SFS Annual Meeting

6/04/2024  |   10:30 - 10:45   |  Independence Ballroom D

Coupling Concentration- and Process-Discharge Analysis Informs Arctic Stream Metabolic Response to River Discharge. Flow intensity strongly dictates when and how stream networks act as transporters or transformers of solutes, altering the biogeochemical parameters that control stream ecosystem metabolism (e.g., residence time, turbidity, temperature, etc.). With Arctic ecosystems experiencing dramatic hydrologic intensification due to rapid climate change, it remains unclear how changes in flow duration and intensity will impact instream ecosystem processes and the transport of solutes from land to surface waters. To address this question, we measured high-frequency hydrochemical dynamics at the outlets of three catchments in Northern Alaska that represent common Arctic landscape types: tundra, lake-influenced tundra, and high-gradient alpine. We deployed a suite of in-situ sensors to capture continuous dissolved oxygen, pH, conductivity, turbidity, dissolved organic carbon (DOC), and nitrate (NO3-) concentrations at 15-minute intervals throughout the flow seasons (June-September) in 2021-2023. Prior work in these watersheds has demonstrated strong landscape controls on DOC and NO3- concentration-discharge (C-Q) behaviors at the event-scale. Here, we assessed ecosystem process-discharge (P-Q) relationships by measuring continuous whole-stream metabolism (as GPP and ER) throughout the flow season. Using changepoint analysis, we identified distinct discharge thresholds at which ecosystem metabolism, solute concentrations, and other physicochemical drivers significantly change with increasing flows within each of our catchments. Understanding P-Q thresholds provides valuable information about the strength of biogeochemical controls on metabolism at different flows, and overall metabolic resilience to changing discharge, clarifying how stream ecosystems respond to physical and chemical change in the rapidly changing Arctic.

Abigail Rec (Primary Presenter/Author), University of Vermont, abigail.rec@uvm.edu;

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

Arial Shogren (Co-Presenter/Co-Author), University of Alabama, ashogren@ua.edu;

Jay Zarnetske (Co-Presenter/Co-Author), Department of Earth and Environmental Sciences, Michigan State University, jpz@msu.edu;

Amelia Grose (Co-Presenter/Co-Author), Michigan State University, groseame@msu.edu;

Jansen Nipko (Co-Presenter/Co-Author), Brigham Young University, jbnipko@gmail.com;

Benjamin Abbott (Co-Presenter/Co-Author), Brigham Young University, Department of Plant and Wildlife Sciences, benabbott@byu.edu;

Jonathan O'Donnell (Co-Presenter/Co-Author), National Park Service, jonathan_o'donnell@nps.gov;

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6/04/2024  |   10:45 - 11:00   |  Independence Ballroom D

ARCTIC STREAM CHEMISTRY REFLECTS THAWING SOIL AND INCREASING FLOWPATH DEPTHS Stream chemistry reflects hillslope processes including subsurface water flowpaths and can be used to trace these flowpaths in regions where soil chemistry varies at depth. This is particularly valuable in the Arctic, where thawed soil depth naturally increases throughout the thaw season (May-September), as well as over longer timescales due to climate change, exposing new pathways for water and solute transport. This may alter fluxes of reactive nutrients, including [N]itrogen, by allowing for more mineralization of abundant organic matter, increasing dissolved inorganic N (DIN) in surface water. To assess the impact of evolving flowpath depths on stream chemistry, we conducted twelve sampling events across three thaw seasons (2021-2023). For each event, we sampled 40-50 stream sites across four headwater catchments typical of distinct Arctic landscape types in northern Alaska. We analyzed geochemical tracers that change as a function of soil depth (e.g., Na+, Ca+, K+) in stream water throughout the thaw season to document changing flowpath depths. We also sampled soil water and thaw depth at some sites to compare to our geochemical results. Then, we examined stream DIN to look for evidence of increasing mineralization with increasing flowpath depths. We found shifts in geochemical tracer concentrations reflecting deeper thaw in all catchments as the thaw season progressed, but shift magnitudes varied by catchment. These geochemical indicators of increasing thaw were concurrent with increases of stream nitrate export in the late thaw season, supporting hypotheses that thawing soil may fundamentally change stream ecosystem conditions as the Arctic continues warming.

