Web-building spider Nephila clavata (Nephilidae: Arachnida) can represent 137 Cs contamination of arthropod communities and bioavailable 137 Cs in forest soils at Fukushima, Japan.

Large areas of Fukushima's forests were contaminated with radiocesium(Cs-137) after the Fukushima Dai-ichi Nuclear Power Plant accident. Most of the contaminated forests have not been decontaminated, and bioavailable Cs-137 is likely to circulate within the forest environment's food web. Nephila clavata (Nephilidae: Arachnida) is a top predator in the forest arthropod community, and this web-building spider potentially consumes many arthropod species presented in the grazing and detrital food chains. We tested whether Cs-137 in the spider could serve as a proxy for Cs-137 contamination of these arthropod communities. We also examined whether N. clavata could serve as a proxy for soil bioavailable Cs-137. Nephila clavata was similarly or more contaminated with Cs-137 compared with lower-trophic-level arthropods such as herbivores and other predators at the same trophic level. Thus, the Cs-137 activity of N. clavata could represent the extent to which the arthropod community was contaminated with Cs-137. Data from nine Cs-137-contaminated sites in Fukushima showed a significant positive correlation between soil bioavailable Cs-137 and N. clavata's Cs-137 activity05 but the coefficient of determination was only moderate (R-2 = 0.43), suggesting that N. clavata is only a weak proxy of soil bioavailable Cs-137. Our results also showed that the bioavailable fraction of Cs-137 in Fukushima was strongly correlated with the total inventory and that the K and Na contents of the soil determined the soil-to-spider transfer factor for Cs-137 and the Cs-137 activity in N. clavata, respectively. These results improve our understanding of Cs-137 transfer from the soil to arthropod species. (C) 2019 Elsevier B.V. All rights reserved.