A team of divers from the state Division of Aquatic Resources today planted five, nursery-grown corals in the waters at Hanauma Bay Nature Preserve as part of a pilot project to restore the reef.
The healthy corals — including three cauliflower corals (Pocillopora meandrina) and two elkhorn corals (Pocillopora eydouxi) — were planted in two shallow pockets on opposite sides of the bay, where researchers hope they will continue to grow and thrive.
Each coral, measuring up to 25 centimeters, was carefully grown at the Hawaii Coral Restoration Nursery at Sand Island, using fragments of coral pieces taken from the leeward side of Oahu.
They had been cared for in special tanks at the nursery for four years, free of microorganisms, and are also the same as species of corals already present in the shallow waters of Hanauma Bay.
“I have very high confidence they’re going to do fine,” said David Gulko, DAR aquatic biologist in charge of the nursery. “We’ll know if the corals are doing well in regards to adapting to the new environment within a week or two. We’ll have a pretty good idea what the impacts are from people within a month or two after the bay reopens.”
The closure of Hanauma Bay since March due to the pandemic has provided the perfect window of opportunity for the small project to take place, advocates said, and supporters are hoping that its success will lead to a larger-scale, long-term restoration project.
No reopening date has yet been set for Hanauma Bay, but the Honolulu City Council on Wednesday passed a bill increasing the parking fees and entrance fees for nonresidents 13 years and older.
Lisa Bishop, president of the Friends of Hanauma Bay, also supported a council-approved resolution seeking to establish a reservation system when it reopens.
After seeing a natural resurgence at the bay over seven months — in water clarity as well as the return of marine life in the inner reef — Bishop is hoping it will be able to continue undisturbed for the rest of the year. When it reopens, she is hoping there will not be the same level of crowds as in past years, which have taken a toll on the bay.
It’s an unprecedented opportunity, she said, for the state to “renew its dedication to Hanauma Bay more than 50 years after its designation as the stateʻs first Marine Life Conservation District by resetting its focus to restoring the Bay for current and future generations.”
Two teams planted the corals, using an environmentally safe adhesive to attach them to rock substrates on opposite sides of the bay. Their locations have been carefully marked so that DAR teams can monitor them.
Since the nursery at Sand Island — which maintains 60 Hawaiian species of coral, 48 of which are considered rare — was established several years ago, it has experienced a 100% success rate with corals transferred into the ocean.
The nursery has developed a special method of growing corals for Hawaii, where micro-fragments of coral are glued to a pyramid-shaped concrete module, then nursed in a special tank optimizing conditions for their growth.
During this time, the fragments — all genetically identical — fuse together to form one colony, and corals that would normally grow at 1 to 2 centimeters a year in the ocean grow at a rate of 8 to 10 centimeters inside specialized tanks.
Nursery-grown corals have also been outplanted off of Sand Island and in the deep waters off of Honolulu airport’s reef runway.
Last summer, a team from DAR outplanted extremely rare and endemic thick finger coral (Porites duerdeni) onto a reef at Kaneohe Bay after it was believed to have been wiped out during major bleaching events several year ago.
This is, however, a first for Hanauma Bay, and the first time corals have been outplanted in areas that will potentially be exposed to a lot of human activity.
Gulko noted that corals at Hanauma Bay have decayed over time, partly due to heavy use by people, and partly due to external factors that negatively impacted coral colonies across the state.
Hanauma Bay itself is already a large, natural nursery for numerous species, and he hopes this project opens the door to more active maintenance and restoration of the corals there on a larger scale.
“Hanauma Bay itself serves like a giant nursery,” he said. “We just need to take care of it, and if we take care of it, it will help take care of us. It serves as a safe place for a wide variety of fish, invertebrates, and corals to reproduce. As their progeny gets large and leaves the bay, that’s what repopulates the islands, and perhaps other islands.”