Tag Archives: talk

Undergraduate Researcher Shersingh’s SURGE Experience

Congratulations to visiting undergraduate researcher Shersingh Joseph Tumber-Davila on completing and thriving in the demanding eight-week Summer Undergraduate Research in Geoscience and Engineering (SURGE) program! Shersingh came to the Welander lab with a strong background in environmental research (news article) from his home institution of the University of New Hampshire. SURGE is a competitive earth science research and graduate school preparation program, which is specifically designed to recruit students of diverse backgrounds from other universities across the country. I was amazed at the number of activities the program had for the students including GRE test preparation, faculty seminars, career and grad school panels, and field trips. This was all while performing graduate-level research including a oral and poster presentation at the end of the program. Shersingh approached all these demands with amazing energy and attitude, which we’d really like acknowledge!

SURGE student Shersingh

SURGE student Shersingh

In Shersingh’s research, he asked whether microbe-mediated hydrogen (H2) uptake support C mineralization in soils. Soils are a strong sink for atmospheric H2, which is presumably used by soil microorganisms to fuel their energy metabolism. In addition, emissions of H2 have grown since the industrial revolution, so the availability of H2 energy to soil microbes likely also increased. Shersingh tested the influence of excess H2 on the ability of soil microbes to mineralize soil carbon for a variety of carbon substrates, especially those that can be energy intensive (e.g., lignin and lignocellulose). He used Streptomyces ghanaensis as a model organism containing high affinity hydrogenase (H2 uptake) and laccase (lignin breakdown) genes. By measuring carbon dioxide respiration rates and intermediate products involved in the breakdown of lignin and lignocellulose, we found evidence for increased breakdown of lignocellulose (straw) with elevated levels of H2. This may point to a  link between the H2 and C biogeochemical cycles in soils that will be interesting to pursue further. This project is in collaboration with Stanford postdoc Marco Keiluweit who specializes in soil carbon cycling.

Thesis Defense!

I defended my thesis entitled “Field Measurement of the Fate of Atmospheric H2 in a Forest Environment: from Canopy to Soil” on October 4, 2012.

It was an incredible relief to finish the thesis document itself (link to .pdfCarl-Gustaf Rossby Prize for best PhD thesis in PAOC for the year). I really enjoyed preparing and giving my thesis defense presentation. It’s not often that one gets to present the culmination of six years of hard work and personal development to colleagues, family, and friends. I am grateful for mentorship from my advisor Ron Prinn, my thesis committee (Steve Wofsy – Harvard, Bill Munger – Harvard, Tanja Bosak – MIT, Colleen Hansel – WHOI, Shuhei Ono – MIT), and many others along the way!

I am continuing at MIT for a short (approximately 9 month) postdoctoral position with Ron Prinn to translate the work described in my thesis to publications. I am currently exploring possibilities for a postdoctoral position at the intersection of microbial ecology and atmospheric chemistry (trace gas cycles or aerosols) by searching advertised positions and writing fellowship proposals.

I survived the AGU 2011 Fall meeting

I just returned to Boston after the six weeks of travelling. My two weeks in California, filled with conferences and colleagues, was quite different from the intensive and somewhat isolated period spent in India.

Presenting my poster at AGU – one of 12,000+ posters

First stop was San Diego, where I attended the 44th Meeting of Advanced Global  Atmospheric Gases Experiment (AGAGE) Scientists and Cooperating Networks at the Scripps Institute of Oceanography in La Jolla. Anita Ganesan’s instrument in Darjeeling may pave the way for the first AGAGE site in India, so the crowd was eager to hear her describe our success in deploying her instrument. Her dedicated and diligent work is paying off as she is collecting some of the first high precision direct greenhouse gas measurements in India.

I gave a talk at the AGAGE meeting on my recent work on the flux of H2, CO2 and COS between the soil and atmosphere at Harvard Forest. I focus on the persistence of soil-atmosphere exchange of trace gases across snowpack, which insulates the soil microbial community from freezing air temperatures while allowing trace gases  to diffuse through the porous snow matrix. I’m interested in how strongly the biogeochemical cycling continues throughout the winter and in comparing the behavior of the different cycles in the low temperature ‘incubator’ beneath the snow. Continue reading