UBC Theses and Dissertations
Effects of heatwaves on key ecological processes structuring early successional tidepool communities Konecny, Cassandra Angelica
With climate change, we are seeing an increase in mean temperatures globally. Perhaps of greater concern, however, is the associated increase in the frequency, magnitude, and duration of heat wave events. Through mass die offs, coral bleaching, and species range expansions and contractions, heatwaves have had large impacts on marine ecosystem and their function. While we have an understanding of how communities have been altered by naturally occurring heatwaves, we have little understanding of what factors are important in determining the response of a system to extreme heat events. In order to better predict the response of marine ecosystems to extreme heat events we must understand how extreme temperatures interact with key ecological processes. The goal of this thesis was to determine how heatwaves, in conjunction with key ecological processes, such as herbivory and dominant foundation species, alter community composition and function. I tested this using artificial tidepools in Burrard Inlet, British Columbia as a study system and manipulated temperature in situ through the design of a novel temperature manipulation system: the SAUTE. In chapter 2, I test how regular heat events of different intensities and herbivore density affect community composition through a 2-month field manipulation. My results demonstrate that tidepool communities in the Pacific Northwest may not be impacted directly by regular increases in maximum daily temperatures by 2-4ºC throughout the summer, but that indirect effects through the loss of herbivore grazers could have impacts on community composition. In chapter 3, I ask how a late summer, longer duration heatwave influences community composition in tidepools and if this effect is dependent on the dominant foundation species present. The data that I present suggests that, though there were few direct impacts the heatwave on tidepool assemblages, the dominant foundation species was an important determinant of community composition and diversity. While I only observed a slight decrease in the abundance of foundation species with heating, if extreme heat events modify ecological processes, such as herbivory, that create and allow different habitat types to persist, then they could have large indirect effects on tidepool communities.
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