Yean Das

Heterotrophic Prokaryotes (HP) contribute the largest fraction of living biomass (~90%) in the ocean and play a vital role in global biogeochemical cycles through the remineralization of dissolve organic matter (DOM) and its transport to higher trophic levels. Flow cytometric enumeration of HP typically exhibits two distinct subpopulations with similar side scatter (SSC, related to cell size) but different green fluorescence intensity that has been shown to be proportional to cell DNA content. Thus, they are commonly referred to as high nucleic acid fluorescent (HNA) and low nucleic acid fluorescent (LNA) populations. HNA are often associated with productive environment whereas, LNA are abundant in oligotrophic regions, suggesting these populations have distinct physiology and metabolic capacity, if true their relative distributions have important implications for biogeochemical cycling within marine systems. However, little is known about what processes affect their relative distributions over broad geographical scales.

Using field samples collected from the North Atlantic, Yean is working to unravel the role that physical mixing processes play in structuring the relative distribution of two marine heterotrophic prokaryote subpopulations. Specifically, Yean's research focuses on how physical processes such as seasonal changes in stratification and mesoscale eddies influence the composition of microbial communities, their growth and mortality processes and ultimately the flow of carbon through the marine ecosystems.