5/20/2015  |   10:30 - 10:45   |  102B

EXPERIMENTAL FLOWS INCREASE RESILIENCE OF A REGULATED RIVER TO CATASTROPHIC DISTURBANCE Following adaptive management protocols, the flow-regulated Spol River has experienced multiple, annual experimental flows since 2000. The experimental flows were effective in enhancing the trout fishery as well as causing regime shifts in macroinvertebrates via changes in the habitat template. In late March 2013, the river was disturbed by a loss in flow followed by a major release of fine sediments from the reservoir; i.e. a catastrophic disturbance. The disturbance caused major reductions in fish and macroinvertebrate abundances, indicating low ecosystem resistance. Fish redd numbers were low the first year following the disturbance, although remaining fish were in good condition and recruitment expected to be high in subsequent years. Macroinvertebrate abundances and richness rebounded quickly, reaching predisturbance levels within months. When compared to flow effects from the early floods (year 2000/01), these data suggest that resilience of the river ecosystem to catastrophic disturbance was enhanced. These results highlight the importance of long-term monitoring in assessing the response patterns of regulated rivers to experimental flow release programs.

Chris Robinson (Primary Presenter/Author), Eawag, robinson@eawag.ch;


Johannes Ortlepp (Co-Presenter/Co-Author), Hydra, j.ortlepp@hydra-institute.com;


Thomas Scheurer (Co-Presenter/Co-Author), Swiss Academy of Natural Sciences, thomas.scheurer@scnat.ch;

5/20/2015  |   10:45 - 11:00   |  102B

PERSISTENCE AND STABILITY OF PÁRAMO MACROINVERTEBRATE COMMUNITIES IN STREAMS WITH CONTRASTING NATURAL DISTURBANCE REGIMES Páramo streams are headwaters occupying tropical high altitudes. Conversely to high-altitude temperate streams, páramo streams experience minimal seasonality. Maximum variation in temperature/flow typically occurs on diel rather than annual scales. But similarly in tropical and temperate zones, high-altitude streams are strongly heterogeneous, ranging from groundwater-dominated (stable) to runoff-dominated (unstable environment). We measured conductivity, suspended solids, streambed stability, and temperature/flow regimes of a number of streams on two glaciated volcanoes of the Ecuadorian Andes. We used these data to identify six focal pairs of groundwater/runoff-dominated streams each occupying the same watershed and altitudinal band (~4000 m asl) and are currently monitoring assemblage persistence (taxon presence/absence) and stability (compositional similarity) with monthly macroinvertebrate sampling. Preliminary results suggest that groundwater-dominated streams maintain greater abundance, biomass, diversity, and assemblage stability and persistence than do environmentally unstable runoff-dominated streams. Runoff-dominated assemblages tend to comprise a subset of groundwater-dominated assemblages, although some taxa are found predominantly in runoff streams. Our results will inform biomonitoring for effects of anthropogenic disturbance and will provide insight into the effects of shrinking glaciers, which directly influence runoff-dominated páramo streams.

Debra Finn (Primary Presenter/Author), Missouri State University, dfinn@missouristate.edu;
Associate Professor Stream Ecology

Henrietta Hampel (Co-Presenter/Co-Author), University of Cuenca, hennihampel@gmail.com;


Andrea C. Encalada (Co-Presenter/Co-Author), Instituto BIOSFERA, Universidad San Francisco de Quito, Cumbayá, Ecuador Biológicas y Ambientales, Universidad San Francisco de Quito, Cumbaya, Ecuador, aencalada@usfq.edu.ec;

5/20/2015  |   11:00 - 11:15   |  102B

SPATIAL AND TEMPORAL RESPONSE PATTERNS OF ECOSYSTEM METABOLISM FOLLOWING A CHANNEL ALTERING FLOW EVENT IN PRAIRIE STREAMS Ecosystem processes in intermittent streams systems can be radically altered by channel-disturbing flow events following periods of drought. In order to understand the resiliency of ecosystem function to disturbance events, such as flooding, we measured rates of gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) using continuously logged dissolved O2 and temperature for thirty days following a storm event. Streams are characterized by increasing canopy cover from the headwaters downstream related to burning regimes. The stream with the least dense canopy cover experienced an increase in GPP and ER and remained heterotrophic over the 30 days. Conversely, the stream with the most dense canopy cover was characterized by a gradual decrease in GPP, a decrease in ER, and intermittent periods of autotrophy following the event. However, rates observed for each day at both sites were lower than previous estimates of GPP and ER for those sites at similar times of the year. Despite the immediate influence of flooding on GPP and ER, the effect of the preceding drought conditions may influence limits to recovery.

