6/08/2017  |   11:00 - 11:15   |  305B

EFFECTS OF TEMPERATURE ON ACTIVITY OF AQUATIC FUNGI AND LEAF LITTER DECOMPOSITION Climate change is expected to affect rates of heterotrophic activity and carbon dynamics in streams. The Metabolic Theory of Ecology (MTE) can guide predictions of metabolic activity of organisms with increased temperature; however, multiple factors can cause deviations from simple MTE expectations. We assessed the temperature sensitivity of aquatic hyphomycetes and leaf litter decomposition and estimated the activation energy (E) of several fungi-mediated processes across different temperature intervals. We followed fungal biomass accrual, sporulation, respiration, enzymatic activity and litter decomposition in laboratory microcosms simulating stream conditions. We found that fungal parameters and decomposition rates often do not follow simple MTE predictions, i.e. estimates of E varied depending on temperature interval. We observed much greater temperature sensitivity of microbial parameters at 5-10 C than at higher temperatures (15-20 C). Also, at low temperatures, estimates of E for parameters of fungal activity and decomposition rate (up to 1.46 and 0.96 eV, respectively) often greatly exceeded canonical estimates for respiration (~0.65 eV). These trends may have important implications for stream ecosystems under climate change scenarios, since bulk leaf litter inputs and peak microbial activity coincide with the coldest season (autumn-winter) in temperate streams.

Vlad Gulis (Primary Presenter/Author), Coastal Carolina University, vgulis@coastal.edu;


Kyra Harrington ( Co-Presenter/Co-Author), Coastal Carolina University, klharring@g.coastal.edu;


Jonathan P. Benstead ( Co-Presenter/Co-Author), The University of Alabama, jbenstead@ua.edu;


Amy D. Rosemond ( Co-Presenter/Co-Author), University of Georgia, rosemond@uga.edu;


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6/08/2017  |   11:15 - 11:30   |  305B

QUANTITATIVE STABLE ISOTOPE PROBING: WHAT IS IT, HOW DOES IT WORK, AND WHY IS IT IMPORTANT FOR FRESHWATER ECOLOGY? Understanding how the population dynamics of species contribute to ecosystem processes is a primary focus of ecological research, and has led to important breakthroughs in the ecology of macroscopic organisms. However, the inability to measure population-specific rates, such as growth, for microbial taxa within natural assemblages limits our understanding of how those taxa interact to regulate processes such as primary production, decomposition, and nutrient cycling. By combining techniques from microbiology, molecular biology, and bioinformatics, we have developed a new tool: quantitative stable isotope probing (qSIP), for estimating taxon-specific growth and mortality within intact microbial assemblages. We use isotope substitution within DNA molecules to model taxon-specific population growth in the presence of ¹⁸O-labeled water. By applying this model to phylogenetic marker sequencing data collected from tracer incubations of environmental samples, we demonstrate how qSIP can be used to estimate rates of growth, mortality, and turnover for individual populations of prokaryotic taxa within intact microbial assemblages. We outline some of the opportunities for applying this approach to freshwater ecosystems to elucidate how microbial populations drive biogeochemical fluxes and food web dynamics.

Benjamin Koch (Primary Presenter/Author), Northern Arizona University, ben.koch@nau.edu;


Bruce Hungate ( Co-Presenter/Co-Author), Northern Arizona University, bruce.hungate@nau.edu;


Jane Marks ( Co-Presenter/Co-Author), Northern Arizona University, jane.marks@nau.edu;


Rebecca Fritz ( Co-Presenter/Co-Author), Northern Arizona University, rjf227@nau.edu;


Michaela Hayer ( Co-Presenter/Co-Author), Northern Arizona University, michaela.hayer@nau.edu;


Rebecca Mau ( Co-Presenter/Co-Author), Northern Arizona University, rlm284@nau.edu;


Theresa McHugh ( Co-Presenter/Co-Author), Colorado Mesa University, mchughtheresa@gmail.com;


Ember Morrissey ( Co-Presenter/Co-Author), West Virginia University, ember.morrissey@mail.wvu.edu;


Egbert Schwartz ( Co-Presenter/Co-Author), Northern Arizona University, egbert.schwartz@nau.edu;


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6/08/2017  |   11:30 - 11:45   |  305B

EXPLORING FRESHWATER MICROBIOMES USING QUANTITATIVE STABLE ISOTOPE PROBING Freshwater microbes associated with leaf litter decomposition serve as a food resource for aquatic insects. Insects also have microbial communities in their guts to assist digestion. Quantitative stable isotope probing (qSIP) is a novel molecular tool to differentiate active from inactive microbes. This technique uses, ‘heavy water,’ H₂¹⁸O to isotopically label microbial taxa and estimate their growth rates. This experiment addresses three questions: Does the activity rate of individual microbial taxa differ across leaf types during decomposition? How does the presence of shredders affect the microbial assemblage and growth rates of individual taxa? Do the microbes that are active in the guts of insects reflect the microbes found on decomposing leaves? Results indicate that microbial communities differ across leaf types and during decomposition. Growth rates of microbes are not correlated with their abundances suggesting that taxa in low abundance might be important in organic matter processing. We will discuss a model for viewing microbes with respect to ecological roles often used to describe macroscopic organisms.

