Hybrid Reef Coastal Erosion Project

To test the viability of bio-enhancing materials, proposed for use for coastal protection, we are determining which substrates promote coral recruitment and growth through field and in situ experiments conducted in Kāne‘ohe Bay, Hawai‘i. Recruitment rates and post-settlement survivorship were assessed through field deployment of recruitment tile arrays during the summer spawning season (recruitment rate) and six-month post-spawning (post-settlement survivorship and fouling community assessment) to determine settlement differences between 11 proposed bio-enhancing materials. To test the viability of coral growth on bio-enhancing materials, micro-fragments of two Hawaiian coral species have been transplanted onto each material, and growth will be monitored under in situ conditions at the coral nursery at the Hawai‘i Institute of Marine Biology. A cost-benefit analysis will be conducted to estimate costs and consequences for each material, including carbon footprint, tensile strength, and ecological benefits. Such an approach can maximize the benefit of restoration efforts and shoreline protection. This will inform ecological engineering and guide management strategies for future erosion control of heavily eroded shorelines and serve to reduce the ecological footprint of projects that would otherwise rely on grey infrastructure (i.e., ports, marinas, groins, etc.).

Materials Tested (11 materials, 220 plates)

  • 20 plates from each of the companies: Econcrete, Oceanit, Intellireef, Natrix, and Fortera.
  • Honolulu Construction and Draying (HC&D) provided raw mixes to construct 20 plates each of mid-range strength and carbon cured cement.
  • 20 each of large basalt and limestone pieces were cut into 4×4 squares by a lapidarian.
  • 20 terracotta plates 4×4 were included.
  • Quikcrete was used to cast 20 4×4 plates.

Twenty-two arrays were constructed using PVC and stainless steel fittings for coral recruitment and community settlement experiments. Arrays were deployed in June 2022 during the summer spawning season to assure maximum settlement.

hybrid reef image 1hybrid reef image 2

Images of prepared tiles from proposed materials (n=220) (left) and deployed tiles in the field (n=22) (right).

To determine coral growth, microfragmentation of two Hawaiian species, Porites compressa and P. evermanni were selected from the HIMB coral nursery, cut using a diamond band saw, and secured on the four corners of each of the 88 labeled plates in July 2022. Each fragment was 1×1 cm. Four genotypes of each species were used. Photogrammetry of each plate was conducted as the initial baseline. Reference from labels determined genotype location.

hybrid reef image 3.jpghybrid reef image 4.jpg

Planar and side views of fragment locations on the tile (left) and deployed tiles at HIMB nursery (n=88) (right).

Images are taken and a condition assessment conducted monthly of the 1056 fragments. Acquired images are used to create a 3-Dimensional model using Agisoft Metashape (Version 1.7.2). We are in the process of incorporating acquired 3D models into a digital tracking program (TagLab) to measure each fragment’s top surface area and perimeter. The data will convert into vertical and radial growth, compared by material, to determine the viability of coral growth on each material type.

hybrid reef image 5

Image of the DEM (Dense elevation mesh) model of fragments attached to the tile.

Testing The Proton Flux Hypothesis and the Coral Metabolism Model

The founder of our Coral Reef Ecology Lab, Dr. Paul Jokiel, developed the Proton Flux Hypothesis and the Coral Metabolism Model as a result of the response of coral calcification to climate change impacts. We are currently testing these concepts that may redefine the existing paradigms in this field. The proton flux hypothesis is a transformative new concept that explains the mechanisms responsible for the observed decrease in coral calcification with increasing ocean acidification. Historically, research has focused on the uptake of carbonate/bicarbonate ions as the limiting factors controlling reduced calcification under conditions of ocean acidification. The Proton Flux Hypothesis (Jokiel 2016) focuses on the waste products, mainly hydrogen ions (H+), that are removed from coral tissues. Under ocean acidification, H+ increases when pH decreases. This limits the removal of H+ across this strong concentration gradient resulting in the inability of corals to quickly remove H+. This results in a buildup in coral tissues that impedes calcification.

proton flux image 1

Simplified Two Compartment Proton Flux Model (A.) showing the spatial arrangement of chemical reactions with the resulting fluxes and recycling pathways of protons (B.), oxygen (C.) and carbon (D.) (adjusted from Jokiel et al., 2016).

