|dc.description.abstract||Over the recent decades, there has been an increase in human-related negative environmental impacts on aquatic ecosystems worldwide. These impacts are varied and can include climatic variations as well as increased urban and industrial developments. These impacts can be challenging to manage as they can manifest themselves in a cumulative manner over very large spatial (watershed) and temporal (decadal) scales. In response to these challenges, scientists have been developing methods which attempt to assess the increasingly complex interactions between our environment and the current and future demands of society. This thesis proposes a framework for quantifying cumulative changes in water quality and quantity and demonstrates its implementation in an entire watershed, the Athabasca River basin in Alberta, Canada. The Athabasca River basin is an ideal watershed for this study as it has undergone significant increases in urban and industrial developments which have the potential to impact this aquatic ecosystem.
The province of Alberta, Canada is currently experiencing significant economic growth as well as increasing public awareness of its dependence on water. The Athabasca River is a glacial fed river system with a basin covering 157 000 km2 and is the longest (1538 km) unregulated river in Canada. The basin holds significant cultural and economic importance, supporting more than nine First Nation groups, and providing water to hundreds of industries. There has been an increasing level of industrial, urban and other land-use related development (pulp and paper mills, oil sands developments, agriculture, and urban development) within the Athabasca River basin. Many of the historical water quantity and quality data for this basin have not been integrated or analyzed from headwaters to mouth, which affects development of a holistic, watershed-scale cumulative effects assessment.
The main goal of this thesis was to develop and apply a quantitative approach (framework) to assess and characterize the cumulative effects of man-made stressors (e.g. municipal effluent, pulp and paper effluents, oil sands) on indicators of aquatic health (water quality and biological responses) over space and time for a model Canadian river, the Athabasca River, Alberta. This framework addresses the problems of setting an historical baseline, and comparing it to the current state in a quantitative way. This framework also creates the potential for the prediction of future impacts by creating thresholds specific to the study area. The outcome of this framework is the identification and quantification of specific stressors (dissolved sodium, chloride and sulphate) showing significant change across the entire Athabasca River basin, as well as the development of thresholds for these parameters.
The first part of this framework was to quantify any spatial and temporal changes in water quality and quantity across the entire basin from headwaters to mouth, across two time periods, historical and current, over a period of 40 years. Data were collected from several federal, provincial and non-government sources. A 14-30% decrease in discharge was observed during the low flow period in the current time period in the lower three river reaches with the greatest decrease occurring at the mouth of the river. Dissolved sodium, sulphate and chloride concentrations in the second time period were greater than, and in some cases double, the 90th percentiles calculated from the first time period in the lower part of the river.
Based on these findings, the second portion of the framework involved developing basin-specific thresholds for these parameters using the partial life-cycle fathead minnow (Pimephales promelas) bioassay. Two laboratory experiments (dissolved sodium and dissolved chloride) and three field experiments (sodium chloride, dissolved sulphate and water collected downstream of industrial inputs at the mouth of the Athabasca River) were conducted using a diluter system allowing for the dilution of a 100% test solution (based on the highest recorded concentration of the respective parameter in the river) down to 50%, 25%, 12.5%, 6.25% and a 0% control. Significant changes in egg production were identified and linked to changes in gill diffusion distances illustrating the chronic impacts of these parameters on fathead minnow (FHM). The threshold range determined in the laboratory for dissolved sodium was between 12.5% (36.11 mg/L) and 50% (57.00 mg/L) and dissolved chloride less than 22.22 mg/L. At levels outside or above these ranges a possible decrease in reproductive output may occur. The threshold range determined in the field studies for dissolved sulphate concentration was between 23.33 mg/L and 100 mg/L and for the sodium chloride experiment the greatest increases in reproductive output occurred in the highest treatment (25.43 mg/L Na and 38.90 mg/L Cl) which was similar to the range identified in the laboratory study for dissolved sodium.
These results showed that significant changes have occurred in both water quantity and quality between the historical and current day Athabasca River basin. It is known that in addition to climatic changes, rivers which undergo increased agricultural, urban and industrial development can experience significant changes in water quantity and quality due to increased water use, discharge of effluents and surface run-off. Using the results from this thesis, we can begin to quantify dominant natural and man-made stressors affecting the Athabasca River basin as well as place the magnitude of any local changes into an appropriate context relative to trends in temporal and spatial variability. This thesis is a significant contribution to method development for watershed-scale cumulative effects assessment including development of whole river benchmarks for sublethal exposures of fish to increasing salinity for a river of economic and cultural importance and experiencing significant development pressure.||en_US