Saturday, March 6, 2021

Jug Bay Wetlands Sanctuary: Biogeochemistry Test Bed and Field Site

Chris with snapping turtle at Jug Bay


“Snapping Turtle Working Group. How may I direct your call?”


In the days when junk phone calls used to interrupt dinnertime, at home we answered our phone with this phrase when we knew it was likely to be a marketing call. Why? My husband Chris Swarth, the Director of the Jug Bay Wetlands Sanctuary  ( from 1989-2012, was on a committee (the Snapping Turtle Working Group) to protect this vulnerable species, a much-misunderstood turtle that lived in Jug Bay’s extensive marshes.


Jug Bay in October

During the 23 years he worked there, I used Jug Bay for my own biogeochemistry studies, trained interns on how to do field work there, took postdocs into the marshes to test field equipment destined for remote areas, and analyzed many hundreds of samples for stable isotopes.


Evan and Nick Smith Herman fishing

Driving the Gator

Adjacent to the Sanctuary’s visitor center was a log house that served as the Director’s residence. For about nine years, we spent nearly every weekend there enjoying relative peace and quiet (when it was closed) and teaching our kids, Dana and Evan about the natural world. They learned to capture snakes, seine for fish, paddle a kayak, and be comfortable in thick, gooey mud. We celebrated Christmas, Easter, and birthdays in the little house, entertaining people from around the world.


Celebrating Christmas in log cabin, 1994

The wetlands and surrounding forests were lush, verdant places in spring and summer. Marsh plants thrived in the Patuxent River’s nutrient rich waters. Turtles, deer, snakes, fish, beaver, and birds found ways to utilize every habitat on the 1,800 acres of the Sanctuary. Even more important for a stable isotope biogeochemist was a diverse, rich community of microorganisms driving the nitrogen cycle, the carbon cycle, and the oxygen cycle.


Working with intern Sue Ziegler (Sue's blog), Dave Velinsky, and Chris, I began my first project studying the microbial cycles converting ammonium and nitrate back and forth as a function of the amount of oxygen in Jug Bay’s thick marsh sediments. Years later, Sue did part of her postdoc there measuring organic matter in sediments and estuarine waters. Plankton and microbes carried out a yearly dance cycling proteins and amino acids as a function of the tides and the seasons.

Aerial photo Jug Bay marshes and forests


My favorite work on rotting plants (Favorite papers) was started at Jug Bay in 1990 and published in 1999. I used the dynamic nature of the marsh plants’ seasonal growth to conduct an isotope study on how microbes alter isotope patterns during sediment burial and decay. Having a field site literally in my “front yard” made this work doable.


When astrobiology came into play at the Geophysical Lab, Jug Bay became a “Mars Test Bed” for many of the postdocs and staff member Andrew Steele. We conducted field PCR (genetic analysis) tests powered by a portable generator out on a wooden observation blind 80 meters into the freshwater tidal marsh. From lessons we learned that day, adaptations were made to equipment we then used in far-northern Arctic Svalbard (Mars on Earth). Postdocs Albert Colman and Shuhei Ono tested nutrient equipment that was later adapted to field work in Siberian Russia. Jennifer Eigenbrode and Penny Morrill tested methane collecting equipment and methods before heading to a field site in Northern California.


Shuhei Ono, Albert Colman, Simon Clarke

Jen Eigenbrode, Penny Morrill, and me

I also trained my high school interns prior to their traveling to California’s San Jacinto Mountains for fieldwork (Family Isotopes). Evan learned to drive the Sanctuary’s field vehicle, The Gator, there when he was in middle school. Every summer during the time the Geophysical Lab hosted REU interns, I brought them from the lab in Washington, DC, down to Jug Bay’s humid marshes. The lab-based interns joined Chris’s summer interns for a day of fish seining, marsh mucking, followed by a hotdog and hamburger barbecue.

Shuhei and Jen

Microbial Mud

Nick and Brendan O'Connor, intern training


Over the years, I worked with many of Chris’s interns who were studying turtles. We have measured stable isotopes of box turtles, red-bellied turtles, musk turtles, and mud turtles. Geophysical Lab intern Celine Silver with one of Chris’s interns Antonio Cordero carried out one study with box turtles. They tracked box turtles that had been removed from a major highway construction site and relocated several miles away. We compared the data from these relocated turtles with Jug Bay’s population of about 570 resident box turtles, all of which had been captured, marked, and then released. Our isotope studies on turtles revealed their dependence on the development of an ecosystem maintained by beavers that had created a sizeable pond in a small creek’s watershed.


Marked box turtle

 Looking back, my family and I were enormously privileged to have such a beautiful habitat literally at our beck and call.


We never did analyze a single snapping turtle, however, being in awe of the power of their tremendous jaws.

Marilyn and Dana, on the river

Canoeing with student Patrick Griffin

Red-bellied turtle nesting

Chris on the deck overlooking Jug Bay

Isotope Queen books are now available:


Fogel, M. L., and N. Tuross, 1999. Transformation of plant biochemicals to geological macromolecules during early diagenesis. Oecologia 120:  336-346. This paper reflects the talk presented at the 1st Isotope Ecology Meeting Keynote Address.


Ziegler, S. E. and M. L. Fogel, 2002. Seasonal and diel relationships between the isotopic compositions of dissolved and particulate organic matter in freshwater ecosystems. Biogeochemistry 64: 25-52.


Teece, M., C.W. Swarth, N. Tuross and M.L. Fogel, 2004. Determination  of the essential amino acid requirements of the red-bellied turtle,  Pseudemys rubriventris, during hatchling development. In: C. W.  Swarth, W. M. Roosenburg and E. Kiviat, eds. Conservation and Ecology of Turtles of the Mid-Atlantic Region, pp. 85-92, Bibliomania Press, Salt Lake City, Utah.


Morrill, P. L., J. G. Kuenen, O. J. Johnson, S. Suzuki, A. Rietze, A. L. Sessions, M. L. Fogel, and K. H. Nealson, 2013. Geochemistry and geobiology of a present-day serpentinization site in California: The Cedars. Geochim. Cosmochim. Acta 109: 222-240.


Rounding Third Base and Heading Home

Cards from Franny and Flowers the Rumbles   My daughter Dana is marrying George Goryan on June 25 at our home in Mariposa...