SFS Annual Meeting

5/20/2019  |   11:00 - 11:15   |  250 DE

STREAM FOOD WEB RESPONSE TO THE BENTHIC ALGAE DIDYMOSPHENIA GEMINATA IN AN INLAND TEMPERATE RAINFOREST The response of vertebrate taxa to environmental change is studied for its import to both conservation science and ecological theory. In the Kootenai River basin of Montana, nuisance blooms of Didymosphenia geminata (Didymo) alter the benthic habitat of stream-dwelling macroinvertebrates leading to concerns about food availability to vulnerable Redband Trout (Oncorhynchus mykiss gairdneri) populations. The goal of this study was to determine if Didymo blooms influence the production of secondary consumers and examine underlying trophic mechanisms. Two study streams with similar physical habitats were selected, one with Didymo blooms and one without. Trout were captured bi-monthly, weighed, measured, and lavaged for diet contents. We constructed energy-flow food webs using mark-recapture population estimates, measured trout growth, and diet samples in both streams. During the summer of 2018, Redband Trout production was more than three times higher in the stream with Didymo compared to the reference. Food web analysis revealed that this stark contrast is likely attributable to differing sources and magnitudes of macroinvertebrate energy flow to trout. While preliminary, it appears management of Didymo blooms for the benefit of trout is likely not necessary in similar systems.

Niall Clancy (Primary Presenter/Author), Utah State University, niall.clancy@aggiemail.usu.edu;


Janice Brahney (Co-Presenter/Co-Author), Utah State University, jbrahney@gmail.com;


Phaedra Budy (Co-Presenter/Co-Author), U.S. Geological Survey, Utah Cooperative Fish and Wildlife Research Unit, Utah State University, phaedra.budy@usu.edu;


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5/20/2019  |   11:15 - 11:30   |  250 DE

USE OF TROPHIC BASIS OF PRODUCTION ANALYSES AND STABLE ISOTOPE TRACER ADDITIONS TO QUANTIFY ENERGY FLOW AND NUTRIENT CYCLING IN TROPICAL STREAM FOOD WEBS We quantified energy flow and nutrient cycling in Central American headwater mountain streams over multiple years in order to assess how disease-driven amphibian declines were influencing ecosystem function. These declines resulted in sudden, catastrophic losses of consumer biomass and diversity from the streams. Initial studies suggested detrital pathways dominated energy flow and nutrient cycling in these forested systems, particularly when standard functional group and trophic basis of production approaches were employed. However, autochthonous pathways were significant, particularly in healthy streams with grazing tadpoles. Tracer studies with 15N additions indicated that although coarse detritus accounted for ~83% of N uptake, the grazing pathway accounted for ~87% of N flux from resources in to animals when amphibians were present; N fluxes from detritus to shredders and periphyton to grazers became similar after amphibian declines. Gut content analyses revealed high degrees of omnivory across taxa and functional groups in the streams, reflecting significant complexity in food webs. Gut content analyses also further demonstrated the importance of autochthonous pathways. Collectively, these studies illustrate the importance of using multiple approaches and examining different scales to evaluate energy flow and nutrient cycling patterns in freshwater habitats.

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


Checo Colon-Gaud (Co-Presenter/Co-Author), Georgia Southern University, jccolongaud@georgiasouthern.edu;


Therese Frauendorf (Co-Presenter/Co-Author), University of Victoria, tfrauendorf@gmail.com;


Amanda Rugenski (Co-Presenter/Co-Author), University of Georgia, atrugenski@gmail.com;


Robert O. Hall (Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, bob.hall@flbs.umt.edu;


Walter Dodds (Co-Presenter/Co-Author), Kansas State University, wkdodds@ksu.edu;


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


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5/20/2019  |   11:30 - 11:45   |  250 DE

