AS marine scientists dived into the watery depths of a huge crater caused by the largest nuclear bomb ever detonated by the United States they expected to find a desolate moonscape, devoid of life.
But the deeper they swam they were amazed to fi
nd themselves surrounded by a lush world of giant coral as big as trees, and huge shoals of fish.
On 1 March 1954 a bomb a thousand times as powerful as that which destroyed Hiroshima in the Second World War, was set off on the remote Pacific island Bikini Atoll, in the Marshall Islands.
The 15 megatonne hydrogen bomb left a crater one mile across and 80 yards deep, and caused a mushroom cloud that rose 62 miles over the South Pacific.
The fireball created by the bomb vapourised some islands and shook communities as far as 124 miles away, raised water temperatures to 55,000 degrees Celsius and radioactive fallout reached Australia and Japan.
When the scientists went to study the underwater environment in Bravo crater for the first time since the blast they were surprised to discover it is not the sterile environment they were expecting, but is teeming with huge Porites coral sustaining a thriving underwater ecosystem.
"I didn't know what to expect, some kind of moonscape perhaps," said Zoe Richards, from James Cook University in Australia, "But it was incredible.
"We saw communities not too far from any coral reef, with plenty of fish, corals and action going on, some really striking individual colonies."
The research team, made up of scientists from Germany Italy, Hawaii, Australia and the Marshall Islands, were thrilled to discover tree-like corals up to nine yards high, with trunks up to 12 inches thick.
For comparison the team also dived on neighbouring Rongelap Atoll, which was left untouched during a series of 23 tests by the Americans between 1946-58, and the marine environment there was pristine.
Ms Richards thinks healthy sea species must have travelled on strong winds and currents from Rongelap Atoll, to seed Bikini's recovery.
Rongelap Atoll is the second largest atoll in the world with a vast coral reef diversity and lies upstream of Bikini.
"The healthy condition of the coral at Bikini Atoll today is proof of their resilience, if the reef is left undisturbed and there are healthy nearby reefs to source the recovery," she said.
But Ms Richards does not think the resilience of Bikini Atoll means the impact on corals from the even more ominous threat of climate change has been over-estimated.
"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."
Despite the incredible underwater world, life above the sea on Bikini Atoll is still far from back to normal. Decontamination work means it is safe to visit, but fruit such as coconuts that grow locally are so full of radiation they are unsafe to eat, and the Bikinians evacuated before the blast have not yet returned home.
Maria Beger from the Commonwealth Research Facility for Applied Environmental Decision Analysis at The University of Queensland thinks the lack of people in Bikini Atoll could also have played a part in keeping the ecology pristine and undamaged.
"Apart from occasional forays of illegal shark, tuna and Napoleon Wrasse fishing, the reef is almost completely undisturbed to this day," she said. "There are very few local inhabitants and the divers who visit, dive on shipwrecks, like the USS Saratoga, and not on the reef."
She took a Geiger counter with her which helped explain why the food grown there is not safe to eat.
"The ambient gamma radiation on the residential island of Bikini Atoll was fairly low – pretty much like the background radiation in an Australian city," she said.
"However, when I put the Geiger counter near a coconut, which accumulates radioactive material from the soil, it went berserk."
UK nuclear and climate change expert Anthony Day said 50 years was quite a long time for the atoll to recover.
"It's very similar to what they found near Chernobyl. Because they evacuated the area the wildlife and the plants are undisturbed. They have come back in a way that's very unusual."
Even though the research team, which has just published its report, discovered a thriving marine environment at Bikini Atoll, not all their findings were positive. Despite the booming coral populations and fish stocks, a disturbingly high level of coral species were wiped out from the atoll by the shattering blast.
A total of 42 species present in the region before the blast are now missing. "At least 28 of these species losses appear to be genuine local extinctions probably due to the 23 bombs that were exploded there from 1946-58, or the resulting radioactivity, increased nutrient levels and smothering from fine sediments," said Ms Richards.
Now Bikini Atoll could become a top diving destination.
The team was asked by the Marshall Islands authorities to investigate Bikini, partly to see if a small diving industry based there could be safely expanded.
Divers are attracted by wrecks that litter the waters around Bikini – mainly 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.
But locals are unlikely to return to live on the atoll in the near future. Even though decontamination works have been carried out to make sure it is safe to visit, local produce is unsafe to eat.
A large population of Bikinians live elsewhere in the Marshall Islands, desperate to return home but afraid of the contamination risks.
It is reported that in 1946 Commodore Ben Wyatt, the military governor of the Marshalls, travelled to Bikini and on a Sunday after church, he assembled the 167 Bikinians to ask if they would be willing to leave their atoll temporarily so that the United States could begin testing atomic bombs.
King Juda, then the leader of the Bikinian people, stood up after much confused and sorrowful deliberation among his people, and announced they would go, saying everything was in the hands of God.
MARINE TREASURETHE Porites coral found in such abundance in Bikini Atoll is often referred to as the Jewelled Finger, Jewel, or Finger Coral.
A green or yellow branching form of the coral is most common, but it is found in a variety of shapes and colours.
Polyps on the surface of the coral can expand and give it a fuzzy appearance.
The yellow colour of the coral makes it a very attractive part of underwater ecosystems.
Corals are the crucial building blocks of reefs, which are so important for sustaining sea life.
They are highly sensitive to environmental changes and scientists have predicted that more than 50 per cent of the coral reefs in the world may be destroyed by 2030.
Coral reefs can easily be swamped in algae if there are too many nutrients in the water.
The full article contains 1207 words and appears in The Scotsman newspaper.
