Reference number : GC-2017-Q1-03275, amendment number : , agreement type : G, recipient legal name : Hudson, Jeff (University of Saskatchewan), recipient country : CA, recipient province : nan, recipient city : Saskatchewan, recipient postal code : nan, program name english : Discovery Grants Program - Individual, program name french : Programme de subventions à la découverte - individuelles, program purpose english : This proposal examines the abiotic and biotic factors, including human, that affect biogeochemical processes and water quality in aquatic ecosystems. The factors giving rise to cyanobacterial blooms and their toxins are under intense research. Concern over the loss of ecosystem services (e.g., water quality) has been a major focus. However, only recently has the effect of cyanobacteria on ecosystem function been considered. Cyanobacteria have widespread impacts on food webs through toxin production, resistance to grazing and as poor food quality for grazers. Hence, when lakes are dominated by cyanobacteria their planktonic food webs should be functioning inefficiently. I will test this hypothesis with novel techniques that directly measure food web turnover efficiency. My next objective is to compare two important biogeochemical pathways of P in Lake Diefenbaker (SK). Loading of P from rivers into reservoirs is often a major determinant of water quality. Similarly, planktonic P regeneration is known to be important to maintain productivity. However, the importance of each pathway relative to the other is unknown, despite the potential significance of these processes for lake and reservoir management. Therefore, I propose to measure and compare both pathways in Lake Diefenbaker. My third objective is to determine whole-lake rates of photoammonification. This is a process by which dissolved organic nitrogen (DON) is photodecomposed to the bioavailable nutrient NH 4 in waterbodies. My preliminary research suggests that this process may be significant in spring and summer. However, the rate at which DON is converted to NH 4 as a function of depth in lakes has not been determined, a necessary step to estimate whole system rates. Therefore, I will measure depth integrated photoammonification in a diverse set of prairie and Precambrian Shield lakes in order to establish the relevance of this pathway. My next objective concerns the measurement of NO 3 , an important nutrient affecting water quality in lakes. NO 3 is usually measured with colorimetric methods. However, colorimetric methods entail many steps and are prone to interferences. The second derivative UV technique for NO 3 measurement is emerging as an alternative method; it is rapid, less prone to interferences, and generates less waste. However, this technique has not been tested in more challenging waters typical of prairie regions (e.g., of greater conductivity and higher dissolved organic carbon concentration). My preliminary analyses indicate that both techniques differ greatly in estimating NO 3 in such waters. Therefore, I will compare their performance and determine if the second derivative technique is suitable for NO 3 measurement in prairie waterbodies. These studies will advance our understanding of biogeochemical processes in lakes and reservoirs, and ultimately aid in the management and protection of inland waters., program purpose french : This proposal examines the abiotic and biotic factors, including human, that affect biogeochemical processes and water quality in aquatic ecosystems. The factors giving rise to cyanobacterial blooms and their toxins are under intense research. Concern over the loss of ecosystem services (e.g., water quality) has been a major focus. However, only recently has the effect of cyanobacteria on ecosystem function been considered. Cyanobacteria have widespread impacts on food webs through toxin production, resistance to grazing and as poor food quality for grazers. Hence, when lakes are dominated by cyanobacteria their planktonic food webs should be functioning inefficiently. I will test this hypothesis with novel techniques that directly measure food web turnover efficiency. My next objective is to compare two important biogeochemical pathways of P in Lake Diefenbaker (SK). Loading of P from rivers into reservoirs is often a major determinant of water quality. Similarly, planktonic P regeneration is known to be important to maintain productivity. However, the importance of each pathway relative to the other is unknown, despite the potential significance of these processes for lake and reservoir management. Therefore, I propose to measure and compare both pathways in Lake Diefenbaker. My third objective is to determine whole-lake rates of photoammonification. This is a process by which dissolved organic nitrogen (DON) is photodecomposed to the bioavailable nutrient NH 4 in waterbodies. My preliminary research suggests that this process may be significant in spring and summer. However, the rate at which DON is converted to NH 4 as a function of depth in lakes has not been determined, a necessary step to estimate whole system rates. Therefore, I will measure depth integrated photoammonification in a diverse set of prairie and Precambrian Shield lakes in order to establish the relevance of this pathway. My next objective concerns the measurement of NO 3 , an important nutrient affecting water quality in lakes. NO 3 is usually measured with colorimetric methods. However, colorimetric methods entail many steps and are prone to interferences. The second derivative UV technique for NO 3 measurement is emerging as an alternative method; it is rapid, less prone to interferences, and generates less waste. However, this technique has not been tested in more challenging waters typical of prairie regions (e.g., of greater conductivity and higher dissolved organic carbon concentration). My preliminary analyses indicate that both techniques differ greatly in estimating NO 3 in such waters. Therefore, I will compare their performance and determine if the second derivative technique is suitable for NO 3 measurement in prairie waterbodies. These studies will advance our understanding of biogeochemical processes in lakes and reservoirs, and ultimately aid in the management and protection of inland waters., agreement title english : Novel Biogeochemical Pathways, Patterns and Measurements of Nitrogen and Phosphorus in Lakes and Reservoirs, agreement title french : Novel Biogeochemical Pathways, Patterns and Measurements of Nitrogen and Phosphorus in Lakes and Reservoirs, agreement number : RGPIN, agreement value : 120000.0, agreement start date : 2017-05-10, agreement end date : nan, description english : nan, description french : nan, expected results english : nan, expected results french : nan, additional information english : Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023), additional information french : Subvention ou bourse octroyée s'appliquant à plus d'un exercice financier. (2017-2018 à 2022-2023), owner organization : nserc-crsng, owner organization title : Natural Sciences and Engineering Research Council of Canada | Conseil de recherches en sciences naturelles et en génie du Canada