Research Biogeochemist
Smithsonian Environmental Research Center
Smithsonian Institution
PO Box 37012
MRC 540
Washington, D.C. 20013-7012
megonigalp@si.edu
Research Interests
The carbon cycle is a powerful integrator of physiological function across levels of ecological complexity ranging from cells to ecosystems. I study the carbon cycle of upland and wetland ecosystems as a means of understanding their response to stressors such as flooding and climate change. Because plants are the major source of organic carbon in ecosystems and microbes are a major sink, my research encompasses both groups of organisms. I am interested in how the different forms of carbon produced by plants (e.g. carbohydrates, cellulose, lignin) influence microbial metabolism, the unique characteristics of the rhizosphere as an environment for microbial communities, and the interaction of these processes with physical variables such as flooding, salinity, and soil mineral composition. My research program currently has two primary components: feedbacks between climate change and terrestrial ecosystem function and plant-microbe interactions in the rhizosphere.
Current Research Projects
I am currently collaborating with Dr. Bert Drake of SERC to understand the effects of elevated carbon dioxide in the atmosphere on carbon sequestration and methane production in wetland ecosystems. We are particularly interested in the effects of an enhanced plant-carbon supply on microbial community composition and activity. Although they account for just 10% of the terrestrial surface, wetlands hold 30% of the global soil carbon pool, an amount equivalent to the carbon stored in all living vegetation. This work is funded by the Department of Energy.
I am investigating the microbial ecology of the soil zone immediately surrounding plant roots (i.e. the ‘rhizosphere’). The rhizosphere is ‘hot spot’ of microbial activity because plants are excellent sources of organic carbon (i.e. energy) and other resources that microbes require. A primary focus of my work is the influence of iron-oxidizing and iron-reducing bacteria on the cycling of this important element in wetlands. The work has involved isolating and characterizing iron-metabolizing bacteria using molecular techniques, and testing hypotheses about the nature of a rhizosphere-organized iron cycle. This work is funded by NSF.
Recent Publications
Neubauer, SC, D Emerson, and JP Megonigal. 2002. Life at the energetic edge: Kinetics of circumneutral iron oxidation by lithotrophic iron-oxidizing bacteria isolated from the wetland-plant rhizophere. Applied and Environmental Microbiology 68: 3988-3995.
Vann, CD and JP Megonigal. 2003. Effects of Elevated CO2 and Water Depth on Methane Emissions: Comparison of a Woody and Non-woody Wetland Plant Species. Biogeochemistry 63: 117-134
Darke, AK and JP Megonigal. 2003. Control of sediment deposition rates in two mid-Atlantic coast tidal freshwater wetlands. Estuarine and Coastal Shelf Science 57 (1): 255-268
Craft, C, P Megonigal, S Broome, J Cornell, R Freese, J Stevenson, L Zheng and J Sacco. 2003. The pace of ecosystem development of constructed Spartina alterniflora marshes. Ecological Applications (in press).
Weiss, JV, D Emerson, SM Backer and JP Megonigal. 2003. Enumeration of Fe(II)-oxidizing and Fe(III)-reducing bacteria in the root zone of wetland plants: Implications for a rhizosphere iron cycle. Biogeochemistry (in press).