5/25/2016  |   15:30 - 15:45   |  311-312

FOOD WEB DYNAMICS ON BRANCHING RIVER NETWORKS River food webs inhabitant watersheds with branching (or dendritic) geometries. We explore how dynamics of species-rich food webs are influenced by the branching nature of river networks. Simulated food webs are constructed using a size-based “niche model” paired with consumer-resource models where vital rates are determined by empirical allometric relationships. Species within the food web are then allowed to disperse among habitat patches that are arranged in a branching structure. Dispersal is modeled to vary among species in a number of ways, including randomly, allometrically, and with competition-colonization tradeoffs. Our models are capable of producing a wide array of dynamics, including stability, dramatic fluctuations, and extinctions. Branching network structure and dispersal mode influences food web stability, yet intrinsic features of the food web have a strong interaction effect with these. Food webs with certain intrinsic structures show greater sensitivity to influence by spatial effects, with specific network geometries and dispersal modes largely playing a secondary role in shaping dynamics. We conclude by discussing the potential of mechanistic food web models to inform management of freshwater systems under global environmental change.

Kurt Anderson (Primary Presenter/Author), University of California, Riverside, kurt.anderson@ucr.edu;


Sean Hayes ( Co-Presenter/Co-Author), University of California, Riverside, sean.hayes@email.ucr.edu;


Jonathan Sarhad ( Co-Presenter/Co-Author), University of California, Riverside, jonathan.sarhad@gmail.com;


Presentation:
This presentation has not yet been uploaded.

5/25/2016  |   15:45 - 16:00   |  311-312

A MECHANISTIC MODEL OF FORAGING AND BIOENERGETICS TO EXPLORE SALMON GROWTH IN PACIFIC NORTHWEST RESERVOIRS DURING DROUGHT In the Pacific Northwest, large dams and their reservoirs alter the life history patterns of anadromous juvenile salmonids by providing conditions which lead to growth rates exceeding those observed in upstream reaches. Here, we expand and combine mechanistic models of visual foraging and bioenergetics to predict growth conditions for juvenile salmon under different management and climatic scenarios. Opportunities for foraging by the fish constrain maximum consumption, and are informed by field measurements of temperature, light and zooplankton abundance across depths. We explore how observed differences in juvenile Chinook Salmon size could be explained by the physical and biological conditions found within three upper Willamette Basin Reservoirs during normal operation and drought years. Our initial results suggest that the distribution of prey resources may induce fish to forage outside of their physiological temperature optima. The effects of drought vary across reservoirs as a function of stratification and mixing. While some reservoir conditions are highly conducive to early summer growth, reservoirs may become ecological traps in late summer, before fall drawdowns that encourage downstream passage through the dams.

Christina A. Murphy (Primary Presenter/Author), U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME, christina.murphy@maine.edu;
things here

Ivan Arismendi ( Co-Presenter/Co-Author), Oregon State University, Department of Fisheries & Wildlife, ivan.arismendi@oregonstate.edu;


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


Presentation:
This presentation has not yet been uploaded.

5/25/2016  |   16:00 - 16:15   |  311-312

EXPLORING LINKAGES IN HEADWATER FOOD WEBS BEFORE AND AFTER FOREST HARVEST USING STRUCTURAL EQUATION AND MECHANISTIC MODELS We examined changes in stream food webs before and after forest harvest using data from the Trask River watershed in Oregon, using structural equation (SEM) and mechanistic models in 12 headwater streams. In this study, the biomass of different trophic levels was quantified for 8 years in 5 reference and 7 harvested watersheds. Data collection began in 2006, five years before forest harvest, and continued until 2015. By examining associations among stream ecosystem components, we simplified our causal diagram of trophic relationships, and then compared the strength of stream trophic linkages in reference watersheds to those in harvested watersheds from both pre- and post-harvest periods using SEM. We used the ecological relationships identified by the SEM to construct mechanistic models, which allowed us to further explore the potential effects of a broader range of riparian disturbances on stream ecosystems. Structural equation and mechanistic models quantify causal pathways of stream physical, chemical and biological responses, and inform our understanding of stream responses to existing and planned riparian guidelines and forest management practices.

