SFS Annual Meeting

5/20/2019  |   09:00 - 09:15   |  250 AB

DETECTING DIFFERENCES IN NITROGEN FLOW IN ECOSYSTEM-SCALE EXPERIMENTS: A NEW APPROACH TO MODELING ISOTOPE TRACER ADDITIONS IN STREAM ECOSYSTEMS Isotope tracer additions are a powerful tool for estimating nutrient flows in stream ecosystems. To date, these studies have been descriptive in nature and have estimated trophic fluxes using simple models in a piecemeal approach. A successful analytical framework needs to be able to provide flux estimates and associated errors that account for the interdependence of parameter estimates among all compartments, the uncertainty in the diet of consumers, and the over-enrichment of compartments that feed selectively. Here, we present a new, holistic modeling approach based on Bayesian Hidden Markov Models, for the analysis of 15N-NH4+ tracer data in 2 Trinidadian streams in which light and fish populations were experimentally manipulated. This modeling approach allows estimation of uncertainty associated with all N fluxes, propagates error when estimating derived parameters, quantitatively compares alternative models of food web structure, and statistically compares parameter estimates across experimental treatments. We also compare the results of this new approach with estimates derived from historical techniques. This method enables rigorous statistical estimation of nutrient fluxes and ecosystem properties and thus provides a powerful new tool for assessing how whole-stream, experimental manipulations effect food web structure and function.

Steven Thomas (Primary Presenter/Author), University of Alabama, sathomas16@ua.edu;


Mattieu Bruneaux (Co-Presenter/Co-Author), matthieu.bruneaux@gmail.com, matthieu.bruneaux@gmail.com;


Sarah Collins (Co-Presenter/Co-Author), University of Wyoming, sarah.collins@uwyo.edu;


Alexander Flecker (Co-Presenter/Co-Author), Cornell University, Ithaca, NY, USA, asf3@cornell.edu;


Rana El-Sabaawi (Co-Presenter/Co-Author), University of Victoria, rana@uvic.ca;


Andrés López-Sepulcre (Co-Presenter/Co-Author), Cornell University, lopezsepulcre@gmail.com;


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5/20/2019  |   09:15 - 09:30   |  250 AB

HOW TO THINK ABOUT HYPORHEIC EXCHANGE IN GRAVEL BEDDED RIVERS (WITH ATTENTION TO IMPLICATIONS FOR BIOGEOCHEMISTRY) Hyporheic exchange – the continuous, bi-directional exchange of water between a stream channel and underlying alluvium – is now recognized as a critical driver of stream ecosystems. When conceptualizing hyporheic exchange in expansive hyporheic zones (HZs) associated with coarse-grained river beds, researchers and managers sometimes default to an assumption of homogeneity, failing to consider the temporally dynamic and heterogeneous nature of upwelling hyporheic water with respect to temperature, dissolved constituents, and other characteristics. Further, when the HZ is conceptualized as single, homogenous transient storage zone, the diversity of water characteristics and habitats within the HZ is overlooked. A conceptual model of hyporheic exchange that incorporates the hydrologic age distribution of water stored in the HZ and the residence time distribution of water discharged from the HZ underscores the spatially diverse and temporally dynamic characteristics of upwelling hyporheic water. We present such a conceptual model, focusing on variation in ratios of water exchange rates and storage as a function of residence time and water age. Incorporating such hydrologic rigor when considering hyporheic exchange aids in the design, implementation, and interpretation of research related to hyporheic processes.

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


Scott O'Daniel (Co-Presenter/Co-Author), Confederated Umatilla Tribes, scottodaniel@ctuir.org;


Katie Fogg (Co-Presenter/Co-Author), Montana State University, s.katie.fogg@gmail.com;


Byron Amerson (Co-Presenter/Co-Author), Montana State University, byron.amerson@gmail.com;


Ann Marie Reinhold (Co-Presenter/Co-Author), Montana State University, Montana Institute on Ecosystems, reinhold@montana.edu;


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


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5/20/2019  |   09:30 - 09:45   |  250 AB

