Effect of climate change on permafrost microbiome at the Pleistocene-Holocene and Holocene-Anthropocene transitions

  • Author / Creator
    Saidi-Mehrabad, Alireza
  • Understanding past and future responses of Arctic soil microbes to climate change is critical to an understanding of ecosystem function and climate change feedbacks; the goal of my thesis was to obtain a clearer understanding of these feedbacks. The remnants of the Pleistocene and early Holocene biota, including microorganisms, are preserved in the permafrost of Eastern Beringia, which could potentially show how soil microbes were shaped in Eastern Beringia by the ancient climate change that occurred at the end of the last ice age. However, contamination, low biomass, and physical complexity of permafrost samples create difficulties for molecular analyses. My results show that none of the widely used permafrost decontamination methods fully removed intentionally added biological tracer; hence, I introduced a novel method based on bleaching and scraping. Further, I showed that while permafrost chemical parameters and age did not affect decontamination, they influenced DNA extraction efficiency. I tested multiple widely used DNA extraction kits and modified one to acquire sufficient DNA from difficult permafrost samples. Using this optimized sampling and extraction protocol, I examined whether relict permafrost microbial communities provide a window into past soil microbial communities or not. Microbial community composition and soil chemistry at the Pleistocene-Holocene transition indicated that these parameters were stable until the climate system crossed a threshold, after which there was an abrupt shift to a new steady state. These findings may provide insights into possible future shifts in modern soils. I also examined the response of Arctic methanotrophs (microbes that use CH4 as their sole source of energy) to increases in temperature and active layer disturbance, which both parameters are going to be widespread in Anthropocene. Soil disturbance had a more significant effect on methanotroph community structure than temperature. There was a strong linear relationship between CH4 oxidation rate and temperature; furthermore, CH4 oxidation rates significantly increased in disturbed soils. The active methanotrophs shifted in response to temperature in undisturbed samples, but not in disturbed samples. The results of my thesis complement the previous studies regarding the carbon cycle in the fragile Arctic, and could lead to generation of effective strategies for better management of novel fragile ecosystems in a warmer world.

  • Subjects / Keywords
  • Graduation date
    Spring 2021
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.