To understand this relationship of corals to ocean acidification, we must examine coral growth forms and calcification. The Coral Metabolism Model (Jokiel 2011) places the zone of calcification in the outer portions of a colony, where symbionts are not present, regardless of morphology. Thus, this facilitates the removal of metabolic wastes including H+ and maximizes the recycling of oxygen and bicarbonate. The zone of photosynthesis is located in the inner regions of the colony where the symbionts reside providing protection from harmful UV rays while increasing efficiency by scattering light (PAR) to increase absorption. By testing this model, we can better understand growth form diversity and plasticity and the response of coral calcification to ocean acidification.

proton flux image 2

Coral morphology showing areas of rapid calcification (ZC) in relation to areas of photosynthesis (ZP) relative to the boundary layer (BL).  In all morphologies, the ZC is located between the ZP and adjacent to the BL (Jokiel et at., 2011).

This three-year project will provide an essential empirical framework for coral reef responses to realistic present and future climate change projections, which will allow for a true representation of the environmental tolerance of future coral reefs. This research will advance our understanding beyond a correlative framework by re-evaluating existing paradigms concerning coral and coral reef metabolism by providing data that is vital to the understanding of carbonate dynamics and the ecology of present-day reefs and ancient coral reef ecosystems. 

Ocean Cooling Trials to Ameliorate Coral Bleaching

ocean_coolingTo ameliorate the effects of bleaching on coral reefs, we have identified several strategies to test as a proof of concept that if successful can be expanded to protect large areas of reef and serve as refuges that can act as a source of replacement and enhancement. Corals live within 1o-2oC of their thermal tolerances. Four methodologies will be evaluated to determine the efficacy of each in reducing ocean temperatures 1o-2oC to ameliorate coral bleaching during summer maximums.

1) Heat exchange: A closed heat exchange system of deep cold water (4.5oC) in proximity to nearshore reefs will be evaluated. Pipes with cold seawater will provide cooling to evaluate extent and efficacy of reducing temperatures. No direct deep seawater exchange will occur.

2)Evaporative cooling/shading: A bubbling procedure will bubble air from a surface barge with an energy system generated through currents and waves. Size of bubbles are regulated to minimize impact on corals and fishes. Air bubbles will provide an evaporative cooling effect of surface water and a shading influence for corals.

3) Evaporative cooling/shading: Surface misting methodology using ambient surface seawater will be employed and assessed for rates of cooling and water column mixing. This will provide both and evaporative cooling and a shading effect.

4) Artificial upwelling: An open diffusion system will release cold, deep seawater through an irrigation network of pipes. The dispersion of elevated nutrients and lower pH from the deep seawater will be evaluated in the field and in manipulative onshore mesocosm experiments.

All testing will be conducted at the Hawai‘i Ocean Science and Technology Park (HOST) for proximity to cold seawater (Fig. 1). A team of engineers is in place to assist in design and implementation. Automatic sensor and monitoring systems will be deployed. Biological surveys and physical and environmental monitoring will be conducted to identify any shifts. Exposure rates, seawater mixing, intensity, duration, temperatures, pH, and water quality gradients will be closely monitored. To evaluate the spatial scale, these methods will be assessed at 3m and 10m depths. Our team of coral reef ecologists, oceanographers, and engineers provide the proficiency and experience to assess the efficacy of ocean cooling and artificial upwelling as viable solutions to coral bleaching that can be extrapolated to other, larger regions.

The Hawaiian Koʻa (Coral) Card: Coral health and bleaching assessment color reference card for Hawaiian corals.

Koa card Phase 1Phase I- With the projected increase in severity, extent, and frequency of coral bleaching events, the goal of our project was to develop an inexpensive, rapid, and non-invasive coral health card that can be rapidly used by nearly everyone to assess and report on coral bleaching severity. As corals lose their zooxanthellae symbionts or “bleach”, the color of the colony begins to lighten until the tissues are transparent and the skeleton becomes visibly white. An easy and effective field method of determining the severity of bleaching is the comparison of different shades of color over time and/or between sites and coral colonies. There is a pressing need in Hawai‘i for such a tool as more scientists, students, community members, and resource managers become involved in monitoring the changes taking place on our reefs. The tool we developed through quantified field and laboratory research, validation testing, and surveys is unique in its circular design that follow the degradation of color in four major quadrants to represent the colors of 17 major coral species in Hawai‘i.

