Red tides are being spotted off the coast of San Diego, which means glowing bioluminescent waves may be coming back.
The first sign of a red tide is noticeable discoloration in the water. Oceans will appear bright red and blood red and can sometimes turn pink.
The cause of the red tides is an abundance of these "plankton super swimmers" called Lingulodinium polyedra. They form dense blooms that emit a reddish color and lead to dazzling displays of bioluminescence on beaches at night.
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Beachgoers who notice red tides during the day might extend their stay until the sun goes down to catch a glimpse of the marine phenomenon when the waves light up in neon blue.
Dr. Drew Lucas, an associate professor at Scripps Institution of Oceanography at UC San Diego, has researched the plankton species and their bioluminescent blooms. He spoke with NBC 7 to answer five commonly asked questions about the electric blue waves in San Diego.
What causes bioluminescence?
Bioluminescence is caused by tiny organisms that drift in the ocean called Lingulodinium polyedra. They are a species of motile photosynthetic dinoflagellates.
"They're like plants in the sense that they photosynthesize, but they're unlike most plants in the fact that they move around a bunch. They can swim," Lucas said.
In fact, they swim so well for their size that Lucas has referred to them as the Michael Phelps of the plankton world. Their strong swimming abilities are the reason they are able to take over the coastal ecosystem, turning the water red during the day and making it glow at night.
These organisms don't show off their glowing powers during the day. It's when nighttime rolls around, and they get physically disturbed — like from a breaking wave, a boat, a dolphin or a surfer — that they unleash their glow.
"That flash of light for each individual cell is not very bright, but when there's a lot of them in the water, that's when they really can light the waves up and lead to quite bright glowing," Lucas said.
More bioluminescence stories:
When can you see bioluminescence in San Diego?
First things first, it needs to be dark to see bioluminescence. Lucas says the organisms do not glow if they encounter light.
The natural phenomenon can happen at almost any time of the year, Lucas explained. But he's noticed a slight preference for spring to early fall.
If you're at the beach when there's a red tide, and you can't stay until the sun goes down, Lucas shared a tip to see bioluminescence from the comfort of your home. When there's a red tide, fill up a jar with some red water and put it in your fridge for an hour, creating a dark environment. Once you take the jar out, shake it, and it will supposedly light up.
Where can you see bioluminescence in San Diego?
Lately, Lucas says people have reported seeing the red tide in the mid to northern areas of San Diego County, from Del Mar to Oceanside.
He says he's seen a little bit of red in the water in the La Jolla area over the past few days.
"It is patchy. It does move around unless it's a very strong event like the one in 2020 ... In that case, it was literally everywhere," he said.
Because the red tide seems to move around, Lucas says the best way to know where to find the red tide is on social media.
How long does bioluminescence last?
The amount of time the red tides that cause bioluminescence lasts varies, but Lucas says they typically stick around for a couple of weeks.
"In 2020, the red tide was around for almost two months. Sometimes, it's only a night or two that is really bioluminescing at the beach," Lucas said.
If you plan to view the electric waves from the sand, the red tide must be in the breaking waves. Red tides that are offshore may be viewed from a boat.
Is it safe to swim in bioluminescent waters?
"It is my understanding that, in general, people tolerate swimming in the red tide just fine," said Lucas, who claims he has swam and surfed in it. "In a typical scenario, the bioluminescent red tide is not harmful to human health or even the ecosystem."
Red tides can impact the ecosystem at specific intensities. Interestingly, it doesn't have to do with the bloom but rather when the organisms start to die off.
"They start to decompose in the ocean, and that decomposition uses up all the oxygen, which can really harm marine life," he said. "There have been reports of it creating some amount of discomfort in people in terms of the smell and aerosols that are coming out of the water as the bloom is decaying."
But as of now, the red tides are in their growth phase.
Lucas' research on how Lingulodinium polyedra created a historic red tide and bioluminescence display in 2020 can be found here.
