Researchers return from expedition to Papahanaumokuakea with a sense of hope

Scientists that recently returned to Oahu from a 20-day research expedition to Papahanaumokuakea Marine National Monument now have some valuable images and data — and a new sense of hope.

The group of scientists headed out on a rare trip from Aug. 1 to 20 aboard the charter vessel Imua for the second half of a two-part summer research project led by the National Oceanic and Atmospheric Administration’s Office of National Marine Sanctuaries. This trip followed another one in July.

It was the first time a team was able to return to the French Frigate Shoals, or Lalo, to observe what has happened since researchers in 2019 discovered the devastating impacts on reefs due to Hurricane Walaka the prior year.

That year, researchers were shocked to discover Rapture Reef, previously one of the most beautiful, diverse reefs in the isles, turned into a wasteland of coral rubble, with no signs of fish or life, by the Category 3 hurricane that passed through in October 2018.

What they found two years later were exciting, promising signs of nature’s resilience.

“Researchers haven’t been able to get back up there until now because of COVID restrictions and limited ship time,” said chief scientist Jason Leonard. “So they were quite amazed an area totally devastated was making a slow recovery. “

Not only were there there signs of “recruitment,” or reproduction and re-establishment of different species of coral, but juvenile and adult reef fish that had returned to the area.

Scientists found an abundance of herbivorous fishes such as manini and kole at work, grazing on algae, which keeps dead coral surfaces clean and allows juvenile corals to take hold and grow.

“Observations showed positive signs of the overall health of the reefs and that it is slowly making a comeback,” said NOAA in a news release.

At Lisianski island, they found previously damaged reefs that had undergone severe coral bleaching in 2015, now in recovery, with the presence of some young corals.

In addition, scientists found many of the very large, and therefore very old, coral heads in sheltered parts of the lagoon that survived the hurricane were still in excellent shape.

They documented one that was six to seven feet in diameter, and estimated to be more than 200 years old at French Frigate Shoals.

“The health of these old corals is critically important to biodiversity and resilience,” said Keolohilani Lopes, field logistics technician with Papahanaumokuakea, in the news release. “Like old growth forests, these old corals offer long-term habitat stability, and will serve as the brood stock to help to repopulate more heavily damaged areas of the atoll.”

Scientists were also able to conduct follow-up surveys of a shipwreck site possibly dating from the 1800s discovered earlier this summer by crew from the Polynesian Voyaging Society during a survey aboard the Hokule‘a and Hikianalia.

They were able to use advanced cameras and computer programs to digitally reconstruct the site in the area, now nicknamed “Hikianalia Reef,” which they will be able to send to maritime archaeologists to possibly identify the ship.

Scientists took 3-D models of the corals that will help them track their recovery, and to share with other researchers around the world.

They also collected limu samples from each atoll, including some species at Midway that may be new to science on this expedition.

The first mission in July focused on collecting data on a nuisance seaweed, Chondria tumulosa, first documented in 2019 at Pearl and Hermes Atoll. The amount of algae, so far, does not appear to have diminished since then, according to researchers, but fortunately, was not observed elsewhere.

During this expedition, scientists visited the French Frigate Shoals (Lalo), Laysan Island (Kamole), Lisianski Island (Kapou), Kure Atoll (Holaniku), and Midway (Kuaihelani).

Papahanaumokuakea, a 1,350-mile stretch of coral isles, seamounts and shoals northwest of the main Hawaiian isle chain, is home to a diverse array of coral, fish, birds and marine mammals unique to Hawaii, including the endangered Hawaiian monk seal, threatened green sea turtle and 22 species of seabirds, including the Laysan albatross.