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Wetland Center study
shows highway culverts can alter wetland ecology and water flow
The first phase of a study funded by the North Carolina State University-based Center for Transportation and the Environment investigated the effect of highway construction on wetlands. Wetland Center researchers found that trees, plants, and soils in two wetland systems were significantly changed by the way underlying culverts altered water levels on either side of a stretch of Interstate 40 in eastern North Carolina. The extension of I-40 from Raleigh to Wilmington in the late 1980s meant cutting through miles of wetlands. The highway’s effects on drainage, water flow, and species habitats posed many important questions. DUWC Director Curtis J. Richardson said state and federal transportation officials now recognize a vital need for new construction standards in wetlands. "But they really don’t have the data to say how they should design when crossing wetland areas," he added. "That is what we are trying to provide." |
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Dr. Richardson and fellow investigator Dr. Kevin Nunnery, now a Wetland Center post-doctoral researcher, faced an immediate hurdle when they began their study in 1995. They had to assess construction impacts of a highway that had been built seven years before their study began.
They chose two adjacent wetland corridors, Beaverdam Swamp and Kill Swamp, which cross Interstate 40 about 1.5 miles apart near the Sampson County town of Newton Grove in North Carolina’s coastal plain. Both swampy creeks had similar water flow rates and kindred upstream and downstream environments. Their upstream land use patterns - agriculture and livestock production - were also similar. And both passed under I-40 through the same type of conduit systems - a central box-shaped culvert and two smaller stream overflow pipes. The locations were deemed the best sites available in North Carolina for studying a recently constructed highway crossing’s effects on wetlands.
In a move to mimic how the affected wetlands might have appeared before the superhighway’s construction, Richardson and Nunnery selected an undisturbed "reference area" about 320 yards upstream from the Beaverdam Swamp study site. They also obtained highway department pre-construction aerial photos of the wetland crossing sites to gauge what the tree cover was like before I-40 was completed.
Their study showed that the box culvert systems ended up acting more like bottlenecks than conduits, especially at the Beaverdam Swamp crossing. "During the wet periods water backed upstream significantly," Richardson said in a recent interview. "That significantly changed the areas that were wet, and it quite often killed upstream vegetation there. More than that, we found after a period of time that a lot of the wetlands were converted into new types of wetlands. And some uplands also were converted into wetlands."
In a final report on the 18-month field study, conducted from March 1995 until October 1996, the researchers said the culvert bottleneck raised Beaverdam Swamp’s mean surface elevation more than 7 inches upstream of the highway crossing. Resulting ponding extended more than 100 yards upstream. And the soil decomposition rate was significantly lower upstream as well, "suggesting that ponding was inhibiting decomposition there," the report said.
While Kill Swamp’s water levels were altered less dramatically, there were significant changes in vegetation within both wetlands. Plants downstream of both crossings were 30 percent to 50 percent thicker below the crossing than in upstream sections. Trees also grew 10 percent to 40 percent less prolifically upstream than downstream.
The reference area, which had escaped any impact from I-40, contained "several less flood tolerant species" than the affected areas, "suggesting that stream hydrology had been disturbed near the highway," the report said. Trees in the reference area were also significantly leafier than in the affected areas.
The report described a general "paucity of information on what effects highways may have on wetland ecological functions, and how severe and geographically far-reaching those effects are." There is also "no accepted, reliable procedure for quantifying and assessing" those impacts.
In the study’s second phase the center has begun studying how a new US 17 bypass project near the Camp Lejeune Marine Corps base near New Bern will affect coastal wetlands in the adjacent New River Estuary. This time the scientists have been able to begin their work before construction begins.
The assessment framework developed for freshwater wetlands in the study’s I-40 phase is being refined and modified for brackish wetlands. Researchers will have collected data for a full field season prior to the beginning of highway construction in wetlands affected by construction as well as in two reference wetlands.
"We plan to monitor these wetlands through the construction phase and through any recovery phase," said Dr. Neal Flanagan, a Wetland Center investigator in the second phase. "The objectives of our current research are to produce assessment criteria specific to coastal wetlands and to identify highway construction techniques and designs that minimize impacts."
From the Director
Looking back, looking forward
t
is with great pleasure and excitement that I welcome you to the first issue
of WetlandWire. During the past few years many DUWC graduates and other NSOE
alumni have written or e-mailed to ask about recent happenings at the Wetland
Center and about important national trends in wetland topics. Well, these past
few years have been busy indeed, both at the center and across the country.
