Marine Microbial Ecology and Biogeochemistry
Research areas
Viruses are the most abundant biological entities in the ocean, and the majority infect marine microorganisms, including archaea, bacteria, and protists. During infection, viruses manipulate host metabolism, altering cellular composition and stimulating the release of dissolved chemical cues from intact infected cells, which can elicit chemotactic responses from neighboring microbes. Thus, virus-infected cells have the potential to serve as long-lasting (i.e. hours) point sources of valuable nutrients in nutrient poor waters of the surface ocean. In addition, the release of chemoattractants or chemorepellents from intact, virus infected cells has the potential to alter nano, micro, and mesozooplankton predation rates and carbon and nutrient flux among trophic levels. We use a combination of video microscopy, microfluidics, metabolomics, transcriptomics, flow cytometry, stable isotope tracing, and lab and field based manipulative experiments to understand viral redirection of host metabolism and consequent impacts on planktonic food web interactions and carbon and nutrient cycling.
The biological carbon pump, mediated by surface ocean phytoplankton, enables the transport of atmospheric carbon dioxide to dark, interior waters where it is sequestered from exchange with the atmosphere on timescales of months to millenia. At the most fundamental level, biological productivity and organismal interactions drive the formation and degradation of carbon-rich particulate matter. We are interested in how virus-host and predator-prey interactions influence the formation and break-up of phytoplankton cellular aggregates, and the resulting influence of particle composition and size distributions on feeding rates and behaviors by mesozooplankton. To this end, we use a combination of lab and field based experimental systems and various particle imaging techniques to understand how microbial interactions drive marine particle composition, size, and sinking rates.
Dissolved chemical cues in ocean waters drive myriad microscale plankton interactions, ultimately controlling ecosystem-scale processes such as biomass production, nutrient cycling, and carbon fixation and remineralization. We are interested in both identifying relevant chemical cues and quantifying the impact of such cues on trophic level carbon, macro-, and micronutrient transfer. We are particularly interested in the potential role of vitamins and other secondary metabolites as chemoattractants or repellents and resulting impacts on organismal interactions and micronutrient exchange.
The Floge Lab: Unraveling Marine Microbial Ecosystems and Biogeochemical Dynamics
The global ocean, covering over 70% of Earth’s surface, plays a critical role in sustaining life. Drifting photosynthetic microorganisms in the ocean, called phytoplankton, take up atmospheric carbon dioxide and produce oxygen and organic carbon compounds utilized by other organisms. These microscopic organisms carry out approximately half of Earth’s primary productivity (roughly equal to that by land plants), supporting life in the ocean, providing oxygen to the atmosphere, and removing atmospheric carbon dioxide. Due to their small size and underappreciated role in global photosynthesis, phytoplankton are sometimes called the invisible forest. Phytoplankton are responsible for taking up nearly one quarter of anthropogenic fossil fuel based carbon dioxide emissions, transporting that carbon into ocean waters where it can be sequestered, thereby reducing global climate warming and associated negative impacts. However, during this time of rapid global change, it is unclear how ocean microbes will respond to continued ocean warming and acidification and the resulting impact on sequestration of atmospheric carbon dioxide.
Microorganisms are the engines that both drive Earth’s biogeochemical cycles and control health and disease states in macroorganisms. Microbes (viruses, archaea, bacteria, and protists) thrive within complex communities and communicate via dissolved chemical cues. Thus, microbial ecology is chemical ecology. Our research seeks to understand the diverse chemical cues that drive interactions among marine microbes and their environment and ultimately control global scale cycles of carbon and nutrients. Current projects include identification of chemical cues released by virus-infected phytoplankton and resulting chemotactic responses by bacteria and protists, the role of viruses in vitamin cycling and cyanobacterial biofilm formation, and biogeochemical consequences of viral infections under different climate scenarios.
