This month marks a year since BP’s Macondo well in the Gulf of Mexico blew out, spewing nearly five million barrels of oil in the largest accidental marine oil spill in history. Much more recent – and still ongoing – is the nuclear aftermath following the 9.0 magnitude Tohoku earthquake and tsunami last month. The tsunami, in addition to causing huge loss of life and property, resulted in partial core meltdowns in several nuclear reactors and significant releases of radiation-contaminated water into the sea following several last-ditch cooling attempts. Radioactive cesium-137 was subsequently found in the waters adjacent to the reactors at levels 10-100 times higher than those measured in the Black Sea after Chernobyl, potentially making Fukushima the worst nuclear accident on record with regards to its effect on the ocean.
Woods Hole Oceanographic Institution senior scientist Ken Buesseler considers Japan’s irradiated waters, noting that "the ocean has the ability to mix and dilute even these alarmingly high concentrations of contaminants." He goes on to write:
"Indeed, just 15 miles offshore the levels of some contaminants, including cesium-137, with its relatively long 30-year half-life, are already 100 to 1,000 times lower than waters near the reactors, and thus pose little direct hazard for human exposure."
But aside from this bit of good news, Buesseler focuses on what remains unknown about the Fukushima disaster: the full complement of radionuclides (including highly-toxic plutonium) released into the oceans has not been measured. Nobody knows where the nuclear contaminents are spreading to, or the rate at which they are dispersing. And perhaps most importantly: "There are large gaps in our knowledge of how marine life assimilates radioactive contaminants, how the process may vary depending on different life stages, or how contaminants will transfer up the food chain to fish and other marine animals."
These unknowns echo questions still being raised about the aftermath of the BP oil spill in the Gulf after a year, where at least a million barrels of oil remain unaccounted for. In an article for Scientific American, David Biello looks into this missing oil, also finding that the unknowns overshadow the knowns. He cites a report on the fate of oil from December 16, 2010: "Months later, it is unknown what happened to the oil that remained….It is debatable whether the fate of the remaining oil will ever be established conclusively."
Judging by what what remains unresolved a year after the BP spill, it seems likely that we’ll never really know the full impact Fukushima’s fallout will have on marine organisms. Like oil, radioactive contaminants can kill organisms outright, as well as travel up the food chain, initially accumulating in iodine-absorbing plants such as kelp. But we know far less about the long-term effects radiation will have on animal reproduction. According to Joseph Rachlin, director of Lehman College’s Laboratory for Marine and Estuarine Research in NYC:
"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… that’s the main problem as I see it with radiation—altering the genetics of the animal and interfering with reproduction."