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Students Research Ancient Climate Through Stream Restoration

In deep long trenches that a backhoe shoveled near Franklin & Marshall’s campus, students spent the past six months collecting samples from black wetland soil that has not seen the light of day for more than 300 years.

In the process, they extracted ancient seeds of wetland plants and other organic matter that date back to the waning stages of the last Ice Age more than 13,000 years ago.

“It’s been one of the best experiences I’ve had the pleasure of being a part of,” rising junior geoscience major Douglas Rosa says. “I’ve been loving every minute of it and I’ve found all of the research content fascinating and really interesting.”

The summer research Rosa and three other students – rising sophomore Maria Fernanda Araoz Pozo, and rising juniors Jacob Hockwitt and Julia Martin – have conducted is related to a stream restoration approach Professors Dorothy Merritts and Robert Walter, along with environmental engineering firm LandStudies, Inc., pioneered two decades ago. 

A restoration project recently launched by the Steinman Foundation and the Little Conestoga Creek Foundation is following the Merritts-Walter approach to return 2 1/2 miles of the stream back to its pre-industrialization environment. 

"In addition to improving water quality, enhancing stream capacity, rejuvenating ecosystems along the creek, and connecting disparate parts of the community via an ADA-compliant trail, this project will ultimately become an environmental science laboratory for students of all ages," says Robert Krasne, co-chairman of the Steinman Foundation.  

However, the students, who radiocarbon date the seeds and black soil at Penn State’s Accelerator Mass Spectrometry lab in State College, uncovered the area’s prehistoric past – from tundra and permafrost to warm wetland conditions  – based on their findings. 

“This experience has been very transformative, both academically and personally,” Pozo says. 

“We taught them how to extract seeds and how to identify them,” Walter says. “We’re getting constant verification and checking with our expert partners.” 

Two trenches dug for the stream restoration project have loose gravel at their bottoms, reflecting tundra with permafrost from about 80,000 to 13,000 years ago, before the landscape became a warm area with wetlands, says Merritts, a recently elected member of the National Academy of Sciences.  

“This area was unglaciated and lies about 100 kilometers south of the Laurentide ice sheet margin,” she says. “We have confirmed that continuous permafrost existed here until about 13,000 years BP (before preset time).” 

The trench walls show several feet of brown soil, which is mud from the mill ponds that once dammed the Little Conestoga Creek for more than 300 years, and beneath that, the dark black organic-rich soil of wetlands that existed before mill ponds flooded them.

“The trench site has a complete late Pleistocene to Holocene record of slow sedimentation in a sedge-dominated wet meadow with pools of slow-moving shallow water,” Merritts says. “We have about 10 radiocarbon dates at the site so far with the oldest about 13,000 years BP.”

Rosa, from Weehawken, N.J., says Merritts’ work in geomorphology is a specialization within the geoscience major that he wants to pursue.

“I’m hoping to go to graduate school after graduating, and this research will help me to get the experience of taking part in research,” he says. 

Pozo, from Tarija, Bolivia, says her coursework in the Department of Earth & Environment, and this research project, confirmed her decision to study geoscience, which she made in high school. 

“The opportunity to work with Professor Walter and Professor Merritts is very inspiring and likewise, the chance to learn from such a hard-working research team with Jacob, Julia and Douglas is making this experience one of the highlights of my F&M journey,” she says. 

Support for the trenching, radiocarbon dating, student stipends and the F&M Chesapeake Watershed Initiative is provided by the R. K. Mellon Foundation and F&M College.

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