Ecology of Stream Nutrient Pulses

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Anthropic disruption of nutrient cycles has dramatically increased nutrient availability to stream ecosystems leading to a global eutrophication crisis threatening the many services stream ecosystems provide to human society. For many streams, especially those in agro-ecosystems, large quantities of nutrients are delivered to streams during short-duration hydrologic events. However, the ecological consequences of pulse nutrient loadings to streams are not well described. My research program will use a series of mesocosm experiments to: 1) quantify effects of pulse nutrient additions on algal diversity and biomass, and; 2) identify environmental factors (i.e., flow, light and ambient nutrient availability) regulating the magnitude and nature of community change caused by pulse nutrient additions. The afore-mentioned mesocosm experiments, coupled with seasonal phosphorus addition experiments to streams in the basins of Lakes Erie and Winnipeg, will be used to determine if diversity and biomass changes in algal communities mediate rates of associated ecosystem processes and food web structure. Stability of the identified community-ecosystem process linkages will be determined across space and time using two separate field surveys. Combined, this research will address multiple gaps along the knowledge chain linking landscape patterns to reach-scale nutrient delivery to algal dynamics and, ultimately, stream ecosystem processes. These data will also provide foundational information needed to generate tools that can enhance stream monitoring programs and set nutrient targets that can be used to protect and restore streams from impairment by stream nutrient pulses. My research program will initiate this process by applying the described relationships linking environmental properties to algal communities and ecosystem processes to generate and test scalable models predicting ecological consequences of pulse nutrient loadings. These models will allow prediction of reach-scale changes in algal diversity and nutrient uptake that can impact valued ecosystem services (recreation and water purification) under forecasted climate and land use change scenarios. My lab will continue to work with decision-makers in government to incorporate these data and tools into policy thereby enhancing management of stream ecosystems threaten by eutrophication within Canada and around the world. The proposed work will engage collaboration with 4 PhD students, 4 MSc students, 5 undergraduate thesis students and multiple undergraduate research assistants. These students will receive extensive training in all aspects of research within the aquatic sciences providing them the communication, leadership and technical skills for successful careers in academic, government and private sectors.