Since its inception in 1990, the Wetland Center faculty has grown to include
four core faculty and 18 staff researchers based in Durham and at the center’s
Florida Everglades field station. Center research efforts have ranged from acid
mine drainage in Tennessee and Alabama, hydrologic and phosphorus issues in
the Florida Everglades, restoration of salt marshes in the Southeast, and the
effects of highway culverts on wetland ecology in North Carolina. Many of our
students have moved on to positions in federal and state governments, consulting
firms, teaching, and academic research. They are entering the field as wetland
issues garner increasing attention in political, civic, and industrial arenas.
In these active times we hope WetlandWire will be a two-way conduit between you and the Wetland Center’s faculty, staff, and students. We will bring you news and a variety of viewpoints on what is happening in the wetlands community. You’ll meet the Duke Wetland Center faculty, staff, and students. There will also be regular updates on our new and continuing research projects. We look forward to your comments on WetlandWire and your suggestions for future issues. We especially look forward to hearing from DUWC alumni so future issues can include an alumni news column.
I would like to thank a number of individuals without whose efforts this center would not have been established and could not have flourished. In the late 1980s, I went to then Dean George Dutrow and explained to him my concept for developing a Wetland Center in the School of Forestry and Environmental Studies. His insight and support, along with that of Provost Phillip A. Griffiths, helped bring the Wetland Center into existence.
Together we developed a mission statement, coordinated interest of faculty members from six different departments, and raised a small endowment to provide support for student projects. Our initial efforts were rewarded when, in 1990, Dean Dutrow and I took the proposal for the formal establishment of the Wetland Center to the Duke University Board of Trustees. In the intervening years, the center has grown to include 21 total faculty, 18 staff researchers, eight Ph.D. students, 21 Masters of Environmental Management students, and an annual research budget of nearly $1.5 million. Another key factor in the growth and development of the center came in 1994 when the School of Forestry and Environmental Studies, renamed the Nicholas School of the Environment, moved into the new Levine Science Research Center. Dean Norm Christensen worked with us to provide ample research and office space, allowing the center to grow and develop a strong research base within NSOE. We can now look forward to tackling the wetlands issues of the future.
Please drop us a note to let us know what’s on your minds in the wetlands/aquatic area, and stop in to see our new facilities when you get the chance.
- — Curtis J. Richardson,
- Director, Duke Wetland Center
Wetland Center on the Web
he
Duke University Wetland Center is pleased to announce our new web page is up
and running. The address is www.env.duke.edu/wetland.
The site contains general information about the Wetland Center and can also take visitors out of the laboratory and on an Everglades field trip.
The center’s site includes detailed summaries of our current research, publications and presentations, course offerings, information about our faculty, staff and students, and links to other wetland organizations throughout the world.
Other features of the site include Wetland Center job openings and a calendar of upcoming events. Plans to make issues of WetlandWire, the center’s newsletter, available online are underway.
The site was designed by Greta Guzman, a rising second-year MEM student in NSOE, and is being maintained by Guzman and NSOE student Kirsten Hofmockel.
Send any suggestions for the website to Lisa Blumenthal, Duke University Wetland Center, Nicholas School of the Environment, Box 90333, Durham, NC 27708-0333.
Research News
ERIM teams up with Duke University to conduct groundbreaking water research
he
Duke Wetland Center and the Environmental Research Institute of Michigan (ERIM)
have recently begun a joint research project in south Florida, Monitoring Regional-Scale
Hydrologic Processes in the South Florida Ecosystem, funded by both the National
Science Foundation and the U.S. Environmental Protection Agency.
The project will combine field hydrology and ground-truthing with remote sensing radar imagery data to study changes in the patterns of surface-water inundation between Rookery Bay Estuary (Naples, Florida) and the Everglades National Park (ENR) during the past 20 years. Ground-truthing is important in interpreting remote sensing radar imagery. The response of radar to the earth’s surface varies according to vegetation communities, standing water, soil type, soil moisture, and texture of the soil surface.
Wetland Center researchers will establish 15 new continuously-recording water-depth stations to complement 40 existing stations managed by the South Florida Water Management District, the U.S. Geological Survey and ENR. Once the radar images are calibrated to present hydrologic conditions, the investigators will study images collected over the past 20 years to look at changes in surface-water inundation patterns as a result of changes in land use and water management policies.
The results of this study will be used to verify existing surface-water flow models in south Florida and to model the impacts of road and canal construction on the Everglades. After site selections are finalized, installation of the new stations will begin.
