This activity book was created with funding from NOAA CRCP grant NA19NOS4820057
Written & Illustrated by Cara Lin, Guam Department of Agriculture, as part of the National Coral Reef Fellowship 2020-2022
Edited by Whitney Hoot, Guam Bureau of Statistics and Plans
Marie Auyong, CSS, on contract to National Oceanic and Atmospheric Administration
Guam, a United.States. unincorporated territory, is the southernmost island in the Mariana Archipelago. It is located in the western Pacific approximately 3,700 miles west-southwest of Honolulu, Hawaii; 1,500 miles east of Manila; and 1,500 miles south-southeast of Tokyo, Japan. It is the largest island in Micronesia, with a land mass of 216 mi2 and a maximum elevation of approximately 405 meters. It is also the most heavily populated island in Micronesia with a population of about 168,000 people (July 2018 est). 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 seastar 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.