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


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


Allison Veach (Co-Presenter/Co-Author), Kansas State University, amveach@ksu.edu;


Janine Rüegg (Co-Presenter/Co-Author), University of Lausanne, janine.ruegg@unil.ch;


Matt Trentman (Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, matt.trentman@flbs.umt.edu;

5/20/2015  |   11:15 - 11:30   |  102B

TAKING A BROADER PERSPECTIVE: CATCHMENT-LEVEL WILDFIRE VARIABILITY AND CLIMATE DRIVE RIPARIAN SPIDER RESPONSES IN YOSEMITE NATIONAL PARK, CA Whereas studies of wildfire effects on riparian ecosystems commonly account for variability at the reach scale, broader-scale factors including catchment wildfire and climate may be important to consider, especially in Mediterranean ecosystems characterized by frequent drought and high-severity wildfires. From 2012-2013, we investigated how precipitation and wildfire severity, frequency, and extent effect tetragnathid spider density, mercury (Hg) body loads, trophic position (TP), and reliance on aquatic energy (i.e., derived from benthic algae) at twelve paired reaches. In 2014, we resurveyed these variables at two control reaches and two reaches burned by the Rim Fire in 2013 in a BACIP (paired before-after, control-impact) design. With fire as a reach-scale categorical variable (high vs. low severity), differences in spider responses between pairs and after the Rim Fire were largely insignificant. However, model-selection results using quantitative predictors across both reach and catchment scales indicated that stream macroinvertebrate density, catchment-scale fire frequency, and precipitation were key drivers of spider density and TP. These results provide initial evidence that climate and catchment-scale wildfire variability are important to consider when describing aquatic-terrestrial linkages in Mediterranean ecosystems.

Breeanne K. Jackson (Primary Presenter/Author), The Ohio State University, jackson.1938@osu.edu;


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

5/20/2015  |   11:30 - 11:45   |  102B

THE EFFECT OF URBANIZATION ON THE WEB SPINNING BEHAVIORS OF RIPARIAN ORB-WEAVING SPIDERS Urban streams are known to be heavily impacted by elevated concentrations of nutrients and pollutants. These aquatic ecosystems not only represent a source of energy for riparian consumers, but also a source of contaminants through bioaccumulation from consuming emerging aquatic insects. The web-building behavior of spiders has been used as a bioindicator for environmental contaminants due to changes in web features that can be linked to neurological effects caused by pollutants. In this study we evaluated the effect that urbanization, and its possible associated pollutants, have on the web-building behavior of Tetragnatha boydi. Tetragnatha is a genus of web-building spiders known to be specialists of aquatic ecosystems and are major consumers of aquatic insects. We selected five study sites along an urban gradient within the Río Piedras watershed in San Juan, Puerto Rico. Webs were photographed in the field and we later analyzed web structure variables (e.g., radii length, capture spiral length). We found significant differences for some web parameters among different sites, which indicate possible effects from contaminants associated with differences in surrounding urban density.

Jose Sanchez-Ruiz (Primary Presenter/Author), Montana State University, jas091988@gmail.com;


Sean Kelly (Co-Presenter/Co-Author), University of Puerto Rico-Rio Piedras, spkelly.84@gmail.com;


Alonso Ramírez (Co-Presenter/Co-Author), North Carolina State University, alonso.ramirez@ncsu.edu;

5/20/2015  |   11:45 - 12:00   |  102B

DECREASED TRAIT DIVERSITY OF MACROINVERTEBRATE COMMUNITIES WITH INCREASING IMPERVIOUS SURFACE COVER Macroinvertebrates in streams can be very sensitive to catchment urbanization, particularly to the presence of impervious surfaces. Recent research shows that many macroinvertebrate taxa do not persist in streams in catchments with >2% impervious surface. However, some studies suggest that alpha diversity does not decline with increasing impervious surface coverage. The loss of sensitive macroinvertebrate diversity could result in the loss of taxa with unique traits, yielding a loss of trait diversity from stream communities. We examined the relationship of functional trait richness as well as alpha diversity of the macroinvertebrate community to the percentage of impervious surface near the sampling site for stream reaches sampled by the Maryland Biological Stream Survey between 2007 and 2013. There was no relationship between alpha diversity and impervious surface (P = 0.52), but there was a negative relationship between functional trait richness and impervious surface (P = 0.025), suggesting that increasing percentages of impervious surface can drive declines in trait diversity within a community, even as alpha diversity remains unchanged.

Thomas Barnum (Primary Presenter/Author), USEPA-ORD, tbarnum32@gmail.com;


Meghan Williams (Co-Presenter/Co-Author), Smithsonian Environmental Research Center, williamsme@si.edu;


Donald Weller (Co-Presenter/Co-Author), Smithsonian Environmental Research Center, wellerd@si.edu;