Robinson Ridge 2019 – Canary in the Coal Mine - DNA subsoil and surface sequencing A16S, 18S, 16S, ITS

Robinson Ridge (66° 22’ S, 110° 35’ E) is a small, rocky patch of ice-free ground on a peninsula located in the east coast of Windmill Islands, Eastern Antarctica. The northern part of Robinson Ridge hosts a substantial bryophyte community dominated by the Antarctic endemic moss, Schistidium antarctici (Robinson et al., 2018). Between 2000 – 2013, these moss beds had presented evidence of drying. However, since Antarctica experienced a major heatwave in the summer of 2020 that accelerated ice melts, providing ephemeral moisture to the soils, moss beds that were previously physiologically stressed, had recovered into their green, healthy state.The soil microbial community at Robinson Ridge was first sampled in the austral summer of 2005 and was found to harbour relatively high abundances of Actinobacteriota, Eremiobacterota and the rare candidate phylum Ca. Dormibacterota (Ferrari et al., 2016; Siciliano et al., 2014). In 2017, these three oligotrophic phyla were proposed to be capable of a novel form of autotrophic carbon fixation, termed atmospheric chemosynthesis (M. Ji et al., 2017). In order to develop the baseline data required for monitoring anthropogenic-induced impacts on the Antarctic ecosystem, it is important to understand the environmental drivers shaping the soil microbial community at fine, local scale, especially the Antarctic microbiota is known to be closely linked to soil properties. The response of the unique microbial diversity in Robinson Ridge along with the broad vegetation cover, may act as the canary in the coal mine, allowing us to make informed decisions for conservation and protection purposes.In this study, we used a 300-m-continuous slope to assess the fine scale heterogeneity of the soil environmental and microbial properties in Robinson Ridge. In 2019, up to 93 surface (biocrust) and subsurface soil samples were collected from three parallel 300-m-transects, 2 m apart, with samples taken at variable lag distances of 0, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 100.1, 100.2, 100.5, 101, 102, 105, 110, 120, 150, 200, 200.1, 200.2, 200.5, 201, 202, 205, 210, 220, 250 and 300 m. This spatial sampling design was identical to that which occurred in 2005 (Siciliano et al., 2014). A subset of 18 subsoil samples (at 6 x distance points 0, 2, 100, 102, 200, 202m of all three transects) were selected for a regional biodiversity study, and hence the data for these 18 subsoil samples can be found in the record, “AAS_4406_Windmill_Islands_DNA_A16S,18S,16S, ITS”. As the sampling transects represented a single contiguous soil catena (300x6 m2) that encompasses a hillslope with wind-exposed arid soils and snowmelt-sustained-moss beds at the bottom of the slope, the samples were grouped into three, based on their distance and elevation along the established transect: “Bottom” soils (elevation less than 8 m, distance between 0 – 50 m), “Mid” soils (elevation 10 – 16 m, distance between 100 – 150 m), and “Top” soils (elevation 20 – 23 m, distance between 200 – 300 m). “Bottom” soils at the hillslope had access to meltwater flow from the surrounding snow patches and were the nearest to the moss communities. All soils (0.4 g) were extracted in triplicates using the FastDNA SPIN kit prior to subjecting the gDNA to next-generation sequencing. Archaeal 16S rRNA gene, Bacterial 16S rRNA gene, Micro-eukaryotes 18S rRNA gene, and Fungal ITS1/ITS2 diversity data were obtained using Illumina sequencing combined with comprehensive soil physiochemical data.Details on Illumina sequencing can be found here: https://www.ramaciotti.unsw.edu.au/services/next-generation-sequencing/microbiome-custom-target. Except for A16S data, all primer sequences were not retained in the raw DNA files. The four primer sets used to target specific hypervariable gene regions to cover the soil microbiome in this study were the:27F/519R - Bacterial 16S V1-V31391F/EukBr - Eukaryotic 18S V9A2F/519R - Archaeal A16SITS1F-ITS2         - Fungal ITS1fITS7-ITS4          - Fungal ITS2This study capitalises on the capability to pinpoint tipping points along natural environmental gradients at fine scales to better understand the relationship between environmental drivers and structure of the local microbiota at a site known to be susceptible to climate change.Reference:Robinson, S. A., King, D. H., Bramley-Alves, J., Waterman, M. J., Ashcroft, M. B., Wasley, J., . . . Hua, Q. (2018). Rapid change in East Antarctic terrestrial vegetation in response to regional drying. Nature Climate Change, 8(10), 879-884. doi:10.1038/s41558-018-0280-0Ji, M., Greening, C., Vanwonterghem, I., Carere, C. R., Bay, S. K., Steen, J. A., . . . Ferrari, B. C. (2017). Atmospheric trace gases support primary production in Antarctic desert surface soil. Nature, 552(7685), 400-403. doi:10.1038/nature25014Ferrari, B. C., Bissett, A., Snape, I., Dorst, J. v., Palmer, A. S., Ji, M., . . . Brown, M. V. (2016). Geological connectivity drives microbial community structure in polar ecosystems. Environmental Microbiology, 18(6), 1834-1849. Siciliano, S.D., Palmer, A.S., Winsley, T., Lamb, E., Bissett, A., Brown, M.V., van Dorst, J., Ji, M., Ferrari, B.C., Grogan, P., Chu, H., and Snape, I. (2014). Soil fertility is associated with fungal and bacterial richness, whereas pH is associated with community composition in polar soil microbial communities. Soil Biology and Biochemistry, 78, pages 10-20.