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Microbial diversity, complexity, and dynamics within a ‘grass-to-glass’ profile at a late iron age archaeological site, and as a function of climatic variables


EMSL Project ID
60748

Abstract

We propose to systematically analyze the microbial consortia that are enriched on rock surfaces as a function of depth through a ‘grass-to-glass’ profile using samples obtained during the excavation of: (i) Broborg, a late iron age Swedish vitrified hillfort; (ii) Timna, an ancient copper mine in Israel; and (iii) an obsidian flow at the Newberry volcano. A predictive understanding of processes that underpin mineral weathering, nutrient cycling, and degradation of materials relevant to radioactive waste storage in the environment will be enabled. The proposed experiments will determine how microbial communities interact with natural and anthropological materials, and how these interactions change with availability of different energy sources. Through our previous work, we have identified niche environments, including the vitrified material within the walls of the Broborg hillfort, that contain microbes with specific ecosystem functions. These include: (i) Bacillales, containing taxa that solubilize phosphorus and promote plant-growth; (ii) a Sphingobacterium genus that produces gluconic, lactic, acetic, formic, and oxalic acids; and (iii) taxa known to be involved in lithoautotrophic Mn(II)- and Fe(II)-oxidizing communities. Symbiotic ectomycorrhizal (ECM) tree roots are present as an important niche in our samples, and we found Archaeorhizomycetes fungi, and arbuscular mycorrhizal fungi, both of which have been implicated in mineral weathering in soil environments. We showed that archaea diversity and abundance increase with depth in the profile and identified species, e.g., Thaumarchaeota, that are involved in key element (nitrogen) cycling. We require a range of EMSL tomography, diffraction, and microscopy capabilities to characterize the samples and show the association of these microbial species with vitrified surfaces. We plan to use a combination of microscopy and spectroscopy to establish specific mineral weathering signatures and link them to the phylogenic information, so that we can identify key organisms and processes responsible for accelerating or inhibiting long-term weathering. This includes determining how these organisms and processes are influenced by available energy sources, which change as a function of depth through the profile. Samples from different climatic zones will be used to demonstrate that the observed changes in microbial community structure and function in response to the niche environment is broadly applicable and underpins the ability to predict natural processes including mineral weathering and nutrient cycling. The research is of societal importance as Broborg, Timna and Newberry represent habitat analogues for disposed radioactive waste glass to inform how microbial processes might influence long-term glass waste form durability.

Project Details

Project type
Large-Scale EMSL Research
Start Date
2023-10-01
End Date
N/A
Status
Accepted

Team

Principal Investigator

Carolyn Pearce
Institution
Pacific Northwest National Laboratory

Co-Investigator(s)

Andrew Plymale
Institution
Pacific Northwest National Laboratory

Team Members

Emily Nienhuis-Marcial
Institution
Pacific Northwest National Laboratory

Jessica Allen
Institution
Eastern Washington University

Tanya Cheeke
Institution
Washington State University Tri-Cities

Jose Marcial
Institution
Pacific Northwest National Laboratory

James Neeway
Institution
Pacific Northwest National Laboratory

John Vienna
Institution
Pacific Northwest National Laboratory