6/05/2017  |   09:00 - 09:15   |  301A

Stressors in linked aquatic-terrestrial ecosystems: Developing predictive frameworks Over 20 years ago, several seminal publications established the field of spatial food web ecology, greatly increasing our understanding of how movements of nutrients and energy link aquatic and terrestrial ecosystems. Within the last decade, the conceptual underpinning of this field have begun to be applied to studying stressors that affect aquatic systems (e.g., nutrients, contaminants, wildfire, invasive species, and climate change) and their impacts the quantity and quality of resources exported to terrestrial consumers. A next step for this research will be the development of conceptual and quantitative frameworks that can predict the magnitude and types of effects of aquatic stressors have on terrestrial food webs within a spatial context. This talk will give an overview of the session, specifically of the science and tools being developed to help managers and researchers better understand the implications of aquatic stressors on linked aquatic-terrestrial ecosystems, and outline our recent developments in building a predictive framework for understanding the impacts of aquatic contaminants on terrestrial food webs.

Johanna Kraus (Primary Presenter/Author), United States Geological Survey, jkraus@usgs.gov;


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6/05/2017  |   09:15 - 09:30   |  301A

ARE THE EFFECTS OF SUBSIDIES AT THE FRESWHATER-TERRESTRIAL BOUNDARY CONSISTENT ACROSS MULTIPLE ECOSYSTEM BOUNDARIES? One way that stressors affect aquatic-terrestrial linkages is by disrupting the amount of resources and consumers that cross the aquatic-terrestrial boundary. Freshwater ecologists have recognized the importance of these linkages for decades, making the freshwater-terrestrial boundary a potential model system for the study of cross-ecosystem linkages in general. To understand whether the effects of subsidies and consumer fluxes at the freshwater-terrestrial interface are similar in direction and strength at other ecosystem boundaries, we conducted a meta-analysis of 1426 observations from 166 studies. At the freshwater-terrestrial boundary, resource subsidies increased recipient consumer responses (e.g. density or growth) by ~1.5 fold, while consumer fluxes (e.g. dragonfly emergence) reduced prey responses by a similar amount. The indirect effects of these two fluxes differed, attenuating rapidly for consumer fluxes, but not for resource fluxes. Strikingly, these patterns were consistent at each of the other 5 ecosystem boundaries (e.g. marine-terrestrial, freshwater-terrestrial). Our results indicate that the continued study of the effects of stressors on aquatic-terrestrial linkages can not only yield insight into the ecology and management of freshwater-terrestrial ecosystems, but can also yield insight into the effects of stressors on ecosystems in general.

Jeff Wesner (Primary Presenter/Author), University of South Dakota, Jeff.Wesner@usd.edu;


Daniel Allen ( Co-Presenter/Co-Author), The Pennsylvania State University, dca5269@psu.edu;


Lauren Henning ( Co-Presenter/Co-Author), University of South Dakota, lauren.henning@usd.edu;


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6/05/2017  |   09:30 - 09:45   |  301A

CAN WE RELATE TERRESTRIAL-AQUATIC LINKAGES TO HYDROPOWER FLOWS DOWNSTREAM OF A LARGE DAM? The importance of ecological subsidies of energy, nutrients, organism, and other resources from streams and rivers to adjacent terrestrial ecosystems is now well recognized in ecology. However, the extent to which the magnitude and ecological importance of these subsidies are affected by a broad array of anthropogenic activities is only beginning to be understood. In this presentation, we will discuss results from the first year of studying aquatic-terrestrial linkages in the iconic Colorado River ecosystem downstream of Glen Canyon Dam, in Arizona, USA. The goal of this project is to understand whether flow variation due to hydropower generation, which affects local aquatic invertebrate production, propagates out of the river ecosystem and also controls the distribution and production of terrestrial consumers. Specifically, we will address the extent to which terrestrial consumers in river reaches with contrasting levels of diel varial zone water stage fluctuations rely more or less extensively on aquatic invertebrate resources, based on abundance, species richness, and stable isotope-based trophic relationships of terrestrial arthropods.

Jeffrey Muehlbauer (Primary Presenter/Author), University of Alaska Fairbanks, USGS Alaska Cooperative Fish and Wildlife Research Unit, jdmuehlbauer@alaska.edu;


Thomas Quigley ( Co-Presenter/Co-Author), USGS Grand Canyon Monitoring and Research Center, tquigley@usgs.gov;


Ted Kennedy ( Co-Presenter/Co-Author), USGS Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, tkennedy@usgs.gov;


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6/05/2017  |   09:45 - 10:00   |  301A

