Transfer of 137Cs to web-building spiders, Nephila clavata, and its pathways: a preliminary study using stable carbon and nitrogen isotope analyses

Understanding the pathways of Cs-137 transfer to spiders as generalist predators is useful to assess the long-term recycling of Cs-137 through the food chain in forest ecosystems. Approximately 6.5 years after the Fukushima Dai-ichi Nuclear Power Plant accident, we collected spider samples at two different habitats (in a forest interior and along a river) in a forest and determined their Cs-137 activity concentrations and stable carbon and nitrogen isotope ratio values (delta C-13 and delta N-15). Across the locations, Cs-137 was detected in all spiders, indicating that a significant fraction of the deposited Cs-137 is still bioavailable. The geometric means of the transfer factor (T-ag ) values were 1.3 x 10(-3) m(2) kg(-1) and 0.8 x 10(-3) m(2) kg(-1) for the spiders in the forest interior and along the river, respectively. There were no significant differences in the Cs-137 activity concentration and T-ag value between the locations. In contrast, the delta C-13 and delta N-15 for the spiders were significantly different between the locations, indicating different food resources of the spiders. The preliminary results indicate that the transfer of Cs-137 to spiders can be a useful indicator of Cs-137 recycling in forest ecosystems, but the transfer pathways remain difficult to identify because of high variability.

Automated summary

Understanding the transfer pathways of Cs-137 to spiders, as generalist predators in forest ecosystems, is beneficial for assessing long-term recycling of Cs-137 through the food chain. Results showed Cs-137 was detected in all spiders at different habitats, indicating its bioavailability, while differences in carbon and nitrogen isotope ratios suggested varying food resources for spiders between locations. Further research is needed to clarify the transfer pathways due to high variability observed.