A mushroom cloud rises after the detonation of the 11-megaton nuclear device bomb 'Romeo' over Bikini Atoll in March 1954.
SOME corals are again flourishing on Bikini Atoll, the Pacific site of the largest American atom bomb ever exploded, but other species have disappeared.
A team of international scientists, including Australians, recently dived on the atoll, more than half a century after the stunning blast, to examine its marine life.
Zoe Richards from Queensland's James Cook University, along with other scientists from Germany, Italy, Hawaii and the Marshall Islands, said the team had dived into the vast Bravo Crater left by the 1954 atom bomb.
The 15 mega-tonne bomb was a thousand times more powerful than the one dropped on Hiroshima in Japan in WWII.
It vapourised three islands, raised water temperatures to 55,000 degrees, shook islands 200km away and left a crater 2km wide and 73m deep.
Ms Richards said she did not know what to expect when she dived on the crater but was surprised to find huge matrices of branching Porites coral - up to eight metres high - had established, creating thriving coral reef habitat.
"Throughout other parts of the lagoon it was awesome to see coral cover as high as 80 per cent and large tree-like branching coral formations with trunks 30cm thick.
"It was fascinating - I've never seen corals growing like trees outside of the Marshall Islands.''
The healthy condition of the coral at Bikini today was proof of the atoll's resilience and ability to bounce back from massive disturbances if the reef was left undisturbed and there were healthy nearby reefs to source the recovery.''
But Ms Richards said the research also revealed a disturbingly high level of loss of coral species from the atoll.
"Compared with a famous study made before the atomic tests were carried out, the team established that 42 species were missing compared to the early 1950s.
"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.''
The coral survey was carried out at the request of the atoll's local government.
For comparison the team also dived on neighbouring Rongelap Atoll, where no atomic tests were carried out directly although the atoll was contaminated by radioactive ash from the Bravo Bomb.
Local inhabitants were also evacuated and, for the most part, have not returned.
The marine environment at this atoll was found to be in a pristine condition.
"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,'' Ms Richards said.
http://www.heraldsun.com.au/news/world/corals-flourish-on-bikini-atoll/story-e6frf7mx-1111116066596
