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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. Current and recent projects include: the examination of hypersaline microbial mats, determination of natural estrogen in karst spring basins, and the air-sea fluxes of methane.

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 and consumption within the mats, 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.

Estrogen in karst spring basins

Along with Dr. Carol Wicks and her students, I was involved with investigating the sources and fate of natural estrogens in ground water in the karstic basins of Missouri. Based on this work, we concluded that cavefish are exposed to concentrations of estrogen, at least on the short term, that might be adversely impacting their health. We have also found that natural estrogen does not appear to degrade over short time periods (14 days, the travel time through the karstic basins of interest).

Air-sea fluxes of methane

Methane is a globally significant greenhouse gas that is produced by obligately anaerobic bacteria. The largest source of methane to the atmosphere is our natural and agricultural wetlands. Paradoxically, the surface ocean, an oxygen-rich environment, is also supersaturated with respect to methane. With colleagues from the University of West Florida, I had the opportunity to sail on a transect cruise from the southern tip of Chile up to the U.S. By measuring depth profiles of dissolved methane, I was able to determine that methane concentrations were greatest at the thermocline, suggesting that methane was being produced in organic-rich particles collecting at this density interface. In addition, by measuring atmospheric methane concentrations, air-sea fluxes of methane from 41 oS to 27 oN latitude were also determined.

 

collecting microbial mat

Cutting out and collecting a square of microbial mat from the Guerrero Negro salt ponds to be transported back to the greenhouse facility at NASA Ames Research Center. These mats have been studied and continue to be studied because of their evolutionary link to early life on this planet, and because they can be used as an analogue to life on other planets, such as Mars, where we are now finding evidence for paleo-hypersaline environments.

Greenhouse One

Greenhouse One, located at NASA Ames Research Center. Inside microbial mats have been maintained for over a year. For a live look inside the greenhouse, go to: http://greencam.arc.nasa.gov

microelectrode

Oxygen microelectrode measuring an oxygen profile in one of the microbial mats located in Greenhouse One. The microelectrode can be automatically lowered into the mat at a spatial resolution of about 50 micrometers.

All photos on this page taken by Dr. Brad Bebout of NASA Ames Research Center.