CANBERRA (Reuters) - Coral is again flourishing in the crater left by the largest nuclear weapon ever detonated by the United States, 54 years after the blast on Bikini Atoll, marine scientists said on Tuesday.
A team of research divers visited Bravo crater, ground zero for the test of a thermonuclear weapon in the remote Marshall Islands on March 1, 1954, and found large numbers of fish and coral growing, although some species appeared locally extinct.
"I didn't know what to expect, some kind of moonscape perhaps. But it was incredible," Zoe Richards, from Australia's James Cook University, told Reuters about the team's trip to the atoll in the south Pacific.
"We saw communities not too far from any coral reef, with plenty of fish, corals and action going on, some really striking individual colonies," she said.
The 15 megatonne hydrogen bomb was 1,000 times more powerful than the blast which destroyed Hiroshima, vaporizing islands with temperatures hitting 99,000 Fahrenheit, and shaking islands even up to 124 miles away.
The resulting 4 mile-wide fireball left a crater 1 mile across and 80 yards deep, while the mushroom cloud rose 62 miles over the South Pacific and radioactive fallout reached Australia and Japan.
Richards, from the Australian government-backed Centre of Excellence for Coral Reef Studies, said the research team from Germany, Italy, Hawaii, Australia and the Marshall Islands found corals up to 9 yards high and some with 12 inch-thick trunks.
"It was fascinating. I've never seen corals growing like trees outside of the Marshall Islands," Richards said.
While above-water areas remained contaminated and unfit for human habitation, healthy sub-sea species probably traveled on strong winds and currents from nearby Rongelap Atoll, which was not bombed in a series of 23 tests between 1946-58.
"It is absolutely pristine for another tragic reason. It received fallout and was evacuated of people, so now underwater it's really healthy and prevailing winds have probably been seeding Bikini Atoll's recovery," Richards said.
Compared with a study made before the atomic tests, the team established that 42 species were missing compared to the early 1950s, with at least 28 of those locally extinct.
The team was asked by Marshall Islands authorities to investigate Bikini for the first time since the tests, in part to see if a small diving industry could safely be expanded.
The waters around Bikini are littered with wrecks of old , decommissioned ships sunk during the atomic tests, including the aircraft carrier USS Saratoga and the former Japanese flagship HIJMS Nagato, from which Admiral Yamoto gave the order to attack Pearl Harbour.
Richards said the ability of Bikini's corals to bounce back from "a single huge destructive event" was proof of their resilience, although that did not mean the threat to corals from climate change had been overestimated.
"Climate change is an ongoing struggle to survive with coral, with no reprieve in sight," she said. "After the atomic blasts they had 50 years undisturbed to recover."
Marine life flourishes at Bikini Atoll test site
By Nick Squires in Sydney
Last Updated: 6:01pm BST 15/04/2008
It was blasted by the largest nuclear weapon ever detonated by the United States but half a century on, Bikini Atoll supports a stunning array of tropical coral, scientists have found.
In 1954 the South Pacific atoll was rocked by a 15 megatonne hydrogen bomb 1,000 times more powerful than the explosives dropped on Hiroshima.
The explosion shook islands more than 100 miles away, generated a wave of heat measuring 99,000ºF and spread mist-like radioactive fallout as far as Japan and Australia.
But, much to the surprise of a team of research divers who explored the area, the mile-wide crater left by the detonation has made a remarkable recovery and is now home to a thriving underwater ecosystem.
Bravo crater was ground zero for the test of the thermonuclear warhead on Bikini Atoll, in the remote Marshall Islands.
"I didn't know what to expect, some kind of moonscape perhaps. But it was incredible," Zoe Richards, from James Cook University in Australia, said. "We saw … plenty of fish, corals and action going on, some really striking individual colonies."
The scientists - from Australia, the US, Germany, Italy and the Marshall Islands - found corals up to 24 ft high with 10 inch thick trunks.
While surrounding islands remain contaminated and unfit for human habitation, healthy marine species were probably propelled by strong winds and currents from nearby Rongelap Atoll, which was not bombed in the atomic tests of 1946-58.
"The team thinks that Rongelap Atoll is potentially seeding Bikini's recovery because it is the second-largest atoll in the world with a huge amount of coral reef diversity and biomass and lies upstream from Bikini," said Ms Richards, from the government-backed Centre of Excellence for Coral Reef Studies.
While much marine life had been re-established, the researchers found that at least 28 species of coral previously found in the area had become locally extinct.
The team was commissioned by the Marshall Islands government to investigate Bikini for the first time since the tests, partly to see if a small diving industry could safely be expanded.
The waters around Bikini are littered with wrecks of World War Two decommissioned ships sunk during the tests, including the aircraft carrier USS Saratoga and the former Japanese flagship HIJMS Nagato, from which Admiral Yamoto gave the order to attack Pearl Harbour.
Ms Richards said the ability of Bikini's corals to bounce back from "a single huge destructive event" was proof of their resilience.
That did not mean, however, that the threat to coral reefs around the world from climate change had been overstated.
"Climate change is an ongoing struggle to survive with coral, with no reprieve in sight," she said. "After the atomic blasts they had 50 years undisturbed to recover."
The US Navy evacuated the inhabitants of Bikini in March 1946. At the time a US Navy Commodore told the islanders that the US was trying to learn how to use nuclear weapons for the good of mankind and asked them to "sacrifice their islands for the welfare of all men".
The Bikini islanders were moved by the US Navy three times. After nearly starving to death on the first island they were sent to, the population ended up on Kili Island in 1948, where they have lived since.
Numerous surveys of Bikini have concluded that the atoll is still not safe for human habitation.
(Editing by Michael Perry and Sanjeev Miglani)
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