— Ed Romanowicz, Ph.D.
| Everglades paleoecology study:
Preliminary results of calibration sets and soil cores from WCA-2A
Right - Kevin Nicholas, Jason Lynch and John Zahina pulling up peat core for analysis from Everglades WCA-2A. |
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ntroduction:
The Everglades have experienced major anthropogenic changes in both hydrology
and nutrient inputs over the past 100 years. Although there is much ongoing
research of this wetland, the status of the ecosystem before human intervention
and the relative effects of nutrients and hydrology on changing vegetation and
water quality are not well understood.
In the last several decades, nitrogen- and phosphorus-enriched agricultural drainage has been pumped into the northern water conservation areas from the Everglades Agricultural Area. The bulk of the nutrients are discharged into Water Conservation Area 1 (WCA-1) and WCA-2A, creating a phosphorus gradient of enrichment. Phosphorus levels in the water column and soils generally decrease in the downstream or southerly direction. Along with the P enrichment in the northern part of WCA-2A, there has been a shift in plant species composition to southern cattail from the native sawgrass and slough communities. There have also been major changes to the hydrology of the system, but these are not as well understood.
Paleoecology: Paleoecological methods can provide a wealth of information about the Everglades ecosystem. Dating of recent sediments and soils is accomplished using gamma and alpha spectroscopy (to measure lead-210 and cesium-137). Pollen, seed, and phytolith analyses of dated sediments or soils can provide information on plant community development and changes through time. Other paleoecological methods such as diatom stratigraphy, chrysophyte cyst abundance, charcoal analysis of sediments, organic carbon and nutrient analysis of sediments or soils, and measurement of various metals (including heavy metal accumulation in the peat soils) can be used to characterize the original ecosystem and investigate both the direct and long-term trends resulting from changing environmental variables due to climate and human intervention. All of these indicators are being used in developing transfer functions for environmental variables by canonical correspondence analyses and weighted-averaging regression models. Transfer functions are used when comparing calibration sets from existing environments to down-core changes in microfossil indicators.
Diatoms: Diatoms are particularly useful for paleoecological research because of a species-specific silica shell (frustule) that is often preserved in the stratigraphic record. Presence or absence of individual species and diatom assemblages can be interpreted as indicators of water quality changes such as eutrophication (nutrients), hydroperiod, pH, and salinity fluctuations. Diatoms contribute as a dominant algae group in the periphyton of the Everglades.
Objectives of Paleoecological Studies: The two objectives of this project are: 1) to calibrate indicators such as pollen, seeds, and diatoms to current areas of different nutrient inputs (and across nutrient gradients), different vegetation cover, and different hydrology patterns; and 2) to analyze sediment cores from different areas of the Everglades (primarily WCA-2A and -3A) to determine historical vegetation cover and water quality changes through time over the past 100-500 years in relation to historical changes in anthropogenic influence to the areas, including changes in the fire history of the Everglades. These analyses will provide evidence of the relative effects of multiple stressors on this aquatic ecosystem as well as provide a pre-disturbance "reference" for Everglades restoration.
Funding: This project is funded by the Everglades Agricultural Area Environmental Protection District. The principal investigator is Dr. Curtis Richardson.
- Sherri Cooper, Ph.D.
Meet The Faculty
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Dr. Richardson’s research interests in applied ecology center on long-term ecosystem response to large-scale perturbations such as acid rain, toxic materials, flooding, or nutrient additions. He has specific interests in wetland ecosystems, phosphorus nutrient dynamics, and the effects of environmental stress on plant metabolism and growth. Major research focuses on wetlands as nutrient sinks and transformers. His current research activities include: (1) the effects of nutrient additions and hydrology on Everglades phosphorus retention and community changes; (2) heavy metal sorption, storage, and removal from pocosin peatlands; (3) wetland development trends in the southeastern United States; and (4) the effects of highway construction on wetland functions.
Email: curtr@duke.edu
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Dr. Cooper’s interests include using paleoecological tools to re-create the history of water quality and vegetation changes in aquatic systems related to both climatic influences and anthropogenic effects. Her specialties include estuarine systems and diatom analysis. Cooper’s current research is focused in two areas: (1) the recent history of the Everglades to re-create vegetation (using pollen and seeds), water quality, and fire histories over the past 200 years for use in restoration plans; and (2) the water quality history of the Neuse and Pamlico River estuaries of North Carolina using diatom analysis and geochemical techniques.
