Sarah J. Nelson

Assistant Research Professor | University of Maine

A current CV

May 2012 CV – S.J. Nelson

Citizen Science and the AcadiaLearning project

In collaboration with Acadia Partners for Science and Learning and Maine Sea Grant, I serve as a lead scientist on this set of projects that provides

Stream Team scientists help students collect invertebrates for mercury analysis.

Stream Team scientists help students collect invertebrates for mercury analysis.

professional development for high school teachers. A series of earlier projects was instrumental in scoping the structure for the citizen science projects and in determining that citizen scientists and high school students can produce high-quality mercury data. The goal of AcadiaLearning is to enable teachers to deliver inquiry-based scientific research projects to their students. Students ultimately sample mercury and other environmental parameters in sites across the Gulf of Maine region.

Funding & Support: Maine Department of Education, NOAA, and Acadia Partners for Science and Learning

Location of selected=

Location of selected study sites at the Schoodic Research Watershed

Initial projects involving student research:

Schoodic Research Fellowship Program, 2008-2009, Are we under-estimating mercury burdens in winter soils? A case study at Schoodic Peninsula, Acadia National Park, Maine (S. Nelson). This work was based on two years of intensive winter watershed geochemistry field courses for high school students.

L.L. Bean Acadia Research Fellowship, 2006, How much is enough? Developing a citizen-based monitoring plan for mercury in paired gauged watershed streams at Acadia National Park (S.J. Nelson). This project evaluated the mercury data produced by students as compared to that produced by professional scientists through paired field sampling. It also determined (statistically) the variability associated with varying time between sampling for streamwater mercury.


My interdisciplinary focus is built upon a foundation of rigorous training in long-term monitoring, as the data manager and quality control/quality assurance officer for the US EPA’s Regionalized Long-Term Monitoring (RLTM) lakes, Temporally Integrated Monitoring of Ecosystems (TIME) lakes, High Elevation (HELM) lakes, the US EPA and NSF-funded Bear Brook Watershed in Maine (BBWM), and the Acadia-PRIMENet research watersheds, for both chemical and hydrological data. These projects demand a high level of understanding of the policy-relevant science of atmospheric deposition research and recovery of acidified ecosystems, coupled with careful investigation of subtle long-term trends. Funding and support for these projects has been provided by: US EPA, US Geological Survey, University of Maine, University of New Hampshire.


Lake sampling.

Lake sampling.

Determining the effectiveness of the Clean Air Act and Amendments for the recovery of surface waters in the northeastern US.

This research is part of the US EPA program to collect long-term data on the trends and patterns of response in surface waters sensitive to acidic deposition. Goals are to:

  1. document the changes and patterns in aquatic chemistry for defined sub-populations and sites that are known to be susceptible to acidification or recovery,
  2. evaluate linkages in changes in surface waters, if any, to changes in deposition that are related to regulatory goals;
  3. characterize the effectiveness of the Clean Air Act Amendments in meeting goals of reducing acidif­ication of surface waters and improving biologically-relevant chemistry in the northeastern US, and
  4. provide information for assessment of the need for future reductions in atmospheric deposition based on the rate of recovery (or not) of the systems under study.

Bear Brook Watershed in Maine. The Bear Brook Watershed in Maine (BBWM) research program is centered on two small first-order adjacent forested stream watersheds in eastern Maine.  The research was begun in the mid-1980s as part of the national agenda of research to determine the effects of acid deposition on surface waters and their related watersheds.  Since then, the BBWM program of research has grown to encompass an array of scientific objectives that include acid deposition, climate change and carbon sequestration, nitrogen saturation, base cation depletion, and studies of the evolution of watershed biogeochemistry under prolonged experimental acidification.

Acadia Research Watersheds: Atmospheric deposition, mercury biogeochemistry (including snow), watershed mass balances

When I began with the PRIMENet (Acadia Research Watersheds) project, the ‘watersheds’ were, in fact, nothing more than two small pieces of flagging tied to trees near the chosen stream sampling site. Over the next three years, I led the teams that delineated watershed boundaries, created and deployed field gear, instrumented the watersheds with soil plots and throughfall, and rain samplers, coordinated with the U.S. Geological Survey to deploy stream gauging stations, and assisted with sampling for several of the individual research projects in addition to my own.

