Lake Zapotlán is a small (1100 ha) endorheic lake in western Mexico that is internationally recognized by RAMSAR. It receives point source pollution from partially treated sewage from two surrounding cities, as well as non-point sources, including urban runoff, agricultural runoff, erosion and consequent deposition of sediment as a result of deforestation surrounding the Lake. The purpose of this study was to determine the severity of pollution in the Lake through measurement of nutrient and bacteria levels and assess for potential human health and ecological risks in Lake Zapotlán. Results found that nutrient levels have increased since 1994 and that they are high enough to cause eutrophication problems. Partially treated wastewater contributes over 30 tonnes of phosphorus to the Lake each year. E. coli levels were extremely high and could pose a health risk to those participating in recreational activities on the Lake.

Anaerobic oxidation of methane (AOM) in peatlands was investigated using 13carbon isotope tracers. Existence of AOM in marine and freshwater ecosystems is well known, but only recently has solid evidence for this process been demonstrated in northern peat accumulating wetland ecosystems. The primary objective of this thesis research was to characterize rates of AOM in peatlands across site types (bogs and fens with varying physicochemical properties) and latitudinal gradients. It was found that AOM was ubiquitous process across North American sites and dominant in fens over bogs, however carbon derived from methane was similar in both types of peatlands. Though, none of the proposed electron acceptors hypothesized stimulated AOM. AOM had a combined, average rate of 2.9 nmol methane kg-1s-1, which would translate to an approximate global consumption of 24 Tg methane annually. This mass of methane is equivalent to almost 7% of all annual anthropogenic carbon dioxide emissions.

Lake Zapotlán is a small (1100 ha) endorheic lake in western Mexico that is internationally recognized by RAMSAR. It receives point source pollution from partially treated sewage from two surrounding cities, as well as non-point sources, including urban runoff, agricultural runoff, erosion and consequent deposition of sediment as a result of deforestation surrounding the Lake. The purpose of this study was to determine the severity of pollution in the Lake through measurement of nutrient and bacteria levels and assess for potential human health and ecological risks in Lake Zapotlán. Results found that nutrient levels have increased since 1994 and that they are high enough to cause eutrophication problems. Partially treated wastewater contributes over 30 tonnes of phosphorus to the Lake each year. E. coli levels were extremely high and could pose a health risk to those participating in recreational activities on the Lake.

Anaerobic oxidation of methane (AOM) in peatlands was investigated using 13carbon isotope tracers. Existence of AOM in marine and freshwater ecosystems is well known, but only recently has solid evidence for this process been demonstrated in northern peat accumulating wetland ecosystems. The primary objective of this thesis research was to characterize rates of AOM in peatlands across site types (bogs and fens with varying physicochemical properties) and latitudinal gradients. It was found that AOM was ubiquitous process across North American sites and dominant in fens over bogs, however carbon derived from methane was similar in both types of peatlands. Though, none of the proposed electron acceptors hypothesized stimulated AOM. AOM had a combined, average rate of 2.9 nmol methane kg-1s-1, which would translate to an approximate global consumption of 24 Tg methane annually. This mass of methane is equivalent to almost 7% of all annual anthropogenic carbon dioxide emissions.

Despite decades of research, the water quality of many lakes is impaired by excess total phosphorus loading. Four studies were undertaken using watershed models to understand the temporal and spatial variability of diffuse urban and agricultural total phosphorus pollution to Hamilton Harbour, Ontario, Canada. In the first study, a novel Bayesian framework was introduced to apply Spatially Referenced Regressions on Watershed Attributes (SPARROW) to catchments with few long term load monitoring sites but many sporadic monitoring sites. The results included reasonable estimates of whole-basin total phosphorus load and recommendations to optimize future monitoring. In the second study, the static SPARROW model was extended to allow annual time series estimates of watershed loads and the attendant source-sink processes. Results suggest that total phosphorus loads and source areas vary significantly at annual timescales. Further, the total phosphorus export rate of agricultural areas was estimated to be nearly twice that of urban areas. The third study presents a novel Bayesian framework that postulates that the watershed response to precipitation occurs in distinct states, which in turn are characterized by different model parameterizations. This framework is applied to Soil-Water Assessment Tool (SWAT) models of an urban creek (Redhill Creek) and an agricultural creek (Grindstone Creek) near Hamilton. The results suggest that during the limnological growing season (May – September), urban areas are responsible for the bulk of overland flow in both Creeks: In Redhill Creek, between 90% and 98% of all surface runoff, and in Grindstone Creek, between 95% and 99% of all surface runoff. In the fourth chapter, suspended sediment is used as a surrogate for total phosphorus. Despite disagreements regarding sediment source apportionment between three model applications, Bayesian model averaging allows an unambiguous identification of urban land uses as the main source of suspended sediments during the growing season. Taken together, these results suggest that multiple models must be used to arrive at a comprehensive understanding of total phosphorus loading. Further, while urban land uses may not be the primary source of sediment (and total phosphorus) loading annually, their source strength is increased relative to agricultural land uses during the growing season.

