Following the people and events that make up the research community at Duke

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Tag: Nicholas School of the Environment

Reducing Food Insecurity and Creating Community at Durham’s Catawba Trail Farm

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At Catawba Trail Farm in north Durham, the idea of community remains at the forefront of all that they do. A space dedicated to growing, learning, and diligent work, the farm invites all willing to become involved. Recently, students at Duke University had the opportunity to bear witness to these qualities, through a course taught by Dr. Brian McAdoo of Duke’s Nicholas School of the Environment.

Picture of volunteers at Catawba Trail Farm (Credit: @UrbanCommunityAgrinomics on Instagram.)

The Catawba Trail Farm was once known as Snowhill Plantation, yet despite this co-founder Delphine Sellars refers to it as “a place of healing.” This is because Sellars recognizes the importance of acknowledging the past when attempting to shape the future. Sellars’ focus is on taking land formerly used to abuse enslaved people and transforming it into a place of empowerment and healing. This is seen through the connection between the farm and McAdoo’s course here at Duke. The course, “Exploring Earth Sciences: Surviving Anthropocene in North Carolina,” explores a range of themes such as food insecurity, environmental justice, and global change through the context of environmental studies. Additionally, McAdoo’s course has what is referred to as the ‘Catawba Trail Mission’ where Duke students, in partnership with Catawba Trail Farm, seek to not only target this food insecurity within the community, but also uncover the history hidden within the roots of the farm.  

Picture of Delphine Sellars (Credit: @UrbanCommunityAgrinomics on Instagram.)

The most recent progress of this mission can be seen through the class’s work with the gravesite of William Johnston, who established Snowhill Plantation in 1763. Through a geophysical survey, the class identified several unmarked graves of enslaved people buried with the Johnston family. Through this they have worked to trace their lineages to their loved ones and inform them of their findings. The class has also used this same technology to help identify and ensure that the traits and key aspects of the land are fully understood and respected. 

Picture of volunteers at Catawba Trail Farm (Credit: @UrbanCommunityAgrinomics on Instagram.)

Through the work between Duke and Catawba Trail Farm, students are granted the opportunity to take their learning beyond the textbook and truly begin to understand the depth behind the land outside of technological gadgets. Catawba Trail Farm helps in this journey while simultaneously learning more about the rich nature of the land and its inhabitants. This constant sense of learning and support is what makes students such as Duke master’s student, Roo Jackson, comfortable in saying Catawba Trail Farm “feels like home.” 

Post by Gabrielle Douglas, Class of 2027
Post by Gabrielle Douglas, Class of 2027

Glowing Waterdogs and Farting Rivers: A Duke Forest Research Tour

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Jonny Behrens looks for aquatic macroinvertebrates with Duke Forest Research Tour participants.

“Who would be surprised if I told you that rivers fart?”

Nick Marzolf, Ph.D., went on to explain that streams release greenhouse gases from decaying matter and gas-producing bacteria. This revelation was one of several new facts I learned at the annual Duke Forest Research Tour in December.

“First and foremost,” says Duke Forest Senior Program Coordinator Maggie Heraty, “the Duke Forest is a teaching and research laboratory.” The Office of the Duke Forest hosts an annual Research Tour to showcase research activities and connect to the wider community. “Connecting people to science and nature, and demystifying scientific research, is a key part of our goals here,” Heraty says.

Duke Forest, which consists of over 7,000 acres in  Durham, Orange, and Alamance Counties, lies within the Cape Fear and Neuse river basins, two of seventeen river basins in North Carolina. What exactly is a river basin? Heraty quoted a poetic definition from North Carolina Environmental Education:

“A river basin encompasses all the land surface drained by many finger-like streams and creeks flowing downhill into one another and eventually into one river, which forms its artery and backbone. As a bathtub catches all the water that falls within its sides and directs the water out its drain, a river basin sends all the water falling within its surrounding ridges into its system of creeks and streams to gurgle and splash downhill into its river and out to an estuary or the ocean.”

Located within the Cape Fear River Basin, the headwaters of New Hope Creek, which passes through the Korstian Division of Duke Forest, are fed by roughly 33,000 acres of land, over 5,000 of which are in the Duke Forest. Land outside of the Forest is of vital importance, too. Duke Forest is working in partnership with other local conservation organizations through the Triangle Connectivity Collaboration, an initiative to connect natural areas, create wildlife corridors, reduce habitat fragmentation, and protect biodiversity in the Triangle region.

