6/08/2017  |   09:00 - 09:15   |  306B

CONTRIBUTIONS OF FISH AND MUSSEL COMMUNITIES TO NUTRIENT DYNAMICS Mussels and fish are known to generate nutrient hotspots, but whether aggregations of these two consumer groups overlap and interact to influence nutrient dynamics remains unexplored. Mussel beds create stable, long-term hotspots that may attract fishes by providing resource subsidies. Hence, we asked whether fish biomass is greater at stream reaches with mussel beds compared to reaches without mussel beds. Within mussel beds, we measured fish and mussel biomass and excretion rates to determine whether there are differences in their contribution to nutrient cycling. Fish biomass was homogeneously distributed in mussel and non-mussel reaches. Within mussel reaches, mussel biomass exceeded fish biomass. Consequently, mussel areal excretion rates were higher than those of fish. However, N:P excreted by fishes was lower than that of mussels. Future efforts will evaluate the more diffuse occurrences of fishes compared to the aggregated occurrences of mussels towards nutrient hotspots and ecosystem function.

Garrett Hopper (Primary Presenter/Author), Kansas State University, ghopper@ksu.edu;


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


Caryn C. Vaughn ( Co-Presenter/Co-Author), University of Oklahoma, carynvaughn@gmail;


Thomas Parr ( Co-Presenter/Co-Author), University of Oklahoma, Thomas.parr@ou.edu;


Kiza Gates ( Co-Presenter/Co-Author), Washington Department of Fish and Wildlife, kizagates@gmail.com;


Carla L. Atkinson ( Co-Presenter/Co-Author), University of Alabama, carlalatkinson@gmail.com;


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6/08/2017  |   09:30 - 09:45   |  306B

Towards a Meta-Ecosystem Perspective of Aquatic-Terrestrial Linkages A "meta-ecosystem" as a set of spatially isolated ecosystems that exchange energy, materials, and organisms. Reciprocal (bi-directional) exchanges of resources and consumers between aquatic and terrestrial ecosystems make them a model for studying meta-ecosystems. A central feature of meta-ecosystems are feedbacks produced bi-directional resource flows. But currently we typically study linkages between aquatic and terrestrial ecosystems uni-directionally, and only focus on one linkage at a time. Here we argue that new insights can be gained by explicitly integrating feedbacks, and multiple linkage types, into empirical studies of aquatic-terrestrial linkages. We present the results of a theoretical meta-ecosystem model with two three-trophic level ecosystems, one approximating a high-energy flux system ("aquatic") and another approximating a low-energy flux system ("terrestrial"). We then vary and examine the effects of consumer fluxes and resource fluxes from one system to the other, with and without allowing feedbacks between each system to occur, and explore their consequences on meta-ecosystem dynamics. We find that when we allow feedbacks to occur, and when multiple linkages are considered, the effects of resource additions and consumer removals lead to different outcomes.

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


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


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


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


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


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


Christina A. Murphy ( Co-Presenter/Co-Author), U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME, christina.murphy@maine.edu;
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Brooke Penaluna ( Co-Presenter/Co-Author), PNW Research Station, US Forest Service, brooke.penaluna@oregonstate.edu;


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


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


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6/08/2017  |   09:45 - 10:00   |  306B

EXPERIMENTAL WHOLE-ECOSYSTEM WARMING ALTERS ENERGY PATHWAYS BUT NOT TOTAL ENERGY FLOW IN A STREAM FOOD WEB Climate warming will alter flows of energy through food webs due to the critical influence of temperature on physiological rates, community structure, and trophic dynamics. However, few studies have experimentally assessed the influence of warming on energy flux and food web dynamics in intact communities. Here we test how warming affects energy flux and the trophic basis of production in a natural food web by experimentally heating a stream reach by ~4°C for two years. Experimental warming led to increases in estimated metabolic demand by the invertebrate community, but no change in measured production. Consequently, estimated total resource consumption based on production did not increase. Regardless of discrepancies between estimated demand and consumption, warming shifted organic matter flows within the food web (e.g., consumption of amorphous detritus decreased, while that of filamentous algae increased). Elevated metabolic demand without increases in total resource consumption was likely driven by increases in resource quality, taxon-level variation in responses to warming, or differences in the temperature dependences of metabolism and ingestion that are not accounted for by production-based analyses. Overall, our results underscore the challenges of predicting temperature effects on complex food web processes.

