A Cal State Long Beach professor authored a study on radioactive kelp, which was found along the coast of Southern California last year.
The radioactive material was released into the water and atmosphere as a result of the Fukushima accident.
As professor Steven L. Manley watched the damage from Fukushima on television, he was reminded of a study done in 1986 after the Chernobyl disaster, where radioactive Iodine 131 was found in samples of intertidal seaweed along the West Coast.
“I thought, if I was doing this … I would choose Macrocystis pyrifera, giant kelp, because it forms these large canopies and it’s not in the intertidal so there’s not tidal influence,” Manley said.
Manley added that kelp is like a “sponge for iodine” because they concentrate iodine 10,000-fold, so for every one molecule in the water, there would be 10,000 in the kelp’s tissue.
During accidents like Fukushima, one of the major radioisotopes released are Iodine 131, which decays very quickly due to its eight-day half-life.
By measuring the kinetics of the decay, Manley was able to determine which radioisotopes were released.
CSULB graduate student Danielle Burnett, who was working on another study involving giant kelp, was asked to bring samples of kelp blades from her study sites for the study.
The kelp was dried and pulverized, and was analyzed for more than 24 hours due to its low levels. It then took about nine days to analyze the data.
After collecting all the information on the giant kelp samples, Manley worked with Lowe to come up with sampling protocols and call other people in the region.
Samples were collected from Palos Verdes, Santa Barbara and Monterey Bay.
Students from Lowe’s class also contributed to the study by collecting tissue from other locations.
“This project couldn’t have been successful without a master’s program at CSULB,” Manley said. “Because without those students, we wouldn’t have been able to do this.”
The two professors and students began collecting samples last April and made periodic measurements on the samples to see the progress of decay. The whole study took around two to three months.
The study concluded that there is a very low level of radiation in the kelp, so it would most likely not be harmful to people.
“If you were swimming in the canopy, it probably wouldn’t be harmful; it has less radiation than a dental X-ray,” Manley said. “The amount of radioactivity due to Iodine 131 was less than twice the background level.”
There are many natural radioactive isotopes that the kelp soaks up, which create the background level. The amount of radioactivity recorded was less than double the background level.
Manley and Lowe also observed that there were radioisotopes of Cesium present on the kelp.
Seeing that Cesium 137 has a half-life of 30 years, the Cesium would still be present if the kelp had taken it up.
“We know very little about how Cesium gets transferred from one organism to another, and we still have the samples for Cesium isotopes so … we hope to sit down and pursue this more,” Manley said.