What’s the mysterious brown substance appearing at Hawaii’s beaches?

Algae bloom on Kauai (Photo: Dept. of Health)

A mysterious substance is appearing at beaches across Hawaii.  It even caught state health officials by surprise.

They say the brown substance seen on the shoreline on Kauai is a Trichodesmium algae bloom.

It prompted a brown water advisory for the Garden Isle over the weekend.  It also showed up in Hilo Bay on the Big Island on Monday.

Eric Grabowski talks about Trichodesmium with the same passion that miners talk about gold.

“Because it’s not often that we see organisms that thick in the oligotrophic ocean so it was pretty exciting to come upon this,” said Grabowski, a U.H. Manoa Oceanography Dept. Research Associate.

He and his fellow researchers came upon a large Tricho bloom last week, about 20 miles north of Kahuku as they were heading back to Oahu from an expedition.

“And it looks like a sandbar out in the middle of the ocean,” Grabowski said.

It’s likely the same algae that made its way to Kauai and the Big Island in recent days.

And Grabowski said there’s a chance it could make its way to Oahu, but it really depends on the weather and the currents.

Tricho is found in Hawaii’s waters year-round, but it doesn’t always look that way, and in fact, most of us never come across it.

“So the reason it looks brown now is because it’s in really really high concentration,” said Matthew Church, a U.H. Manoa Oceanography Dept. Associate Professor.  “Typically what will happen is this organism will bloom in the summer in waters around hawaii but I don’t think it always washes in shore.  It sometimes gets diluted in the open ocean.”

“My guess is that combination of warm water and low wind allowed it to get concentrated at the surface,” he added.

Church said the Tricho bloom plays an important role in our ocean ecosystem.  “It captures nitrogen from the atmosphere and introduces it to the ocean water … it helps fertilize the waters around Hawaii.”

As for its effect on humans?

“I think in general it appears to be a pretty innocuous organism.  It doesn’t appear to be detrimental to human health,” Church said.

Still, the Department of Health is asking people to stay out of the water if you see this due to the possibility of swimmers itch.

But Grabowski says it didn’t bother him.

KHON2 asked: “Would you put your hand in the water if you saw it?”
Grabowski replied: “Sure.  I was putting my hand in the water.”
KHON2 asked: “And you weren’t getting itchy?”
Grabowski replied: “no.”

After all, finding the large algae bloom was like finding a treasure.

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