To accurately quantify the change in color during bleaching, we have conducted controlled temperature induce bleaching assays using six common Hawaiian species with over 600 fragments. All corals were photographed and sub-sampled daily for coral health factors. Photographs were analyzed using an automatic function in Adobe Photoshop™ to generate various color values. These images provide reliable correlations between the photographs and changes in the color of the coral at various stages of bleaching and recovery. Professional underwater photographers were used to assure natural colors and for uniform consistency (Yuko and Keoki Stender). Simultaneously with the photography of the fragments, the photosynthetic efficiency and fluorescence was determined as color loss progressed. Samples were taken to evaluate chlorophyll a and symbiont density to correlate with color factors. As bleaching progresses these factors decline. Over 10,000 photographs were then analyzed to determine hue, saturation, and brightness of each coral fragment. These color factors were then correlated with the health factors at various stages of bleaching. 

Ko'a card

Phase II- We then conducted a field and lab validation and an observer variation trial.

Once we had conducted these lab experiments, it was imperative to validate this dataset. Validations were conducted by repeating the experiment with an independent set of samples to see if the same results are found. We used over 100 fragments this time with similar results.

We then validated the card in the field to determine each color’s abundance and distribution in shallow waters. We found that this set of colors can be used with 17 species of corals and the overwhelming majority of common species in Hawai‘i.

We also looked at the observer variation and solicited feedback. The assessments were made in natural sunlight conditions with corals presented in a black raceway tank. Each observer independently determined the majority color of each coral fragment avoiding tips and cut margins. Observer variation was based on comparing the selected color value by each observer to the color value that was most frequently selected (observer precision). To determine if observer precision is influenced by any particular factor we looked at age, gender, coral familiarity (never snorkel, snorkel, know coral common names, know coral scientific names), highest level of education (high school, bachelors, graduate), and ease of use (easy, medium, difficult). 

No significant correlation was found between any of these factors. Despite non-significant results, 4 out of the 5 males that participated in the Hawaiian Koʻa Card trials scored at or below 50% precision, which is the color the majority of observers selected. Males are known to see color slightly differently than women. The card was also tested under field conditions.

A new biodegradable material was tested to determine if it would compromise the card by fading or scratching. For sun trials, the card was placed on the roof in direct sunlight and weather elements. In saltwater trials, the card was submerged in an open flow saltwater tank. And for abrasion trials, the card was scraped against the sand and dead coral rubble. The only environmental factor that showed a visible difference was abrasion, yet only through vigorous scratching and scraping. Thus, these high-quality, biodegradable cards should hold up well under environmental conditions if stored out of the elements.

Phase III- This phase is an on-going training, education and outreach to reach managers, educators, students, community groups, and individuals. We have conducted training on Kaua‘i, Maui, and O‘ahu and in Kona. We have distributed our first 1,000 Ko‘a cards and accompanying brochures. We include educational materials on bleaching and recommendations for solutions. All training and material have been free of cost thus far due to a generous donation of printed cards from Condit, a custom trade show booth, displays, exhibits company based in Colorado. This tool is currently available at all State Division of Aquatic Resources offices.


The health of numerous coral reefs throughout the state can be evaluated using this tool. Initially, the state of the reefs must be determined before declines can be reversed. This will aid in identification of areas where management efforts should focus.

Widespread use of the coral assessment wheel will help detect areas of refuge that are more resilient to climate change by identifying regions with low occurrence of bleaching.

The Hawaiian Ko‘a card will give individuals and communities a sense of kuleana (responsibility) and mālama (stewardship) for the reefs in their ‘ahupua‘a (land division).

The education provided about bleaching and the ability to directly experience the visual transformation in the corals can be a force for change that can be passed on.

Assessment data can be of service in evaluating the efficacy of management efforts to slow climate impacts.

Observation is critical in determining the condition of reefs. The color gradients on the assessment card will train ocean users to detect slight color differences and relate this to coral health.

Statewide assessment data derived from this project will be incorporated into the ridge to reef database to increase spatial and temporal recognition of changes in the mauka/makai.

Measurable baselines and subsequent declines can be established for reefs statewide.

