5/24/2016  |   10:30 - 10:45   |  314

THE INFLUENCE OF CARBON QUALITY ON NITROGEN REMOVAL ALONG SUBSURFACE FLOWPATHS RECEIVING INPUTS FROM WASTEWATER TREATMENT PLANT EFFLUENTS Wastewater treatment plant (WWTP) effluents are sources of carbon, nutrients and bacteria for receiving streams, which affect in-stream biogeochemical processes and distort the amount and fate of nutrients transported downstream. Previous research shows that receiving streams have a high capacity to nitrify ammonium inputs, whereas they have lower capacity to remove nitrate. We hypothesize that the low quality of organic carbon from effluent inputs limits denitrification in receiving streams. To test this hypothesis, we added a labile carbon source to a set of 12 artificial flumes with hyporheic flow, which were fed with water from a WWTP effluent. The flumes contained gravels alone or gravels with three species of helophytes, a biotic compartment used in stream restoration that can influence carbon quality, water residence time and biogeochemical rates. In this talk, we will present the results of the longitudinal patterns for ammonium and nitrate uptake in the subsurface water and how they change during the experimental carbon addition. Results contribute to improve water quality management strategies by integrating WWTP operation with the bioreactive capacity of receiving streams.

Eugènia Martí (Primary Presenter/Author), Center for Advanced Studies of Blanes (CEAB-CSIC), eugenia@ceab.csic.es;


Miquel Ribot ( Co-Presenter/Co-Author), Center for Advanced Studies of Blanes (CEAB-CSIC), Spain, mribot@ceab.csic.es;


Timothy Vaessen ( Co-Presenter/Co-Author), Integrated Freshwater Ecology Group, Center for Advanced Studies of Blanes (CEAB-CSIC), Blanes, Girona, Spain, t.n.vaessen@ceab.csic.es;


Myrto Nikolakopoulou ( Co-Presenter/Co-Author), Dep. Ecology, University of Barcelona, Barcelona, Spain, mnikolakopo@gmail.com;


Paul Romeijn ( Co-Presenter/Co-Author), School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK , romeijn.p@gmail.com;


Tanja Brandt ( Co-Presenter/Co-Author), Helmholtz Centre for Environmental Research, Leipzig, Germany , Tanja.Brandt@ufz.de;


Esperança Gacia ( Co-Presenter/Co-Author), Center for Advanced Studies of Blanes (CEAB-CSIC), Spain, gacia@ceab.csic.es;


Albert Sorolla ( Co-Presenter/Co-Author), Naturalea Conservacio S.L., albertsorolla@naturalea.eu;


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


Alba Argerich ( Co-Presenter/Co-Author), University of Missouri, alba.argerich@oregonstate.edu;


Francesc Sabater ( Co-Presenter/Co-Author), Universitat de Barcelona, fsabater@ub.edu;


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5/24/2016  |   10:45 - 11:00   |  314

EXAMINING THE ROLE OF DISSOLVED ORGANIC NITROGEN IN STREAM ECOSYSTEMS ACROSS BIOMES Watershed nitrogen exports are often dominated by dissolved organic nitrogen (DON); yet, little is known about the role DON plays in ecosystems. As an organic nutrient, DON may serve as either an energy source or as a nutrient source. One hypothesized control on DON is nitrate (NO3-) availability. Here we examine the interaction of NO3- and DON in streams across three biomes: temperate deciduous and coniferous forests and in a tropical rainforest. Streams ranged in dissolved organic carbon (DOC) concentration (1 mgC/L - 50 mgC/L) and DOC: NO3- ratios (10-700). We performed a series of short-term NO3- additions across multiple streams within each biome. Preliminary results suggest there is considerable temporal variation within temperate forests with DON switching between a nutrient source and an energy source. However, in aseasonal tropical streams DON is primarily used as an energy source. DOC concentrations rarely changed in response to NO3- additions suggesting that the N-rich fraction of the DOM pool is more bioreactive than the C-rich fraction. Contrasting responses of the DON and DOC pools indicate different mechanisms controlling their respective cycling.