DO US STREAM NITROGEN CONCENTRATIONS REFLECT CHANGING INPUTS OVER TIME? RESULTS FROM THE U.S. EPA NATIONAL RIVERS AND STREAMS ASSESSMENTS (2000-2014) The US EPA National Rivers and Streams Assessment (NRSA) surveys allow for the examination of large-scale changes in stream nutrient concentrations over time. A recent inventory of N inputs to HUC8 watersheds over time showed that while nitrogen (N) input to the entire continental US was similar in 2002 and 2012, N inputs increased in much of the Central Plains, decreased in the eastern US and showed little change across most of the West. We examined temporal and spatial variations in total nitrogen (TN) concentrations in a spatially-balanced survey of over 3,000 wadeable streams in the NRSA between 2000 and 2014. At the national scale, TN concentrations did not change significantly over this time, consistent with the lack of a national trend in N inputs for the entire US. Streams in the Central Plains had significantly greater TN concentration than streams in the West and Appalachians, reflecting the pattern in N inputs for those areas. Surveyed stream chemistry will be combined with national nitrogen input spatial data to model the response to changes in landscape nutrient loading at regional and finer scales.

Jiajia Lin (Primary Presenter/Author), National Research Council/ US EPA, jlin42@outlook.com;


Ryan Hill (Co-Presenter/Co-Author), US Environmental Protection Agency, hill.ryan@epa.gov;
Ryan Hill is an aquatic ecologist with the U.S. EPA Office of Research and Development. He is interested in how watershed conditions drive differences in freshwater diversity and water quality across the United States. He has worked extensively with federal physical, chemical, and biological datasets to gain insights into the factors affecting water quality and biotic condition of freshwaters across the conterminous US. He has also worked to develop and distribute large datasets of geospatial watershed metrics for streams and lakes for the Agency (EPA’s StreamCat and LakeCat datasets). Ryan completed his PhD in Watershed Ecology at Utah State University in 2013 with Dr. Chuck Hawkins. He was an ORISE postdoctoral fellowship at the U.S. EPA from 2014-2019 before joining the EPA in 2019.

Robert Sabo (Co-Presenter/Co-Author), US EPA, Sabo.Robert@epa.gov;


Alan Herlihy (Co-Presenter/Co-Author), Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Corvallis, OR, alan.herlihy@oregonstate.edu;


Marc Weber (Co-Presenter/Co-Author), US EPA, Pacific Ecological Systems Division, Corvallis, OR, weber.marc@epa.gov;


J. Renee Brooks (Co-Presenter/Co-Author), EPA Western Ecology Division, Brooks.Reneej@epa.gov ;


Christopher Clark (Co-Presenter/Co-Author), US EPA, Clark.Christopher@epa.gov;


Scott Leibowitz (Co-Presenter/Co-Author), US EPA, Pacific Ecological Systems Division, Corvallis, OR, leibowitz.scott@epa.gov;


John Stoddard (Co-Presenter/Co-Author), U.S EPA, Office of Research and Development, Pacific Ecological Systems Division, Corvallis, OR, Stoddard.John@epa.gov;


Jana Compton (Co-Presenter/Co-Author), US EPA, Pacific Ecological Systems Division, Corvallis, OR, compton.jana@epa.gov;


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5/20/2019  |   09:45 - 10:00   |  250 AB

LOADING AND BIOACCUMULATION OF SELENIUM AND MERCURY FROM MOUNTAINTOP COAL MINING INTO STREAMS AND RIPARIAN FOOD WEBS While mercury (Hg) and selenium (Se) bioaccumulate and are individually toxic to organisms at high concentrations, some studies show reduced rates of Hg bioaccumulation when organisms are fed diets high in both Se and Hg. This has been interpreted to suggest that Se enrichment of diets or entire ecosystems could prevent Hg toxicity. Yet, little is understood about the biogeochemical and bioaccumulation processes that potentially lead to this putative antagonistic relationship. We examined relationships between Hg and Se in Central Appalachian streams with variable Se concentration (BDL-70 ug/L) due to mountaintop coal mining. We measured Hg and methyl-Hg concentrations in water, sediment, biofilm, aquatic invertebrates, and riparian spiders across the Se concentration gradient. We found that while Se concentrations were strongly positively correlated with mining extent, mined watersheds generally had lower Hg concentrations. We found that total Hg, methyl-Hg, and Se bioaccumulate, with highest concentrations in macroinvertebrates. We found limited evidence for an antagonistic relationship between Hg and Se at the microbial level. The interaction between these two elements is less conclusive in invertebrates; while methyl-Hg and Se are negatively correlated in cranefly larvae, there is no correlation in spiders.

