5/23/2016  |   13:30 - 13:45   |  309-310

METHANE AND METHYLMERCURY PRODUCTION POTENTIALS IN NORTH CAROLINA PIEDMONT STREAM SEDIMENTS Anaerobic microbes with a variety of metabolic pathways can methylate mercury, including sulfate reducing bacteria (SRB), iron reducing bacteria (FeRB), and methane producing Archaea (MPA). Competition for substrate occurs between SRB and MPA, with SRB outcompeting MPA when sulfate is in excess. Low concentrations of sulfate in streams are thought to reduce SRB activity in streams. However, SRB are known to be the dominant methylmercury (MeHg) producers in many aquatic environments. Potential contributions to MeHg production from microbes and MPA activity in a subset of North Carolina Piedmont streams is evaluated in this research. Our data suggest SRB exihibit control on methane production by MPA. Mercury methylation remained unchanged from the control when the activity of MPA was inhibited. However, when SRB were inhibited there was reduced MeHg production, similar to when both microbial groups were inhibited. In these experimentally manipulated sediments SRB were the dominant MeHg producers; other microbes (e.g., FeRB) contributed to MeHg production; and MPA produced a negligible amount of MeHg.

Peter Blum (Primary Presenter/Author), The University of North Carolina at Greensboro, pwblum@uncg.edu;


Anne Hershey ( Co-Presenter/Co-Author), The University of North Carolina at Greensboro, aehershe@uncg.edu;


M.T.K. Tsui ( Co-Presenter/Co-Author), The University of North Carolina at Greensboro, tmtsui@uncg.edu;


Steven Whalen ( Co-Presenter/Co-Author), University of North Carolina at Chapel Hill, whalen@email.unc.edu;


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5/23/2016  |   13:45 - 14:00   |  309-310

CHARACTERIZING THE PRESENT AND FUTURE EXTENT OF CHLORIDE IMPAIRMENT IN THE MERRIMACK RIVER NEW HAMPSHIRE USA In temperate developed watersheds, road salt application drives chloride loading to freshwater streams, but climatological factors affect actual ecological impairment. We present the development, parameterization, and several applications of a regional hydrologic and chloride transport model (FrAMES-NACL). Seasonal climate controls on impairment, the duration and extent that concentrations exceed a tolerance threshold, depend on scale: winter-severity drives contamination in low-order streams (loading dominated), whereas runoff from pristine headwaters is important downstream (dilution dominated). We assess the sensitivity of future chloride storage and impairment to build-out, carbon emissions, and management strategies using scenarios of land-cover and climate change at the watershed scale through 2100. USEPA chronic impairment changes between -57% to +67% depending on land-cover and road salt application rate. Simulations assuming lower road salt application, increasing (+260%) population, and low-carbon emissions yield no significant increase in mean pristine river length. However, pristine river length decreases for dispersed build-out, and future droughts increase impairment by legacy chloride in groundwater. Projected population in New England requires reducing road salt to preserve existing aquatic habitat.

Shan Zuidema (Primary Presenter/Author), University of New Hampshire, shan.zuidema@unh.edu;


Wilfred M. Wollheim ( Co-Presenter/Co-Author), University of New Hampshire, wil.wollheim@unh.edu;


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5/23/2016  |   14:00 - 14:15   |  309-310

THE GEOCHEMICAL INFLUENCE OF TRACE ELEMENT CONCENTRATIONS FROM MARINE SEDIMENTARY BEDROCK ON FRESHWATER STREAMS IN THE WESTERN TRANSVERSE MOUNTAIN RANGES Government agencies assess the biological integrity of streams and the chemistry of groundwater to monitor for anthropogenic impacts. Some of the impacted streams lack obvious stressors that can be linked to the impacts. In the case of elevated nutrients and ionic concentrations found in impacted stream sites within the Malibu Creek Watershed, research from the Las Virgenes Municipal Water District pointed towards the leachate from the Modelo formation, which contests previous studies suggesting an anthropogenic influence. Differentiating between natural water chemistry and point/non-point source contamination could aid in resolving water quality issues since monitoring occurs near anthropogenic development. Water, bedrock, and diatoms were sampled from spring, seep, and stream sites underlain by Tertiary/Cretaceous sedimentary bedrock throughout the study area. Multivariate analyses revealed site groupings driven by salinity along with a correlation between geochemistry and diatom assemblages. Mixing models and radar charts identified potential rock types as sources for analyte concentrations. Sites that were underlain by the Modelo formation presented brackish water and high nutrient concentrations resulting from weathering, which potentially influences the diatom species compositions found at the spring/seep sites.

