Bacterial dormancy, bacterivory, and bacterioplankton diversity in the ocean

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Bacterioplankton are abundant, phylogenetically diverse, and physiologically versatile organisms. Many studies have demonstrated that the majority of marine bacterioplankton are viable but physiologically inactive or dormant. Grazing by protists is thought to be the main cause of mortality of inactive bacterioplankton. It is a long-standing question how a majority of dormant bacterioplankton can persist in the absence of apparent physical shelters from grazers. The PIs will examine whether bacterioplankton dormancy reduces the probability of being grazed, and in this way maintains a reservoir of genetic diversity, that enables rapid community-level responses to changing environmental conditions. This will require the use and further development of innovative technology, combining fluorescence-activated cell sorting with community and single-cell molecular analyses. This cutting-edge technology significantly enhances the scientific community's capability to address fundamental questions that were previously unattainable due to methodological constraints. A coastal station in the Gulf of Maine and an oligotrophic station in the Sargasso Sea will be studied during the annual plankton succession, providing information on the temporal and spatial variability in microbial trophic interactions. The project will support one postdoctoral associate and at least two undergraduate students. The undergraduate students will work with the Bigelow Laboratory for Ocean Sciences Education and Outreach team to ready their findings for web-based dissemination to non-scientists. Content will be accessible on the Bigelow Laboratory website, linked from the NSF-funded resource "Cycling through the Food Web" (http://www.bigelow.org/bacteria/), which promotes understanding of microbial food webs, biodiversity, and global nutrient cycling for middle and high school audiences. The PIs will also work closely with the Centers for Ocean Sciences Education Excellence-Ocean Systems (COSEE-OS) to aid learners, particularly those in rural and inland areas, to gain a better understanding of the role of the oceans in the greater earth system.