ABSTRACT
The Marshall Islands are a group of 34 islands, 29 of which represent atolls forming two parallel north–south chains. There are 16 atolls in the western Ralik Chain and 13 in the eastern Ratak Chain. The Marshall Islands are part of Micronesia and constitute a sovereign island nation that depends heavily on its relationship with the U.S., an alliance that stems from conflicts during World War II and post-war nuclear testing, especially on Enewetak and Bikini, the two northernmost atolls. Much of what is known about atoll structure and biological function was derived from studies conducted in those locations. The dominant flows include the westward North Equatorial Current in the northern Marshall group and the east-flowing North Equatorial Countercurrent to the south. The most common waves are wind-driven with an easterly component, but swell from the northwest or south, and local cyclones can also impact the atolls. Tides aregenerally less than 1.75 m. Almost all the atolls located here form open rims. The Marshallese people are skilled navigators who used their prowess in shipbuilding and stick chart models to travel between islands and even between chains. The atoll of Kwajalein, which is located near the center of the Ratak Chain, includes one of the Earth’s largest atoll lagoons and nearby Ebeye Island is beset by one of the highest population densities of any atoll, approaching 47,000 individuals per km2. In addition, Majuro in the southeastern Ralik Chain is the capital of the Marshall Islands and is one of the most urbanized atolls in the world.
