SFS Annual Meeting

5/23/2019  |   09:00 - 09:15   |  251 AB

WHAT IS WHOLE STREAM RESPIRATION? Stream respiration is a cornerstone stream ecosystem function, yet respiration is difficult to conceptualize and measure. Here I describe two outstanding questions regarding stream respiration. First is is that we have varying ways of measuring and conceptualizing stream respiration. Oxygen is easy to measure but represents activity of one of a suite of terminal electron acceptors. CO₂ is becoming more prevalent but is not often comparable to O₂ because in streams with pH>6.3 (i.e. [HCO₃] > [CO₂)]) CO₂ travel distance will be half or less of that of O₂ because most of the inorganic C travels as HCO₃ and is thus unexchangeable with the atmosphere. Second is understanding the source of carbon fueling respiration. Streams and rivers are usually heterotrophic, but much of respiration is from newly fixed carbon. Time series methods can partition sources of carbon, yet this approach could benefit from corroboration from more mechanistically focused studies. Respiration will continue to challenge stream ecologists; addressing this difficulty will enable better understand the role of rivers in carbon cycling.

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


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5/23/2019  |   09:15 - 09:30   |  251 AB

WHAT IS WHOLE STREAM RESPIRATION? Stream respiration is a cornerstone stream ecosystem function, yet respiration is difficult to conceptualize and measure. Here I describe two outstanding questions regarding stream respiration. First is is that we have varying ways of measuring and conceptualizing stream respiration. Oxygen is easy to measure but represents activity of one of a suite of terminal electron acceptors. CO₂ is becoming more prevalent but is not often comparable to O₂ because in streams with pH>6.3 (i.e. [HCO₃] > [CO₂)]) CO₂ travel distance will be half or less of that of O₂ because most of the inorganic C travels as HCO₃ and is thus unexchangeable with the atmosphere. Second is understanding the source of carbon fueling respiration. Streams and rivers are usually heterotrophic, but much of respiration is from newly fixed carbon. Time series methods can partition sources of carbon, yet this approach could benefit from corroboration from more mechanistically focused studies. Respiration will continue to challenge stream ecologists; addressing this difficulty will enable better understand the role of rivers in carbon cycling.

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


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5/23/2019  |   09:30 - 09:45   |  251 AB

HETEROTROPHIC REGIMES IN RIVERS: PARTITIONING SOURCES OF ECOSYSTEM RESPIRATION THROUGH A TIME-SERIES ANALYSIS Respiration in streams is controlled by the timing, magnitude, and quality of organic matter (OM) inputs from internal production and external fluxes. Here, we tested how well current understanding of respiration drivers predict seasonal metabolic patterns. To that end, we developed a time-series analysis to estimate the contribution of different OM sources to the whole ecosystem respiration. OM sources analyzed included: long-term storage of OM in the streambed, autochthonous OM related to primary production, allochthonous OM delivered to the stream during discharge events, and seasonal pulses of leaf-fall. The framework considers the timing of the different OM inputs but accounts also for possible storage build-up and delay between OM input and respiration. We applied such analysis to 4 stream reaches, characterized by different catchment size, climate and canopy cover, where multi-annual time-series of estimated ecosystem respiration and ancillary environmental variables (namely, water temperature, discharge, gross primary production and leaf area index) were available. Results generally agree with conceptual predictions, but the detailed analysis of this rich dataset allowed shedding further light on how catchment size and the position control the heterotrophic regimes of streams and rivers.

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


Erin Hotchkiss (Co-Presenter/Co-Author), Virginia Polytechnic Institute and State University (Virginia Tech), ehotchkiss@vt.edu;


Alba Argerich (Co-Presenter/Co-Author), University of Missouri-Columbia, argericha@missouri.edu;
Assistant Professor Stream Ecology

John Kominoski (Co-Presenter/Co-Author), Florida International University, jkominos@fiu.edu;
John Kominoski is an ecosystem ecologist and biogeochemist who studies how effects of diverse types of disturbances interact with other long-term environmental changes to influence ecosystem structure and functions. He is the Lead PI of the Florida Coastal Everglades Long Term Ecological Research program, where his lab studies how coastal biogeochemistry is changing with hydrologic presses from saltwater intrusion from sea-level rise and hydrologic pulses from restoration and storms. The Kominoski Lab also studies how urban coastal ecosystems respond to seasonal changes in hydrology, flood pulses, and sea-level rise.

Diana Oviedo-Vargas (Co-Presenter/Co-Author), Stroud Water Research Center, doviedo@stroudcenter.org;


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


Rachel Scarlett (Co-Presenter/Co-Author), Purdue University, rscarlet@purdue.edu;


Daniel von Schiller (Co-Presenter/Co-Author), University of Barcelona, d.vonschiller@ub.edu;


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


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5/23/2019  |   09:45 - 10:00   |  251 AB

STREAM METABOLISM IN ENVIRONMENTAL FLOW MANAGEMENT: THE LONG TERM INTERVENTION MONITORING PROJECT IN AUSTRALIA An innovative, federally funded project, through the Commonwealth Environmental Water Office, is investigating how to balance water needs for the environment with those of human populations and agriculture in The Murray-Darling Basin (MDB) in eastern Australia. The MDB produces around half of Australia’s food but suffers consistently from insufficient water. A major objective is the measurement and assessment of responses of ecological indicators, including fish, vegetation and stream metabolism, to planned and stochastic stream discharge events. Such knowledge will greatly benefit management of scarce water resources (timing, duration and magnitude of watering actions). Four years of stream metabolism data has now been collected from two to six sites in each of seven sub-catchments of the MDB. This talk will present some highlights in the findings thus far and explore the use of metrics derived from rates of gross primary production, ecosystem respiration and flow to discern the effects of environmental watering actions. In general, stream metabolism rates are at the lower end of the international spectrum and are constrained by both nutrient bioavailability and light climate (high turbidity).

