Radiological dose reconstruction for birds reconciles outcomes of Fukushima with knowledge of dose-effect relationships.

Jacqueline Garnier-Laplace,Timothy A Mousseau,Claire Della-Vedova,Karine Beaugelin-Seiller,Anders Pape Møller,Jean-Michel Métivier,Christian Ritz

doi:10.1038/srep16594

Abstract

We reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011–2014. Substituting the ambient dose rate measured at the census points (from 0.16 to 31 μGy h−1) with the dose rate reconstructed for adult birds of each species (from 0.3 to 97 μGy h−1), we confirmed that the overall bird abundance at Fukushima decreased with increasing total doses. This relationship was directly consistent with exposure levels found in the literature to induce physiological disturbances in birds. Among the 57 species constituting the observed bird community, we found that 90% were likely chronically exposed at a dose rate that could potentially affect their reproductive success. We quantified a loss of 22.6% of the total number of individuals per increment of one unit log10-tansformed total dose (in Gy), over the four-year post-accident period in the explored area. We estimated that a total dose of 0.55 Gy reduced by 50% the total number of birds in the study area over 2011–2014. The data also suggest a significant positive relationship between total dose and species diversity.

Highlights

We reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011–2014
Whatever year, where ambient dose rate varied by two orders of magnitude among sites, variation in absorbed dose rates among species and among sites varied by two orders of magnitude, the minimum value being estimated for Anas poecilorhyncha and the maximum for Phasianus colchicus and Eophona personata
In this study, substituting the ambient dose rate measured at the census point by the transformed dose variable using radiological dose rate reconstructed for adult birds of each species, we confirmed that the overall abundance of birds at Fukushima during 2011–2014 decreased with increasing absorbed doses (Fig. 3a)

Summary

Introduction

We reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011–2014. 400 sampling points (in 2011, 300 points) in areas within and outside the 20-km exclusion zone were visited annually to observe abundance and diversity of birds and other organisms, as well as their reproductive state; a number of environmental variables including ambient radiation level at the exact census points were recorded. In total this database contains information for 1500 point censuses (300 identical points from 2011 to 2014 with an additional 100 more points from 2012 to 2014). These differences between Chernobyl and Fukushima may reflect differences in duration of exposure, differences in radioactive isotopes still being present in the radioactive deposits at the census periods, and differences in potential accumulation of mutations since sampled individuals are offspring from a much smaller number of generations in Fukushima than in Chernobyl[7,13]

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Results

Conclusion