5/19/2015  |   15:30 - 15:45   |  102B

THE HYPORHEIC ZONE AS A PRIMARY SOURCE OF RESILIENCE FOR INVERTEBRATE COMMUNITIES IN INTERMITTENT ALLUVIAL RIVERS: EVIDENCE FROM FIELD AND LABORATORY EXPERIMENTS Intermittent rivers, whose flow ceases periodically, represent half of the World’s rivers and are expanding in many areas. Understanding community resilience in such systems is essential to predict the effects of climate change on biodiversity. We hypothesized that the hyporheic zone is the primary source of resilience in alluvial rivers and tested this using i. a natural experiment where community resilience to drying was addressed in 8 rivers, ii. a field experiment where flow and sources of resilience were manipulated, and iii. mesocosm experiments that simulated drying events (increased water temperature and competition). Our results indicate that communities in alluvial rivers are highly resilient to drying; recovery within 3 weeks of rewetting was observed in all rivers after drying events lasting 14-105 days. Preventing recolonization by drift did not alter recovery and circumstantial evidence indicates the hyporheic zone is the main source of resilience in alluvial rivers. Both intraspecific competition and increased temperature triggered the active vertical migration of invertebrates into the hyporheic zone. Altogether, these results indicate the hyporheic zone is essential to maintaining biodiversity in intermittent alluvial rivers.

Ross Vander Vorste (Primary Presenter/Author), Rivers Study Center and Department of Biology - University of Wisconsin La Crosse , vandervorste.ross@gmail.com;


Florian Mermillod-Blondin (Co-Presenter/Co-Author), Irstea-Lyon, blanka;


Florian Malard (Co-Presenter/Co-Author), Irstea-Lyon, blankb;


Thibualt Datry (Co-Presenter/Co-Author), Irstea-Lyon, blankc;

5/19/2015  |   15:45 - 16:00   |  102B

WILDFIRE EFFECTS ON STREAM METABOLISM ACROSS GRADIENTS OF FIRE SEVERITY, WATERSHED GEOMORPHOLOGY, AND SPATIAL SCALE As climate change shifts fire regimes, it is important to understand stream ecosystem responses to fire. How stream metabolism responds remains largely unexplored. We investigated effects of fire severity, watershed geomorphology, and spatial scale on stream ecosystem metabolism in a wilderness watershed of central Idaho. We estimated metabolism using observed dissolved oxygen, temperature, and irradiance to model diel oxygen dynamics in 18 streams varying in fire history and watershed characteristics. We estimated rates of production and respiration, using the P:R ratio as an index of metabolic state. We found that post-fire riparian canopy recovery strongly influences stream metabolic state. Severely burned streams with dense riparian regrowth were heterotrophic, whereas streams with less canopy recovery were autotrophic. Fire’s effect on stream metabolic state was highly mediated by watershed geomorphology, with the strongest long-term changes observable in low-order, steep streams. Effect sizes of predictors on metabolic state were strongest at fine spatial scales. These results indicate that the physical habitat template acts as a filter for aquatic ecosystem response to disturbance, and that context must be explicitly quantified when assessing stream responses.

Emily Davis (Primary Presenter/Author), University of Washington School of Aquatic and Fishery Sciences, davisem@uw.edu;

5/19/2015  |   16:00 - 16:15   |  102B

EFFECTS OF EXPERIMENTAL WATER ABSTRACTION ON INSTREAM PROPERTIES AND INVERTEBRATE ASSEMBLAGES IN TWO LOWLAND STREAMS We used a controlled experiment to evaluate short-term ecosystem responses to flow and water reduction in two lowland streams. Weekly and biweekly samples of both abiotic and biotic stream components were taken both before and after the experimental reduction at the control (upstream) and disturbed (i.e. stagnant and drought) stretches. Flow reduction was complete at both stretches, causing a stronger water reduction in the drought treatment. There was a significant overall effect of disturbance on both stream components in comparison with upstream controls. The responses of the macroinvertebrate communities differed between streams and within stretches. In one stream, invertebrate densities declined relative to the control (up to 74% of the total invertebrates and 91% of the EPT) but only in the stagnant stretch. On the other, there was a strong decline in invertebrate richness in the stagnant stretch (up to 22% and 49% of the EPT, respectively), and on EPT richness (up to 66%) in the drought stretch. Lowland streams are extremely vulnerable to climate change and anthropogenic impacts for their hydrological position and closeness to human populations.

