SFS Annual Meeting

5/21/2019  |   14:00 - 14:15   |  250 AB

SEASONAL DYNAMICS AND CONTROLS ON STREAM DOC TRANSPORT IN THE HIGH-CARBON REGION OF THE PACIFIC COASTAL TEMPERATURE RAINFOREST Streams in British Columbia's humid, organic-rich Pacific Coastal Temperate Rainforest (PCTR) deliver globally significant yields of soil-derived dissolved organic carbon (DOC) to the ocean, which can affect ocean acidification, provide energy to coastal food webs, and off-gas to the atmosphere as CO2. We collected high-frequency data from automated, in-situ fDOM sensors for two years in four PCTR watershed outlets to determine seasonal controls on stream DOC in the PCTR, and to develop a model of subsurface DOC transport and hydrological connectivity. We corrected fDOM sensor output for temperature, turbidity, and inner filter effects to achieve reliable estimates of stream DOC (R2=0.47-0.89). Storm event DOC concentrations primarily exhibited dilution across all seasons with flushing at the end of the dry summer period and the beginning of the wet autumn period, and were significantly correlated with precipitation, 3-day pre-event soil moisture, and watershed area (p < 0.05, R2=0.22). Establishing seasonal controls on stream DOC transport in this high-carbon region has critical implications for coastal ecology and the global carbon cycle, and improves our ability to predict how these systems may be affected by environmental and climatic changes in the future.

Anna Bishop (Primary Presenter/Author), University of Alberta, abishop@ualberta.ca;


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5/21/2019  |   14:15 - 14:30   |  250 AB

BENTHIC MICROBIAL COMMUNITIES RAPIDLY UTILIZE METHANE WHEN EXPOSED TO NATURAL GAS MACRO-SEEPS IN AN INLAND RIVER Methane is usually present in trace quantities in rivers, but natural gas macro-seeps along the Condamine River (Queensland, Australia) elevate water-column methane concentrations to more than 3000 times above concentrations at non-macro-seep reaches. We quantified the spatial and temporal variation in methane oxidation, and the factors mediating this variation, in reaches with and without macro-seeps. Additionally, we performed a sediment translocation experiment to investigate how quickly benthic methanotroph communities become established after the formation of new macro-seeps. Rates of sediment methane oxidation were, on average, 90 times greater near macro-seeps compared to non-macro-seep reaches and generally exceeded rates reported from other aquatic environments. The microbial communities within translocated sediments rapidly responded, with rates of methane oxidation within the translocated sediments matching rates measured at macro-seep reaches within hours of translocation. River discharge was an important determinant of both water-column methane concentration and rates of methane oxidation. We show that methanotroph communities are very active in rivers impacted by natural gas macro-seeps, which indicates that methane may be a prominent energy source in these ecosystems.

Michael Venarsky (Co-Presenter/Co-Author), Australian Rivers Institute, Griffith University, mvenarsky@gmail.com;


Gavin Rees (Co-Presenter/Co-Author), CSIRO Land and Water, gavin.rees@csiro.au;


Mark Kennard (Co-Presenter/Co-Author), Australian Rivers Institute, Griffith University, m.kennard@griffith.edu.au;


Ryan Burrows (Primary Presenter/Author), Australian Rivers Institute, Griffith University, ryan.burrows@unimelb.edu.au;


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5/21/2019  |   14:30 - 14:45   |  250 AB

HIGH-RESOLUTION SPATIO-TEMPORAL DOM DYNAMICS IN WHITE CLAY CREEK, PENNSYLVANIA Chromophoric dissolved organic matter (CDOM) is the fraction of DOM that absorbs light in the ultraviolet-visible spectral region. In the last decades, several absorbance-based metrics have been developed to help quantify dissolved organic carbon (DOC) concentrations, characterize the complex chemical character of DOM, and identify DOM sources and processing in the environment. Using in situ spectrophotometers to measure high-frequency absorbance spectra, we evaluated how DOM dynamics reflected watershed and reach-scale biogeochemical processes in White Clay Creek, a temperate third-order stream in Pennsylvania, USA. In January 2018, three field spectrophotometers (s::can®) were deployed ~1 km apart, and set to collect data at 5-15 minute intervals. Preliminary results of specific UV absorbance (a proxy for aromaticity) and spectral slope (a proxy for molecular weight and photodegradation) showed variation in DOM quality at small spatial (<1 km reaches) and temporal (diurnal, storm event) scales. These appear related to DOM source and transformation during transport, likely through photodegradation. While in situ, high-frequency measurements yielded new insights into stream DOM dynamics, the application of this technology requires several logistical and technical considerations related to power supply, chemical and biological fouling, and data management.

