LIHU‘E — Hawai‘i’s reefs can’t get any relief.
A multi-agency working group has discovered a new invasive species off Hawai‘i’s coastline that threatens to upend the island chain’s marine ecosystem by outcompeting and suffocating its coral reefs.
The working group first identified the octocoral Unomia stolonifera in Pearl Harbor, O‘ahu, in April, after the Navy alerted state and federal environmental agencies to the colony in 2021.
Unlike reef-building corals, octocorals don’t form skeletons — a long, energy-intensive process — allowing them to grow much more quickly than their hard-bodied counterparts. Additionally, their softer bodies more easily fragment, allowing them to travel via ocean currents and form new colonies in distant areas, posing the threat of rapid and potentially interisland spread.
“We know Pearl Harbor is an estuary. There’s currents coming out of there,” said Christy Martin, program manager of the Coordinating Group on Alien Pest Species, the organization responsible for the working group. “And we’re getting up on the surf season for South Shore, and that wave action can also promote it to break off and start a new population. So, it’s like an invasive species times three.”
The octocoral species grows on hard surfaces and spreads aggressively, planting itself on rocky shorelines and algal reefs and preventing native corals from establishing colonies there. Even worse, the octocoral can grow colonies on top of living coral, smothering and killing the native reef.
“You collapse the food web in an area when you do that,” Martin said. “All of the things that might be using coral or rocky spaces for shelter or food — all of that gets shrunken down to only those things that can live and comply with the octocoral.”
While the group is not certain how the octocoral arrived in Hawai‘i, the Navy has noted that Unomia is popular with home aquarium hobbyists, and may have been illegally dumped into the area.
Because of this possibility, Christina Coppenrath, marine resources management systems specialist with Naval Facilities Engineering Systems Command, is urging base visitors and residents to educate themselves on how delicate the marine ecosystem can be.
“Aquarium species should never be released into the wild,” she said. “If someone is having issues with managing one or more of the species in their aquarium, or are (transferring) and don’t know what to do with the species in their tank, they should contact local aquarium shops for assistance. No matter what, these species should not be dumped into the ocean.”
The working group is also working with the Department of Defense to create a removal and response plan for the existing Unomia colony in Pearl Harbor.
Interestingly enough, one of the main containment and removal ideas floated comes from Kaua‘i, after invasive snowflake coral colonies found at Port Allen in the early 2000s prompted a new method of coral control.
By wrapping heavy plastic over the invasive species and forming a watertight seal, divers decimated the South Shore snowflake coral colonies by smothering them. Now, researchers believe this same tactic could be used against Unomia on O‘ahu, alongside a series of other removal strategies, before the octocoral spreads any farther.
Still, Martin emphasized that any efforts to eliminate the octocoral from Hawai‘i’s shores would be a time-consuming process.
“Eradication means that you visit that place again and again for years to make sure you’ve got every last one,” she said. “And every time you go back and there’s less, it gets harder and more expensive. This is the beginning of a long road, and we definitely hope to be successful, but it won’t be this year, and it won’t be the next.”
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Jackson Healy, reporter, can be reached at 808-647-4966 or jhealy@thegardenisland.com.
