Stephen Sebestyen

Title: Research Hydrologist
Unit: 
Address: NRS
1831 Hwy 169 East
Grand Rapids, MN 55744-3399
Phone: 218-326-7108
E-mail: Contact Stephen Sebestyen

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Education

• PhD (2008) State University of New York College of Environmental Science & Forestry, Forest and Natural Resources Management, Syracuse, NY.
• MS (2000) Cornell University, Department of Natural Resources (Program in Biogeochemistry & Global Change), Ithaca, NY.
• BS (1997) Susquehanna University, Department of Geological and Environmental Sciences, Selinsgrove, PA.

Civic & Professional Affiliations

• American Association for the Advancement of Science
• American Geophysical Union
• International Association of Hydrological Sciences

Current Research

My scientific interests focus on understanding how hydrological and biogeochemical processes interact in ecosystems. I study how source variation and landscape processes affect the flow of water and solutes through the environment using traditional hydrological analyses, high-frequency chemical sampling, and isotopic tracers.

I am a research hydrologist with the USDA Forest Service in Grand Rapids, MN. I devote portions of my time to research at the Marcell Experimental Forest (MEF) and national-scale syntheses of data from catchment studies on Experimental Forests and Ranges of the USDA Forest Service. At the MEF, I am co-leader of research planning and co-lead scientist on hydrological and biogeochemical research. I have developed a comprehensive research program that builds upon the 50-year legacy of research at this site. The MEF research watersheds were established to study the ecology and hydrology of peatlands and uplands along the southern fringe of the boreal zone. Using extensive resources at the field site, I pursue research related to the effects of nitrogen pollution on ecosystem functions, carbon cycling in peatlands, understanding effects of climate variability, interactions of dissolved organic matter with mercury and other trace metals, and quantifying effects of landscape disturbance on water and solutes yields. I am a participant in the SPRUCE Experiment (Spruce and Peatland Response Under Climatic and Environmental change), a large-scale, experiment in which above- and below-ground temperatures will be manipulated in a black spruce ? Sphagnum bog at the MEF.

I participate and co-lead data synthesis efforts on catchment studies to investigate stream chemistry responses to climate change, atmospheric deposition, natural disturbance, and forest management practices. The intent of these studies is to broaden understanding to national and global scales.

At the Sleepers River Research Watershed in northeastern Vermont, I have been exploring how sources of stream nitrate and dissolved organic matter (DOM) vary among events, seasons, and years. My research in the northeastern USA also includes studies of nitrate sources, DOM dynamics, and effects of biogeochemical cycles during winter on water and solutes yields from catchments that span the region from New York to Maine.

I also study how the direction, magnitude, and variability of groundwater seepage influences biogeochemical cycles in lakes and wetlands. With past work, I have explored the effects of lakeshore seepage on pore water biogeochemistry, plant communities, and brook trout redds in lakes of the Adirondack Mountains of New York. In several new studies, I work with other researchers to quantify effects of groundwater seepage on lake trophic status.

I collaborate with a broad range of research scientists, graduate students, and undergraduate students on projects at the MEF, across the USA, and abroad. My position as a Forest Service scientist and being adjunct faculty at the University of Minnesota and Bemidji State University allow me to be highly involved with graduate student and postdoctoral research.

Why is This Important

1. The flow of water transfers energy and matter from the atmosphere and terrestrial landscapes to lakes, streams, wetlands, and coastal zones. My scientific interests center on understanding how water and reactive chemicals are transported and transformed in the environment. With an emphasis on catchment science, I study hydrological and biogeochemical cycles to identify ways to effectively maintain water quality and ecosystem productivity. I use multiple approaches (hydrologic, biologic, geochemical, biogeochemical, and isotopic) across range of temporal, spatial, climatic, and ecological settings to study such issues as atmospheric pollutant deposition, forest health, ecosystem acidification, nutrient enrichment of surface waters, and ecosystem response to climate change.
2. The variation of stream nutrient concentrations over event and seasonal time scales reflects complex biogeochemical and hydrological processes that affect ecosystem functions, but more fundamentally, relates to the availability of biologically-essential substances that fuel life cycles in catchments, headwater streams, and downstream water bodies.
3. In landscapes where human activities enrich nutrient availability and affect land use / land cover, my work highlights the need to consider multiple elements and interactions of water and nutrient cycles in the context of coupled hydrological and biogeochemical cycles that control surface water chemistry. For example, I study how the nutrient enrichment of ecosystems by human activities directly affects the forms and concentrations of nitrogen in streams. Understanding the linkages between atmospheric sources of nitrogen to forests and streams helps to inform scientists, land managers, and legislators who seek to protect the valuable natural resources provided by forests.

Future Research

With future projects and collaborations, I will pursue research that:

• Quantifies rates of terrestrial and aquatic biogeochemical transformations to definitively pinpoint the landscape processes that affect water chemistry.
• Determines how sources, transformations, and transport processes interact to control nutrient availability within ecosystems.
• Quantifies how short-term processes that occur at discrete locations and times (the "hotspots" and "hot moments" of biogeochemical processes) are important when considered at the ecosystem level.
• Considers how to "scale up" understanding of hydrological and biogeochemical processes from plot level studies and point monitoring locations to larger landscape units.
• Establishes monitoring and experimental (manipulative) studies to identify how the timing, release, and cycling of solutes in catchments is affected by climatic and land use / land cover changes.

Featured Publications

Additional Online Publications