Laura Naslund (Co-Presenter/Co-Author), University of Georgia, laura.naslund@duke.edu;


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.

Collin A. Eagles-Smith (Co-Presenter/Co-Author), US Geological Survey, ceagles-smith@usgs.gov ;


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


Jacqueline Gerson (Primary Presenter/Author), Duke University, jgerson1@gmail.com;


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5/20/2019  |   10:00 - 10:15   |  250 AB

EVENT-SCALE RIVERINE LOADING OF NITROGEN AND PHOSPHORUS: IMPACTS OF LAND USE AND SEASONALITY ON N:P EXPORT RATIOS Riverine nutrient loads, particularly during high flows, impact ecological processes in receiving waterbodies by altering nutrient concentrations and ratios. Given that nitrogen (N) to phosphorus (P) ratios influence a range of processes, and that anthropogenic activities are shifting the balance of these elements, it is important to understand N and P loading patterns across space and time. While general differences in N and P provenance and riverine loading dynamics are well-established, drivers of variability in intra- and inter-event loading patterns remains poorly understood. Yet these events tend to dominate annual nutrient loads in many climates. With the advent of in situ sensors and novel algorithms to predict N and P concentrations concurrently, opportunity exists to examine event-scale N and P loading patterns. Here we use high-frequency N and P measurements for >350 events, over 5 years, across land uses to quantify riverine N and P loading and N:P export ratios. Initial results demonstrate the importance of event contributions to annual loads for both nutrients, and variability in concentration-discharge relationships for N and P across event sizes, land uses, and seasons that drive important differences in N:P export ratios.

Dustin Kincaid (Primary Presenter/Author), University of Vermont, dustin.kincaid@uvm.edu;


Erin Seybold (Co-Presenter/Co-Author), Kansas Geological Survey, University of Kansas, erinseybold@ku.edu;


E. Carol Adair (Co-Presenter/Co-Author), University of Vermont, carol.adair@uvm.edu;


William Breck Bowden (Co-Presenter/Co-Author), University of Vermont, breck.bowden@uvm.edu;


Julia Perdrial (Co-Presenter/Co-Author), University of Vermont, julia.perdrial@uvm.edu;


Matthew Vaughan (Co-Presenter/Co-Author), Lake Champlain Basin Program, mvaughan@lcbp.org;


Andrew Schroth (Co-Presenter/Co-Author), University of Vermont, aschroth@uvm.edu;


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5/20/2019  |   10:15 - 10:30   |  250 AB

RELATIONSHIPS BETWEEN TRACE METAL-NUTRIENT COLIMITATION IN STREAM BIOFILMS AND SURFACE WATER CHEMISTRY Stream biofilms use complex and diverse element sequestration and assimilation mechanisms for growth and metabolism. Trace metals are incorporated in many mechanisms as enzyme cofactors, to support electron transfer proteins for photosynthesis and respiration, or to produce enzymes that allow for use of less common organic nutrient sources. Much of what is understood about stream nutrient limitation focuses on just N and P, although trace metals support several underlying metabolic pathways that may also cause apparent nutrient limitation. We present data from streams in the Great Lakes region that span a gradient of pristine to urban and low to high inorganic and organic nutrient concentrations. We used trace metal nutrient diffusing substrates (tNDS) with different combinations of elements to identify trace metal-nutrient co-limitation of algae and measured surface water chemistry. Stream biofilms responded to multi-element additions more than single-element additions. Zinc and nickel amended treatments showed increased algal biofilm growth across 60% of streams. Colimitation was observed most frequently in streams with low dissolved inorganic nutrients; however, colimitation was also observed in urban streams. These data suggest that colimitation is common and trace metal-nutrient colimitation is complex and overlooked.

Andrea Fitzgibbon (Primary Presenter/Author), Kent State University , afitzgib@kent.edu;


David Costello (Co-Presenter/Co-Author), Kent State University, dcostel3@kent.edu;


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