No description available.

Within our ecosystems, soil biota control an array of functions, such as nutrient cycling and decomposition, and have been pursued as a soil quality indicator. Though microbial communities are known to be a reflection of their environment, small scales dynamics within an agricultural system have been overlooked for many years leading to gaps when inferring on relative microbial values. To further asses our current microbial knowledge, two experiments analyzing microbial phospholipid fatty acid (PLFA) structures and enzyme activities sought out to determine temporal fluctuations, cycles, and driving force behind simulated daily microbial parameter outputs. Across both studies, temporal effects, cyclical structures, and common driving forces were recorded, but further validation and characterization is needed to solidify the temporal dynamics of the microbial community. Overall, this information serves as a valuable step towards determining the most viable tillage systems based on environmental conditions, and physical proof of small scale microbial fluctuations.

Petroleum contamination is ubiquitous worldwide, and poses significant health risks to humans, organisms, and the environment. Understanding the fate and behaviour of these chemicals is extremely important in order to predict and mitigate the effects of spills and accidental releases, and limit the exposure of these contaminants to humans and ecosystems. The physical and biological interactions with various petroleum hydrocarbons released into the environment were examined throughout this thesis in two different environmental settings; offshore bay sediments near Deepwater Horizon oil spill impacted sites, and an experimental aquifer injected with compounds representative of ethanol blended fuels. Stable carbon isotopes were used to identify carbon sources in a given environment as well as utilized by microbial communities during biodegradation of petroleum hydrocarbons. Patterns of n-alkanes, low levels of UCM and the lack of PAHs suggest hydrocarbons in Barataria Bay sediments were of dominantly terrestrial origin. Stable carbon isotope analysis of microbial lipids and n-alkanes indicate the presence of some petroleum residues, however there is no strong evidence of Deepwater Horizon oil. Dissolved ethanol, toluene, and MTBE were continuously injected into a pilot-scale laboratory tank simulating an unconfined sand aquifer contaminated with ethanol blended fuel. Ethanol, toluene and MTBE all experienced significant mass loss within the aquifer, which was attributed to biological degradation using stable carbon isotope analysis of residual hydrocarbons. Isotopic analysis of PLFA indicated a strong ethanol sourced signature used in microbial metabolism with some indications of an additional carbon sources such as toluene or MTBE. / Thesis / Master of Science (MSc)

All organisms within a forested system play a role in the biogeochemical cycle, not only within the forest but also within the global community. Soil microorganisms are a vital part of this cycle, as they sequester or make nutrients available for the development of the forest environment. When a disturbance event occurs, changes to the environment occur; however, it is unclear how these changes affect the soils microbial community. This 2-year (2007 and 2008) study was carried out to obtain a preliminary assessment of the microbial community structure and nutrient (nitrogen and phosphorus) availability within lodgepole pine stands of the Boreal Plain ecozone in west-central Alberta. Six stands of different ages were selected to determine the differences between pre and post harvest. Nutrient flux measurements were conducted using plant root simulator (PRS) probes to investigate the changes in nutrient availability. The microbial community structures were determined using two biochemical methods. The first one was a community level physiological profile (CLPP), which provides information concerning the functional characteristics of the microbial communities. Phospholipid fatty acid (PLFA) analysis provides information about the physiological characteristics of the microbial community. Analysis of the PRS probes results varied for the two nutrients: phosphorus (P) and nitrogen (N). Nitrogen availability was determined by examining the fluxes of ammonium and nitrate to the PRS probes. These did not show a strong relationship between the different aged stands during 2007 or 2008. In addition, no statistical difference was shown between the 2007 and 2008 data compared to the LFH or the mineral soil of the stands. Phosphorus, however, did show a potential trend where there was an initial increase of available P after harvest and then a gradual decrease, as the forest stands matured. This was strongly observed within the LFH, while there was a slight increase in the mineral layer. These trends remained consistent over the two-year period showing a gradual decrease in P flux to the PRS probes as a stand aged even in just one year. The microbial communities did not show a strong change after a forest-harvesting event. When examining the functional groups, there was a drastic shift in the LFH layer microbial community over the first sampling season. This change remained the same within the beginning of the second sampling year. This shift occurred in all stands due to an environmental factor, which was suspected to be the increase in moisture during the season. The change in the microbial communities was not observed, however, in the mineral layer of the soil when the functional structure was examined. When the physiological composition of the microbial communities was observed, though, using PLFA, it was apparent that the physiological characteristics of the microbial community had changed in the mineral soil. Furthermore, no physiological change was observed in the microbial communities of the LFH, only a functional change.