Amelia Grose (Primary Presenter/Author), Michigan State University, groseame@msu.edu ;

Jay Zarnetske (Co-Presenter/Co-Author), Department of Earth and Environmental Sciences, Michigan State University, jpz@msu.edu;

Arial Shogren (Co-Presenter/Co-Author), University of Alabama, ashogren@ua.edu;

Abigail Rec (Co-Presenter/Co-Author), University of Vermont, abigail.rec@uvm.edu;

Valeria Prieto Hurtado (Co-Presenter/Co-Author), Brigham Young University, vprietohurtado@gmail.com;

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

Benjamin Abbott (Co-Presenter/Co-Author), Brigham Young University, Department of Plant and Wildlife Sciences, benabbott@byu.edu;

Jonathan O'Donnell (Co-Presenter/Co-Author), National Park Service, jonathan_o'donnell@nps.gov;

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6/04/2024  |   11:00 - 11:15   |  Independence Ballroom D

Longitudinal patterns in carbon cycling along a stream continuum draining a heterogeneous landscape Landscape alterations can impact hydrology and biogeochemistry in streams, influencing ecosystem processes such as ecosystem metabolism (i.e., gross primary production (GPP) and ecosystem respiration (ER)). However, we rarely characterize metabolism along a single stream as it moves through engineered structures and land cover changes. Here we asked: how do landscape differences along an aquatic continuum influence stream metabolism? High-frequency sensors were deployed along 3 sites of Stroubles Creek in Blacksburg, VA (i.e., buried upstream, urban-agricultural, and forested sites) to record stage, dissolved oxygen (DO), fDOM, and water temperature for ~one year. We used streamMetabolizer in R to estimate daily GPP and ER. GPP estimates were the lowest at the buried upstream site (0 to 4.3 gO2 m-2d-1), where ER had the highest range of values (-1.03 to -26.22 gO2 m-2d-1). GPP and ER at our urban-agricultural site ranged from 0 to 9.18, and -0.13 to -15.27 (gO2 m-2d-1), respectively. Our forested site had the highest GPP range (0 to 13.97 gO2 m2d-1);ER ranged from -0.23 to -23.77 gO2 m2d-1. Metabolism was most constrained over the study period at the buried upstream site, followed by the urban-agricultural site, with the forested downstream site having the most dynamic metabolic regime. Using site-specific stage-discharge relationships, we will address how flow conditions influence the metabolism and downstream transport of organic matter at each of our three sites. Understanding how flow influences metabolism will aid in informing overall freshwater ecosystem function and susceptibility to environmental and land use changes.

Katherine Pérez Rivera (Primary Presenter/Author), Virginia Tech, kperezrivera@vt.edu;

Stephen Plont (Co-Presenter/Co-Author), The University of Alabama, plontste@gmail.com;

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

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6/04/2024  |   11:15 - 11:30   |  Independence Ballroom D

Effect of storm events on the metabolic activity in a Mediterranean headwater stream Hydrological disturbances following storm events influence the structure and functioning of headwater streams. However, understanding of how these disturbances impact critical processes such as stream metabolism is challenging. We assess the effect of hydrological disturbances on the resistance and resilience of stream gross primary production (GPP) and ecosystem respiration (ER) in a net heterotrophic Mediterranean stream (period 2018-2023). We expect stream metabolism to show low resistance because GPP and ER will be either enhanced by inputs of limited resources (small hydrological disturbances) or hindered by biofilm damage (large hydrological disturbances). We also predict resilience to decrease with the size of the hydrological disturbance. We calculated metabolic rates during 53 individual hydrological events of different magnitude (discharge from 1.3 to 3770 L s-1), though only 23 events were successfully resolved (all <100 L s-1). Mean GPP and ER equalled 0.4 ± 0.1 and 5.4 ± 0.3 gO2m-2d-1. The two processes showed low resistance to hydrological disturbance, with magnitudes increasing between 2- and 3-fold for 62% of the events. Changes in GPP were unrelated to the magnitude of the hydrological event, while a positive correlation was found for ER (R2 = 0.5). Recovery times were not linked to the size of the event, but ER recovered more slowly than GPP, suggesting a prolonged effect of limited resource inputs on ER. Our findings support the idea that stream metabolism responds to intermediate disturbances and highlight how changes in hydrological regimes could impact stream functioning and its role on global biogeochemical cycles.

Carolina Jativa (Primary Presenter/Author), Integrated Freshwater Ecology Group, Center for Advanced Studies of Blanes (CEAB-CSIC), Blanes, Girona, Spain., carito.jativa@gmail.com;

Emma Lannergård (Co-Presenter/Co-Author), Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden, emma.lannergard@slu.se;

Anna Lupon (Co-Presenter/Co-Author), Center for Advanced Studies of Blanes (CEAB-CSIC), Spain, alupon@ceab.csic.es;

Xavi Peñarroya (Co-Presenter/Co-Author), Integrated Freshwater Ecology Group, Center for Advanced Studies of Blanes (CEAB-CSIC), Blanes, Girona, Spain., xp.galceran@gmail.com;

José Ledesma (Co-Presenter/Co-Author), Department of Hydrogeology, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany, jose.ledesma@ufz.de;

