Date of Award
Master of Applied Science (MASc)
Environmental Applied Science and Management
A benthic chamber system was developed to measure all major nitrogen cycling processes in lakes. The system coupled advantages of flow-through systems common in core incubations with those of in situ benthic chambers. The system also coupled advantages of N2:Ar and isotope pairing techniques for explicit measurement of gross and net denitrification, allowing determination of N2 fixation. Use of 15N tracer (15N2, 15NO3-, or 15NH4+), in these chambers also allowed explicit and simultaneous in situ measurements of other major nitrogen cycling processes including ammonium and nitrate uptake, DNRA, and ammonification.
Nutrient loading ratios (Si:N and P:N) and community composition of herbivores (Daphnia and mussels) were studied to determine effects on nitrogen cycling using mesocosms simulating thermally stratified, shallow lakes. Increased Si:N enhanced organic matter remineralization in bottom water, enhancing nitrogen loss by denitrification. Herbivore type had no apparent effect on where N was recycled or on N-loss through denitrification.
Lau, Yat-Fung (Jeremy), "Nitrogen Biogeochemistry in Lakes – Chemical and Biological Drivers and Developing Techniques to Explicitly Measure Concurrent Processes" (2012). Theses and dissertations. Paper 786.