Coral Reef Project
Science Center Objects
Explore the fascinating undersea world of coral reefs. Learn how we map, monitor, and model coral reefs so we can better understand, protect, and preserve our Nation's reefs.
Cerulean damselfish dart around lettuce coral off the Cape Range National Park along the Ningaloo Coast in Western Australia. USGS researchers combined forces with Australian colleagues in this UNESCO World Heritage Site to conduct the most extensive study of how erosion of reefs contribute sand to the beaches—a coast’s natural armor. With the threat of a rising sea and changes to the climate, understanding this connection can tell us how resilient the coast will be.
Coral reefs are unique ecosystems of plants, animals, and their associated geological framework. Coral reefs cover less than 0.5 percent of the earth's surface, but are home to an estimated 25 percent of all marine species. Second only to tropical rainforests in size and complexity, some scientists estimate that more than one million species of plants and animals are associated with coral reefs. Coral reefs are also of great economic importance to those who live on or visit islands in the Pacific and Atlantic Oceans. Reefs shelter and provide nursery grounds for many commercially and culturally important species of fish and invertebrates, they protect the islands' harbors, beaches, and shorelines from erosion and wave damage by storms, and they are vital to the marine tourism industry. These diverse ecosystems provide valuable goods and services worth about $4 billion each year to the U.S.’s coastal communities. Yet, as important as coral reefs are, these ecosystems are being threatened worldwide.
More than 8,500 square miles (22,000 square kilometers) of coral reef habitat is found in U.S. waters. Most of these coral reefs still appear to be relatively healthy, but some areas of dead and dying coral have been found in recent years. The causes of this degradation are poorly known, but are probably in part related to human activities.
Photograph of waves breaking over the fringing coral reef that protects the shoreline of Waikīkī and infrastructure of Hawaiʻi's capital, Honolulu.
Credit: Brian Schmidt, licensed under CC BY 3.0 via Wikimedia Commons
The U.S. Geological Survey (USGS), working closely with academic institutions, state, and other Federal agencies, is spearheading an effort to better understand the geologic and oceanographic controls on the structure and processes of our Nation's coral reef ecosystems.
This web site is a gateway to USGS studies of coral reefs. We focus on the geophysical processes that influence the health and sustainability of coral reefs. From this work we are gaining new insight into the structure of coral reefs, providing the basis for future monitoring, and understanding better both the influences of natural processes and impacts of human activities on coral reef health. These efforts will help to preserve and protect the biodiversity, health, and social and economic value of these remarkable habitats.
Read more coral reef facts.
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.
Learn about our current studies by topic.
Climate Change and Land-use Histories
We are developing new and unique oceanographic and environmental archives from coral skeleton records to better understand the compounding effects of land-use and environmental change on coral reef health.
We are conducting geophysical and geochemical research to address questions about coastal groundwater-to-reef flow and coral reef health, with the goal of informing management decisions related to planning and implementing activities in priority watershed-coral reef systems.
Reef Hydrodynamics and Sediment Processes
We are developing a better understanding how tides, waves, currents, and both land- and reef-derived sediment influence the development of coral reefs and their adjacent shorelines.
Role of Reefs in Coastal Protection
We are combining ocean, engineering, ecologic, social, and economic modeling to provide a high-resolution, rigorous, spatially-explicit valuation of the coastal flood protection benefits provided by coral reefs and the cost effectiveness of reef restoration for enhancing those benefits.
Reef Resource Assessments - Planning for the Future
We are mapping and assessing all of the important geologic and oceanographic factors to identify those coral reefs most at risk and those reefs that are potentially the most resilient and the most likely to recover from natural and human-driven impacts.
Also, learn about our studies by location:
- Guam
- Hawai‛i
- Kaho‛olawe
- Kaua‛i
- Kwajalein Island
- Lāna‛i
- Maui
- Moloka‛i
- O‛ahu
- Puerto Rico
- Roi-Namur Island
- Tutuila
Please also see the associated Coral Reef Ecosystem Studies (CREST) Project website.
