Abstract
Waterlogged burial conditions impact upon artefact preservation. One major determinant of preservation is presence and behaviour of microorganisms, however, unravelling the mechanisms, especially in waterlogged conditions is challenging. In this study, we analysed elemental composition, bacterial diversity and community structure from excavation trenches at the Roman Site of Vindolanda, Northumberland, UK, using pXRF and 16S rRNA gene amplicon sequencing. Excavation trenches provide information of different occupation periods. The results indicated that microbial communities were dominated by Firmicutes, Bacteroidetes and Proteobacteria at a phylum level. Samples which also had visible vivianite presence showed that there were marked increases in Methylophilus. Methylophilus might be associated with favourable preservation in these anaerobic conditions. More research is needed to clearly link the presence of Methylophilus with vivianite production. The study emphasises the need for further integration of chemical and microbiome approaches, especially in good preservation areas, to explore microbial and chemical degradation mechanisms.
Highlights
Waterlogged burial conditions impact upon artefact preservation
Between Roman occupation periods, wooden and stone buildings were destroyed, sealed with thick layers of clays and re-built upon, forming layers in which oxygen was excluded from the decomposing material underneath
Vivianite is associated with other instances of good preservation including that of human remains: for example human DNA of increased quality can be extracted from samples located within the Brisbane burial grounds from underneath vivianite c rusts[7]
Summary
Waterlogged burial conditions impact upon artefact preservation. One major determinant of preservation is presence and behaviour of microorganisms, unravelling the mechanisms, especially in waterlogged conditions is challenging. Our assumption is that the exceptional levels of preservation seen at Vindolanda are brought about by a combination of environmental factors linked to the unusual anaerobic and elemental conditions observed, through an interaction between local geochemistry, hydrology and past human activity at the site (clay sealing). Such conditions in turn impact on the microbial community within the soil, producing vivianite and limiting growth of degrading organisms
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