Pedogenic and microbial interrelation in initial soils under semiarid climate on James Ross Island, Antarctic Peninsula region

Abstract

Abstract. James Ross Island (JRI) offers the exceptional opportunity to study microbial-driven pedogenesis without the influence of vascular plants or faunal activities (e.g., penguin rookeries). In this study, two soil profiles from JRI (one at Santa Martha Cove – SMC, and another at Brandy Bay – BB) were investigated, in order to gain information about the initial state of soil formation and its interplay with prokaryotic activity, by combining pedological, geochemical and microbiological methods. The soil profiles are similar with respect to topographic position and parent material but are spatially separated by an orographic barrier and therefore represent windward and leeward locations towards the mainly southwesterly winds. These different positions result in differences in electric conductivity of the soils caused by additional input of bases by sea spray at the windward site and opposing trends in the depth functions of soil pH and electric conductivity. Both soils are classified as Cryosols, dominated by bacterial taxa such as Actinobacteria, Proteobacteria, Acidobacteria, Gemmatimonadetes and Chloroflexi. A shift in the dominant taxa was observed below 20 cm in both soils as well as an increased abundance of multiple operational taxonomic units (OTUs) related to potential chemolithoautotrophic Acidiferrobacteraceae. This shift is coupled by a change in microstructure. While single/pellicular grain microstructure (SMC) and platy microstructure (BB) are dominant above 20 cm, lenticular microstructure is dominant below 20 cm in both soils. The change in microstructure is caused by frequent freeze–thaw cycles and a relative high water content, and it goes along with a development of the pore spacing and is accompanied by a change in nutrient content. Multivariate statistics revealed the influence of soil parameters such as chloride, sulfate, calcium and organic carbon contents, grain size distribution and pedogenic oxide ratios on the overall microbial community structure and explained 49.9 % of its variation. The correlation of the pedogenic oxide ratios with the compositional distribution of microorganisms as well as the relative abundance certain microorganisms such as potentially chemolithotrophic Acidiferrobacteraceae-related OTUs could hint at an interplay between soil-forming processes and microorganisms.

Influence of microorganisms on initial soil formation along a glacier forefield on King George Island, maritime Antarctica

“…other Antarctic habitats (e.g. Ganzert et al, 2011;Yan et al, 2017;Meier et al, 2019). Differences between the sites with regards to the observed community compositions were found only in near-surface substrates in the upper 10 cm, while the microbial communities became less diverse and more similar with increasing depth across all investigated soil profiles.…”

“…Furthermore, changes in soil microstructure, induced e.g. by frequent freeze-thaw cycles and associated changes in pore spacing and nutrient contents have been related to shifts in microbial community compositions in soils from maritime Antarctica (Meier et al, 2019). Meier et al (2019) observed a change towards a lenticular microstructure below 20 cm depth, which was related to significant changes in the microbial community compositions.…”

“…Total genomic DNA extracts of each sample were sequenced using tagged 515F (5'-GTGCCAGCMGCCGCGGTAA-3') and 806R (5'-GGACTACHVGGGTWTCTAAT-3') primers after Caporaso et al (2010). The used cycler program and reaction mix were described by Meier et al (2019). The sequencing was performed on an Illumina HiSeq (2 x 300 bp) by GATC Biotech AG, Germany.…”

“…Raw sequencing data obtained by Illumina HiSeq (2 x 300 bp) was processed according to Meier et al (2019) with few differences. Clustering of operational taxonomic units (OTUs) at 97 % sequence similarity and their taxonomic assignments was done with the SILVA data base (version 132, Quast et al, 2013).…”

“…Bacterial abundances were quantified using quantitative PCR (qPCR) and the 314F (5'-CCTACGGGAGGCAGCAG-3') and 534R (5'-ATTACCGCGGCTGCTGG-3') primers after Muyzer et al (1993). The used cycler program and reaction mix were described by Meier et al (2019).…”