Graduate Theses & Dissertations

Effects of hydrologic seasonality on dissolved organic matter composition, export, and biodegradability in two contrasting streams
Environmental and seasonal processes are important watershed drivers controlling the amount, composition, and fate of dissolved organic matter (DOM) in aquatic ecosystems. We used ten months of water samples and eight months of bioassay incubations from two contrasting catchments (agriculture and natural, forested) to assess the effects of seasonal variability on the composition, export, and biodegradability of DOM. As expected, the DOM composition and exports were more allochthonous-like and autochthonous-like in the forest and agriculture streams, respectively. However, we found no relationship between DOM composition and biodegradability in our study, suggesting that broad environmental factors play a large part in determining bioavailability of DOM. We found that both differences between the catchments and seasonal variability in hydrology and water temperature cause shifts in DOM composition that can affect exports and potentially affect its susceptibility to microbial activity. More research is needed to fully understand the impact of land use and temporal variability on bioavailability and delivery to downstream ecosystems. Author Keywords: Bioavailable dissolved organic carbon, Biodegradability, Dissolved organic matter, Export, Seasonality, Streams
Hydrological and Flooding Effects on Stream Nutrient Levels
Stream solutes are strongly linked to hydrology, and as such, we sought to better understand how hydrology, particularly flooding, influences nitrogen (N) and phosphorus (P) levels. We used a long-term dataset of monthly water quality samples for many Ontario, Canada, catchments to assess the effects of landscape variables, such as land use and physiography, on the export of nutrients during floods, and to characterize overall concentration-discharge patterns. In general, we found that landscape variables could partially explain the export variation in flood waters, but that the importance of specific variables depended on flood characteristics. We also found that overall concentration-discharge relationships for N and P C were positive, but non-linear, with greater concentrations on the rising limb of the hydrograph depending on the nutrient. With these results, we have identified general patterns between nutrients and hydrology, which will be helpful for managing the ecological effects of flooding. Author Keywords: C-Q relationships, Discharge, Export, Flooding, Nutrients, Thresholds
Comparison of the Optical Properties of Stratiotes aloids and the Local Plant Community
As part of a mandate to control the spread of Stratiotes aloides (WS; water soldier) in the Trent Severn Waterway, the Ministry of Natural Resources (MNR) created a management plan to eradicate WS. However, one of the biggest challenges in eradicating WS or any invasive aquatic plant is the ability to estimate the extent of its spread and detect new populations. While current detection methods can provide acceptable detection, these methods often require extensive time and effort. The purpose of this thesis was to assess the use optical properties of WS and WS exudates for detection, in order to improve on current detection methods. The optical properties of WS were sampled at three different sites during three different seasons (spring, summer, and fall) by a) randomly sampling tissue from WS and the local plant community at each site, and recording the reflectance properties in a laboratory setting b) collecting dissolved organic matter (DOM) samples from plant incubations and river water in the field. Significant differences in the reflectance properties of WS were observed among samples from different sites and different sampling times; however, changes in fluorescence properties were only seasonal. Despite spatial differences in WS reflectance; WS was detectable using both hyperspectral and multispectral reflectance. When hyperspectral reflectance was used, significant differences between WS and the local plant community were found in June using two bands (i.e. bands 525 and 535, R 2 = 0.46 and 0.48, respectively). Whereas multispectral reflectance was significant different in October using the coastal and blue band. While WS produced a unique signal using both reflectance types, multispectral reflectance had a greater potential for detection. Its greater potential for detection was due to the reduced noise produced by background optical properties in October in comparison to June. DOM derived from WS was also characterized and compared with whole-river DOM samples in order to find unique markers for WS exudates in river samples. While similarities in DOM concentrations of WS exudates to Trent River water limited the ability to detect WS using compositional data, the ratio of C4/C5 components were compared in order to find components that were proportionally similar. Based on the results of this study multispectral and fluorescence techniques are better suited for the detection of a unique WS signature. The results derived from this work are intended to have practical applications in plant management and monitoring, DOM tracing, as well as remote sensing. Author Keywords: Dissolved organic matter, Hyperspectral reflectance, Invasive species management, Multispectral reflectance, PARAFAC, Stratiotes aloides

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