Our partners are numerous and include:
- U.S. Coral Reef Task Force (USCRTF)
- Department of the Interior
- Other Federal Partners
- State Partners
- Territorial and Commonwealth Partners
- Guam Division of Aquatic and Wildlife Resources
- Commonwealth of the Northern Mariana Islands Department of Land and Natural Resources
- American Samoa Department of Marine and Wildlife Resources
- Puerto Rico Department of Natural and Environmental Resources
- U.S. Virgin Islands Department of Planning and Natural Resources
- Academia
- University of California Santa Cruz - Institute of Marine Sciences
- University of Western Australia - Oceans Institute
- University of Puerto Rico at Mayaguez - Center for Applied Ocean Science & Engineering
- University of Hawaiʻi - Hawaiʻi Institute of Marine Biology
- Woods Hole Oceanographic Institution - Department of Geology and Geophysics
- Delft University of Technology - Department of Hydraulic Engineering
- Queen's University - Department of Civil Engineering
- University of Cantabria - Department of Sciences and Techniques in Water and Environment
- Non-governmental Organizations
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Date published: September 7, 2021Status: ActiveQuantifying Flood Risk and Reef Risk Reduction Benefits in Florida and Puerto Rico: The Consequences of Hurricane Damage, Long-term Degradation, and Restoration Opportunities
Coastal flooding and erosion from extreme weather events affect thousands of vulnerable coastal communities; the impacts of coastal flooding are predicted to worsen during this century because of population growth and climate change. Hurricanes Irma and Maria in 2017 were particularly devasting to humans and natural communities. The coral reefs off the State of Florida and the Commonwealth of...
Contacts: Curt Storlazzi, PhD, Michael Beck, Borja Reguero, Shay Viehman, Kim Yates -
Date published: September 7, 2021Status: ActiveRole of Reefs in Coastal Protection
We are combining ocean, engineering, ecologic, social, and economic modeling to provide a high-resolution, rigorous, spatially-explicit valuation of the coastal flood protection benefits provided by coral reefs and the cost effectiveness of reef restoration for enhancing those benefits.
Contacts: Curt Storlazzi, PhD -
Date published: September 7, 2021Status: ActiveThe Value of U.S. Coral Reefs for Risk Reduction
Summary of the report, “Rigorously valuing the role of U.S. coral reefs in coastal hazard risk reduction”
Contacts: Curt Storlazzi, PhD, Michael Beck -
Date published: August 26, 2021Status: ActiveClimate Change and Land-use Histories
We are developing new and unique oceanographic and environmental archives from coral skeleton records to better understand the compounding effects of land-use and environmental change on coral reef health.
Contacts: Nancy Prouty -
Date published: August 26, 2021Status: ActiveReef Resource Assessments - Planning for the Future
We are mapping and assessing all of the important geologic and oceanographic factors to identify those coral reefs most at risk and those reefs that are potentially the most resilient and the most likely to recover from natural and human-driven impacts.
Contacts: Curt Storlazzi, PhD -
Date published: August 26, 2021Status: ActiveCoral Reef Project: Kauaʻi
As part of the USGS Coral Reef Project, the USGS is working on the island of Kauaʻi to identify circulation patterns and a sediment budget for Hanalei Bay to help determine any effects to the coastal marine ecosystem.
Contacts: Curt Storlazzi, PhDAttribution: Pacific Coastal and Marine Science Center -
Date published: June 25, 2021Status: ActiveCoral Reef Project: Puerto Rico
To better understand how waves move across coral reefs and cause flooding on tropical shorelines, USGS scientists have installed video cameras and oceanographic instruments off San Juan and Rincón, Puerto Rico. Their work is part of a study funded by USGS after Hurricanes Irma and María. The offshore instruments measure wave heights and speeds; the onshore video cameras show where waves break...
Contacts: Curt Storlazzi, PhD -
Date published: June 25, 2021Status: ActiveReef Hydrodynamics and Sediment Processes
The overall objective of this research effort is to better understand how circulation and sediment processes impact coral reefs and their adjacent coastlines.
Contacts: Curt Storlazzi, PhD -
Date published: June 10, 2021Status: ActiveCoral Reef Project: Maui
As part of USGS Coral Reef Project studies, the USGS has been heavily involved in efforts to improve the health and resilience of Maui's coral reef system, bringing expertise in mapping, circulation and sediment studies, and seismic surveys.
