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SFS Annual Meeting

Monday, May 20, 2019
14:00 - 15:30

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14:00 - 14:15: / 151 G GOING WITH THE FLOW: SPATIAL AND TEMPORAL TRENDS IN STREAM MICROBIAL COMMUNITY STRUCTURE AND FUNCTION

5/20/2019  |   14:00 - 14:15   |  151 DEF

GOING WITH THE FLOW: SPATIAL AND TEMPORAL TRENDS IN STREAM MICROBIAL COMMUNITY STRUCTURE AND FUNCTION Microbes play key roles in shaping stream nutrient cycles and food webs. Similar to the macrobiota, stream microbial communities are shaped by both geomorphology and ecological interactions. However, how these processes interact to drive community changes over space and time remains poorly understood. We have conducted a five-year study of microbial community composition across the Upper Oconee Watershed near Athens, GA. We have found strong, replicable longitudinal trends in microbial community composition across the watershed, with alpha and beta diversity both decreasing with downstream movement through the stream network. This decrease in diversity is accompanied by consistent enrichment of a small subset of microbial taxa, with the same microbes being enriched across large stream networks and over long periods of time. The end result of these processes are highly diverse and variable upstream microbial communities, and progressively greater temporal and spatial stability in community composition as you move downstream. Studies of stream microbial metagenomes show that these taxonomic diversity trends are associated with downstream decreases in microbial metabolic diversity, suggesting that position within the River Continuum plays a key role in shaping microbial community structure and function.

Elizabeth Ottesen (Primary Presenter/Author), University of Georgia, ottesen@uga.edu;


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14:15 - 14:30: / 151 G RIPARIAN DEFOLIATION BY THE INVASIVE GREEN ALDER SAWFLY ALTERS TERRESTRIAL PREY SUBSIDIES TO SALMON STREAMS

5/20/2019  |   14:15 - 14:30   |  151 G

RIPARIAN DEFOLIATION BY THE INVASIVE GREEN ALDER SAWFLY ALTERS TERRESTRIAL PREY SUBSIDIES TO SALMON STREAMS The green alder sawfly (Monsoma pulveratum) is an invasive wasp whose larvae are defoliating riparian thin-leaf alder (Alnus tenuifolia) stands across southcentral Alaska. To test the hypothesis that riparian defoliation by this invasive sawfly negatively affects the flow of terrestrial prey resources to stream fishes, we sampled terrestrial invertebrates on riparian alder foliage, their subsidies to streams, and their consumption by juvenile coho salmon (Oncorhynchus kisutch). Invasive sawflies altered the composition of terrestrial invertebrates on riparian alder foliage and as terrestrial prey subsidies to streams. Community analyses reinforced these findings revealing that invasive sawflies shifted the community structure of terrestrial invertebrates between seasons and levels of energy flow (riparian foliage, streams, and fish). Invasive sawfly biomass peaked mid-summer, altering the timing and magnitude of terrestrial prey subsidies to streams. Juvenile coho salmon consumed invasive sawflies when most abundant, but relied more on other prey types selecting against sawflies relative to their availability. Although we did not find effects of invasive sawflies extending to juvenile coho salmon in this study, these results could change as the distribution of invasive sawflies expands or as defoliation intensifies.

David Roon (Primary Presenter/Author), Oregon State University, david.roon@oregonstate.edu;


Mark Wipfli (Co-Presenter/Co-Author), University of Alaska Fairbanks, mwipfli@alaska.edu;


Jim Kruse (Co-Presenter/Co-Author), US Forest Service, jkruse@fs.fed.us;


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14:30 - 14:45: / 151 G ENHANCED CARBON METABOLISM DOWNSTREAM OF A STREAM CONFLUENCE MIXING ZONE

5/20/2019  |   14:30 - 14:45   |  151 G

ENHANCED CARBON METABOLISM DOWNSTREAM OF A STREAM CONFLUENCE MIXING ZONE Stream confluences are ubiquitous features in freshwater networks and are known for distinct hydrogeomorphic characteristics relative to upstream tributaries and downstream reaches. However, the role of confluences as control points, locations that disproportionately influence ecosystem function (e.g., carbon metabolism, nutrient uptake), is still unknown. We might expect enhanced biological processes at confluences due to the delivery and mixing of carbon and nutrients. To test the potential influence of confluence mixing zones on dissolved organic carbon (DOC) removal in stream networks, we estimated DOC uptake using pulse injections of roasted barley leachate (standardized DOC source) and NaCl in two tributary reaches and downstream of their confluence. DOC uptake velocity (vf-DOC) in each tributary was 0.843 and 0.378 mm/min. vf-DOC downstream (0.94 mm/min) was higher than vf-DOC predicted from a mixing model of upstream vf-DOC and proportional flow contributions of tributaries (0.75 mm/min). This discrepancy in measured and predicted vf-DOC is also supported by bioassay experiments which found increased DOC uptake within the confluence mixing zone.. These results suggest that DOC uptake downstream of confluences cannot be estimated from tributary DOC uptake alone. Confluences may play a distinct role in carbon cycling.

