Navy to start ‘large-scale’ effort to remove invasive coral at Pearl Harbor

The Navy is preparing for a large-scale removal effort of a problematic invasive coral that covers around 80 acres at Pearl Harbor.

Unomia stolonifera is a species of “octocoral,” also known as “pulsing coral” or “stoloniferous fire coral,” and was first detected in the harbor in 2020.

Experts have said it’s likely the coral was introduced at two different sites at the harbor, where they believe aquariums were dumped into the water. The invasive octocoral is a popular aquarium species.

It’s not hard to see why its tentacles can be mesmerizing — as they appear to dance and sway in the water.

But now it’s threatening Hawaiʻi’s reef ecosystem.

“The situation with the pulsing coral in Pearl Harbor is an absolute environmental emergency. There is no doubt about it. It can fragment easily and spread,” said Christy Martin, program manager for the Coordinating Group on Alien Pest Species. “The most important thing we could be doing (is) to eradicate that, because you know it will fragment, it will spread to the rest of our reef.”

The fast-growing invasive coral can easily spread and overrun an area if given the opportunity. It’s a soft coral that can settle and spread on hard surfaces. That includes hard stony coral, which forms reef fish habitat. The invasive species can grow over the hard stony coral, suffocating it.

In turn, that can disrupt entire ecosystems and cause significant problems for reef fish populations.

That’s what’s happening along the coast of north Venezuela, where the coral covers hundreds of acres of reef after its introduction to the area in the 2000s through the illegal aquarium trade. It’s also spreading in the Caribbean Sea.

Pearl Harbor is being similarly impacted.

Over the last few months, the Navy has been testing different methods to kill the octocoral in the harbor. Mechanical removal alone isn’t effective because the coral can fragment and start growing in another area.

But the Navy believes it’s found a successful way to eradicate it — by smothering the coral with heavy tarps. In test trials, it placed tarps over the coral and weighed them down, keeping oxygenated water from reaching anything underneath.

It takes a little over a week to kill the coral after covering it with tarp.

“The tarps are effective. Once you lay it down, you keep the sandbags on top, and then when you remove the tarp from the area, the octocoral has been successfully suffocated,” said Nicole Olmsted, a Navy conservation manager.

The Navy is shipping in more of the tarps and other material for a large-scale removal effort that it plans to start next month.

The tarps will cover one part of the affected reef at a time. After the octocoral is dead in that area, the Navy will move the tarps to another spot and repeat until the coral is completely removed.

If the effort is successful, it would not be good just for Hawaiʻi but could also help other areas where the coral has taken over. There hasn’t been a proven method to eradicate the octocoral in places it’s been able to establish itself, Olmsted said, so it could become a case study for the tarp method to be used elsewhere.

Olmsted said the removal could take years, but that complete eradication is still possible.

“The goal right now is eradication. It might shift towards some other containment or something, depending on how this large-scale effort goes,” she said.

But it’s also dependent on the funding the Navy decides to allocate to it in the coming years, Olmsted said.

The Navy declined to provide Hawaiʻi Public Radio with any costs associated with that effort.

Local agencies and organizations are also hopeful for eradication but are more hesitant about their outlook on the military’s ability to stop the octocoral from spreading — let alone completely remove it from Pearl Harbor.

“Eradication is very difficult. While that is the U.S. Navy’s goal, there are vessels going in and out of the harbor. There are all these different vectors and all these different implicating things that could lead to it spreading,” said Jesse Boord, a biologist for the state Department of Land and Natural Resources’ Division of Aquatic Resources.

Animals attaching to boat hulls, known as biofouling, is one of the most common ways aquatic invasive species are introduced to and spread in Hawaiʻi, DAR officials said.

That means Pearl Harbor, an active Naval Base, can easily spread the octocoral.

The DLNR, the military and other agencies are part of a working group in which the Navy provides regular updates on the situation. But DAR officials said that’s the extent of their involvement, which has been a source of frustration to groups that want to help eradicate the coral.

The Navy has limited other groups from getting into the harbor waters. The Navy only lets its divers do coral removal, surveying and other octocoral-related work. Olmsted said it’s mostly an issue of safety.

DAR has been surveying the waters outside Pearl Harbor and outside federal jurisdiction, just in case the octocoral does spread further.

DAR has so far not found any more cases of octocoral.

Boord said the situation is hopefully a lesson in communication. He said the Navy knew about the octocoral for about a year or two before letting state agencies know. In that time, other agencies could have helped respond more rapidly to the situation.

The agencies are working together to urge the public not to dump their aquariums into the water. Local organizations recently held a “Don’t Let It Loose” campaign to stem what’s been a growing issue in recent years around the state.

Boord said 19 popular aquarium species were found in Hawaiʻi waters over the last handful of years, which is more than in years prior.

“For the marine environment in particular, we are seeing an uptick in the number of non-native species that were either released — somebody wanting to let their Nemo live — and others that are purposefully outplanting,” Martin of the Coordinating Group on Alien Pest Species said.

The aquarium releases suspected in the octocoral introduction at Pearl Harbor also introduced five other popular aquarium species to the area, including another octocoral species.

While that octocoral hasn’t spread much, it could if the dominant species were suppressed.

Another species of concern is what DAR called a “hitchhiking” species of anemone, or Anemonia manjano, in Kāneʻohe Bay. A few colonies of the non-native anemone were removed in 2020, but have since been found growing on top of native corals.

Martin warns that there could be even more invasive species in Hawaiʻi.

“The DAR team has gone out at least five times (this year), and that is quite an uptick. And they’re not everywhere. They’re not seeing everything. So, we think it’s the tip of the iceberg,” she said.