Hawai‘i Coral Restoration Nursery

Hawai‘i Coral Restoration Nursery


The Hawaiʻi Coral Restoration Nursery (HCRN) is a biosecure facility located at DAR’s Ānuenue Fisheries Research Center (AFRC) on Sand Island, O‘ahu, and is part of an innovative State of Hawaiʻi driven approach towards mitigating both planned (coastal development and dredging activities) and unplanned (vessel groundings and pollution spills) impact events on Hawaiian coral reefs. The HCRN uses small coral colonies to rapidly grow large colonies at a land-based coral nursery which are then outplanted to damaged and degraded reef areas. More information about the HCRN’s fast-growth process, including sourcing corals, grow-out, and outplanting can be found in the links below. 

To protect the biodiversity of Hawaiian corals from the threat of extinction, the HCRN also houses part of the Rare Hawaiian Coral Ark, a multi-agency effort started at the HCRN in 2015, which preserves a live repository of rare, uncommon, and endemic Hawaiian coral species. In the event that a rare species of Hawaiian coral goes extinct in the wild, the HCRN has the ability to grow representatives of that species held in the Ark and reintroduce them back into their native habitat, restoring the coral population and staving off extinction. More information about the HCRN’s Rare Hawaiian Coral Ark and existing project to prevent the localized extinction of  an extremely rare species of Hawaiian coral can be found in the link below. 

Coral restoration in Hawaiʻi presents several unique challenges. Due to Hawaiʻi’s geographic isolation, it has one of the highest rates of endemism of any ecosystem worldwide; this includes both corals and coral reef-associated organisms, such as fish, invertebrates, and limu (algae). This means that much of the incredible marine life can be found nowhere else in the world, giving those agencies tasked with protecting that marine life a huge responsibility to act in the best interest of the environment. Additionally, compared to many other reef systems in the world, Hawaiʻi has some of the slowest growing corals, averaging 1-2 cm per year, compared to 10-20 cm per year in the Caribbean. Despite these challenges, coral restoration is incredibly important, since bleaching events, vessel groundings, coastal development, pollution, and climate change all pose serious threats to the coral reef community. 

Because coral reefs contain so many unique and geographically restricted organisms, coral restoration demands a high level of knowledge about coral reef ecology and professional coral husbandry. For these reasons, and in compliance with laws governing Hawaiian corals as a natural resource, the HCRN             adheres to protocols it has developed through years of experience studying, growing, and restoring Hawaiian reefs. The HCRN focuses on growing large corals, between 40-100 cm, and has an outplant survival rate of over 95%. Larger coral colonies provide far more ecological services and functions on a reef than small coral colonies, such as:

  • More habitat for fish and invertebrates
  • Greater reduction in wave energy
  • Higher rates of reproduction
  • Higher chance they will be able to withstand stress events, such as increasing water temperatures or predation
Coral Restoration

Nursery Process

Collecting CoralsQuarantineFast-Growing CoralsAcclimating CoralsOutplanting CoralsMonitoring


To minimize the impact to natural reefs, the HCRN prioritizes collecting corals from harbors since these colonies contribute little to coastal protection, juvenile fish habitat, sand production, and tourism attraction,  and provide fewer ecological services than corals found on the reef and therefore have a lower ecological value. By collecting corals from areas of low ecological value, quickly growing them to a much larger size, and placing them out on a degraded reef site, the HCRN is able to vastly increase the ecological value those corals provide. Additionally, corals sourced from harbors may be more resilient to expected changes on our reefs over the coming decades, as they have been exposed to high levels of disturbance and temperature change over their lifetime.

Collecting corals from harbors doesn’t come without risks; due to the polluted nature of harbors along with the frequent boat traffic, collecting corals from these areas increases the chances that these corals may contain heavy metals deep within their skeletons, harbor-associated diseases, or aquatic invasive species (AIS). To mitigate these risks, the HCRN follows strict quarantine and health assessment procedures for all corals entering and exiting the nursery.

Coral colonies collected for module production must meet the following requirements:

  • Must be a native Hawaiian coral species
  • Healthy tissue coloration and polyp extension (varies by species)
  • Absence of bleaching
  • Absence of visible tissue recession or recent death
  • Absence of excessive algal growth
  • Absence of visible disease
  • Minimal or absence of visible AIS 
  • Minimal or absence of visible micropredators visible on colony
  • Large enough size to produce a coral module

Corals that meet these requirements are carefully dislodged from the substrate by HCRN staff using various tools. The process is photographed and cataloged in the HCRN database to maintain a chain-of-custody for every coral collected for the HCRN.

