University of Western Ontario - Electronic Thesis and Dissertation Repository


Master of Science




Dr. Irena F. Creed


The role of the micronutrient iron in the regulation of cyanobacteria dominance and cyanotoxicity is poorly understood. Iron is required for important metabolic pathways, including both phosphorus (P) and nitrogen (N) assimilation, and low levels of this element may influence the assimilation of the macronutrients. The hypothesis tested was that cyanobacteria produce and utilize siderophores and toxins in low iron conditions to scavenge iron, when P and N are not limiting algal growth, providing some cyanobacteria with a competitive advantage over other algal species. Among the naturally eutrophic lakes studied, cyanobacteria were dominant at low iron (>pFe19) concentrations (Spearman r = 0.73, p=0.004). Under these low iron conditions, the concentration of hydroxamate siderophores was significantly related to cyanobacteria biomass (r2=0.81, p<0.001), and the concentrations of extracellular microcystin were significantly correlated to the concentrations of hydroxamate siderophores (r2=0.98, p<0.001). These findings provide support for iron regulation of cyanobacteria harmful algal blooms (cyanoHABs). Lake management programs can work to mitigate and prevent future cyanoHAB occurrences through the regulation of iron in naturally eutrophic lakes.