Jose Caprile (Primary Presenter/Author), California State University, Long Beach, caprile.ja@gmail.com;


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5/23/2016  |   14:15 - 14:30   |  309-310

DIDYMOSPHENIA GEMINATA IN GRAND TETON NATIONAL PARK, WY: DISTRIBUTION, MAT STOICHIOMETRY, AND BIOGEOCHEMISTRY Didymosphenia geminata, a freshwater diatom, produces copious amounts of extracellular stalk material in streams and rivers. Unlike most algal blooms, which occur under eutrophic conditions, D. geminata creates thick (up to 10cm) mats in oligotrophic waters. Prevalence of D. geminata mats has increased worldwide over the past two decades. Since the early 2000s, D. geminata mats have been present in Lake Creek, Grand Teton National Park, WY. Between 2008 and 2015, we surveyed 24 streams in Grand Teton National Park and surrounding areas, examined 3 sediment cores for historical distribution, mapped mat extent, sampled for mat stoichiometry, and examined nutrient limitation and biogeochemical fluxes. Cells of D. geminata were present in Phelps Lake prior to the thick mats developing in the outlet. We observed an increase in mat prevalence in multiple streams. Mat stoichiometry depicts a shift in benthic resources with C:N as high as 22, C:P to 2382, and N:P to 107, resembling stoichiometry of terrestrial leaves. Didymosphenia geminata mats alter ecosystem processes and functions including increases in P uptake and N₂-fixation.

Lisa Kunza (Primary Presenter/Author), South Dakota School of Mines and Technology, lisa.kunza@sdsmt.edu;


Jaime Haueter ( Co-Presenter/Co-Author), South Dakota School of Mines and Technology, jaime.haueter@mines.sdsmt.edu;


Christopher Schiller ( Co-Presenter/Co-Author), South Dakota School of Mines and Technology, christopher.schiller@mines.sdsmt.edu;


Sarah Spaulding ( Co-Presenter/Co-Author), U.S. Geological Survey, Institute of Arctic and Alpine Research, University of Colorado Boulder, sarah.spaulding@colorado.edu;


Emily Stickney ( Co-Presenter/Co-Author), South Dakota School of Mines and Technology, emily.stickney@mines.sdsmt.edu;


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5/23/2016  |   14:30 - 14:45   |  309-310

BIOGEOCHEMISTRY OF SEABIRD SUBSIDIES IN STREAM ECOSYSTEMS: PATTERNS IN ECOLOGICAL STOICHIOMETRY Despite the established importance of ecological stoichiometry in controlling ecological processes such as reproduction and nutrient cycling, the mechanistic understanding of nutrient assimilation is poorly understood. In particular, whether marine nutrients enhance ecological stoichiometry or merely replace nutrient atoms already present is not known. To test this question on two scales we compared the relationship between C:N ratios and delta¹⁵N values in fish, benthic invertebrates, coarse particulate organic matter (CPOM), and riparian soil and vegetation in 8 streams with varying intensity of seabird subsidies. At an individual ecosystem component level marine N replaced existing N rather than enhancing C:N in ecosystems receiving seabird subsidies. Although stoichiometric replacement suggests seabird N has little effect on stream biota life history, further research is needed to determine the full biogeochemical implications of stoichiometric replacement. At an ecosystem scale, marine N enhanced C:N when moving across the terrestrial-aquatic interface and into the freshwater community (P<0.05). This ecosystem-scale enhancement of C:N matches theoretical predictions for carbon and nitrogen as they move into streams, but has not previously been demonstrated in systems experiencing marine enrichment.

Roseanna Gamlen-Greene (Primary Presenter/Author), University of British Columbia, roseanna.gamlen.greene@gmail.com;


Jon Harding ( Co-Presenter/Co-Author), University of Canterbury, jon.harding@canterbury.ac.nz;


David Hawke ( Co-Presenter/Co-Author), Christchurch Polytechnic Institute of Technology, david.hawke@cpit.ac.nz;


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