TITLE: Postdoctoral Research Associate
ACADEMIC INSTITUTION: University of Southern California

 

What is your role in Extreme 2008?
I’m the sole postdoc funded by our deep-sea/hydrothermal vent research project, which is focused on developing an understanding of the distribution, genetic diversity, and activities of protists (single-celled eukaryotic microorganisms).  Several years ago, I collaborated with Drs. Dave Caron and Craig Cary to write the research proposal that’s currently supporting my work on the Extreme 2008 expedition. This year, we’ll be adding to our protistan sample collections from 2007 and conducting experiments to characterize the feeding activities of protists in the deep sea. I’ll be participating in all aspects of protistan sample collection and processing and will be working with Dave and Craig to plan dives and prioritize collections.  A major task for this field season will be the retrieval and processing of "protist traps" that have been deployed for the past year at both Guaymas Basin and 9North. Additionally, I’ll be attempting to amplify the DNA in single-cell isolates to identify their phylogenetic affiliation and determine the extent to which these visibly active cells are included in environmental DNA samples from vent systems.

What questions are you trying to answer and why?
Recent work in our lab at USC has focused on describing protistan diversity at several deep-sea sites in the Sargasso Sea (2,500 m) and a research site off the coast of Southern California (500 - 900 m).  Previous studies of protistan diversity using light microscopy have provided a limited description of the "true" taxonomic diversity of complex assemblages. Analysis of sub-cellular morphology by electron microscopy has been useful for describing individual protistan taxa, but is extremely labor intensive. For these reasons, we’ve turned to characterizing complex protistan assemblages using DNA-based technologies. We’ve detected a number of DNA-based phylotypes from our deep-sea samples which have a high degree of similarity to newly discovered protistan lineages.  These new lineages have been described recently by research groups from various sites around the world with many examples coming from a relatively small number of deep-sea samples. The size, shape, abundance, and trophic status of these newly described taxa are largely unknown, and evidence of their existence is limited almost exclusively to DNA databases. We’re broadly interested in describing protistan diversity in the deep sea and specifically at hydrothermal vents for the purpose of revealing the microbial community structure at these sites, characterizing previously unknown taxa and, when possible, linking cellular morphotypes to their genetic and physiological signatures.

Why is this research important? What are the benefits?
Describing the diversity of complex protistan assemblages is important for uncovering the range of eukaryotic diversity and determining the function of various ecosystems in the world’s oceans.  In general, more diverse systems tend to be more stable with respect to particular ecosystem-level functions. Protistan diversity is turning out to be much higher than pre-molecular studies would have predicted, which has implications for ecosystem modeling.  In addition, DNA-based diversity data will help us to understand the evolutionary relationships among eukaryotes and possibly help to explain the origin of life on Earth. Despite these facts, many marine systems lack comprehensive descriptions of the protistan community (e.g., how many different types of organisms are present at a given time?).  Phototrophic protists (phytoplankton) are responsible for a majority of the primary production in the euphotic zone (the region of the water column illuminated by solar radiation) while heterotrophic protists feed on other protists and prokaryotes (bacteria and archaea) all through the water column.  Recycling of nutrients and organic matter by heterotrophic protists can provide a significant source of nitrogen and phosphorous in nutrient-limited systems.  Additionally, heterotrophic protists may serve as prey for larger organisms, thereby serving as a conduit for energy transfer from the base of marine food webs to higher trophic levels.  Discovering which organisms are present at a given time and location will provide clues for understanding how nutrients and energy cycle through marine ecosystems. This is especially true for hydrothermal vents where the functional roles of protists are virtually unknown.

What's your background, and what lured you into marine science/education?
I grew up in New Hampshire, near Lake Winnipesaukee, where I spent many summers exploring the lake. My Dad and I obtained our SCUBA certifications when I turned 16, which opened up a whole new realm of underwater exploration for me.  I pursued my undergraduate degree in zoology at the University of New Hampshire, during which time I volunteered in a marine plankton ecology laboratory.  In January 1991, I began a six-month volunteer program at the Bermuda Biological Station for Research (BBSR).  My first job in Bermuda involved studying sea anemones and their protistan symbionts (phototrophic dinoflagellates). This volunteer work led to a full-time technical position at BBSR where I worked on a project studying oceanic nutrient cycles and the utilization of nutrients by marine microbes.  I met many visiting scientists in Bermuda, and these interactions made me realize that I was very interested in studying the role of bacteria and protists in the marine environment.  I received my master’s degree in marine science from the College of William and Mary in 1999, where I studied heterotrophic bacterial production. In 2005, I received a Ph.D. in biological sciences from the University of Southern California, where I conducted research on the molecular ecology of marine protistan assemblages.