Institute Profile: Stroud Water Research Center

A former director of river and reservoir ecology for the Tennessee Valley Authority and a retired president of the International Basic Economy Corporation bounced over the dusty roads of rural southeastern Pennsylvania on a mission. It was early September 1966, and Dr. Robin Vannote and Mr. W.B. Dixon Stroud had been asked by Dr. Ruth Patrick, chair of the Department of Limnology at the Academy of Natural Sciences of Philadelphia (now of Drexel University), to find a site to build a new research station. Stroud, an honorary trustee of the academy, had been encouraged by the academy's former president, George Clark V, to facilitate access to land in rural Chester County, Pennsylvania, for the academy's research. Clark's introduction of Stroud and his wife, Joan Millikin Stroud, to Patrick started a lifelong friendship based on shared values for science and the arts. Stroud and Vannote rolled to a stop next to the ruins of an old stone Quaker bank barn overlooking the East Branch of White Clay Creek. They decided this would be the place to build Stroud Water Research Center, and Vannote would oversee design, construction, and operations. The barn, renovated into the Stroud Center's first laboratory by December 1967, would soon host some of the most influential minds in the burgeoning field of ecology and limnology. The time and place of the Stroud Center's construction mark notable inflection points in science and society (Bott and Sweeney 2014; Hearty 2019). By the time Patrick founded the Stroud Center, she had worked her way from being a volunteer curator (with a Ph.D. in botany) in the Leidy Microscope Collection at the Academy in 1937, to being one of its intellectual and administrative leaders. Her early work using diatoms as indicators of “stream health” (a term she coined circa 1950) had led to a novel approach for assessing the pollution status of waterways. She presented these results to the Limnology Society of America in 1946 and caught the attention of a well-connected industry scientist who recognized the value of Patrick's methods for understanding water pollution. She was soon overwhelmed by the demand from corporations to contract her assessment services of stream health, information that corporations needed to manage new regulatory responsibilities for their waste discharges. Patrick used these lucrative contracts to broaden her data collection and invest in independent research projects, and the Stroud Center allowed free reign for her science to flourish. Today's research at the Stroud Center remains consistent with the multidisciplinary approach that Patrick established in 1967. While the Stroud Center separated from the Academy of Natural Sciences in October 1999 to become an independent nonprofit organization, it maintains a dual mandate of seeking discoveries in freshwater science while innovating the tools and processes for aquatic science, education, and restoration (stroudcenter.org). The Stroud Center's 22-ha campus is adjacent to the East Branch of White Clay Creek in Avondale, Pennsylvania, located 54 km west–southwest of Philadelphia (Figure 1). The National Science Foundation designated the 800-ha White Clay Creek watershed upstream of the Stroud Center as an Experimental Ecological Reserve in 1981 and a Long-Term Research in Environmental Biology site in 1998. Conservation easements protect much of this land in perpetuity. The Stroud Center's frontage on White Clay Creek provides easy access to heavily instrumented stream reaches. The Stroud Center includes 3800 m2 of research, education, and administrative space, including the Moorhead Environmental Complex, a LEED Platinum building for education and public outreach that was constructed in 2012. A renovated 18th-century log cabin provides temporary housing for visiting faculty and interns. The Biogeochemistry and Ecosystem Ecology laboratories maintain gas chromatographs, spectrophotometers, and fluorometers. The Microbiology Laboratory maintains IDEXX systems, microcentrifuges, a qPCR thermal-cycler, a UV transluminator, epifluorescence microscopes, and gel electrophoresis equipment. The Fluvial Geomorphology, Entomology, and Fisheries laboratories maintain field sampling and measurement equipment, including hydroacoustic profilers, surveying equipment, electrofishing units, and small boats. Common lab equipment includes ultra-pure water, filtration capabilities, ultra-low freezers, microbalances, drying ovens, autoclave, incubators, particle-size analyzers, and sensors for in-situ measurements. A unique aspect of the Stroud Center's laboratory is the use of water from White Clay Creek within the Streamhouse and Wet Lab in flumes and biofilm experiments. A core practice of the Entomology Laboratory is to breed and maintain genetically traceable lines of macroinvertebrates for laboratory experiments, including cultures of a parthenogenetic mayfly. These organisms are fed with cultured biofilms grown in the Streamhouse with water from White Clay Creek. The creek's water can also be used in eight variable flow, variable recirculation 6-m flumes in the Streamhouse. This