SFS Annual Meeting

5/21/2018  |   14:00 - 14:15   |  330 B

EMERGENT METABOLIC REGIMES OF RIVER NETWORKS Recent advances in measuring, modeling, and synthesizing stream metabolic rates are improving our ability to disentangle the hierarchy of controls on primary productivity (GPP) in stream and river reaches. However, we still know very little about the emergent patterns of stream metabolism at river network scales. Here we explore whether the daily variation in metabolism within individual stream reaches culminates in an emergent river network metabolic regime. To estimate river network GPP, we applied a set of modeled productivity regimes common to streams and rivers to individual reaches within simulated Optimal Channel Networks (OCNs). We found that at the river network scale, daily GPP exhibits a bimodal annual regime with seasonal peaks during the spring and summer. Although GPP in headwater streams is relatively low, the cumulative influence of spring peaks in primary productivity across a large number of headwater streams is substantial at the network scale, and river network GPP is often maximized during the spring vernal window. Additional model scenarios will explore how the range and timing of river network metabolism is affected by watershed size as well as future shifts in climate and riparian land use.

Lauren Koenig (Primary Presenter/Author), University of Connecticut, Lauren.Koenig@uconn.edu;


Ashley Helton (Co-Presenter/Co-Author), University of Connecticut, ashley.helton@uconn.edu;


Philip Savoy (Co-Presenter/Co-Author), Duke University, prs15@duke.edu;


Robert O. Hall (Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, bob.hall@flbs.umt.edu;


Emily Bernhardt (Co-Presenter/Co-Author), Duke University, ebernhar@duke.edu;


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5/21/2018  |   14:15 - 14:30   |  330 B

NUTRIENT PROCESSING DOMAINS AS FUNCTIONAL SPACE FOR LOTIC ECOSYSTEMS: THE CASE OF THE UPPER CLARK FORK RIVER, MONTANA The propensity for stream ecosystem to lose or sequester nutrients has been assessed by contrasting the relative roles of transport and uptake across an array of factors. The nutrient processing domain (NPD) concept combines perspectives from wetland science, geomorphology, and stream ecology to propose that different streams, or discrete segments of streams, may occupy distinct realms in functional space characterized by magnitude (absolute rates), efficiency (rates as a percent of inputs), and character (dominant nutrient fate) of biogeochemical processing, manifesting in systems that may act as producers, transformers, compilers, or removers. In the Upper Clark Fork River, MT, river segments of 20-80 km were analyzed to address how they act as NPDs in the context of nitrogen (N) and phosphorus (P) loads. The most upstream reach acted as a producer (25 – 225 mg N/m2/d) across seasons while the reach immediately downstream functioned as a N compiler (net uptake of 10-40 mg N/m2 d), but a producer for P (5-15 mg P/m2/d), with compiler function quantitatively linked to upstream subsidies. Discerning how NPDs emerge and their consequences for longitudinal succession is relevant to conceptual and managerial models addressing stream biogeochemistry.

H. Maurice Valett (Primary Presenter/Author), University of Montana, Division of Biological Sciences, maury.valett@umontana.edu;


Amy J. Burgin (Co-Presenter/Co-Author), University of Kansas, burginam@ku.edu;


Stephen Hamilton (Co-Presenter/Co-Author), Cary Institute of Ecosystem Studies, hamilton@caryinstitute.org;


Kevin McGuire (Co-Presenter/Co-Author), Virginia Tech, kevin.mcguire@vt.edu;


Marc Peipoch (Co-Presenter/Co-Author), Stroud Water Research Center, mpeipoch@stroudcenter.org;


Ryan Sponseller (Co-Presenter/Co-Author), Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden, ryan.sponseller@umu.se;


Emily Stanley (Co-Presenter/Co-Author), University of Wisconsin - Madison, ehstanley@wisc.edu;


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5/21/2018  |   14:30 - 14:45   |  330 B

SEASONAL PROGRESSION OF CONCENTRATION AND UPTAKE OF NITROGEN AND PHOSPHORUS IN A ROCKY MOUNTAIN STREAM As the timing of snowmelt advances in a warming world, determining the seasonal progression of nutrient uptake in high elevation streams will be critical to understanding changes in the nutrient dynamics of these sensitive ecosystems. We measured stream-water concentrations and uptake rates of phosphorus, ammonium and nitrate during the growing season in a third-order stream at 3000m in Colorado, USA where snowmelt timing is advancing by 4 days per decade. In early spring, when snowmelt dominated streamflow, nutrients were at concentrations near their seasonal maximum and uptake was at a minimum. As summer progressed, phosphorus concentrations generally declined while uptake increased. For nitrogen, concentrations and uptake rates were not closely related. Ammonium concentrations decreased until late June, then increased through the end of September before decreasing again. Meanwhile, ammonium uptake rates increased throughout the study period. For nitrate, stream concentrations tracked melting snow, decreasing to low levels at baseflow. Nitrate uptake was below detectable levels throughout the study. In this stream, earlier snowmelt should increase stream uptake of phosphorus and ammonium, but since ammonium concentration and uptake are unrelated, only phosphorus concentrations are likely to decrease.

