Microbial biogeography and colonisation in Arctic terrestrial ecosystems

Malard, Lucie (2019) Microbial biogeography and colonisation in Arctic terrestrial ecosystems. Doctoral thesis, Northumbria University.

Preview

Text (Doctoral thesis) Malard.Lucie_phd.pdf - Submitted Version Download (231MB) | Preview

Abstract

The considerable microbial diversity of soils and their key roles in biogeochemical cycling and in the generation and decomposition of climate active gases has led to a growing interest in their global distribution and the underlying processes driving community structure. The Arctic is the fastest warming region on Earth and Arctic ecosystems are known to harbour significant microbial diversity, far more diverse and numerous in the region than was once thought. Yet despite this interest in Arctic microbial communities, their geographic distribution and structure remains elusive as there are a lack of large scale studies across the region. Selection and dispersal are two of the processes involved in bacterial community structure and while it is widely accepted that microorganisms are constantly dispersed and deposited everywhere, whether the deposited invaders have the ability to colonise remains largely unknown. The aims of this thesis were to characterise bacterial diversity across the Arctic region, determine biogeographical distribution, evaluate the influence of environmental and spatial factors on soil bacterial community structure across various spatial scales, and assess the colonisation potential of dispersed microorganisms in Arctic soils.
Using soil samples collected across the region, bacterial communities were characterised and a core microbiome composed of 13 taxa was identified, highlighting the low levels of ubiquity in the region and providing evidence of biogeographical distribution. It produced a baseline of bacterial diversity in the Arctic which could be used for monitoring purposes and to model spatial distribution. Key environmental variables influencing communities at various spatial scales were identified, with pH as a key variable at the Pan-Arctic scale and organic carbon important at the landscape scale. Overall, selection by environmental variables was a key process involved in structuring bacterial communities. Dispersal also had an important role and appeared to have a consistent influence at all scales of investigation. The colonisation potential of dispersed microorganisms deposited in Arctic soils was investigated using snow melt as a model for dispersal. Successful colonisation was only observed in acidoneutral soils, suggesting that colonisation may rarely be successful, despite the constant deposition of airborne invaders through wet and dry deposition processes.

Actions (login required)

View Item

Downloads