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Temporal coherence of nutrients and implications for understanding British Columbia lake water quality variation

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Title: Temporal coherence of nutrients and implications for understanding British Columbia lake water quality variation
Author: Jensen, Ernest Victor
Degree Master of Science - MSc
Program Environmental Sciences
Copyright Date: 2010
Publicly Available in cIRcle 2010-10-18
Abstract: Temporal coherence, or the degree to which lakes behave similarly through time, provides new insights into the relationship between extrinsic drivers such as climate, and synchronous variation in lake variables at scales beyond the individual lake and catchment. A review of relevant literature suggests coherence of nutrients is highest among proximate pairs of short water residence time lakes within a common drainage path. High connectivity and short water residence times reduce the potential for catchment and lake specific alteration of the discharge signal. Few studies to date have explored coherence of total nitrogen and total phosphorus among lakes. To evaluate nutrient coherence among British Columbia (BC) lakes, I assembled spring estimates of total nitrogen and total phosphorus values over the period 1977 to 2007 for twenty-six lakes. To optimize coherence, I utilized a depth composite mean from a single deep site on lakes with at least 10 years of spring data. All lakes occur in catchments with varying degrees of anthropogenic disturbance and reflect a broad range of lake morphology and climatic conditions in both coastal and interior areas of BC. I explored the potential for climate to cause nutrient coherence by determining whether discharge was synchronous among nearby drainages, and whether lake nutrient variability was dependent on antecedent catchment discharge. Subsequently, I tested whether nutrient coherence was dependent on lake-pair proximity, similarity in lake water residence time, or lake fertility. Temporal coherence was calculated as the average Pearson Product Moment Correlation (r). Discharge was found to be highly coherent, particularly among streams in southern BC, over distances of several hundred kilometers. Temporal coherence of total nitrogen among lakes at all spatial scales was very weak but positive. Coherence was greater and positive for total phosphorus. Phosphorus coherence was not dependent on lake pair proximity, and dependence on water residence time was limited to coastal lakes. Temporal coherence of phosphorus was significantly greater for oligo-mesotrophic lakes than eutrophic lakes across significant spatial scales. These findings should be considered when interpreting lake response to local stressors and setting lake management targets.
URI: http://hdl.handle.net/2429/29248
Scholarly Level: Graduate

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