Canon Brook, the system into which Cadillac Brook flows.

Canon Brook, the system into which Cadillac Brook flows.

The goal of our research was to address research questions about mercury, acid rain, and nitrogen saturation developed from prior research. The project design was based on natural differences in forests and soils induced by an intense wildfire in one watershed in 1947. There is no evidence of fire in the reference watershed for several hundred years. We tested hypotheses about controls on surface water chemistry, and bioavailability of contaminants in the contrasting watersheds. The stream water chemistry patterns reflect, in part, the legacy of the intense fire, which, in turn, controls differences in forest vegetation and soil characteristics. These factors result in higher nitrogen and mercury flux from the unburned watershed, reflecting differences in atmospheric deposition, contrasting ecosystem pools of nitrogen and mercury, and inferred differences in internal cycling and bioavailabilty. My MS thesis dealt with throughfall chemistry in the paired watersheds.

These projects (1999-2002) were funded by US EPA and USGS BRD. The results were recently published in a special issue of Environmental Monitoring and Assessment, for which I was a guest editor.

Follow-up funding from the National Park Service (NPS)-Natural Resource Challenge continued long-term monitoring of streams for Hg, N, and major ions, plus focused on modeling atmospheric deposition (particularly for mercury) based on landscape factors (2002-2005). Long-term stream monitoring was continued through 2006 with student citizen scientists.  

A snow sampling campaign at Acadia.

A snow sampling campaign at Acadia.

I received one (of four) Canon National Parks Science Scholarships in 2003, for my PhD research project, entitled: Closing the loop on hydrologic and mass balances for a temperate forested park. This project evaluated mercury deposition, transport, and flux in snow. Read more about the Canon Scholars program here.

Reports (See my CV or publications, at right, for peer-reviewed articles): 

  • Nelson, S.J., August 2006. Quicksilver from the skies: mercury in snow at Acadia National Park. Acadia Partners Report 2006-01. Published online:
  • National Park Service, 2002.  Natural Resources Challenge-NRPP, Correlating predictive contaminant deposition maps with streamwater chemistry at Acadia National Park. Project PMIS Number 75017. (J.S. Kahl, S. J. Nelson, I. J. Fernandez)
  • Nelson, S.J., J. S. Kahl, I. J. Fernandez, K. D. Sheehan, A. Grygo Diamond, K. B. Johnson, K. C. Weathers, February, 2007. Final Report: Understanding atmospheric deposition to complex landscapes at Acadia National Park, Maine, 2002-2005. National Park Service, Northeast Region, Technical Report NPS/NER/NRTR-2007/080.
  • Nelson, S.J., J.S. Kahl, (editors) 2003.  Final Integrated Report: Establishing paired gauged watersheds at Acadia National Park for long-term research on acidic deposition, nitrogen saturation, forest health, and mercury biogeochemistry (1998-2002).  Submitted to US EPA and National Park Service. 
  • Schauffler, M., S. Nelson, K. Johnson, J. S. Kahl, G. Jacobson, and I. Fernandez, 2002. Paleoecological assessment of forest-disturbance in upper Hadlock Brook and upper Cadillac Brook watersheds.   Final report to NPS, Acadia National Park, Bar Harbor, ME.  30p.

National Parks: Resource Condition Assessments/Resource Stewardship Strategy

I co-authored the recently-published Resource Condition Assessment for Acadia National Park (Natural Resource Report NPS/NRPC/WRD/NRR-2008/069). I am also co-authoring three other such reports: for CACO (Cape Cod Nat’l Seashore), BOHA (Boston Harbor Islands), and SAIR (Saugus Ironworks). These reports seek to compile data, coordinate research findings, and perform new analyses of existing data to assess the current state of the Park’s resources, and determine threats and stressors to the resources. I am also working on a Resource Stewardship Strategy for BOHA, in which we will identify and prioritize science-based strategies for achieving and maintaining desired future conditions for the Park.

