Coral damaged by grounded yacht ready to return to Honolua Bay after recovering in nursery

MĀ‘ALAEA — In a saltwater aquarium at the Maui Ocean Center Marine Institute’s facilities, a cluster of tiny corals are building up their strength for a big journey back home. 

The neatly arranged rows of lobe and cauliflower coral were plucked from Honolua Bay more than a year ago after the grounding of a 94-foot luxury yacht left deep scars on a critical reef that has some of the highest coral coverage on Maui, according to the state Department of Land and Natural Resources.

After being cared for at the Marine Institute’s nursery in Mā‘alaea, most of the broken pieces of coral have recovered enough to be planted back in Honolua Bay, said Dustin Paradis, director of the nonprofit institute. 

“Corals have been declining for a long time and largely due to humans,” Paradis said. “So I think it’s part of our responsibility to try to undo some of the damage that we’ve done. And if there’s a will, there’s a way.” 

The corals’ saga began on Feb. 20, 2023, when the yacht “Nakoa” broke off its moorings in Honolua Bay and drifted onto the rocks at the north end of the bay, just outside of the Honolua-Mokulē‘ia Bay Marine Life Conservation District. It took nearly two weeks and multiple attempts to drag “Nakoa” off the reef, and the yacht eventually sank in about 800 feet of water as a salvage ship towed it away. 

The grounding impacted just over 20,000 square feet of hard bottom nearshore habitat that included turf algae and patchy coral cover, according to the final damage assessment report by the state Division of Aquatic Resources. A total of 119 live coral colonies were heavily damaged and destroyed, including 85 colonies of cauliflower coral, a fast-growing species named for its resemblance to the vegetable, and 34 colonies of lobe coral, one of the four most prominent reef-building species in Hawai‘i.

Biologist Russell Sparks, who led the team assessing the reef for damage, said at the time that even without intervention, it would take the reef two or three years to repopulate back to the way it was.

The state levied a fine of more than $117,000 to the yacht’s owners, but increased the amount to $1.8 million in April after hearing testimony from the community over the cultural and ecological importance of Honolua, a rare publicly owned and undeveloped shoreline that activists fought to protect years ago from a proposed golf course and luxury homes. 

The owners of “Nakoa” are appealing the fine. 

After the yacht was removed and the state assessed the damage, Maui Ocean Center Marine Institute staff and volunteers, and two coral specialists from the Maui Ocean Center collected more than 100 fragments of damaged corals from the bay.

“They’re pretty compromised because they’re broken off the reef,” Paradis said. 

Choosing corals to take back to the nursery for regrowth is a bit like triage as staff figure out which ones have the best chance for survival. Paradis said they try to take corals that have more than 80% live tissue, though every scenario is different. Sometimes freshly disturbed corals, though broken, can be healthier than older corals with more areas of dead tissue. 

The Marine Institute, which is housed beside the Maui Ocean Center aquarium, also specializes in rescuing and treating injured sea turtles. The tanks in the institute’s nursery include coral for educational purposes, samples for research projects like the Restore with Resilience initiative that is studying coral’s thermal tolerance, and damaged coral making a recovery like the pieces salvaged from Honolua Bay. 

After going through quarantine to make sure they were free of disease, the corals were cut into fragments roughly the size of a dollar coin using a diamond-bladed bandsaw. Some were affixed to plugs made of aragonite, which is similar to the coral skeleton of calcium carbonate, while others were placed on terracotta tiles, which were chosen because they are readily available raw materials, Paradis said. 

The corals live in a saltwater tank with water pumped in from Mā‘alaea Bay, surrounded by yellow tang and native Hawaiian collector urchins that keep the coral clean by eating the algae on it. They’re fed a blend of powdered marine plankton and rest under blue and pink fluorescent lights that mimic the wavelengths that the corals would get from sunlight in their natural habitat.   

The coral are ready to return to the wild when they have fully encrusted the base material. Some of the coral on the tiles need more time to grow, but most of the coral on the plugs are “ready to go,” Paradis said.

“That way it’s fully encased by the coral, so when it’s outplanted there’s no foreign material in the ocean,” he explained. “It’s just a standard practice of restoration.” 

Once the Marine Institute gets its special activities permit renewed, the team will survey the dive spot and make a plan for placing the corals back in the bay on a hard, bare surface. Holes will be drilled for the coral on the plugs and the coral on the plates will be attached with a marine-grade epoxy. The team will monitor the coral quarterly, Paradis said. 

The coral will likely be planted around November or December, after the threat of coral bleaching has passed during the warmer months but before the winter swells arrive. 

The yacht in Honolua was one of 12 boat groundings in Maui Nui in 2023 — not including the roughly 80 boats damaged or destroyed in the Lahaina wildfires — compared to just two in 2022, according to the state Division of Boating and Ocean Recreation.

Even with the rise in groundings, Paradis said the team hasn’t been called to help salvage more coral than usual. Some incidents were on sand, including the former Navy torpedo boat “Chaparral” that grounded next to a seawall in North Kīhei in January. 

There’s a silver lining to the salvaged coral from Honolua — Paradis said the team will be planting more colonies than they collected because the salvaged coral was cut into pieces, and these colonies could eventually grow much bigger over time. 

“Lobe coral is one of the reef dominators in Hawai‘i, and they grow very large, extremely large,” Paradis said. “They can be thousands of years old also. So these, though they’re small, over time they will contribute to the reef, and they will build the reef and build habitat for the fish.”