New Hope Creek in the Korstian Division of the Duke Forest.

Dwarf waterdogs

We walked down a short trail by the creek, and the tour split into two groups. Our group walked farther along the stream to meet two herpetologists studying the elusive dwarf waterdog.

Bryan Stuart, Ph.D., Research Curator of Herpetology at the North Carolina Museum of Natural Sciences, and Ron Grunwald, Ph.D., Duke University Senior Lecturer Emeritus, are involved in a study looking for dwarf waterdog salamanders (Necturus punctatus) in New Hope Creek. Dwarf waterdogs are paedomorphic, Stuart said, meaning they retain larval characteristics like external gills and a flat tail throughout their lives. In fact, the genus name Necturus means “tail swimmer” in reference to the species’s flat tail.

According to Stuart, on October 3, 1954, Duke professor and herpetologist Joe Bailey collected a dwarf waterdog in New Hope Creek. It was the first record of the species in Orange County.

The Duke Forest is in the westernmost part of the species’ Piedmont range, though it extends farther west in parts of the sandhills. “To have a dwarf waterdog record in Orange County—that’s almost as interesting as it gets,” Stuart said.

Ron Grunwald and Bryan Stuart discuss dwarf waterdog research at New Hope Creek.
Photo provided by The Office of the Duke Forest.

In the late 1960s, Michael A. Fedak, Bailey’s graduate student, did a thesis on dwarf waterdogs in the area. His specimens are still stored in the collections of the North Carolina Museum of Natural Sciences.

No one had studied this population since—until now.

Dwarf waterdogs are very sensitive to pollution and habitat disturbance, Stuart said, on top of the fact that New Hope Creek is already at the edge of the species’s habitat. When Fedak studied them several decades ago, the salamanders were abundant. Are they still?

Stuart, Grunwald, and other researchers want to find out. “The challenge of salamander biology,” Grunwald said, “is that it always happens when it’s freezing.” Surveying salamander populations, he explains, isn’t like watching birds or counting trees. It requires you to go where the salamanders are, and for dwarf waterdog research, that means dark, cold streams on nights when the water temperature is below 55 degrees Fahrenheit.

Researchers bait funnel traps with chicken liver or cat food and set them underwater overnight. Sometimes they catch crayfish. Sometimes they catch nothing. And sometimes they catch exactly what they’re hoping to find: the elusive dwarf waterdog. After all this time, these slippery, nocturnal, chicken-liver-loving salamanders are still here.

Two dwarf waterdogs in a funnel trap before being released back into New Hope Creek.

Though the traps have been successful at capturing some individuals, they will never catch them all, so researchers calculate the recapture rate to estimate the total population. Imagine a bag of rice, Grunwald said. You could count each individual grain, but that would be challenging and time-consuming. Alternatively, you could pull out one grain of rice, color it, and put it back in the bag, then estimate the total number by calculating the probability of pulling out the same colored grain of rice again. In a very small bag, you might draw the same rice grain several times. But the more rice you have, the less likely you are to draw the same grain twice.

To figure out if any of the dwarf waterdogs they catch are recaptures, the researchers mark each individual with a visual implant elastomer, which is “just a fancy way of saying rubber that we can see,” Grunwald said. The material is injected under a salamander’s “armpit” with a small syringe, creating a pattern visible under ultraviolet light. With two colors (fluorescent yellow and red) and four possible injection locations (one behind each leg), there are plenty of distinct combinations. Grunwald showed us a waterdog that had already been marked. Under a UV flashlight, a spot just below its right foreleg glowed yellow.

Captured dwarf waterdogs are injected with a special rubber material that glows under a UV light. Each salamander is marked with a distinct pattern so researchers can recognize it if it’s ever recaptured.

Establishing a recapture rate is essential to predicting the total population in the area. The current recapture rate? Zero. The sample size so far is small—about a dozen individuals—and none of them have been caught twice. That’s an obstacle to statistical analysis of the population, but it’s good news for the salamanders. Every new individual is one more dwarf waterdog survivor in New Hope Creek.

Ron Grunwald with Research Tour participants looking at dwarf waterdogs in bags.
Photo provided by The Office of the Duke Forest.

Stream health

Next, at a different spot along the stream, we met Nick Marzolf, Ph.D., a postdoctoral scholar, and Jonny Behrens, a Ph.D. student, to learn more about New Hope Creek itself. Marzolf and Behrens have both been involved with aquaterrestrial biogeochemistry research in the lab of Emily Bernhardt, Ph.D., at Duke University.

