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Water World: Calder Director Measures Aquatic Health in Upper Mississippi


John Wehr, Ph.D., directs Fordham’s Calder Center in Armonk, N.Y.
Photo by Bill Denison

John Wehr, Ph.D., sees the world’s network of watery veins and arteries for what it is: the vascular system of the Earth.

As a limnologist, Wehr, professor of biology and director of Fordham’s Louis Calder Center biological field station, has conducted numerous studies on the impact of humans on freshwater environments, most notably on water quality and critical levels of phytoplankton.

At Calder, Wehr oversees research projects in the center’s 10-acre lake and in lakes and streams across the state. He also mentors projects in the University’s Experimental Lakes Facility (ELF) tanks, a collection of two dozen 1,200-gallon tanks that can hold entire lake communities for research purposes.

The ELF tanks make it possible to replicate a “miniature lake” that can be controlled, yet result in environmental conditions with a fairly high level of realism. Recently, Wehr oversaw a project on how an increase in ultraviolet radiation levels, resulting from the thinning ozone layer, affected the lake’s algal and bacterial communities and, therefore, its food chain.

“In the past, we thought of fish and larger plankton as being most important, but it is actually these tiny microbes that are critical,” he said.

As the co-editor of Freshwater Algae of North America: Ecology and Classification (Academic Press, 2003), Wehr’s expertise in algae and phytoplankton has attracted projects beyond the confines of Calder. A few years ago, Wehr published a study on the health of channel regions of the Ohio River. Currently, he is partnering with the U.S. Geological Survey (USGS) to study a huge archive of phytoplankton samples from the upper Mississippi River, and helping to measure the importance of wetlands on the river’s ecosystem.

“The upper section of the Mississippi is basically still a natural river, expanding and contracting with rainfall and the time of year,” said Wehr, who divides his time between the Calder Center and the Rose Hill campus. “But the lower part of the Mississippi has been turned into essentially a channel of water, with few wetlands to buffer the water and no exchange.”

The result, he said, is catastrophic flooding and a “dead zone” that exists in the Gulf of Mexico at the river’s mouth, stretching for 5,000 square miles. There, an abundance of algae, feeding upon an excess of nitrate-based nutrient runoff, makes aquatic life unsustainable.

“Some scientists refer to wetlands and side channels of rivers as ‘the rivers’ liver,’” Wehr continued. “Our research asks the questions: does a river that has high connectivity and intact flood plains function better? Is it necessary to preserve intake wetlands and backwater habitats that previously were thought of as useless? We suspect wetlands matter because of how their phytoplankton and other microbes process nutrients.”

A few times a year, Wehr and his students travel to LaCrosse, Wis., to measure the activity and composition of aquatic organisms and water samples, using experimental enclosures that are dropped in different locations of the upper Mississippi.

Wehr and Jillian Decker, a doctoral candidate in biology, transfer the river samples into clear, one-gallon sunlit containers called mesocosms. Back at the center’s labs, they test hundreds of samples from a range of habitats on the river.

In addition to the experimental samples, Wehr and Decker are doing tests on the first round of a cross-section of 10,000 preserved, unstudied samples of river phytoplankton collected by the USGS over the past decade.

“There are very few agencies in the world that have such a huge archive just waiting for someone to analyze,” Wehr said.

Wehr and colleagues in LaCrosse are working on a paper, “Differences in Phytoplankton Species Composition Among Habitat Types in Pool 8 of the Upper Mississippi River,” based on their preliminary research. The long-range plan, Wehr said, is to get additional federal funding to complete a more comprehensive study on the upper river’s connectivity—and how it influences an ecosystem.

At Fordham, Wehr wears three distinct hats: as professor of biology, he teaches students on the Rose Hill campus; as Calder’s director, Wehr oversees the budget and staff of the forested, 113-acre facility; lastly, he is a vigorous mentor.

“There were three faculty and two grad students when I arrived [in 1986],” recalled Wehr, “Now we’re eight faculty and countless students.”

Each summer, the center hosts Fordham University’s Calder Summer Undergraduate Research (CSUR) Program, sponsoring 12 undergraduates from around the country in paid research internships. The program has been in existence since 1998 and is funded by the National Science Foundation (NSF). This past summer, six of the 12 students were from Fordham.

During the academic year, the center engages several undergraduates and about a dozen graduate research assistants on projects that often lead to honors, master’s or doctoral theses. Plans are underway to provide 12 housing spots for graduate students with the new construction of NSF-funded, log cabin dormitories.

“We tryto make Calder a place where students can do good science, one that is very collaborative,” said Wehr, who takes photos of his students after they defend their master’s theses or doctoral dissertations and posts them on the wall of his office.

“As with all of the scientists here, our labs don’t work unless we’ve got students happily joining us in our research. In fact, I can’t imagine doing a research project without having students involved.

“I think we have had a good impact on a number of people’s careers and lives,” he said.

– Janet Sassi


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