For the last week, scientists from the University of Hawai‘i and the state Department of Land and Natural Resources have dove off South Kaua‘i to try to eradicate a deadly, introduced coral species that threatens Hawai‘i’s $30-million-a-year black coral industry.
For the last week, scientists from the University of Hawai‘i and the state Department of Land and Natural Resources have dove off South Kaua‘i to try to eradicate a deadly, introduced coral species that threatens Hawai‘i’s $30-million-a-year black coral industry.
The snowflake coral, scientifically known as Carijoa riisei, has laid waste to black coral found in deep waters in Hawai‘i. The black coral provides the raw material that is used to make coral jewelry that is sold in Hawai‘i and throughout the world
With scientific surveys and data, the divers found the snowflake coral at two spots off west and south Kaua‘i and began eradication efforts.
While much more work has to be done at the two sites, divers don’t think the coral has spread beyond the sites. Yet, the researchers aren’t entirely sure.
“Due to the limited sightings, we are going on the assumption its presence is limited,” said one of the divers, Anthony Montgomery.
With the exception of Kaua‘i, the snowflake coral, called so because of its white gelatinous polyps with tentacles that fan the water, has thrived in deep water off O‘ahu, the Big Island, Moloka‘i and Maui.
If future eradication efforts aren’t stepped up to halt the advance of the coral on the shores of Kaua‘i, the coral will be headed for virgin territory – the Northwestern Hawaiian Islands, a repository of rich marine resources.
“If nothing is done (on Kaua‘i) we are basically forfeiting the island, as was the case with Maui and the Big Island,” said Sam Kahng. Stopping the coral in its tracks on Kaua‘i would be unprecedented, Kahng and Montgomery said.
Kahng is pursing a doctorate degree in biological oceanography with the University of Hawai‘i Department of Oceanography.
The dive team consisted of Kahn; Montgomery and Paul Murakawa, both aquatic biologists with the state Department of Land and Natural Resources Aquatic Resources Division, Jason Leonard, a fisheries specialist with the same division, and Decy Devere, a diver with the University of Hawaii.
They were assisted by Wade Ishikawa, a staffer with the same division on Kaua‘i.
As part of the eradication effort, the researchers came to Kaua‘i to map out the location of the snowflake coral and to determine the size of the infestation and the amount of time and resources needed to eradicate the coral.
The DLNR division funded the pilot project partly because of the intuitive of Kahng, a specialist on snowflake coral, “the timing of it (the project),” and other considerations, Montgomery said.
Funding for future work is anticipated to come from the National Oceanic Atmospheric Administration, Montgomery said.
The team arrived on Kaua‘i on Monday and left Thursday.
The divers located the Kaua‘i sites with the help of surveys done by Bishop Museum and with reports by a Kaua‘i dive company, Montgomery said.
The divers found the largest amount of the snowflake coral in south Kaua‘i, a discovery that didn’t jolt them but gave them cause for concern, Montgomery said.
“There is a lot. We don’t have all the analysis. What we found is enough to be of concern,” Montgomery said.
Montgomery and Kahng relish the chance to stop the spread of the coral on Kauai, “because there is so little of it.”
The coral hails from areas in the western Atlantic and parts of the Caribbean.
The snowflake coral is believed have come to Hawai‘i on the bottom side of ships or as larvae in a vessel’s ballast water.
The coral was first discovered in waters at Pearl Harbor on O‘ahu in 1972. The discovery was made by biologists who suspected the hulls of ships were “fouled” by the coral, Kahng said.
Since 1972, the snowflake coral has multiplied and spread in Hawaiian waters.
Kahng theorizes the infestation has accelerated in Hawaiian waters in recent years because “there are more ships (with the coral) traveling to Hawai‘i and because they (the ships) can travel faster due to technology.”
The coral, if allowed to go unchecked, could decimate the black coral. The coral covers the black coral and removes the rust-colored or red-colored tissue off the latter, leaving a skeletal frame, Montgomery said.
Scientists have found that certain black coral beds in Hawai‘i have been turned into “graveyards” by the species, according to a report done by Kahng.
While Maui boasts having the largest commercial black coral beds in Hawai‘i, Kaua‘i has the largest non-commercially-harvested black coral beds in the state, the researchers said.
The snowflake coral strikes black coral beds that live at depths of 250 feet and more.
Healthy black coral beds “seed” higher-elevation areas, but if they are killed off by the snowflake coral, the black coral population can be greatly diminished, though probably not entirely killed off, Montgomery believes.
In the short term, the work of the snowflake coral will cause substantial harm to Hawai‘i’s black coral industry, Montgomery and Kahng.
What long-term impacts the coral may have on the marine environment is unknown, and therefore, a little scary, Kahng said.
“We don’t know what all the impacts might be,” he said.
Kahng said he hopes to have the findings from the work, which is ongoing, published in scientific journals. Also, he hopes the coral eradication plans or control methods used on the Kaua‘i dive will be put in practice statewide.
The divers manually removed the troublesome coral, clearing large clumps in some areas and removing all of the coral in other areas, Kahng said. The idea was to see which method proved more successful.
In his report, Kahng said the snowflake coral feeds on zooplankton and organic particles by capturing them with tentacles.
The coral’s shape is unique among coral, as its polyps have eight tentacles as opposed to six in most stony corals.
The snowflake, which attacks to surfaces with root-like structure, likes darkness, Kahng said.
At depths where light cannot penetrate significantly, the coral can spread like carpet on rocky surfaces that have been swept clean of sediment. The coral also can grow close to shore, under pilings or bridges, as long as they are away from light, Kahng said.
The snowflake coral will thrive in currents that bring them zooplankton.
The coral, or cousins to it, have apparently left their imprint in areas of the Pacific other than Hawai‘i.
A species of the coral has been reportedly found in the Western Pacific and in waters off Australia and Asia.
Based on reports, there may be at least one or more different species of Carijoa that is native to Australia, Kahng said.
For more information: Contact Kahng at kahng@hawaii.edu or Montgomery at Tony.Montgomery@hawaii.gov or at 1-808-587-00365.