5/23/2016  |   10:30 - 10:45   |  307

ACCOUNTING FOR THE EFFECTS OF COMBINED STRESSORS ON THE BIOLOGICAL STRUCTURE OF MEDITERRANEAN STREAMS The combined effect of hydrological alteration (expressed as its deviation with respect to basal water regime) and the chemical impact caused by the urban sewage inputs in small streams (quantity and relevance of urban effluents) on the stream biological structure was studied in several small Mediterranean streams. Upstream (control) and downstream (impact) sites varied in chemical and hydrological patterns. Impact sites were unable to dilute the chemical inputs (nutrients, DOC or pharmaceutical compounds), but effects were not uniform. Benthic organic matter did not remarkably increase at the impact but the individual body size of invertebrates was higher downstream. The richness of Odonata, Coleoptera, Hemiptera and Diptera increased at these sites at the expense of more sensitive taxa. Filter feeders increased, while shredders and scrapers decreased, and life cycle duration extended at the impact sites. Hydrological alterations and chemical impacts produce complex effects on the stream biological structure.

Sergi Sabater (Primary Presenter/Author), University of Girona and ICRA, sergi.sabater@udg.es;


Vicenç Acuña ( Co-Presenter/Co-Author), Catalan Institute for Water Research (ICRA), vacuna@icra.cat;


Ladislav Mandaric ( Co-Presenter/Co-Author), ICRA, lmandaric@icra.cat;


Jordi-René Mor ( Co-Presenter/Co-Author), University of Barcelona, jrmor@icra.cat;


Isabel Muñoz ( Co-Presenter/Co-Author), University of Barcelona, imunoz@ub.edu;


Olatz Pereda ( Co-Presenter/Co-Author), University of the Basque Country, olatz.pereda@ehu.edu;


Mira Petrovic ( Co-Presenter/Co-Author), ICRA, mpetrovic@icra.cat;


Daniel von Schiller ( Co-Presenter/Co-Author), University of Barcelona, d.vonschiller@ub.edu;


Arturo Elosegi ( Co-Presenter/Co-Author), University of the Basque Country (UPV/EHU), arturo.elosegi@ehu.eus;


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5/23/2016  |   10:45 - 11:00   |  307

SUBSIDY-STRESS UNDER MULTIPLE STRESSORS: INTERACTION BETWEEN WATER SCARCITY AND POINT-SOURCE POLLUTION ON STREAM COMMUNITIES AND ECOSYSTEM FUNCTIONING Urban effluents can subsidize (promote) or stress (reduce) biological activity in stream ecosystems, and water scarcity interact with these impacts as it reduces dilution capacity. We analysed the interaction between water scarcity and point-source pollution by studying reaches upstream and downstream from 13 urban effluents in the Ebro River basin (Spain) under a gradient of temporality. We measured water quality, biofilm, and ecosystem functioning (organic matter breakdown and phosphorus uptake). Our hypotheses were that: i) biological activity would be subsidized by low concentrations of effluent contaminants, stressed by high concentrations; ii) the subsidy-stress response would differ among variables; and iii) water scarcity would reduce the threshold level for stress effects. Study reaches spanned a range of over 500 x in nutrient concentration. Biofilm biomass was significantly higher in impacted reaches, benthic chlorophyll and nutrient uptake significantly lower, but there were no overall differences in breakdown rates. The impact of point-source effluents increased with water scarcity for breakdown rate, but showed weak, decreasing trends with biofilm biomass and chlorophyll. Our results show diverging impacts of urban effluents on different stream attributes.

Arturo Elosegi (Primary Presenter/Author), University of the Basque Country (UPV/EHU), arturo.elosegi@ehu.eus;


Vicenç Acuña ( Co-Presenter/Co-Author), Catalan Institute for Water Research (ICRA), vacuna@icra.cat;


Ladislav Mandaric ( Co-Presenter/Co-Author), ICRA, lmandaric@icra.cat;


Isabel Muñoz ( Co-Presenter/Co-Author), University of Barcelona, imunoz@ub.edu;


Olatz Pereda ( Co-Presenter/Co-Author), University of the Basque Country, olatz.pereda@ehu.eus;


