Wednesday, May 25, 2016
15:30 - 17:00

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15:30 - 15:45: / 308 BENTHIC HABITAT SUSCEPTIBILITY TO PERTURBATIONS INFLUENCES URBAN STREAM METABOLISM

5/25/2016  |   15:30 - 15:45   |  308

BENTHIC HABITAT SUSCEPTIBILITY TO PERTURBATIONS INFLUENCES URBAN STREAM METABOLISM The relative importance of intensified hydrologic disturbance regimes in urban streams for metabolism is partially dependent on channel geomorphology since benthic habitats vary in their susceptibility to perturbation. We selected two groups of 3 urban streams in Durham and Raleigh, NC that each spanned a gradient in hydrologic flashiness, with one group having ‘unstable’ beds in the study reach and the other with ‘stable’ beds. Since November 2015, we have been measuring gross primary productivity (GPP). We expected that average GPP would be negatively correlated with hydrologic flashiness and lower overall in sites with unstable beds. Daily GPP ranged from 0.10 to 5.83 g O2m-2d-1 across all sites. Average GPP was not consistently lower in sites with unstable beds nor correlated with mean stormflow duration (inverse metric for flashiness). Temporal patterns of GPP were highly variable across the sites ranging from steady low rates (CV=0.15) to ‘boom-bust’ patterns with storms (CV=0.91). We expect that light is the primary driver of GPP, but bed stability plays an important role in determining the frequency and intensity of GPP reductions following spates.

Joanna Blaszczak (Primary Presenter/Author), Flathead Lake Biological Station, University of Montana, joanna.blaszczak@flbs.umt.edu;


Joseph Delesantro ( Co-Presenter/Co-Author), University of North Carolina - Chapel Hill, jmdelesantro@gmail.com;


Dean Urban ( Co-Presenter/Co-Author), Duke University, deanu@duke.edu;


Emily Bernhardt ( Co-Presenter/Co-Author), Duke University, ebernhar@duke.edu;


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15:45 - 16:00: / 308 BIOGEOCHEMICAL EVALUATION OF RESTORED URBAN STREAMS

5/25/2016  |   15:45 - 16:00   |  308

BIOGEOCHEMICAL EVALUATION OF RESTORED URBAN STREAMS Urban infrastructure changes pathways connecting storm waters to streams, altering the function and structure of riparian and stream ecosystems, degrading channels and increasing downstream contaminant export. Geomorphic stream restoration, focused on channel stabilization, is commonly implemented as a response strategy. However, considerable uncertainty exists about its effectiveness on nutrient fluxes, nutrient retention, and hyporheic exchange. Furthermore, seasonal and interannual variation associated with restoration warrant further study. We studied metabolism and nitrogen dynamics of six urban reaches in the greater Baltimore area, representing a gradient of hyporheic connectivity, restoration age, and canopy cover. We use seasonal nitrate additions, coupled with continuous discharge and stream metabolism, to establish relationships between nutrient retention and metabolism, and to quantify the effectiveness of stream restoration on annual nutrient export. In addition, synoptic sampling of nutrients in the streams further quantifies temporal variability in ecosystem function across reaches. Preliminary results indicate high variability in nitrate uptake length across reaches and variable net nitrate removal, suggesting that geomorphic restoration may increase nitrate retention. Further study will establish the biotic and abiotic drivers of change in nutrient retention.

Thomas Doody (Primary Presenter/Author), University of Maryland, College Park , tdoody@umd.edu;


Alexander Reisinger ( Co-Presenter/Co-Author), Cary Institute of Ecosystem Studies, reisingera@caryinstitute.org;


Emma Rosi ( Co-Presenter/Co-Author), Cary Institute of Ecosystem Studies, rosie@caryinstitute.org;


Sujay Kaushal ( Co-Presenter/Co-Author), University of Maryland, skaushal@umd.edu;


Peter Groffman ( Co-Presenter/Co-Author), City University of New York, Peter.Groffman@asrc.cuny.edu ;


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16:00 - 16:15: / 308 ECOSYSTEM METABOLISM RESPONSE TO URBAN DEVELOPMENT IN COASTAL CALIFORNIA STREAMS

5/25/2016  |   16:00 - 16:15   |  308

ECOSYSTEM METABOLISM RESPONSE TO URBAN DEVELOPMENT IN COASTAL CALIFORNIA STREAMS Around the world, urbanization is altering stream ecosystems, but the response of stream ecosystem metabolism remains ambiguous. Six similar but variably developed watersheds in coastal Santa Barbara, California provide an ideal setting to compare stream metabolism response to urbanization. From March to July, 2014, dissolved oxygen records were collected and used to estimate ecosystem rates of gross primary production (GPP) and community respiration (CR). Rates of GPP range from 0.06 to 6.11 g O2/ m2/d across streams, with site-average GPP in developed streams significantly higher than in undeveloped streams. Rates of CR range from 2.03 to 15.87 g O2/m2/ d and show no significant difference between developed and undeveloped site-averages. Complementary data analyses identify nitrate as a primary driver of GPP across sites, but reveal non-significant correlations between land cover and metabolism estimates. However, population and septic system counts do correlate significantly with metabolism estimates. These results indicate that stream metabolism is sensitive to nutrient pollution from urbanization, and suggest a need for incorporating more specific information about human activities on the landscape to improve our understanding of urban metabolism.