All organisms within a forested system play a role in the biogeochemical cycle, not only within the forest but also within the global community. Soil microorganisms are a vital part of this cycle, as they sequester or make nutrients available for the development of the forest environment. When a disturbance event occurs, changes to the environment occur; however, it is unclear how these changes affect the soils microbial community. This 2-year (2007 and 2008) study was carried out to obtain a preliminary assessment of the microbial community structure and nutrient (nitrogen and phosphorus) availability within lodgepole pine stands of the Boreal Plain ecozone in west-central Alberta. Six stands of different ages were selected to determine the differences between pre and post harvest. Nutrient flux measurements were conducted using plant root simulator (PRS) probes to investigate the changes in nutrient availability. The microbial community structures were determined using two biochemical methods. The first one was a community level physiological profile (CLPP), which provides information concerning the functional characteristics of the microbial communities. Phospholipid fatty acid (PLFA) analysis provides information about the physiological characteristics of the microbial community. Analysis of the PRS probes results varied for the two nutrients: phosphorus (P) and nitrogen (N). Nitrogen availability was determined by examining the fluxes of ammonium and nitrate to the PRS probes. These did not show a strong relationship between the different aged stands during 2007 or 2008. In addition, no statistical difference was shown between the 2007 and 2008 data compared to the LFH or the mineral soil of the stands. Phosphorus, however, did show a potential trend where there was an initial increase of available P after harvest and then a gradual decrease, as the forest stands matured. This was strongly observed within the LFH, while there was a slight increase in the mineral layer. These trends remained consistent over the two-year period showing a gradual decrease in P flux to the PRS probes as a stand aged even in just one year. The microbial communities did not show a strong change after a forest-harvesting event. When examining the functional groups, there was a drastic shift in the LFH layer microbial community over the first sampling season. This change remained the same within the beginning of the second sampling year. This shift occurred in all stands due to an environmental factor, which was suspected to be the increase in moisture during the season. The change in the microbial communities was not observed, however, in the mineral layer of the soil when the functional structure was examined. When the physiological composition of the microbial communities was observed, though, using PLFA, it was apparent that the physiological characteristics of the microbial community had changed in the mineral soil. Furthermore, no physiological change was observed in the microbial communities of the LFH, only a functional change.

Across the United States, high tunnels are used as a means of season extension and control over climatic variability in fruit and vegetable production. However, high tunnel systems are an intensive form of agricultural production which may compromise soil and crop quality over time. This study examined the effects of the varying environmental conditions, created in two types of tunnel system, movable and stationary, on the flow of nitrogen from amendment to plant and impact on crop and soil quality parameters. The way nutrients cycled through these systems was different and the nutrient treatments had no consistent effects on soil nutrient parameters, although some microbial groups were affected by the nature of the nutrient amendment. No exposure to rainfall resulted in an accumulation of leachable NO3 in the stationary tunnels. Spinach yields were superior to those in a previous study at the same site however, leaf NO3 levels consistently exceeded EU maximum limits for fresh-sap leaf NO3. We cannot conclude from our data if there was a compromise of crop or soil quality in the high tunnel production systems and further investigation is necessary as high tunnels gain in popularity and make a larger footprint on the agricultural landscape.

The PLFA profiling method was adopted and used to determine changes in microbial community structure and abundance along natural and human-induced environmental gradients. The presented studies were based on field sampling campaigns combined with targeted laboratory experiments. According to the aims of particular studies, microbial PLFA fingerprinting was combined with the auxiliary below- and aboveground ecosystem characteristics to identify the drivers of microbial responses to environmental changes or with 13C-labelling and metagenomics to obtain more complex information about running processes and involved microorganisms.

