The project demonstrated how it may be possible to restore larger areas much more quickly than would happen naturally.

In the summer of 2020, a large log scoured a stretch of Hanauma Bay’s brown lobe coral, a boulder-like, reef-building animal that helps protect the shoreline from waves. 

Without human intervention, this kind of destruction could ruin a coral reef. And this wasn’t just any reef — it was Hanauma Bay, a protected nature reserve and one of Hawaii’s most popular tourist destinations.

Three years later, the state Division of Aquatic Resources has completed its restoration project. The Hawaii Coral Restoration Nursery finished outplanting the last of six lab-grown coral modules at the end of the bay in April, demonstrating to aquatic biologists, policymakers and others that such work is possible.

Two DAR SCUBA divers outplant a nursery-grown coral module at a reef restoration site.
Two state Division of Aquatic Resources scuba divers outplant a nursery-grown coral module at a reef restoration site. (Courtesy: DLNR DAR)

“Corals in Hawaii grow so, so slowly that it may take hundreds of years to recover from an event like that,” said Christina Jayne, the HCRN curator. “Almost a quarter of our coral species are found nowhere else in the world, so if something happens to one of those species, there is no replacement.” 

The nonprofit Friends of Hanauma Bay solicited help from HCRN to restore this area of the reef, so that the reef could still provide ecosystem services to the bay: habitat for fish and other marine organisms, for example, and coastal protection.

Established in 2015, HCRN has pioneered a methodology for restoring Hawaiian corals by growing them quickly in a land-based lab, then outplanting them in the wild. 

Divers collect corals that have been damaged by storms. These coral fragments are then quarantined at the Anuenue Fisheries Research Center. 

The Hawaii Coral Restoration Nursery has pioneered a methodology for restoring Hawaiian corals by growing them quickly in a land-based lab, then outplanting them in the wild. (Grace Cajski/Civil Beat/2023)

HCRN staff cut the coral into 1-by-1-centimeter microfragments, and then superglued these fragments onto concrete pyramid modules. The coral fragments grow across their edges and eventually touch their neighboring fragments. 

When all neighbors touch, a large adult colony is formed. The corals are acclimatized to the conditions of the outplanting site, and then placed in the wild. 

This process takes one to two years — less than 1/20th of the time it takes for the same growth in the wild. 

“These large adult corals can instantly contribute to the ecosystem services and functions, being part of the ecosystem of that reef,” said Jayne. 

Before committing to outplanting six coral modules, in 2020 HCRN outplanted a few small coral colonies into different areas of Hanauma Bay. 

Hanauma Bay aerial.
A log damaged some of the coral at Hanauma Bay in the summer of 2020 but the state has since replanted lab-grown corals to help restore the reef. (Cory Lum/Civil Beat/2018)

This pilot project showed the team the potential for survivorship in the inter-reef area, and provided a lower-stakes opportunity to solidify their outplanting methods in this new location. The test corals grew well. 

“They’re still out there, you can go out and swim around them, if you know where to find them — but they look like natural corals now,” said Jayne. 

Since the pilot project was promising, HCRN began growing the six modules to restore the log-damaged brown lobe coral. 

Consistent monitoring of the six modules’ growth and health has revealed that this restoration project has been successful. There have been no signs of predation, the corals are a healthy color, and they have started to grow down onto the natural reef substrate on the rocks. 

“This project is showing: can we do restoration in Hanauma Bay, will it be successful? And the answer is yes,” Jayne said.

The HCRN is continuing to grow corals for active restoration projects that mitigate and restore damaged reefs. (Grace Cajski/Civil Beat/2023)

The HCRN is continuing to grow corals — about 150 modules at a time, all of which are grown with their final destination in mind — for active restoration projects that mitigate and restore damaged reefs. 

HCRN maintains the Rare Hawaiian Coral Ark, a living seedbank for rare, uncommon or endemic coral species in Hawaii. It provided fragments of knobby finger coral that had been extirpated in Kaneohe Bay in 2015.

In the near future, HCRN will undertake coral enhancement projects that are community-minded: the team will outplant corals at recreational dive sites, which will augment the dive sites and teach people about the importance of coral restoration. 

Two tall branching coral module outplants providing habitat for fish.
Two tall branching coral module outplants provide habitat for fish. (Courtesy: DLNR DAR)

HCRN is also expanding its facility to be able to grow more coral modules per year. 

“The ultimate goal is to have corals on the reef that, if you swim over it, you would have no clue that it was grown in a coral nursery, and it just looks like a natural coral reef,” said Jayne. “And that they would contribute to maintaining that reef ecosystem, and reproduce.”

But restoring Hawaii’s damaged coral reefs requires lots of resources, like staff and space and time. 

“We’re one institution, we can only make so many corals a year,” said Jayne. “But our team of less than 10 people can’t restore all of Hawaii’s reefs.”

Luckily, HCRN’s successes have inspired other coral restoration projects. 

The Ocean Science and Technology Park in Kona, Arizona State University is leading the creation of the first land-based coral nursery on Hawaii island. A collaboration with the National Oceanic and Atmospheric Administration and DAR, this program, called ‘Ako’ako’a, hopes to preserve and restore West Hawaii’s coral reefs. 

“The HCRN has contributed to our understanding and preparedness for coral restoration in Hawaii,” said ‘Ako’ako’a Director Greg Asner. “They have also driven a pathway for other organizations, including (the University of Hawaii), ASU and every NGO, to learn from in working on coral restoration across the state.” 

He attributed HCRN’s knowledge and work as a crucial seed for future coral restoration in the state.

Civil Beat’s coverage of climate change is supported by The Healy Foundation, the Environmental Funders Group of the Hawaii Community Foundation, Marisla Fund of the Hawaii Community Foundation and the Frost Family Foundation. 

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