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David K. Skelly
Yale University
School of Forestry & Environmental Studies
370 Prospect Street
New Haven, CT 06511 USA

Yale FES



Meredith Atwood Holgerson

Office: Greeley Laboratory
Address: 370 Prospect Street, New Haven, CT 06511

B.S. Biology, Envir. Studies
Denison University
M.S. Conservation Biology
SUNY College of Env. Science & Forestry
Ph.D. Forestry & Envir. Studies
Yale University

I am broadly interested in freshwater ecology and conservation.  To date, much of my research has focused on small, temporary ponds.  Small ponds are abundant on the landscape, but we know little about their ecosystem dynamics.  I have several ongoing projects for my dissertation:

Carbon Cycling in Small Ponds
Inland freshwaters tend to be net sources of carbon to the atmosphere, meaning the system breaks down more carbon than it produces.  Small ponds make up a smaller surface area than larger lakes, but are numerically more abundant and may represent “hot spots” for carbon cycling.  My research is the first to evaluate carbon dioxide and methane production in very small ponds (<1,000 m2), and suggests that small ponds may play a disproportionately large role in greenhouse gas production.

Oxygen Dynamics in Small Ponds
Small ponds are very low oxygen environments, yet are productive and support a wide array of invertebrate and amphibian consumers.  My research suggests that while daytime oxygen concentrations are low, small ponds can receive substantial nighttime influxes of oxygen from the atmosphere.  I am working to determine the drivers of this gas exchange, and how these bursts of oxygen may help support pond fauna.

Biogeochemistry + Food Web Structure
The projects above highlight that small ponds have a very unique biogeochemistry: they are heavily loaded with CO2 and CH4, with low O2. I am curious as to how this biogeochemistry influences carbon sources in the food web.  I use stable isotope analysis to determine food web structure and ultimate carbon sources.  My research to date suggests that pond biogeochemistry (O2, CO2, and CH4 dynamics) influences the dominant carbon source in the food web.  I am currently evaluating the hypothesis that methane provides an additional carbon source to the food web when concentrations are high.

Terrestrial Leaf Litter + Aquatic Food Webs
Aquatic consumers derive carbon from two sources: terrestrial production and aquatic production.  There is current debate among aquatic ecologists regarding the extent to which terrestrial carbon can support the food web.  If terrestrial carbon can support any aquatic food web, one might expect to see it in small ponds where leaf litter inputs are high, water volume is low, and there are no inlets/outlets.  I am using stable isotopes and a tracer addition to evaluate the role of terrestrial leaf litter in the food web.

Funding Support
I am grateful to the many organizations that have helped support my dissertation work.  Without them, this work would not be possible:

  • National Science Foundation, Graduate Research Fellowship Program
  • Yale Institute of Biospheric Studies: Research Support, Small Grant Award, Dissertation Improvement Grant, Matching Grant for Stable Isotopic Studies
  • Society of Freshwater Science General Endowment Fund
  • Sigma Xi Grant-in-Aid of Research
  • Friends of Chatham Waterways Lewis E. Kimball Scholarship
  • Village Garden Club of Dennis

Master’s Research: At SUNY-ESF, I researched how different basal resources influenced amphibian consumers in small ponds.  I compared how different types of sediment and plant litter influenced algal growth and the development of wood frog tadpoles (Rana sylvatica).   I found that mineral sediments reduced tadpole survival and that although plant litter types differed in nutrient composition, the differences did not influence tadpoles.  My findings highlight that wetland restoration efforts should use organic sediment additions, and leaf litter type may not matter for tadpole development.

Undergraduate Honors Thesis: While at Denison University (Granville, OH), I worked with Dr. Rebecca Homan researching amphibian demography and distribution at a vernal pool.  We found that adult and juvenile wood frogs, spotted salamanders (Ambystoma maculatum), and American toads (Bufo americanus) migrated in non-random directions to and from the focal vernal pool.  It was through this research that I became interested in amphibian ecology and conservation.

A non-biology project with USGS: As an undergraduate, I worked with Dr. Abram Kaplan’s consulting team to evaluate the USGS Leadership Program.  The USGS strives to form a leadership-centered culture where they train employees to demonstrate leadership behavior, in hope that leadership will then diffuse through the organization.  We conducted surveys of leadership course participants, co-workers of participants, and employees at-large in the USGS to evaluate how well leadership spread within the organization.


  • ENSR Environmental Consulting (2007): I interned in ENSR’s Division of Water and Natural Resources where I was introduced to wetland policies, wetland science, and threatened species conservation. 
  • Bald Head Island Conservancy Sea Turtle Intern (2009): I performed nightly beach patrols for nesting sea turtles, PIT and flipper tagged nesting turtles, led educational programs, and also conducted amphibian call surveys for an independent research project.

Getting local middle school girls excited about science and freshwater ecology!



Atwood, M.A. 2013. Effects of euthanasia method on stable-carbon and stable-nitrogen isotope analysis for an ectothermic vertebrate. Rapid Communications in Mass Spectrometry 27 (8): 909-913.  Link

Atwood, M.A., J.W. Mora, and A.W. Kaplan. 2010. Learning to lead: evaluating leadership and organizational learning. Leadership and Organizational Development Journal 31 (7): 576-595.

Homan, R.N., M.A. Atwood, A.J. Dunkle, and S.B. Karr. 2010. Movement orientation by adult and juvenile wood frogs (Rana sylvatica) and American toads (Bufo americanus) over multiple years. Herpetological Conservation and Biology 5 (1): 64-72.

Mora, J.W., A.W. Kaplan, L.M. Weis, and M.A. Atwood. 2008. Recipe for change: building a leadership culture at the U.S. Geological Survey.  Training and Development 62 (3): 42-46.

Spotted salamander egg masses at a study pond.

Posing by one of my study ponds.

Cladoceran zooplankton from a study pond.

A nice day to sample ponds.