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Jellyfish radioisotope concentrations
[i]***137Cs activity concentrations were below the detection limit in all measured samples***[/i]
Nov. 2015


Radioactivity in three species of eastern Mediterranean jellyfish
Activity concentrations of 137Cs, 40K, 210Po, 210Pb, 234U and 238U were determined in umbrella and oral arms of three widely distributed jellyfish species; namely [i]Rhopilema nomadica Galil, 1990, Aurelia aurita Linne, 1758 and Aequorea forskalea Péron & Lesueur, 1810 collected from February 2011 to January 2012 in four sampling locations along the Syrian coast (Eastern Mediterranean Sea). The results have shown significant variations in radionuclides activity concentrations amongst the species. The average activity concentrations of 40K, 210Po, 210Pb, 234U and 238U in the umbrella of R. nomadica species were higher than the average activity concentrations in the umbrella of A. aurita species by about 3.2, 1.4, 1.8, 3.2 and 3.2 folds, and A. forskalea species by about 45.5, 15.4, 19, 7.4 and 7.6 folds, respectively. The average activity concentrations of 40K, 210Po, 210Pb, 234U and 238U in oral arms of R. nomadica species were higher than the average activity concentrations in oral arms of A. auritaspecies by about 3.8, 1.7, 1.9, 2.8 and 2.9 folds, respectively. 137Cs activity concentrations were below the detection limit in all measured samples. In addition, activity concentrations of 137Cs, 40K, 210Po, 210Pb, 234U and 238U were also determined in 44 surface seawater samples and the activity concentrations ranged between 10.6 and 11.9 Bq l−1 for 40K, 1.1 and 1.4 mBq l−1 for 210Po, 0.5 and 0.7 mBq l−1 for 210Pb, 40.8 and 44.5 mBq l−1 for 234U, and 36.9 and 38.4 mBq l−1 for 238U, while 137Cs activity concentrations were below the detection limit in all measured samples. Moreover, the umbrella and oral arms readily accumulated 40K, 210Po, 210Pb, 234U and 238U above ambient seawater levels in the sequence of 210Po > 210Pb > 4 K > 234U and 238U. Concentration ratio (CR) values were relatively high for 210Po and 210Pb and reached 103 and 102, respectively for the jellyfish R. nomadica species compared to A. aurita and A. forskalea species. Therefore, R. nomadica can be used as biomonitor for these two radionuclides in the Eastern Mediterranean Sea. However, the obtained data can be considered the first reported baseline values for radioactivity in jellyfish.

WHOI counterparts, Oregon State University recommendation for lack of 137 Cs in jellyfish? A "preferential food"
No mention of accumulation radioisotopes other than 137Cs, as outlined above.
Aug. 2017
Lack of Cesium Bioaccumulation in Gelatinous Marine Life in the Pacific Northwest Pelagic Food-Web

4 Conclusion
Gelatinous organisms seem to show remarkably low retention of radiocesium when compared to their competitors in the food web. Even with 24 h counting periods, several kilograms of sample tissue to concentrate and a relatively high-efficiency HPGe in a low-background environment, only one of all gelatinous samples collected exceeded the detection threshold for Cs-137. CRs were no higher than 4.4 and may very well have been 1.0 for some of the organisms collected. *** Jellyfish may thus serve as a preferential food source during periods of high levels of radiocesium contamination,*** and may experience more population growth due to lack of competition in the event contamination levels are sufficient to produce population level effects in the ecosystem. More work on radiosensitivity of jellyfish and the means by which they maintain such low levels of retention are needed in the future.

Jellyfish Thrive on Climate Change
To summarize: Jellyfish bioaccumulate numerous radioisotopes. Cesium137 is not one of them. "...readily accumulated 40K, 210Po, 210Pb, 234U and 238U above ambient seawater levels in the sequence of 210Po > 210Pb > 4 K > 234U and 238U. Concentration ratio (CR) values were relatively high for 210Po and 210Pb and reached 103 and 102, ..." The nuclear apologists use of this data? To recommend eating more jellyfish.

"...they do well in polluted areas because they need less oxygen than other sea life. Exploding jellyfish populations have swept into power plants across the world — including two nuclear plants in Scotland — shutting down parts of the power grid..."

Save the nukies; Eat more jellyfish!
interesting that there is a 3 to 45 fold concentration ratio of k-40 and none for cesium.   It is a scientific assumption that cesium is incorporated by the same cell process as potassium, but apparently not for jellyfish.   One thing to consider is that the cesium may be in the form of glass microspheres that are more or less the size of a cell.  This would change bioconcentration factors and perhaps measurement accuracy as well
we are healthy with background radiation but unhealthy with the same dose from fallout
It's probably worth looking into the amounts of Tritium that were added by Fukushima.  Tritium has devastating effects on marine life.  

"tritium produced measureable, dose dependent, and irreversible suppression of immune capacity in affected fish."
"It appeared that there was no threshold or significant dose-rate effect for either beta or gamma rays on germ cell survival, and that tritium beta rays were more effective than cesium-137 gamma rays in germ cell killing."

Tritium is of environmental importance because it is released from nuclear facilities in relatively large quantities and because it has a half-life of 12.26 y. Most of the tritium released into the atmosphere eventually reaches the aqueous environment where it is rapidly taken up by acquatic organisms. This paper reviews the current literature on tritium in the aquatic environment. Conclusions from the review, which covered algae, aquatic plants, invertebrates, fish, and food chain studies, were that aquatic organisms incorporate tritium into their tissue free water very rapidly and reach concentrations near that of the external medium. Incorporation of tritium from tritiated water into the organic matter of cells is at a slower rate than incorporation into the tissue free water. If organisms consume tritiated food, incorporation of tritium into the organic matter is faster and a higher tritium concentration is reached than when the organisms are exposed to only tritiated water. Incorporation of tritium bound to molecules into the organic matter depends on the chemical form of the 'carrier' molecule. No evidence was found that biomagnification of tritium occurs at higher trophic levels. Radiation doses to large populations of humans from tritium releases will most likely be from the consumption of contaminated water rather than contaminated aquatic food products.

Tritium isn't usually included in measurements of radionuclide contamination.  Most of the Tritium releases will eventually end up in the Ocean.  It isn't much of a danger to humans but even the smallest amount will harm aquatic life.
"The map is not the territory that it is a map of ... the word is not the thing being referred to."

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