We can provide habitat protection by community driven management through provision of education and resources

Hawaiian Ko‘a Card

Hawaiian Ko‘a Card Publication

 Determining Sediment Tolerance Thresholds for Hawaiian Corals

Hawaiian coral metabolic tolerance levels to sedimentation have not been previously determined. By resuspending fine clay particles in recirculating respirometry chambers we are defining the tolerance limits for dominant species of corals. Each chamber is equipped with an oxygen probe allowing for continuous monitoring of oxygen production and consumption in coral colonies exposed to sediment stress over time. These controlled experiments are assisting in the understanding of coral community metabolism through measurements of calcification and photosynthesis. Results from this project will help define management strategies for conservation and mitigation.


Coral Acclimatization/Adaptation to Increasing Temperatures

There is sparse research to support or refute whether corals will be able to acclimate to rising ocean temperatures. In 1970, our founder Paul Jokiel and his colleague Steve Coles conducted the first thermal tolerance experiments on Hawaiian corals. They determined that corals will bleach between 1-2 °C of their summer maximum temperatures. These findings formed the basis of subsequent bleaching research and continues to be used in calculations to model predictions for bleaching (eg. NOAA’s CoralWatch). Thermal tolerances have not been reassessed since that time. The first bleaching event did not even occur until 1983 and was not observed in the Hawaiian Islands until 1996. Now almost half a century later we replicated the initial experiments to quantify whether or not acclimatization/adaptation has occurred. This exciting research uses the same seawater system, mesocosms, coral species collected from the same reef flat, and replicates other conditions of the original experiment. Although Dr. Jokiel is no longer with us, we brought in his colleague, Dr. Coles, to conduct the assessments and classifications of the original experiments. 


Hawaiʻi Coral Health Surveys

The Coral Reef Ecology Team is dedicated to ongoing work focusing on anthropogenic impacts on coral reefs. We are currently conducted coral health surveys in Kāneʻohe Bay and Hanauma Bay Nature Preserve to better understand how humans shape coral reefs.

Dr. Rodgers and Justin Han img_1454

Hā‘ena Community-Based Subsistence Fishing Area (2016-2020)

Haena.pngThe Community-Based Subsistence Fishing Area (CBSFA) in waters off Hā‘ena, Kaua‘i is an area of special interest to the State of Hawai‘i. The purpose of this five-year project is to assist the Division of Aquatic Resources (DAR) in evaluating this Hā‘ena CBSFA special management area. Monitoring inside and outside this region will be critical in determining the efficacy of any marine remedial management actions. We are partnering with DOBOR, DAR Maui Monitoring, DAR Oahu Monitoring, DAR Invasive Species and the Kauai Education and Outreach teams to survey 100 random locations annually using the Kauai Assessment Habitat Utilization (KAHU) methodology for fishes, benthic components, and urchins. Sediment grain-sizes and composition will be also determined. Temperature loggers have been deployed at 25 stations throughout the area.

Pila’a, Kaua’i (2016-2020)

Pilaa.pngIn 2001, our lab surveyed the extensive damage to a reef downstream from a large site where illegal grading took place at Pila‘a, Kaua‘i. Our survey results and court testimony assisted in securing the largest unprecedented settlement to the State of Hawai‘i for reef damage. The initial baseline survey will be repeated using the same methods in order to document recovery. We have begun assessments using the Kaua’i Assessment Habitat Utilization (KAHU) methodology for comparability with other sites. We are determining coral recruitment rates using standard recruitment arrays and establishing a long-term monitoring site to document any changes in fish and benthic populations. In collaboration with USGS we will be analyzing the record of coral growth and sedimentation over past centuries through coring large corals. This method identifies annual bands and the sedimentation signature within each band over the length of long cores.

Effectiveness of Coral Relocation as a Mitigation Strategy  2005-Ongoing

Coral relocation field photoCoral reef restoration and management techniques are in ever increasing demand due to the global decline of coral reefs in the last several decades. Coral relocation has been established as an appropriate restoration technique in select cases, particularly where corals are scheduled for destruction. We removed coral from the HIMB navigation channel and relocated it to a similar nearby dredged reef in 2005 for safe vessel navigation. This was a joint project that included Army divers of the 7th Engineering Detachment’s 29th Engineering Battalion, Marine Options Program students, UH undergrads, graduate students, and the Division of Aquatic Resources. This multi-agency project received the UH Team of the Year Award and was advanced to the State Team of the Year competition in 2009. Coral recovery at the donor site and changes in fish populations at the receiving site were tracked periodically over the following decade in 2008, 2012, and 2016. Coral regrowth at the donor site in the navigation channel was rapid until a recent bleaching event in 2014-15 reduced coral cover by more than half. The transplant of mature colonies increased spatial complexity at the nearby receiving site, immediately increasing fish biomass, abundance, and species diversity that was maintained throughout subsequent surveys. Our research indicates that unlike the majority of historical accounts of coral relocation in the Pacific and relocation projects our lab has undertaken (eg. Kawaihae), corals transplanted into wave-protected areas with similar conditions as the original site can suffer low mortality. Data on long-term monitoring of coral transplants in diverse environments is central in developing management and mitigation strategies. We will continue to reassess the long-term changes every five years or whenever events that precipitate change occur.

