Tuesday, June 6, 2017
09:00 - 10:30

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09:00 - 09:15: / 306A FRESHWATER MUSSELS: A POWERHOUSE OF NITROGEN TRANSFORMATIONS IN STREAMS

6/06/2017  |   09:00 - 09:15   |  306A

FRESHWATER MUSSELS: A POWERHOUSE OF NITROGEN TRANSFORMATIONS IN STREAMS Freshwater mussels (Unionidae) occur in dense aggregations in streams and create hotspots of biogeochemical activity driven by their filter-feeding activity and excretion. Mussel excretion has a high N:P ratio and mussel aggregations can alleviate N limitation of primary production. Mussel N releases could stimulate rates of nitrification and denitrification in sediments because they increase N availability by filtering N from the water column and translocating it to sediments by excretion and egestion. We measured potential denitrification and gross nitrification rates in two rivers located in southeastern Oklahoma. In each river we selected two reaches with dense mussel aggregations and two control reaches located near the mussel beds, but with no or few mussels. Results show that gross nitrification rates are higher and potential denitrification is less N-limited in sediments near mussel beds. Our results provide further evidence that freshwater mussels are important contributors to ecosystem function that create hotspots of biogeochemical processes. Mussel declines could have significant impact on N export to downstream habitats.

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


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


Keith Gido ( Co-Presenter/Co-Author), Kansas State University, kgido@ksu.edu;


Caryn C. Vaughn ( Co-Presenter/Co-Author), University of Oklahoma, cvaughn@ou.edu;


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09:15 - 09:30: / 306A SELF-ORGANIZATION AND THE FUNCTIONING OF STREAMS AND RIVERS

6/06/2017  |   09:15 - 09:30   |  306A

Self-organization and the functioning of streams and rivers The role of self-organization, i.e., the process of individual agents interacting with each other and with local information, has explained regular pattern formation and its ecosystem consequences worldwide. Those patterns occur mostly in otherwise homogeneous terrestrial ecosystems. But does self-organization also influences streams and rivers? In a survey of the nutrient spatial heterogeneity over post-flood succession in a desert stream, we showed that although the environmental template was a dominant driver, the contribution of internal self-organization accounted up to 23% of the effect size of the template for the spatial patterns of the limiting nutrient in the system. In another example, we showed that the spatial distribution of riverine wetlands along the stream channel was simultaneously controlled by physical template and internal feedbacks (self-organization), the relative importance of each varying with hydrological condition of the system. We further develop the concept of self-organization in the context of flowpath, propagation of influence, river continuum and other current concepts, and prescribe a list of questions that can be addressed with this more integrative theoretical framework for freshwater science.

Xiaoli Dong (Primary Presenter/Author), Duke University, xd23@duke.edu;


Jim Heffernan ( Co-Presenter/Co-Author), Duke University, james.heffernan@duke.edu;


Stuart Fisher ( Co-Presenter/Co-Author), Arizona State University, s.fisher@asu.edu;


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09:30 - 09:45: / 306A BIOGEOCHEMICAL CONSEQUENCES OF FORESTED COASTAL WETLAND RETREAT

6/06/2017  |   09:30 - 09:45   |  306A

BIOGEOCHEMICAL CONSEQUENCES OF FORESTED COASTAL WETLAND RETREAT Forested coastal wetlands provide important ecosystem services and are vulnerable to land use and global climate change. There has been significant research on the ability of marshes to keep up with sea level rise and their potential to migrate inland. However, we still lack a clear understanding of the biogeochemical consequences of forested wetland retreat associated with marsh inland migration. Based on our ongoing work and a literature review, we examined rates of sediment accretion and carbon and nitrogen accumulation in forested wetlands and marshes along the Atlantic coast of the US. We found higher and more variable accretion rates in marshes (4.65 ± 5.15 mm/year) than in forested wetlands (2.17 ± 0.83 mm/year). While analyses of C and N accumulation rates are still ongoing, results to date show little difference in C accumulation across wetland states, but higher N accumulation in marshes. Our results suggest that forested coastal wetlands are more vulnerable to sea level rise than marshes, and that accelerated sea level rise will alter the provision of ecosystem services provided by coastal landscapes.

Marcelo Ardon (Primary Presenter/Author), North Carolina State University, mlardons@ncsu.edu;


Gillian Gundersen ( Co-Presenter/Co-Author), North Carolina State University, gcgunder@ncsu.edu;


Matthew Stillwagon ( Co-Presenter/Co-Author), North Carolina State University, mgstillw@ncsu.edu;


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09:45 - 10:00: / 306A CHRONIC NITRATE CONCENTRATIONS ALTER THE STRUCTURE AND FUNCTION OF RIVER BIOFILMS

6/06/2017  |   09:45 - 10:00   |  306A

CHRONIC NITRATE CONCENTRATIONS ALTER THE STRUCTURE AND FUNCTION OF RIVER BIOFILMS We tested the effects increased nutrient availability on the composition and function of river biofilms using laboratory mesocosms. Early and mature stage biofilms from two rivers were incubated in for three weeks at four nitrate loads (0, 0.5, 5 and 25 mg L-1). Early stage biofilms increased growth rates in response to elevated nitrate, but growth of mature biofilms were less responsive to added elevated nitrate. In terms of nutrient acquisition, cell specific maximum uptake rates declined with elevated nitrate treatments, resulting in an essentially constant rate of uptake per unit photosynthesis across a wide range of nitrate concentrations. Nutrient recycling within the biofilm was driven by the level of biofilm development, as biofilms became more self-reliant on internal N cycling with increasing size. Early stage biofilms shifted from a diatom dominated community to a community dominated by green algae and cyanobacteria with increasing nitrate treatment levels. Our results indicate that nitrate loading alters biofilm structure and function and provides a set of mechanisms to explain for the efficacy loss pattern seen in field studies.

