Effects of radionuclide contamination on leaf litter decomposition in the Chernobyl exclusion zone

Abstract

The effects of radioactive contamination on ecosystem processes such as litter decomposition remain largely unknown. Because radionuclides accumulated in soil and plant biomass can be harmful for organisms, the functioning of ecosystems may be altered by radioactive contamination. Here, we tested the hypothesis that decomposition is impaired by increasing levels of radioactivity in the environment by exposing uncontaminated leaf litter from silver birch and black alder at (i) eleven distant forest sites differing in ambient radiation levels (0.22-15μGyh(-1)) and (ii) along a short distance gradient of radioactive contamination (1.2-29μGyh(-1)) within a single forest in the Chernobyl exclusion zone. In addition to measuring ambient external dose rates, we estimated the average total dose rates (ATDRs) absorbed by decomposers for an accurate estimate of dose-induced ecological consequences of radioactive pollution. Taking into account potential confounding factors (soil pH, moisture, texture, and organic carbon content), the results from the eleven distant forest sites, and from the single forest, showed increased litter mass loss with increasing ATDRs from 0.3 to 150μGyh(-1). This unexpected result may be due to (i) overcompensation of decomposer organisms exposed to radionuclides leading to a higher decomposer abundance (hormetic effect), and/or (ii) from preferred feeding by decomposers on the uncontaminated leaf litter used for our experiment compared to locally produced, contaminated leaf litter. Our data indicate that radio-contamination of forest ecosystems over more than two decades does not necessarily have detrimental effects on organic matter decay. However, further studies are needed to unravel the underlying mechanisms of the results reported here, in order to draw firmer conclusions on how radio-contamination affects decomposition and associated ecosystem processes.

Adverse effects induced by chronic gamma irradiation in progeny of adult fish not affecting parental reproductive performance

“…In the present study, adult zebrafish were exposed to 4 dose rates (0,0.5,5,137 Cs gamma radiation) over 10 d. The dose rates were higher than those in "hot spots" measured in freshwater ecosystems around Chernobyl, Pryp'yat', Ukraine (<0.2 mGy h -1 ; Lecomte-Pradines et al 2014;Bonzom et al 2016;Fuller et al 2018;Lerebours et al 2018). Reproduction was initiated, and the progeny were then exposed or not to the same dose rates over 96 to 120 h. The objectives of the present study were to evaluate 1) adult reproductive performance, 2) the effects in the progeny of irradiated parents, and 3) the responses at the molecular and organism levels.…”

Skin and gut microbiomes of a wild mammal respond to different environmental cues

“…Forest litter accumulates in contaminated areas (including the Red Forest) within the CEZ [ 79 ], potentially increasing available microbial niche space from which bank voles SK microbiome is sourced, given that bank voles inhabit burrows and move about the leaf litter. Curiously, accumulation of forest litter in contaminated areas within the CEZ implies impaired function of microbial decomposers and/or soil invertebrates [ 79 ], but see also [ 80 ]. As such, high SK microbiome diversity within the CEZ (and by implication high microbial diversity in the surrounding environment) does not appear to be associated with a healthy ecosystem function [ 81 ].…”

Towards solving a scientific controversy – The effects of ionising radiation on the environment

“…Many studies have reported no substantial effects of radiation on wildlife in the Chernobyl Exclusion Zone (CEZ) (e.g. Chesser and Baker, 2006;Deryabina et al, 2015;Murphy et al, 2011;Bonzom et al, 2016). Conversely, others report significant impacts of radiation on wildlife at extremely low dose rates.…”