Heather Frazier (Primary Presenter/Author), University of California, Santa Barbara, heather.berry@geog.ucsb.edu;


John Melack ( Co-Presenter/Co-Author), University of California, Santa Barbara, CA, USA, melack@lifesci.ucsb.edu;


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16:15 - 16:30: / 308 LINKING URBANIZATION TO CHANGES IN RIPARIAN VEGETATION IN A MEDITERRANEAN CLIMATE: CONSEQUENCES FOR ECOSYSTEM FUNCTION IN HEADWATER STREAMS

5/25/2016  |   16:15 - 16:30   |  308

LINKING URBANIZATION TO CHANGES IN RIPARIAN VEGETATION IN A MEDITERRANEAN CLIMATE: CONSEQUENCES FOR ECOSYSTEM FUNCTION IN HEADWATER STREAMS Urbanization is generally associated with decreases in riparian forest area and drying of riparian zones due to stream channel incision. However, urbanization may produce different consequences in regions with Mediterranean climates, such as Sacramento, California. Many headwater streams in this area were historically intermittent and did not support dense woody vegetation; with urbanization, streams have not only incised, but have also become perennial due to runoff. We analyzed land use/land cover change in Sacramento’s 85-square-km Arcade Creek watershed. Since 1937, land use has shifted almost entirely from agriculture to urban, and forested area within 50 m of streams has increased 38 percent. Additionally, our survey of riparian vegetation at nearly 70 headwater stream reaches across the Sacramento area suggests that both channel incision and dry-season flow are important predictors of woody species composition, while exotic trees proliferate closer to the urban core. These changes in riparian forest area and species composition affect stream shading and litter inputs, potentially impacting in-stream nutrient cycling. Drought-related reductions in urban water use may cause further changes to these ecosystems if streams become intermittent again.

Joanna Solins (Primary Presenter/Author), University of California, Davis, jsolins@ucdavis.edu;


Mary Cadenasso ( Co-Presenter/Co-Author), University of California, Davis, mlcadenasso@ucdavis.edu;


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16:30 - 16:45: / 308 CHARACTERIZATION OF DISSOLVED ORGANIC MATTER SOURCES ALONG A MOUNTAIN TO URBAN GRADIENT OF LANDUSE

5/25/2016  |   16:30 - 16:45   |  308

CHARACTERIZATION OF DISSOLVED ORGANIC MATTER SOURCES ALONG A MOUNTAIN TO URBAN GRADIENT OF LANDUSE Dissolved organic matter (DOM) is the largest pool of carbon in aquatic ecosystems, and after of decades of study, remains a mysterious mixture of labile and non-labile compounds. We hypothesized anthropogenic changes in land use have increased the proportion of labile DOM in river ecosystems. We sampled DOM at 16 sites in autumn and summer in three Utah watersheds that encompass a range of land uses. Samples were analyzed for inorganic nutrient concentrations, dissolved organic carbon (DOC), nitrogen (DON), and several spectrofluorometric indices including the fluorescence index (FI). FI values ranged from 1.4 to 1.7 representing a range in DOM derived from both microbial and terrestrial sources. DOC concentrations were negatively correlated with the FI and positively correlated with phosphorus concentrations suggesting sites with high DOC concentrations have proportionally more recalcitrant DOM than labile DOM. Interestingly, DOC and DON were not significantly correlated indicating DOM inputs from multiple sources. This study can help identify sources of DOM and shed light on the complex interactions between inorganic nutrients and organic matter inputs in watersheds with varying land use.

Julie Kelso (Primary Presenter/Author), ORISE Environmental Protection Agency, julia.kelso@gmail.com;


Michelle Baker ( Co-Presenter/Co-Author), Utah State University, michelle.baker@usu.edu;


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16:45 - 17:00: / 308 DISSOLVED ORGANIC MATTER IN URBAN EPHEMERAL HEADWATERS

5/25/2016  |   16:45 - 17:00   |  308

DISSOLVED ORGANIC MATTER IN URBAN EPHEMERAL HEADWATERS Gutters and stormwater pipes are the engineered, ephemeral headwaters of urban stream networks. During baseflow conditions, these areas store and process organic matter (OM) which can then be quickly mobilized at stormflow. Within these headwater ecosystems, we hypothesize that rates and timing of organic matter input, processing, and export influence the amount and composition of OM within the network of the engineered urban headwaters, as well as OM delivered to perennial streams. To test these hypotheses, we measured litterfall, decomposition, and changes in OM load in 5 residential gutters and 5 catchbasins in Durham, NC. During storms, we collected samples from roofs, roads, streams, and stormwater infrastructure to determine DOM and inorganic nutrient concentrations. We also characterized DOM composition (using EEM-PARAFAC) in stormwater and compared the amount and composition of DOM among locations in the urban headwaters. Generally, DOC concentration and the contribution of PARAFAC components associated with microbial activity decreased from upstream (roofs, road) to downstream (stream) locations. Together, these data suggest that considerable processing of OM occurs in the engineered headwaters of urban stream networks.

Megan Fork (Primary Presenter/Author), Umeå University - Department of Ecology, Environment and Geoscience, megan.fork@gmail.com;


Joanna Blaszczak ( Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, joanna.blaszczak@flbs.umt.edu;


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


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