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


James Larson ( Co-Presenter/Co-Author), U.S. Geological Survey, jhlarson@usgs.gov;


Brooke Penaluna ( Co-Presenter/Co-Author), PNW Research Station, US Forest Service, brooke.penaluna@oregonstate.edu;


Alba Argerich ( Co-Presenter/Co-Author), University of Missouri, alba.argerich@oregonstate.edu;


Erica Garcia ( Co-Presenter/Co-Author), Charles Darwin University, erica.garcia@cdu.edu.au;


Christina A. Murphy ( Co-Presenter/Co-Author), U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME, christina.murphy@maine.edu;
things here

Scott Cooper ( Co-Presenter/Co-Author), University of California Santa Barbara, scott.cooper@lifesci.ucsb.edu;


Claire Ruffing ( Co-Presenter/Co-Author), University of British Columbia, ruffing.cathcart@ubc.ca;


Daniel Allen ( Co-Presenter/Co-Author), Arizona State University, Daniel.C.Allen@asu.edu;


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


Matt Whiles ( Co-Presenter/Co-Author), University of Florida, mwhiles@ufl.edu;


Presentation:
This presentation has not yet been uploaded.

5/25/2016  |   16:15 - 16:30   |  311-312

STREAM COMMUNITY RESPONSES TO RIVER OTTER REINTRODUCTIONS IN ILLINOIS River otter (Lontra canadensis) are an apex predator that can exert top-down control in riparian-stream ecosystems. We used structural equation models to assess if recovering otter populations in Illinois are affecting stream communities. We compared fish and macroinvertebrate communities from before (1982-1995) and after (2005-2013) reintroduction of river otter, which occurred in 1994–1996. Fish and macroinvertebrate data for 42 sites located throughout 6 major watersheds in southern Illinois (25,550 km²) were obtained from state agencies. Otter sign data (e.g., tracks and scat) were collected during 2012-2014. We used the proportion of times that otter sign was observed as an index for otter use at each site. We used AIC to compare 6 models of the stream community. The inclusion of river otter use at sites did not improve a simple stream community model (ΔAIC=14.14). Additionally, change in percent forest within the watershed did not improve the model (ΔAIC=202.94). Overall, our results indicated that any changes in stream communities over time were not due to river otter presence or change in forest cover.

Angela Holland (Primary Presenter/Author), Southern Illinois University Carbondale, amjackson@siu.edu;


Eric Hellgren ( Co-Presenter/Co-Author), University of Florida, hellgren@ufl.edu;


Matt Whiles ( Co-Presenter/Co-Author), University of Florida, mwhiles@ufl.edu;


Presentation:
This presentation has not yet been uploaded.

5/25/2016  |   16:30 - 16:45   |  311-312

TOWARDS UNDERSTANDING DRIVERS OF COMMUNITY-LEVEL INVERTEBRATE PRODUCTION USING STRUCTURAL EQUATION MODELING Invertebrate secondary production is an important flux in freshwater ecosystems that links populations to ecosystem processes and underpins some of the ecosystem services that humans depend on (e.g., fisheries production). Annual estimates of invertebrate community production are relatively uncommon, owing to the time and effort involved in field sampling and laboratory processing. In the past few decades, however, a significant number of researchers have ‘taken the plunge’, allowing for a more quantitative assessment of the key drivers of whole-community production. We build on previous efforts to compile and analyze all published estimates of invertebrate community production in streams and rivers (n > 200), as well as important environmental factors that are hypothesized to influence production (e.g., temperature, flow metrics, nutrient concentrations, substratum type, organic matter resources). We are using structural equation modeling to help conceptualize and quantify direct and indirect drivers of community-level secondary production. Initial results suggest that factors predicting secondary production at the community level differ from, and are more idiosyncratic than, those influencing production at the individual and population levels.