Rebecca Fritz (Primary Presenter/Author), Northern Arizona University, rjf227@nau.edu;


Michaela Hayer ( Co-Presenter/Co-Author), Northern Arizona University, michaela.hayer@nau.edu;


Rebecca Mau ( Co-Presenter/Co-Author), Northern Arizona University, rlm284@nau.edu;


Benjamin Koch ( Co-Presenter/Co-Author), Northern Arizona University, ben.koch@nau.edu;


Alexa Schuettenberg ( Co-Presenter/Co-Author), Northern Arizona University, aas322@nau.edu;


Egbert Schwartz ( Co-Presenter/Co-Author), Northern Arizona University, egbert.schwartz@nau.edu;


Bruce Hungate ( Co-Presenter/Co-Author), Northern Arizona University, bruce.hungate@nau.edu;


Jane Marks ( Co-Presenter/Co-Author), Northern Arizona University, jane.marks@nau.edu;


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6/08/2017  |   11:45 - 12:00   |  305B

Denitrification potential in a dynamic environment: influences of flow variation, vegetation, and geomorphology in waterways and riparian zones of an irrigated agricultural landscape Denitrification, the microbial conversion of nitrate to nitrogen gases, can greatly influence whether lotic and riparian ecosystems act as sinks for agricultural nitrate pollution. Though agricultural waterways and riparian zones have been a focus of denitrification research for decades, almost none of this research has occurred in the irrigated agricultural settings of arid and semi-arid climates. This setting provides unique conditions that may advance our understanding of denitrification, including management-associated heterogeneity in flow conditions, vegetation, and geomorphology. We measured potential denitrification in riparian soils and channel sediments from 79 waterway reaches in the irrigated agricultural landscape of California’s Central Valley. We found strong associations of sediment denitrification potentials with flow conditions, which we hypothesize resulted from variation in microbial communities’ resilience to dry-wet cycles. Denitrification potentials in riparian soils, in contrast, did not appear affected by flow conditions, but instead were associated with organic matter, vegetation cover, and slope in the riparian zone. These results advance understanding of how denitrification responds to varying flow conditions in non-perennial lotic ecosystems. Our findings also demonstrate that denitrifier communities respond to waterway management, which can therefore be leveraged to address agricultural nitrate pollution.

Alex Webster (POC,Primary Presenter), University of New Mexico, awebster2@unm.edu;


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


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


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6/08/2017  |   12:00 - 12:15   |  305B

PATHOGENIC BACTERIA AND ANTIBIOTIC RESISTANCE IN SOUTH DAKOTA SURFACE WATERS Between 2003 and 2012, there were 390 E. coli O157 outbreaks in the US, including 15 waterborne outbreaks that sickened 154 people, including one fatality. In 2012, South Dakota ranked third for STEC infection and first for E. coli O157 infection. Additionally, South Dakota experienced the highest number of recorded STEC infections in history in 2016 with an 86% increase over the five-year average. Routine fecal contamination testing does not take into account the bacterial pathogenicity. Rapid Creek, Skunk Creek, and the Big Sioux River have exceeded standards for fecal coliforms and/or E. coli. We have developed and applied a pathogenicity metric to assay the disease-causing potential of organisms in impaired surface water. From total DNA isolated from water samples, we detected genes encoding two Shiga toxins (stx1/VT1; stx2/VT2), an intimin (eaeA), an enterohemolysin (ehxA), and an enteroinvasin (einV). We screened a subset of our samples for antibiotic resistance genes finding Amp-C, Tet-C , Str-A , and a Van-A gene as well as multiply resistant organisms. These results indicate a higher potential health risk than does measuring E. coli alone.

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


Kelsey Murray ( Co-Presenter/Co-Author), South Dakota School of Mines and Technology, kelsey.murray@mines.sdsmt.edu;


Ashley Preston ( Co-Presenter/Co-Author), South Dakota School of Mines and Technology, ashley.ditlev@mines.sdsmt.edu;


Linda DeVeaux ( Co-Presenter/Co-Author), South Dakota School of Mines and Technology, linda.deveaux@sdsmt.edu;


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6/08/2017  |   12:15 - 12:30   |  305B

WOLBACHIA IS COMMON AMONG, BUT NOT NECESSARILY WITHIN, AQUATIC INSECT SPECIES Wolbachia is a genus of bacteria commonly found within the reproductive tissues of arthropods and can cause an array of different effects on their hosts. A recent study found that 52% (CIs 44% - 60%) of aquatic species are infected with Wolbachia. This is similar to previous estimates of the incidence of Wolbachia in terrestrial insects. However, knowledge of the prevalence within species (i.e. the proportion of individuals infected) is unknown. We constructed a model that estimated the proportion of insects infected with Wolbachia within 244 aquatic insect species using data from previously published surveys. Preliminary findings indicate that at least half of the aquatic insect species infected with Wolbachia harbor infections below 5%. This varies widely across orders and families, however, and the estimates for many species are uncertain due to low sample sizes.

Eric Sazama (Primary Presenter/Author), University of South Dakota, ericjsazama@gmail.com;


Scot Ouellette ( Co-Presenter/Co-Author), University of Nebraska Medical Center, scot.ouellette@unmc.edu;


Jeff Wesner ( Co-Presenter/Co-Author), University of South Dakota, Jeff.Wesner@usd.edu;


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