Despite decades of research, the water quality of many lakes is impaired by excess total phosphorus loading. Four studies were undertaken using watershed models to understand the temporal and spatial variability of diffuse urban and agricultural total phosphorus pollution to Hamilton Harbour, Ontario, Canada. In the first study, a novel Bayesian framework was introduced to apply Spatially Referenced Regressions on Watershed Attributes (SPARROW) to catchments with few long term load monitoring sites but many sporadic monitoring sites. The results included reasonable estimates of whole-basin total phosphorus load and recommendations to optimize future monitoring. In the second study, the static SPARROW model was extended to allow annual time series estimates of watershed loads and the attendant source-sink processes. Results suggest that total phosphorus loads and source areas vary significantly at annual timescales. Further, the total phosphorus export rate of agricultural areas was estimated to be nearly twice that of urban areas. The third study presents a novel Bayesian framework that postulates that the watershed response to precipitation occurs in distinct states, which in turn are characterized by different model parameterizations. This framework is applied to Soil-Water Assessment Tool (SWAT) models of an urban creek (Redhill Creek) and an agricultural creek (Grindstone Creek) near Hamilton. The results suggest that during the limnological growing season (May – September), urban areas are responsible for the bulk of overland flow in both Creeks: In Redhill Creek, between 90% and 98% of all surface runoff, and in Grindstone Creek, between 95% and 99% of all surface runoff. In the fourth chapter, suspended sediment is used as a surrogate for total phosphorus. Despite disagreements regarding sediment source apportionment between three model applications, Bayesian model averaging allows an unambiguous identification of urban land uses as the main source of suspended sediments during the growing season. Taken together, these results suggest that multiple models must be used to arrive at a comprehensive understanding of total phosphorus loading. Further, while urban land uses may not be the primary source of sediment (and total phosphorus) loading annually, their source strength is increased relative to agricultural land uses during the growing season.

Downstream adjustment in stream channel morphology is examined in the context of stream channel confluences. Stream channel confluences represent areas of point specific increases in discharge, flow energy and potential erosion in a river system which will in turn affect the post-confluence downstream morphology. Analysis of 12 confluence junctions from southern Ontario streams, constituting 36 channel reaches in total, show an internally consistent hydraulic geometry relationship but with specific controls on channel morphology related to boundary conditions. Predictions of mainstem morphologies is possible using tributary attributes but reach specific channel confinement and material type add significant influence.

The seasonal asymmetry in coastal temperatures on Hudson Bay was explored and evaluated as a proxy to hindcast sea ice conditions prior to 1972. Various indices of air temperature difference (∆T) between Churchill, MB and Inukjuak, QC were tested for linear correlations with spatially averaged sea ice concentration (SIC) and ice-free season length (IFS). A multiple regression equation employing a 31-day average of peak ∆T and a 61-day average of temperature during freeze-up reproduced the IFS record with an average error of 8.1 days. This equation was employed to extend the IFS record by 28 years. The resulting 68-year time series revealed a significant increasing trend most pronounced from 1985 to 2011. Hindcast data helped eliminate low-frequency climate oscillations of periodicity <68 years as a source of this trend, lending further evidence to the growing consensus of a declining sea ice being the result of anthropogenic climate forcing.

Downstream adjustment in stream channel morphology is examined in the context of stream channel confluences. Stream channel confluences represent areas of point specific increases in discharge, flow energy and potential erosion in a river system which will in turn affect the post-confluence downstream morphology. Analysis of 12 confluence junctions from southern Ontario streams, constituting 36 channel reaches in total, show an internally consistent hydraulic geometry relationship but with specific controls on channel morphology related to boundary conditions. Predictions of mainstem morphologies is possible using tributary attributes but reach specific channel confinement and material type add significant influence.

A climate change impact assessment was conducted to examine the spread of furunculosis found in the fish species of Ouje-Bougoumou; and subsequently to examine the resulting impacts on the health of the community. A past assessment was performed to assess whether there was a temporal relationship between increased temperatures and past incidences of furunculosis using observed climate data and traditional ecological knowledge (TEK) data. To project future impacts of climate change, climate models, lake models and TEK were used. Findings show that the rise in air mean temperature coincides with the timeline of past incidences of furunculosis. It is predicted that the lake temperatures will remain suitable for the presence of A. salmonicida; thus, it is likely that the disease will persist throughout the twenty-first century. To conclude, climate change is not eliminated as a plausible factor to the onset of furunculosis.