Radiation signs in California kelp. (Photo: YouTube/MrKJKat /Stock File/FIS)
Kelp off California coast still contains radiation from Japan
Tuesday, April 10, 2012, 00:50 (GMT + 9)
Radioactivity from Japan’s stricken Fukushima Daiichi nuclear power plant reached the North American west coast in just days after the 11 March 2011 earthquake and tsunami.
California State University, Long Beach (CSULB) marine biology professors Steven L Manley and Christopher G Lowe have examined kelp samples and determined that iodine 131 was present in California kelp more than a month after the tsunami, partly because rainstorms helped deposit the airborne contaminants into the ocean.
Their findings appear in an article, “Canopy-Forming Kelps as California’s Coastal Dosimeter: 131I from Damaged Japanese Reactor Measured in Macrocystis pyrifera,” in the online edition of the journal Environmental Science & Technology.
The team measured significant, although most likely non-harmful levels of radioactive iodine in the giant kelp Macrocystis pyrifera, which may have affected certain fish that eat it because fish have a thyroid system that utilizes iodine.
They do not, however, know whether cesium 137 was present in the kelp – and cesium 137 has a half-life of 30 years instead of eight days of iodine.
Manley found iodine in kelp blades from Orange County. He then had Lowe, director of the CSULB Shark Lab and an expert in marine fisheries, ask his graduate students to also obtain kelp samples.
California samples contained varying low levels of iodine 131, but a closely related kelp in Alaska, Macrocystis integrifolia, had none, possibly because it could have decayed away and it was not detected, or because the plume never did get up there in a high enough concentration, Manley explained.
“Even though we detected low levels, it still got into the environment and we don’t know anything about the other radioisotopes like cesium 137, which stays around much longer than iodine. In fact, the values that we reported for iodine probably underestimate what was probably in there. It could be two to three times more because we were just sampling the surface tissue; the biomass estimates were based on canopy tissue and a lot of kelp biomass is underneath,” he added.
Manley hopes to engage CSU’s Coastal Affairs, Science and Technology (COAST) consortium of all CSU campus marine biology programmes in follow-up studies, to organize a standardized monitoring system to get tissue and background samples every few months so that if another event occurs, the team will have some baseline information.
By Natalia Real