Part of the Mariana Islands in the Pacific Ocean and almost entirely surrounded by coral reefs, Guam is the biggest island in Micronesia. Soil sedimentation, or the suspension of soil particles in the river, is a major problem for Guam's central and southern reefs. Rivers carry soil sediment, which accumulate on the coral, restricting light and oxygen. Located near the Ugum and Talafofo rivers, these reefs receive an estimated 290 tons of sediments per hectare annually. Heavy metals and other pollutants are found in sediments of Apra Harbour, affecting southwestern reefs. Nearby rivers carrying these sediments include the Atantano, Sasa, Aguada, Big Guatali, Aplacho, Maggo, Guatali, Laghas, Tenjo and Paulana.
The Maluku Islands are in Indonesia, one of the richest areas in the world for coral reef diversity. One of the smallest islands in the archipelago, Haruku Island has an extensive coastal reef. Located on its southwest coast, the mouth of the Learisa Kayeli river is near to Haruku coral reef, which has been heavily damaged by sedimentation from soil erosion and mine exploration.
Mozambique is located on the East African coast, an area with a lot of
river discharges and high nutrient concentration, which negatively affects the country's coral reefs by increasing the growth of surrounding algae, which compete with corals for space and available oxygen. The Limpopo and Zambezi rivers have been responsible for the creation of large coral-free patches along the coast, but small fringing coral still survive in some areas. Mozambique's main reef system stretches from the Rovuma River in the north to Pebane in the south.
Part of the Caribbean island of Hispaniola, the Dominican Republic has coral reefs scattered along its coastline. The mountainous terrain and the presence of large rivers, such as the Yaque del Norte River, results in high sediment concentration near coastal reefs. The country's largest barrier reef formation is found on the northern coast, near the Yaque del Norte River.