Research

  
 

My research interests lie in the area of aquatic biogeochemistry and are directed toward determining the rates of processes involved in carbon cycling. Carbon is the basic building block of life, and I am interested in how organic matter is produced, degraded, transported and utilized. One of my main tools for studying carbon cycling is stable isotopic analysis.

Hypesaline microbial mats

Modern microbial mats are thought to be analogues for early life on earth; the remnants of this early life are preserved in layered carbonate structures called stromatolites. Along with colleagues from NASA Ames Research Laboratory, we have been investigating carbon cycling and flow through hypersaline microbial mats collected in Baja California. Initial work has focused on isotopic analyses of the various organic and inorganic carbon pools under both natural and experimentally manipulated environmental conditions, taking advantage of the NASA Ames greenhouse facility. Because of this facility’s ability to maintain mats, experimental manipulations can occur to help us understand conditions on early Earth, as well as on possible conditions on other planets harboring life. Planned work includes determining and understanding the factors involved with methane production within these mats, as well as in other high salinity sites (such as the Don Edwards National Wildlife Refuge in northern California), since methane is among the most promising biosignature gases being considered for life detection space missions such as NASA’s Terrestrial Planet Finder. We also plan to investigate the cycling of organic matter and the coupling between these very productive mat system and the overlying water column under natural conditions in the salt ponds in Baja California.

Fluxes of methane

Methane is a globally significant greenhouse gas (approximately 25X more potent than carbon dioxide) that is produced by obligately anaerobic bacteria. The largest source of methane to the atmosphere is our natural and agricultural wetlands. I have been involved with determining fluxes of methane from many types of environments. Currently, I’m interested in the flux of methane from lagoons of wastewater treatment plants.


 

Collecting samples in the field

Collecting samples in the field at the salterns of Guerrero Negro, Baja, California Sur, Mexico

Sampling methane bubbles

Sampling methane bubbles at a wastewater treatment plant in California

Gypsum crust showing an endolithic microbial ecosystem

Gypsum crust showing an endolithic microbial ecosystem