Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Lindo, Zoë

2nd Supervisor

Tai, Vera

Joint Supervisor

Abstract

Boreal peatlands are vital for global carbon storage as limited microbial decomposition slows carbon release. However, climate change is expected to affect microbial communities and biomasses, and therefore carbon storage in peatlands. This study sampled experimentally warmed plots from two fens with differing vegetation across two years. Metabarcode sequencing and quantitative PCR (qPCR) assessed changes in microbial diversity and biomass, focusing on bacteria, fungi, and protists. qPCR was also tested as a biomass proxy and corroborated fungal-to-bacterial biomass ratios at each fen, indicating carbon sequestration potential. Experimental warming had no significant effect on microbial diversity, composition, or fungal-to-bacterial ratios, though microbial communities were more influenced by sampling year. This could be from insufficient temporal resolution to detect long-term community changes over short-term variations. Overall, the study demonstrates the importance of temporal scale in characterizing microbial trends in boreal peatlands and shows qPCR provides a reasonable biomass proxy.

Summary for Lay Audience

Peatlands are a type of wetland ecosystem in which organic matter input exceeds decomposition leading to an accumulation of incompletely decomposed organic matter. Peatlands are most commonly found in the boreal region, which stretches across high latitudes of the northern hemisphere, including Canada. In boreal systems, the organic matter is derived from above-ground vegetation, which is largely dominated by mosses (e.g., Sphagnum species) or sedges (e.g., Carex species). There are also unique conditions in boreal peatlands, such as low temperatures, low nutrients, and waterlogged conditions, resulting in large anoxic areas that limit microbial decomposition and thus contribute to carbon sequestration, playing an essential role in global carbon storage in these systems. However, the predicted effects of climate change on these conditions are expected to disproportionately affect boreal peatlands and could potentially alter carbon storage and decomposition processes such that peatlands become carbon sources.

Thus, the aims of this project were to characterize changes in microbial communities focusing on bacteria, fungi and protists under experimental warming to help elucidate changes in microbial communities under climate change. The study was conducted at a large-scale long-term field experiment that consisted of two peatland sites that differed in above-ground vegetation (namely Sphagnum versus Carex species). Sampling was conducted at both field sites from experimentally warmed and ambient plots in 2022, and 2023. To characterize what microbial communities were present in the samples, DNA sequencing was employed. Additionally, quantitative PCR was performed to determine the quantity of DNA in a given sample as a proxy of microbial biomass.

This study revealed that experimental warming largely had no effect on microbial communities, however a significant difference was revealed between sampling years, suggesting environmental variability between the two years played a larger role than warming at the scale used in this study. This study also characterized protist communities at the peatland sites, revealing more diverse communities in the Carex-dominated fen, therefore contributing to this often overlooked and undescribed community. Furthermore, this study corroborated previously known fungal and bacterial biomasses at these sites using emerging molecular methods, providing support for the use of these techniques in this manner.

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