SFS Annual Meeting

5/22/2018  |   14:00 - 14:15   |  330 B

PROCESSES AND ENVIRONMENTAL CONDITIONS INFLUENCING THE STABLE ISOTOPE FRACTIONATION FACTOR (ALPHA) OF DISSOLVED OXYGEN DURING RESPIRATION Traditional methods to estimate metabolism are unable to track differences in ecosystem respiration occurring between day and night. New models based on oxygen stable isotope analyses are a promising tool for more precise metabolism estimates. However, these models are sensitive to the oxygen isotope fractionation factor (alpha) used, and alpha may vary among locations and organisms, and under different environmental conditions. We explored the physical-chemical processes that influence the value of alpha related to respiration. We collected rocks and water and incubated them in the dark in sealed-recirculating chambers. Chambers were placed inside temperature-controlled chambers at 13 and 20 C, and at four flow velocities. We used a microflow probe to assess water velocity profiles to indicate thickness of the diffusion boundary layer. The flow boundary was less than 1 mm thick at ? 0.5 cm/s. The value of alpha ranged between 0.985 and 0.995, increasing with flow until a threshold flow was attained and the diffusion boundary layer thickness became less defined with increasing flow. Alpha decreased with a higher temperature. Data suggest that flow and temperature need to be accounted for when using oxygen isotope to estimate respiration

Flavia Tromboni (Primary Presenter/Author), University of Nevada, Reno, ftromboni@unr.edu;


Walter Dodds (Co-Presenter/Co-Author), Kansas State University, wkdodds@ksu.edu;


Sudeep Chandra (Co-Presenter/Co-Author), Global Water Center and Biology Department, University of Nevada, Reno, sudeep@unr.edu;


Simon R. Poulson (Co-Presenter/Co-Author), University of Nevada Reno, poulson@unr.edu ;


Anne Schechner (Co-Presenter/Co-Author), Kansas State University, anneschechner@ksu.edu;


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5/22/2018  |   14:15 - 14:30   |  330 B

SCALING GAS-EXCHANGE FROM LOW TO HIGH-ENERGY STREAMS Estimating gas exchange across the air-water boundary in aquatic ecosystems is a key component to understanding biogeochemical and metabolic fluxes. Most knowledge on gas exchange in streams is based on tracer gas experiments conducted in low slope (<10%), low-energy streams. Globally, however, a significant proportion of stream slopes likely exceed 10%, but we know little how gas exchange scales to these high-energy streams. We combined 638 published estimates of gas exchange (k600, m d-1) from low sloped and sub-alpine streams with 60+ new estimates of k600 from mountain streams to understand how k600 scales from the flatlands to the mountains. Stream slopes ranged from 0.002-19%, stream discharge from 0.001-209 m3 s-1, and k600 from 0.1-4118 m d-1. Gas exchange scaled with stream energy dissipation rate (eD, m2 s-3) and depth, which explained 69% of the variability in k600. In low-energy streams, k600 increased rapidly relative to eD, but that rate decreased with increasing eD. Our findings highlight the high k600 in high-energy streams not accounted for by current models to predict gas exchange in streams globally, which has implications for scaling gas fluxes from streams and rivers to the atmosphere.

Amber Ulseth (Primary Presenter/Author), Sam Houston State University, amber.ulseth@epfl.ch;


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


Hilary Madinger (Co-Presenter/Co-Author), University of Wyoming, hilary.madinger@gmail.com;


Tom Battin (Co-Presenter/Co-Author), Ecole Polytechnique Fédérale de Lausanne, tom.battin@epfl.ch;


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5/22/2018  |   14:30 - 14:45   |  330 B

LONG-TERM STREAM RESTORATION EFFECTS ON ECOSYSTEM FUNCTIONS IN COASTAL PLAIN STREAMS. Instream restoration through coarse woody debris (CWD) addition is a low-cost and simple process that increases retention of organic matter, increases hydrologic complexity, and decreases water velocities. Few restoration projects evaluate efficacy after restoration, and even fewer look at long-term (decadal) responses. Here, we evaluate the long-term efficacy of initial stream restoration 14 years later. Four streams within Fort Benning Military Installation (FBMI), GA were restored with the addition of CWD dams in 2003 and evaluated 1-3y later. Following restoration, nutrient uptake and stream metabolism rates increased, whereas water quality metrics did not change, as compared to 3 unrestored streams. Beginning in spring 2017, we measured ammonium uptake, stream metabolism, and water-quality metrics in all 7 streams. Preliminary results suggest that ammonium uptake, stream metabolism, and water-quality metrics are within the ranges reported 1-3 y post-restoration. In spring and winter, ammonium uptake ranged from 0-0.082 mm/s. Gross primary production rates were low (<0.1 g O2/m2/d), and ecosystem respiration rates ranged from 0.25-198 gO2/m2/d. Data will be collected through fall 2018. Our year-long dataset will be one of the few that assess the long-term efficacy of restoration on stream ecosystem function.