Email: slcooper@duke.edu
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Dr. Romanowicz’s research interests are surface and groundwater hydrology with a particular emphasis on wetland hydrology and groundwater/lake interactions. Presently, Romanowicz is studying the modern and paleohydrology of the Everglades. In addition he is working with the Environ-mental Research Institute of Michigan to develop remote sensing as a tool for investigating the effects of land use changes on the surface hydrology of the Everglades.
Email: earomano@duke.edu
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Dr. Vaithiyanathan’s research activities have focused on understanding the biogeochemical cycling of nutrients and trace metals in aquatic systems. He has carried out laboratory and field research in Indian rivers, Chesapeake Bay estuaries, Canadian shield lakes, and floodplains of the Parana River and the Florida Everglades. His recent work has centered on the impacts of agricultural runoff on the nutrient dynamics in the Everglades. He is a senior scientist at the Duke Wetland Center field station in Florida.
Email: panchabiv@hotmail.com
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Meet The Research Associates
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Dr. Bachand is interested in developing management methods to improve the water and wastewater treatment capabilities of constructed wetlands. Previously, he has developed management methods and design goals to improve nitrogen removal within constructed wetlands. Currently, he is investigating ways to improve phosphorous removal capabilities of constructed wetlands by in-marsh addition of chemical coagulants, studying both the effectiveness and ecological impact of these applications. Bachand’s research uses large-scale field experiments in combination with small benchscale experiments. In this way, he is able to study both the real-world effects of various manipulations and management methods as well as the fundamental mechanisms involved.
Email: pbachand@duke.edu
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Dr. Flanagan's interests are systems ecology and applied ecology with emphasis on impact assessment, wetland restoration, nonpoint pollution control, and constructed wetlands for wastewater treatment. Currently, Flanagan's research is examining the effects of highway construction on the ecosystem function of coastal wetlands in North Carolina. Future research includes the optimal placement of restored wetlands to improve water quality at the watershed level.
Email: nflanaga@duke.edu
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Dr. Huvane’s research involves utilizing paleoecological techniques to develop recent (decades to centuries) and long-term (millennia) environmental histories of aquatic and forested ecosystems. Her work has included the use of diatom remains in lake sediments to quantitatively reconstruct environmental variables such as lake-water pH and alkalinity. She has also examined charcoal and pollen records in lake sediments to infer fire regimes on local and regional scales. Currently, Huvane is studying the ecosystem history of Florida Bay to infer past water quality conditions, including salinity and nutrient status, in conjunction with researchers at the USGS in Reston, VA.
Email: jhuvane@duke.edu
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Dr. Nunnery’s interests are in wetland restoration ecology and applied wetland ecology. His past research activities have included the quantification of sediment accumulation in forested riverine wetlands and the assessment of highway construction on wetland functions. Currently he is working on several Everglades projects, which include monitoring changes in soil chemical and physical properties in nutrient-enriched areas and the effects of agricultural runoff on native plant growth.
Email: knun@duke.edu
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Faculty Notes
Dr. Sherri R. Cooper, Assistant Research Professor, presented two posters at professional meetings earlier this spring. "Water Quality History of the Neuse and Pamlico Estuaries" appeared at the first annual Water Resources Research Conference in Raleigh, NC. The poster, "Paleoecological Study of the Neuse and Pamlico Estuaries," was presented at the spring meeting of the Southeast Estuarine Research Society in Augusta, GA. In April, Cooper gave two lecture presentations: "Using Geochemical and Fossil Indicators to Reevaluate Water Quality Histories of North Carolina Estuaries" as part of Duke University’s Quaternary Ecology seminar series, and "The History of Water Quality in the Pamlico and Neuse River Estuaries as Determined Using Paleoecological Methods" for the Duke chapter of the American Wetlands Research Association. On June 4, Cooper gave a talk entitled, "Paleoecological Study of the Neuse and Pamlico Estuaries" to the Water Resources Research Institute Board of Directors in Raleigh, NC.
Dr. Jacqueline K. Huvane, Dr. Sherri R. Cooper and Laura Pyle presented the poster "Diatoms as Paleoecological Indicators of Environmental Change in the Florida Bay Ecosystem" at the 1998 Florida Bay Science Conference, May 12-14, at the University of Miami, FL.