Jonathan O'Brien (Primary Presenter/Author), Canisius College, obrien46@canisius.edu;


David Kerling ( Co-Presenter/Co-Author), Canisius College, kerling1@canisius.edu;


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10:00 - 10:15: / 306A GROUNDWATER INPUTS DRIVE LONGITUDINAL PATTERNS OF STREAM CO2 AND CH4 EMISSIONS IN A BOREAL LAKE-STREAM SYSTEM

6/06/2017  |   10:00 - 10:15   |  306A

GROUNDWATER INPUTS DRIVE LONGITUDINAL PATTERNS OF STREAM CO2 AND CH4 EMISSIONS IN A BOREAL LAKE-STREAM SYSTEM Boreal headwater streams emit substantial amounts of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the relative contribution of terrestrial vs. aquatic carbon (C) sources to these emissions remains unclear. We measured biweekly (May-November) CO2 and CH4 fluxes at 50-m intervals along a 1.5 km reach draining a small lake. We also estimated groundwater C inputs, CO2 and CH4 emissions, and stream metabolism across a range of flow conditions. On average, both CO2 and CH4 fluxes decreased markedly during the first 500 m of the reach, but then increased gradually along the following 1000 m. Lake dynamics influenced C emissions near the outlet (0-300 m), whereas terrestrial inputs were the major source of inorganic C lower in the reach. Stream CO2 and CH4 concentrations increased by 24-90% immediately after four groundwater discharge zones, generating hot-spots of C emissions. Our study shows that CO2 and CH4 emissions can change substantially over time and space in response to catchment hydrology and landscape features and suggests that discrete spatial measurements may limit the reliability of C emission estimates from streams.

Anna Lupon (Primary Presenter/Author), Swedish University of Agricultural Sciences, anna.lupon@slu.se;


Ryan Sponseller ( Co-Presenter/Co-Author), Umeå University, ryan.sponseller@emg.umu.se;


Blaize Denfeld ( Co-Presenter/Co-Author), Umeå University, blaize.denfeld@umu.se ;


Jason Leach ( Co-Presenter/Co-Author), Simon Fraser University, jleach@sfu.ca ;


Hjalmar Laudon ( Co-Presenter/Co-Author), Swedish University of Agricultural Sciences, hjalmar.laudon@slu.se;


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10:15 - 10:30: / 306A REGENERATIVE STORMWATER CONVEYANCE (RSC) AS A RESTORATION APPROACH TO NUTRIENT MANAGEMENT MAY DEPEND UPON CARBON QUANTITY, QUALITY, AND SOURCE

6/06/2017  |   10:15 - 10:30   |  306A

Regenerative Stormwater Conveyance (RSC) as a restoration approach to nutrient management may depend upon carbon quantity, quality, and source Regenerative Stormwater Conveyance (RSC) is a restoration approach based on engineering stream channels to incorporate shallow pools, riffles, and grade controls to increase storm water retention and control erosion, and adding a carbon layer to the stream bed (e.g. wood chips) to enhance microbial processes like denitrification. This study examines RSCs effects on nutrients (P and N) and trace metals at two RSC sites 5 and 7 years post-construction, using combined field and lab measurements. Field measurements showed that RSCs usually had lower DO and pH relative to nearby untreated stream reaches, but did not have consistently different P, N, dissolved organic carbon or trace metals (Fe and Mn). No consistent longitudinal change in any water quality parameter was observed across sites. In lab simulation experiments, we observed consistent removal of N and P when sediment was amended with wood chips and leaf litter suggesting that organic matter additions to stream substrates are important drivers of nutrient transformation in RSCs. Nutrient management effectiveness in RSCs depends upon quantity and quality of organic matter added to the stream bed but also as supplied from the adjacent riparian zone.

Shuiwang Duan (Primary Presenter/Author), United States Environmental Protection Agency, sduan@umd.edu;


Paul Mayer ( Co-Presenter/Co-Author), United States Environmental Protection Agency, mayer.paul@epa.gov;


Sujay Kaushal ( Co-Presenter/Co-Author), University of Maryland, skaushal@umd.edu;


Barret Wessel ( Co-Presenter/Co-Author), University of Maryland, bwessel@terpmail.umd.edu ;


Thomas Johnson ( Co-Presenter/Co-Author), United States Environmental Protection Agency, Johnson.Thomas@epa.gov ;


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