Hawai‘i Coral Restoration Nursery

Hawai‘i Coral Restoration Nursery


The Hawaiʻi Coral Restoration Nursery 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. To do this, the HCRN uses small corals to rapidly grow into large colonies at a land-based coral nursery which are then outplanted to damaged and degraded reef areas. Below, you can see the steps it takes to collect source corals, rapidly grow them to a much larger size, and outplant them onto degraded reef sites. 

 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, 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 quickly grow representatives of that species held in the Ark and outplant them near a site they were once found, restoring the reef with that species and staving off extinction. Below, you can read more about the Rare Hawaiian Coral Ark and how it has already prevented the possible localized extinction of one species of extremely rare Hawaiian coral. 

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 the corals as well as 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 frequent 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 other unique and geographically restricted organisms, such as fish, invertebrates, and algae, coral restoration demands a high level of knowledge of ecological interaction, as well as professional care and treatment for coral. For these reasons, and in compliance with laws governing the use of Hawaiian corals as a natural resource, the Hawaiʻi Coral Restoration Nursery (HCRN) adheres to protocols it has developed over years of experience studying, growing, and restoring Hawaiian reefs. The HCRN focuses on growing large corals, between 40-100 cm, and has one of the highest survival rates of any coral restoration nursery. Large corals provide far more ecological services and functions than small coral colonies, such as:

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

Nursery Process

Collecting CoralsQuarantineFast-Growing CoralsAcclimating CoralsOutplanting CoralsMonitoring

Collecting Corals


To minimize the impact to natural reefs, the HCRN prioritizes collecting corals from harbors, as these corals provide fewer ecological services than corals found on the reef and therefore have a lower ecological value. This is because coral colonies found in harbors contribute little to coastal protection, juvenile fish habitat, sand production, or tourism attraction. 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, we are able to vastly increase the amount of ecological value that coral provides. 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 does have some risks, however. Due to the polluted nature of harbors along with the frequent boat traffic, collecting corals from these areas increases the chances that these corals have heavy metals deep in their skeletons, associated diseases, or aquatic invasive species (AIS). To mitigate these risks, the HCRN follows strict quarantine and health assessment procedures.

With regards to corals collected for module production, (rare coral collections have different considerations and requirements) every collected coral must meet certain requirements:

  • Must be a native Hawaiian coral species
  • Healthy coloration
  • No visible previous death or tissue recession
  • No visible damage or abrasion
  • Minimal or no AIS visible on colony
  • Minimal or no 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, occasionally corals will need to be collected from either the restoration site itself or nearby natural reef sites. In this instance, the HCRN will collect enough coral to produce two modules; one of which will be used for the restoration project, while the other will be returned to the site of collection to replace the coral that was taken. This ensures 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 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.


Just like humans, when corals are subjugated to stressful events, individuals are more likely to contract infections or present with disease. For corals, the process of collection and transport into the nursery is a stressful process. In addition to minimizing coral stress during collection and transport, the HCRN uses a variety of treatments to combat commonly found infections.

Aquatic Invasive Species

Due to its isolated nature, Hawaiʻi is especially sensitive to AIS, 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, also known as corallivores, in the Hawaiian coral reef ecosystem. Most commonly found are different species of nudibranchs which eat Porites corals, 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 creatures 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.


Fast-Growing Corals

After the quarantine process, the corals undergo the HCRN microfragmentation and fast-growth process. When corals grow, they add new tissue onto their edges and expand outwards. For example, a coral on the reef in Hawaiʻi that is 10 cm wide and 10 cm long will be around 11-12 cm wide and 11-12 cm long after one year, because they only have four sides to grow on. To make corals grow faster, HCRN staff use a specially-designed diamond blade band saw to cut corals into 1 cm x 1 cm pieces (microfragments), creating more edges for the coral to add new tissue onto. So that 10 cm wide coral gets cut into 100 microfragments, each 1 cm x 1 cm, and now the coral has 400 cm of edges to add tissue onto. By increasing the amount of edges on which new growth can occur, the HCRN dramatically increases the overall growth rate of its corals. After the coral is microfragmented, it is glued using medical grade, coral-safe superglue onto cured concrete modules made at the nursery, and placed in one of the coral grow-out room specialized aquariums to complete the fast-growth process. 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

The concrete module that the coral is glued onto is extremely important in allowing the coral to grow faster. In the ocean, corals need to pull minerals out of the water in order to produce more skeleton to grow larger. Using these concrete modules, the coral has a temporary skeleton that it can grow onto, which is just another reason that coral will grow faster when at the HCRN. 

