KelpWatch 2015 Monitoring: No Fukushima derived contamination May – June ’15

Bull Kelp, or Nereocystis luetkeana
Bull Kelp (Nereocystis luetkeana)

By Jay T. Cullen

The purpose of this diary is to report the most recent results of Kelp Watch 2015, a program dedicated to monitoring for Fukushima derived contamination along the Pacific Coast of North America.  New results from the fourth sampling period (May 4 through June 10 2015)  were released on Dec. 8, 2015 and can be found here. As with previously reported results here, here, here and here no radioactive isotopes from Fukushima were detected in kelp growing at sampling sites along our Pacific coast.  The absence of 134Cs in kelp suggests that ocean transport of Fukushima contamination had yet to reach persistently high enough levels in North American coastal water to bioaccumulate in kelp. The scientific community expects that levels of contamination rise in coastal waters as predicted by measurements and models in the coming year Kelp Watch 2015 will help to track the arrival of the plume in time and space.

A review of the goals and approach of Kelp Watch 2015 can be found at their project website.  Samples were collected May to June of 2015 from Juneau AK in the north down to Humboldt County CA in the south along the Pacific Coast .  KelpWatch 2015 is actively seeking out samples located near to San Francisco where the highest levels of Fukushima derived contamination were recently reported in offshore waters.

Full results for the fourth sampling period can be found here along with details about the goals and approach of Kelp Watch 2015.  Owing to its relatively short half life of ~2 years radioactive 134Cs serves as a useful tracer of Fukushima impact because it was released in significant quantities into the environment after the disaster in March 2011.  All other sources of the man made isotope have occurred far enough in the past that any 134Cs detected in the environment serves an unmistakable fingerprint of Fukushima impact.  Similar to previous work by this program all samples of kelp collected from the Pacific by Kelp Watch 2015 during the Spring of 2015 had no detectable (detection limit ~ 0.04 Bq kg-1 dry weight of kelp) levels of 134Cs indicating that isotopes from Fukushima are not significantly affecting radioisotope activities in these organisms to date.  This is despite the fact that Fukushima contaminated seawater has been detected periodically at the coast and most notably in Ucluelet BC where the first shoreline seawater sample with Fukushima contamination was collected on Feb. 19, 2015. The fact that the kelp is still free of 134Cs is likely related to the lack of persistent contact with Fukushima contamination owing to the dynamic nature of coastal currents, coastal upwelling of less contaminated water from depth, significant inputs of contamination free freshwater runoff or a combination of these factors given sampling location.

Continued monitoring of seawater and marine biota by projects like KelpWatch 2015 and InFORM will help to determine levels of Fukushima derived contamination along the North American coast and the corresponding risks to ocean and public health.

This post is the latest in a series dedicated to the public dissemination of information about the impacts of the Fukushima Dai-ichi disaster on the health of the North Pacific Ocean ecosystem and health of North American residents.

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