Effects of radionuclide contamination on leaf litter decomposition in the Chernobyl exclusion zone.
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.
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SERIS, Cadarache, Bât. 183, BP 3, 13115 St Paul-lez-Durance, France. Electronic address: jean-marc.bonzom@irsn.fr.
Jean-Marc
JM
Bonzom
Centre d'Ecologie Fonctionnelle et Evolutive (CEFE UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE), 1919 Route de Mende, F-34293 Montpellier, France.
Stephan
S
Hättenschwiler
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SERIS, Cadarache, Bât. 183, BP 3, 13115 St Paul-lez-Durance, France.
Catherine
C
Lecomte-Pradines
EcoLab, Université de Toulouse, CNRS, UPS, INPT, 118 Route de Narbonne, 31062 Toulouse cedex, France.
Eric
E
Chauvet
Chernobyl Center for Nuclear Safety, Radioactive Waste and Radioecology, International Radioecology Laboratory, 07100 Slavutych, Ukraine.
Sergey
S
Gaschak
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SERIS, Cadarache, Bât. 183, BP 3, 13115 St Paul-lez-Durance, France.
Karine
K
Beaugelin-Seiller
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SERIS, Cadarache, Bât. 183, BP 3, 13115 St Paul-lez-Durance, France.
Claire
C
Della-Vedova
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SERIS, Cadarache, Bât. 183, BP 3, 13115 St Paul-lez-Durance, France.
Nicolas
N
Dubourg
Chernobyl Center for Nuclear Safety, Radioactive Waste and Radioecology, International Radioecology Laboratory, 07100 Slavutych, Ukraine.
Andrey
A
Maksimenko
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SERIS, Cadarache, Bât. 183, BP 3, 13115 St Paul-lez-Durance, France.
Jacqueline
J
Garnier-Laplace
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-ENV/SERIS, Cadarache, Bât. 183, BP 3, 13115 St Paul-lez-Durance, France.
Christelle
C
Adam-Guillermin
D001673:Biodegradation, Environmental / Q000528:radiation effects*; D047852:Chernobyl Nuclear Accident; D065928:Forests; D018515:Plant Leaves; D011834:Radiation Monitoring; D012987:Soil / Q000737:chemistry; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D014197:Trees
D012987:Soil; D012990:Soil Pollutants, Radioactive
Decomposers; Dose rates; Ecosystem functioning; Ionizing radiation; Nuclear accident; Pollution