6/08/2017  |   09:00 - 09:15   |  306A

EXTENSIVE SPATIOTEMPORAL VARIATION IN NUTRIENT CONCENTRATIONS OF LAKE MICHIGAN’S TRIBUTARIES Despite efforts to reduce nutrient loads to the Laurentian Great Lakes since the 1970’s, nutrient inputs continue to cause coastal eutrophication and degrade ecosystem services. Tributaries are a practical focus for quantifying nutrient loads from watersheds, and understanding spatial and temporal drivers of tributary nutrient concentrations is critical for managing nutrient loads. We circumnavigated Lake Michigan quarterly to analyze nutrient concentrations in ~100 tributaries. Tributaries were selected randomly with stratification by watershed area and land use. We find only weak effects of watershed area on tributary nutrient concentrations. However, phosphorus and nitrogen concentrations increase and carbon concentrations decrease with increasing agricultural and urban land uses. Strong seasonal variation in nutrients complicates interpretation of land use effects; for instance, nitrate concentrations are highest in the summer, but effects of land use are stronger in fall and winter. Overall, we find carbon, nitrogen, and phosphorus concentrations (and associated stoichiometries) vary by up to 3 orders of magnitude among Lake Michigan tributaries. Our seasonal and spatial sampling regimen offers insight into the challenge of managing nutrient loads in this landscape.

Robert J. Mooney (Primary Presenter/Author), Center for Limnology, University of Wisconsin - Madison, rjmooney@wisc.edu;


Galen A. McKinley ( Co-Presenter/Co-Author), University of Wisconsin - Madison, gamckinley@wisc.edu;


Lucas Gloege ( Co-Presenter/Co-Author), University of Wisconsin - Madison, gloege@wisc.edu;


Christina K. Remucal ( Co-Presenter/Co-Author), University of Wisconsin - Madison, remucal@wisc.edu;


Megan B. McConville ( Co-Presenter/Co-Author), University of Wisconsin - Madison, mmcconville@wisc.edu;


Peter B. McIntyre ( Co-Presenter/Co-Author), Center for Limnology, University of Wisconsin-Madison, pmcintyre@wisc.edu;


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6/08/2017  |   09:15 - 09:30   |  

Sediment quality criteria for heavy metals in Dongting Lake based on screening level concentration approach 129 surface sediment samples and the co-occurrence in sediments of macrozoobenthos samples were collected from Dongting Lake during 2013-2015. Concentrations of six heavy metals—arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn) in the sediment were measured and the species composition of macrozoobenthos were identified. The results showed that the average concentration of As, Cd, Cr, Cu, Pb, Zn was 17.2, 2.63, 56.9, 32.4, 38.4 and 96.3 mg/kg (dry weight) respectively. Based on the field data on the co-occurrence in sediments of macrozoobenthos and concentrations of the six heavy metals, the screening level concentration (SLC) approach was induced to preliminarily discuss the sediment quality criteria (SQC) recommended values of the six heavy metals for surface sediments from Dongting Lake. The calculated SQCs of As, Cd, Cr, Cu, Pb and Zn of Dongting Lake were 11.97, 1.13, 42.03, 19.17, 23.63 and 67.54 mg/kg (on the basis of dry weight). These SQC values of heavy metals in Dongting Lake came from this study were comparative with those from other derivation methods.

Yanmin Zhao (Primary Presenter/Author), Chinese Research Academy of Environmental Sciences, zhaoym@craes.org.cn;


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6/08/2017  |   09:30 - 09:45   |  306A

USING STREAM TEMPERATURE DISTRIBUTIONS INSTEAD OF SINGLE METRICS TO EVALUATE THERMAL RESPONSES TO FOREST HARVEST Stream temperatures are influenced by numerous processes, especially changes in land management. Maximum daily temperature is a commonly used metric for evaluating responses. However, single metrics do not fully represent the magnitude and duration of temperatures experienced by instream biota. Analyses that make use of all the data more accurately a) characterize shifts in summer stream temperature regimes, b) quantify potential exposure to critical and non-critical temperatures, and c) help researchers and managers to better understand stream temperature responses to manipulations. Here we examine the distributions of summer stream temperatures before and after forest harvest in the Trask River Watershed Study in northwestern Oregon. We studied 15 small streams for 10 years; half of the watersheds were clearcut harvested in 2012. We observed high spatial and temporal variation among sites and years, with some sites having normally distributed temperatures, while others showed skewed distributions and long tails. We compare observed temperatures to known thermal tolerances for tailed frog tadpoles, Ascaphus truei. With these analyses, we are quantifying chronic exposure, which could subsequently result in shifts in phenology or community structure.