While the HCRN prioritizes collecting corals from harbors, corals will occasionally need to be collected from natural reef sites, particularly for emergency restoration. When collecting from a natural reef, the HCRN collects enough source coral material to produce two modules; one of which will be used for the restoration project, while the other will be returned to the collection site to replace the ecological services the collected coral previously provided, ensuring there is no loss of ecological services due to the collection of coral for restoration purposes.


Immediately after collection, HCRN staff place coral colonies in a designated quarantine area at the HCRN to closely monitor coral health. While in quarantine, HCRN staff check corals daily for disease, AIS, micropredators, and other indicators of poor coral health. Once those corals have been quarantined for 30 days with no health issues, the corals are moved out of the quarantine area. If, at any point, a health issue is observed on a coral in quarantine, the 30-day time period is restarted. This process allows for acclimation to the nursery setting and reduces the risk of disease, AIS, or micropredators within the nursery itself.


When corals are subjugated to stressful events, they are more likely to contract infections or present signs of disease. The process of collection and transport from the field into the nursery is a stressful process and to minimize the stress during these events, the HCRN uses a variety of coral-safe treatments to boost coral health and combat commonly found infections.

Aquatic Invasive Species (AIS)

Due to the isolated location of Hawaiʻi, AIS can pose a serious threat to ecosystems, which are species that are introduced into an environment that outcompete native species, leading to a decline in overall species diversity and ecosystem function. In the quarantine process, any AIS found are removed and reported to the DAR Aquatic Invasive Species team.


There are many animals that eat coral in the Hawaiian coral reef ecosystem. Most commonly found are different species of nudibranchs which eat corals in the Genus Porites, the Montipora-eating flatworm, and corallivorous snails that prey on a variety of coral species.

To get rid of micropredators, HCRN staff conduct daily health assessment checks, including manual removal of these organisms and their progeny. Once the coral has been free of disease, AIS, and micropredators for at least 30 days, it can then undergo the fast-growth process. 



It is important to realize that a coral colony is made up of thousands of individual small animals called coral polyps. Coral polyps can divide through asexual reproduction to produce coral polyps that are genetic clones of itself. When a piece of coral is cut or broken in half, the row of polyps along the freshly-exposed edges begin to grow a new row of coral polyps, which then begin to grow another new row of coral polyps, and by taking advantage of this method of asexual reproduction and outward growth, the HCRN can grow large corals much faster through a process called microfragmentation.

To expedite growth rates, HCRN staff use a specially-designed diamond blade band saw to cut corals into 1 cm x 1 cm square pieces (microfragments), creating more edges for new tissue growth and increasing the surface area to volume ratio. If a 10 cm x 1 cm coral is cut into 100 microfragments, each 1 cm x 1 cm, the coral now has a total perimeter of 400 cm for new tissue growth to occur. After the coral is microfragmented, coral-safe superglue is used to attach fragments onto cured concrete modules made at the nursery, and placed in a specialized aquarium to complete the fast-growth process. Since microfragments are from the same source material (ie the same genotype), when they grow across the concrete module and meet up with their neighboring tissue they fuse to form one large colony. 

The concrete modules used in the fast-growth process are extremely important in contributing to the coral’s increased size. Corals pull minerals out of their surrounding environment that are essential to produce more skeleton and grow to a larger size. Using these concrete modules as a base, fragments  have a temporary skeleton they can grow onto, enabling colonies to achieve a larger size in a shorter amount of time at the HCRN. The entire process is photodocumented and entered into the HCRN database to maintain a chain-of-custody for every coral module grown at the HCRN


Once in the grow-out tanks, all aspects of the environment are controlled to create optimal growth conditions. Water temperature and flow, salinity, essential minerals, light, and coral food are a few things the HCRN can modify to aid coral growth. The HCRN’s professional team of aquarists check on the health of the corals to ensure tank conditions remain optimal  and take quick action if issues arise. 

The coral microfragments grow on these concrete modules until all coral tissue fuses with each other, forming a large single colony again. After the entire module is fused and 100% covered with live coral tissue, the fast-grown coral module is moved into an acclimationtank in preparation for outplanting.


Once the concrete module is completely covered in coral tissue, it is almost ready to be outplanted onto a natural reef. The fast-growth environment at the HCRN is very different from the natural reef environment, so colonies are acclimated to the specific conditions found at the target restoration site. Coral outplants are re-introduced to natural sunlight, photoperiod, water quality parameters, and restoration-site temperatures in large acclimation tanks at the nursery. After a period of 30 days in the acclimation tank, the coral colonies are ready for life in the ocean. The entire process is photodocumented and entered into the HCRN database to maintain a chain-of-custody for every coral module grown at the HCRN.




