Radiation in Japan Seas : Marine life in danger
Christine Dell’Amore
More radiation from nuclear plant
could cause ‘bizarre mutations.’
If radioactive material from the Fukushima Daiichi nuclear power
plant-disabled by the March11 Japan earthquake and tsunami-continues to
enter the ocean, marine life could be threatened, experts say.
Aboard a boat pulling a barge with water for Japan’s overheating
Fukushima nuclear plant Thursday.
Photograph from Japan Maritime Self-Defence Force via Reuters |
In the past week, seawater samples taken near the nuclear power
plant, on Japan’s eastern coast, have shown elevated levels of
radioactive isotopes, including cesium 137 and iodine 131, according to
the New York Times.
All life on Earth and in the oceans lives with exposure to natural
levels of ionizing radiation-high-frequency radiation with enough energy
to change DNA. Most such genetic damage heals, but the addition of
human-made radiation can make it harder for the body to repair broken
genes.
Radiation concentrations in the Japanese seawater samples have
fluctuated in past days, but on Wednesday the amount of iodine spiked to
3,355 times the legal limit for seawater, Japanese nuclear safety
officials told the Associated Press.
That level is the highest so far-and an indication that more
radiation is entering the ocean, though how is still unknown, the agency
reported. Cesium was also found to be 20 times its safety limit on March
28, according to the Times.
Once in seawater, radiation can hurt ocean animals in several ways-by
killing them outright, creating “bizarre mutations” in their offspring,
or passing radioactive material up the food chain, according to Joseph
Rachlin, director of Lehman College’s Laboratory for Marine and
Estuarine Research in New York City.
“There will be a potential for a certain amount of lethality of
living organisms, but that’s less of a concern than the possible effects
on the genetics of the animals that become exposed,” Rachlin said.
“That’s the main problem as I see it with radiation-altering the
genetics of the animal and interfering with reproduction.”
Even so, according to radioecologist F. Ward Whicker, the
concentrations of iodine and cesium levels “would have to be orders of
magnitude larger than the numbers I’ve seen to date to cause the kind of
radiation doses to marine life that would cause mortality or reductions
in reproductive potential.
“I am very doubtful that direct effects of radioactivity from the
damaged reactors on marine life over a large area off the coast of Japan
will be observed,” Whicker, professor emeritus at Colorado State
University, said via email.
Likewise, using legal limits to gauge damage to marine life is of
little value right now, he said.
To make a “credible assessment” of the risk to marine animals,
scientists would have to know the actual concentrations of radioactive
iodine in the water and fish or other marine animals off Fukushima
Daiichi, he said.
Threat to local marine life
It’s possible that levels of radioactive contamination near the
Fukushima nuclear reactors could increase and cause some harm to local
marine life, Whicker said.
“If this happens, the most likely effects would be reductions in
reproductive potential of local fishes. ... ,” he said.
Marine organisms’ eggs and larvae are highly sensitive to radiation,
since radioactive atoms can replace other atoms in their bodies,
resulting in radiation exposure that could alter their DNA, Whicker
said.
Most such deformed organisms don’t survive, but some can pass
abnormalities on to the next generation, Lehman College’s Rachlin said.
Either way, the radiation exposure could hurt the population’s ability
to survive long-term.
Rachlin thinks the most susceptible critters would be soft-bodied
invertebrates such as jellyfish, sea anemones, and marine worms-which
can take up the radiation more quickly than shelled creatures-though
Whicker said fish may be most at risk.
Whicker added, “I would expect any temporary losses in reproduction
in local fish to be offset by immigration of unaffected individuals from
surrounding areas that would be impacted to a lesser degree.”
In addition to its threats to reproduction, pockets of radioactive
material can can burn fish passing through, hitting them like a stream
of searing water, Rachlin said.
Complicating matters is the fact that predator species in the Pacific
such as tuna and sailfish are already stressed by overfishing, according
to Rachlin.
“I’m concerned-this is the spawning season. ... If this impacts the
survivorship of the young and larvae, this will be a further insult.”
According to chemical oceanographer Bill Burnett, “In the short run
[the radiation] could have some definite negative impacts” on marine
life.
“The good news is the half life [of iodine] is only eight days,”
added Burnett, an expert in environmental radioactivity at Florida State
University.
So “if they stop the source of radioactive leakage, this is going to
be a short-term problem.”
However Fukushima Daiichi’s leaking cesium is potentially more
serious, since that isotope takes 30 years to decay, Burnett said.
There could also be some movement of radiation up the food chain if
animals eat irradiated plants and smaller, radioactive animals, Rachlin
said.
In particular, plants such as kelp can quickly absorb iodine, FSU’s
Burnett said. There’s a possibility that the devastation of towns in
northeastern Japan caused by the earthquake and tsunami also released
toxic metals such as lead into the soil and water, according to Texas
Tech University ecotoxicologist Ron Kendall.
Previous studies have shown that metals can work in concert with
radiation to suppress immune systems in vertebrates, making them more
vulnerable to disease, Kendall said. It’s a “big issue for the
environment and human health because of the widespread destruction. It
takes me back to New Orleans after Hurricane Katrina-this to me is even
more complicated with the radiation.”
Ocean resilient against radiation
The ocean has a “tremendous capacity” for diluting radiation,
Colorado State’s Whicker noted.
“It also has resilience, in the sense that the area would recover
over time as the situation improves and as the radioactivity decays and
disperses.”
“But I should caution that we have not had much opportunity to study
the effects of very large releases of radioactivity into marine
ecosystems,” he said. The best data comes from nuclear weapons tests in
the Pacific in the 1950s and 1960s.
Texas Tech’s Kendall also pointed out that there’s not much known
about radiation in seawater.
“The dose makes the poison,” he said, “and the more concentrated the
radiation, the more potential effects. It’s something we definitely need
to monitor.”Added Lehman’s Rachlin: “If it’s a one-shot pulse, OK, not a
problem.
But if the radiation leaks continue for several months, Japan may be
dealing with a more serious blow to marine life, he said.
The coastline, after all, isn’t Chernobyl, he said. “We can’t cement
[over] that whole area.”
-National Geographic |