Variability of stress biomarker expression in a model organism for terrestrial ecotoxicology-Enchytraeus albidus

Enchytraeid (Annelida, Oligochaeta) are ecologically relevant terrestrial organisms involved in the litter decomposition, bioturbation, nutrient cycling (Zhang et al, 2017), and the porosity and soil structure, etc. (Gomes et al, 2012). The enchytraeid are present in a wide range of ecosystems (Didden et al 2001) and come into contact with the different soil constitutants: the soil solution, the solid phase, and the gaseous phase (Didden et al, 2001), hence the importance to take them into account in the soil quality assessment. Moreover, anthropogenic pressures may alter the organism’s health and thus, affect the ecological functions assuring by enchytraeids. That is why the development of tools for soil quality assessment requires to understand the enchytraeid sensitivity to environmental factor variations. Many studies have shown the sensitivity of these organisms to different chemical contaminants in soils. Nevertheless, in most studies the soil used was a standard laboratory soil (Kuperman et al, 2006). The present study aims to analyze the natural variability of stress biomarker expression in an enchytraeid species exposed to 20 natural soils collected in different ecosystems: urban, forest, and agricultural. This makes it possible 1) to characterize the variability of biomarker expression, 2) to identify the soil edaphic parameters influencing the biomarker expression, and thus 3) to define the sensitivity of these tools for the soil chemical stress diagnosis. The species used for this study is Enchytraeus albidus, a model species for terrestrial ecotoxicity tests, with a short life cycle (42-days for the ecotoxicity test) (ISO 2004) and present in various ecosystems (Kasprzak, 1982, Rombke et al, 2002). They are easy to use for assessing toxic and chemical stress (Didden et al, 2001), reproduce rapidly, and can be maintained in a variety of substrates (Rombke et al, 2002). The experimental device is designed according to ISO 16387 norm (2014). The biomarkers measured during this study are life history traits (survival and reproduction) and energy reserves, the latter of which provides more detailed information on the organism’s health. In parallel, the pedo-edaphic parameters, enzymatic activities and metal contamination levels of the 20 soils are characterized. Finally, multifactorial statistical analysis of the data allow us to distinguish the predominant environmental parameters involved in the variation of stress biomarkers studied in E. albidus, and to establish the relevance of these biomarkers as tools for the soil quality assessment.