SFS Annual Meeting

5/21/2019  |   11:00 - 11:15   |  251 DE

CONSEQUENCES OF UNPREDICTABLE RIVER FLOW REGIMES FOR LINKED ORGANISMAL-ECOSYSTEM PHENOLOGY IN THE ANTHROPOCENE Details of linked organismal-ecosystem phenology associated with the unpredictable flow regimes of New Zealand rivers can shed light on potential influences of climate extremes. Unpredictable flooding and non-seasonal organic matter inputs have led to trophic dynamics most unlike those of continental systems. Trophic generalists are pervasive, and macroinvertebrate life histories are poorly synchronized and involve multiple overlapping cohorts. The unpredictability likely works to ameliorate life-history trade-offs, promoting generalist traits and increasing niche width. However, extreme events are now exceeding the capacity of even extremophiles (e.g. mudfish) to adapt, and are associated with extirpation where dispersal is insufficient. Unpredictable flows, both low and high, also modulate food-web characteristics by controlling energy availability. For example, the occurrence of runaway primary production linked to a trophic cascade driven by non-native trout is most often associated with intermediate levels of flooding Such nonlinearities associated with a dynamic hydroclimatic regime make the effects of the higher magnitude erratic events predicted under climate warming for New Zealand difficult to forecast. However, linking metabolic regimes with existing flow-ecology knowledge from regimes like New Zealand’s has the potential to improve predictability of river ecosystems under global change.

Angus McIntosh (Primary Presenter/Author), University of Canterbury, angus.mcintosh@canterbury.ac.nz;


Jonathan Tonkin (Co-Presenter/Co-Author), University of Canterbury, jonathan.tonkin@canterbury.ac.nz;


Mark Galatowitsch (Co-Presenter/Co-Author), Centre College, mark.galatowitsch@centre.edu;


Helen Warburton (Co-Presenter/Co-Author), University of Canterbury, helen.warburton@canterbury.ac.nz;


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5/21/2019  |   11:15 - 11:30   |  251 DE

HOW DO YOU MEASURE A YEAR IN THE LIFE? EXAMINING ECOSYSTEM-WIDE RESPONSES TO ANNUAL SENESCENCE OF INVASIVE HYDRILLA IN UPLAND STREAMS OF THE CUMBERLAND PLATEAU Aquatic macrophytes are essential to the structure and function of freshwater ecosystems. Macrophytes with annual growth influence nutrient availability in the water between periods of growth when they are nutrient sinks and senescence when they are nutrient sources. This natural process can have profound effects on native communities where a non-native macrophyte has invaded and successfully colonized, as no evolutionary relationship exists between a native community and its exotic invader. The invasion of monoecious hydrilla (Hydrilla verticillata), an exotic aquatic macrophyte that smothers streambeds with profuse growth, was discovered in the Emory River Watershed of eastern Tennessee in August 2007. Monoecious hydrilla experiences annual growth characterized by winter senescence of shoots, giving it the potential to alter algal and associated invertebrate communities in response to nutrient and detritus influx. This study examines the effects of growing and senescent seasons on dissolved nutrients, algal colonization, and macroinvertebrate communities. Higher nutrient levels, higher periphyton biomass, and a shift in invertebrate functional feeding groups are predicted for periods of senescence relative to periods of growth. Understanding the temporal effects of hydrilla is necessary for making efficient and low-impact decisions regarding management endeavors.

Sandra Bojic (Primary Presenter/Author), Austin Peay State University, sbojic@my.apsu.edu;


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5/21/2019  |   11:30 - 11:45   |  251 DE

INFLUENCE OF STREAM METABOLISM AND FLOW VARIABILITY ON FISH TROPHIC NICHE IN DESERT STREAMS Flood and drought events have well documented effects on population dynamics, community composition, and many ecosystem processes. What remains less clear are the mechanisms relating streamflow to temporal variations in resource availability and the trophic dynamics of consumers. For example, floods may remove primary producers from the streambed, forcing consumers to subsist on allochthonous food sources. Alternatively, instream GPP may increase rapidly following a flood while stores of benthic detritus recover slowly, increasing consumer reliance on aquatic primary production. We collected seasonal measurements of stream metabolism and fish communities at sites along a gradient of streamflow variability in Arizona. Temporal changes in fish trophic niche were evaluated using stable isotope analysis. Across sites and seasons, food chain length decreased with increasing magnitude of antecedent high and low flow events (flow anomalies). Supporting the hypothesis that disturbances shorten food chains, the trophic position of an omnivorous fish (Agosia chrysogaster) distributed across several sites also decreased with greater flow anomaly magnitude. Quantifying these relationships will help elucidate the contributions of flow and metabolic regimes to spatial and temporal variation in stream food web structure.

