SFS Annual Meeting

5/21/2019  |   09:00 - 09:15   |  151 ABC

STRUCTURAL AND FUNCTIONAL TRAJECTORIES OF BIOFILM COMMUNITY SUCCESSION Limited understanding of biofilm community succession precludes our ability to forecast short-term responses of stream ecosystems to pressing environmental problems such as increasing sediment loads or flooding frequency. To examine succession trajectories of biofilm structure and function we employed artificial streams in which epilithic biofilms were first developed to mature stages and then exposed to flooding disturbances of contrasting intensity. Over a 6-week period, we monitored structural (bacteria and algal abundance and diversity) and functional (species interactions, nutrient uptake, and enzyme activity) attributes pre and post-disturbance. Diatom abundance increased faster than other algal groups (3.73ug/cm2/d; p <0.001) resulting in mature Melosira-dominated biofilms (18.3±1.3 gAFDM/m2) after approximately 3 weeks. High- and low-intensity floods removed 68 and 54% of the organic matter standing stocks and 71% and 37% of diatom standing stocks, respectively. Biomass-specific N uptake rates (ug N/gAFDM/h) were significantly lower in later (11±2) than early (371±124) stages of biofilm succession, suggesting stronger N-recycling pathways in mature biofilms. Ongoing analysis of co-occurrence microbial networks based on subunit ribosomal RNA genes (16S) assessment and extracellular enzyme activities will provide further assessment of N-recycling pathways and the overall trajectories of biofilm community succession.

Marc Peipoch (Primary Presenter/Author), Stroud Water Research Center, mpeipoch@stroudcenter.org;


Raven Bier (Co-Presenter/Co-Author), Stroud Water Research Center, rbier@stroudcenter.org;


Jing Wang (Co-Presenter/Co-Author), Stroud Water Research Center, jwang_hku@163.com;


Jinjun Kan (Co-Presenter/Co-Author), Stroud Water Research Center, jkan@stroudcenter.org;


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5/21/2019  |   09:15 - 09:30   |  151 ABC

MODELING AND PREDICTING THE OCCURRENCES OF ANTIBIOTIC RESISTANCE GENES IN US RIVERS AND STREAMS Antimicrobial resistance (AMR) of pathogens is a critical threat to human and animal health. Human activities enhance the spread of AMR and AMR can be detected in streams by PCR targeting antibiotic resistance genes (ARGs). Understanding anthropogenic drivers of this spread is critical to develop effective monitoring and mitigation. Here, we identified potential ecological drivers to model and predict the probability of occurrence of four ARGs (sul1, tetW, blaTEM, and KPC), a gene associated with AMR mobilization (intI1), and two potential pathogenic indicators (E. coli and enterococci). We paired gene occurrences from ~2,000 stream samples across the US (USEPA NRSA) with several watershed attributes, including urbanization and agriculture (StreamCat dataset). We used random forests to model gene occurrences in response to watershed land use intensity. The models correctly predicted ARGs at 70%-82% of sites but varied in their ability to balance type I and II errors. We then predicted ARG occurrences at 1.1 million stream reaches. The resulting maps reflect the relative importance of urbanization, agriculture, or other landscape stressors on the occurrence of each gene and can indicate where focused surveillance and mitigation of AMR may be needed.

Ryan Hill (Primary Presenter/Author), US Environmental Protection Agency, hill.ryan@epa.gov;
Ryan Hill is an aquatic ecologist with the U.S. EPA Office of Research and Development. He is interested in how watershed conditions drive differences in freshwater diversity and water quality across the United States. He has worked extensively with federal physical, chemical, and biological datasets to gain insights into the factors affecting water quality and biotic condition of freshwaters across the conterminous US. He has also worked to develop and distribute large datasets of geospatial watershed metrics for streams and lakes for the Agency (EPA’s StreamCat and LakeCat datasets). Ryan completed his PhD in Watershed Ecology at Utah State University in 2013 with Dr. Chuck Hawkins. He was an ORISE postdoctoral fellowship at the U.S. EPA from 2014-2019 before joining the EPA in 2019.

