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

Abstract

ABSTRACT Understanding the pathways of 137Cs transfer to spiders as generalist predators is useful to assess the long-term recycling of 137Cs 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 137Cs activity concentrations and stable carbon and nitrogen isotope ratio values (δ13C and δ15N). Across the locations, 137Cs was detected in all spiders, indicating that a significant fraction of the deposited 137Cs is still bioavailable. The geometric means of the transfer factor (Tag ) values were 1.3 × 10−3 m2 kg−1 and 0.8 × 10−3 m2 kg−1 for the spiders in the forest interior and along the river, respectively. There were no significant differences in the 137Cs activity concentration and Tag value between the locations. In contrast, the δ13C and δ15N for the spiders were significantly different between the locations, indicating different food resources of the spiders. The preliminary results indicate that the transfer of 137Cs to spiders can be a useful indicator of 137Cs recycling in forest ecosystems, but the transfer pathways remain difficult to identify because of high variability.