6/06/2017  |   11:00 - 11:15   |  302B

TESTING EFFECTS OF LARGE CONSUMERS ON STREAM ECOSYSTEM STRUCTURE AND FUNCTION: SYNTHESIS ACROSS THE SCALER PROJECT Large stream consumers (e.g., fish, crayfish, amphibians) are particularly vulnerable to human-induced extirpation. As part of the MacroSystems Biology SCALER project, we conducted a paired consumer removal/control experiment in streams encompassing 7 unique biomes to test whether changes in macroconsumer communities would affect stream structure and function. We compared consumer communities (biomass, trophic position) to measured changes in ecosystem functions (ecosystem respiration [ER], gross primary production [GPP], ammonium [NH4] uptake) and basal resources (benthic organic matter, chlorophyll-a, macroinvertebrates) at both patch and whole-reach scales. Across all biomes, we found no consistent reach-scale changes in ecosystem functions following consumer exclusion. At the patch scale, there were no consistent changes in structure or function between paired exclusion and control treatments across biomes. Ongoing analyses are assessing cross-biome effects of different consumer feeding groups on ecosystem rates, to test whether algivorous macroconsumers reduce GPP via chlorophyll-a and whether top-down effects of insectivorous macroconsumers ultimately affect GPP, ER, and NH4 uptake via changes in macroinvertebrate communities or biomass.

Kaitlin J. Farrell (Primary Presenter/Author), University of Georgia, farrellkj2@gmail.com;


Amy D. Rosemond ( Co-Presenter/Co-Author), University of Georgia, rosemond@uga.edu;


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


Keith Gido ( Co-Presenter/Co-Author), Kansas State University, kgido@ksu.edu;


Michael B. Flinn ( Co-Presenter/Co-Author), Watershed Studies Institute, Dept. of Biological Sciences, Murray State University, mflinn@murraystate.edu;


Matt Whiles ( Co-Presenter/Co-Author), University of Florida, mwhiles@ufl.edu;


Erica Garcia ( Co-Presenter/Co-Author), Charles Darwin University, erica.garcia@cdu.edu.au;


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


Brooke Penaluna ( Co-Presenter/Co-Author), PNW Research Station, US Forest Service, brooke.penaluna@oregonstate.edu;


Michael Douglas ( Co-Presenter/Co-Author), Charles Darwin University, Michael.Douglas@cdu.edu.au;


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6/06/2017  |   11:15 - 11:30   |  302B

DO RIVERS HAVE RHYTHM? MEASURING AND MODELING THE PRODUCTIVITY REGIMES OF FLOWING WATERS Seasonal variations in gross primary productivity (GPP) are related to climatic conditions in many terrestrial, marine, and lentic systems. The phenology of productivity in these systems has been extensively described, analyzed, and modeled with respect to their primary forcings. The same cannot be said for river ecosystems. Annual regimes of light and temperature are often uncorrelated in rivers due to light attenuation from riparian canopies, sediment loads, or colored organic matter. Intense and frequent storm disturbances in rivers may significantly reduce autotrophic biomass and allochtonous energetic subsidies to river heterotrophs may match or exceed in situ GPP. Therefore, we expect that the seasonality of productivity in river ecosystems can be described as a function of light, disturbance, and nutrient regimes instead of broad climatic patterns. A global effort to measure, synthesize, and model metabolism across many river ecosystems is necessary to disentangle the hierarchy of these controls on freshwater metabolism. Here we report the first attempts at characterizing and modeling the metabolic regimes of rivers with contrasting light, disturbance, and allochtonous input regimes across several hundred U.S. rivers.

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


Jim Heffernan ( Co-Presenter/Co-Author), Duke University, james.heffernan@duke.edu;


Alison Appling ( Co-Presenter/Co-Author), US Geological Survey, alison.appling@gmail.com;


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


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6/06/2017  |   11:30 - 11:45   |  302B

HOW RIVER NETWORK STRUCTURE AFFECTS NITROGEN REMOVAL AND EXPORT Streams and rivers play an important role in watershed nitrogen (N) dynamics. We explore how river network structure – the spatial arrangement of tributaries – may affect N removal and export at the watershed-scale. To represent network structure, we derived Optimal Channel Networks (OCNs) with identical watershed areas and stream densities but varying watershed shapes (i.e., with maximum flow path lengths of 140, 72, and 50 km). For each OCN, we implemented a published N model based on extensive N removal measurements for scenarios spanning a wide range of catchment N loading rates (incoming concentrations from 0.15 µg N L^-1 to 150 mg N l^-1). Similar to previous findings, the fraction of N removed decreased with increasing N loading for all networks. The networks removed similar fractions of N load for both low and high loading scenarios. However, elongated networks removed a substantially higher fraction of N load for intermediate loading scenarios. Watershed shape was also related to the role of large streams in whole-network N removal. Additional model scenarios will explore interactions between network structure, stream density, and heterogeneous N loading.

