Electronic Thesis and Dissertation Repository


Master of Science



Collaborative Specialization

Global Health Systems in Africa


Dr. Irena Creed


The frequency and intensity of cyanobacteria blooms are increasing globally. The interacting effects of environmental drivers, including increased temperature, altered precipitation, reduced acidification-with associated shifts in nutrient limitation- and increased dissolved organic matter loads to lakes are predicted to create favourable environmental conditions for cyanobacteria in northern lakes. This prediction was tested in 28 nutrient-poor Swedish lakes over 16 years (1998-2013). Increases in cyanobacteria abundance were identified in 21% of the study sites, composed mostly of increases in three specific genera: Merismopedia, Chroococcus, and Dolichospermum. Increases in temperature favoured Merismopedia dominance in lakes with low pH and high nitrogen to phosphorus ratios. In contrast, higher pH and associated acidification recovery favoured Chroococcus and Dolichospermum. In addition, increases in dissolved organic matter loads suppressed Chroococcus while promoting Dolichospermum. These findings highlight the complex nature of global changes on cyanobacteria prevalence and reveal how specific genera of cyanobacteria may be able to benefit from global changes and potentially pose a management risk to freshwater ecosystems.