Guam, a U.S. unincorporated territory located at 13° 28' N, 144° 45' E, is the southernmost island in the Mariana Archipelago. It’s location in the western Pacific is approximately 3,700 miles west-southwest of Honolulu; 1,500 miles east of Manila; and 1,500 miles south-southeast of Tokyo. It is the largest island in Micronesia, with a land mass of 560 km2 and a maximum elevation of approximately 405 meters. It is also the most heavily populated island in Micronesia with a population of about 164,000 people (est. July 2003). The northern portion of the island is relatively flat and consists primarily of uplifted limestone. The southern half of the island is primarily volcanic, with more topographic relief and large areas of highly erodible soils. This topography creates a number of watersheds throughout the southern areas which are drained by 96 rivers.
The condition of Guam’s coral reefs (including fringing reefs, patch reefs, submerged reefs, offshore banks, and barrier reefs) varies considerably, depending on a variety of factors including geology, human population density, degree of coastal development, levels and types of marine resource uses, oceanic circulation patterns, and frequency of natural disturbances (e.g., storms and earthquakes). Many of Guam’s reefs have declined in health over the past 40 years. However, in the past, Guam’s coral reefs have recovered after drastic declines. For example, an outbreak of the crown - of - thorns starfish in the early 1970s reduced coral cover in some areas from 50 to 60% to less than 1%. Twelve years later, greater than 60% live coral cover was recorded for these areas. A more distressing indicator of the condition of Guam’s coral reefs is the marked decrease in rates of coral recruitment.
Reefs unaffected by sediment, nutrient loading, and freshwater runoff in the northern part of the island and between river outflows, have relatively healthy coral communities. The reefs have not suffered the large scale bleaching events and coral diseases seen in other parts of the world. Unfortunately, some reefs have been damaged by land-based sources of pollution and heavy fishing pressure.
Guam's Coral Reef Management Priorities
Guam Capacity Assessment Report and Coral Reef Conservation Time Line
Status of coral reef fish assemblages and benthic condition around Guam: A report based on underwater visual surveys in Guam and the Mariana Archipelago, April-June 2011 U.S. Dept. of Commerce, NOAA Technical Memorandum NOAA-TM-NMFS-PIFSC-33, 22
Report on the Status of Marine Protected Areas in Coral Reef Ecosystems of the United States. Volume 1: Marine Protected Areas Managed by U.S. States,Territories, and Commonwealths. NOAA Technical Memorandum CRCP 2 February 2007
Potential larval sources, destinations, and self-seeding in the Mariana Archipelago documented using ocean drifters (Journal of Oceanography, 2014)
Search the CoRIS Geoportal for Guam metadata, data and publications
Select "Micronesia" in the Region window and "Guam" in the Country window
NOAA/National Weather Service - Data for Guam
USGS Water Resources - Data for Guam
NOAA CO-OPS Tide data
NOAA Tide Predictions - Guam
Guam Coastal Atlas - The atlas provides benthic habitat maps and geospatial data for the nearshore waters of Guam.
Pacific Islands Benthic Habitat Mapping Center - Guam
Coastal Change Analysis Program (C-CAP) Landcover Data - Guam