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MS Thesis Defense, Anastasia Dulskiy: Drivers of Microbial Diversity in the Temperate Coral Oculina arbuscula
November 3, 2022 @ 1:00 pm - 2:00 pm
Drivers of Microbial Diversity in the Temperate Coral Oculina arbuscula
|Disruption of the coral-algal symbiosis (bleaching) in response to anthropogenic stressors, such as warming and nutrient pollution, represents a significant threat to coral reefs worldwide. Corals are complex meta-organisms (“holobionts”) that host a variety of microbes, and recent evidence supports the role of bacteria in facilitating coral acclimatization to environmental stressors. Oculina arbuscula, an abundant scleractinian coral in the southeastern US, is characterized by a facultative symbiosis with photosynthetic algae (Symbiodiniaceae), allowing for investigation of coral host biology at varying levels of symbiosis. Here, I use 16S and ITS2 metabarcoding to investigate variation in coral-associated bacterial and algal communities in symbiotic (high symbiont density) and aposymbiotic (low symbiont density) O. arbuscula colonies along an inshore-offshore disturbance gradient in North Carolina. I found that O. arbuscula microbiomes significantly differed from the surrounding environment across sites and seasons, and that evenness of O. arbuscula microbiomes was higher in nearshore environments. Two bacterial taxa (Thiovulum and Burkholderiaceae) that have previously been suggested as disease indicators in tropical corals were present in high relative abundance across O. arbuscula samples, suggesting potential functional roles for these bacteria within the temperate coral holobiont. Lastly, coral-associated bacterial diversity and community structure did not differ between symbiotic states, but symbiont density was found to be a strong predictor of alpha diversity. Interestingly, the relationship between density and alpha diversity varied between sites, which I explain using a model incorporating ideas from resource allocation theory and the mutualism-parasitism hypothesis. Overall, this study provides a novel investigation of the microbial ecology of Oculina arbuscula, furthering our understanding of the coral-algal symbiosis and providing foundational knowledge of an ecologically important species to North Carolina hard bottom habitats.
Zoom link: https://unc.zoom.us/j/92429664710