Statewide Monitoring CRAMP (1998-ongoing)

CRAMP.pngIn 1998 when we developed the Coral Reef Assessment and Monitoring Program (CRAMP) in response to management needs, there was no long-term widespread monitoring program in this state. It was vital to get a baseline of what our reefs looked like, to recognize any changes that may occur, and to identify any impacts that are affecting these reefs. Over 60 sites span the full spectrum of habitats, encompassing the full latitudinal range and include the entire range of protection status from open access sites with no other legal protection except what applies to the entire state to fully protected sites, and a gradient of natural and anthropogenic impacts. This extensive dataset is being used to find trends and patterns on a statewide, island, and site scale and identify forcing functions that drive them. Researchers, managers, and educators are utilizing the data for a wide variety of purposes. We currently partner with the DLNR’s Division of Aquatic Resources to monitor sites and to set up new sites such as the one planned for Pila‘a, on Kaua‘i.

Hanauma Bay Biological Carrying Capacity (2017-2018)

hanuama bay.pngThe Hanauma Bay Nature Preserve (HBNP) project will assess anthropogenic use and global impacts in relation to biological carrying capacity.  The Hanauma Bay biological carrying capacity study is designed to determine the acceptable limits of disturbance to the marine resources of Hanauma Bay. It will do so by (1) reviewing recent and historical data and compiling this data into one annotated bibliography, (2) performing several new observational experiments, and (3) continuing to monitor the long-term sites established in 1999. By monitoring human activity in each area of the bay in harmony with coral skeleton trampling (using dead coral skeletons), coral recruitment, and sediment suspension experiments, we will be able to determine if the current level of human use allows Hanauma Bay to sustain its marine resources.  In addition to new field surveys, by resurveying long-term monitoring sites and documentation of temperatures and currents from year to year, it allows us to determine changes in the biological populations over time and relate these changes to shifts in activities (ex. fish feeding).  By blending historical data with data from past and present observational experiments , we will have a better understanding of the Bay’s current condition and will be able to make informed recommendations toward protecting its marine resources for continued future use.

Effects of Nutrients on Corals

We are evaluating the impacts of increased nutrients on corals in relation to increasing temperatures. Our preliminary results show some mitigating effects of nutrients on growth and bleaching of corals.

Ridge to Reef (Mauka/Makai) Connections (2015-2017)

We are developing protocols that prioritize watersheds and coastal waters for protection and restoration in Hawai‘i. Quantitative watershed and coral reef condition indices are being integrated with a GIS-based, predictive model to produce geographically realistic planning and evaluation tools. We are integrating quantitative model output from terrestrial watershed and coral reef condition indices to evaluate the ecological condition of the “ridge to reef” system. This project provides spatial maps to determine which of the 580 watersheds in the state have the strongest connections to adjacent reefs and would most benefit from watershed restoration efforts. This will help address the scientific needs of the agencies responsible for the management and mitigation of Hawaiian coral reef ecosystems. This project was funded by the Environmental Protection Agency.



Pelekane Bay

Our lab has conducted multiple coral reef studies in Pelekane Bay and the larger Kawaihae area since 1995 to better understand the response of the reef community to cumulative human impacts, effectiveness of management measures, and recovery potential. The most recent studies between 2010 and the present focus on key biological and ecological processes investigating coral settlement, growth, partial-mortality, and community structures in relation to land-based sedimentation and environmental quality. These studies in Pelekane Bay were carried out collaboratively with federal government agencies, and non-governmental organizations, and the community to address the broader issues of land-derived impacts on coral reefs.  Our findings suggest significant impacts of sedimentation on biological and ecological processes of corals and recovery potential.