Scientists working to measure radiation released after the April 2011 earthquake and tsunami in Japan have seen no signs of nuclear contamination along the West Coast of the United States. Researchers participating in the Kelp Watch 2014 project announced the news after analyzing the first batch of samples collected earlier this spring.
Kelp Watch 2014 uses coastal kelp beds as detectors of radioactive seawater arriving from Fukushima via the North Pacific Current. The project aims to gather kelp samples at 44 sites from Baja California to Alaska.
The effort is being led by Steven Manley, marine biology professor at California State University, Long Beach (CSULB), and Kai Vetter, head of applied nuclear physics at the Lawrence Berkeley National Laboratory (Berkeley Lab) and a nuclear engineering professor at the University of California, Berkeley.
“Our data does not show the presence of Fukushima radioisotopes in West Coast giant kelp or bull kelp,” Manley said. “These results should reassure the public that our coastline is safe, and that we are monitoring it for these materials. At the same time, these results provide us with a baseline for which we can compare samples gathered later in the year.”
The samples analyzed to date were gathered from as far north as Kodiak Island, Alaska, to Baja California. The 31 California collection sites include waters alongside several NRS reserves, including Younger Lagoon, Landels-Hill Big Creek, Kenneth S. Norris Rancho Marino, and Carpinteria Salt Marsh. Future sampling efforts will include the waters off Bodega Marine Reserve.
Don Canestro, director of the NRS’s Kenneth S. Norris Rancho Marino Reserve, participated in the first round of sampling and described the labor-intensive process. “You have to take out your boat, because they want kelp without any epiphytes like snails, so you can’t collect it on the beach. You’re hanging over the side of the boat to pull whole stipe of kelp on board. It takes about a 30 gallon garbage can of wet kelp to get the desired amount needed for the sample.”
Once brought back to shore, the kelp is allowed to drip dry. “You can’t just leave it in the can; you’ll wind up with a bucket full of slime,” Canestro says. Once relatively dry, the blades of the kelp are plucked off and driven to a lab, where they are dried further and ground for analysis.
“The samples of greatest concern were those from the north, Alaska to Washington State, where it is thought the radioactive water will first make contact with North America,” Manley said. “The telltale isotopic signature of Fukushima, Cs-134, was not seen, even at the incredibly low detection limits provided by Dr. Vetter’s group at the Berkeley Lab and UC Berkeley.”
Vetter plans to publish findings on naturally occurring radiation sources such as those associated with the decay of uranium and thorium. This information will help put into context the detection of any radioisotopes from Fukushima.
Although initiated as a California project, Kelp Watch 2014 has expanded to encompass the west coast of North America and beyond. “Because the Pacific Northwest may be ground zero for its arrival, we will be receiving monthly samples from the west and southern coastline of Vancouver Island (Canada),” Manley said. In addition, giant kelp samples from Chile, far from any potential influence from Fukushima, will serve as reference controls.
Information about the procedures and results, including the results of the first samples’ analyses, are available to the public at kelpwatch.berkeley.edu. The researchers will continually update the website for public viewing as more samples arrive and are analyzed. “One of the goals of Kelp Watch 2014 is to keep the public informed, to let them know we are on top of this event, and to document the amount of Fukushima radiation that enters our kelp forest ecosystem,” Manley said.
During the first phase of the project, samples were taken from 38 of the 44 sites originally identified, and the data being presented comes from an analysis of 28 of the 38 sample sites, most collected from Feb. 24 through March 14. The second of the three 2014 sampling periods is scheduled to begin in early July.
Sampling began in 2014 because scientists calculated that it would take roughly three years for ocean currents to deliver significant amounts of radiation across the Pacific.