Ethan Baruch (Primary Presenter/Author), Arizona State University, ebaruch@asu.edu;


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


Albert Ruhi (Co-Presenter/Co-Author), Department of Environmental Science, Policy, and Management, University of California, Berkeley, albert.ruhi@berkeley.edu;


Mengdi Lu (Co-Presenter/Co-Author), Arizona State University, Mengdi.Lu@asu.edu;


John Sabo (Co-Presenter/Co-Author), Arizona State University, John.L.Sabo@asu.edu;


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5/21/2019  |   11:45 - 12:00   |  251 DE

INTRASPECIFIC VARIABILITY AND THE EFFECT OF AN INVASIVE SPECIES ON THE PHENOLOGY OF ECOSYSTEM FUNCTIONING Biological invasions are a key component of global changes and, by creating new biotic interactions within invaded ecosystems, invasive species can induce strong changes on food web structure and ecosystem functioning. To date, however, our understanding of their effects on the phenology of ecosystem processes is limited as most investigations have focused on climate warming. Using a conjunction of field, experimental and modelling approaches and invasive crayfish as model organisms, we demonstrated that i) invasive species can have profound effect on the phenology of a key ecosystem function (namely organic matter decomposition) by accelerating the rate of carbon recycling and shortening the availability of organic detritus in ecosystems and that ii) phenotypic variability, irrespective of its natural and human-induced determinants, can strongly modulate the effects of invasive crayfish on leaf litter decomposition. These results highlight the role of invasive species on ecosystem phenology with their effects depending on individual phenotypes and not just on their abundance, and the need to understand how they interact with the phenological effects of climate warming.

Antoine Lecerf (Co-Presenter/Co-Author), EcoLab, Université de Toulouse, CNRS, France, antoine.lecerf@univ-tlse3.fr;


Maria Alp (Co-Presenter/Co-Author), IRSTEA, France, maria.alp@irstea.fr;


Mathieu Buoro (Co-Presenter/Co-Author), INRA, France, mathieu.buoro@inra.fr;


Charlotte Evangelista (Co-Presenter/Co-Author), University of Oslo, Norway, charlotte.evangelista0@gmail.com;


Allan Raffard (Co-Presenter/Co-Author), CNRS, France, allanraffard@outlook.com;


Libor Zavorka (Co-Presenter/Co-Author), Toulouse Univeristy, France, Libor.Zavorka@glasgow.ac.uk;


Julien Cucherousset (Primary Presenter/Author), CNRS, Toulouse University, Dept EDB, France, julien.cucherousset@univ-tlse3.fr;


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5/21/2019  |   12:00 - 12:15   |  251 DE

IS FRESHWATER MIGRATION A MECHANISM TO AVOID ENERGETIC LIMITATION IN AMAZONIAN FISHES? Fish migration is thought to play a key role in the functioning of freshwater ecosystems. Migration comprises a complex spatiotemporal variation in the fish abundance and distribution across seasons or life stages. Allowing fishes to access different conditions in potentially distant areas during their life cycle for reproduction, feeding, or finding refuge. Nevertheless, compared with other forms of fish migration, potamodromy, which occur entirely within freshwaters, has received less attention in the literature. In tropical freshwater ecosystems like the Amazon Basin, potamodromy is relatively common and usually involves large-bodied and fisheries-important species. Most existing research on potamodromy has focused on environmental cues that trigger migration, such as hydrological or thermal regimes. But the possible influence of energetic regimes and resource availability on the migratory behavior of tropical fishes has received limited attention. We conducted a literature review to examine the state of the knowledge of migratory behaviors of Amazonian freshwater fishes, understanding their ecological motivations whether these are linked to thermal, hydrologic, or energetic regimes. As a result, we compiled a species checklist summarizing their migratory behaviors and a spatial database of geographical records of fish migration across the Amazon.

Guido A Herrera-R (Primary Presenter/Author), University of Tennessee, guidohero@hotmail.com;


Elizabeth P Anderson (Co-Presenter/Co-Author), Florida International University, epanders@fiu.edu;


Aldo Farah (Co-Presenter/Co-Author), Florida International University, farahaldo@gmail.com;


Sandra Correa (Co-Presenter/Co-Author), Missisipi State University, sbc257@msstate.edu;


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5/21/2019  |   12:15 - 12:30   |  251 DE

NOVEL INSIGHTS INTO ECOSYSTEM DRIVERS FROM ANALYSIS OF METABOLIC REGIMES Reservoirs can act as hotspots of biogeochemical activity, modifying downriver nutrient regimes and potentially impacting downriver metabolic regimes and aquatic ecosystems. Here, we show that seasonal and inter-annual variation in phosphorus loading from Lake Powell Reservoir is an important control on Colorado River food webs downriver from Glen Canyon Dam. Variation in phosphorous loading and light are equally important in explaining variation in gross primary production 120 river km below the dam. Invertebrate drift and native fish condition have tracked long-term variation in GPP and a depressed carbon supply likely led to a ~50% decline in the spawning rate of endangered humpback chub in one year. In the tailwater of the dam, invertebrate drift and rainbow trout recruitment also track interannual and seasonal variation in phosphorous loading, however, links to the metabolic regime are not as clear. This discrepancy may result from the more complex aquatic vegetation community located near the dam, which includes rooted macrophytes. Our work highlights how studying metabolic regimes can improve understanding of ecosystem drivers, identifying environmental controls in regulated rivers beyond the usual suspects of temperature, hydrology, and sediment regimes.

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


Bridget Deemer (Co-Presenter/Co-Author), U.S. Geological Survey, Southwest Biological Science Center, bdeemer@usgs.gov;


Michael Yard (Co-Presenter/Co-Author), USGS, myard@usgs.gov;


Ted Kennedy (Co-Presenter/Co-Author), USGS Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, tkennedy@usgs.gov;


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


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