SFS Annual Meeting

5/21/2019  |   11:00 - 11:15   |  250 AB

A DAM SIGHT BETTER OR WORSE? HOW CHANGES IN HUMAN AND BEAVER IMPOUNDMENTS AFFECT RIVER NETWORK BIOGEOCHEMICAL PROCESSES There are more than 14,000 dams in New England alone with over 100 of them already having been removed and many more slated for removal in the future. Meanwhile, a resurgence in the beaver population has resulted in the construction of countless dams across New England which has led to the impounding of many streams. We seek to understand how human dam removals and beaver dam construction affect reach-scale biogeochemical processes and what implications there may be for river network-scale nutrient fluxes. We analyzed samples for nutrients and gases in impoundments across northeastern MA as well as estimated aquatic metabolism in a single reservoir and beaver pond. Preliminary results indicate the human reservoir has greater NPP compared to the beaver pond. CH4 concentrations were highest in the beaver pond while N2O and N2 were generally higher in human reservoirs, indicating different dominant processes occurring between impoundments. These results suggest that as river networks transition from being dominated by human reservoirs to beaver ponds, shifts in biogeochemical processes are also likely to occur. With dam removals ongoing and the beaver population increasing, this could have significant impacts on network-scale nutrient fluxes.

Christopher Whitney (Primary Presenter/Author), University of New Hampshire, chris.whitney@unh.edu;


Wilfred M. Wollheim (Co-Presenter/Co-Author), University of New Hampshire, wil.wollheim@unh.edu;


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5/21/2019  |   11:15 - 11:30   |  250 AB

REDUCED FLOWS ALTER NUTRIENT EXPORT OVER MULTIPLE SEVERE DROUGHTS IN SOUTHWEST GEORGIA, USA The Southeastern US is predicted to have warmer summers, more variable precipitation and increased human water demand, increasing the frequency and severity of water scarcity. Since 1994, water-quality constituents have been measured monthly in two adjacent watersheds in southwestern Georgia, USA. Land-use is similar between the watersheds except that Chickasawhatchee creek flows through the second largest wetland complex in Georgia allowing for a greater influence of floodplain activity. We calculated daily yield of water quality constituents under normal conditions across four years (minimum flow 2.57 and .0991 m3/s) and moderate to extreme drought conditions across five years (minimum 0.125 and 0 m3/s) to examine the effect on nutrient transport. Reduced nutrient export was observed during drought years across all constituents with average yearly yield reduced by half or more. During normal years, nutrient exports were largely comparable with a greater reduction in Chickasawhatchee creek during drought years. We attribute this to greater floodplain disconnection and tributary drying caused by low rainfall, greater withdrawals, and consequently reduced groundwater levels. Increased water scarcity could have important consequences for aquatic life through reduced flow and export of biologically important materials to downstream communities.

Chelsea R. Smith (Primary Presenter/Author), The University of Alabama, crsmith5@crimson.ua.edu;


Stephen Golladay (Co-Presenter/Co-Author), Georgia Water Planning and Policy Center at ASU, steve.golladay@jonesctr.org;


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5/21/2019  |   11:30 - 11:45   |  250 AB

STREAM FLOW AND SOLUTE FLUX RESPONSES TO WARMING AND ELEVATED CO₂ IN A BOREAL PEATLAND The Spruce and Peatland Responses Under Changing Environments project is an ecosystem-scale experiment examining the effects of elevated temperature (+0, +2.25, +4.5, +6.75, +9°C) and CO₂ concentrations (+500 ppm) on peatland ecosystem processes, including stream flow and solute dynamics. After three years of warming, stream flow and solute concentrations and fluxes have changed considerably. Stream flow from the +9°C (warmest) treatments was 19-63% lower (depending on the year) than from the +0°C (unheated) treatments because evapotranspiration increased with warming. Total organic carbon (TOC) concentrations in stream water increased with warming; in 2018, mean TOC concentrations were 54 mg/L in the +0°C treatments and 101 mg/L in the +9°C treatments. While there were strong responses in TOC concentrations to warming, nutrient concentrations did not change. Despite higher TOC concentrations, cumulative TOC fluxes were lower with warming in 2016 and 2017 because stream flow reductions with warming dominated the TOC flux response. In the third year (2018), outflow patterns began to shift and TOC fluxes from the +9°C treatments were similar to fluxes from the less-warm treatments. These findings highlight the complexity of peatland stream and solute responses to climate change.