EFFECTS OF DAM REMOVAL EXTEND TO TERRESTRIAL FOOD WEBS: EVIDENCE FROM A COMMON RIPARIAN CONSUMER The longitudinal influences of dam removal on river ecosystem structure and function are increasingly well described, but impacts on lateral connectivity with adjacent terrestrial systems are unknown. We quantified the effects of lowhead dam removal on a model riparian consumer – spiders of the family Tetragnathidae – before and three years following dam removal. We compared spider density, reliance on aquatically-derived energy (i.e., nutritional subsidies originating from benthic algae), and trophic position among four river reaches: three experimental reaches (upstream unrestored, upstream with channel restoration, downstream of former dam) and one control reach above an intact lowhead dam. Spider densities declined after dam removal system-wide (up to 15.5× lower than pre-dam removal), with the sharpest declines at an upstream-restored reach. In the first two years, spiders were 1.6× more reliant on aquatically-derived energy, yet trophic position decreased without corresponding changes in prey abundance, biomass, or body size. Spiders potentially tracked different basal resource use via chironomid prey, which exhibited shifts in isotopic signatures after dam removal. Our study illustrates that dam removal, an increasingly common river-restoration method, can have significant lateral effects on terrestrial consumers and food webs.

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


David W. P. Manning ( Co-Presenter/Co-Author), The Ohio State University, manning.413@osu.edu;


Robert P. Davis ( Co-Presenter/Co-Author), The Ohio State University, davis.4683@buckeyemail.osu.edu ;


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6/05/2017  |   10:00 - 10:15   |  301A

FORESTS, WOOD, STREAMS, AND SPIDERS: LINGERING EFFECTS OF LAST CENTURY’S STRESSORS ON AQUATIC-RIPARIAN LINKAGES In the Colorado Front Range (USA), disturbance history dictates stream planform. Undisturbed, old-growth streams have multiple channels and large amounts of instream wood and depositional habitat, while disturbed streams (wildfires and logging >100 years ago) are single-channeled with mostly erosional habitat. We tested how these opposing stream states influenced organic matter storage, benthic macroinvertebrate secondary production, emerging aquatic insect flux, and riparian spider biomass. Organic matter storage and macroinvertebrate production did not differ among sites per unit area (m^-2), but values were 2× to 21× higher in undisturbed reaches per unit of stream valley (m^-1 valley) because total stream area was higher in undisturbed reaches. Insect emergence was similar among streams at the area and valley scales. However, insect emergence per meter of stream bank was lower in undisturbed sites because multithread channel reaches had 3× more stream bank per meter of valley than single-channel reaches. Riparian spider biomass followed the same pattern, and we attribute this to the multi-thread channels at undisturbed sites diluting the amount of prey (emerging aquatic insects) reaching the stream bank (riparian spider habitat).

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


David Walters ( Co-Presenter/Co-Author), United States Geological Survey, waltersd@usgs.gov;
Dr. David Walters is a Supervisory Research Ecologist at the Columbia Environmental Research Center. David has been a research ecologist with the USGS since 2008. Prior to that, he was an ecologist for the U.S. EPA, National Exposure Research Laboratory for 6 years. He is a freshwater ecologist with broad training in stream ecology, human impacts on aquatic ecosystems, and ecotoxicology. His current research topics include food webs and contaminant flux, aquatic-riparian linkages, stream fish ecology, land use and climate change, and invasive species.

Ellen Wohl ( Co-Presenter/Co-Author), Colorado State University, Ellen.Wohl@colostate.edu ;


Bridget Livers ( Co-Presenter/Co-Author), Colorado State University, bridgetlivers@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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6/05/2017  |   10:15 - 10:30   |  301A

HOW DOES HEMLOCK WOOLLY ADELGID INVASION AFFECT RIPARIAN CONSUMER TROPHIC DYNAMICS? Riparian invasive species can alter in-stream community structure and function, but their reciprocal effects across the aquatic-terrestrial boundary are less known. We investigated differences in riparian spider trophic dynamics associated with Hemlock Woolly Adelgid (HWA) in 21 Virginia (high invasion severity), West Virginia (moderate invasion), and Ohio (no invasion) headwater stream ravine systems. Isotopic signatures (?13C, ?15N) of Tetragnathidae indicated changes in trophic relationships across HWA invasion severity. Spider ?13C closely tracked emergent aquatic-insect ?13C at non-invaded sites, but this relationship was largely decoupled at sites with moderate invasion severity, suggesting a shift in riparian spider diet associated with HWA invasion. Two-source mixing models indicated that spider reliance on aquatic-derived nutritional subsidies (i.e., originating from periphyton) was slightly lower in sites with moderate to severe invasion. Spider trophic position also decreased in sites with moderate invasion. Both results imply possible shifts in basal-resource availability or changes in emergent-insect community structure following HWA invasion. Our results show that riparian invasion may have reciprocal impacts on cross-boundary energetic fluxes that influence trophic interactions of adjacent terrestrial consumers.

Kristen M. Diesburg (Primary Presenter/Author), The Ohio State University, diesburg.1@osu.edu;


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


David W. P. Manning ( Co-Presenter/Co-Author), The Ohio State University, manning.413@osu.edu;


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