The blue ocean has turned a rusty red hue—but what is causing the ocean to turn colors?

The red tide, as it's called, is from an algal bloom, according to Valerie Hill, administrative and development director at the Roundhouse Aquarium off the Manhattan Beach Pier.

It was first spotted by one of her co-workers last Thursday, Sept. 5, and stuck around through the weekend. By Monday afternoon, winds had pushed the reddish water north of the pier.

"It's a bit breezy out here today, the wind is creating some chop and breaking it apart a bit," she said.

The tiny plants—called phytoplankton—live in the ocean regularly, producing oxygen that we breathe, Hill explains.

"Sometimes they go a little nutty with their reproduction, we don't always know why," she said. "There are always different theories. When those phytoplankton bloom, they reproduce really fast and you can see their color, a reddish brownish color. You see them because there’s so many of them."

Don't worry if you accidentally swallow some while swimming or get some in your nose while surfing.

"Usually there are harmless, especially if you are just swimming," she said. "There are some type that are harmful, that is usually due to a food chain bioacculumation. Just swimming shouldn't cause a problem. If a bit of water gets in your mouth, it's not a high enough concentration to make you sick."

There's many kinds of phytoplankton in the water, one that always gets attention is the bioluminescent dinoflagellates that, when moved by water or waves, glow neon blue at night, though there's been no word if the latest red tide has those properties.

The last time bioluminescence was seen was seen off Southern California was May 2018 off the San Diego coast. 

There's also been worry recently about large algae blooms that can be harmful to marine mammals, causing a “domoic acid” outbreak that affects anchovies and sardines that stranded and caused a large number of sea lion and dolphin stranding and deaths.

A marine heatwave announced last week by the National Oceanic Atmospheric Administration flagged concerns about recently detected warmer-than-normal waters possibly causing such algae blooms like occurred in 2014 and 2015 with "the Blob."

But Hill said until she can get some samples, she didn't want to speculate what species the pytoplankton may be or whether it could be harmful.

"Some species are harmful, some are totally harmless," she said. "If I was able to get a sample right in the bloom, there would probably be more of one or two species, and I would be able to identity them."

Hill and others will be watching the water this week to see if the red tide sticks around.

Contact Lisa Jacobs lisa.jacobs@TBRnews.com or follow her on Twitter @lisaannjacobs.

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