puts it on par with young albacore and bluefin tuna in terms of trophic level, which
have CRs of 200+ [2, 4].
One implication of this result is that, at least with regards to food safety, dietary
jellyfish are likely to remain safe for consumption even in cases of substantial
contamination. Drinking water standards for Cs-137 are several orders of magnitude below those for most foods owing to the much larger quantities of water
consumed by a human. For example, the EPA in the US has a drinking water
standard of 7.4 Bq/L (approximately 7.4 Bq/kg) for Cs-137, whereas the FDAs
derived intervention level for Cs-137 in food products is 1,200 Bq/kg. Given the
CRs presented here even for the highest trophic positions of gelatinous organisms,
jellyfish should remain a relatively safe food product even when harvested in water
well of 100 times past the safe drinking water standards.
Another implication of these results is one that has been mirrored in other areas
of anthropogenic effects on marine ecosystems: jellyfish blooms. In the event of a
radiocesium release of a large enough magnitude to produce population level effects
in that ecosystem, the doses to gelatinous organisms can be expected to be tens to
hundreds of times lower than that to crustaceans, fish and even macroalgae.
Although no in-depth studies have been conducted on the radiosensitivity of
gelatinous organisms, there is nothing to suggest they would be especially
radiosensitive to offset this greatly decreased dose. Because of their extremely
simple immune system that lacks the an equivalent “weak-link” of bone-marrow,
and an intestine that is replaced directly by mitosis rather than the “weak-link” of
crypt cells, the general indication is that they would show at least moderate
radioresistance. One might expect, then, that ecosystem-affecting anthropogenic
radiocesium releases might lead to jellyfish blooms and increased competition with
forage fish much, much as been observed from anthropogenic eutrophication and
apoxia (albeit for a different set of sensitivity/resistance mismatches).
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.
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have CRs of 200+ [2, 4].
One implication of this result is that, at least with regards to food safety, dietary
jellyfish are likely to remain safe for consumption even in cases of substantial
contamination. Drinking water standards for Cs-137 are several orders of magnitude below those for most foods owing to the much larger quantities of water
consumed by a human. For example, the EPA in the US has a drinking water
standard of 7.4 Bq/L (approximately 7.4 Bq/kg) for Cs-137, whereas the FDAs
derived intervention level for Cs-137 in food products is 1,200 Bq/kg. Given the
CRs presented here even for the highest trophic positions of gelatinous organisms,
jellyfish should remain a relatively safe food product even when harvested in water
well of 100 times past the safe drinking water standards.
Another implication of these results is one that has been mirrored in other areas
of anthropogenic effects on marine ecosystems: jellyfish blooms. In the event of a
radiocesium release of a large enough magnitude to produce population level effects
in that ecosystem, the doses to gelatinous organisms can be expected to be tens to
hundreds of times lower than that to crustaceans, fish and even macroalgae.
Although no in-depth studies have been conducted on the radiosensitivity of
gelatinous organisms, there is nothing to suggest they would be especially
radiosensitive to offset this greatly decreased dose. Because of their extremely
simple immune system that lacks the an equivalent “weak-link” of bone-marrow,
and an intestine that is replaced directly by mitosis rather than the “weak-link” of
crypt cells, the general indication is that they would show at least moderate
radioresistance. One might expect, then, that ecosystem-affecting anthropogenic
radiocesium releases might lead to jellyfish blooms and increased competition with
forage fish much, much as been observed from anthropogenic eutrophication and
apoxia (albeit for a different set of sensitivity/resistance mismatches).
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.
314
D.R. Neville and K.A. Higley