6/08/2017  |   09:00 - 09:15   |  302B

EXPLAINING TEMPORAL TRENDS AND SPATIAL PATTERNS IN SUMMER STREAM CHEMISTRY FOR SUBARCTIC WATERSHEDS The boreal forest of interior Alaska is undergoing unprecedented change in response to a rapidly warming climate, which has tremendous impacts for the regions aquatic ecosystems. However, it is difficult to know whether variability in stream chemistry over time reflects climate signals, hydrologic stochasticity, environmental conditions, or a combination all three. Here, we use dynamic factor analysis to evaluate similarities among temporal trends of solutes in five separate watersheds to understand how drivers representing climate, hydrology, and physiography influence biogeochemical signals. Daily concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and other solutes (NO3-, NH4+, Ca2+, K+, Mg2+, Na+) collected during the summer from 2002 - 2015 were used to calculate trends. In general, summer stream chemistry in these headwater streams differs among sites, suggesting that driving mechanisms vary by watershed for most solutes. However, watershed characteristics such as permafrost extent partially explained differences in DOC, DIC, and some base cations. These findings contribute to the current understanding of the effects of interannual variability in active layer depths and permafrost extent in subarctic watersheds.

Claire Ruffing (Primary Presenter/Author), University of British Columbia, ruffing.cathcart@ubc.ca;


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


Adrianne Smits ( Co-Presenter/Co-Author), University of California, Davis, asmits@ucdavis.edu;


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6/08/2017  |   09:15 - 09:30   |  302B

TEMPORAL TRENDS IN N, P, AND SILICA STOICHIOMETRY IN THE MISSISSIPPI RIVER BASIN SUGGEST INCREASINGLY FAVORABLE CONDITIONS FOR NON-SILICEOUS ALGAE AND CYANOBACTERIA Stoichiometric ratios of N, P, and dissolved silica (dSi) determine whether the response to nutrient loading is mainly by diatoms or by non-siliceous taxa, including cyanobacteria. The Indicator of Coastal Eutrophication Potential (ICEP), described previously by other researchers, predicts production by diatoms vs. non-siliceous taxa based on deviation from the Redfield ratio for diatoms under N-limited (N-ICEP) and P-limited (P-ICEP) conditions. I calculated N-ICEP and P-ICEP using USGS nutrient loads from 1980-2015 for the entirety of the Mississippi-Atchafalaya River basin, as well as four major sub-basins: the Ohio, Missouri, Upper Mississippi, and combined Arkansas-Red basins. N-ICEP for the mouth of the Mississippi River was positively correlated through time with both volume and area of the Gulf hypoxic zone, indicating that ICEP captures relevant ecological properties of the system. N-ICEP at the mouth was controlled largely by the Upper Mississippi, the most stoichiometrically imbalanced sub-basin. An auto-regressive integrated moving-average model showed increasing P-ICEP values through time, with N-ICEP moving in the opposite direction. N:P:dSi stoichiometry is changing throughout the Mississippi basin and the trend points towards increasingly favorable conditions for cyanobacteria in inland waters.

Todd V. Royer (Primary Presenter/Author), Indiana University Bloomington, troyer@iu.edu;


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6/08/2017  |   09:30 - 09:45   |  302B

CLIMATE DRIVERS OF VARIABILITY AND SYNCHRONY IN DISCHARGE AND NUTRIENT LOADS IN THE MISSISSIPPI BASIN Agriculture in the Mississippi Basin contributes to nutrient loading to the Gulf of Mexico. However, climatic fluctuations result in annual variability in nutrient loads to the Gulf. Climate phenomena such as El-Niño Southern Oscillation (ENSO) influence regional precipitation and temperature and may drive synchrony in streamflow, but climate-driven effects on solute export from the Mississippi Basin are poorly understood. Here, we investigate how large-scale climactic patterns (ENSO, North Atlantic Oscillation (NAO), Northern Hemisphere Land-Surface Air Temperature Anomaly (SAT)) influence N, P, and Si loads from four large Mississippi sub-basins: the Upper Mississippi, Ohio-Tennessee, Missouri, and Arkansas-Red. We fit multivariate autoregressive state-space models to USGS estimated solute loads from these four basins (1979 – 2014) to investigate how climate affects temporal and spatial variation in solute load dynamics. Discharge and solute loads in the Upper Mississippi and Missouri displayed synchronous dynamics ( delta AICc > 2 for all solutes), whereas the Ohio-Tennessee and Arkansas-Red were independent. Climate indices (ENSO, SAT, NAO) had significant effects on discharge and solute loads, and the magnitude and direction of these effects varied by solute and region.

