SFS Annual Meeting

5/20/2019  |   14:00 - 14:15   |  250 AB

HIGH SUPPLY, HIGH DEMAND: A UNIQUE NUTRIENT ADDITION DECOUPLES NITRATE UPTAKE AND METABOLISM IN A LARGE RIVER Our current understanding of the relationship between nitrate (NO3-N) demand and supply in streams assumes that biological demand for nitrogen (N) remains constant in response to an N addition. This may be true on the scale of hours, but we hypothesize that over longer time (e.g., weeks to months, as with a sustained nutrient addition) biological communities may shift and increase demand in response to increased nutrient supply. To explore this, we treated a six-month controlled N waste release into the Kansas River (conducted by the City of Lawrence, KS) as an ecosystem-scale nutrient and microbial community addition experiment. We deployed four nitrate and dissolved oxygen sensor arrays along a 33 km study reach from January to May 2018 to continuously monitor diel NO3-N and stream metabolism. We evaluated the ratio of N supply to demand through time using the integrated diel NO3-N calculation method. We predict that supply:demand is largest at the start of a nutrient addition event, decreasing with time as the microbial community shifts. If true, this could change our understanding of N processing in streams that experience consistently high nutrient supply.

Michelle Catherine Kelly (Primary Presenter/Author), University of Kansas, michellekelly@ku.edu;


Lydia Zeglin (Co-Presenter/Co-Author), Kansas State University, lzeglin@ksu.edu;


Amy Burgin (Co-Presenter/Co-Author), University of Kansas, burginam@ku.edu;


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5/20/2019  |   14:15 - 14:30   |  250 AB

WHEN BUDGETS DON'T BALANCE: INDICATORS OF SHIFTING CARBON BALANCES AND LESSONS TO LEARN FROM THEM Carbon mass balances represent a useful (if bulky) tool in identifying the flow and fate of carbon in aquatic ecosystems, yet our best efforts to quantify total annual inputs and outputs don’t always work out. A fundamental assumption for any carbon mass balance is that the system is at equilibrium: that annual terrestrial and atmospheric carbon inputs must be equivalent to annual outputs (through carbon export, burial, or emissions). However, internal carbon subsidies (such as large pools of dissolved organic carbon) or changes in the size of the biotic community in a lake can throw off this assumption, and are important to consider especially in face of accelerating climate change. I present data supporting the occurrence of such carbon budget shifts, and discuss their potential implications for understanding lake community shifts.

Soren Brothers (Primary Presenter/Author), Utah State University, soren.brothers@usu.edu;


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5/20/2019  |   14:30 - 14:45   |  250 AB

A PROMISING APPROACH TO SOLVE LIGHT-ASSOCIATED MISSPECIFICATIONS IN RIVER METABOLISM MODELS Light drives variation in riverine gross primary productivity (GPP), but characterizing light regimes at reach scales remains challenging. Additionally, we do not know how ecosystem-scale GPP responds to light; stream scientists use metabolism models assuming either linear or saturating relationships between GPP and light without testing the actual relationship. These misspecifications can cause large errors in GPP estimates. Here we developed a new modeling approach that accounts for process error (PE) during the day (versus generic PE during both day and night) to allow a flexible means of addressing light saturation and to account for misspecified light inputs into metabolism models. We compared three models (i.e., linear GPP-Light & generic PE; saturated GPP-Light & generic PE; and linear GPP-Light & daytime PE) by simulating [O2] data under different light scenarios and evaluating each model’s success in recovering the simulation parameter values. Results showed that only shallow rivers (mean depth ~0.20 m) with low light attenuation (~0.80 m-1) might be light saturated. Across all scenarios, daytime PE had the greatest accuracy and least bias of the three model variants, suggesting it is a promising approach to improve estimates of river metabolism.

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


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


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


Arturo Elosegi (Co-Presenter/Co-Author), University of the Basque Country (UPV/EHU), arturo.elosegi@ehu.eus;


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


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5/20/2019  |   14:45 - 15:00   |  250 AB

RECOGNIZING BOTH DENITRIFICATION AND CONSUMPTIVE PROCESSES IMPROVES WHOLE SYSTEM DIEL N2 FLUX MODELS IN DISCRETE REACHES OF AGROECOSYSTEMS There is considerable interest in enhancing denitrification within intervening aquatic habitats between agricultural areas and downstream aquatic ecosystems to reduce N loading impacts. We conducted a series of experiments to examine how manipulating ditch environments can promote denitrification within agricultural drainage networks. Laboratory incubations demonstrate that ecological (wetland vegetation) and bioengineering (hardwood mulch addition) manipulations significantly enhance denitrification potential within ditch sediments. However, experiments comparing whole system diel N2 fluxes between control and vegetation or mulch manipulations uncovered complex patterns suggesting fluxes may be controlled by the balance of both N2 production via denitrification and consumption driven by physical or biological processes. We expand the current one-station model to a two-station model and investigate potential improvement added by a N2 consumption term to represent biological (N fixation) or physical (bubble formation and N2 scavenging) mechanisms associated with daytime photosynthesis . More work is needed to understand specific mechanisms associated with N2 consumption processes in small agricultural drainages; however this modified diel N2 flux model enhances model fit and increases model utility in systems where discontinuities create severe diel patterns in dissolved gas concentrations and prohibit accurate estimates of N2 flux.

