According to a study released this week by researchers at Cal State Long Beach, a wave of radioactivity traveled across the Pacific Ocean in the week after the 9.0 earthquake that struck Japan on March 11, 2011.
Researchers, who were working on a separate project mapping a different isotope, cesium 137, harvested the seaweed from three sites along Orange County at Corona del Mar, Laguna Beach and Crystal Cove in the week after the quake.
Those samples contained contained small amounts of iodine 131, as well as cesium 137.
The highest levels were found in Corona del Mar. Researchers said the levels were probably highest there because the kelp is also exposed to urban runoff.
Samples were also collected by marine biologists from UC Santa Barbara, UC Santa Cruz and the University of Alaska Southeast.
The California samples contained varying low levels of the isotope, while the Alaska samples contained none.
The levels, while most likely not harmful to humans, were significantly higher than measurements prior to the explosion and comparable to those found in British Columbia, Canada, and northern Washington state following the Chernobyl disaster in 1986, according to the study.
"Radioactivity is taken up by the kelp and anything that feeds on the kelp will be exposed to this also," study author Steven L. Manley said.
"Even though we detected low levels, it still got into the environment."
Manley said the study only measured the surface of the seaweed, meaning there could easily be twice to three times as much radioactive material in the ocean.
"It's not a good thing, but whether it actually has a measurable detrimental effect is beyond my expertise," Manley said.