project IX
project I

project II

project III

project IV

project V

project VI

project VII

project VIII

project IX

project X

current vacancies

project IX: role of lakes and streams in greenhouse gas budgets: development of predictive models to estimate anthropogenic influences

Human alterations of the nitrogen (N) cycle have led to increased atmospheric concentrations of nitrous oxide (N2O), an important greenhouse gas (GHG), with 310 times the warming potential of carbon dioxide. With the wealth of aquatic ecosystems within Canada, understanding how lakes and rivers affect greenhouse gas relations is critical to creating reliable estimates of natural greenhouse gas fluxes, and to understanding how humans continue to affect greenhouse gas relations by changing aquatic ecosystems. Much work has been dedicated to quantifying N2O fluxes from soils, but fluxes from aquatic sources are poorly characterized. This is despite the 2-20 fold increase in riverine N concentrations in numerous regions (Vitousek et al. 1997), the finding that increased concentrations of inorganic N are correlated with increased N2O emissions (Cole and Caraco 2001), and models of the global N2O budget that suggest rivers and estuaries are large emissions sources, particularly in the northern hemisphere (Seitzinger and Kroeze 1998). To date, no budgets of riverine nitrous oxide emissions based on direct measurements have been published within Canada. It seems likely that N enrichment from agricultural inputs and sewage, as well as atmospheric deposition, has led to increased N2O emissions from many Canadian rivers. Currently, estimates of nitrous oxide release from agriculturally affected streams are based on IPCC methods; however, these methods seem to overestimate N2O fluxes in many regions.

This work will build upon existing watershed-based computer models, adding components to model greenhouse gas relations. These tools, created using existing data and targeted field research, will not only vastly improve our understanding of carbon storage and carbon dioxide emissions from lakes, and nitrous oxide emissions from streams, but will allow us to predict the effects of climatic change, and other human-related activities on greenhouse gas fluxes. Specific tasks included in this research program include 1) producing diffusive N2O budgets for several streams with varying levels of N inputs; 2) measuring rates of nitrification and denitrification and N2O production ratios (nitrification N2O:NO3-; denitrification N2O: N2) in short-term incubation experiments to help assess whether in-stream processes (rather than groundwater inputs) can account for N2O concentrations, and determining whether nitrification or denitrification is the primary source of N2O; and 3) assessing whether N-enrichment leads to increases in N2O fluxes.