UC Irvine

Global change is impacting ecosystems worldwide, driving widespread biodiversity loss and disrupting a broad spectrum of ecological processes. Ecosystems are organized by interactions among species, which dictate everything from species composition to how biomass and energy flow through the system. Only by studying the effects of global change in the context of existing ecological structures and species interactions can the impacts be fully understood. My dissertation research has focused on the ways in which climate change affects the ecological roles of species: whether by altering the relative importance of common species in ecosystems, directly impacting ecosystem function via species loss, or accelerating the proliferation of invasive species. In my first chapter, I consider the potential for an abundant marine producer to engineer habitat for other species and how that role may shift with climate change. I found that this dominant alga raised pH when in isolation but not in the context of a tide pool community, suggesting that the most abundant species do not necessarily affect the impacts of global change in coastal ecosystems. My second chapter focuses on the contributions of dominant species to ecosystem multifunctionality in coastal areas, as well as the potential effects of dominant species loss on ecosystem multifunctionality. I found that a dominant producer and a dominant consumer had largely opposite effects on ecosystem function and that the loss of the producer altered the functional impact of the consumer, suggesting that species loss may impact ecosystem multifunctionality beyond the functional footprint of the individual species. In my third chapter, I identified the ways that climate change is likely to influence factors that historically limited species invasion in high-latitude, marine ecosystems. Each of these invasion barriers is likely to become increasingly porous, potentially increasing invasions in high-latitude areas in decades to come. The results of this research could be incorporated into (1) conservation plans, sharpening the focus on species which have the greatest ecological impact, either by stabilizing environmental conditions or by driving ecosystem function, and (2) invasive species management strategies, by highlighting the increasing vulnerability of high-latitude ecosystems to species invasion under warming conditions and stressing the importance of international cooperation in monitoring programs.