It’s important to realize that a coral polyp is an animal, and that a coral colony is made up of many thousands of individual tiny coral polyps. The reason microfragmentation works is because coral polyps can divide asexually and produce coral polyps that are genetic clones of itself. When a piece of coral is cut in half, the row of polyps along the cut 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 process of asexual reproduction, the HCRN can grow large corals much faster than if they were not microfragmented.



Once in the coral grow-out tanks, all aspects of the environment are controlled so that they are ideal for coral growth. Water temperature, salinity, amount and type of food in the water, pH, essential mineral levels, length and spectrum of the light, and water flow are all things the HCRN staff can modify to suit the coral growing in that tank. Every day, professional aquarist staff at the HCRN check on the health of the corals to make sure that they are growing at their best, and take quick action if a coral is looking stressed. 



The coral microfragments grow on these concrete modules until the coral tissue grows far enough to meet the coral tissue of the fragment next to it, and the tissues will fuse with each other, forming a large single colony again. After the entire module is covered with fused coral tissue, the fast-grown coral module is moved into an acclimation tank to prepare for outplanting.





Acclimating Corals

Once the concrete module is completely covered in coral tissue, they are almost ready to be placed into the ocean. The fast-growth environment at the HCRN is very different from the natural reef environment, so to prepare colonies for life on the reef, colonies need to be acclimated to the specific conditions found at the restoration site. In large acclimation tanks at the HCRN, coral outplants are re-introduced to natural sunlight, photoperiod, water quality parameters, wave motion, and restoration-site temperatures. 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.


Outplanting Corals

To restore a degraded area of the reef, the HCRN staff secure the coral modules onto the reef in a process called outplanting. A baseline assessment is completed at the outplant site before outplanting modules, which provides information necessary to determine whether the site meets the needs for coral restoration, and which species of coral should be outplanted. To prepare the site to receive a new coral, HCRN staff clear algae and sediment off the substrate the coral will be attached to. Then, 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. 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, therefore 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 outplanting site.









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

  1.   Presence and degree of outplant tissue paling or bleaching
  2.   Presence and degree of outplant tissue death 
  3.   New coral growth since outplanting
  4.   Presence of any known coral disease
  5.   Presence of corallivores
  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

During the assessment that was completed before the outplanting, natural corals adjacent to the outplanting site were selected to be control reference corals. These natural corals are used to compare coral health between areas containing natural coral growth and outplanted modules during long-term monitoring. Over time, the outplanted coral will begin to look more and more similar to the natural corals, both in terms of color as well as profile appearance. 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 could cause extinction. Approximately 25% of the coral species in Hawaiʻi are endemic, meaning that 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 could have cascading effects. By holding living specimens of these coral species in a biosecure facility under the care of Rare Coral Specialist staff, the Rare Hawaiian Coral Ark provides insurance against catastrophic events and local-scale extinctions. Where appropriate, excess rare coral tissue is microfragmented, fast-grown to produce small coral modules, and outplanted in order to reintroduce that species back into their native habitat to help restore these unique coral populations. 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, 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 Oʻahu. Later in 2015, after unusually high summer water temperatures which caused mass coral bleaching and mortality, no living colonies of P. duerdeni could be found in the Bay; 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 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 Oʻahu.


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 in Hawaiian reefs is low when compared to other large reef ecosystems. There are only around 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.

Most of the common Hawaiian coral species are massive-form corals, growing colonies that look like large lumpy boulders. Other reefs of the world are dominated by branching corals and other growth forms. To preserve the ecosystem functions of massive corals, the HCRN uses specially designed coral modules to mimic natural 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 Islandsare 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, until the HCRN was created, there was little mitigation conducted for direct impacts to the State’s corals. 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 State created the HCRN as a method of mitigating these damages.

Why is the HCRN a land-based nursery?

Elsewhere in the world, most coral nurseries are field-based (in-situ), meaning they are placed directly in the ocean. This type of nursery takes little 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. Often these nurseries 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 rate of Hawaiian coral 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 aquarium tanks on land. This gives us the ability to use our fast-growth protocol to quickly grow large adult colonies of coral for restoration purposes within a year. In our land-based nursery, we are able to mimic the high wave energy corals experience on the reef, and this causes them to form much denser skeletons, allowing them to survive far better when they are outplanted onto the reef. 

Where is the HCRN located?

The Hawaiʻi Coral Restoration Nursery is a biosecure facility located at DAR’s Ānuenue Fisheries Research Center (AFRC) on Sand Island, O‘ahu


Want to know more more about the HCRN?

Fill out this Google Form to help us answer your questions! 



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.