Different cesium-137 transfers to forest and stream ecosystems

•Detrital-based food web structure was observed in both forest and stream ecosystems.•The 137Cs concentration in litter was 4 times lower in stream than in forest.•The difference of 137Cs concentration in litter reflected in animal contamination.•137Cs leaching from litter decreases contamination level of stream food web.

Understanding the mechanisms of 137Cs movement across different ecosystems is crucial for projecting the environmental impact and management of nuclear contamination events. Here, we report differential movement of 137Cs in adjacent forest and stream ecosystems. The food webs of the forest and stream ecosystems in our study were similar, in that they were both dominated by detrital-based food webs and the basal energy source was terrestrial litter. However, the concentration of 137Cs in stream litter was significantly lower than in forest litter, the result of 137Cs leaching from litter in stream water. The difference in 137Cs concentrations between the two types of litter was reflected in the 137Cs concentrations in the animal community. While the importance of 137Cs fallout and the associated transfer to food webs has been well studied, research has been primarily limited to cases in a single ecosystem. Our results indicate that there are differences in the flow of 137Cs through terrestrial and aquatic ecosystems, and that 137Cs concentrations are reduced in both basal food resources and higher trophic animals in aquatic systems, where primary production is subsidized by a neighboring terrestrial ecosystem.