Iron-Regulated Cyanobacterial Predominance And Siderophore Production In Oligotrophic Freshwater Lakes, Ryan J. Sorichetti

Electronic Thesis and Dissertation Repository

The frequency and intensity of cyanobacterial blooms (cyanoblooms) is increasing globally. Contrary to existing phosphorus (P) and nitrogen (N) paradigms describing cyanobloom proliferation in eutrophic (nutrient-rich) freshwater lakes, many of the recent cyanobloom reports pertain to oligotrophic (nutrient-poor) freshwater lakes with no prior history of cyanobloom occurrence. There exists a critical research need to re-visit existing conceptual models, identify regulating factors currently unaccounted for and improve our ability to effectively detect and measure cyanobacterial toxins (cyanotoxins) in lakes. Iron (Fe) is required in nearly all pathways of cyanobacterial macronutrient use, though its direct role in regulating cyanobacterial biomass is not …

Tree Seedling Establishment In Response To Warming And Nitrogen Addition In A Temperate Old Field, Bryana D. Mcwhirter

Electronic Thesis and Dissertation Repository

Climate change and increased atmospheric nitrogen deposition over the next century may alter the ability of woody species to germinate and compete with grasses and forbs in temperate old fields. To investigate the responses of seed germination and seedling growth to warming and nitrogen addition, I transplanted seeds and seedlings into plots of a field experiment and conducted a greenhouse experiment. The combination of warming and nitrogen allowed seeds to germinate earlier, although there was no effect on final germination. In the greenhouse nitrogen increased seedling growth, and warming had little effect. However, in the field, warming significantly decreased the …

Overwintering Diet Quality And Timing Of Initiation Of Breeding In The Deer Mouse (Peromyscus Maniculatus), Lindsey Valliant

Electronic Thesis and Dissertation Repository

Timing of breeding in seasonal environments is important in population dynamics, but it is not always known what cues animals use to time breeding. In northern deer mice (Peromyscus maniculatus) at Kananaskis, Alberta, Canada, early seasonal births are related to overwinter protein supplementation. It is not however known if natural variation in diet quality has the same effect. I hypothesized that yearly winter arthropod availability would influence yearly spring breeding. I predicted that the mean date of initiation of breeding in the population would be related to overwinter diet quality, indicated by ¹⁵N enrichment of hair of …