UBC Theses and Dissertations

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UBC Theses and Dissertations

The effects of morphology and neighbouring seaweeds on macroalgal microbiota Chen, Melissa


Macroalgae (seaweeds) have an intimate relationship with their microbial symbionts. Microbial communities associated with macroalgal surfaces (epibiota) are generally host-specific and, historically, there has been great interest in the role of biological compounds and chemical warfare in microbial community assembly on seaweeds. However, the interaction between seaweeds and their environment may also influence community assembly of their microbiota. In my thesis, I conduct two experiments that ask how factors not related to seaweed chemistry influence microbial community assembly. First, I ask whether the interaction between flow and seaweed morphology affects the settlement and structure of microbial biofilms. In this project, I test whether three common algal morphologies select for differential biofilm communities using artificial macroalgae units (AM units) made out of latex. I find that morphology does affect initial microbial settlement and community structure, but that eventual dominance of substrate specialists (in our case a latex degrader) swamps the influence of morphology in long-term biofilms. The second chapter of my thesis asks whether macroalgae affect the microbial epibiota of each other. To test this, I co-incubate Nereocystis leutkeana meristem fragments with different species of mature macroalgae. I find that although water column communities change significantly when incubated with mature macroalgae, seaweed surface communities are far more resistant to change. Overall, these results support the idea that the seaweed surfaces are highly selective, and demonstrate that modulations on seaweed microbiota operate within an overarching paradigm of species specificity. With these experiments, I hope to contribute to the larger body of knowledge on seaweed-microbe associations and improve understanding of how, and why, we find the observed microbiota on seaweed surfaces.

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