After WWII, the U.S. detonated 23 nuclear bombs at Bikini Atoll; nearly 70 years later, it’s a thriving habitat for marine species

Surprisingly, one of the best places in the Pacific Ocean to find an abundance of corals, tropical fish, and sharks is Bikini Atoll, a former United States nuclear test site.

In the tense years following World War II, the United States conducted 23 nuclear tests at Bikini Atoll between 1946 and 1958. One of them, codenamed Castle Bravo, was a hydrogen bomb that remains to this day the largest U.S. nuclear detonation in history. Reaching a yield of 15 megatons, it was a thousand times more powerful than the atomic bomb dropped on Hiroshima.

During the detonations, sea-surface temperatures soared to 55,000 degrees Celsius, virtually wiping out all life. Marine ecosystems had to start completely over from scratch.

A recovering ecosystem

In 2008, scientists estimated that nearly 65% of the area’s biodiversity had returned. However, not every species survived the nuclear fallout—28 coral species are still missing from the region and are believed to be locally extinct.

Hard corals are critical to a reef’s structural architecture, generating a complex three-dimensional habitat for fish and invertebrates—which, in turn, attract apex predators like sharks.

The United States bombed the USS Saratoga (CV-3) during atomic tests in 1946, and the aircraft carrier now rests at the bottom of Bikini Atoll. Greg Asner, director of ASU’s Center for Global Discovery and Conservation Science, led an expedition to the site and discovered that 23 percent of known hard coral genera were growing directly on the sunken aircraft carrier.

His crew surveyed seven additional ships, including the battleship Arkansas and the Japanese Imperial Navy’s flagship Nagato—the vessel Admiral Yamamoto used to orchestrate the 1941 attack on Pearl Harbor.

According to Asner’s findings, the team tallied 33 hard coral genera across the wrecks, representing roughly 27 percent of the global total.

An accidental sanctuary with a tragic legacy

The nuclear tests permanently altered the history of Bikini Atoll and the Marshall Islands, driving the forced displacement of native inhabitants and causing widespread human irradiation and environmental contamination from radioactive fallout.

Furthermore, the detonations at Bikini Atoll—and Cold War testing as a whole—gave rise to some of the most defining and frightening imagery of the nuclear era.

Today, Bikini Atoll still holds sunken munitions and fuel reserves scattered across its seabed, and human presence remains strictly limited due to residual radioactive isotopes, according to UNESCO.

Yet, this isolation has turned the site into an unexpected ecological laboratory. “The terrible history of Bikini Atoll is an ironic setting for research that might help people live longer. By understanding how corals could have recolonized the radiation-filled bomb craters, maybe we can discover something new about keeping DNA intact,” said Stanford biology professor Stephen Palumbi.

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