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UBC Theses and Dissertations

Factors structuring microbial communities on marine foundation species Davis, Katherine


The microbiome of marine organisms contributes to host health and ecosystem processes like nutrient cycling. Despite the importance to healthy ecosystems, little is known about the dynamics and drivers of microbiome variation on marine hosts. In this dissertation, I use longitudinal studies and field-based transplant experiments to assess the factors associated with microbiome change on four coastal foundation species. In the intertidal macroalga Fucus distichus, I characterize temporal dynamics and microbiome variation on host individuals. I show seasonal turnover is a highly significant predictor of microbiome change. Local environmental conditions and host developmental stage also explain some microbiome variation. I test microbiome fidelity to geographically and phenotypically differentiated F. distichus by exposing hosts to new abiotic conditions and microbial source pools. No immediate shifts in microbiome composition occur in five-day transplant experiments, suggesting the established microbiome is buffered against short-term environmental change. I test whether host filtering modulates the shell microbiome of the mussel, Mytilus californianus, and find the microbiome is not specific to living mussels. Instead, it is associated with abiotic conditions that vary across geographic locations and elevation in the intertidal zone. In cultivated kelps, I test if outplanting kelp from controlled hatcheries to open ocean sites alters the microbiome and if host and abiotic factors are correlated with microbiome variation at cultivation sites. Host-species specificity was evident throughout the cultivation process and outplanting is followed by high microbiome turnover. Microbiome variation is more strongly correlated to season than abiotic differences between cultivation sites. Altogether, my findings suggest abiotic factors and host identity influence selective microbiome assembly on coastal foundation species. Seasonal microbiome turnover occurs in multiple hosts and coastal habitats, indicating microbes associated with the prevailing conditions may commonly replace existing members of the microbiome over weeks to months. Within host species, local abiotic conditions and host physiological state are correlated to microbiome variation. This research broadens our understanding of the tempo of microbiome turnover and factors predicting microbial community variation in marine foundation species. It provides necessary foundational knowledge for a holistic understanding of host and ecosystem response to changing oceans.

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Attribution-NonCommercial-NoDerivatives 4.0 International