Bess Ward - Research
For information about Bess Ward's research, please go to the Microbial Ecology/Environmental Microbiology page.
Research (Project Summaries)
Marine and global nitrogen cycle, molecular and immunological probes for marine bacteria and bacterial processes (especially nitrification and denitrification), microbial ecology, phytoplankton community composition and succession, phytoplankton nitrogen utilization
Microbes control many of the important biogeochemical processes that occur in the oceans as well as on land. They contribute to the trace gas cycles that influence climate; they utilize and produce nutrients that are involved in eutrophication; and they are even capable of cleansing the environment by degrading a vast variety of chemical compounds, both naturally occurring and anthropogenically produced. My research focuses on the nitrogen cycle and the microorganisms involved in transformations of inorganic and organic nitrogen in the ocean and in sediment environments. This research makes use of technical approaches that range from molecular biological techniques to stable isotope biogeochemistry. The two main bacterial groups we study are the nitrifiers (both bacteria and archaea), autotrophs, which oxidize ammonium to nitrite and nitrate, and the denitifiers, heterotrophs that can respire nitrate in the absence of oxygen. The linked activities of these two groups can be crucial in determining the chemical form and supply of nitrogen to planktonic communities and in determining the net nitrogen budget of ecosystems. Our work also addresses the utilization of nitrogen by marine phytoplankton, and investigations of community composition response to changing nitrogen availability.
We have used molecular methods for identification and analysis of bacteria in natural systems to study the distribution and diversity of nitrifying and denitrifying bacteria in marine environments. We have developed a suite of functional gene microarrays, which we use to evaluate the community composition of different functional groups, such as nitrifiers, denitrifiers, eukaryotic nitrate assimilators, etc. With these high throughput methods, we have been able to identify groups of phylotypes among the ammonia oxidizing bacteria that vary together in response to environmental factors, showing repeating patterns over multiple years. In the case of phytoplankton, the high resolution array data are matched with biogeochemical rate measurements to investigate which phytoplankton types respond to different nutrient conditions and which are responsible for most of the N assimilation at different times of year.
Denitrification has long been recognized as the primary biological sink for fixed nitrogen in natural environments. But in 1995, the process of anaerobic ammonium oxidation (anammox) was discovered and subsequently shown to be a very important N loss process in sediments and oxygen minimum zones (OMZs) of the ocean. Surprisingly, several studies have found that anammox dominates the N loss process in OMZs, and denitrification is sometimes not detected at all. In our work on denitrification, we have found that denitrifying bacteria in OMZs show classical bloom dynamics, in which an initially very diverse assemblage becomes much less diverse as a few phylotypes “win” and attain high cell densities under intensely denitrifying conditions. This kind of behavior is consistent with episodic denitrification in OMZs, which we suggest can explain the apparent lack of denitrification. We are now investigating, through both manipulative experiments and modeling approaches, the environmental factors which might control the relative contributions of anammox and denitrification to N loss in the ocean.
This research program (Project Summaries) is supported by field work on research cruises and expeditions as well as by laboratory based research, and is supported by a variety of federal and regional funding agencies.
Recent Extramural Projects
2007-2010 National Science Foundation, Biological Oceanography: En-Gen: Genome-Enabled Environmental Functional Genomics and Expression Profiling of Diatoms in the Ocean. (Co-PIs François Morel, Princeton, and Andrew Allen, J. Craig Venter Institute)
2007-2010 National Science Foundation, Chemical Oceanography: Denitrification and Anammox in the Arabian Sea.2005-2008 National Science Foundation, Biological Oceanography: Eukaryotic phytoplankton functional diversity: Dynamics of phytoplankton response to N supply during upwelling. (Co-PI B. K. Song, University of North Carolina, Wilmington).
2004-2005 DOE, Draft Level Sequencing of a Selection of Nitrifying Bacteria (with Dan Arp, Martin Klotz, Lisa Stein, Jenny Norton)
2004-2006 National Science Foundation, Chemical Oceanography: Diversity and distribution of denitrifying bacteria in relation to chemical distributions in the oxygen minimum zone of the Arabian Sea. (Co-PI, Amal Jayakumar).
2004-2006 National Science Foundation: Microbial genome sequencing; The complete genome sequence of a mini consortium of marine ammonia oxidizers. (Martin Klotz, Karen Casciotti, John Heidelburg, Co-PIs)
2003-2006 National Science Foundation: What limits denitrification and bacterial growth in Lake Bonney, Taylor Valley, Antarctica?
2000-2005 National Science Foundation: Biocomplexity of Aquatic Microbial Systems: Relating Diversity of Microorganisms to Ecosystem Function.2000-2003 Department of Energy: The Coupling Between Carbon and Nitrogen Cycles in Coastal Upwelling Ecosystems: Biogeochemical Cyling and Its Molecular Basis.
1998-2001 National Science Foundation: Control of Dentrification in a Permanently Ice Covered Antarctic Lake: Potential for Regulation by Bioactive Metals. (Co-PI Mark Wells, UCSC.)
Research Cruises and Expeditions (recent)
2007 Chief Scientist, R/V Roger Revelle, Arabian Sea, 30 days, Sep – Oct.
2005 McMurdo Station and Lake Bonney, Antarctica, 6 weeks, Nov-Dec
R/V Knorr, Eastern Tropical North Pacific, 21 days, Oct-Nov
2004 McMurdo Station and Lake Bonney, Antarctica, 7 weeks, Nov-Dec
R/V Cape Henlopen, Sargasso Sea, 4 days, Oct, Chesapeake Bay, 3 days Oct.
2003 R/V Cape Henlopen, Sargasso Sea, Chesapeake Bay, 3 days Apr, June, Oct.
2002 R/V Cape Henlopen, Sargasso Sea, 4 days, Apr, Chesapeake Bay, 3 days Oct.
2001 R/V Cape Henlopen, Chesapeake Bay, 3 days, Aug, 3 days Oct.
2000 McMurdo Station and Lake Bonney, Antarctica, 6 weeks, Nov-Dec.
1999 Chief scientist, R/V Point Sur, Monterey Bay, 5 bimonthly 1-day cruises.
McMurdo Station and Lake Bonney, Antarctica, 7 weeks, Nov-Dec
1998 Chief scientist, R/V Point Sur, Monterey Bay, 6 bimonthly 1-day cruises.
1996 R/V Sagar Sampada, Arabian Sea, 13 days, November.