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

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


Pavel Kram ( Co-Presenter/Co-Author), Czech Geological Survey, pavel.kram@geology.cz;


Jakub Hruska ( Co-Presenter/Co-Author), Czech Geological Survey, jakub.hruska@geology.cz;


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


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5/24/2016  |   11:00 - 11:15   |  314

SEASONAL PATTERNS IN DENITRIFICATION RATES AS A FUNCTION OF NITRATE AVAILABILITY IN VEGETATED AGRICULTURAL DITCH SEDIMENTS Application of external nitrogen (N) inputs to agricultural systems has increased food production to meet growing demands worldwide. However, excess N inputs also contribute to significant environmental impacts including eutrophication of fresh and coastal waters. Widespread implementation of best management practices (BMPs) that reduce N inputs to aquatic ecosystems are needed. Denitrification is a biologically-mediated removal mechanism that decreases nitrate transport to downstream waterbodies. Recent work demonstrated that ditch sediments planted with Leersia oryzoides have significantly higher denitrification potential than bare sediments or those planted with Typha latifolia. Seasonal factors including temperature, oxygen concentrations, nitrate availability, and organic matter content also influence denitrification rates. In this study, we explored the seasonal effects of nitrate availability on denitrification in agricultural ditch sediments from mesocosms vegetated with L. oryzoides. Denitrification rates were measured as N2 production from intact vegetated sediment cores using Membrane Inlet Mass Spectrometry. We will present denitrification rates as a function of nitrate concentration and temperature in experimental cores across 4 seasons. This study will contribute to future models that predict denitrification rates associated with vegetated ditch BMPs.

Shannon Speir (Primary Presenter/Author), University of Arkansas, slspeir@uark.edu;


Jason M. Taylor ( Co-Presenter/Co-Author), USDA, Agricultural Research Service, National Sedimentation Lab, jason.taylor@ars.usda.gov;


Thad Scott ( Co-Presenter/Co-Author), Baylor University, Thad_Scott@baylor.edu ;


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5/24/2016  |   11:15 - 11:30   |  314

VARIATION IN AMMONIUM UPTAKE RATES THROUGHOUT A TROPICAL WATERSHED: IMPLICATIONS FOR SCALING ECOSYSTEM PROCESSES Quantifying spatial variability in nutrient uptake is critical for evaluating the importance of individual streams to watershed-scale nutrient delivery. Scaling aquatic ecosystem processes like nutrient uptake remains a fundamental challenge, however, because drivers identified at individual sites often fail to explain large-scale patterns. To begin to address this disconnect across scales we conducted pulse ammonium (NH₄) additions throughout the Río Mameyes watershed, Puerto Rico to analyze how NH₄ uptake varies with stream size. Mean reach ambient NH₄ uptake velocities (V_f) ranged from 1.5 – 6 mm/min, although ambient V_f was more variable when rising and falling limbs of the pulse addition were considered separately. We found that NH₄ V_f increased with specific discharge, suggesting downstream changes in biological demand or the nature of transient storage. We observed significant nitrate production during NH₄ addition experiments, but the percentage of NH₄ that was nitrified (12 – 74%) did not scale with stream size. Ultimately, understanding the drivers of nutrient uptake within individual river networks may help bridge the gap between our understanding of site-level processes and large-scale biogeochemical patterns in aquatic ecosystems.