Contacts: Curt Storlazzi, PhDAttribution: Pacific Coastal and Marine Science Center -
Date published: May 24, 2021Status: ActiveLow-lying areas of tropical Pacific islands
Sea level is rising faster than projected in the western Pacific, so understanding how wave-driven coastal flooding will affect inhabited, low-lying islands—most notably, the familiar ring-shaped atolls—as well as the low-elevation areas of high islands in the Pacific Ocean, is critical for decision-makers in protecting infrastructure or relocating resources and people.
Contacts: Curt Storlazzi, PhD
Rebounds, regresses, and recovery: A 15-year study of the coral reef community at Pila‘a, Kaua‘i after decades of natural and anthropogenic stress events
Pila‘a reef on the north shore of Kaua‘i, Hawai‘i was subjected to a major flood event in 2001 that deposited extensive sediment on the reef flat, resulting in high coral mortality. To document potential recovery, this study replicated benthic and sediment surveys conducted immediately following the event and 15 years later. Coral cores were...
Rodgers, Ku'ulei S.; Richards Dona, A.; Stender, Y. O.; Tsang, A. O.; Han, J. H. J.; Weible, Rebecca; Prouty, Nancy G.; Storlazzi, Curt D.; Graham, Andrew M. Bomb-produced radiocarbon across the South Pacific Gyre— A new record from American Samoa with utility for fisheries science
Coral skeletal structures can provide a robust record of nuclear bomb produced 14C with valuable insight into air-sea exchange processes and water movement with applications to fisheries science. To expand these records in the South Pacific, a coral core from Tutuila Island, American Samoa was dated with density band counting covering a 59-yr...
Andrews, Allen; Prouty, Nancy G.; Cheriton, Olivia Land-based sediment sources and transport to southwest Puerto Rico coral reefs after Hurricane Maria, May 2017 to June 2018
The effects of runoff from land on nearshore ecosystems, including coral reef communities, are influenced by both sediment supply and removal by coastal processes. Integrated studies across the land-sea interface describing sources and transport of terrestrial sediment and its nearshore fate allow reef protection initiatives to target...
Takesue, Renee K.; Sherman, Clark E; Reyes, Aaron O.; Cheriton, Olivia; Ramirez, Natalia I.; Viqueira Ríos, Roberto; Storlazzi, Curt Online-coupling of widely-ranged timescales to model coral reef development
The increasing pressure on Earth's ecosystems due to climate change is becoming more and more evident and the impacts of climate change are especially visible on coral reefs. Understanding how climate change interacts with the physical environment of reefs to impact coral growth and reef development is critically important to predicting the...
Hendrickx, Gijs; Herman, Peter M. J.; Dijkstra, Jasper T.; Storlazzi, Curt; Toth, Lauren T. Wave-driven flood-forecasting on reef-lined coasts early warning system (WaveFoRCE)
Increasing the resilience of coastal communities while decreasing the risk to them are key to the continued inhabitance and sustainability of these areas. Low-lying coral reef-lined islands are experiencing storm wave-driven flood events that currently strike with little to no warning. These events are occurring more frequently and with increasing...
Skirving, William; Storlazzi, Curt; Smail, Emily A Coral reef restorations can be optimized to reduce coastal flooding hazards
Coral reefs are effective natural coastal flood barriers that protect adjacent communities. Coral degradation compromises the coastal protection value of reefs while also reducing their other ecosystem services, making them a target for restoration. Here we provide a physics-based evaluation of how coral restoration can reduce coastal flooding for...
Roelvink, Floortje; Storlazzi, Curt; van Dongeren, Ap; Pearson, Stuart The value of US coral reefs for flood risk reduction
Habitats, such as coral reefs, can mitigate increasing flood damages through coastal protection services. We provide a fine-scale, national valuation of the flood risk reduction benefits of coral habitats to people, property, economies and infrastructure. Across 3,100 km of US coastline, the top-most 1 m of coral reefs prevents the 100-yr flood...
Reguero, Borja G.; Storlazzi, Curt; Gibbs, Ann E.; Shope, James B.; Cole, Aaron D.; Cumming, Kristen A.; Beck, Mike The contribution of currents, sea-swell waves, and infragravity waves to suspended-sediment transport across a coral reef-lagoon system.