Stephen Plont (Primary Presenter/Author), Virginia Tech, plontste@vt.edu;


Caitlin Miller (Co-Presenter/Co-Author), Virginia Tech, millca@vt.edu;


Erin Hotchkiss (Co-Presenter/Co-Author), Virginia Tech, ehotchkiss@vt.edu;


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14:45 - 15:00: / 151 G VARIATION OF FUNCTIONAL REDUNDANCY BETWEEN FUNCTIONAL PROCESS ZONES IN WESTERN NORTH AMERICAN STREAMS

5/20/2019  |   14:45 - 15:00   |  151 G

VARIATION OF FUNCTIONAL REDUNDANCY BETWEEN FUNCTIONAL PROCESS ZONES IN WESTERN NORTH AMERICAN STREAMS Functional process zones are distinct hydrogeomorphic districts useful for explaining ecosystem function within the Riverine Ecosystem Synthesis. FPZs may be used to link ecosystem function across different scales in Macrosystem ecology. For example, macroinvertebrate functional traits should vary predictably across similar FPZs between ecoregions. Functional redundancy links taxonomic diversity to functional traits and is informative in studying resiliency. We hypothesized that FR would vary between low energy and high energy FPZs at different elevations. Data from the US EPA National River and Stream Assessment were analyzed for 103 western North American sites. Relatively undisturbed sites were selected for study from FPZs identified based on elevation, channel morphology, and stream velocity. Discriminant analysis was used to confirm categorization of sites into four FPZs. FR for three functional groups representing 18 traits were analyzed. FR was lowest in the low elevation, low energy sites and highest in the high elevation, low energy sites. On average FR varied significantly between the FPZs (ANOVA, F=6.14, p< 0.00). Our results indicate that the FPZs identified were discrete in terms of FR across large regions in western North American streams.

Barbara Hayford (Primary Presenter/Author), University of Montana, bhayford@gmail.com;


Kaitlyn Dougherty (Co-Presenter/Co-Author), University of South Dakota, Kaitlyn.Dougherty@coyotes.usd.edu;


Alain Maasri (Co-Presenter/Co-Author), The Academy of Natural Sciences of Drexel University, alainmaasri@gmail.com;


Bolortsetseg Erdenee (Co-Presenter/Co-Author), The Academy of Natural Sciences of Drexel University, erdenee.bolortsetseg@gmail.com;


Jon Gelhaus (Co-Presenter/Co-Author), The Academy of Natural Sciences of Drexel University, gelhaus@gmail.com;


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15:00 - 15:15: / 151 G ORGANIC MATTER IN NESTED CATCHMENTS: DECREASING VARIABILITY WITH INCREASING STREAM ORDER

5/20/2019  |   15:00 - 15:15   |  151 G

ORGANIC MATTER IN NESTED CATCHMENTS: DECREASING VARIABILITY WITH INCREASING STREAM ORDER As an expansion to the framework provided by the River Continuum Concept, Creed et al. 2015 proposed rivers behave as a “chemostat” with organic matter variability decreasing with increasing stream order. Long-term data collected as part of the Boulder Creek Critical Zone Observatory was used to test these concepts. Samples were collected on a weekly basis for 4+ years from both the Boulder Creek Watershed and a smaller subcatchment within the watershed. Samples were analyzed for base cations, anions and water isotopes as well as the DOC concentration. The DOM chemistry was also assessed with UV-Vis and fluorescence spectroscopy. The span of data included both wet and dry years to assess behavior across a range of flow conditions as well as seasonal cycles. Boulder Creek demonstrates a classic snow-dominated hydrology, with peaks in flow in late spring and a DOC peak immediately before peak discharge. The subcatchment had a much flashier hydrology than the larger watershed, with both higher overall DOC concentration and greater variability in both DOC concentration and DOM chemistry. The corresponding hydrochemical data suggests that hydrologic flowpaths significantly control the DOM chemistry in the subcatchment.

Rachel Gabor (Primary Presenter/Author), The Ohio State University, gabor.40@osu.edu;


Diane McKnight (Co-Presenter/Co-Author), University of Colorado, diane.mcknight@colorado.edu;


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