Nitrogen fixation by the cyanobacterium Nostoc punctiforme in response to variation in nitrogen availability, temperature, and atmospheric CO2 concentrations

Author

Danielle A. Griffith, The University of Western OntarioFollow

Degree

Master of Science

Program

Biology

Supervisor

Dr. Zoë Lindo

Abstract

The predominant input of available nitrogen (N) in boreal forest ecosystems originates from moss-associated cyanobacteria, which fix unavailable atmospheric N₂, contribute to the soil N pool, and thereby support forest productivity. Although increases in N availability, temperature, and atmospheric CO₂ concentrations are expected in Canada’s boreal region over the next century, little is known about the combined effects of these factors on N₂ fixation by axenic cyanobacteria or the associated mechanisms. I assessed changes in N₂ fixation by Nostoc punctiforme under different global environmental change scenarios and examined correlations between the response and changes in growth, heterocyst percentage, and heterocyst activity. With available N present, N. punctiforme did not perform N₂ fixation or form heterocysts. Elevated CO₂ stimulated growth and N₂ fixation, but this result was influenced by a temperature-mediated growth cycle. Overall, my findings suggest a decrease in boreal N₂ fixation rates in response to global environmental change.

Recommended Citation

Griffith, Danielle A., "Nitrogen fixation by the cyanobacterium Nostoc punctiforme in response to variation in nitrogen availability, temperature, and atmospheric CO2 concentrations" (2014). Electronic Thesis and Dissertation Repository. 2309.
https://ir.lib.uwo.ca/etd/2309