Fifty years after the last atomic blast shook the Pacific
atoll of Bikini, the corals are flourishing again -
new research shows - although divers found that some
coral species appear to be locally extinct.
At the request of the atoll's local government, an
international team of scientists from Australia, Germany,
Italy, Hawaii and the Marshall Islands examined the
diversity and abundance of marine life around the atoll.
They dove into the vast Bravo Crater left in 1954 by the
most powerful American atom bomb ever exploded. At 15 megatonnes
of TNT, it was 1,000 times more powerful than the bomb dropped
on Hiroshima in World War II.
The Bravo bomb vapourised three islands, raised water temperatures
to 55,000 degrees, shook islands 200 kilometers away and left
a crater two kilometers wide and 73 meters deep.
"I didn't know what to expect - some kind of moonscape perhaps"
- said Zoe Richards of the ARC Centre of Excellence for Coral
Reef Studies and James Cook University. "But it was incredible,
huge matrices of branching Porites coral up to eight
meters high had established, creating thriving coral reef
"Throughout other parts of the lagoon it was awesome to see
coral cover as high as 80 percent and large tree-like branching
coral formations with trunks 30cm thick" - she added. "It
was fascinating - I've never seen corals growing like trees
outside of the Marshall Islands."
However, the team documented a 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 to 1958, or the resulting radioactivity,
increased nutrient levels and smothering from fine sediments.
While corals, in general, have shown resilience, she says
the coral biodiversity at Bikini Atoll has proven only partially
resilient to the disturbances that have occurred there.
Maria Beger from the Commonwealth Research Facility for Applied
Environmental Decision Analysis at The University of Queensland
took a Geiger counter with her on the expedition. "The ambient
gamma radiation the residential island of Bikini atoll was
fairly low - pretty much like the background radiation in
an Australian city. However, when I put the Geiger counter
near a coconut - which accumulates radioactive material from
the soil - it went berserk” - Beger said.
Extensive decontamination works have been carried out at
Bikini atoll, making it safe to visit, but local produce is
not safe to eat and it is unlikely the Bikinian people will
return to live on Bikini Atoll in the near future.
For comparison, the team also dived on neighboring Rongelap
Atoll, where no atomic tests were carried out directly - although
the atoll was contaminated by radioactive ash from the Bravo
Bomb and 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
The team was of the opinion that Rongelap Atoll may be seeding
Bikini's recovery, because it is the second largest atoll
in the world with lots of coral reef diversity and biomass
and lies upstream from Bikini.
Richards says that, due to the bombs, Bikini Atoll is a priceless
laboratory showing how in the absence of ongoing stress, some
corals have the capacity to recover from upheavals - a fact
that may contain valuable lessons for the management of reefs
in other parts of the world, including Australia.
Because of its incredible history and current undisturbed
character, Bikini Atoll is now part of a larger project to
have northern Marshall Island Atolls placed on the UNESCO
World Heritage List for conservation.
"The healthy condition of the coral at Bikini atoll today
is proof of their resilience and ability to bounce back from
massive disturbances - that is, if the reef is left undisturbed
and there are healthy nearby reefs to source the recovery"
- said Richards.