Mira Petrovic ( Co-Presenter/Co-Author), ICRA, mpetrovic@icra.cat;


Jordi-René Mor ( Co-Presenter/Co-Author), University of Barcelona, jrmor@icra.cat;


Daniel von Schiller ( Co-Presenter/Co-Author), University of Barcelona, d.vonschiller@ub.edu;


Sergi Sabater ( Co-Presenter/Co-Author), Catalan Institute for Water Research (ICRA), Girona, Spain, ssabater@icra.cat;


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5/23/2016  |   11:00 - 11:15   |  307

A “COCKTAIL” OF STRESSORS: INDEPENDENT AND JOINT EFFECTS OF ENVIRONMENTAL PERTURBATIONS IN A MIDWESTERN US RIVER The individual and synergistic effects of multiple stressors on river ecosystems has emerged as key challenge for both fluvial science and management. In particular, multiuse river systems – those that flow through a suite of land-use types – are subject to a “cocktail” of environmental stressors. Here, we present evidence from five years of research on the 5th-order Scioto River system of central and southern Ohio, USA. We discuss the relative impacts of multiple environmental perturbations (e.g., land-use change, dams, chemical pollution) on food webs along an urban-rural landscape gradient of the Scioto River. We place particular emphasis on the associations between environmental stressors and aquatic-terrestrial connectivity. We conclude with implications for conservation and management of multiuse rivers.

S. Mažeika Patricio Sulliván (Primary Presenter/Author), The Ohio State University, sullivan.191@osu.edu;


Adam Kautza ( Co-Presenter/Co-Author), University of Minnesota, arkautza@umn.edu ;


Tagwireyi Paradzayi ( Co-Presenter/Co-Author), University of Zimbabwe, tagwireyip@gmail.com ;


Jeremy M. Alberts ( Co-Presenter/Co-Author), University of Cincinnati , albertjy@mail.uc.edu ;


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5/23/2016  |   11:15 - 11:30   |  307

FLOW AND TEMPERATURE AS DRIVERS OF LAKE SUPERIOR TRIBUTARY BIOTA The combination of climate and land use change threatens to significantly alter freshwater ecosystems. We are developing models for understanding the future response of streams to climate and land use change to aid land and water use planning, stream management and restoration, and climate adaptation. We developed hydrologic and stream temperature models to characterize current conditions, and are exploring how study streams may respond to future climate and land cover scenarios. We derived flow metrics and are exploring regional flow-ecology relationships to identify critical stream flow parameters for maintaining good habitat for native fish species such as brook trout. We also will examine the interaction between flow and temperature as they relate to the distribution of fish and invertebrates in these streams. Although flow regime is known to be an important component structuring fish habitat, we found that flow metrics alone are poor predictors; addition of temperature data is expected to improve model predictions. Opportunities and strategies to enhance stream resilience through land and water management are also being identified in cooperation with local, regional, and state-level managers.

Lucinda Johnson (POC,Primary Presenter), Natural Resources Research Institute, University of Minnesota Duluth, ljohnson@d.umn.edu;


William Herb ( Co-Presenter/Co-Author), University of Minnesota, herb003@umn.edu;


Meijun Cai ( Co-Presenter/Co-Author), University of Minnesota Duluth, mcai@d.umn.edu;


Kristen Blann ( Co-Presenter/Co-Author), The Nature Conservancy, kblann@d.umn.edu;


William Bartsch ( Co-Presenter/Co-Author), USEPA MidContinent Ecology Division, bart0497@d.umn.edu ;


John Jereczek ( Co-Presenter/Co-Author), MN Department of Natural Resources, john.jereczek@state.mn.us;


Ralph Garono ( Co-Presenter/Co-Author), University of Minnesota Duluth, rjgarono@d.umn.edu;


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5/23/2016  |   11:30 - 11:45   |  307

