By day, a red tide is unsightly and uninviting, with water the color of coffee. But at night, during this unusual phenomenon caused by a plankton bloom, the waves are a brilliant, almost neon blue. This wonderfully surreal scene has played out almost nightly along San Diego beaches for several weeks, luring spectators with cameras and video recorders.


The bioluminescence is caused by a chemical reaction involving the phytoplankton Lingulodinium polyedrum, and the movement of the waves. In a Los Angeles Times story, Scripps Institution of Oceanography professor Peter J. Franks said of the phytoplankton:

"When jostled, each organism will give off a flash of blue light created by a chemical reaction within the cell. When billions and billions of cells are jostled -- say, by a breaking wave -- you get a seriously spectacular flash of light."
What's unusual about the current red tide phenomenon is that it has lasted nearly a month, to the chagrin of daytime swimmers and surfers, who don't like the color or the smell.

Though mildly toxic, the event is not harmful to humans, but a morning surf or swim is not nearly as refreshing as it can be without the plankton bloom. But at night, the glow of the waves is almost otherworldly. And of course, people are venturing out trying to ride the blue waves. (The below video shows what appears to be a largely unsuccessful attempt to surf in the bioluminescence.)

It remains unclear how long this particular event might last. Late Friday, the red tide appeared to be dissipating in some areas, while it remained strongly evident in others.