How much energy does H2 supply to soil microbes?

I presented a poster at the at the Ecology of Soil Microorganisms conference in Prague, 2011 on the role of soil microorganisms in dominating the fate of atmospheric molecular hydrogen (H2). Recent work has linked atmospheric H2 uptake to a novel high-affinity [NiFe]-hydrogenase expressed in active Streptomyces sp. cells, and is perhaps not driven by abiotic hydrogenases as was previously thought. Consequently, atmospheric hydrogen may be a 60-85 Tg yr-1 energetic supplement to microbes in Earth’s uppermost soil horizon. To understand the role of this supplement to the soil microbial ecology, this work explores the following questions:

  1. What is the importance of atmospheric H2 energy to soil microbial communities relative to carbon substrates?
  2. How might this energetic supplement change with changes in anthropogenic H2 emissions?
Ecology of Soil Microorganisms poster
Ecology of Soil Microorganisms

Is H2 an upper atmospheric tracer?

I presented a poster at the 2010 American Geophysical Union General Assembly on H2 as a “mesotracer.” A rare glimpse into the chemical and dynamical evolution of the Arctic polar vortex is provided by a suite of in situ balloonborne measurements. A set of mesospheric tracers observed in the late vortex validate theoretical mesospheric chemical profiles, which is especially valuable for the case of mesospheric H2. Early vortex mesospheric profiles are constructed to explain mixing in tracer-tracer space. Expanding a model to incorporate three mesotracers, H2, CO, and SF6, instead of only one, will increase our ability to constrain estimates of the amount of mesospheric air that descended to stratospheric altitudes by vortex end.

AGU 2010 - Chemical tracers in the upper atmosphere
AGU 2010 Poster – Chemical tracers in the upper atmosphere

MBL microbial diversity course

Anabaena heterocyst and associated epibiont
Anabaena heterocyst and associated epibiont

In the summer of 2010, I spent six inspiring, challenging, and chaotic weeks at the Marine Biological Laboratory Microbial Diversity Course in Woods Hole, MA. I hoped to take full advantage of the opportunity granted by course directors Steve Zinder and Dan Buckley of Cornell to plunge head on into the world of microbiology. I was eager to learn the theory and hands-on methods to study the microbial world, which has such a profound impact on atmospheric composition, and this course gave me a chance to explore my interests in a way not offered anywhere else. Continue reading “MBL microbial diversity course”

Instrument deployment at Harvard Forest

Instrument deployment to Harvard Forest
Instrument deployment – Harvard Forest

After over a year of designing, building, and testing a custom instrument system to measure fluxes of molecular hydrogen (H2), I deployed the system to the Harvard Forest Long Term Ecological Research site in Petersham, Massachusetts ( With the instrument installed, I will measure hydrogen fluxes for a year to determine the seasonal dynamics of H2 cycling in this mixed deciduous forest, and in particular, to characterize the strong soil sink for atmospheric H2.

The instrument shed was tight, and I was packing a lot of equipment. But the move in day was a successful and fun experience thanks to the help of colleagues at Harvard University.

This short documentary created by fellow PhD student Ryan Abernathey highlights the challenges and excitement of move-in day. But the work has only just begun…

Laura at Harvard Forest from Ryan Abernathey on Vimeo.