Without notice, the waters off of California beaches will sometimes transform into a rusty-red color, driving surfers away.
It’s a massive, unpredictable bloom of single-celled, red plankton, and after an almost five-year absence, the red tide has again returned, and with it, glowing bioluminescent waves.
San Diego photographers, in long-exposure shots, captured the vivid, blue glow over the past few days, though the Scripps Institute said the bloom may now be moving north.
The tiny red creatures, called dinoflagellates, discolor the water during the day. That discoloration is most visible when the sun is directly or almost directly overhead, between 11 a.m and 1 p.m.
But in the evening, they produce a glowing, blue bioluminescence when they’re churned around by waves. It’s not known how long the bloom will last, or how far it might spread up the coast.
During red tides, the concentrations of these red, floating creatures can be as high as 20 million cells per liter, according to the Scripps Institute of Oceanography.
“It’s difficult to study an unpredictable event,” bioluminescence expert and Scripps scientist Michael Latz, said in a statement.
But now that the tide has returned, marine scientists are investigating.
Scripps researchers have been sampling the water to learn more about this species of red tide dinoflagellate, called Lingulodinium polyedra. The institute has also uploaded magnified images of the creatures, which you can see here.
Their bioluminescence, while an incredible sight for us, may serve the evolutionary purpose of frightening or driving off hungry predators.
“Dinoflagellate flashes cause a startle response in their predators, disrupting their feeding behavior and resulting in a decrease in grazing rate by reducing the number of dinoflagellates consumed,” the Scripps Latz lab says on their site.
Or, the flashes might grab the attention of another predator that then scares off the first, like a “burglar alarm.”
The actual mechanism that causes the tiny marine critters to glow isn’t fully understood, but Scripps researchers, after studying the dinoflagellates in the lab, know that each little cell, when stimulated by enough movement, flashes for about one-tenth of a second.
So, for those fortunate enough to see the glowing waves off California, just remember that you’re watching millions of dinoflagellates flashing, one after another, as waves tumble into the coast.