Current Projects

Water Quality Benefits of Restoring Wetlands in Agricultural and Urban Landscapes.

The Midwest U.S. is blessed with a temperate climate, abundant rainfall and fertile soils, leading to a highly productive landscape for growing food, corn and soybeans. This high productivity has come at the cost of nutrient enrichment, especially with nitrogen, that has led to declining water quality in the region, the Mississippi River basin and the Gulf of Mexico. Land conversion to agriculture also resulted in drainage and loss of nearly 90% of the wetlands that historically were present on the landscape. We investigate the benefits of restoring wetlands in the agricultural Midwest (Indiana, Ohio) to reduce nutrient loadings and improve water quality in and downstream of the region. With collaborators from Kenyon College (Ohio), we measure denitrification, sediment deposition and nutrient (N, P) accumulation in soils of wetlands and riparian areas restored under the US Department of Agriculture Wetland Reserve and Conservation Reserve Programs. The three-year project is funded by the USDA.

Restoring wetlands in urban environments is even more challenging. In many cases, on-site hydrologic alterations such as levees isolate the wetlands from natural hydrologic pulses while ditches promote drainage of the site. On-site effects are compounded by drastic alteration of the surrounding watershed that leads to increased peak flow, sediment transport and pollutants loadings. We investigate the development of wetland-dependent functions, productivity, biodiversity, carbon sequestration and nutrient retention in a recently restored tidal marsh, Woodbridge River, in New York-New Jersey Harbor USA. The wetland was restored in 2008 by removing the dike and grading the site to promote tidal inundation with saltwater to combat the spread of giant reed, Phragmites communis. With support from the National Oceanic and Atmospheric Administration, U.S. Fish & Wildlife Service and the Office of Natural Resources Restoration (New Jersey Department of Environmental Protection), we measure changes in hydrology, vegetation and soils before (in 2000 and 2001) and following hydrologic restoration of the site. We are pleased to collaborate with HDR Inc., an environmental consulting firm based in Pearl River New York, on this project.

Effects of Climate Change on Tidal Wetlands

Climate change is one the most pressing environmental issues of the 21st century and potential effects include global warming, rising sea level and greater inter-annual variability in regional temperature, precipitation and river discharge. Coastal regions, including tidal wetlands, are particularly susceptible to climate change manifested as rising sea level and greater frequency of storms.

We study the effects of rising sea level, including submergence and salt water intrusion, and increased variability in temperature, rainfall and river discharge on delivery of key ecosystem services provided by tidal wetlands. Services associated with biological productivity, water quality improvement, carbon sequestration and disturbance regulation are measured in tidal salt, brackish and freshwater marshes and tidal forests of the Georgia USA coast. We employ GIS and simulation modeling to predict how climate change will alter the area, spatial distribution and ecosystem services of tidal wetlands along the southeast (GA, SC) coast. Our collaborators include the University of Georgia and University of Houston. Funding to support the work is provided by the U.S. Environmental Protection Agency Science to Achieve Results (STAR) Program, the U.S. Department of Energy through the National Institute for Climatic Change Research (NICCR) and the U.S. National Science Foundation through the Long Term Ecological Research (LTER) Program.

Carbon Sequestration in Wetland Soils

Wetland soils are natural sinks for carbon (C) and they represent one of the largest pools of organic C on earth. Natural and anthropogenic factors such as climate change may alter the carbon balance of these soils, converting them from a sink for atmospheric C to a source of C to the atmosphere. We measure rates of organic C accumulation in a variety of freshwater and estuarine wetland soils, including restored wetlands, to gauge C sequestration across a range of climates, hydrology and vegetation types and soils. Study sites range from peatlands in the north (MI, MN) to subtropical wetlands in the south (Florida Everglades), from semi-arid wetlands in the west (Upper Klamath Lake, Oregon) to highly urbanized wetlands in the east (New York Harbor). We extend our data collection to Europe where wetland soils have been used for centuries as pasture land (Czech Republic) and forestry (Estonia, Finland). We hope to expand this work to include wetlands in Asia, including the Yangtze River delta in China and freshwater wetlands of northeastern China.

Support for this decades-long project has been cobbled together through a variety of research projects and funding agencies too numerous to list. We are pleased to announce two new collaborations to investigate C sequestration in wetlands. One is with Kenyon College to quantify ecosystem services, including C sequestration, of wetlands in the Midwest and northeastern U.S. With funding from the US Environmental Protection Agency (EPA), we will quantify historical and recent rates of C sequestration using radiometric dating techniques, 210Pb and 137Cs, in freshwater wetlands of Indiana, Ohio and Pennsylvania. Our second collaboration is with the US Fish and Wildlife Service to investigate C sequestration in natural and restored tidal marshes of New England, in Maine, Massachusetts, New York and New Jersey. We are appreciative of their support.

Effects of Eutrophication on Freshwater Wetlands

Nutrient over-enrichment or eutrophication is a pervasive problem in streams, lakes, and estuaries, leading to algae blooms, hypoxia and fish kills. Wetlands also are susceptible to eutrophication as increased nutrients (nitrogen-N, phosphorus-P) lead to increased primary production of emergent vegetation, changes in species diversity and alteration of carbon and elemental cycles.

We evaluate the long-term effects of nutrient enrichment on a tidal freshwater marsh by fertilizing Zizaniopsis miliacea (giant cutgrass) plots with N, P and N+P for the past 10 years. Long-term additions of N increase Zizaniopsis aboveground biomass and uptake of N and P but reduce belowground biomass and species diversity. Our findings are similar previous studies of nutrient enrichment in the Florida Everglades where P additions, rather than N, lead to alteration of wetland structure and function. At present, we are extending our studies to include measurements of soil processes (accretion, N&P sorption/desorption) and greenhouse gas (CO2, CH4, N2O) fluxes from fertilized and unfertilized plots.

Our findings indicate that N is the primary limiting nutrient and, hence, the "problem" nutrient affecting tidal freshwater marshes. Considering that these and other tidal wetlands are sinks for N from the surrounding watershed, N enrichment may result in the conversion of these wetlands from a sink to a source of N, increasing the susceptibility of estuaries and shallow water bodies downstream to N eutrophication. We are grateful to US EPA, DOE and NSF for their support of this work.

Indiana University Bloomington
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