Stephen D. Sebestyen (Co-Presenter/Co-Author), USDA Forest Service-Northern Research Station, ssebestyen@fs.fed.us;


Keith Oleheiser (Co-Presenter/Co-Author), XCEL Engineering, olehe003@d.umn.edu;


Paul Hanson (Co-Presenter/Co-Author), Oak Ridge National Laboratory, hansonpj@ornl.gov;


Natalie Griffiths (Primary Presenter/Author), Oak Ridge National Laboratory, griffithsna@ornl.gov;


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5/21/2019  |   11:45 - 12:00   |  250 AB

SPATIAL AND TEMPORAL VARIABILITY OF NUTRIENT DYNAMICS AND ECOSYSTEM METABOLISM IN A HYPER-EUTROPHIC RESERVOIR DURING WET AND DRY YEARS Climate change is increasing the variability, frequency and severity of precipitation and drought events, with more extreme conditions predicted over the next century. Effects will be pronounced in aquatic ecosystems, where externally supplied resources (e.g., nutrients, organic carbon) drive key ecosystem processes. Yet, we know surprising little about how periods of high and low precipitation affect fluxes of these resources and modulate spatial and temporal patterns of ecosystem function. To address this, we deployed dissolved oxygen probes coupled with high spatial resolution and frequent (daily-weekly) nutrient sampling in Acton Lake, a hyper-eutrophic reservoir with an agricultural watershed. We found that high discharge events during wet years produce ephemeral and spatially explicit effects on both nutrient dynamics and metabolism. Increases in dissolved nutrient concentrations were restricted to areas near stream inlets and returned to pre-storm baseline within days. We found both short-term declines in net ecosystem production and increased ecosystem respiration during individual storm events, and overall higher respiration during wet years. Understanding how hydrologic processes during relatively wet and dry years influence metabolism and nutrient cycling is paramount to preserving ecological integrity and ecosystem services of lakes under future climates.

Tanner Williamson (Primary Presenter/Author), Michigan State University, tanner.williamson@gmail.com;


Michael Vanni (Co-Presenter/Co-Author), Miami University, vannimj@miamioh.edu;


William Renwick (Co-Presenter/Co-Author), Miami University, wrenwick@miamioh.edu;


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5/21/2019  |   12:00 - 12:15   |  250 AB

CARBON AVAILABILITY ENHANCES NITRATE REMOVAL IN TROPICAL MONTANE STREAMS Tropical forests store large amounts of the earth’s terrestrial C, but many tropical streams have low levels of dissolved organic carbon (DOC). Because rates of nitrification are high and nitrate is often abundant relative to temperate streams, energy availability may limit inorganic N uptake. We conducted a series of experiments to explore the influence of DOC availability on tropical stream N cycling. Nutrient pulse additions of NO3 with and without an added C source were conducted in streams of the Luquillo Mountains, Puerto Rico. In the absence of added DOC, NO3 uptake was undetectable or had very long (>1000 m) uptake lengths (Sw). With bioavailable DOC added, NO3 Sw was reduced to 80-150 m, with the shortest lengths resulting from addition of dissolved organic nitrogen (urea). This demonstrates that the availability of DOC can enhance NO3 removal and that DON is a significant energy source in stream N uptake dynamics. Understanding nitrate processing in these streams is important to predict future trends for these montane watersheds, especially those impacted by hurricanes that elevate NO3 concentrations for years post impact.

Bianca Rodriguez-Cardona (Primary Presenter/Author), University of New Hampshire, bianca.rodz.pr@gmail.com;


Adam Wymore (Co-Presenter/Co-Author), University of New Hampshire, adam.wymore@unh.edu;
Dr. Adam Wymore is a Research Assistant Professor at University of New Hampshire.

William H McDowell (Co-Presenter/Co-Author), University of New Hampshire, bill.mcdowell@unh.edu;


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5/21/2019  |   12:15 - 12:30   |  250 AB

MEGAFIRES AND HURRICANES: MULTIPLE STRESSORS ALTER STREAM FORM AND FUNCTION IN SEMI-ARID WATERSHEDS Climate change in the western U.S. is causing larger fires and more extreme precipitation events. When these two changes collide, they create massive ecosystem disturbance, affecting terrestrial and aquatic environments as well as human well-being. In October 2018, such a scenario occurred when the remnants of Hurricane Rosa dumped torrential rain on a two-week old, 610-km2 burn scar in central Utah. The wildfires, flash flooding, and debris flows triggered the evacuation of approximately 10,000 local residents and created a sediment plume in the downstream lake that was visible from space. We collected streamwater samples from 10 watersheds during and after the storm, allowing us to quantify the interactive effects of megafire and extreme rain on aquatic biogeochemical fluxes. We analyzed samples for a broad suite of physicochemical parameters including organic matter concentration and biodegradability, water isotopes, major ions, trace metals, and nutrients. While the burned and unburned streams showed various concentration-discharge relationships, the effects of the megafire were apparent in nearly every parameter we quantified, increasing particulate loading and resulting in a substantial loss of terrestrial carbon, nitrogen, and phosphorus.

Benjamin Abbott (Co-Presenter/Co-Author), Brigham Young University, Department of Plant and Wildlife Sciences, benabbott@byu.edu;


Erin Jones (Co-Presenter/Co-Author), Brigham Young University, erinfjones3@gmail.com;


Jordan Maxwell (Co-Presenter/Co-Author), Brigham Young University, jdmax29@byu.edu;


Trevor Crandall (Primary Presenter/Author), Brigham Young University, crandall.trevor@yahoo.com;


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