Environment

Here’s why the ocean at Avila Beach is a weird color right now

If you’re heading to Avila Beach this weekend, you might want to think twice before getting in the water.

That should be easy since it’s an off-putting, rusty red right now.

A red tide has rolled into Avila Beach and Port San Luis Harbor District waters, giving the Pacific Ocean a distinctly bloody hue.

“It’s spectacular to see,” PG&E meteorologist John Lindsey told The Tribune. “It looks like a fairly large event. From Harford Pier all the way to Avila Pier it was present.”

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An algae bloom is turning the ocean a reddish, dark brown in Avila Harbor. Laura Dickinson ldickinson@thetribunenews.com

What is red tide?

Red tide is caused by microscopic phytoplankton, or, marine algae, that have amassed in the coastal waters, according to Lindsey.

Strong gale force winds off the coast have produced “tremendous amounts of upwelling” which brings nutrient-rich water from the bottom of the ocean to the top, he said.

That nutrient-rich water acts as a great buffet for the phytoplankton, Lindsey said.

“It has pretty much unlimited fertilizer,” he said. “Combine that with the sunshine and there you go.”

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An algae bloom is turning the ocean a reddish, dark brown in Avila Harbor. Laura Dickinson ldickinson@thetribunenews.com

Health risks for people

Although the phytoplankton bloom isn’t generally dangerous, Lindsey said, people should avoid swimming in red tide water because some can be allergic to it.

“The best piece of advice is just to avoid it,” he said.

Lindsey added that the biggest risk with red tide is possible toxin buildup in mussels, clams, scallops and oysters, which can cause diarrhetic shellfish poisoning.

Symptoms of diarrhetic shellfish poisoning include “incapacitating diarrhea, nausea, vomiting and abdominal pain,” according to the Woods Hole Oceanographic Institution website.

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An algae bloom is turning the ocean a reddish, dark brown in Avila Harbor. Laura Dickinson ldickinson@thetribunenews.com

Glowing ocean waves

At night, people might also notice some bioluminescence, or bright blue glowing waves, which happens when the phytoplankton are agitated.

The water could retain its reddish hue for the rest of the week and into next Tuesday, Lindsey said, depending on weather conditions.

“I think the red tide is going to stick around for a little while,” Lindsey said.

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Kaytlyn Leslie writes about business and development for The San Luis Obispo Tribune. Hailing from Nipomo, she also covers city governments and happenings in the South County region, including Arroyo Grande, Pismo Beach and Grover Beach. She joined The Tribune in 2013 after graduating from Cal Poly with her journalism degree.
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