Looking north from the Canon Brook trail.

Looking north from the Canon Brook trail.

Eastern Lakes Survey resampling

Locations of US EPA's ELS-II lakes, plus 11 VT lakes we added for mercury research.

Locations of US EPA's ELS-II lakes, plus 11 VT lakes we added for mercury research.

Mercury (Hg) contamination of surface waters and biota is widespread in the Northeast.  Although watershed processing of Hg is complex, several research projects have identified landscape factors such as wetland extent and forest type, and chemical co-variates such as dissolved organic carbon (DOC), that are correlated with Hg in surface waters.  We hypothesized that watershed characteristics control Hg concentrations in northeastern lakes.  Specifically, we suggested that low-conductivity, wetland-dominated systems with high DOC concentrations will have higher Hg concentrations than high-conductivity higher trophic-level lakes.  We linked landscape statistics calculated using spatial analysis (GIS) to a regional lake data set that contains total Hg (THg, range=0.1-6.42 ng/L), methyl Hg (MeHg, range=<0.02-0.76 ng/L), and full ion chemistry.  The lake data set was the EPA Eastern Lake Survey II statistical population of lakes in the Northeastern U.S. plus 11 Vermont LTM lakes, all sampled within a single summer index period during 2004.  These same lakes were sampled during 1984 and 1986 by US EPA (though not for Hg). We developed and compared four statistical models predicting THg and MeHg from these sets of variables. 

Funding: Northeastern States Research Cooperative, 2007-2008, Evaluating spatial patterns in mercury and methyl mercury in northeastern lakes: landscape setting, chemical climate, and human influences (S. Nelson, J.S. Kahl, D. Krabbenhoft, N. Kamman)

I also participated in a project that assessed major ion chemistry and pH, plus zooplankton community structure and composition (with funding from US EPA), in the same set of lakes, during the same sampling campaign.

Funding: U.S. Department of Agriculture/Northeastern States Research Cooperative, 2003, Evaluating scope and trends for the base cation decline in surface waters of the northeastern US (J.S. Kahl, J. Stoddard, R. Church, S. Nelson, L. Rustad, K. Webster, I. Fernandez, R. Stemberger)

Report: Rosfjord, C.H., J.S. Kahl, K. Webster, S. Nelson, I. Fernandez, L. Rustad, R. Stemberger, 2006. Final Report: Acidic deposition-relevant changes in lake chemistry in the EPA Eastern Lake Survey, 1984-2004. Submitted to USDA NSRC.

Water chemistry of Maine’s Atlantic Salmon rivers

In 2002, the Mitchell Center began a collaborative research program with the Atlantic Salmon Commission, Maine DEP, and NOAA Fisheries to coordinate research on Maine’s salmon rivers. Work began on three tributaries of the Narraguagus River and has expanded to include tributaries of the Union River (Maine Atlantic Salmon Commission, 2004-2007, Determining trends in water chemistry for two salmon rivers and their small tributaries, 1985-2006 (S. Nelson, K. Johnson)), work later began on tributaries of the Pleasant River and Denny’s River. A survey of all of Maine’s salmon rivers was conducted in 2003 to assess differences in pH and acidity using the same field and laboratory protocol for maximum data comparability. A side project evaluated the effects of road salt on these rivers and streams.



  • Nelson, S.J., K.B. Johnson, E.A. Dziezyk, J.S. Kahl, 2007. Determining trends in water chemistry for two salmon rivers and their small tributaries, 1985-2006. Final Report to the Maine Atlantic Salmon Commission.
  • Maine Atlantic Salmon Commission, 2006, Do water sampling techniques affect aluminum speciation? (K. Johnson, S. Nelson)
  • Nelson, S.J., J.S. Kahl, K.B. Johnson, J. Boothroyd, August, 2005. Final Report: Are road de-icing salts a factor in the chemistry of salmon rivers? 2004 Maine Atlantic Salmon Conservation Fund.

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