Coral reefs generate substantial volumes of carbonate sediment, which is redistributed throughout the reef‐lagoon system. However, there is little understanding of the specific processes that transport this sediment produced on the outer portions of coral reefs throughout a reef‐lagoon system. Furthermore, the separate contributions of currents,...
Pomeroy, Andrew; Storlazzi, Curt; Rosenberger, Kurt J.; Lowe, Ryan; Hansen, Jeff; Buckley, Mark L. Role of future reef growth on morphological response of coral reef islands to sea-level rise
Coral reefs are widely recognised for providing a natural breakwater effect that modulates erosion and flooding hazards on low‐lying sedimentary reef islands. Increased water depth across reef platforms due sea‐level rise (SLR) can compromise this breakwater effect and enhance island exposure to these hazards, but reef accretion in response to SLR...
Masselink, Gerd; McCall, Robert T.; Beetham, Eddie; Kench, Paul; Storlazzi, Curt
Nearshore water quality and coral health indicators along the west coast of the Island of Hawaiʻi, 2010–2014
Coral reefs worldwide are experiencing rapid degradation in response to climate and land-use change, namely effects of warming sea-surface temperatures, contaminant runoff, and overfishing. Extensive coral bleaching caused by the steady rise of sea-surface temperatures is projected to increase, but our understanding and ability to predict where...
Grossman, Eric E.; Marrack, Lisa; vanArendonk, Nathan R. Spectral wave-driven bedload transport across a coral reef flat/lagoon complex
Coral reefs are an important source of sediment for reef-lined coasts by helping to maintain beaches while also providing protection in the form of wave energy dissipation. Understanding the mechanisms by which sediment is delivered to the coast as well as better constraining the total volumes generated are critical for projecting future coastal...
Rosenberger, Kurt J.; Storlazzi, Curt D.; Cheriton, Olivia; Pomeroy, Andrew; Hansen, Jeff E.; Lowe, Ryan; Buckley, Mark Internal tides can provide thermal refugia that will buffer some coral reefs from future global warming
Observations show ocean temperatures are rising due to climate change, resulting in a fivefold increase in the incidence of regional-scale coral bleaching events since the 1980s; analyses based on global climate models forecast bleaching will become an annual event for most of the world’s coral reefs within 30–50 yr. Internal waves at tidal...
Storlazzi, Curt D.; Cheriton, Olivia; Van Hooidonk, Ruben; Zhao, Zhongxiang; Brainard, Russell E.-
Date published: September 7, 2021Flooding extent polygons for modelled wave-driven water levels in Florida with and without projected coral reef degradation
This data release presents projected flooding extent polygon (flood masks) shapefiles based on wave-driven total water levels for the State Florida (the Florida Peninsula and the Florida Keys). There are 12 associated flood mask shapefiles: one for each of four nearshore wave energy return periods (rp; 10-, 50-, 100-, and 500-years), the current scenario (base) and each of the degradation...
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Date published: September 7, 2021Projected flooding extents and depths based on 10-, 50-, 100-, and 500-year wave-energy return periods for the State of Florida, the Commonwealth of Puerto Rico, and the Territory of the U.S. Virgin Islands for current and potentially restored coral reefs
This data release provides flooding extent polygons based on wave-driven total water levels for the coral lined coasts of Florida, Puerto Rico, and the U.S. Virgin Islands. The locations of the restoration lines along and across shore were defined by the presence of continuous coral/hardbottom habitat of greater than 100 m alongshore length and proximity to the 3-m depth contour. The wave and...
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Date published: September 7, 2021Projected flooding extents and depths based on 10-, 50-, 100-, and 500-year wave-energy return periods for the State of Florida and the Commonwealth of Puerto Rico before and after Hurricanes Irma and Maria due to the storms' damage to the coral reefs
This data release provides flooding extent polygons based on wave-driven total water levels for the coral lined coast of Florida and the Commonwealth of Puerto Rico. The wave and sea-level conditions were then propagated using the XBeach over 100-m spaced shore-normal transects modified to account for base and post-storm scenarios. In situ observations following hurricanes Irma and Maria
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Date published: June 8, 2021Coral geochemistry time series from Kahekili, west Maui
Geochemical analysis (including stable boron, boron:calcium ratio, and carbon and oxygen isotopes) were measured from coral cores collected in July 2013 from the shallow reef at Kahekili in Kaanapali, west Maui, Hawaii from scleractinian Porites lobata.
