Islands in the Sea: the Patchy Distribution and Physiological Poise of Vent Microbes and the Implications for Carbon Cycling

Abstract:

The last thirty-five years have been a watershed for deep-sea microbiology. The discovery of hydrothermal vents and their extraordinarily productive communities, along with the discovery of the deep subsurface biosphere and their slow-growing, energy-starved microbial communities have changed our ideas about the nature and extent of microbial life in the deep sea. Moreover, the avent of genomics and other -omics further reshaped our understanding of microbial evolution and ecology.

Nevertheless, after decades of research, there remain a number of long-standing questions regarding the distribution and activity of microbes in situ. For example, we know that hydrothermal vents are energy-rich environments, and the energy for microbial primary productivity at hydrothermal vents is primarily derived from compounds that are in disequilibria between hot, reduced thermal fluids and the ambient, oxidized bottom seawater. However, we have a rudimentary understanding of how microbes are distributed within this geochemical gradient, and how temporal variability in fluid flow and even eruptions influences primary and secondary productivity. At the other extreme, deep subsurface environs can be very energy limiting, and microbes are seemingly limited in their access to either electron donors (e.g. dissolved organic matter, or DOM) or electron acceptors (e.g. oxygen). Yet here, recent data revealed patterns of microbial activity in the deep subsurface that are inconsistent with our conventional wisdom, and suggest that the availability of electron donors/acceptors may be greater than previously thought.

Here we present our latest data, as well as the technologies and methods that allow us to synoptically measure geochemistry and microbial processes (community composition and gene expression) over space and time. Our findings reveal striking patterns of microbial distribution, gene expression and activity within a vent field and in the deep subsurface that begin to shed some light on the relationship between microbial ecology and physiology and biogeochemical cycles.