A long green slick off Hawaii has folks perplexed. Here’s what it is.

A long green slick off Hawaii has folks perplexed. Here’s what it is.
This slick seen off the Big Island perplexed a viewer. (Image: Mike Hackett)

HONOLULU, Hawaii (HawaiiNewsNow) - Mike Hackett was flying from Maui to Kona this week when he saw something strange in the water: A huge green slick situated right off the Kohala Coast.

He said it went on for miles and miles ― as far as the eye could see.

And the pilot of the craft he was in told him that it had been there for days, and that she’d seen it extend all the way to Oahu waters.

Perplexed, Hackett headed to Facebook with a question: What is this?

Folks had lots of guesses: Runoff. Trash. Oil.

Several people also said they’d also seen the green slick during recent flights around the islands.

One Facebook user quipped: “It’s definitely from another planet.”

Hackett also sent his photo to Hawaii News Now, and we shared it with Dave Karl, a professor of oceanography and the director of the Center for Microbial Oceanography at the University of Hawaii.

Karl instantly recognized the green slick ― and it wasn’t alien.

It was likely a bloom of the water-dwelling Trichodesmium, he told HNN. Trichodesmium is a cyanobacteria, an aquatic bacteria that gets energy from photosynthesis.

Scientists at the university have been studying Trichodesmium in Hawaii waters for decades.

And in the summer, especially when tradewinds die down, the cyanobacteria float to the surface and produce “these beautiful (to some people, like us) surface slicks,” Karl wrote, in an email.

“The lines then form due to local wind and currents.”

Trichodesmium blooms, in some cases, can stretch for hundreds of miles. It’s not quite clear how large the bloom that Hackett captured from air is.

What is clear: The bloom is made of up lots and lots of very tiny organisms.

(Image: Angelicque White)
(Image: Angelicque White)

Angelicque White, an assistant professor of oceanography at the University of Hawaii, included some images of Trichodesmium as they’d be seen under a microscope.

“This organism is quite beautiful up close,” she wrote.

Karl said University of Hawaii scientists first encountered a large bloom of the organisms in 1989 off Hawaii, but added they’ve been reported since the early 1800s in tropical and subtropical seas.

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