Kelp Watch 2014 Update: No Fukushima Derived Radiocesium Detected in West Coast Kelp

By Jay T. Cullen

Dan Harrison, Executive Director of InFORM partner organization Raincoast Education Society ( sampling kelp for Kelp Watch 2014 in Tofino, BC Canada.

The most recent results of Kelp Watch 2014 , a program dedicated to monitoring for the presence of Fukushima sourced radionuclides off our Pacific Coast, are reported in this post. This post is the latest contribution to a series dedicated to the dissemination of information about the impacts of the Fukushima Dai-ichi disaster on the North Pacific Ocean ecosystem and on North American public health. New results from the second sampling period (June to August 2014) of Kelp Watch 2014 were just released and can be found here. As with previously reported results here and here no radioactive isotopes from Fukushima were detected in kelp growing at sampling sites spread across the eastern Pacific coast. However, significant quantities of the short lived radioisotope 131-Iodine (half life ~8 days) continued to be found in Los Angeles County and San Diego in southern California. Rather than being transported across the Pacific these isotopes were likely released locally in waste water that carries significant 131-I because of its application in nuclear medicine to treat thyroid maladies. The absence of 134-Cs in kelp suggest that ocean transport of Fukushima contamination has yet to reach North American coastal water.

Kelp Watch 2014 is a joint initiative between Dr. Steven Manley (Department of Biological Sciences, California State University- Long Beach) and Dr. Kai Vetter (UC Berkeley and Lawrence Berkeley National Laboratory). The program involves the analysis of kelp samples collected by citizen-scientists along the Pacific coast for Fukushima derived radioisotopes. Because of their sedentary existences and propensity to concentrate isotopes in their tissues kelp are useful sentinel organisms with which to monitor the timing and extent of the Fukushima impacted plume of seawater as it progressively affects more of the North American west coast.

Samples were collected June to August of this year at various sampling locations along the coast with some kelp obtained from Chile and Tasmania (where little Fukushima impact is expected) to serve as reference locations.

Stations where samples of kelp were obtained for Kelp Watch 2014
Full results for the second sampling period can be found here along with details about the goals and approach of Kelp Watch 2014.

Because of its relatively short half life of ~2 years radioactive 134-Cs serves as a useful tracer of Fukushima impact as it was released in significant quantities, with many other isotopes, into the environment after the disaster in March 2011. All other legacy sources of the human produced isotope have occurred far enough in the past that any 134-Cs present in the environment faithfully reflects release from Fukushima. Similar to previous work by this program all samples of kelp collected from the Pacific by Kelp Watch 2014 in June to August of this year had no detectable (detection limit ~ 0.04 Bq/kg dry weight of kelp) levels of 134-Cs suggesting that isotopes from Fukushima are not significantly affecting radioisotope activities in these organisms to date.

The authors summarize findings about 134-Cs and its longer lived cousin 137-Cs (half life ~30 yr) as follows:

Cesium-137 was detected in all West Coast samples at very low levels. This isotope is still detectable in the marine environment due to above-ground nuclear weapons testing that took place mostly in the 1950s and 1960s. The very low limits set on the shorter-lived Cesium-134 mean that the Cs-137 cannot be directly tied to the Fukushima releases and is more likely due to these “legacy” sources.

Significant Iodine-131 (131-I, half life ~8 days), which can represent a significant radiological health risk given its propensity to concentrate in the thyroid gland and induce cancer, activities continue to be detected (up to 251 Bq/kg at Long Beach CA) in southern California kelp samples. This 131-I is not likely from Fukushima given that ocean transport is quite slow relative to 131-I decay. Kelp Watch 2014 attributes the presence of 131-I to local sources which are likely waste water inputs to the coastal ocean that contains 131-I from nuclear medical applications in hospitals and clinics in the area.

Ongoing monitoring of seawater and marine organism activity concentrations of radioisotopes from Fukushima will help to determine the likely impacts on the ecosystem and public health along North America’s Pacific coast resulting from the disaster. As always, I will report new results as they are made available and we look forward to more work from this quality monitoring program.


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