During the outplanting phase, HCRN staff secure coral modules onto the reef in target restoration areas. A baseline assessment is completed at the outplant site before outplanting modules, which provides information necessary to determine whether the target site is appropriate for coral restoration, including which coral species should be outplanted. 

During the baseline assessment, natural corals growing adjacent to the outplanting site are selected as reference control corals. These control corals are used to compare coral health and growth between areas containing naturally occurring coral colonies and outplanted modules to analyze long-term restoration outcomes. Over time, the outplanted coral will begin to blend into the natural environment, both in terms of color as well as profile appearance. 

To prepare the site to receive a new coral, HCRN staff clear algae and sediment off the substrate the coral will be attached to. HCRN divers attach the coral to the reef using a coral-safe marine epoxy placed on the underside of the concrete module. Once cemented to the reef, epoxy is added around the base of the module for added support and to provide a surface for the coral to grow as it starts to spread onto the surrounding reef. This process typically occurs during fall and winter to allow the outplanted coral to acclimate to life in the ocean before the warm waters of summer come. During summer, ocean temperatures in Oahu typically rise over 80°F, which could induce bleaching on a freshly outplanted coral that has not yet fully acclimated to its new environment. The entire outplanting process is photodocumented and entered into the HCRN database to maintain a chain-of-custody for every coral outplanted by the HCRN.


Outplanting is a stressful experience for the coral module due to handling and reintroduction into the natural environment.The HCRN routinely monitors outplanted coral colonies to ensure optimal health, survival, and growth. Outplants are monitored for five years, very frequently in the first three months after the outplanting event, and then gradually less frequently as the coral becomes a permanent part of the ecosystem at the outplant site.


HCRN staff look for these key indicators of coral health when monitoring corals:

  1.   Presence and degree of outplant tissue paling or bleaching
  2.   Presence and degree of outplant tissue death 
  3.   Size and growth of the outplant, including new coral growth
  4.   Presence of any known coral disease
  5.   Indication or evidence of corallivores present
  6.   Presence of aquatic invasive species
  7.   Presence of competitors directly affecting coral health and growth
  8.   Impacts of sedimentation
  9.   Obvious breakage of coral colony or outplant structure

These monitoring sessions are photodocumented and entered into the HCRN database to maintain a chain-of-custody for every coral outplanted by the HCRN.


Hawaiian Coral Ark

The Rare Hawaiian Coral Ark is a collection of living coral colonies that represent a mixture of rare, uncommon, and endemic Hawaiian coral species. Coral species naturally exist at differing levels of rarity, and the rarer species are more vulnerable to potential impacts to their populations, which may result in extinction. Approximately 25% of the coral species in Hawaiʻi are endemic, meaning they only exist within the Hawaiian Islands. With no replacement pool outside of Hawaiʻi, it is imperative that a system is set up to protect these endemic species, some of which are restricted to a single bay or a single reef throughout the Hawaiian Islands. A wide range of endemic fish and invertebrates have coevolved with Hawaiian endemic and rare corals and have come to rely on the presence of these corals, so an event that causes the extinction of the coral may have cascading effects. The Hawaiʻi Coral Restoration Nursery makes use of its biosecure facility to house a rare Hawaiian coral species ark project. This project is designed to maintain living specimens of native and endemic coral species as insurance against catastrophic events such as wide-scale bleaching which could threaten endemic species as a whole or extirpate rare native coral species from affected islands. The HCRN is regularly collecting additional species and actively works in concert with the Maui Ocean Center to maintain and expand this Ark.

The importance of the Rare Hawaiian Coral Ark has recently been demonstrated with the restoration of a rare endemic Hawaiian species on the island of O‘ahu. In anticipation of a 2015 summer bleaching event, the HCRN collected three small pieces of Knobby Finger Coral (Porites duerdeni), an endemic species that has only been found in a single location within Kāneʻohe Bay on O‘ahu. Unusually high water temperatures during the summer of 2015 caused mass coral bleaching and mortality across the stateand remaining living colonies of P. duerdeni could not be found in the Bay; due to the proactive response by the HCRN in anticipation of the warm water event, the only known living specimens were located in the Coral Ark. When it was determined that this species could be locally extirpated or possibly extinct in the wild, the Rare Hawaiian Coral Ark staff carefully microfragmented two of the three pieces of coral that had been previously collected, quickly grew them on small modules, and in early 2019, these modules were outplanted back into their native location in Kāneʻohe Bay. To our knowledge, this was the first reintroduction of a possibly extirpated coral species into its native habitat. Three years later, despite a warm summer in 2019, the outplants are healthy and are continuing to grow. 

