Science Center Objects

Shallow water (less than ~150 m water depth) coral reefs are seafloor structures built from the calcium carbonate skeletons of marine organisms. Reefs buffer shorelines from waves, storm surges, and tsunamis and help to protect ~200 million of the world's coastal dwellers from flooding, erosion, property damage, and loss of life. Reefs support high levels of biodiversity; they are home to up to 25% of all ocean species. Developing nations in tropical regions rely on coral reef fisheries for food security. Coral reefs are also an economic driver for tourism, supporting jobs in the hotel, sport fishing, diving, clothing, and gear industries.

Image: Coral reefs, Kwajalein Atoll, Republic of the Marshall Islands

This unique perspective taken from underwater shows a wave crashing over a coral reef protecting the low-lying islands on Kwajalein Atoll in the Republic of the Marshall Islands. It clearly illustrates how healthy coral reefs cause waves to break offshore and dissipate their energy before reaching the shoreline, lessening the probability of coastal erosion and inundation. Credit: Curt Storlazzi, USGS

A cinderblock with monitoring devices on it sits in shallow water on a reef with corals growing on it and off in the distance.

The CMHRP is testing the calcification rates of different genetic strains of threatened Elkhorn coral (Acropora palmata) to advise local and Federal agencies engaged in coral reef restoration. Elkhorn coral is the sole Florida-Caribbean species responsible for creating the reef crest, which is the geological feature responsible for protecting shorelines from wave energy. Credit: Ilsa Kuffner, USGS

While coral reefs are valued for the economic and environmental services they provide, they are also significantly threatened. Since the 1970s, there has been a 70%–80% decrease in the abundance of reef-building corals along U.S. coastlines. Projections indicate that up to 66% of the world's remaining coral reefs will continue to degrade in the coming decades due to ocean warming and acidification. Additional local, regional, and global stressors such as disease, overfishing, land-based pollution, and invasive species have caused a cascading loss of reef-building organisms, biodiversity, and reef-habitat structure.

Underwater, a man wearing a t-shirt, board shorts, mask, snorkel, fins, and gloves secures an instrument to a coral reef.

USGS research geologist Curt Storlazzi free dives in order to set an instrument on the reef off Kauaʻi, Hawaiʻi in March 2015.

(Credit: Amy West, USGS Science Communications Contractor. Public domain.)

The CMHRP contributes to coral reef research by integrating geologic, physical, and biogeochemical information to determine the drivers and quantify the rates of past and modern coral reef formation and degradation, as well as characterize the impact of reef loss on seafloor structure and oceanographic processes. CMHRP studies identify local and global threats to reef ecosystems and provide a perspective on the health and resilience of and the risks to U.S. coral reefs within a global context. CMHRP scientific results are used by partnering agencies and nongovernmental organizations to guide conservation and protection strategies for critical refuge habitats and Endangered Species Act-listed species. CMHRP research complements the contributions of partnering agencies (e.g., National Park Service, U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration, Environmental Protection Agency, and other Federal, state, and local agencies), which lead long-term monitoring programs, map habitats, and conduct biologically and ecologically oriented research on coral reefs.

Past and Current Successes

Results from CMHRP research have shown that reef degradation in the U.S. Caribbean and Florida Keys has already caused significant loss of seafloor elevation, increasing coastline vulnerability to waves and storms. The CMHRP has also found that environmental conditions in some Pacific and Caribbean reefs protect them from the factors driving degradation such as ocean warming and acidification. The CMHRP has shown that in places (e.g., Hawai‘i, Guam) submarine groundwater  delivers far more nutrient contamination to reefs than rivers, leading to increased bio-erosion and loss of reef structure. These and other studies seek to establish the historical and contemporary conditions of coral reefs to inform forecasts about future changes in response to stressors such as changing ocean temperature and chemistry, coastal land use, and sea level.

Image: Diverse Corals of Hurricane Hole Bays

Diverse corals of Hurricane Hole Bays, U.S. Virgin Islands. The mountainous star coral (Montastraea faveolata) (background) is one of the largest colonies in these mangroves. In the foreground is a flower coral (Eusmilia fastigiata). Credit: Caroline Rogers, USGS

Underwater view of coral in some shades of pink where it is alive, shades of brown and green where it's dying.

Underwater photograph off Molokaʻi Hawaiʻi, showing some of the impacts of land-based pollution, such as terrestrial sediment, on coral reefs: burial by sediment, algal overgrowth, and coral bleaching.

Future Plans

The CMHRP will continue to support the resource management needs of partnering agencies by developing coral reef qualitative threat indices that reflect the impact of climate change, sea level rise, changing land use, restoration activities, and resource extraction, and by assigning risk levels to U.S. coral reef resources. An extension of the CMHRP's National Assessment of Coastal Change Hazards will address the vulnerability of coral reef coastlines, which are currently not explicitly included. These risk assessment activities will, in turn, inform numerical modeling to forecast the response of coral reefs to various stressors under a range of scenarios for twenty-first century change. As the program responsible for supplying the geologic expertise for U.S. coral reef studies, the CMHRP will continue to refine methods for detailed seafloor surveying in these settings and for more accurate measurement and prediction of seafloor elevation loss.

Photo of healthy staghorn coral at DRTO

Live Acropora cervicornis coral colonies create three-dimensional coral reef structure on the seafloor in Dry Tortugas National Park. Credit: Ilsa Kuffner, USGS