Deep-sea hydrothermal plumes host dynamic interactions between microbial communities and geochemical processes: hydrothermal inputs fuel enhanced microbial activity, while microorganisms catalyze geochemical transformations and thus mediate the transfer of material between vents and oceans. In addition, plumes are conduits for transport of microorganisms and larvae and thus represent biogeographic connections both between environments within vents fields and between different vent sites. Recent results highlight the intimate nature of interactions between biology and geochemistry in plumes (Bennett et al. 2008, Dick et al. 2009, Dick and Tebo 2010, Toner et al. 2009, Tagliabue et al. 2010) while highlighting gaps in understanding of the microorganisms that determine rates and end-products of biogeochemical processes.

Key questions that remain largely unanswered include: (1) what is the nature of microorganisms that are active in deep-sea hydrothermal plumes (e.g. derived from seafloor vs. background deep sea), and how does this vary within plumes (e.g. rising versus neutrally-buoyant) and across geochemical gradients? (2) To what extent do microbes influence biogeochemical processes in terms of rates, speciation, and end-products (e.g. biogenic minerals)? (3) Which hydrothermal inputs serve as the major energy sources for chemolithoautotrophy in plumes, and what are the implications for feedbacks onto biogeochemical functions? Such information is a prerequisite if we are to reach a deeper understanding of the impact that deep-sea vents have on the chemistry and biology of the oceans.

Our ability to address such questions has been limited by technical challenges but new tools provide great promise for breaching these barriers. In particular, advances in sampling (Breier et al. 2009) and investigating chemical speciation (Toner et al. 2009) and microbial communities (Dick et al. 2010) provide new windows into plume processes and the spatial, temporal, and biological dimensions in which they occur. My laboratory has been applying metagenomic and metatranscriptomic approaches to characterize the metabolic potential and function of plume microbes; such approach hold enormous potential for addressing the questions above.

Given the importance of plume microbial biogeochemistry, its interdisciplinary nature, the fact that it has been understudied for some time, and the promise of recent results and approaches, this topic deserves a prominent role in R2K discussions and synthesis efforts.

REFERENCES

Bennett, S.A., Achterberg, E.P., Connelly, D.P., Statharn, P.J., Fones, G.R. and Gernian, C.R. (2008). The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes. Earth and Planetary Science Letters, 270: 157-167.

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. Fodrie, J.R. Bargar, and B.M. Tebo (2009). Enzymatic microbial Mn oxidation in the Guaymas Basin deep-sea hydrothermal plume. Geochimica 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.

Tagliabue, A., Bopp, L., Dutay, J.-C., Bowie, A.R., Chever, F., Jean-Baptiste, P., Bucciarelli, E., Lannuzel, D., Remenyi, T., Sarthou, G., Aumont, O., Gehlen, M. and Jeandel, C., (2010). Hydrothermal contribution to the oceanic dissolved iron inventory. Nature Geosci, 3: 252-256.

Toner, B.M., Fakra, S.C., Manganini, S.J., Santelli, C.M., Marcus, M.A., Moffett, J., Rouxel, O., German, C.R. and Edwards, K.J. (2009). Preservation of iron(II) by carbon-rich matrices in a hydrothermal plume. Nature Geoscience, 2: 197-201.