Red Tide Envelops SoCal

A Scientist dispels the myths about the brown water in San Diego

Southern California surfers have made a point to stay out after sunset for rave-inspired sessions over the last few weeks. Photo: Gilley

By day, Southern California surf has shown shades of red and brown, swamp-esque water that raises Contagion-like fears every time you get in. But by night, the waves glow neon tones of blue and green, akin to an underwater disco where the plankton are the party.

Red tide has swept through San Diego and Orange counties, an algae bloom spreading phosphorescent phytoplankton up and down the coast.

The bioluminescence does play a role in the food chain—it's a defense mechanism. Apparently the glow not only deters natural grazers of these dinoflagellates, but also attracts those organism's predators, who, like us, are attracted to the light.

The scientists say it isn't harmful, contrary to most rumors. Red tide looks and smells dirty, but the bacteria level in the ocean stays roughly the same.

Some avoid duck dives and head dips to keep their insides algae free, others freely ingest the water, curious if it will glow on the way out the next day. Regardless, it's inspired many to throw their wetsuits on for late-night sessions lit by the sparks of the algae, where every wave feels like a science experiment.

SURFER Magazine caught up with Dr. Peter Franks of UCSD's Scripps Institute of Oceanography for more information and to double check that we won't get sick:

Many are claiming this as one of the heaviest red tides in decades. What's your theory on the cause of such a strong bloom in the area?

The organisms that form this red tide are phytoplankton—tiny single-celled plants. Like terrestrial plants they require light and nutrients to grow. It is likely that this red tide was preceded by some sort of injection of nutrients into the upper layer of the ocean. This could have happened through an uplifting of the deep, nutrient-rich waters by a variety of physical forces. Some of these forces are local (enhanced mixing) and some are remote (winds off Baja). At this point we don’t have any conclusive evidence to support any particular mechanism as being responsible for the red tides we get in Southern California. It is likely a very complicated combination of physics, chemistry and biology. We have been getting red tides in this region since before recorded history—they are natural phenomena—but they are very difficult to sample because they are so unpredictable.

How long do you think it will last?

The organisms forming this red tide are very sensitive to turbulence. So if we get a particularly windy day, the red tide might disappear in a day or two. The red tide-organisms are also being eaten by other organisms, and killed by bacteria. Once the mortality becomes higher than their growth rate, the red tide will disappear. It could be gone in a day, or it could last a month or more. It is as unpredictable as the weather.

How would you explain to a surfer that red tide won't kill them? That's true, right?

Many red tides are extremely toxic and can kill people who eat shellfish that concentrate the toxins. This particular organism contains no toxins that are known to affect humans. If you drink the water you’d die from salt poisoning long before you died from phytoplankton toxins. However, the organic material that is secreted by the red-tide organisms may help to prolong the life of human pathogenic bacteria in the ocean, potentially increasing the possibility of being infected by one of them. Many people have written to tell me that they suffer an allergic reaction to red tides. I have never heard of this being investigated carefully, and it would be worth trying to identify the compounds that people are reacting to. They may be from the red-tide organisms, or they may be from bacteria or other organisms that grow during a red tide.

Have you gone in the water at night yet?

I haven’t (I’ve been traveling) but I’ve heard wonderful stories from people who have been swimming in the red tide at night. It’s seriously spectacular! But don’t go in alone—it’s dangerous to swim alone at night.