Derek West (Primary Presenter/Author), North Carolina State University; Rocky Mountain Biological Laboratory, dcwest2@ncsu.edu;


Jared Balik (Co-Presenter/Co-Author), Western Colorado University, jbalik@western.edu;


Brad Taylor (Co-Presenter/Co-Author), North Carolina State University Dept. of Applied Ecology; Rocky Mountain Biological Laboratory, bwtaylo3@ncsu.edu ;


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5/21/2018  |   14:45 - 15:00   |  330 B

RIVER NETWORK SATURATION HYPOTHESIS: FACTORS INFLUENCING BIOGEOCHEMICAL DEMAND OF ENTIRE RIVER NETWORKS RELATIVE TO SUPPLY River networks are important controllers of material transfer from land to ocean. Understanding the factors regulating this function for different gaseous, dissolved, and particulate constituents is critical to assess the local and global effects of climate and land use change. We propose the River Network Saturation hypothesis to generalize how river network regulation of material fluxes changes with flow conditions due to imbalances between supply and demand at network scales. In contrast to terrestrial ecosystems, saturation of river networks is highly variable in time due to the considerable variation in the supply of constituents associated with changes in flow. All river networks become saturated under high flow conditions, but flow thresholds under which saturation occurs depends on the inherent process rates for a given constituent, the presence of saturating kinetics, and the abundance of lentic waters within the river network. As supply increases, saturation at network scales is initially limited by previously unmet demand in downstream aquatic ecosystems. Better understanding of when river networks saturate for different constituents will allow quantification of aquatic function at broader spatial scales and help identify management priorities.

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


Susana Bernal (Co-Presenter/Co-Author), Center for Advanced Studies of Blanes (CEAB-CSIC), Spain, sbernal@ceab.csic.es;


Doug Burns (Co-Presenter/Co-Author), USGS, daburns@usgs.gov;


Jonathon Czuba (Co-Presenter/Co-Author), University of Minnesota, czuba004@umn.edu;


Charles Driscoll (Co-Presenter/Co-Author), Syracuse University, ctdrisco@syr.edu ;


Amy Hansen (Co-Presenter/Co-Author), University of Kansas, amy.hansen@ku.edu;


Robert Hensley (Co-Presenter/Co-Author), National Ecological Observatory Network (NEON) operated by Battelle, hensley@battelleecology.org;


Jacob Hosen (Co-Presenter/Co-Author), Purdue University, jhosen@purdue.edu;


Sujay Kaushal (Co-Presenter/Co-Author), University of Maryland, skaushal@umd.edu;
Dr. Sujay Kaushal is currently a Professor in the Department of Geology & Earth System Science Center at the University of Maryland, College Park, and he has been in this position since 2010. Prior to that, Dr. Kaushal was an assistant professor at the University of Maryland Center for Environmental Science from 2005-2010. His research expertise deals with: investigating causes and consequences of freshwater salinization, understanding the impacts of stormwater management and stream restoration on water quality, elucidating fate and transport of urban pollutants; and tracking sources of nonpoint pollution using geochemical approaches and tracers. Dr. Kaushal has authored over approximately 100 peer-reviewed papers in journals such as Proceedings of the National Academy of Sciences, Nature Reviews Earth and Environment, and Nature Sustainability, and he has received awards such as the UMD College of Computer, Mathematical, and Natural Sciences Junior Faculty Award and the IRPE Prize in limnetic ecology (https://www.int-res.com/ecology-institute/eci-prize-awarding/eci-award-ceremony-2012/). From the perspective of education and training, he was a postdoctoral fellow at the Cary Institute from 2003-2005. He received his PhD from the University of Colorado, Boulder, and he received his bachelors degree from Cornell University.