Dr. Curtis J. Richardson presented the results of phase one of a Duke Wetland Center study of highway effects on wetlands to the Water Resources Research Institute April 10 at North Carolina State University in Raleigh. He also presented "The Ecological Status of the Everglades: Assessing Effects of P Additions on Restoration Potential" at the 19th annual meeting of the Society of Wetland Scientists in Anchorage, AK, in June and "The Ecological Status of the Everglades: Assessing Effects of P Additions and Hydrology" at the joint meeting of the American Society of Limnology & Oceanography and the Ecological Society of America in St. Louis.
Student News
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King is both a student and staff member at DUWC. He joined the Center’s staff in May 1996 immediately after graduation from the NSOE master’s program with a specialization in water quality management. The following year he began work on his Ph.D. in applied community ecology. King’s research interests include the relationship between water/habitat quality in wetlands and aquatic biota, particularly microinvertebrate communities. His work deals primarily with perturbation theory and how it relates to application in a bioassessment framework. His current projects focus on the response of stress-tolerant macroinvertebrate communities to anthropogenic perturbation, specifically experimental and observational investigation of eutrophication and habitat alteration in the Everglades, and assessment of the effects of highway construction on macroinvertebrate assemblages in oligohaline marshes in North Carolina. |
• Recent & upcoming publications: King, R.S. and D.A. Wrubleski. 1998. Spatial and diel availability of flying insects as potential duckling food in prairie wetlands. Wetlands 18:100-114. King, R.S. and J.C. Brazner. 1998. Implications of trophic status on insect communities of coastal wetlands in Green Bay, Lake Michigan, USA. Journal of Great Lakes Research (In review).
• Recent presentation: King, R.S., C.J. Richardson, and K. Nunnery. Methods and metrics for assessment of wetland macroinvertebrate community response to highways. 45th Annual Meeting of the North American Benthological Society, San Marcos, TX. Presented May 29, 1997.
Email: rking@duke.edu
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This was Jensen’s second year at the Wetland Center. Before coming to Duke, she spent a year in Costa Rica teaching English and Environmental Education for the non-profit organization WorldTeach. In her thesis research she has created a calibration set correlating pollen assemblages with vegetation and nutrients in the Everglades Water Conservation Area-2A. Jensen received her Master’s degree in May 1998. This summer she will become co-director of the Vince Shute Wildlife Refuge in Orr, MN. |
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This was Hanchey’s first year as DUWC student, and he was also a teaching assistant. His research interests include the ability of plants to use root microsites and how this affects their survival in wetland soil conditions. Hanchey plans to teach college after his graduation, and he is also interested in public education about the value of wetlands preservation. • Upcoming publication: Hanchey, M.F. 1998. Habitat affinities of a small mammal community in Johnson County, Texas. Texas Journal of Science (In press). Email: mfh@duke.edu |
Upcoming Center Events
| July 19 | Presentation by Dr. Curtis J. Richardson, "Effects of Phosphorus Additions on Restoration and Creation of Everglades Wetlands," VII International Congress of Ecology, INTECOL, Florence, Italy. |
| July 30 | Presentation by Dr. Sherri R. Cooper, "An Historical Perspective on Water Quality in the Neuse and Pamlico Estuaries," Duke University Marine Lab, Beaufort, NC, time TBA. |
| August 12-13 | EPA Workshop on monitoring the ecological performance of stream corridor and wetland restoration, including a presentation by Dr. Curtis J. Richardson on indicator development. The McKinnon Center, North Carolina State University, Raleigh, NC. |
William Mitsch concludes Wetland Center Spring Distinguished Lecture Series
Dr. William Mitsch, Professor of Natural Resources and Environmental Science at The Ohio State University, gave the final talk in this year’s Duke Wetland Center Spring Distinguished Lecture Series on April 20.
In his lecture, "Mother Nature and Father Time: Chief Contractors in Wetland Design," Dr. Mitsch focused on how constructed wetlands tend to "self-design" over time to reach a steady-state that is similar to natural systems having the same regime of environmental factors.
Previous lecturers this season included Dr. Bert G. Drake of the Smithsonian Environmental Research Center ("Effects of Elevated CO2 on Plants and Ecosystem Processes in a Chesapeake Bay Wetland and Florida Scrub-Oak") and Dr. Eville Gorham, Regents’ Professor of Ecology and Botany at the University of Minnesota ("The Role of Northern Peatlands in the Global Carbon Cycle, and Likely Responses to Global Warming").
The schedule for the 1998-99 Series, which will be held at the Levine Science Research Center on the Duke University campus, will be announced in the next newsletter.
