Microbial diversity at a coastal time-series station in the Gulf of Maine. marine plankton metagenome

Cyanobacteria are important primary producers in marine ecosystems, providing food for the smallest protozoan grazers and serving as one of the first links in the marine food-web to organisms in higher trophic levels. We have characterized seasonal blooms of the marine cyanobacterium Synechococcus at a coastal time-series station in the Gulf of Maine on a weekly basis for two years. Synechococcus populations were enumerated by flow cytometry as well as clade-specific quantitative PCR to provide a high-resolution study of cyanobacterial bloom dynamics. Dilution experiments were conducted to estimate the impact of protozoa and viruses (cyanophage) on Synechococcus mortality throughout the bloom season. The diversity of microbial grazers was assessed via single-cell genomics, cell-sorting and amplicon sequencing of small populations of putative grazers, as well as whole-community amplicon sequencing. In addition to targeting grazer populations, 16S rRNA gene amplicon sequencing was performed to further characterize the microbial dynamics at our study site. Our study highlights the interactions among some of the smallest microbial grazers and their cyanobacterial prey and underscores the role of Synechococcus in supporting marine food-webs at certain times of the year.