ENERGY FLOW PATTERNS THROUGH FOOD WEBS IN NEOTROPICAL HEADWATER STREAMS OF THE BRAZILIAN SAVANNA Secondary production is an important element of ecosystem ecology because it quantifies the roles of consumers in energy and nutrient transfers. We estimated production and resource consumption of stream macroinvertebrates, along with stream metabolism and organic matter, in three relatively undisturbed Brazilian savanna headwater streams. We sampled benthic macroinvertebrates and measured reach-scale metabolism from October 2015 to September 2016. Net ecosystem production varied from 8.1 to 35.8 g AFDM m-2 y-1, reflecting heterotrophic conditions. Total secondary production ranged from 11.0 to 13.5 g AFDM m-2 y-1. The shredder and predator functional groups contributed most to production, ranging from 21 - 39% and 20-49% of total production, respectively, and detrital pathways accounted for most energy flow in all streams. Shredders had the greatest mean consumption rates among the collected functional feeding groups, but still only ingested 3.4 to 8.1% of available resources, suggesting that production in these streams is not limited by resource availability. Our study provides the first secondary production and stream metabolism estimates for streams in the Brazilian savanna. Net heterotrophy is not necessarily expected in grassland streams, but detrital pathways dominated energy flow in the systems we examined.

José Mello (Primary Presenter/Author), University of São Paulo, josemello@sc.usp.br;


Daniel Abrahão (Co-Presenter/Co-Author), University of São Paulo, danielshs@usp.br;


Wesley Saltarelli (Co-Presenter/Co-Author), University of São Paulo, wesley.saltarelli@gmail.com;


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


Walter Dodds (Co-Presenter/Co-Author), Kansas State University, wkdodds@ksu.edu;


Davi Cunha (Co-Presenter/Co-Author), University of São Paulo, davig@sc.usp.br;


Juliano Corbi (Co-Presenter/Co-Author), University of São Paulo, julianocorbi@usp.br;


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5/20/2019  |   11:45 - 12:00   |  250 DE

AMINO ACID STABLE ISOTOPES AND HETEROTROPHIC BIOFILMS IN RIVER FOOD WEBS Patterns in essential amino acid (AAESS) d13C values from autotrophs and heterotrophs that can synthesize AAESS de novo may provide enhanced discriminatory power to trace heterotrophic biofilm-derived energy through freshwater food webs. However, no study has characterized producer patterns in AAESS d13C values in adjacent freshwater and terrestrial ecosystems. We analyzed AAESS d13C values of 14 producer taxa, including instream algae and riparian trees from the Rio Grande River and plants from the Chihuahuan Desert in New Mexico (n = 90). Using linear discriminant analysis, we characterized AAESS d13C patterns of producer taxa, yielding a successful reclassification rate of >70%. After confirming the utility of this approach, we completed a series of mesocosm experiments to study the trophic transfer of terrestrial- and heterotrophic biofilm-derived organic matter into aquatic invertebrates. Bulk tissue d13C data reveal freshwater invertebrates consumed terrestrial organic matter, including C4 grasses. Ongoing AAESS d13C analysis will allow us to examine the role of fungi and bacteria in converting terrestrial biomass into more palatable forms of energy. Our work highlights the potential for AAESS d13C analysis to reveal important biological interactions among producers, decomposers, and consumers in freshwater ecosystems.

Emma Elliott Smith (Co-Presenter/Co-Author), University of New Mexico, eaelliot@unm.edu;


Christina Blevins (Co-Presenter/Co-Author), University of New Mexico, cblevins@unm.edu;


Vishwa Patel (Co-Presenter/Co-Author), University of New Mexico, vishwanp20@unm.edu;


Adam Barkalow (Co-Presenter/Co-Author), American Southwest Ichthyological Researchers, LLC, barkalow@unm.edu;


Thomas Turner (Co-Presenter/Co-Author), University of New Mexico, turnert@unm.edu;


Seth Newsome (Co-Presenter/Co-Author), University of New Mexico, newsome@unm.edu;


Alexi Besser (Primary Presenter/Author), University of New Mexico , acbesser@unm.edu;


