# Selecting Bioassay Test Species at the Screening Level of Soil Ecological Risk Assessments
###### Abstract  
For site-specific soil ecological risk assessments (SERAs), an integrated chemical, ecotoxicological, and ecological analysis needs to be performed. The SERA guidelines of international institutions and countries recommend that a SERA be initiated at the screening level to save time and social economic cost; however, they provide no unified test species for this screening level. This study performed SERAs for field soils and confirmed the importance of selecting bioassay test species that reflect the ecotoxicity of field soils at the screening level. To confirm test species that reflect the ecological risk of field soils, correlation analysis was performed on the results of each bioassay with the integrated ecotoxicological risk index (EtoxRI). Our results showed that soil algae, nematodes, and plants were the most representative species in soil assays, with high correlation coefficients with EtoxRI. The results imply the importance of selecting test species that represent ecological risk for the screening level of SERAs. Based on these findings, when using SERAs, species sensitivity, ecological relevance, and economic aspects should be considered when selecting the bioassay test species.  
site specific; soil ecological risk assessment; test species; ecological risk index Received: 25 March 20 Each country and institution recommends lists of bioassays for the ecotoxicological analysis of SERAs by level; however, no unified test species for this screening level has been proposed. Uncertainties in actual ecological risk (including under- and overestimation) arise when bioassays for this screening level are performed by selecting species based only on cost-effectiveness [10; 11]. [PERSON] et al. [1] suggest that all aspects, such as reproducibility, sensitivity, economics, applicability, and ecological relevance, should be considered when selecting species for bioassays. Although some previous studies have considered reproducibility, economic feasibility, and applicability, most have ranked sensitivity and ecological relevance as the least important features. In soil toxicology, earthworms and springtails are commonly used; however, various other test species have been proposed, and improved understanding of biodiversity and suitability of species is a research focus [3; 12; 13]. However, to the best of our knowledge, few studies have estimated the suitability of test species for ecotoxicity tests in site-specific SERAs. [PERSON] et al. [2] evaluated the suitability of bioassays by deriving the sensitivity of bioassays in ERA and considering cost-effectiveness; however, the test duration of the bioassays that they compared was too long to be used as a tool at the screening level (with a minimum of 14 days and a maximum of 56 days). Therefore, it is necessary to consider which species are more suitable as test species for the screening level of bioassays for triad methods.  
Therefore, the aim of this study was to find test species for bioassays that are suitable at the screening level of SERAs. We conducted chemical and ecotoxicological analyses using field soil contaminated by heavy metals. The total concentrations of heavy metals in the soils were measured in the chemical assessment, and the ecotoxicological assessment was performed using six soil species. The test duration and endpoints of bioassays were minimized to ensure cost-effectiveness for the screening level of SERAs. In addition, we estimated the EtoxRI by integrating the results of all bioassays and analyzed the correlations with each bioassay to confirm the test species that best represent ecotoxicity at the screening level of SERAs. The appropriate reflection of ecotoxicity in soils will optimize screening in ecological risk assessments.