Karthik Anantharaman (University of Michigan, Ann Arbor)

Hydrothermal plumes are zones where the reaction of hydrothermal vent fluids with sea water serves as an important habitat for chemolithotrophic microbial communities. Hydrothermal plumes are composed of two distinct parts, namely: 1) The initial rising plume which is comprised of vent fluids that mix with the sea water and are carried upwards in a plume. 2) The laterally dispersing neutrally buoyant plume. Thus, hydrothermal plumes serve as a natural environmental geochemical gradient to support microbes of various physiologies.

Most sampling efforts in the past focused on the neutrally buoyant plume, however, recent advancements in sampling (Breier et al. 2009) have allowed us to take a full suite of samples through the hydrothermal plume. Accordingly, we collected a set of 80 microbial samples in addition to samples for geochemical and mineralogical analyses across the hydrothermal plumes of five vent fields at the Eastern Lau Spreading Center(ELSC) in 2009. 

For my Ph. D thesis, I have proposed to study the microbial ecology of hydrothermal vent systems at the ELSC. Some of the key questions that I am investigating during the course of my research are: 1)What are the compositions of microbial communities in hydrothermal plumes and where are they derived from? 2) How do microbial communities evolve through the hydrothermal plume with co-evolving geochemistry? 3) How do microbes mediate geochemical reactions in the rising and neutrally buoyant plumes?

My approach involves the use of metagenomics and pyrosequencing of 16s rRNA genetags to address the above questions and also correlate findings with associated geochemistry and mineralogy.

Contribution to synthesis

Although there have been a number of recent advances in recent years in the microbiology of hydrothermal plumes (e.g. Huber et al. 2007, Dick et al. 2009, Dick et al. 2010), major gaps still exist in our knowledge of microbial communities. Considering how microbial processes may be critical in determining the fate of hydrothermal effluents and their influence on global ocean chemistry, it is important that we understand the nature and composition of microbes inhabiting hydrothermal plumes. At the meeting, I will present preliminary results of tag–sequencing across five vent fields of Lau Basin. Taking into account the interdisciplinary nature of this research and the interactions with other microbiologists, geochemists and mineralogists, it is my goal to work with the larger community to integrate our efforts in synthesizing the microbiology, geochemistry and mineralogy of hydrothermal plumes.

REFERENCES

Breier, J.A., C.R. Rauch, K.McCartney, B.M. Toner, S.Fakra, S.N. White, and C.R. German (2009). An optical sensor-compatible, suspended particle rosette multi-sampler for discrete, biogeochemical sampling in low particle density waters, Deep Sea Research I, 56: 1579-1589.

Dick, G.J., B.G. Clement, S.M. Webb, F.J. Fordrie, J.R. Bargar, And B.M. Tebo (2009). Enzymatic microbial Mn oxidation in the Guaymas Basin deep-sea hydrothermal plume. Geochimica et Cosmochimica Acta, 73:6517-6530.

Dick, G.J., and B.M. Tebo (2010). Microbial diversity and biogeochemistry of the Guaymas basin hydrothermal plume. Environmental Microbiology, 12:1334-1347.

Huber J.A., Mark Welch D.B., Morrison H.G., Huse S.M., Neal P.R., Butterfield D.A. and Sogin M.L. (2007). Microbial population structures in the deep marine biosphere. Science, 318(5847):97-100.