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Coral-killing seaweed has medicinal benefits, researchers say

Jennifer Smith/Scripps Institution of Oceanography The properties that allow this cyanobacteria to kill coral also make it a potentially powerful medicine. 

California researchers have discovered that there may be a silver lining to an invasive and toxic seaweed that is killing some of Hawaii's coral reefs: It seems the seaweed contains compounds that could treat human diseases. 

"I think this finding is a nice illustration of how we need to look more deeply in our environment, because even nuisance pests, as it turns out, are not just pests," said William Gerwick, a researcher at UC San Diego and the Scripps Institution of Oceanography. "It's a long road to go from this early-stage discovery to application in the clinic, but it's the only road if we want new and more efficacious medicines."

The study appears in today's issue of the journal Chemistry & Biology.

The seaweed, a tiny photosynthetic organism known as a cyanobacterium, was identified in 2008 on coral reefs near the Pu’uhonua o Honaunau National Historical Park, off Hawaii’s Kona coast.

Researchers say it is native to Hawaii and generally inconspicuous. Indeed, they think a little of it is always around Kona's reefs.

It was first noticed during a routine survey of the coral, said Jennifer Smith, a co-author of the study and researcher at Scripps. “It was clearly smothering the corals at one of the most popular dive sites in Hawaii.”

Research on marine cyanobacteria shows that climate change can accelerate the organism's growth. It thrives in environmentally stressful conditions, such as UV exposure, high solar radiation and temperatures, and scarce or overly rich nutrients.

And on the reefs of Kona, the cyanobacteria was thriving. According to the researchers, the bloom was growing and suffocating the coral below.

Lena Gerwick, another co-author, said she and her team were unsure of the exact reason for the recent blooms, but they suspect runoff from nearby coffee plantations could be a factor.

In any case, the scientists took some of it home to find out more about it in their lab.

Lena Gerwick said the fact that it was overtaking the coral indicated that it had ecological advantages over the coral. And there were two theories put forward. The first was that the cyanobacteria was killing a beneficial film of bacteria that usually covers the coral and protects it from disease and pathogens. The second theory was that cyanobacteria was inhibiting the coral's immune system, making it susceptible to attack.

When they got into their La Jolla lab, they found the cyanobacteria generates compounds known as honaucins, which have both the bacteria-killing and anti-inflammation properties they had predicted.

Lena Gerwick said the researchers have now shown that the cyanobacteria can be used as an effective topical anti-inflammatory ointment for mice. And they hope that the combined activity – anti-inflammatory and antibacterial properties – can be used to fight diseases such as cystic fibrosis.

"It's a long shot, but that's just the kind of thing we work for," she said.

Filed under: Environment, Daily Report

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