are a key store of climate-warming carbon.) And given their gluttony, doliolids make a tasty and nutritious meal for baby fish and different kinds of jellies.
But for the most part, the creatures’ fragility has made them a difficult subject for researchers to study. So it’s hard to know where a purple wave is going to strike next, as summer rolls around and the ocean heat makes our coasts less predictable. The only solution, if you hope to bear witness? More beach days.
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