Daniel Nelson (Primary Presenter/Author), University of Oklahoma, dnelson12@crimson.ua.edu;


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


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


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


James Hood ( Co-Presenter/Co-Author), The Ohio State University, hood.211@osu.edu;


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


James Junker ( Co-Presenter/Co-Author), University of North Texas, james.junker1@gmail.com;


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


Jón S. Ólafsson ( Co-Presenter/Co-Author), Marine and Freshwater Research Institute, Iceland, jon.s.olafsson@hafogvatn.is;


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6/08/2017  |   10:00 - 10:15   |  306B

AGGREGATIONS OF MUSSEL AND FISH CONSUMERS INTERACT TO INFLUENCE RESOURCE HETEROGENEITY AND FLUXES IN STREAMS. Aggregations of consumers can create local patches of nutrient regeneration and material flux (biogeochemical hotspots). Mobile, shorter-lived fishes and localized, longer-lived mussels generate overlapping hotspots in streams. We examined how the interaction of these hotspots influences stream function by sampling resource pools (mussels, fishes, macroinvertebrates, seston, periphyton, nutrients) and fluxes (excretion/egestion rates, nutrient uptake, denitrification/nitrification rates, and nutrient limitation) in river reaches with and without large mussel aggregations. We also conducted a mesocosm experiment where we tested how the presence or absence of a grazing minnow influences ecosystem properties in the presence of mussel beds. To date field studies have shown that mussels alleviate nitrogen limitation and that benthic organic matter is consistently higher in non-mussel reaches. In mesocosms, fish distribute nutrients homogenously, whereas nutrients concentrate downstream of mussel patches where fish are absent. In addition, where mussels and fish overlap, benthic algal standing crops are relatively stable over time and benthic organic matter is lower, whereas algal standing crops fluctuate over time without fish and organic matter is higher. Future work will examine how hydrologic variation influences these interactions.

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


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


Thomas Parr ( Co-Presenter/Co-Author), University of Oklahoma, Thomas.parr@ou.edu;


Kiza Gates ( Co-Presenter/Co-Author), Washington Department of Fish and Wildlife, kizagates@gmail.com;


Traci DuBose ( Co-Presenter/Co-Author), University of Oklahoma, tracipopejoy@ou.edu;


Garrett Hopper ( Co-Presenter/Co-Author), Kansas State University, ghopper@ksu.edu;


Carla L. Atkinson ( Co-Presenter/Co-Author), University of Alabama, carlalatkinson@gmail.com;


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6/08/2017  |   10:15 - 10:30   |  306B

SHADE AND GRAZING, NOT PHOSPHORUS, LIMIT ALGAL BIOMASS IN TROPICAL BRAZILIAN ATLANTIC FOREST (MG) STREAMS. We manipulated nutrients grazers and predators in enclosures implanted in a shaded and a partially open site in an Atlantic Brazilian forest stream to address the question of whether these streams are top-down limited by grazers or bottom-up limited by light and nutrients. Algal biomass was low (56 to 162 µg chl-a /m ²). A 58% increase in light resulted in 2.2 fold increase in algal biomass (128 vs. 343 µg chl-a /m ² ) and 4 fould increase in primary production (from 10 to 40 mg C m ² day ^-1 ). Nutrient (P) addition did not stimulate algal standing crop. Helicopsyche grazing caused a 49 to 59% algal biomass reduction when compared with treatments with no grazers. The presence of Anacroneuria sp. (predator) did not reduce feeding by Helicopsyche. Substrates exposed to shade and semi-open sites differed in the dominance of some algal taxa. We conclude that (1) shade and herbivory control algal biomass and in these Atlantic forest streams; and (2) small changes in the light entering the streams can have profound implications in primary producers.

Manuel Graça (POC,Primary Presenter), MARE, University of Coimbra, Portugal , mgraca@ci.uc.pt;


José Barbosa ( Co-Presenter/Co-Author), Universidade Estadual da Paraíba, Campina Grande, PB, Brazil, ethambarbosa@hotmail.com;


Tatiany Chaves ( Co-Presenter/Co-Author), Universidade Estadual da Paraíba, Campina Grande, PB, Brazil, ethambarbosa@gmail.com;


Kele Ferminiano ( Co-Presenter/Co-Author), Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, kelerocha@gmail.com;


Juliana França ( Co-Presenter/Co-Author), Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, jsfranca@yahoo.com.br;


José Júnior ( Co-Presenter/Co-Author), University of Brasíla, Brasília, DF, Brazil, jfjunior@unb.br;


Marcos Callisto ( Co-Presenter/Co-Author), Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, callistom@ufmg.br ;


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