HOW DOES ECOSYSTEM STRUCTURE AND FUNCTION RESPOND TO LOW-FLOW CONDITIONS IN AGRICULTURAL STREAMS? Streams in Europe and other regions will experience more frequent and prolonged low-flow events due to climate change in the coming decades, especially the streams impacted by abstraction for drinking water, industry, and irrigation. Low-flow events can alter the physical and biological structure of the stream (e.g., sedimentation and species composition, respectively), which may affect ecosystem function (e.g., whole-stream metabolism, decomposition). To examine the effects of low flow and the associated stressors on stream function, we conducted both a manipulative field study, reducing baseflow discharge 85% in a headwater stream, and experiments in artificial stream channels. Our research demonstrated that the benthic resources shifted toward a higher proportion of fine particulate organic matter and less autotrophic biofilm, which had cascading effects on higher trophic levels. Furthermore, nutrient retention decreased, which, when coupled with less autotrophic biomass, may enhance nutrient export and, in turn, downstream eutrophication during low-flow conditions.

Tenna Riis (Primary Presenter/Author), Aarhus University, Denmark, Tenna.riis@bio.au.dk;


Daniel Graeber ( Co-Presenter/Co-Author), Aarhus University, Denamrk, dgr@bios.au.dk;


Peter S. Levi ( Co-Presenter/Co-Author), Drake University, Des Moines, IA, USA, plevi@wisc.edu;


Annette Baattrup-Pedersen ( Co-Presenter/Co-Author), Aarhus University, Denmark, ABP@bios.au.dk;


Jes J. Rasmussen ( Co-Presenter/Co-Author), Aarhus University, Denmark, jr@bios.au.dk;


Tinna M. Jensen ( Co-Presenter/Co-Author), Aarhus University, Denmark, Tinna_mj@hotmail.com;


Simon L. Rosenhøj ( Co-Presenter/Co-Author), Aarhus University, Denmark, simon-rosenhoej@hotmail.com;


Erika M. Neif ( Co-Presenter/Co-Author), Universidade Estadual de Maringá, Brazil, neif.erika@gmail.com;


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5/23/2016  |   11:45 - 12:00   |  307

INTERACTIVE EFFECTS OF TEMPERATURE AND NITROGEN SUPPLY ON STREAM BIOFILM STRUCTURE AND FUNCTION Climate warming and nitrogen (N) enrichment are both globally important anthropogenic stressors. A growing literature describes their separate influences on the structure and function of stream ecosystems, yet understanding of how temperature and N interact is limited. We conducted a streamside channel experiment that simultaneously manipulated temperature and N and evaluated responses in gross primary production (GPP), ecosystem respiration (ER), nutrient uptake, and N₂-fixation. A previous experiment demonstrated that the temperature dependencies of GPP and ER were stronger than predicted by metabolic theory due to the strong temperature dependence of N₂-fixation. Here, we predicted that N enrichment would alleviate N-limitation, particularly at low temperatures, decreasing the temperature dependency of GPP and ER. As predicted, GPP and ER exhibited temperature dependencies similar to theoretical predictions. We also observed positive nonlinear relationships between metabolic rates and N, suggesting that N-limitation and not the direct effects of temperature on metabolism shaped the temperature dependencies observed in the previous experiment. Our results suggest that the source of N to stream biofilms (N₂-fixation versus dissolved N) may mediate ecosystem responses to warming.

James Hood (POC,Primary Presenter), The Ohio State University, hood.211@osu.edu;


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


Wyatt Cross ( Co-Presenter/Co-Author), Montana State University, wyatt.cross@montana.edu ;


Paula Furey ( Co-Presenter/Co-Author), St. Catherine University, pcfurey@stkate.edu;


Luke Ginger ( Co-Presenter/Co-Author), Field Environmental Instruments, Inc., ging4591@gmail.com ;


Alexander D. Huryn ( Co-Presenter/Co-Author), The University of Alabama, huryn@ua.edu;


Philip Johnson ( Co-Presenter/Co-Author), University of Alabama, Pjohnson@eng.ua.edu;


Delorianne Sander ( Co-Presenter/Co-Author), St.Catherine University, drsander12@gmail.com;


Jill Welter ( Co-Presenter/Co-Author), St. Catherine University, jill.welter@gmail.com;


Jón Ólafsson ( Co-Presenter/Co-Author), Marine and Freshwater Research Institute, josh@veidimal.is;


Gisli Mar Gislason ( Co-Presenter/Co-Author), University of Iceland, gmg@hi.is;


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