Iris Tsoi (Co-Presenter/Co-Author), University of New England, wtsoi@une.edu.au;


Darren Ryder (Co-Presenter/Co-Author), University of New England, dryder2@une.edu.au;


Ben Wolfenden (Co-Presenter/Co-Author), N/A, Benjamin.Wolfenden@environment.nsw.gov.au;


Ross M. Thompson (Co-Presenter/Co-Author), Centre for Applied Water Science, University of Canberra, ross.thompson@canberra.edu.au;


Fiona Dyer (Co-Presenter/Co-Author), Centre for Applied Water Science, University of Canberra, fiona.dyer@canberra.edu.au;


Yoshi Kobayashi (Co-Presenter/Co-Author), NSW Office of Environment and Heritage, Yoshi.Kobayashi@environment.nsw.gov.au;


Rod Oliver (Co-Presenter/Co-Author), CSIRO / University of Adelaide, rod.oliver122@gmail.com;


Zygmunt Lorenz (Co-Presenter/Co-Author), University of Adelaide, Zygmunt.Lorenz@adelaide.edu.au;


Nicole McCasker (Co-Presenter/Co-Author), Charles Sturt University, nmccasker@csu.edu.au;


Nick Bond (Co-Presenter/Co-Author), La Trobe University, n.bond@latrobe.edu.au;


Michael Grace (Primary Presenter/Author), Monash University , michael.grace@monash.edu;


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5/23/2019  |   10:00 - 10:15   |  251 AB

MIRROR MIRROR: THE ROLE OF HETEROTROPHY IN RUNNING WATERS IS INFORMED BY THE STRENGTH AND VARIATION IN THE RELATIONSHIP BETWEEN ER AND GPP The cumulative metabolism of organic matter (OM) in running waters, captured by ecosystem respiration (ER), can alter the fate of bioreactive elements at landscape to global scales. However, our understanding of what shapes temporal patterns of ER in fluvial systems remains poor. Large datasets of continuous metabolism show that ER and gross primary production (GPP) fluctuate synchronously in some systems, but not in others. We assessed the variation in annual GPP-ER relationships across > 200 US streams and rivers spanning five orders of magnitude in drainage size. The slope of the GPP-ER regression, representing net ecosystem production, was tightly constrained among sites, particularly as drainage size increased. Mirroring between daily GPP and ER, represented by the regression R2, varied from zero to > 0.8 among sites, and tended to increase with drainage area. Finally, the intercept of the GPP-ER regression also varied among sites, but decreased with drainage area, suggesting that as system size increases, larger OM pools support elevated rates of baseline ER. Our results illustrate the utility of exploring GPP-ER coupling and provide insight into how controls over heterotrophic regimes may shift along river continua.

Amy Marcarelli (Primary Presenter/Author), Michigan Technological University, ammarcar@mtu.edu;


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


Lily Kirk (Co-Presenter/Co-Author), University of Florida, lily33@ufl.edu;


Maite Arroita (Co-Presenter/Co-Author), University of the Basque Country, maite.arroita@ehu.eus;


Shai Arnon (Co-Presenter/Co-Author), Ben-Gurion University of the Negev, sarnon@bgu.ac.il;


Michael Grace (Co-Presenter/Co-Author), Monash University , michael.grace@monash.edu;


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


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


Catalina Segura (Co-Presenter/Co-Author), Oregon State University, Catalina.Segura@oregonstate.edu;


Amanda Subalusky (Co-Presenter/Co-Author), University of Florida, asubalusky@ufl.edu;


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


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


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


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5/23/2019  |   10:15 - 10:30   |  251 AB

FLUORESCENCE SENSORS REVEAL IN-STREAM PROCESSING OF DISSOLVED ORGANIC MATTER IN RIVER NETWORKS Levels of fluorescent dissolved organic matter (fDOM) in most freshwater ecosystems fluctuate on a daily basis. Yet the factors driving these changes are poorly quantified. We test the hypothesis that these changes are indicative of in-stream DOM processing, including photo-oxidation, ecosystem respiration, and primary production. To test this hypothesis, we used a network of fDOM sensors deployed in streams and rivers across the United States. We used temperature, shortwave radiation, canopy cover, and turbidity to decompose fDOM time series and disentangle the biotic and abiotic processes. Water clarity was a primary factor controlling fDOM processing, but the impact of turbidity and water color differed. Systems with high turbidity showed evidence of high respiration rates, but low levels of both photosynthesis and photo-oxidation. By contrast, high levels of fDOM in blackwater rivers led to low levels of photosynthesis, but evidence of high rates of photo-oxidation. Decreasing canopy cover and increasing temperature with watershed size were linked to greater diel fluctuation of fDOM. We conclude that overlapping signals of in-stream organic matter processing rates can be decomposed to infer rates of organic matter production and mineralization in freshwaters.

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


Paul Decker (Co-Presenter/Co-Author), University of Florida, phdecker@ufl.edu;


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


Lily Kirk (Co-Presenter/Co-Author), University of Florida, lily33@ufl.edu;


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


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


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


Aron Stubbins (Co-Presenter/Co-Author), Northeastern University, a.stubbins@northeastern.edu;


Matthew Cohen (Co-Presenter/Co-Author), University of Florida, mjc@ufl.edu;


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