Diana Oviedo-Vargas (Primary Presenter/Author), Stroud Water Research Center, doviedo@stroudcenter.org;


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5/21/2019  |   14:45 - 15:00   |  250 AB

USING HIGH-FREQUENCY SENSORS TO QUANTIFY RIVERINE CARBON AND NUTRIENT BUDGETS ACROSS ARCTIC LANDSCAPES The observed and projected hydrologic intensification across the Arctic region, coupled with pronounced degradation of permafrost, highlights the need to quantify changes in riverine carbon and nutrients budgets as material is increasingly released from the landscape. To this end, using sensors deployed from June-September 2017, we collected high-frequency discharge, nitrate (NO3-) and dissolved organic carbon (DOC) concentrations in three watersheds associated with the Long-Term Ecological Research (LTER) site at Toolik Field Station: the Kuparuk (low-gradient tundra), Oksrukuyik (lake-dominated tundra), and Trevor Creek (high-gradient alpine). We estimated daily and seasonal export as flux (mass/time) and yield (mass/area/time). Generally, DOC and NO3-exports were highest during an unseasonably wet late season (mid-July to August), a result counter to the current paradigm of early-season exports dominating Arctic riverine budgets. Our study revealed that high-frequency water chemistry data provides critical insights that challenge current conventions on the timing and magnitude of nutrient and carbon losses from permafrost-underlain Arctic landscapes. As hydrologic patterns intensify in the Arctic, riverine export of DOC and NO3- during wetter seasons could exacerbate nutrient imbalances in freshwater ecosystems, underscoring the need for continued high-frequency monitoring at high latitudes.

Arial Shogren (Primary Presenter/Author), University of Alabama, ashogren@ua.edu;
Assistant Professor, Department of Biological Sciences, University of Alabama

Jay Zarnetske (Co-Presenter/Co-Author), Department of Earth and Environmental Sciences, Michigan State University, jpz@msu.edu;


Benjamin Abbott (Co-Presenter/Co-Author), Brigham Young University, Department of Plant and Wildlife Sciences, benabbott@byu.edu;


Frances Iannucci (Co-Presenter/Co-Author), University of Alaska Fairbanks, fiannucci@alaska.edu;


William Breck Bowden (Co-Presenter/Co-Author), University of Vermont, breck.bowden@uvm.edu;


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5/21/2019  |   15:00 - 15:15   |  250 AB

FLOODS INCREASE CARBON DIOXIDE AND METHANE FLUXES AND CONCENTRATIONS IN SOUTHERN WISCONSIN AGRICULTURAL STREAMS Streams are often sources of carbon dioxide (CO2) and methane (CH4), particularly in agricultural regions where sediment and organic matter inputs can be substantial. Floods are occurring more often and more intensely in southern Wisconsin, one such agricultural region, due to climate change and few studies have investigated how floods impact stream CO2 and CH4 fluxes and concentrations. We compared concentrations and fluxes of CO2 and CH4 with >30 variables representing in-stream and watershed attributes at 10 sites in mixed agricultural and suburban locations in southern Wisconsin. Floods were often stimuli of CO2 and CH4 fluxes and concentrations. These increases were associated with greater water velocity as well as suspended organic matter. Our results indicate that floods may not always be a disturbance in streams, especially regarding greenhouse gas fluxes and concentrations, and that the increase in floods due to climate change may increase greenhouse gas emissions from streams.

Emily Stanley (Co-Presenter/Co-Author), University of Wisconsin - Madison, ehstanley@wisc.edu;


Sam Blackburn (Primary Presenter/Author), University of Wisconsin - Madison, srblackburn@wisc.edu;


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5/21/2019  |   15:15 - 15:30   |  250 AB

RESOURCE LIMITATION OF AUTOTROPHS AND HETEROTROPHS IN BOREAL FOREST HEADWATER STREAMS Permafrost loss at high latitudes alters watershed flowpaths and is predicted to increase nutrient input to streams. Changes in water chemistry and energy supply can significantly impact stream food webs. Within biofilm communities, autotrophs and heterotrophs compete for inorganic nutrients with the outcome dependent on temperature, light availability, and dissolved organic matter (DOM) lability. In Interior Alaska, sub-catchments are underlain with varying permafrost extents, creating an ideal location to quantify impacts of permafrost thaw and resulting variation in water chemistry. Our objective was to determine how changes in resources influence competition between autotrophs and heterotrophs in boreal stream biofilms. We predicted that with abundant light and labile DOM, inorganic nutrients would dictate autotrophic and heterotrophic activity and biomass, but with low light and recalcitrant DOM, inorganic nutrients would become secondary controls. Through nutrient diffusing substrata deployment and in-lab metabolism incubations, we found that inorganic nutrients and labile carbon limited heterotrophs. Autotrophs were limited by light, but in high light were limited by inorganic nutrients. When labile carbon and inorganic nutrients were available, heterotrophs outcompeted autotrophs for inorganic nutrients, and under elevated light, increases in algal carbon supported higher heterotrophic respiration.

Jeremy B. Jones (Co-Presenter/Co-Author), University of Alaska Fairbanks, jbjonesjr@alaska.edu;


Sophie Weaver (Primary Presenter/Author), University of Alaska Fairbanks, saweaver2@alaska.edu;


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