Are Fish Affected by Radioactive Kelp off our Coast?

Fish along Southern California's coast may have been affected by Fukushima's radioactivity that fell on California in the days after Japan's 2011 nuclear disaster, as small levels of radioactive isotopes accumulated in local seaweed, researchers have reported.

The study poses the possibility that small amounts of Fukushima radioactivity has entered the California coast's food web, but the California State University Long Beach marine sciences professor who co-wrote a new study said he does not know if there is a measurable detrimental effect.

The radioactive forms of cesium and iodine "get dispersed over a variety of organisms'' including fish, said Cal State Long Beach marine biology professor Steven L. Manley. "I would assume it's there" in the biomass of plants and animals off California's coast.

"It's not a good thing, but whether it actually has a measurable detrimental effect is beyond my expertise," he said in a news statement issued by the Long Beach State public affairs office.

The seaweed off Southern California was contaminated with short-lived radioisotopes a month after Japan’s Fukushima accident, based on tests of giant kelp from the ocean off Orange County and other locations. Detected was radioactive iodine at peak concentrations 250-fold higher than levels found in West Coast kelp before the nuclear accident, the Environmental Health News reported.

"Basically we saw it in all the California kelp blades we sampled,” Manley told EHN editor Marla Cone. She wrote: The radioactivity had no known effects on the giant kelp, or on fish and other marine life, and it was undetectable when the kelp was tested again a month later. Iodine 131 “has an eight-day half life so it’s pretty much all gone,” Manley said. “But this shows what happens half a world away does effect what happens here. I don’t think these levels are harmful but it’s better if we don’t have it at all.”

Writing in the scientific journal "Environmental Science & Technology," Manley and co-author said researchers measured a radioactive isotope of iodine in kelp within a month after massive radiation leaks were caused by the Japanese earthquake and tsunami.

Manley and Lowe theorize that the radioactive elements blew across the Pacific in winter storm fronts that lashed the California coast shortly after the Fukushima Daiichi reactors blew apart, in the weeks following the massive March 11, 2011 earthquake and tsunami. One particular strain of seaweed, Macrocystis pyrifera, is present in large canopies along shallow areas of the California coast. Radioactive rainfall was absorbed by the seaweed before the seawater had a chance to dilute it, the scientists said in their article.

Followup work showed varying amounts of low levels of radioactive cesium in seaweed from samples near UC Santa Barbara and UC Santa Cruz, the scientists said. No radioactivity was found in seaweed from Alaska. Manley noted that future research into cesium accumulation in kelp is needed, but the graduate programs that support such efforts are in jeopardy due to state budget cutbacks.

Last year, acting on a hunch, Manley began monitoring the kelp samples from Corona del Mar, Laguna Beach and Crystal Cove that were brought in for a different project by graduate student Danielle Burnett. But Cal State Long Beach's old radiation counter was not capable of identifying which particular isotopes were giving off electrons, Manley said.

The level of radioactivity in the Southern California seaweed was "probably not harmful because it was relatively low levels,'' said Manley. But "it may have affected certain fish that graze on the (seaweed) tissue, because fish have a thyroid system that utilizes iodine."

It may be present in California kelp to this day, said Manley. "We were limited in what our instrumentation allows us to do," he said. "The big question was, 'is another major isotope that came over in the cloud, cesium 137, present in the kelp, too?'"

—City News Service contributed to this report.