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5/20/2019  |   12:00 - 12:15   |  250 DE

LEAF TYPE AFFECTS ASSIMILATION OF C AND N BY MACROINVERTEBRATES Leaf litter decomposes predictably with leaf litter traits and the environment. These factors also affect the pathways of element flow. To understand how leaf type affects this pathway, we use a new method for calculating C and N assimilation to macroinvertebrates during decomposition. Using litter from 12 tree species enriched with 13C and 15N, we quantified carbon and nitrogen assimilation from leaves to invertebrate taxa. We incubated twelve leaf species in coarse mesh bags in Oak Creek (AZ). By measuring mass loss, changes in the %C and %N of leaf litter packs, and changes in stable isotope values we estimated C and N loss during decomposition. We also quantified the pathway of C and N transfer to the macroscopic food web by calculating the amount of C and N assimilated by different invertebrate species. We find that element assimilation is a more sensitive metric for detecting differences across leaf types than leaf-associated invertebrate assemblages. Community assemblages did not differ overall by leaf type, while stable isotope values show differential macroinvertebrate assimilation rates across leaf species.

Meghan Schrik (Primary Presenter/Author), Northern Arizona University, ms3398@nau.edu;


Benjamin Koch (Co-Presenter/Co-Author), Northern Arizona University, ben.koch@nau.edu;


Courtney Roush (Co-Presenter/Co-Author), Northern Arizona University, cmr627@nau.edu;


Daniel Cusick (Co-Presenter/Co-Author), Northern Arizona University, dac462@nau.edu;


Jane Marks (Co-Presenter/Co-Author), Northern Arizona University, jane.marks@nau.edu;


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5/20/2019  |   12:15 - 12:30   |  250 DE

REVISITING THE FATE OF DEAD LEAVES IN STREAMS Respiration by stream microorganisms consumes most of the carbon in detritus entering from terrestrial landscapes. A small but vital flux of plant detritus forms the base of the food web and shapes the ecology and biogeochemistry of streams. Traditionally, faster decomposing leaves have been considered to be of higher “quality” suggesting that the entire influence of litter can either be reduced to a one-dimensional relationship between the characteristics of the litter and the performance of a focal organism (or trophic group), or that all organisms and processes respond uniformly. By associating quality with decomposition rate, the “value” of litter increases with its rate of disappearance, regardless of its fate: to higher trophic levels, to sediment organic matter reservoirs, to microbial biomass, to dissolved organic matter, or to the atmosphere as CO2. Moving beyond “quality”, our research tests how litter traits and temperature influence pathways of element flow. Results challenge the commonly held view that slowly decomposing leaves are “poor quality” by demonstrating that some traits that slow decomposition can disproportionately promote C transfer to higher trophic levels, whereas other traits associated with rapidly decomposing litter supports microbial productivity.

Jane Marks (Primary Presenter/Author), Northern Arizona University, jane.marks@nau.edu;


Zacchaeus Compson (Co-Presenter/Co-Author), University of North Texas, zacchaeus.compson@unt.edu;


Adam Siders (Co-Presenter/Co-Author), University of Florida, asiders@ufl.edu;


Courtney Roush (Co-Presenter/Co-Author), Northern Arizona University, cmr627@nau.edu;


Meghan Schrik (Co-Presenter/Co-Author), Northern Arizona University, ms3398@nau.edu;


Benjamin Koch (Co-Presenter/Co-Author), Northern Arizona University, ben.koch@nau.edu;


Adam Wymore (Co-Presenter/Co-Author), University of New Hampshire, adam.wymore@unh.edu;
Dr. Adam Wymore is a Research Assistant Professor at University of New Hampshire.

Steven Thomas (Co-Presenter/Co-Author), University of Alabama, sathomas16@ua.edu;


Alexander Flecker (Co-Presenter/Co-Author), Cornell University, Ithaca, NY, USA, asf3@cornell.edu;


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