Gerard Rocher-Ros (Co-Presenter/Co-Author), Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden. Integrative Freshwater Ecology Group, Centre for Advanced Studies of Blanes (CEAB-CSIC), Blanes, Spain, g.rocher.ros@gmail.com;

Susana Bernal (Co-Presenter/Co-Author), Integrated Freshwater Ecology Group, Center for Advanced Studies of Blanes (CEAB-CSIC), Blanes, Girona, Spain., sbernal@ceab.csic.es;

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6/04/2024  |   11:30 - 11:45   |  Independence Ballroom D

CHARACTERIZING RIVER METABOLISM AND RESOURCE AVAILABILITY ACROSS A GRADIENT OF ALTERATION IN DESERT RIVERS TO INFORM NATIVE FISH CONSERVATION River metabolism and aquatic communities are driven by hydrological and physiochemical regimes in rivers, but these regimes are often altered due to a suite of stressors including anthropogenic water demand and climate change-driven drought. Despite widespread river alteration, the effects of flow regime alteration on bottom-up processes and aquatic food webs remain understudied. To better understand the linkages between river alteration, metabolism, and food webs, we deployed oxygen and temperature sondes and measured benthic algae and macroinvertebrate standing stock in seven tributaries of the upper Colorado River Basin with varying degrees of flow alteration. In 2023, we maintained sondes, measured benthic Chlorophyll-a, and collected benthic macroinvertebrates monthly from July to December during baseflow conditions. Whereas data and sample processing are ongoing, preliminary results for benthic algae suggest a negative correlation (r = -0.79; p = 0.023) between Chlorophyll-a and flow regime alteration, represented as the percent difference between 21st and 20th-century spring flows. We also expect a negative relationship between flow regime alteration and macroinvertebrate biomass and river metabolism. To date, much research on limiting factors for higher trophic levels, such as fishes, has focused on habitat alteration and invasive species introductions, largely ignoring bottom-up effects. Improving our understanding of linkages between river alteration, metabolic regimes, and dynamics of higher trophic levels will enhance our ability to predict how riverine ecosystem structure and function might change in the future.

Chloe Lyles (Primary Presenter/Author), U.S. Geological Survey, Utah Cooperative Fish and Wildlife Research Unit, Utah State University, chloe.lyles@usu.edu;

Phaedra Budy (Co-Presenter/Co-Author), U.S. Geological Survey, Utah Cooperative Fish and Wildlife Research Unit, Utah State University, phaedra.budy@usu.edu;

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

Casey Pennock (Co-Presenter/Co-Author), The Ohio State University, pennock.17@osu.edu;

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6/04/2024  |   11:45 - 12:00   |  Independence Ballroom D

BIOMASS, THERMAL TOLERANCE, AND MOVEMENT BEHAVIOR MEDIATE FRESHWATER MUSSELS’ ZOOGEOCHEMICAL IMPACTS ON BENTHIC METABOLISM Animals can have strong impacts on biogeochemical processes such as carbon cycling. In streams, carbon transport and mineralization in streams are driven by ecosystem metabolism—the balance of ecosystem respiration (ER) and gross primary production (GPP). Animals can alter stream metabolism, and thereby carbon cycling, through mechanisms tied to their ecophysiological and behavioral traits. Freshwater mussels occur in dense aggregations and can affect stream metabolism, but these effects depend on interspecific variation in traits. To test how mussel traits mediate their influence on stream metabolism, we conducted a field experiment using self-contained chambers designed to measure benthic metabolic rates. Each chamber contained one of four monospecific mussel treatments with contrasting thermal tolerance traits. We quantified ER and GPP in each chamber during summer and fall incubations. We also tracked individual mussels’ movement patterns during the summer incubations to test for bioturbation effects. We found that temperature and mussel biomass explained more variation in metabolism than species identity. However, thermally sensitive treatments had higher ER than thermally tolerant treatments in the summer. Mussels’ vertical movement frequency and depth varied by species and thermal tolerance, but horizontal movement did not. Burial depth and vertical movement frequency were greater in thermally sensitive species than thermally tolerant species. Greater movement appeared to increase background ER via bioturbation. Our findings indicate that mussels’ ecophysiological and behavioral traits constrain their impacts on benthic metabolism. An improved understanding of animal-driven effects on stream metabolism may improve our ability to anticipate and predict changes in freshwater carbon cycling.

Jonathan Lopez (Primary Presenter/Author), The University of Alabama, jwlopez@ua.edu;

Matthew Lodato (Co-Presenter/Co-Author), University of Alabama, mlodato@crimson.ua.edu;

Carla L. Atkinson (Co-Presenter/Co-Author), The University of Alabama, carla.l.atkinson@ua.edu;

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