SFS Annual Meeting

5/22/2018  |   11:00 - 11:15   |  330 B

DOES DENITRIFICATION GET MEMORIAL DAY OFF? AN EXAMINATION OF VARIATION IN DENITRIFICATION OVER DAILY TO SEASONAL TIME SCALES IN A FORESTED STREAMS Environmental conditions in streams vary from daily to seasonal time scales, likely driving similar temporal variation in biogeochemical processes. Yet, biogeochemists rarely quantify variation in processes at time scales shorter than seasonal. We are studying how denitrification rates vary across seasonal, weekly, and daily time scales and quantifying environmental drivers of this variability in two temperate forested streams in the Upper Peninsula of Michigan. We are measuring denitrification rates biweekly year-round, as well as daily over a 2-week period in spring, summer and fall starting in May 2017. Denitrification rates measured in sediment cores fluctuate throughout the year (range = 0 - 4160 µg N/m2/hr), with the highest rates in July and lowest in May and December. Yet, daily rates over a 2-week period in May exhibited a similar range in variability, increasing from 0 µg N/m2/hr on the first day of the sampling period to 2790 µg N/m2/hr on the last. We are currently expanding this study to include measurements of nitrification and open water metabolism. Studying these processes together will aid in understanding conditions driving variability in denitrification rates across temporal scales.

Kevin Nevorski (Primary Presenter/Author), Michigan Technological University, kcnevors@mtu.edu;


Amy Marcarelli (Co-Presenter/Co-Author), Michigan Technological University, ammarcar@mtu.edu;


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5/22/2018  |   11:15 - 11:30   |  330 B

PHARMACEUTICALS IMPACT BIOGEOCHEMICAL PROCESSES AND ALGAL COMMUNITY COMPOSITION IN ARTIFICIAL STREAMS Pharmaceuticals and Personal Care Products (PPCPs) are contaminants of concern in aquatic ecosystems and are detected in surface waters receiving wastewater. PPCPs pose a considerable risk to aquatic biota as they are biologically active by design, and have largely unknown effects on non-target organisms including aquatic microbes. Research indicates that select pharmaceuticals can inhibit functioning of aquatic organisms at low, environmentally relevant concentrations. However, the effects of PPCPs on whole-ecosystem structure and function are only now being investigated. We conducted a 21d artificial stream experiment to examine the effects of 3 commonly detected PPCPs (fluoxetine, diphenhydramine and ciprofloxacin) on stream ecosystem function. We examine effects on biogeochemical processes, including denitrification, primary production and respiration. We also explore how PPCPs alter the community compositions of diatoms in algal assemblages. Our results suggest that PPCPs are capable of altering ecosystem processes and we highlight important risks of PPCPs posed to freshwater systems and aquatic biota.

Stephanie Robson (Primary Presenter/Author), Monash University, stephanie.robson@monash.edu;


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


Michael Grace (Co-Presenter/Co-Author), Monash University , michael.grace@monash.edu;


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5/22/2018  |   11:30 - 11:45   |  330 B

THE EFFECTS OF LAND USE ON METABOLISM, NITRATE ASSIMILATION, AND DENITRIFICATION IN NEW ENGLAND STREAMS Aquatic ecosystem services are at risk of declining as a result of land use changes such as urbanization and agriculture. The effects of land use on stream processes such as metabolism, nitrogen fixation, and denitrification are poorly constrained in headwater streams. We sought to understand how land use affects biogeochemical cycling in headwater streams, hypothesizing that higher nutrient loading in urban and agricultural sites promotes metabolism and denitrification while reducing the role of nitrogen fixation. Three baseflow diel sampling rounds at each a forested, agricultural, and urbanized stream site were performed, while in situ nitrate sensors were also deployed periodically in each stream to quantify nitrate assimilation. Initial results indicated that the low nitrate forested stream showed nitrogen fixation, while the higher nitrate urban and agricultural streams showed denitrification. All sites were net heterotrophic but metabolic rates differed across land use types, with net daily metabolism ranging from 4.91 to 25.12 g/m2/day. These results suggest that the dominant ecosystem functions in small streams shift in response to land use change which may have implications for stream restoration.

