# Earthworms' bioturbation under contrasting conditions of ionizing radiation and soil humidity

Franck Gilbert, Yvan Capowiez, Olivier Armant, Nicolas Dubourg, Magali Floriani, J Goussopoulos, Stephan Hättenschwiler, Patrick Laloi, Sylvain Lamothe, Jean-Marc Bonzom

<figure><img src="image_1.png" /></figure>

► To cite this version:

Franck Gilbert, Yvan Capowiez, Olivier Armant, Nicolas Dubourg, Magali Floriani, et al. Earthworms' bioturbation under contrasting conditions of ionizing radiation and soil humidity. British Ecological Society Annual Meeting 2022, Dec 2022, Edimbourg, United Kingdom. . hal-04174936

HAL Id: hal-04174936

https://hal.science/hal-04174936

Submitted on 1 Aug 2023

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

Public Domain
# EARTHWORMS' BIOTURBATION UNDER CONTRASTING CONDITIONS OF IONIZING RADIATION AND SOIL HUMIDITY

Franck Gilbert¹,², Yvan Capowiez², Olivier Armant³, Nicolas Dubourg³, Magali Floriani³, Juliette Goussopoulos², Stephan Hättenschwiler⁴, Patrick Laloi³, Sylvain Lamothe¹ & Jean-Marc Bonzom³

θ: franck.gilbert@univ-tlse3.fr

## THE IRRASOIL PROJECT

There are still many uncertainties that contribute to **persisting controversy on the ecological effects of nuclear pollution**, which are limiting the implementation of environmental protection criteria. The main objective of the IRRASOIL project is to **investigate the effects of ionizing radiation on soil communities and associated functional processes (bioturbation, leaf litter decomposition, nutrient recycling, carbon flux) in interaction with predicted climate change**. More specifically, using a combined approach of **laboratory experiments under controlled conditions** (IRSN Micado'Lab irradiation platform) and **field experiments (Fukushima prefecture, Japan)**, this project aims studying how different functional groups of the soil macrofauna community, such as earthworms (endofauna) and litter layer-dwelling macrofauna (epifauna) interactively affect processes under such combined stresses. **The preliminary results presented here are issued from a first laboratory bioturbation experiment.**

<figure><img src="image_2.png" /></figure>

Laboratoire
écologie fonctionnelle
et environnement

<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

CENTRE D'ECOLOGIE
FONCTIONNELLE
& EVOLUTIVE

<figure><img src="image_6.png" /><figcaption>Fig. 1. Soil columns and their different experimental conditions.</figcaption></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

One hundred and twenty two 20-cm high soil columns (diam.: 16 cm) were built from natural soil (sieving, reconstruction including the addition of **fluorescent particulate tracers**) and then exposed to different experimental conditions within different climatic chambers (Fig. 1). **After 90 days of experimentation**, all the soil columns were recovered and bioturbation activity was quantified using complementary **X-ray tomography and fluorescent particulate tracer methods** [2].

Not surprisingly, no tracer movement was detected in the control soils. In the "epifauna" soils, if the surface organisms moved slightly downwards in the soil [what was not detected by x-ray tomography], it was not deep enough to reach either of the tracer layers placed at 4-cm and 10-cm depth, respectively (data not shown).

In presence of endofauna, results showed **no global effect of humidity change** on both the total macroporosity production and the transfer of tracers by earthworms (A. nocturna and A. caliginiosa) within soils (Figs 2C left & 2D left). On the other hand, the **macroporosity production** tented to **decrease with increasing applied ionizing radiation dose rate** (Fig. 2C right). Partial results of tracers displacement (only three on five replicates analysed so far) also indicated **significant differences** as a function of the irradiation dose, but without any clear trend (Fig. 2D right).

These preliminary results need to be completed and analysed more precisely, especially in order to:

- allow deconvolution of the specific "radiation dose" and the "moisture" effects;

- discriminate the gallery networks constructed by the two earthworm species;

- compare the X-ray tomography and particulate tracers results;

- conclude whether or not a reduction in soil moisture and the application of an ionizing stress had any effect on the processes studied.

<figure><img src="image_9.png" /><figcaption>Fig. 2. Examples of a burrow system produced by endofauna (A) and of a vertical distribution of tracers in the soils around the deposition layer (B) in the experimental soil cores, after 90 days. Mean percentage of total macroporosity volume created by earthworms within the soils columns (C) and computed particle displacement coefficient (PDC; [2]) (D), in the different experimental conditions. For a better poster reading, only the results obtained with pink tracers initially deposited at 4-cm depth are presented here.</figcaption></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /></figure>