Sherri Johnson (Primary Presenter/Author), U.S. Forest Service, Pacific Northwest Research Station, sherrijohnson@fs.fed.us;


Maryanne Reiter ( Co-Presenter/Co-Author), Weyerhaeuser Company, maryanne.reiter@weyerhaeuser.com;


Jay Jones ( Co-Presenter/Co-Author), Weyerhaeuser Company, Jay.Jones@weyerhaeuser.com;


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6/08/2017  |   09:45 - 10:00   |  306A

IN-STREAM CARBON CYCLE IMPACTS FROM WATERSHED-SCALE IMPLEMENTATION OF WINTER COVER CROPS: DOC AND GREENHOUSE GAS DYNAMICS Dissolved organic carbon (DOC) plays a role in many biogeochemical processes, including greenhouse gas production. Agricultural land use can impact stream DOC through tillage, cropping, and subsurface tile drainage. Conservation practices, such as winter cover crops, can mitigate agricultural impacts on streams, but watershed-scale impacts on DOC dynamics remain understudied. We analyzed bi-weekly DOC samples from two tile-drained agricultural watersheds beginning in June 2015: one with 70% of croppable acres in winter cover crops, and one with 20%. We also collected monthly dissolved carbon dioxide, methane, and nitrous oxide samples from tile drains and streams in the minimally cover-cropped watershed. DOC concentrations varied seasonally, and across the two watersheds and stream concentrations were higher than tile drain water (3 mg/L and 1.5 mg/L, respectively). Streams were typically super-saturated in all three gases, and for carbon dioxide and methane, stream concentrations were several fold higher than in tile water. The relationships between DOC and greenhouse gases will enhance our understanding of the carbon cycle in agroecosystems, with potentially important implications for biogeochemical processes and water quality in these intensively-managed landscapes.

Kara Prior (Primary Presenter/Author), Indiana University, kprior@indiana.edu;


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


Jennifer L. Tank ( Co-Presenter/Co-Author), University of Notre Dame, tank.1@nd.edu;


Shannon Speir ( Co-Presenter/Co-Author), University of Arkansas, slspeir@uark.edu;


Matt Trentman ( Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, matt.trentman@flbs.umt.edu;


Brittany Hanrahan ( Co-Presenter/Co-Author), USDA Agricultural Research Service, br.hanrahan@gmail.com;


Sheila Christopher ( Co-Presenter/Co-Author), University of Notre Dame, sheila.christopher@nd.edu;


Ursula H. Mahl ( Co-Presenter/Co-Author), University of Notre Dame, umahl@nd.edu;


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6/08/2017  |   10:00 - 10:15   |  306A

Comparing water quality in streams with and without UNGD in their watersheds Unconventional natural gas development (UNGD) has proliferated in the Marcellus Shale region over the past decade. While instances of water contamination have been documented, the question of whether UNGD is associated with widespread impairment of stream water quality remains unanswered. We attempted to address this data gap by measuring water quality parameters (specific conductance, dissolved metal and radium) in streams in southwestern Pennsylvania, where UNGD is prevalent, and western Maryland, where no UNGD has occurred due to a statewide moratorium. The streams were located in adjacent counties and had similar climate, geology and land use other than UNGD. Pennsylvania streams had significantly higher specific conductance and concentrations of As, Ca, K, Mg, and Sr, suggesting that UNGD in the watersheds may be a source of these constituents. However, no significant correlations between watershed UNGD well density and water quality was observed, suggesting that other activities, such as UNGD waste transport and disposal, may affect water quality more than extraction wells do. Future work will focus on the effects of other UNGD-related activities, identifying pathways by which UNGD-related pollution enters streams, and gathering a more comprehensive data set.

Karen Knee (Primary Presenter/Author), American University, knee@american.edu;


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6/08/2017  |   10:15 - 10:30   |  306A

IDENTIFYING HOW TO REDUCE PHOSPHORUS LOADS FROM LAKE ERIE AGRICULTURAL TRIBUTARIES In the Western Lake Erie Basin, the current strategy to reduce phosphorus exports from agricultural lands is to target hotspots in the watershed that are a major source of dissolved reactive P (DRP) runoff. Yet, increasing evidence suggests we instead need a basin-wide management change because a majority of farms are leaking a moderate amount of DRP. For this study, we aimed to clarify which strategy would be most appropriate to effectively decrease the DRP loadings to Lake Erie by monitoring water quality during storm events from 10 subwatersheds of the Sandusky and Maumee Rivers. Our results suggest that chemographs were almost identical across all of the subwatersheds for each of the 5 monitored storm events during 2016 and 2017. Rising and falling limbs were similarly timed and peak DRP concentrations ranged from 0.10 – 0.25 mg/L. Peak concentrations were lower in the subwatershed with remnant forested land during one of the late spring 2016 events. These results imply it’s the common row-crop agricultural practices leading to DRP losses rather than the actions of a few bad actors.

Laura Johnson (Primary Presenter/Author), Heidelberg University, ljohnson@heidelberg.edu;


Jakob Boehler ( Co-Presenter/Co-Author), Heidelberg University, jboehler@heidelberg.edu;


Remegio Confesor ( Co-Presenter/Co-Author), Heidelberg University, rconfeso@heidelberg.edu;


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