5/20/2015  |   10:30 - 10:45   |  103DE

TRENDS IN STREAM BIODIVERSITY RESEARCH SINCE THE RIVER CONTINUUM CONCEPT Lotic environments contain a disproportionate amount of biodiversity given their relatively small proportion of the worldwide landscape. We conducted a systematic literature search directed towards understanding factors that influence biodiversity in lotic habitats, published in 31 major ecological and freshwater science journals from 1981 to 2014. Our goal was to characterize emergent themes in research successes and identify important areas in need of study. We show an overwhelming taxonomic bias favoring studies of macroinvertebrates and fish. While most studies assessed diversity at a local scale, there has been a recent push to investigate regional drivers of beta and gamma diversity. Several factors were consistently found to be important drivers of diversity including local habitat type, hydrologic variables, disturbance, and stream morphometry. Others such as nutrients and chemical variables showed mixed support. Species interactions, dispersal, and evolutionary processes were rarely considered but show promise as fruitful areas for future study. We suggest that researchers should give increased attention to diversity drivers at different scales as well as take advantage of new molecular techniques to address questions regarding organismal diversity in streams.

Brett Tornwall (Primary Presenter/Author), Virginia Tech, bretttornwall@gmail.com;


James Skelton (Co-Presenter/Co-Author), Virginia Tech, skelto3@vt.edu;


Eric Sokol (Co-Presenter/Co-Author), Battelle, National Ecological Observatory Network (NEON), sokole@gmail.com;
NEON Ecologist and Data Scientist

Bryan Brown (Co-Presenter/Co-Author), Virginia Tech, stonefly@vt.edu;

5/20/2015  |   10:45 - 11:00   |  103DE

LEAF LITTER SPECIES AFFECTS THE ACTIVE AQUATIC MICROBIAL COMMUNITY Microbial colonization of leaf litter in headwater streams is known to enhance litter quality for consumers and facilitate nutrient transfer to higher trophic levels; however, little is known about the response of the active microbial community to different litter species. We used stable isotope probing (18O labeled water) to examine how the active aquatic microbial community responded to five litter species with a range of decomposition rates. We explored two hypotheses: (1) the active aquatic microbial community would differ on the five litter species, and (2) the active microbial community would shift through decomposition time. We expected the active component of the microbial community to be relatively more bacterial dominated for fast-decomposing litter species and more fungal dominated for slow-decomposing litter species. We also expected the active community to shift from bacterial dominated to fungal dominated as decomposition progressed. Our study goes beyond traditional litter decomposition studies that document what microbes are associated with various litter types through time by measuring growth rates of microbial species during decomposition.

Alexa Schuettenberg (Primary Presenter/Author), Northern Arizona University, aas322@nau.edu;

5/20/2015  |   11:00 - 11:15   |  103DE

INFLUENCE OF RESOURCE PULSES ON ECOLOGICAL NETWORKS: INSECTS, SALMON AND THEIR MICROBIOMES Resource subsidies are recognized to cross ecosystem boundaries and influence the structure of ecological networks, especially in systems where animals migrate to reproduce and then die – creating ephemeral carrion resources subsidies. This is particularly true in settings with relatively predictable nutrient pulses, such as salmon-bearing streams of Alaska. The objective of this study was to assess the internal microbiome of aquatic insects (Ephemeroptera and Plecoptera); carrion flies (Diptera: Calliphoridae), which have been shown to move carcass nutrients into the riparian forest; and salmon carcasses. Microbial communities were collected from five streams (salmon bearing and non-salmon bearing) and characterized using Illumina MiSeq. There was an increase in unique operational taxonomic units (OTUs) detected in mayfly larvae collected from salmon bearing streams (1,505) compared to non-salmon streams (1,317). Additionally, carrion fly adults had an increase in unique OTUs (5,400) when compared to carrion fly larvae (1,515) developing on salmon carcasses, which suggests important salmon carcass effects on the insect microbiome. These data are foundational in describing resource subsidy-driven network responses to resource pulses with potential bottom-up effects on food web structure.

Jennifer L. Pechal (Primary Presenter/Author), Michigan State University, pechalje@msu.edu;


M. Eric Benbow (Co-Presenter/Co-Author), Michigan State University, benbow@msu.edu;

5/20/2015  |   11:15 - 11:30   |  103DE

EXPERIMENTAL N AND P FERTILIZATION OF FIVE DETRITUS-BASED HEADWATER STREAMS REVEALS EFFECTS OF RESOURCE STOICHIOMETRY ON CONSUMER BIOMASS AND PRODUCTION Altered global N and P availability may influence food webs by causing shifts in the stoichiometric quality (C:N:P ratio) of basal carbon sources. Such shifts can lead to changes in individual growth rates of consumers, thereby altering population and community dynamics. We tested invertebrate responses to microbially modulated changes in detrital stoichiometry by continuously adding N and P at different dissolved N:P ratios (2:1, 8:1, 16:1, 32:1, 128:1) to five detritus-based headwater streams at the Coweeta Hydrologic Laboratory (North Carolina, USA) for two years. Primary consumer and shredder biomass was higher in all five streams during both years (year 1=12%-117%, year 2= 29%-190% among taxa?) of N and P enrichment compared to the year prior to enrichment. Production of Pycnopsyche and Tallaperla increased following enrichment in all five streams by averages of 150% and 1174%, respectively, and decreased with increasing leaf litter C:P (p<0.05), suggesting P limitation of these two common shredders. Release of primary consumers from nutrient limitation, driven by shifts in detrital stoichiometry, may affect community structure and alter material flows to higher trophic levels.

Lee Demi (Primary Presenter/Author), North Carolina State University, mickdemi@yahoo.com;


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


Amy D. Rosemond (Co-Presenter/Co-Author), University of Georgia, rosemond@uga.edu;


John C. Maerz (Co-Presenter/Co-Author), University of Georgia, jcmaerz@uga.edu;


Vlad Gulis (Co-Presenter/Co-Author), Coastal Carolina University, vgulis@coastal.edu;

5/20/2015  |   11:30 - 11:45   |  103DE

INTERACTIONS BETWEEN CONSUMERS AND STREAM FUNCTIONAL PROCESSES: A CASE STUDY FROM THE PACIFIC NORTHWEST Stream function, including stream metabolism, nutrient uptake, and primary production, are influenced by the presence of fish and amphibians through direct and indirect processes. It is unclear, however, how consumer densities of fish and amphibians exert an effect on stream function and whether these processes change among scales. Here we present results from a field experiment conducted in a 4th-order stream in the H.J. Andrews Experimental Forest (Cascade Range, Oregon, USA). We examined the variation in stream functional processes at a reach- and patch-scale by manipulating consumer densities of resident Coastal Cutthroat Trout, Paiute Sculpin, and Coastal Giant Salamander under natural, depleted, and augmented levels over 34 days. By the end of the experiment, the reach with depleted consumer densities showed decreased algal biomass, Chl a, and nutrient uptake capacity. In contrast, nutrient uptake capacity, algal biomass and Chl a increased in the reach where added consumers. Overall, our findings indicate that large aquatic consumers affect stream functional processes and that the magnitude of the change is density-dependent and mediated by changes in the macroinvertebrate community.

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


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