No description available.

<p>Microorganisms are the most abundant living things on the planet and they drive many important environmental processes. They can do this by coupling reduction – oxidation (redox) reactions. In such reactions, the oxidation of reduced organic matter is coupled with the reduction of another compound, which serves as the electron acceptor. All microbes contain lipids in their cells; phospholipids are the main components of the cell membrane where they make up a consistent component of cell mass. Therefore, in situations where direct cell count is unrealistic, lipid analysis can be used to provide information on microbial communities. Because they hydrolyze shortly after cell death,PLFAs indicate only viable cell biomass, and PLFA analysis provides valuable insight on cell density distribution across a site. One application of PLFA analysis is within this thesis, where it was used to investigate the microbial community at Mildred Lake, Syncrude’s primary tailings settling basin. At Mildred Lake, Syncrude is constructing a freshwater fen over the deposited composite tailings (CT) as part of their reclamation process. Understanding the microbial biogeochemical cycling associated with these reclamation activities is an important component for management decisions affecting the site and thus, inform future reclamation activities.</p> <p>PLFA analysis on samples from the site showed variable concentrations equivalent to estimated cell densities on the order of 107 decreasing to 106 in the CT.These cell density ranges are expected for oligotrophic systems. Phospholipids can also be biomarkers if they are indicative of a specific group of microbes. The study at Mildred Lake identified biomarkers for sulfate reducing bacteria (SRBs). The presence of these biomarkers provided a basis for the hypothesis that sulfide detected at the site was potentially from SRBs.</p> <p>This thesis provides information on the fundamental concepts of lipids and the application of lipid analysis on the environmental samples from the Mildred Lake site to understand its microbial community and cycling of sulfur to prevent potential environmental issues associated with the generation of sulfide.</p> / Master of Science (MSc)

The role of aquifer microorganisms in controlling arsenic contamination of Bangladesh aquifers via oxidation of organic carbon coupled with reduction of sedimentary iron oxyhydroxides and concomitant arsenic dissolution is generally accepted. What remains to be ascertained is the in situ biogeochemical mechanisms of cycling different carbon sources and directly relating indigenous microbiota to arsenic release. Using biomarker fingerprint approaches, this dissertation expanded the presently growing research in the biogeochemical carbon cycling controlling arsenic contamination in Bangladesh aquifers. Comprehensive profiles of microbial cell membrane components (PLFA and sterols) at three different aquifers tested the regional distribution of aquifer microbial community abundance, structure, and organic input potential across Araihazar. The highly variable bulk viable microbial biomass observed across these three sites confer both regional-scale and localized heterogeneous distributions of in-aquifer microbial communities which control carbon cycling in the aquifer. The lack of correlation between PLFA biomarkers and dissolved arsenic challenges the assumption that greater extent of microbial community metabolism results in an increase in arsenic in groundwater. Natural abundance radiocarbon isotope Δ14C analysis of cell membrane PLFA and available carbon pools (SOC, DOC, DIC) confirmed that young organic carbon substrates are being cycled at two of the three sites investigated here. This corroborates previous reports at nearby sites (Site B and F) thereby contributing to a well-constrained carbon source which actively support microbial metabolism over a regional scale. Sterol biomarker distributions were characterized to determine potential sources of organic input into the aquifer. In particular, the importance of raw human and/or animal sewage waste as a source of labile carbon was assessed by measuring the faecal biomarker Coprostanol and comparing its abundance to other sources of biogenic sterols using sewage input proxies (Sewage Contamination Index, Coprostanol/Cholesterol ratio). This was motivated by previous findings which correlated sewage contamination with dissolved arsenic at depth at nearby sites. While sewage contamination was low in the shallow aquifers at these sites, it is more likely that plant organic matter supported the elevated microbial abundance at shallow depths. On the other hand, evidence presented in this project suggests that sewage contamination intrudes into deeper aquifers (e.g. buried Pleistocene) and contributes to the vulnerability of previous pristine aquifers to future arsenic contamination. / Thesis / Master of Science (MSc)