Michael Jahne (Co-Presenter/Co-Author), US EPA, Systems Exposure Division, Cincinnati, OH, jahne.michael@epa.gov;


Scott Keely (Co-Presenter/Co-Author), US EPA Systems Exposure Division, Cincinnati, OH, keely.scott@epa.gov;


Nichole Brinkman (Co-Presenter/Co-Author), US EPA, Systems Exposure Division, Cincinnati, OH, brinkman.nichole@epa.gov;


Richard Haugland (Co-Presenter/Co-Author), US EPA, Exposure Methods & Measurement Division, Cincinnati, OH, haugland.rich@epa.gov;


Scott Leibowitz (Co-Presenter/Co-Author), US EPA, Pacific Ecological Systems Division, Corvallis, OR, leibowitz.scott@epa.gov;


Emily Wheaton (Co-Presenter/Co-Author), US EPA, Systems Exposure Division , Cincinnati, OH, Wheaton.Emily@epa.gov;


Jay Garland (Co-Presenter/Co-Author), US EPA, Systems Exposure Division , Cincinnati, OH, garland.jay@epa.gov;


Roy Martin (Co-Presenter/Co-Author), US EPA, Systems Exposure Division, Cincinnati, OH, martin.roy@epa.gov;


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5/21/2019  |   09:30 - 09:45   |  151 ABC

EFFECTS OF TEMPERATURE ON ACTIVITY OF STREAM MICROORGANISMS ASSOCIATED WITH DECAYING LEAF LITTER Increases in mean temperature under climate-change predictions are expected to affect microbial activity and carbon dynamics in aquatic ecosystems. We explored responses of litter-associated decomposers (fungi and bacteria) along temperature ranges typical of temperate streams to test whether microbial responses can be explained by the Metabolic Theory of Ecology (MTE). Our experiment in laboratory microcosms simulated stream conditions and measured physiological responses of natural stream microbial assemblages colonizing Liriodendron tulipifera leaf disks to temperature (5 levels, 4-20°C). We determined litter decomposition rates, fungal biomass (ergosterol), fungal and bacterial production (radiolabeled tracers), spore production by aquatic fungi, microbial respiration rates and activity of enzymes involved in carbon sequestration. We found that responses of aquatic litter-associated microorganisms to increases in temperature are more complex than predicted by the MTE, with more pronounced fungal responses (higher apparent activation energy, E) at lower temperatures. For some parameters, estimates of E at lower temperatures were higher than canonical values often reported for respiration (~0.65 eV), suggesting that fungi and microbial carbon processing in temperate streams could be especially sensitive to temperature increases during the key winter period of high activity.

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


Hunter Pates (Co-Presenter/Co-Author), Coastal Carolina University, hpates@coastal.edu;


Nicholas Bautz (Co-Presenter/Co-Author), Coastal Carolina University, bautznicholas@gmail.com;


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


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


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5/21/2019  |   09:45 - 10:00   |  151 ABC

BACTERIAL SUCCESSION IN HEADWATER BIOFILMS Microbial biofilms are vital components of nutrient uptake and cycling processes in freshwater ecosystems, but we are still learning how microbes colonize and develop to mature biofilms in stream waters. We evaluated succession of microbial communities initiated in both summer and winter in a well-studied catchment in southeastern Pennsylvania, USA. High throughput sequencing of 16S rRNA genes suggested distinct biofilm structures starting from different seasons. Phototrophic and heterotrophic microbes showed different strategies, with a higher percentage (62.94%) of chloroplasts in winter-initiated biofilms but higher abundance of Proteobacteria (60.22%) in summer-initiated samples in the first month. Interestingly, after the first month both summer and winter-initiated successions had similar community composition, indicating tendency and stability of the internal community structure. Network analysis showed more robust correlations between algae and Cyanobacteria with heterotrophic bacteria in winter than in summer, especially for the first month, suggesting a strong competition for habitats. Results from this study have identified unique roles of phototrophic and heterotrophic bacteria in early and later stages of succession in freshwater streams, which is a key part for understanding ecological roles of microbes in freshwater as well as global aquatic ecosystems.

Jinjun Kan (Primary Presenter/Author), Stroud Water Research Center, jkan@stroudcenter.org;


Jing Wang (Co-Presenter/Co-Author), Stroud Water Research Center, jwang_hku@163.com;


Marc Peipoch (Co-Presenter/Co-Author), Stroud Water Research Center, mpeipoch@stroudcenter.org;


Raven Bier (Co-Presenter/Co-Author), Stroud Water Research Center, rbier@stroudcenter.org;


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