Nick Marzolf (right) and Jonny Behrens discuss stream health.
Photo provided by The Office of the Duke Forest.

Protecting New Hope Creek requires understanding individual organisms—like dwarf waterdogs—but also temperature, precipitation, oxygen levels, pesticide runoff, and biodiversity overall. When humans get stressed, Behrens said, different organs have different physiological reactions. Similarly, different organisms in a stream play different roles and respond to stress in different ways.

Jonny Behrens and Research Tour participants look at aquatic macroinvertebrate samples.
Photo provided by The Office of the Duke Forest.

Behrens passed around vials containing aquatic macroinvertebrates—specimens big enough to see with the naked eye—such as the larvae of mayflies, crane flies, stoneflies, and dragonflies. They are known for being good indicators of stream health because there are many species of macroinvertebrates, and they have different tolerances to stressors like pollution or changes in water temperature.

Aquatic macroinvertebrates can indicate the health of a stream through their species diversity and abundance.
Photo provided by The Office of the Duke Forest.

The water downstream of a nearby wastewater treatment plant is much warmer in winter than other waterways in the area, so researchers see more emergent adult midges and caddisflies there than they do here. Aside from temperature, organisms need to adapt to other changing conditions like oxygen levels and storms.

“Rain is really fun to watch in streams,” Behrens said. The water level rises, pulling up organic matter, and sand bars change. You can tell how high the water got in the last storm by looking for accumulated debris on trees along river banks.

Farting rivers and the peanut butter cracker hypothesis

Marzolf studies hydrology, or “how water moves through not only the landscape but also the river itself.”

Nick Marzolf demonstrates a technique to measure gasses in streams using a syringe.

Part of his research involves measuring gases in water. Streams, like cars and cows and people, release greenhouse gases, including carbon dioxide and methane. In fact, Marzolf and colleagues hypothesize that New Hope Creek contributes more CO2 to the atmosphere per unit area than anywhere else in the Duke Forest.

Decaying matter produces CO2, but that isn’t the only source of greenhouse gasses in the creek. Microscopic organisms, like methane-producing bacteria, produce gases as well.

The “peanut butter cracker hypothesis,” Marzolf said, compares organic matter such as leaves to a cracker, while the “peanut butter,” which makes the cracker more palatable, is the microbes. Scrumptious.

Disturbing the sediment at the bottom of New Hope Creek causes bubbles to rise to the surface due to the metabolic activities of gas-producing bacteria.

Marzolf turned to Behrens. “Do you want to walk around and see if you can stir up some methane bubbles?” Behrens waded into the stream, freeing bubbles from the pressure of the overlying water keeping them in leaf mats. We watched the bubbles rise to the surface, evidence of the activities of organisms too small to see.

Behrens walks around in New Hope Creek to stir up gas bubbles from aquatic bacteria.

Restoring a stream to protect its pigtoe

Finally, Sara Childs, Executive Director of the Duke Forest, discussed stream restoration projects. Though structures in the Duke Forest like remnants of old mills and dams can alter and damage ecosystems, they can also have historical and cultural significance. Duke Forest prioritizes restoration projects that have meaningful ecological, teaching, and research benefits while honoring the history of the land.

For instance, the Patterson Mill Dam was built in the late 1700s and probably remained in use for about 100 years. The stream has already adapted to the structure’s presence, and there isn’t necessarily ongoing degradation because of it. Duke Forest restoration projects, Childs said, don’t revolve around very old structures like the Patterson Mill Dam. Instead, they are planning to remove two more recent structures that are actively eroding banks, threatening wildlife habitat, and creating impounded, oxygen-poor areas in the stream.

One of the structures they are hoping to remove is a concrete bridge that’s endangering a threatened freshwater mussel species called the Atlantic pigtoe (Fusconaia masoni). Freshwater mussels, according to Childs, require a fish species to host the developing mussel larvae on their gills, and the Atlantic pigtoe favors the creek chub (Semotilus atromaculatus). The concrete bridge forms a barrier between the pigtoe and the chub, but removing it could reunite them.

Before starting construction, they will relocate as many mussels as possible to keep them out of harm’s way.

New Hope Creek, home to waterdogs and pigtoe and farting microbes, is precious to humans as well. Heraty describes it as “a really spectacular and beautiful waterway that we are lucky to have right in our backyards here in Durham.”

Post by Sophie Cox, Class of 2025

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