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


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


Enrico Bertuzzo ( Co-Presenter/Co-Author), University Cà Foscari Venice, enrico.bertuzzo@unive.it;


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6/06/2017  |   11:45 - 12:00   |  302B

Aquatic nitrate retention at river network scales across flow conditions determined using nested in situ sensors Non-point pollution sources are strongly influenced by hydrology and are therefore sensitive to climate variability. Some pollutants entering aquatic ecosystems such as nitrate can be mitigated by in stream processes during transport through the river network. Whole river network nitrate retention is difficult to quantify with observations. High frequency, in situ nitrate sensors, deployed in nested locations within a single watershed, can improve estimates of both non-point inputs and aquatic retention at river network scales. We deployed a nested sensor network in the urbanizing Oyster River watershed in coastal New Hampshire, USA, to quantify storm event scale loading and network scale retention. In the headwater streams, nitrate and chloride concentrations both diluted more with increasing storm size. At the mouth of the watershed, chloride also diluted, but nitrate tended to increase. Nitrate to chloride flux ratios indicate this pattern is due to high nitrate retention during small storms that declines during large storms. Nested sensor networks can improve understanding of the controls of both loading and network scale retention, and therefore also improve management of non-point source pollution.

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


Gopal Mulukutla ( Co-Presenter/Co-Author), University of New Hampshire, gopal.mulukutla@unh.edu;


Christopher Cook ( Co-Presenter/Co-Author), University of New Hampshire , christopher.cook@unh.edu;


Richard Carey ( Co-Presenter/Co-Author), University of New Hampshire, richard.carey@unh.edu;


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6/06/2017  |   12:00 - 12:15   |  302B

Organic carbon quality and quantity during storm events across the Connecticut River watershed Despite recognition that most organic matter enters river networks during storms, studies of stormflow dissolved organic matter (DOM) quality are lacking. To address this knowledge gap, we assessed DOM quality and flux across ten storm events in the Connecticut River watershed, at stream sites in Vermont (n=8) and Connecticut (n=8) ranging in size from first to sixth order. Organic carbon fluxes were determined with in situ sensors and water samples were analyzed for DOM quality using spectroscopy – including PARAFAC analysis. The proportion of terrestrial DOM increased at all sites during storm events, but the quantity and type of terrestrial DOM depended on season and watershed topography. Anthropogenic land use in Connecticut and higher wetland coverage in Vermont drove differences in stormflow DOM quality across regions. The proportion of terrestrial DOM during storms decreased with increasing catchment area, indicating processing of this material within the river network. Most studies of DOM reactivity are conducted under baseflow conditions, but changes to DOM quality during storms means that processing of baseflow DOM is not a good predictor of rates during high flows.

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


Jennifer Fair ( Co-Presenter/Co-Author), Yale University, jennifer.fair@yale.edu;


Ethan Kyzivat ( Co-Presenter/Co-Author), Brown University, ethan_kyzivat@brown.edu;


Serena Matt ( Co-Presenter/Co-Author), Yale University, serena.matt@yale.edu;


Lisa Weber ( Co-Presenter/Co-Author), Yale University, lisa.weber@yale.edu;


Bryan Yoon ( Co-Presenter/Co-Author), Northeastern University, b.yoon@northeastern.edu;


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


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6/06/2017  |   12:15 - 12:30   |  302B

INTERPRETING AND COMMUNICATING LOCAL VS BROAD-SCALE MODEL RESULTS: A CASE STUDY USING PHOSPHORUS AND SUSPENDED SOLID PREDICTION AND ASSESSMENT ACROSS WISCONSIN STREAMS Many of us have encountered the frustrating but reasonable “… but what does your model say about MY stream or lake?” line of questioning. This discrepancy between large-scale models and interest in local issues is pervasive in resource management agencies, where biologists must make local management decisions often based on models developed for a much broader region. In Wisconsin, we have developed a statewide model to predict daily reach-level phosphorus and total suspended solids concentrations, and are using it to assess effects on fish and macroinvertebrates. Each model contains random effects to help tease apart site-specific nuances from state-level trends, and we are beginning to share these nuances with biologists and stakeholders to preempt the “but what about MY stream?” criticisms. Crucial to this communication has been the development of automated reports via RMarkdown for each stream reach, which we will soon pair with a Shiny web application. This talk will summarize each model and how they utilize techniques from macrosystems ecology, and include our thoughts and strategies for effectively communicating the results of broad-scale models at local scales.

Alexander Latzka (Primary Presenter/Author), Wisconsin Department of Natural Resources, Alexander.Latzka@wisconsin.gov;


Matt Diebel ( Co-Presenter/Co-Author), Wisconsin Department of Natural Resources, Matthew.Diebel@wisconsin.gov;


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