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, 12 (1), e0171133
eCollection

Radiocesium Transfer in Forest Insect Communities After the Fukushima Dai-ichi Nuclear Power Plant Accident

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Radiocesium Transfer in Forest Insect Communities After the Fukushima Dai-ichi Nuclear Power Plant Accident

Yumiko Ishii et al. PLoS One.

Abstract

To understand radiocesium transfer in the forest insect food web, we investigated the activity concentrations of radiocesium in forest insects in the Fukushima and Ibaraki Prefectures approximately 1.5-2.5 years after the Fukushima Dai-ichi Nuclear Power Plant. We analyzed 34 species of insects sampled from 4 orders and 4 feeding functional groups (herbivore, carnivore, omnivore, and detritivore) from three sites in each prefecture. 137Cs activity concentrations were lowest in herbivorous species and were especially high in detritivorous and omnivorous species that feed on forest litter and fungi. Radiocesium activity concentrations in any given species reflected the degree of contamination of that species' primary food sources since radiocesium activity concentrations were found to be the lowest in leaves and grass and the highest in litter, bark, and fungi. This study confirmed that litter and other highly contaminated forest components such as fungi, decaying wood, bryophytes, and lichens serve as sources of 137Cs transfer into the forest insect community.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Locations of Study Sites in the Fukushima and Ibaraki Prefectures.
Left panel shows 137Cs deposition (Bq m−2) in eastern Japan (The map was generated from the Distribution Map of Radiation Dose by MEXT, Japan, http://ramap.jaea.go.jp/map/). Right panels are the aerial photographs provided by the Geographical Survey Institute (http://maps.gsi.go.jp/development/ichiran.html), with red squares showing locations of study sites in the Ibaraki Prefecture (A, B, C) and Fukushima Prefecture (D, E, F).
Fig 2
Fig 2. 137Cs activity concentrations in Forest Components and Insects.
137Cs activity concentrations are shown for study sites in Fukushima (upper panel) and Ibaraki (lower panel) in 2012. Litter and leaf samples are shown separately for Japanese cedar forests (Litter_e and Leaf_e) and deciduous forests (Litter_d and Leaf_d). Dark horizontal lines represent the mean, with the box representing the 25th and 75th percentiles, the whiskers the 5th and 95th percentiles, and dots indicating outliers.
Fig 3
Fig 3. 137Cs Activity Concentrations in Insect Feeding Functional Groups.
137Cs activity concentrations of insect species are shown in relation to the 137Cs activity concentrations in litter at the site. Colors indicate the functional feeding group to which species belongs: green, herbivore; yellow, omnivore; gray, carnivore; red, detritivore. Symbols indicate the sampling area: circle, Fukushima; triangle, Ibaraki.
Fig 4
Fig 4. Concentration Ratio of 137Cs in Sampled Insect Species.
CRs were calculated as Bq kg−1 insect dry weight/(Bq kg−1 litter dry weight. Species are grouped by the orders to which they belong (Coleoptera, Hemiptera, Lepdoptera, Orthoptera) with lines separating the orders. Colors indicate the functional feeding group to which species belongs: green, herbivore; yellow, omnivore, gray, carnivore; red, detritivore. Symbols indicate the sampling area: circle, Fukushima; triangle, Ibaraki.

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Substances

Grant support

This work was financially supported by the research program on Disaster Environment, an internal budget of National Institute for Environmental Studies. The internal budget was originally issued by the Ministry of Environment, Japan (http://www.nies.go.jp/shinsai/index-e.html).
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