Lauren Koenig (Co-Presenter/Co-Author), University of Connecticut, Lauren.Koenig@uconn.edu;


Y. Lu (Co-Presenter/Co-Author), University of Alabama, yuehan.lu@ua.edu;


Alessandra Marzadri (Co-Presenter/Co-Author), Center for Ecohydraulics Research, University of Idaho , marzadri@ing.unitn.it;


Peter Raymond (Co-Presenter/Co-Author), Yale University, peter.raymond@yale.edu;


Durelle Scott (Co-Presenter/Co-Author), Virginia Tech, dscott@vt.edu;


Robert Stewart (Co-Presenter/Co-Author), University of New Hampshire, rob.stewart@unh.edu;


Philippe Vidon (Co-Presenter/Co-Author), The State University of New York College of Environmental Science and Forestry, pgvidon@esf.edu;


Ellen Wohl (Co-Presenter/Co-Author), Colorado State University, Ellen.Wohl@colostate.edu ;


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5/21/2018  |   15:00 - 15:15   |  330 B

PERMAFROST DETERMINES SOURCES OF DISSOLVED INORGANIC CARBON IN BOREAL FOREST WATERSHEDS Half of the global carbon pool resides in permafrost, which is thawing from increasing global temperature. Permafrost serves as a barrier to water percolation into mineral soil and restricts surface flow to the upper organic layer. Whereas many solute concentrations are correlated with permafrost extent, we observe similar concentration of dissolved inorganic carbon (DIC) in headwater streams draining catchments with varying extents of permafrost (4-50% permafrost, 5.0-11.7 mg C/L) at Caribou-Poker Creeks Research Watershed (Fairbanks, AK, USA). We hypothesize that streams draining catchments underlain by large extent of permafrost have a greater proportion of DIC from soil respiration. Alternatively, streams draining catchments underlain by low extent of permafrost have a greater proportion of DIC from weathering. In this study, we measured pH and DIC concentration to partition carbonate ions, and quantified ecosystem respiration and diel variation of carbonate species using CO2 sensors. Ecosystem respiration did not vary between streams, and all streams were supersaturated with CO2. Preliminary results support our hypotheses that permafrost in watershed catchments influences the source of DIC and suggests that thawing permafrost has the potential to increase the proportion of DIC from weathering as permafrost thaws.

Rachel Voight (Primary Presenter/Author,Co-Presenter/Co-Author), University of Alaska Fairbanks, rlvoight@alaska.edu;


Jeremy B. Jones (Co-Presenter/Co-Author), University of Alaska Fairbanks, jbjonesjr@alaska.edu;


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5/21/2018  |   15:15 - 15:30   |  330 B

AQUATIC METABOLISM IS AN IMPORTANT DRIVER OF CO2 DYNAMICS IN ARCTIC STREAMS OF SWEDEN Streams play an important role in the carbon (C) cycle, accounting for a large portion of CO2 emissions from inland waters, despite their small areal coverage. However, the relative importance of different terrestrial and aquatic processes driving CO2 evasion from streams remains poorly understood. In this study, we measured CO2 and O2 continuously in seven arctic streams in northern Sweden during the summers of 2015 and 2016 to estimate daily metabolic rates and CO2 evasion simultaneously. Preliminary estimates of stream ecosystem respiration ranged between -3.5 and -10 g O2 m-2 d-1, were comparable to values from the temperate zone, and accounted for a large fraction of the CO2 evaded. While some studies suggest that photooxidation of organic matter is a key pathway for CO2 production in arctic freshwaters, we consistently observed markedly lower CO2 concentrations during the day than at night. Moreover, estimates of gross primary production ranged from 0.2 - 1.4 g O2 m-2 d-1 and explained a substantial part of the diel pattern in CO2 concentrations. Our results indicate that in-stream metabolism plays a large role in the CO2 dynamics of these arctic streams.

Gerard Rocher-Ros (Primary Presenter/Author), Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden. Integrative Freshwater Ecology Group, Centre for Advanced Studies of Blanes (CEAB-CSIC), Blanes, Spain, g.rocher.ros@gmail.com;


Ryan Sponseller (Co-Presenter/Co-Author), Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden, ryan.sponseller@umu.se;


Carl-Magnus Mörth (Co-Presenter/Co-Author), Stockholm University, magnus.morth@su.se;


Maria Myrstener (Co-Presenter/Co-Author), Department of Ecology, Umeå University, maria.myrstener@umu.se;


Reiner Giesler (Co-Presenter/Co-Author), Climate Impacts Research Centre, Department of Ecology and Environmental Science, Umeå University, 981 07 Abisko, Sweden, reiner.giesler@umu.se;


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