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Date published: April 21, 2021Model parameter input files to compare locations of coral reef restoration on different reef profiles to reduce coastal flooding
This dataset consists of physics-based XBeach Non-hydrostatic hydrodynamic models input files used to study how coral reef restoration affects waves and wave-driven water levels over coral reefs, and the resulting wave-driven runup on the adjacent shoreline. Coral reefs are effective natural coastal flood barriers that protect adjacent communities.
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Date published: March 26, 2021Cross-reef wave and water level data from coral reef environments
Direct field observations of wave dynamics across coral reefs and the resulting water levels are limited. Here we provide direct in situ measurements of waves and water levels across a number of coral reefs, extending from the fore reef, across the reef crest, and to the shoreline. These measurements are provided to help better understand the evolution of waves across coral reefs and...
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Date published: January 27, 2021Jurabi, Exmouth, Western Australia, 2016 Coral Reef Circulation and Sediment Dynamics Experiment
Carbonate reefs are a major source of sediment for coastlines in much of the tropical regions of the world, contributing to significant shoreline accretion and beach nourishment. A collaborative experiment between USGS and University of Western Australia was conducted to investigate determine the primary oceanographic processes responsible for cross-reef sediment transport. Data will be added...
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Date published: December 31, 2020Geochemistry time series and growth parameters from Tutuila, American Samoa coral record
Geochemical analysis (including radiocarbon, stable carbon isotope, and elemental composition) and growth parameters (including calcification rate, density, and extension information) were measured from a coral core collected from a reef off the southern side of Tutuila, American Samoa. The core was collected near Matautuloa Point on 8 April 2012 in collaboration with the Ecosys
Attribution: Pacific Coastal and Marine Science Center -
Date published: October 20, 2020Model parameter input files to study three-dimensional flow over coral reef spur-and-groove morphology
This data set consists of physics-based Delft3D-FLOW and SWAN hydrodynamic models input files used to study the wave-induced 3D flow over spur-and-groove (SAG) formations. SAG are a common and impressive characteristic of coral reefs. They are composed of a series of submerged shore-normal coral ridges (spurs) separated by shore-normal patches of sediment (grooves) on the fore reef of
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Date published: August 10, 2020
Modeled effects of depth and semidiurnal temperature fluctuations on predictions of year that coral reef locations reach annual severe bleaching for various global climate model projections
Using global climate model projections of sea-surface temperature at coral reef sites, we modeled the effects of depth and exposure to semidiurnal temperature fluctuations to examine how these effects may alter the projected year of annual severe bleaching for coral reef sites globally. Here we present the first global maps of the effects these processes have on bleaching projections for three...
The Role of U.S. Coral Reefs in Coastal Protection
U.S. Geological Survey research on flood protection provided by coral reefs. This is a story map that introduces research to understand the role of US coral reefs in coastal protection.
Reducing Flood Risks by Restoring Coral Reefs
The increasing risk of flooding along our coasts is driven by climate change, development and habitat loss.
Powerful climate-fueled hurricanes such as Irma and Maria in 2017 caused significant damage to coastal communities in Florida and Puerto Rico, not
How Our Reefs Protect Us: Valuing the Benefits of U.S. Reefs
The degradation of coastal habitats, particularly coral reefs, raises risks by increasing the exposure of coastal communities to flooding hazards during storms. The protective services of these natural defenses are not assessed in the same rigorous economic terms as artificial defenses, such as seawalls, and therefore often are not considered in decision-making. Here we
PubTalk 4/2018 - Coral Reefs
Title: The Role of U.S. Coral Reefs in Coastal Protection - Rigorously valuing flood reduction benefits to inform coastal zone management decisions
- Coral reefs are a first line of coastal defense
- We can account for the physical defense that reefs provide
- We can provide value-based information to guide restoration efforts at management-relevant
What's Drifting Beneath Kauai's Ocean?
