Electronic Thesis and Dissertation Repository


Master of Science




Dr. Irena Creed

2nd Supervisor

Dr. Charles Trick

Joint Supervisor


Urea use has grown substantially in the past half-century, with urea now accounting for > 50% of nitrogen fertilizer applications worldwide. The shift from inorganic nitrogen fertilizers to urea-based sources has coincided with the reappearance of cyanobacteria blooms in freshwaters. Here, we examined urea as a nitrogen source for three bloom-forming cyanobacteria species. We found that (1) urea was consumed more rapidly relative to inorganic nitrogen substrates, suggesting that cyanobacteria exhibit a preference for urea; (2) urea was consumed in excess of cellular requirements; and (3) urea may offer cyanobacteria a competitive edge over eukaryotic algae by enhancing light absorption capabilities. These findings build on the growing body of literature demonstrating the importance of urea in freshwater eutrophication and satisfying the nitrogenous needs of cyanobacteria. As society’s reliance on urea is projected to escalate, it is important that we understand the unintended consequences of urea discharge on receiving freshwaters.