Lauren Koenig (Primary Presenter/Author), University of New Hampshire, lauren.koenig@unh.edu;


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


Janine Ruegg ( Co-Presenter/Co-Author), Brandenburg University of Technology, jrueegg@GMAIL.COM;


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


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5/24/2016  |   11:30 - 11:45   |  314

TEMPERATURE EFFECTS ON STREAM NETWORK NITRATE REMOVAL: EXPLORING PHYSICAL DRIVERS OF SEASONAL VARIATION Research describing patterns of nitrate removal in stream networks is often based on models parameterized to summertime baseflow conditions. We have developed an empirically-based stream network model that incorporates temperature influences on nitrate removal dynamics. The model simulates: a) the effect of stream temperature on stream respiration rate; and b) the subsequent effect of stream respiration rate, along with nitrate concentration, on nitrate removal efficiency (vf den). We simulated nitrate removal dynamics in the North St. Vrain watershed in Rocky Mountain National Park, Colorado, USA under stream discharges and temperatures typical of winter, spring, summer, and fall. As expected, predicted nitrate removal rates are correlated with water temperature and inversely correlated with discharge. Beyond this finding, however, our analysis quantifies the relative influence of discharge vs. temperature in driving seasonal patterns of nitrate removal in the stream network. Thus, our model provides an effective means of developing testable mechanistic hypotheses describing the physical drivers of seasonal variation in stream network nitrate removal.

Geoffrey Poole (POC,Primary Presenter), Montana State University, Montana Institute on Ecosystems, gpoole@montana.edu ;


Sam Carlson ( Co-Presenter/Co-Author), Montana State University, sam.p.carlson@gmail.com;


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


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


Michael Venarsky ( Co-Presenter/Co-Author), Australian Rivers Institute, Griffith University, mvenarsky@gmail.com;


David Walters ( Co-Presenter/Co-Author), United States Geological Survey, waltersd@usgs.gov;
Dr. David Walters is a Supervisory Research Ecologist at the Columbia Environmental Research Center. David has been a research ecologist with the USGS since 2008. Prior to that, he was an ecologist for the U.S. EPA, National Exposure Research Laboratory for 6 years. He is a freshwater ecologist with broad training in stream ecology, human impacts on aquatic ecosystems, and ecotoxicology. His current research topics include food webs and contaminant flux, aquatic-riparian linkages, stream fish ecology, land use and climate change, and invasive species.

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5/24/2016  |   11:45 - 12:00   |  314

TEMPERATURE EFFECTS ON STREAM NETWORK NITRATE REMOVAL: RECONSIDERING THE ROLE OF LARGE STREAMS. A prior stream network modeling effort demonstrated that nitrate removal via denitrification occurs predominantly in smaller (low-order) streams, but shifts towards larger (higher-order) streams as nitrate concentrations increase. We have updated the prior stream network model to incorporate the effect of water temperature on nitrate removal efficiency (vf den). Our revised model represents: a) the effect of stream temperature on respiration rate, and b) the subsequent effect of stream respiration rate, along with nitrate concentration, on vf den. We use measured stream temperatures and associated respiration rates from the North St. Vrain stream network in Rocky Mountain National Park, Colorado to simulate stream network nitrate removal across a range of nitrate concentrations. Our model shows that cool water temperatures and lower respiration rates typical of smaller streams yield decreased vf den relative to predictions from the prior modeling effort. Thus, by incorporating the effects of stream temperature, our model results suggest that prior research has underestimated the importance of larger streams in contributing to whole-network nitrate removal.

Sam Carlson (POC,Primary Presenter), Montana State University, sam.p.carlson@gmail.com;


Geoffrey Poole ( Co-Presenter/Co-Author), Montana State University, Montana Institute on Ecosystems, gpoole@montana.edu ;


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


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


Michael Venarsky ( Co-Presenter/Co-Author), Australian Rivers Institute, Griffith University, mvenarsky@gmail.com;


David Walters ( Co-Presenter/Co-Author), United States Geological Survey, waltersd@usgs.gov;
Dr. David Walters is a Supervisory Research Ecologist at the Columbia Environmental Research Center. David has been a research ecologist with the USGS since 2008. Prior to that, he was an ecologist for the U.S. EPA, National Exposure Research Laboratory for 6 years. He is a freshwater ecologist with broad training in stream ecology, human impacts on aquatic ecosystems, and ecotoxicology. His current research topics include food webs and contaminant flux, aquatic-riparian linkages, stream fish ecology, land use and climate change, and invasive species.

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