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NOAA awards $2.4M for 'twilight reefs' coral research in American Samoa

Stony coral, Galaxea fascicularis,
Source: NOAA's Office of National Marine Sanctuaries

Pago Pago, AMERICAN SAMOA —  Most ocean enthusiasts are familiar with shallow coral reefs: colorful ecosystems teeming with life that support more species than any other marine environment. But what many people don’t know is that these reefs can extend to depths of over 500 feet. These deeper reefs are known as mesophotic coral ecosystems or “twilight reefs.”

Mesophotic coral ecosystems are not easy to access, and not as well studied as shallow coral reefs. However, NOAA is working with partners to change this. This month, NOAA is announcing $2.4 million in funding for a four-year research project studying mesophotic coral ecosystems in American Samoa, including reefs within the National Marine Sanctuary of American Samoa and the National Park of American Samoa.

The first year of research represents $599,673 of the anticipated $2.4 million four-year project. The competitive research program is called the Deep Coral Reef Ecosystem Studies (Deep-CRES) Program: American Samoa.

It seeks to improve our scientific understanding of mesophotic coral ecosystems, so that resource managers like National Marine Sanctuary of American Samoa can better protect them.

The funding comes from NOAA’s National Centers for Coastal Ocean Science (NCCOS)  Competitive Research Program, in cooperation with the Office of National Marine Sanctuaries and Office of Ocean Exploration and Research.


Mesophotic coral ecosystems are located below conventional scuba diving depths, at about 100 to 500 feet or more. Due to their depth, they remain relatively understudied. They share some coral and fish species with shallow reefs, in addition to other species that are unique to these depths.

These soft corals (Dendronephthya spp.) were photographed at 148 feet in American Samoa.  [photo: Anthony Montgomery, under Creative Commons License]

With the health of shallow coral reef ecosystems in decline, it is important to understand the value and role of mesophotic coral ecosystems in tropical and subtropical waters. These ecosystems serve as essential habitat for economically and ecologically important species to spawn, breed, feed, and grow to adulthood.


To improve knowledge of mesophotic coral ecosystems, this project targets American Samoa, the only U.S. territory in the South Pacific. American Samoa includes five volcanic high islands (Tutuila, Aunu‘u, Ofu, Olosega, and Ta‘u) and two atolls (Rose and Swains). Due to the region’s volcanic and coral topography, nearly 80 percent of potential coral reef habitat in American Samoa is within the depth range of mesophotic coral ecosystems.

Yet it remains relatively unexplored.

Diver Jason Leonard photographs a mesophotic coral ecosystem at 80 meters (262 feet) off Larsen's Bay in National Marine Sanctuary of American Samoa. [photo: R.L. Pyle, under Creative Commons License]

There is only modest knowledge of the fish and corals found within mesophotic coral ecosystems in American Samoa. We have little to no information about the physical environment, habitat characteristics, water quality, or distribution of mesophotic coral ecosystems in the region. Improving our scientific understanding of these poorly-known habitats will help resource managers proactively develop strategies to manage and protect these ecosystems.

American Samoa has several marine protected areas that contain mesophotic coral ecosystems, including National Marine Sanctuary of American Samoa, National Park of American Samoa,Rose Atoll Marine National Monument, and community-based marine protected areas managed by the American Samoa Department of Marine and Wildlife Resources. In addition to protecting fragile ecosystems, these marine protected areas serve as hubs for science projects like this one.


The project is led by the U.S. Fish and Wildlife Service, in partnership with Bishop Museum, the Hawai‘i Institute of Marine Biology at the University of Hawai‘i, Old Dominion University, and Papahānaumokuākea Marine National Monument.

The U.S. Fish and Wildlife Service’s Pacific Islands Fish and Wildlife Office will lead the overall project and research related to coral ecology and describing physical habitat characteristics. Bishop Museum will lead fish taxonomy and reproduction studies, conduct research on the diversity of algae and non-coral invertebrates, and identify environmental water characteristics.