indoor flume facility with natural light can host replicated experimental designs for nutrient cycling and macroinvertebrate research. Since 1988, the Stroud Center has also operated the Maritza Biological Laboratory in the Guanacaste Conservation Area of Costa Rica (Figure 2). Stream ecosystem ecology research at Maritza provides an important tropical contrast to temperate streams. Maritza is staffed by two full-time technicians, and it periodically hosts visiting staff from the Avondale campus and other collaborators. The most well-cited paper from the Stroud Center is “The River Continuum Concept” (RCC) by Vannote and numerous colleagues on the River Continuum Project (Vannote et al. 1980). ASLO awarded the authors of the RCC the John Martin Award for this publication and the many studies inspired by it. In the wake of the RCC, a graduate student from Vannote's lab, Dr. Bern Sweeney, would lead a similarly sized research effort across North America to study the developmental effects of temperature on macroinvertebrates. Sweeney and Vannote's resulting Thermal Equilibrium Concept (Sweeney and Vannote 1978) was to aquatic entomology what the RCC was to river ecosystems: a foundation for developing generalized and testable hypotheses. ASLO awarded Sweeney the Ruth Patrick Award in 2024. Nutrient spiraling theory and measurement would later be shepherded to widespread application with contributions from Dr. Denis Newbold at the Stroud Center. Of the two dozen-plus Limnology and Oceanography publications by Stroud Center scientists, many involve long-term records of entomology, chemistry, hydrology, and watershed characteristics of White Clay Creek and the tropical streams surrounding Maritza Biological Station. These long-term records provide context for process-oriented research and detection of climate-related change, but they also help reveal the ecological coupling between riparian forests and streams. To study how reforestation of the riparian zone influences stream ecosystems, staff planted trees along a channel reach formerly used for cattle pasture while an adjoining reach was maintained as meadow without tree cover. These experimental units contrast with an approximately 70 year-old riparian forest upstream. This tripartite stream reach has been the center of 20 years of NSF Long-Term Research in Environmental Biology and continues today. The Stroud Center's research team has worked across the United States and around the world, but its largest off-campus research project was a 6 year survey of the freshwater ecosystems across the 5,180-km2 watershed that provides drinking water to New York City. The recently completed Delaware River Watershed Initiative involved a similar spatial scale of stream surveys over 10 years and included dozens of ecological restoration practitioners and community science collaborators. Recent tropical research in Belize and Panama complements the ongoing research at Maritza Biological Station and earlier work in Peru. Starting in 1992 with demonstrations to local schools of how to collect and identify stream macroinvertebrates, the Stroud Center's Education Department has developed a diverse portfolio of environmental education research projects and STEM curricula. The department serves over 10,000 students per year with in-person student programming and serves environmental educators from around the United States with professional development programs. A major initiative of the Stroud Center is WikiWatershed (wikiwatershed.org), a science gateway for advancing knowledge and stewardship of fresh water. WikiWatershed serves over 20,000 students, scientists, educators, and practitioners with open source modeling tools, data portals, web apps, and open hardware for a wide array of freshwater science and conservation applications. Decades of experimental research exploring the interactions and dependencies between aquatic ecosystems and their riparian forests inspired the Stroud Center to dedicate full-time staff and funding to watershed restoration. In 2012, the Stroud Center established the Robin L. Vannote Watershed Restoration Program to promote conservation practice adoption. This program and its contractors have planted 400 ha of riparian forests and facilitated the implementation of 17,000 ha of soil health practices. Beyond conservation implementation, close collaboration between the watershed restoration team, their clients, and Stroud Center scientists has enabled novel field and watershed-scale experiments to evaluate how conservation practices and riparian planting techniques affect nutrient and pesticide dynamics and water fluxes relevant to aquatic ecosystems. The Stroud Center offers undergraduate summer internships through funding from the National Science Foundation and other sponsors; opportunities are posted on the Stroud Center's website (https://stroudcenter.org/category/jobs/) in the early spring. The Stroud Center welcomes interdisciplinary collaboration with scientists, educators, and environmental practitioners around the world; get connected via Facebook (www.facebook.com/StroudCenter) and LinkedIn (www.linkedin.com/company/stroudcenter).