Wyatt Cross (POC,Primary Presenter), Montana State University, wyatt.cross@montana.edu ;


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


Arthur Benke ( Co-Presenter/Co-Author), University of Alabama, abenke@ua.edu;


Thomas Brey ( Co-Presenter/Co-Author), Alfred Wegener Institute, thomas.brey@awi.de;


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


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


Daniel McGarvey ( Co-Presenter/Co-Author), Center for Environmental Studies, Virginia Commonwealth University, djmcgarvey@vcu.edu;


Christina A. Murphy ( Co-Presenter/Co-Author), U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME, christina.murphy@maine.edu;
things here

Christopher Patrick ( Co-Presenter/Co-Author), Virginia Institute of Marine Science (VIMS), cpatrick@vims.edu;


Claire Ruffing ( Co-Presenter/Co-Author), University of British Columbia, ruffing.cathcart@ubc.ca;


Parsa Saffarinia ( Co-Presenter/Co-Author), University of California, Riverside, psaff001@ucr.edu;


Matt Whiles ( Co-Presenter/Co-Author), University of Florida, mwhiles@ufl.edu;


Guy Woodward ( Co-Presenter/Co-Author), Imperial College London, gu.woodward@imperial.ac.uk;


Presentation:
This presentation has not yet been uploaded.

5/25/2016  |   16:45 - 17:00   |  311-312

CHALLENGES AND OPPORTUNITIES FOR ADVANCING FOOD WEB THEORY AND ANALYSIS IN STREAM ECOSYSTEMS THROUGH MODELING Stream ecosystems are threatened by many human disturbances, including climate and land use changes, and rapid biodiversity loss, but it is unclear how food web structure and dynamics will respond to these stressors. Although knowledge of trophic dynamics in freshwater ecosystems is based primarily on empirical data, recent advances in mechanistic and statistical modeling provide new opportunities for rigorously describing ecological systems and forecasting their responses to perturbations. We review the challenges for advancing trophic theory and analysis in stream ecology and discuss the application of current modeling approaches to examine the effects of disturbances on trophic dynamics. We then present a case study evaluating the effects of invasive species on stream community dynamics. More specifically, our approach uses mechanistic modeling to predict the effects of non-native species across functional feeding groups. Resulting predictions then inform causal hypotheses for structural equation modeling of community data from the National Rivers and Streams Assessment. Our approach highlights the utility of coupled modeling frameworks for generating predictions and testing hypotheses regarding the effects of human perturbations on complex ecosystems.

Claire Ruffing (Primary Presenter/Author), University of British Columbia, ruffing.cathcart@ubc.ca;


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


Matt Whiles ( Co-Presenter/Co-Author), University of Florida, mwhiles@ufl.edu;


Daniel Allen ( Co-Presenter/Co-Author), Arizona State University, Daniel.C.Allen@asu.edu;


Kurt Anderson ( Co-Presenter/Co-Author), University of California, Riverside, kurt.anderson@ucr.edu;


Alba Argerich ( Co-Presenter/Co-Author), University of Missouri, alba.argerich@oregonstate.edu;


Ana Chara-Serna ( Co-Presenter/Co-Author), Department of Forest and Conservation Sciences, University of British Columbia, ana.chara@forestry.ubc.ca;


Scott Cooper ( Co-Presenter/Co-Author), University of California Santa Barbara, scott.cooper@lifesci.ucsb.edu;


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


Nika Galic ( Co-Presenter/Co-Author), University of Minnesota, ngalic@umn.edu;


Erica Garcia ( Co-Presenter/Co-Author), Charles Darwin University, erica.garcia@cdu.edu.au;


James Grace ( Co-Presenter/Co-Author), U.S. Geological Survey, gracej@usgs.gov ;


Angela Holland ( Co-Presenter/Co-Author), Southern Illinois University Carbondale, amjackson@siu.edu;


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


James Larson ( Co-Presenter/Co-Author), U.S. Geological Survey, jhlarson@usgs.gov;


Daniel McGarvey ( Co-Presenter/Co-Author), Center for Environmental Studies, Virginia Commonwealth University, djmcgarvey@vcu.edu;


Christina A. Murphy ( Co-Presenter/Co-Author), U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME, christina.murphy@maine.edu;
things here

Roger Nisbet ( Co-Presenter/Co-Author), University of California, Santa Barbara, Roger.nisbet@lifesci.ucsb.edu;


Christopher Patrick ( Co-Presenter/Co-Author), Virginia Institute of Marine Science (VIMS), cpatrick@vims.edu;


Brooke Penaluna ( Co-Presenter/Co-Author), PNW Research Station, US Forest Service, brooke.penaluna@oregonstate.edu;


Parsa Saffarinia ( Co-Presenter/Co-Author), University of California, Riverside, psaff001@ucr.edu;


Presentation:
This presentation has not yet been uploaded.