Rachel Nifong (Primary Presenter/Author), Agricultural Research Service, USDA, rachel.nifong@ars.usda.gov;


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


Matt Moore (Co-Presenter/Co-Author), USDA, Agricultural Research Service, National Sedimentation Lab, matt.moore@ars.usda.gov;


Jerry Farris (Co-Presenter/Co-Author), Arkansas State University, jlfarris@astate.edu;


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

WETLAND BIOGEOCHEMICAL RESPONSES TO CLIMATE CHANGE PREDICTED SCENARIOS Wetlands are one of the world's largest known carbon sinks, while comprising only 2-6% of the Earth's surface. Carbon in wetlands is stored through decomposition and sedimentation of organic matter and absorption of CO2 from the atmosphere by soil microbes. As climates continue to change and some regions are expected to experience increased periods of drought, wetlands are predicted to become carbon sources instead of carbon sinks. Increased drought periods are also predicted to cause more frequent wetland wildfires. We examined changes in soil microbial biomass, soil organic matter, and soil C:N ratio in a series of experimental ponds manipulated with hydroperiod fluctuation and vegetation control using prescribed burns. Preliminary results show that frequently changing hydrologic conditions limit microbial biomass compared to more stable flooded or dry conditions. Our goal is to develop a framework to better understand the response of southeastern coastal plain wetlands to predicted climate change scenarios.

Checo Colon-Gaud (Co-Presenter/Co-Author), Georgia Southern University, jccolongaud@georgiasouthern.edu;


Angela Shaffer (Primary Presenter/Author,Co-Presenter/Co-Author), Georgia Southern University, as17251@georgiasouthern.edu;


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

EXPERIMENTAL NUTRIENT ENRICHMENT STIMULATES MULTIPLE TROPHIC LEVELS THROUGH ALGAL AND DETRITAL FOOD WEB PATHWAYS: A GLOBAL META-ANALYSIS FROM STREAMS AND RIVERS Anthropogenic increases in dissolved nitrogen (N) and phosphorus (P) strongly influence river and stream ecosystems. Quantifying biological responses to elevated nutrient concentrations is a research priority for basic and applied scientists, but there has been no comprehensive assessment of nutrient enrichment effects across lotic ecosystems. We conducted a global meta-analysis of published studies that experimentally increased concentrations of N or P in streams and rivers to examine how enrichment alters rate and state variables at multiple trophic levels. Our synthesis included 184 studies, 880 experiments, and 3500 biotic responses to nutrient enrichment. We documented widespread increases in biomass (+43.2 ± 2.0%) and production (+32.2 ± 2.9%) across all trophic levels (microbial heterotroph, primary producer, primary and secondary consumers, integrated ecosystem), with no significant differences among trophic levels. Responses to nutrient enrichment were moderated by water temperature, background concentrations of inorganic N and P, and light availability. Our meta-analysis revealed critical knowledge gaps including uncertainty in long-term consumer and whole-stream responses, due to the brief duration of most experiments. Overall, multiple food web pathways and trophic levels in lotic ecosystems are fundamentally altered by increased concentrations of N and P.

Marcelo Ardon (Co-Presenter/Co-Author), North Carolina State University, mlardons@ncsu.edu;


Lydia Zeglin (Primary Presenter/Author), Kansas State University, lzeglin@ksu.edu;


Ryan Utz (Co-Presenter/Co-Author), Chatham University, rutz@chatham.edu;


Scott Cooper (Co-Presenter/Co-Author), University of California Santa Barbara, scott.cooper@lifesci.ucsb.edu;


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


Rebecca Bixby (Co-Presenter/Co-Author), University of New Mexico, bbixby@unm.edu;


Ayesha Burdett (Co-Presenter/Co-Author), River Bend Ecology, Australia, Ayesha.Burdett@gmail.com ;


Jennifer Follstad Shah (Co-Presenter/Co-Author), University of Utah, jennifer.shah@envst.utah.edu;


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


Tamara Harms (Co-Presenter/Co-Author), University of California Riverside, tharms@ucr.edu;


Laura Johnson (Co-Presenter/Co-Author), Heidelberg University, ljohnson@heidelberg.edu;


Sherri Johnson (Co-Presenter/Co-Author), U.S. Forest Service, Pacific Northwest Research Station, sherrijohnson@fs.fed.us;


Jeremy B. Jones (Co-Presenter/Co-Author), University of Alaska Fairbanks, jbjonesjr@alaska.edu;


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.

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


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


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


David Van Horn (Co-Presenter/Co-Author), University of New Mexico, vanhorn@unm.edu ;


Amelia Ward (Co-Presenter/Co-Author), University of Alabama, award@ua.edu;


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