In 2022, three modules of another rare endemic coral, Purple Rice Coral (Montipora dilatata) were also outplanted into Kāneʻohe Bay on O‘ahu.



Corals in the Ark


Acropora sp., Anacropora sp., Montipora dilatata*, Montipora flabellata*, Montipora patula*, Montipora studeri


Gardineroseris planulata, Leptoseris foliosa, Leptoseris hawaiiensis, Leptoseris incrustans, Leptoseris mycetoseroides, Leptoseris papyracea, Leptoseris scabra, Leptoseris tubulifera*, Pavona maldivensis


Cladopsammia eguchii, Tubastraea coccinea, Tubastraea diaphana, Rhizopsammia verrilli


Cyphastrea agassizi, Cyphastrea ocellina, Leptastrea bewickensis, Leptastrea transversa, Leptastrea pruinosa


Cycloseris sp. (red)*, Cycloseris vaughani, Diaseris fragilis, Diaseris distorta, Fungia (Lobactis) granulosa


Pocillopora ligulata*, Pocillopora molokensis*


Porites cf. annae, Porites compressa*, Porites duerdeni*, Porites evermanni*, Porites hawaiiensis*, Porites cf. lichen, Porites monticulosa, Porites rus, Porites solida


Coscinaraea wellsi, Psammocora explanulata, Psammocora profundacella, Psammocora nierstraszi, Psammocora stellata, Psammocora verrilli*

Soft Corals & other:

Sarcothelia edmondsoni*, Sinularia molokensis*, Clavularia sp., Heteractis malu

*Asterisks denote endemic species.

HCRN Milestones

2017: First facility in the world to grow 42 cm massive corals in less than a year.

2018: First dedicated facility to maintain a living rare coral ark consisting of over 50 species.

2019: Only facility in the United States with a consistent year-round supply of viable coral larvae which can be used to facilitate restoration activities.

2019: First to reintroduce a rare, endemic, extirpated coral species back into the wild.

2020: First facility anywhere in the world to grow and outplant a 1-meter massive coral in under a year. A 1-meter coral colony in Hawaii takes 100-150 years to grow naturally.

2020: First outplant of coral modules in Hanauma Bay’s heavily-used inner reef area.

2021: First facility to develop a fast-growth technique for large, upright, branching corals and successfully outplanted a tall branching coral.

2022: First outplanting of nursery-grown, rare endemic Purple Rice Coral (Montipora dilatata) large colonies back into the wild.

Voice of the Sea

Voice of the Sea Season 7 Episode 2: Coral Restoration Nursery

Voice of the Sea is a Hawai‘i Sea Grant program that highlights research, science, and cultural practices throughout Hawai‘i and the Pacific. In this Episode, watch Coral Nursery staff explain the importance of conducting coral restoration in Hawai‘i.


Frequently Asked Questions

What makes Hawaiian corals unique?

Hawaiian corals are unique for a number of reasons, and these impart special needs for maintenance and growth in a restoration setting. The most consequential reasons are generally slow growth rates, low levels of biodiversity, a unique dominant growth form, and the highest level of endemism found in a reef ecosystem on the planet.

Hawaiian corals grow incredibly slowly in the wild at an average growth rate of 1-2 cm per year. For comparison, Acropora cervicornis, a fast-growing Caribbean branching coral and likely the most commonly used species in coral restoration in the Atlantic, grows upwards of 10 cm per year. On the Great Barrier Reef, where coral restoration is being closely studied, corals can commonly grow upwards of 20 cm per year. Due to the slow growth rate in Hawaiʻi, nursery staff must be innovative when coming up with ways to quickly grow Hawaiian corals. This also emphasizes the importance of coral restoration, since natural recovery from impact events can take an incredibly long time. 

The biodiversity on Hawaiian reefs is low when compared to other large reef ecosystems. There are only approximately 60 species of Hawaiian corals in the main Hawaiian Islands, and these occur at differing levels of rarity. For this reason, the nursery focuses efforts on maintaining these levels of diversity when restoring an impact site.

The most common Hawaiian coral growth forms are massive, plating, or small branching colonies. Other reefs in the world are dominated by branching corals. To preserve the ecosystem functions of large bouldering or plating coral, the HCRN uses specially designed modules to mimic natural coral structures while minimizing potential damage from waves and sediment.

