The movement of the radioactive cesium in the food chain by the trophic levels of arthropod

The Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant accident occurred on March 11, 2011 and released large amounts of radioactive materials into the environment. Those radioactive materials were deposited on the soil surface and circulated in the ecosystem after the accident. The movement of Cs is highly affected by the food chain circulation in the ecosystem from a long-term perspective. Therefore, in order to observe the Cs movement in the food chain, we investigated the Cs concentration in arthropods, including insects. In this research, we collected three dominant arthropods in Fukushima: the Japanese grasshopper (Oxya yezoensis), the Emma mole cricket (Teleogryllus emma) and the Joro spider (Nephila clavata). These arthropods can be classified into three trophic levels in the food chain: herbivorous for the grasshopper, omnivorous for the field cricket, and carnivorous for the web spider. Then we observed the temporal changes of Cs concentrations in the trophic levels of the arthropods from 2012 to 2014. The results suggest that the arthropods in higher trophic levels accumulate Cs in higher concentrations than that of the arthropods in lower trophic levels. (author)