EEPS Colloquium: Anne Dekas

Microbial Carbon and Nitrogen Cycling in the Deep Sea

Microorganisms play an essential role in biogeochemical cycling, today and throughout time. The deep sea—defined here as >200 m water depth—is one of the largest habitats for microbial life on Earth. However, it is poorly explored relative to the surface ocean, and the diversity and activity of microorganisms in this realm are largely uncharacterized. The goal of my research is to understand the activity of microbes in the deep sea: who is doing what, how much, and how does it affect larger food webs and biogeochemical cycles? In this talk, I will describe how we employ DNA sequencing and stable isotope tracer experiments to explore deep-sea microbial carbon and nitrogen cycling with a focus on nitrogen fixation and chemoautotrophy. Additionally, I will describe advances in nanoscale secondary ion mass spectrometry (nanoSIMS) to quantify anabolic activity in uncultured microorganisms on the single-cell level.  Together, our work reveals that deep-sea microbial cells are more active than previously assumed, and that diverse deep-sea taxa are likely important contributors to organic nitrogen and carbon production at depth.

Host: David Fike