UH student studying snowflake invasion
When he took a submarine ride over the black coral beds deep in Maui's Auau Channel last month, Dan Polhemus was shocked at what he saw.
Snowflake coral will be the subject of a talk -- "Carijoa riisei: Hawaii's Most Invasive Introduced Marine Invertebrate" -- Thursday at the Bishop Museum. University of Hawaii Ph.D. candidate Sam Kahng will speak on his dissertation subject 4 to 5 p.m. in the Paki Conference Room.
"I saw stands of black coral and they're not black, they're white," said Polhemus, administrator of the state Division of Aquatic Resources in the Department of Land and Natural Resources.
"There were very few of the black coral that weren't covered with snowflake coral," Polhemus said.
"The deeper you go, the more there is," he added. The coral appears to have "attacked that fishery from the bottom up, while divers were harvesting from the top down."
"These were obviously not isolated incidents," Polhemus said of what he saw from inside a Hawaii Undersea Research Laboratory Pisces mini-sub, and via the video from an unmanned underwater vehicle.
The scene was all too familiar to Sam Kahng, a University of Hawaii doctoral candidate who wrote his dissertation on the aggressive soft coral that was first seen in the state in 1972 and now has spread to every major island.
Since his academic mentor, Richard Grigg, first documented snowflake coral deep in the Auau Channel in 2001, Kahng has been going back to monitor it: in 2003, 2004 and, most recently, Oct. 21-27.
Kahng said he wouldn't want to rely on his visual perception as to whether the snowflake coral growth is worse now than two years ago. He said he will analyze the data he collected before saying whether the situation is worse than before.
Averaging the data from trips to the Auau Channel in 2001, 2003 and 2004, half the black corals below 70 meters deep were overgrown with snowflake coral, Kahng said.
"Where it is entrenched, there are very few options," he said.
At Kauai's Port Allen Harbor, Polhemus' division is leading a campaign to wipe out the interloper.
"If they are able to eradicate on Kauai, it would be a very good thing, because there are very pristine black coral beds there," Kahng said.
Black coral divers push their physical limits by diving with air to depths of 150 to 200 feet -- deeper than recreational divers -- to harvest the coral trees. The dangerous occupation has only a handful of practitioners in Hawaii. They provide the product that's the base of a $30 million jewelry-making industry.
The snowflake coral originally was believed to have come to Hawaii from the Caribbean, Kahng said. But genetic testing suggests it may have come from the Western Pacific.