UC San Diego

Marine microbial communities consist of millions of species engaging in complex interactions with one another and with their environments over a variety of time scales. The field of marine microbial ecology has only begun to understand the true extent of the diversity – both of species themselves (which include members of the bacteria, archaea, and eukaryotic protists) and the ways they interact with one another. Many studies of marine species diversity represent snapshots of a community but do not capture the temporal dynamics of its members. In this dissertation I illustrate how the microbial community at a single site changes over time by collecting high-frequency samples at the Scripps Pier (La Jolla, CA, USA). I leverage amplicon sequencing to describe the bacterial and eukaryotic communities and find there to be detectable, occasionally very large, fluctuations, some with seasonal patterns and others on the order of days. I use this high-resolution sequence data to: identify putative grazers of the marine cyanobacteria Synechococcus (Chapter 1), characterize fine-scale changes in Synechococcus microdiversity over the course of blooms (Chapter 2), and suggest new Syndiniales parasite-host interactions at our site (Chapter 3).