Adrianne Smits (Primary Presenter/Author), University of California, Davis, asmits@ucdavis.edu;


Claire Ruffing ( Co-Presenter/Co-Author), University of British Columbia, ruffing.cathcart@ubc.ca;


Todd V. Royer ( Co-Presenter/Co-Author), Indiana University Bloomington, troyer@iu.edu;


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


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


Rebecca Bellmore ( Co-Presenter/Co-Author), Southeast Alaska Watershed Coalition, rebecca@sawcak.org;


Mark Scheuerell ( Co-Presenter/Co-Author), University of Washington , scheuerl@uw.edu;


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


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


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6/08/2017  |   09:45 - 10:00   |  302B

A BIG-DATA APPROACH TO UNDERSTANDING THE EFFECTS OF DROUGHT ON TOTAL DISSOLVED SOLIDS IN STREAMS AND RIVERS Total dissolved solids (measured as specific conductivity, SC) influences the distributions of aquatic organisms, but we can only estimate variation in space and time over limited extents. Reduced precipitation and increased temperatures increase SC, so landscape scales estimates of SC during droughts are needed at to identify location and amounts of SC increase. We related 11,961 SC observations made at 1,756 minimally impaired sites across the conterminous USA between 2001 and 2015 to watershed summaries of static (e.g., geology and soils) and dynamic (e.g., climate, vegetation, and evapotranspiration) environmental predictors using Random Forests. The resulting model explained 92% of the variation in the validation data, with a root mean squared error of 122 µS/cm. We then applied this model to predict monthly SC for every stream segment in the study area over the 15 years, allowing comparisons of SC between drought and non-drought conditions. These comparisons show that SC increases >125 µS/cm occur in some minimally affected streams during summer droughts, potentially leading to local extirpations of aquatic life. These are the authors views and do not necessarily represent views or policies of U.S. EPA.

John Olson (Primary Presenter/Author), Dept of Applied Environmental Science, California State University Monterey Bay, CA, USA, joolson@csumb.edu;


Lei Zheng ( Co-Presenter/Co-Author), previously with Tetra Tech, Inc., lei.zheng@hotmail.com;


Susan Cormier ( Co-Presenter/Co-Author), USEPA, Cormier, Susan ;


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6/08/2017  |   10:00 - 10:15   |  302B

LOSS OF MACROINVERTEBRATE TAXA AS A RESULT OF INCREASED SPECIFIC CONDUCTIVITY DURING DROUGHT Drought increases the risk of impairment associated with water quantity and quality. Intensive drought concentrates dissolved chemicals and reduces dilution of mineral inputs. One of the direct impacts of increased total dissolved solids (measured as specific conductivity, [SC]) is the extirpation of salt-intolerant aquatic life. We developed and used a model that estimates the proportion of extirpated genera based on background SC and a change in SC (Delta-Delta model). The loss of macroinvertebrate genera associated with increased SC as a result of drought was assessed using the 95th centile extirpation concentration (XC₉₅) approach released by USEPA in 2011. Using either the measured or geophysical modeled change in SC during a drought as the independent variable and the Delta-Delta model, we estimated the proportion of genera extirpated at various spatial and temporal scales. We therefore identified the streams that are most vulnerable to drought and the proportion of extirpation at a national scale. These are the authors views and do not necessarily represent the views or policies of USEPA.

Lei Zheng ( Co-Presenter/Co-Author), previously with Tetra Tech, Inc., lei.zheng@hotmail.com;


John Olson (Primary Presenter/Author, Co-Presenter/Co-Author), Dept of Applied Environmental Science, California State University Monterey Bay, CA, USA, joolson@csumb.edu;


Susan Cormier ( Co-Presenter/Co-Author), USEPA, Cormier, Susan ;


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6/08/2017  |   10:15 - 10:30   |  302B

ASSESSING HYDROLOGICAL FLUCTUATIONS THROUGH SPACE AND TIME USING TIME-LAPSE IMAGERY Variability of freshwater systems over space and time increases the difficulty of monitoring and understanding hydrological and environmental changes. Time-lapse imagery offers a passive technique of high-temporal resolution to monitor aquatic systems. With over forty time-lapse cameras installed across the Great Plains, the Platte Basin Time-lapse (PBT) project is a multimedia endeavor documenting a stressed watershed to contribute to scientific research, while simultaneously supporting science communication. We are exploring methods of streamlining visual and automated image analysis to understand hydrological fluctuations in relation to environmental variables at a range of temporal and spatial scales. We use batch image classification to quantify water inundation in ground-water fed lakes and sub-irrigated wetlands and employ time-series modeling to assess changing dynamics. In this presentation we present our preliminary findings, examples of time-lapse data sequences, and share ways that other researchers may engage with PBT. We invite you to explore more at www.plattebasintimelapse.com.

Emma Brinley Buckley (Primary Presenter/Author), Nebraska Educational Telecommunications, ebuckley@netad.unl.edu;


Mary Harner ( Co-Presenter/Co-Author), University of Nebraska at Kearney, harnermj@unk.edu;


Michael Farrell ( Co-Presenter/Co-Author), University of Nebraska - Lincoln, mfarrell@netad.unl.edu;


Michael Forsberg ( Co-Presenter/Co-Author), University of Nebraska - Lincoln, forsberg.mike@gmail.com;


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