Reef Coral Arks Projects

Navy Arks in Puerto Rico

Dr. Jessica Carilli, a Scientist with the Naval Information Warfare Center Pacific in San Diego, connected with Forest after realizing that the Arks might be of interest to the Department of Defense (DoD). Submerged lands under DoD management in tropical marine zones—offshore islands such as Guam, Hawaii, and Puerto Rico—harbor rich coral reef communities. Because coral reefs are protected under US law, the DoD is sometimes required to mitigate for coral damage resulting from activities such as constructing and managing underwater structures like wharves and piers.

After recruiting Forest, Aaron, Jason, and Bart as team members, Jessica and the team secured funding from the DoD (SERDP/ESTCP) for a 4-year project demonstrating Coral Reef Arks in Vieques, Puerto Rico. The Former Vieques Naval Training Range (VNTR), used for almost 60 years as a site for munitions testing, is undergoing an extensive cleanup of old ordinance, both on land and in the surrounding sea. Before munitions are removed, the corals growing on them have to be detached and moved to new locations suitable for their survival. Coral translocation efforts like this are not always very successful, particularly if there are not suitable locations onto which to move the corals. The team hopes that Coral Reef Arks will provide ideal conditions for these translocated corals to improve survival.

Coral Reef Arks Image 1
Coral Reef Arks Image 2
Photos by: Baer

The team is testing whether Coral Reef Arks surpass traditional coral mitigation approaches in two ways:

  1. Arks, a portable, depth-adjustable structure, provide improved physical seawater conditions (ex. enhanced light and flow, reduced sedimentation) for translocated corals and
  2. Arks are not only homes for corals, but also house a significant fraction of the diverse biological components that comprise reef ecosystems and are essential to the health and survival of corals.

Over the past year, Jessica and the Coral Arks team have made significant progress towards the Vieques Arks deployment. In February 2020, Jessica and Jason traveled to Vieques to build ARMS that will be used to collect and move coral reef biodiversity from the seafloor onto Arks. Working closely with the Navy and contract scientific divers supporting the underwater munitions removal activities at Vieques, sites for the deployment of Coral Arks were selected, and hydrodynamic models were developed to determine the strength of the forces that Arks might be subjected to in ambient and extreme current scenarios (e.g., due to hurricanes). The results from these models have helped the team design Arks structures, as well as anchor systems, that can withstand the relentless push-and-pull of the ocean.

The team also built and tested a Coral Ark prototype in San Diego Bay, designed by local marine engineer and team member Dr. Bart Chadwick. This testing allowed the team to gather data on how the structures influence, and are influenced by, the surrounding hydrodynamic environment. The tests focused on determining how currents and flow regimes change as they move into and through the Arks, as this could greatly impact the biology growing in and on the structure. By towing the Ark behind a boat at increasing speeds, the team was able to simulate the forces the Ark will experience in higher current scenarios, allowing them to better compensate for these forces in the design of the final Arks structures. Finally, building and testing the prototype structure in San Diego offered the Coral Arks team valuable perspective on the challenges of deploying these large structures in the ocean, providing the hands-on experience needed to ensure the deployment in Vieques goes smoothly and efficiently.

Coral Reef Arks Image 1
Coral Reef Arks Image 1
Coral Reef Arks Image 1
Coral Reef Arks Image 1
Coral Reef Arks Image 1
Coral Reef Arks Image 1
Photos by: Jessica Carilli

The US Navy’s Vieques Restoration Program is focused on removing munitions that were used around the island during past training and testing activities. Many of these munitions have associated corals that must be moved to ensure coral survival. Coral Arks provide an excellent strategy for coral mitigation.

The following images show Coral Arks structure (onshore), the offshore Ark deployment in Vieques, Puerto Rico, and a portion of the field team after the successful field deployment effort. Photo credits: Jason Baer, Anneke van der Geer, Aaron Hartmann, and Jenna Aquino.

As of March 2022, two Arks have been deployed in Vieques, PR. These Arks, constructed from fiberglass and stainless steel, are designed to receive limestone plates to which corals are attached. The Arks are anchored to the seafloor by three sand screw anchors and a mooring system designed to withstand the forces from strong storms and currents, based on calculations from robust hydrodynamic models.

Goal: To mitigate damage to corals during Navy munitions clean-up. This will provide opportunities to track coral health and reef community development and resilience following coral transplantation. As for the Curacao site, Arks are monitored for colonization by reef organisms and coral health.

Corals for transplantation to Arks. (Left) Staghorn coral (Acropora cervicornis) growing at NOAA’s Los Palominos nursery offshore Fajardo, Puerto Rico. (Middle) Finger coral (Porites furcata) growing on a sunken barge in Guayama, Puerto Rico. (Right) Prepared coral plates for translocating corals to Arks and control sites.

Photo credits: Jenna Aquino and Jason Baer. 

Ark colonization after 3 months

The top three photos show Arks immediately following deployment in November, while the bottom three show Arks during the February monitoring event, three months later. Both Arks accumulated a significant biological community since deployment. Fortunately, corals seem to be growing productively even despite competition for space with fouling organisms.

Photo credits: Jason Baer. 

Quantifying growth of transplanted corals

The top three photos represent coral plates on Arks, three months after deployment. The bottom three photos show coral plates at control sites, also three months after deployment. Staghorn corals (A. cervicornis) have performed well at both Arks and control sites, while P. porites and S. radians have been less successful at control sites than Arks.

Photo credits: Anneke van der Geer.

Coral growth and survival is higher on the Arks for some coral species relative to the control sites, which may be due in part to improved environmental conditions at the Arks sites.


Arks sites display higher average flow speeds and less fluctuations in dissolved oxygen than control sites, which are both crucial to their success. Arks also display less signs of microbialization than the control sites, with higher abundances of free viruses (which keep bacterial abundances, including potential pathogens, low) and lower bacterial biomass. These factors likely contribute to the enhanced growth and survival of corals on Arks.


Our most recent monitoring event, in May 2022, involved adding not only a new set of coral plates to each site, but also 10 colonized ARMS units to each Ark. These ARMS units have been passively collecting reef biodiversity for the past year on a healthy section of reef, and by moving these to the Arks, we hope to provide even more of the allies (algae grazers, nutrient recyclers) that enable corals to maintain dominance on healthy reefs. These ARMS and coral plates serve as the final addition to the Arks and control sites, and further scientific monitoring events over the next year and a half will answer some of our questions regarding how reefs assemble, and how these assemblies can be engineered in order to restore, reconstruct, and rebuild reefs in trouble.

Jason Baer and Mark Little collect data on Coral Arks
Seeded ARMS installed onto Coral Arks, along with a new set of coral plates