Lastly, Hawaiian coral reef systems sustain high rates of endemism, meaning many coral species found in the Hawaiian Islands are found nowhere else in the world. Approximately 25% of coral species found in the Hawaiian Islands are only found here, emphasizing the need to protect these species. As there is no replacement pool for these species, the State of Hawaiʻi must be extremely cautious in their management decisions regarding endemic Hawaiian corals. 

Why does the State of Hawaiʻi need a coral nursery?

Despite corals being fully protected by law in the State of Hawaiʻi, there was little mitigation conducted for direct impacts to the State’s corals prior to the HCRN. Due to multiple human impact events causing significant damage to coral reefs, such as the M/V Cape Flattery grounding in 2005 and the USS Port Royal grounding in 2009, the Division of Aquatic Resources created the HCRN as a method to mitigate these damage events.

Why is the HCRN a land-based nursery?

Elsewhere in the world, most coral nurseries are field-based (in-situ), meaning they are located directly in the ocean. In-situ nurseries require less maintenance and infrastructure, and therefore costs far less to run. Most of these nurseries incorporate a fishing line technique where corals are suspended from a structure to hang them in the water. These nurseries often excel at naturally fast-growing species of branching corals such as Acropora, which is not a component of major reefs in the main Hawaiian Islands. Importantly, this method can only be used in calm water locations. Given the slow natural growth rates of Hawaiian corals as well as the extremely high wave energy that Hawaiian reefs encounter, field-based nurseries would not result in large corals being produced within short time frames. Because of these considerations, the HCRN is a land-based (ex-situ) nursery, which means that corals are grown in tanks on land. This gives us the ability to use our fast-growth protocol to quickly grow large adult coral colonies for restoration purposes within a year. At the HCRN, natural conditions are replicated, such as the high wave energy corals experience on the reef, allowing colonies to survive far better when they are outplanted onto the reef.  

Want to provide feedback?

Fill out this Google Form to help us improve our website.



Meet the Team

We are a small team consisting of specialists and technicians, all with specialized and diverse backgrounds that contribute to restoring Hawaii’s coral reefs.

Christina Jayne, Coral Nursery Curator

Christina Jayne has worked professionally with corals since 2010 and has been with the Nursery since 2018 after earning her B.S. and M.S. in Marine Biology from Scripps Institution of Oceanography at UC San Diego. As the Nursery’s Curator, she oversees coral husbandry operations, restoration projects, and husbandry staff.








Norton Chan, Senior Coral Specialist

A graduate of the University of Hawaii at Manoa, Norton Chan has been a professional Aquarist for over 20 years working with various fishes, invertebrates, and corals from Hawaii and the Indo-Pacific previously at the Waikiki Aquarium.  Currently for the Hawaii Division of Aquatic Resource’s Coral Nursery, he has been a Senior Coral Specialist since 2015.






Taylor Engle, Coral Specialist

Taylor Engle has been with the Hawaii Coral Restoration Nursery since 2019. As a Coral Restoration Specialist, he oversees husbandry in Frag Room 1 and water quality analysis throughout the facility.








Honor Weber, Coral Specialist

Honor Weber graduated from University of California, Santa Cruz with a B.S. in Marine Biology and has worked in wetlabs and public aquariums such as Monterey Bay Aquarium and Waikiki Aquarium before starting at the HCRN as a Technician in 2019, and now Specialist since 2021. Honor focuses on coral husbandry, planula production and settlement, concrete fabrication as well as working with the entire team on fieldwork and managing the volunteer program. 







Angelica Demers, Coral Technician

Angelica Demers, a self-proclaimed fish nerd, earned her B.S. in Coastal and Ocean Resource Management from the University of Texas A&M in Galveston (Go Sea Aggies!). She has been working with fish and corals for over ten years, and was thrilled to join the team at HCRN in 2021 as a coral restoration technician. Her duties include accessing coral health and disease treatment in the nursery quarantine area as well as assisting with coral micro-fragmentation and coral module grow-out. 







Samara Neufeld, Coral Technician

Samara Neufeld has earned a B.S. in Marine Biology with a minor in Sustainability from Florida Institute of Technology, and an M.P.S. in Marine Conservation from University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Science. Joining the nursery in 2021 as a Restoration Technician, she has focused primarily on the husbandry of fast-growth coral modules and field work operations. 







Morgan Short, Coral Technician

Morgan Short joined the nursery in 2022 as a Coral Restoration Technician and is primarily responsible for overseeing coral quarantine operations and assisting with the Rare Hawaiian Coral Ark. Prior to her position at HCRN, she managed husbandry at a coral nursery at Nova Southeastern University while obtaining her M.S. in Marine Science and was an Adjunct Professor for Goshen College’s Marine Biology program.