Sam Bickley (Primary Presenter/Author), Auburn University, slb0035@auburn.edu;


Daniel Isenberg (Co-Presenter/Co-Author), Troy University, djisenberg94@gmail.com;


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


Brian Helms (Co-Presenter/Co-Author), Troy University, helmsb@troy.edu;


Jack W. Feminella (Co-Presenter/Co-Author), Auburn University, feminjw@auburn.edu;


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5/22/2018  |   14:45 - 15:00   |  330 B

THE IMPACT OF SUBSTRATE SIZE AND OTHER DRIVERS ON NUTRIENT UPTAKE ACROSS A FIVE-MONTH BIOFILM COLONIZATION SEQUENCE IN EXPERIMENTAL STREAMS AT ND-LEEF Headwater streams play a significant role in the removal and transformation of nutrients which can prevent or delay nutrient export, but partitioning the role of abiotic and biotic drivers controlling retention remains challenging in natural systems. We conducted short-term nutrient additions over a five-month biofilm colonization sequence (June-November) using four 50m experimental streams (Q=~1 L/s) at ND-LEEF, each lined with different substrate (D50: <1mm-5cm). It took two weeks of biofilm colonization for significant differences among streams to emerge; uptake velocities (Vf) for ammonium, nitrate, and soluble reactive phosphorus (SRP) were significantly different, suggesting benthic substrate size influenced nutrient uptake. Chlorophyll a was correlated with ammonium and SRP Vf, while benthic organic matter, as ash-free dry mass, was correlated with nitrate Vf. In November, we quantified changes in nutrient uptake after disturbance (i.e., manual sloughing of biofilm) at low (Q=0.9 L/s) and high discharge (Q=4.1 L/s). Post disturbance, we measured significant nitrate and SRP uptake at low Q, however, there was little measurable uptake at high Q for any solute. Our data suggest that the combination of substrate size, biofilm colonization, and discharge influence instream removal of ammonium, nitrate, and SRP.

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


Jennifer L. Tank (Co-Presenter/Co-Author), University of Notre Dame, tank.1@nd.edu;


Arial Shogren (Co-Presenter/Co-Author), University of Alabama, ashogren@ua.edu;
Assistant Professor, Department of Biological Sciences, University of Alabama

Martha M. Dee (Co-Presenter/Co-Author), University of Notre Dame, mdee@nd.edu;


Matt Trentman (Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, matt.trentman@flbs.umt.edu;


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5/22/2018  |   15:00 - 15:15   |  330 B

WITHIN VERSUS AMONG RIVER VARIATION IN GAS EXCHANGE RATE Knowledge of air-water gas exchange is needed to estimate ecosystem metabolism and greenhouse gas evasion in rivers. Ecologists assume a single value for gas exchange for a given river. Yet rates of gas exchange should vary with time as a function of discharge, but in an unknown way. Here we estimated gas exchange rate (K, 1/d) as parameters in a metabolism model for 237 rivers measured through time. We pooled information on gas exchange as a piecewise linear function of discharge allowing any possible shape between gas exchange and discharge. Median rates of $K$ among rivers fell within published values based on gas tracers; slope and velocity predicted variation in K. Within rivers, K tended to decline with increasing discharge, likely because depth (z) increased faster than variation in turbulence. The degree of decline depended upon the hydraulic geometry of the channel with K declining more quickly with discharge in rivers with high bank slopes Gas exchange velocity (k=z*K, m/d), increased with increasing discharge; however, the relationships varied strongly among rivers suggesting much unexplained variation in how gas exchange respond to changing discharge.

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


Edward Stets (Co-Presenter/Co-Author), US Geological Survey, tedstets@gmail.com;


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


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


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


Jud Harvey (Co-Presenter/Co-Author), U. S. Geological Survey, National Research Program, Reston, VA, USA, jwharvey@usgs.gov;


Charles Yackulic (Co-Presenter/Co-Author), USGS Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, cyackulic@usgs.gov;


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5/22/2018  |   15:15 - 15:30   |  330 B

MORE THAN ONE WAY TO LIMIT ALGAE: TRACE METAL-NUTRIENT COLIMITATION OF ALGAL PRODUCTION Algae use diverse mechanisms to acquire and sequester nutrients to support metabolism and growth. Some mechanisms include the use of trace metals 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 basin that span a gradient of pristine to urban and low to high inorganic nutrient concentrations. We used trace metal nutrient diffusing substrates (tNDS) with different combinations of elements to identify trace metal-nutrient co-limitation of algae. Metal-nutrient co-limitation was observed in streams with low dissolved inorganic nutrients. Chlorophyll a concentrations showed that 80% of streams with low inorganic P were Zn-P co-limited. Net primary production estimates showed that study streams with low inorganic N were Ni-N co-limited. We suggest that while a stream may appear N or P limited, the metabolic mechanism underlying this result may be due to trace metal co-limitation.

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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