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


Daniel Bolster (Primary Presenter/Author), University of New Hampshire, drb1020@wildcats.unh.edu;


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5/22/2018  |   11:45 - 12:00   |  330 B

STREAM NITROGEN FLUXES UNDER VARIABLE NUTRIENT LOADING Nitrogen fixation can contribute large fluxes of dissolved nitrogen gas (N₂) into aquatic biofilms, frequently in low nitrate streams. By contrast, denitrification is often studied in streams to investigate nitrate removal rates for use in remediation. We investigated both nitrogen fixation and denitrification rates across 9 streams in Wyoming and Colorado with varying nitrate concentrations. We predicted nitrogen fixation will correspond with light and gross primary production (GPP) while inversely related to denitrification and nitrate concentrations. We coupled whole stream N₂ models with diel data for nitrogen fixation and 10 microcosms. Nitrogen fixation ranged from 0.0 to 0.2 g N₂ m^-2d^-1 and GPP ranged from 1.3 to 6.2 g O₂ m^-2d^-1. Nitrogen fixation measured in microcosms varied dielly with light levels and GPP and was high when denitrification fluxes were low. In low nitrate streams, nitrogen fixation fluxes were up to 7 times higher than denitrification. Nitrogen fixation contributed to stream nitrogen cycling, especially in streams low nitrate, low denitrification streams.

Hilary Madinger (Primary Presenter/Author), University of Wyoming, hilary.madinger@gmail.com;


Robert O. Hall (Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, bob.hall@flbs.umt.edu;


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5/22/2018  |   12:00 - 12:15   |  330 B

DECADAL TRENDS AND DRIVERS OF NITROGEN CONCENTRATIONS IN GRASSLAND STREAMS Grasslands are highly threatened biomes and there is little information on how pristine grassland streams have been modified over time. Furthermore, headwater streams are critical predictors of downstream nutrient concentrations, and their nutrient export is influenced by factors including climate and land-use. We used water quality data from 1983-2016 from Konza Prairie Biological Station to examine how N export from a grassland watershed has changed on a decadal scale. Long term data from Konza Prairie allow examination of how N export is influenced by factors such as land-use, precipitation, and hydrology. Trend analysis showed an increasing trend for reduced N (as NH4+) at large spatial scale and decreasing trend for oxidized N (as NO3-) on a more local scale. Regression analysis indicated that atmospheric deposition of N is important for reduced and oxidized N, but hydrology and prairie restoration are more significant for oxidized N. Our results highlight varying scales of influence that impact water quality in low-order grassland streams. Local land-use variables appear to be crucial for oxidized N, while large-scale disturbances are more important for reduced N.

James Guinnip (Primary Presenter/Author), Kansas State University, jguinnip@ksu.edu;


Walter Dodds (Co-Presenter/Co-Author), Kansas State University, wkdodds@ksu.edu;


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5/22/2018  |   12:15 - 12:30   |  330 B

SEASON OR LAND-USE? EXPLORING THE DRIVERS OF WATER QUALITY IN AN AGRO-URBAN WATERSHED OF CENTRAL IOWA The Raccoon River is the source of drinking water for over 500,000 Iowans and provides a host of additional ecosystem services. However, like many Midwestern US rivers, the Raccoon suffers from high nitrate and suspended sediment concentrations. To investigate the spatial and temporal factors that most strongly influence water quality, we conducted an 18-month study of nine locations throughout the lower Raccoon River watershed, including three branches of the river as well as the mainstem in Des Moines. We measured suspended sediment and nitrate concentrations every two weeks and rates of sediment denitrification monthly. Seasonal factors strongly influenced nitrate; the highest concentrations occurred in the spring and were lowest in the fall (10.4 and 1.9 mgN/L, respectively). Similarly, denitrification rates were generally consistent across sites, but varied through time with winter rates up to 50% lower than summer rates. Further analyses will explore the contribution of the variation in land-use on water quality among the three branches of the Raccoon. Understanding the spatial and temporal drivers of nitrate and suspended sediment in agro-urban watersheds can contribute to effective management of rivers in human-dominated landscapes.

Peter S. Levi (Primary Presenter/Author), Drake University, peter.levi@drake.edu;


Emily D. Anderson (Co-Presenter/Co-Author), Drake University, emily.d.anderson@drake.edu;


Katie VanDooren (Co-Presenter/Co-Author), Drake University, katie.vandooren@drake.edu;


Angela L. Bowman (Co-Presenter/Co-Author), Iowa State University, albowman73@gmail.com;


Amy J. Burgin (Co-Presenter/Co-Author), University of Kansas, burginam@ku.edu;


Caroline A. Davis (Co-Presenter/Co-Author), University of Iowa, caroline-davis@uiowa.edu;


Christopher S. Jones (Co-Presenter/Co-Author), University of Iowa, christopher-s-jones@uiowa.edu;


Terrance D. Loecke (Co-Presenter/Co-Author), University of Kansas, loeckete@gmail.com;


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