Residents and visitors both revel in Kauai’s lush landscape, and beneath its seascape. However, it’s underwater where things don’t look so healthy. Scientists from the U.S. Geological Survey put together a detailed picture of the physical environment of the coral reefs at Makua Beach. Understanding just what these reefs are exposed to and for how long, may help explain why
Breaking Down Reefs, Building Up Beaches
On the remote western coast of Australia lies a UNESCO World Heritage Site above and below the sea. Researchers from the U.S. Geological Survey and University of Western Australia convened here at Ningaloo Reef and Jurabi Coastal Reserve to embark on the most extensive study EVER done into how coral reefs shape our coasts.
Exploring Causes of Coral Disease
The Hawaiian Islands’ beautiful ocean and beaches attract more than 8.5 million tourists each year. The USGS aims to help Hawaii preserve its underwater natural resources by tracing how oceanography may influence coral disease outbreaks. Looking into contaminants in the freshwater, or how quickly a bay may or may not flush, will help enrich future and past studies about
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Date published: September 7, 2021
Reducing Flood Risks by Restoring Coral Reefs
Healthy coral reefs are more than just hotspots of marine biodiversity—they’re also invaluable to long-term resilience against coastal storms.
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Date published: July 23, 2021SPCMSC and PCMSC scientists participating in 14th International Coral Reef Symposium
USGS research will be presented by several USGS scientists during the virtual 14th International Coral Reef Symposium taking place 19-23 July 2021.
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Date published: May 12, 2021USGS Scientists Add Another Piece to Puzzle of How Hurricanes Can Gain Strength
Unique observations collected by U.S. Geological Survey scientists during Hurricane María in 2017, revealed previously unknown ocean processes that may aid in more accurate hurricane forecasting and impact predictions.
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Date published: February 4, 2020USGS collaborates with National Park Service to study threatened coral reefs in American Samoa
USGS scientists from the Pacific Coastal and Marine Science Center and the St. Petersburg Coastal and Marine Science Center are cooperating with the National Park Service to better understand links between coastal groundwater and coral reef health on the island of Ofu in the National Park of American Samoa (NPSA).
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Date published: July 1, 2019Maui-area coral reefs described in detail, including threats
A new USGS Open-File Report describes the coral reefs of Maui, Moloka‘i, Lānaʻi, and Kahoʻolawe in detail, including location, extent, coral cover, and connectivity.
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Date published: April 30, 2019Coral Reef Barriers Provide Flood Protection for More Than 18,000 People and $1.8 Billion Worth of Coastal Infrastructure and Economic Activity Annually
Today, the U.S. Geological Survey (USGS) released the findings of a new, in-depth study titled “Rigorously Valuing the Role of U.S. Coral Reefs in Coastal Hazard Risk Reduction,” – funded in part by the U.S. Department of the Interior’s (DOI) Office of Insular Affairs –
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Date published: November 29, 2018Studying flood hazards in San Juan, Puerto Rico
USGS scientists from Pacific Coastal and Marine Science Center, along with with NOAA, the University of Puerto Rico-Mayaguez, and Arrecifes Pro Ciudad, are using video imagery and wave measurements to study flood hazards in San Juan, Puerto Rico.
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Date published: September 7, 2018Hurricane Maria’s impacts on deep-water coral reefs off Puerto Rico
USGS research geologist Curt Storlazzi was quoted in an August 22 Nature news article about Hurricane Maria’s effects on deep-water coral reefs off Puerto Rico.
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Date published: May 7, 2018Public lecture on coral reefs as coastal protection
On Thursday, April 26, research geologist Curt Storlazzi of the USGS Pacific Coastal and Marine Science Center gave a public lecture on “The Role of U.S. Coral Reefs in Coastal Protection—Rigorously valuing flood reduction benefits to inform coastal zone management decisions.”
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Date published: March 30, 2018Polluted Groundwater Threatens Hawaiian Coral Reefs
According to a study by USGS scientists, polluted, low-pH groundwater discharging onto a shallow coral reef off Kahekili Beach Park in west Maui, Hawai‘i, further increases seawater acidity and exposes corals to nitrate concentrations 50 times higher than normal.