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National Oceanic and Atmospheric Administration

Coral Reefs Ecosystem Essays

Northwestern Hawaiian Islands

This essay on the coral reef ecosystems of the Northwestern Hawaiian Islands (NWHI) is the first in a series on United States coral reef possessions offered by CoRIS.

The NWHI comprise a group of distant and remote islands, atolls, and shoals that span more than 1,200 miles of the North Pacific Ocean in a northwesterly direction from the Main Hawaiian Islands. Unlike coral reef ecosystems elsewhere in the world that are threatened by human mismanagement, the coral reefs of the NWHI are generally healthy and pristine.

In addition to descriptions of the ecosystems of the NWHI, the essay provides links to metadata and data for each particular island, atoll, shoal, and submerged bank. The ecological information presented in the essay is from the multi-agency Northwestern Hawaiian Islands Coral Reef Assessment and Monitoring Program (NOWRAMP) expeditions, the U.S. Fish and Wildlife Service, NOAA's National Ocean Service and National Marine Fisheries Service, the Bernice P. Bishop Museum, and the NOAA report on the State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2005. More detail...


Navassa is a small, remote, and uninhabited oceanic island located in the Windward Passage approximately 55 km west of the southwestern tip of Haiti. It is under United States jurisdiction administered by the U.S. Fish and Wildlife Service as a U.S. National Wildlife Refuge. The refuge includes a 12 mile radius of marine habitat around the island. Because of its remote location and uninhabited status, the surrounding marine ecosystem is basically unspoiled. Although there are no permanent residents on Navassa, transient Haitian subsistence fishers regularly visit the island, with detrimental effect on the fishes and edible invertebrates. Because of the island’s remoteness, existing protective regulations are not enforced.

In addition to descriptions of the coral habitats and communities of Navassa, the essay provides descriptions of the terrestrial communities and links to marine ecosystem metadata and data held by CoRIS. More detail.

Virgin Islands

The biologically rich coral reef ecosystems in the U.S. Virgin Islands (USVI) consist of a mosaic of benthic habitats, principally hard coral and other hard bottom areas, seagrass meadows, and mangrove forests that are home to a great diversity of organisms. These coral reef ecosystems provide, inter alia, shoreline protection and support valuable socio- economic activities. The USVI consists of three large main islands, east of Puerto Rico and several smaller islands. St. Croix is the largest island, St. Thomas is the second largest, and St. John is the third largest. Coral reefs in the USVI and reefs elsewhere in the Caribbean face similar environmental stresses which include climate change, diseases, storms, coastal development and runoff, coastal pollution, tourism and recreation, fishing, and vessel groundings. More detail.

The Republic of Palau (Belau)

Palau (or Belau), part of the Caroline Islands group, is the westernmost archipelago in Oceania. It is located 460 miles (741 km) east of Mindanao in the southern Philippines and about 808 miles (1,300 km) southwest of Guam. Palau is composed of nine or more inhabited islands and greater than 700 islets. The archipelago also has six isolated islands which lie approximately 211-372 miles (339-559 km) to the southwest. Numerous volcanic islands, atolls, raised limestone islands, and low coral islands comprise Palau. A barrier reef surrounds much of the main island cluster, merging into a fringing reef in the south. Palau has the most diverse coral fauna of Micronesia and the highest density of tropical marine habitats of comparable geographic areas around the world. In addition to coral reefs, mangrove forests, and seagrass meadows, Palau has deep algal beds, mud basins, current-swept lagoon bottoms, rich tidal channels, and anoxic basins within the Rock Islands.More detail.

Guam (Guahan)

Guam, a volcanic island completely surrounded by a coralline limestone plateau, is a U.S. territory located in the southernmost part of the Mariana Archipelago. It is the largest island in Micronesia and lies relatively close to the Indo-Pacific center of coral reefs. A variety of reef types are represented on Guam, including fringing reefs, patch reefs, submerged reefs, offshore banks, and barrier reefs. Fringing reefs are the predominant reef type, extending around much of the island. Guam possesses one of the most species-rich marine ecosystems among U.S. jurisdictions. More than 5,100 marine species have been identified from Guam's coastal waters, including over 1,000 nearshore fish species and 300 species of stony corals. More detail.