Many people have noticed the current “red tide,” a brown layer of water just offshore along Pacific Palisades and Southern California beaches.
Scientists say that it is caused by a “bloom” of phytoplankton, which are microscopic single-celled organisms that occur naturally in coastal waters. They are called dinoflagellates, and when they become concentrated in large groups, they discolor the ocean water, resulting in the red-brown color.
According to an April 30 story in Surfer (“Why Do Waves Glow During Red Tide, Exactly? We Had Questions, So We Called Some Algae Scientists”), the red tides show up when it’s hot and after it has rained.
UC Santa Cruz professor Dr. Raphael Kudela, who has focused much of his research on monitoring water quality, phytoplankton population dynamics and harmful algae blooms, said, “We’ve looked at it in experimental conditions, and this particular type of dinoflagellate (algae) likes nutrients that are in runoff, and it really likes nice warm temperature sunny days. That pretty much describes San Diego [and other areas of the coast] right now.”
Richard Stumpf, an algar blooms expert at the National Oceanic and Atmospheric Administration (NOAA), says red tides tend to occur in Florida every year. In Texas along the Gulf Coast, they used to bloom every ten years, but now appear every three years.
The “red tide” that has Pacific Palisades residents traveling to the bluffs at night and along Will Rogers State Beach is an amazing bioluminescent phenomenon.
Thursday night there were easily more than 100 people on the beach, practicing safe distancing and wearing masks, as they looked for a neon blue light that is easily seen when the water crashes into the beach. The neon blue waves and the full flower moon were spectacularly beautiful.
According to Dr. Alexis Fischer, a research associate and surfer at Santa Cruz: “This particular type of phytoplankton produces bioluminescence when it’s agitated. These flashes cause a startle response in their predators, and so is thought to be a predator avoidance behavior. However, any sort of mechanical stress, like waves, can also trigger the luminescence.”
How long will it last? According to Kudela, typically a couple of weeks.