# Soil Hg Contamination Impact on Earthworms'
## 3 Results
### Beta Diversity in Earthworm, Cast and Soil (Experiment 1)

Table 3: Statistical differences (ANOVA) in bacterial and fungal beta-diversity between Hg treatments and among sample types in experiment 1 and between Hg treatments and among earthworm gut parts in experiment 2. DF = Degrees of freedom. The bacterial community in the Hg-treated earthworm samples was dominated by Anarolineae (Chloroflexi, 9.5%), Alphaproteobacteria (8.7%), Actinobacteria (7.8%), Acidobacteria-6 (7.4%), Betaproteobacteria (7.4%), Planctomycetia (6.8%), Gammaproteobacteria (5.8%), and Deltaproteobacteria (5.2%). The relative abundance of the Mollicutes (phylum Firmicutes), which dominated (60.8%) the bacterial community in the uncontaminated control pots, decreased drastically in the Hg-contaminated treatment (Figure 4). Moreover, OTUs from the Mollicutes class were among the most negatively affected by the Hg-contaminated soil treatment when log\({}_{2}\)-fold changes in OTU read abundances were assessed (Figure 5). Other relatively abundant OTUs negatively affected by the Hg-contaminated soil layer included Gammaproteobacteriaabacteria (Aeronadeceae and Shewanella sp. ), Flavobacteria (Flavobacterium sp.) and Verrucomicrobiae (Verminebacter sp.). However, these taxonomic classes also included OTUs that significantly increased in the Hg-contaminated treatment compared to the control (Figure 5). Hg-tolerant OTUs (i.e., those with a significantly increased abundance in the Hg-contaminated treatment) were not particularly abundant and were spread over various phyla and classes, with Pedosphaerae, Oputae, Anaerobic, Acidobacteria-6, Gemm-1, Phycisphaerae, and Nitrospira being the most positively affected (Figure 5). Figure 4: Relative abundance of bacterial (**A**) and fungal (**B**) phyla and classes across the treatments (Hg = Hg-contaminated, \(\mathrm{ctrl}\) = uncontaminated control) and the sample types (soil, earthworm and cast) in experiment 1. In the cast samples, the bacterial community of both Hg treatments was dominated by Flavobacteria (phylum Bacteroidetes, 41% of Hg-contaminated samples), Gammaproteobacteria (Proteobacteria, 30%) and Verrucomicrobiae (Verrucomicrobia, 9.3%; Figure 4). Interestingly, abundant Aeromonadaceae (Gammaproteobacteria) and Flavobacterium sp. (Flavobacteria) OTUs, which were negatively affected by the Hg treatment in the earthworm samples, increased significantly in the cast samples. Besides, most of the OTUs from the Bacteroidetes phylum increased significantly in the Hg-treated cast samples, whereas they were negatively impacted by Hg in the earthworm samples (Figure 5). The bacterial community diversity in the soil samples did not vary between Hg treatments and was dominated by Mollicutes, Gammaproteobacteria and Flavobacteria (Figure 4). The fungal community in the earthworm, cast and soil samples in both Hg treatments was dominated by OTUs from the Hypocreomyctidae, Pleosporales, Pezzales, Leotiomycetes, Agaromyceset and Trichospor classes (Figure 4). The biggest change in the relative abundance of the dominant fungal classes between the control and the Hg-contaminated soil treatments were observed for the Agaromycetes (\(-\)12.2%), Hypocreomyctidae (\(+\)8.8%) and Pleosporales (\(+\)8.0%) in the earthworm samples and for the Pezzales (\(-\)14.4%), Trichosporon (\(-\)12.5%), Hypocreomyctidae (\(+\)10.1%), Pleosporales (\(+\)6.9%), and the Leotiomycetes (\(-\)6.0%) in the cast samples. In the cast samples, these changes were supported by a significant increase in abundant OTUs such as a Fusarium sp. Figure 5: Bacterial OTUs that were significantly increased or depleted in the Hg-contaminated treatment in comparison to the uncontaminated control in earthworm (**A**) and cast (**B**) samples from experiment 1. The size of the points represents the square root of the read abundance of the OTUs. The OTUs are listed by taxonomic class, and points are color coded according to taxonomic phylum. OTU (Hypocreomycetidae) and a Preussia sp. OTU (Pleosporales) and by a significant decrease in a Scytalidium sp. OTU (Leotionycetes), a Pseudaleuria sp.