Liliana Garcia (Primary Presenter/Author), Universidade de Vigo, lilizar@uvigo.es;


Isabel Pardo (Co-Presenter/Co-Author), Universidade de Vigo, ipardo@uvigo.es;

5/19/2015  |   16:15 - 16:30   |  102B

CANCELED THE RESPONSE OF MUSSEL POPULATIONS TO THE ADDITION OF SALINE WATER FROM A CLOSED BASIN LAKE INTO THE SHEYENNE RIVER OF NORTH DAKOTA Devils Lake, a closed basin lake, has seen an eight meter rise in water elevation in the last 20 years. To alleviate flooding two outlets were opened to drain water from the lake into the Sheyenne River. This has resulted in higher, constant flow regimes over the summer and fall, and markedly higher levels of ions such as sulfate and chloride in the Sheyenne River. In comparing mussel populations at three sites before and after opening of the outlets, overall mussel populations decreased by an average of 70%. We saw a pattern of greater decreases in certain species and less of an effect on others. The Wabash Pigtoe (Fusconaia flava) saw a decrease ranging from 74% to 99%. This species has gone from the most common species collected in that section of the river to one of the rarer species. In contrast the Black Sandshell (Ligumia recta) has shown a steady population level over the years of sampling. Further biota studies to examine the impact of Devils Lake water on the Sheyenne River are warranted.

Andre DeLorme (Primary Presenter/Author), Department of Science, Valley City State University, andre.delorme@vcsu.edu;


Louis Wieland (Co-Presenter/Co-Author), Department of Science, Valley City State University, louis.wieland@vcsu.edu;

5/19/2015  |   16:30 - 16:45   |  102B

DO ANNUAL WINTER LAKE DRAWDOWNS ALTER THE PHYSICAL HABITAT STRUCTURE AND COMPLEXITY OF SHALLOW LITTORAL ZONES? Annual wintertime water level drawdowns are a common lake and pond management tool implemented across the northeastern US to protect human-built structures and to reduce submerged aquatic vegetation. Despite its widespread use, ecological responses to winter drawdowns are understudied. We quantified physical habitat structure and complexity in the littoral zones of 14 lakes that range in historical drawdown amplitudes (0.3–2.4 m) and two lakes without drawdowns. In each waterbody, we sampled macrophytes, wood, and sediment texture at two 20-m sites adjacent to either forested or developed riparian zones. Our preliminary results indicate that macrophyte biomass and biovolume decreased and substrate heterogeneity increased with amplitude regardless of riparian zone land cover. However, macrophyte structural complexity, small wood density, and leaf litter cover showed no discernible trend. Generally, waterbodies with drawdowns less than 1.5 m varied widely in habitat structure and complexity, suggesting that low-amplitude drawdowns may not consistently alter littoral habitat. Future studies relating metrics of littoral zone physical habitat complexity to biotic assemblages will help determine ecosystem stability and resiliency in response to changes in winter drawdown regimes.

Jason Carmignani (Primary Presenter/Author), The Natural Heritage & Endangered Species Program, Division of Fisheries and Wildlife, MassWildlife, jason.carmignani@state.ma.us ;


Allison Roy (Co-Presenter/Co-Author), U.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts Amherst, aroy@eco.umass.edu;

5/19/2015  |   16:45 - 17:00   |  102B

ARROWHEAD (SAGITTARIA CUNEATA) AS A BIOINDICATOR OF NITROGEN AND PHOSPHORUS FOR PRAIRIE STREAMS Excess nitrogen (N) and phosphorus (P) from agricultural run-off is causing deteriorating ecosystem conditions of prairie streams in southern Manitoba, Canada. The emergent plant, arrowhead (Sagittaria) may be an ideal bioindicator of environmental stress because it is abundant, easily identifiable, and exhibits plastic responses to environmental factors (i.e., water depth, P concentration). To evaluate S. cuneata as a bioindicator, we conducted a 2x2 factorial-design experiment with high or low N and P added to nutrient-poor water (4 treatments) or nutrient-poor sediment (4 treatments), and an unamended control. Plants grown with added sediment nutrients produced, on average, 5.7X and 13.4X more tubers, 3.6X and 8.9X more leaves, and were 20 and 35% taller than plants with added water nutrients or controls, respectively. Leaves were also 2.1X and 2.9X larger for sediment-enriched plants than water-enriched and control plants, respectively, during peak growing season. Our results indicate that arrowhead exhibits plastic responses to sediment nutrients. Further research is continuing to develop and validate S. cuneata as an in-field method of identifying nutrient conditions in prairie streams.

Katherine Standen (Primary Presenter/Author), Canadian Rivers Institute, Department of Biology, University of New Brunswick, k.standen@unb.ca;


Patricia A. Chambers (Co-Presenter/Co-Author), Environment and Climate Change Canada, 867 Lakeshore Rd., Burlington Ontario, Canada, L7R 4A6, patricia.chambers@canada.ca;


Joseph M. Culp (Co-Presenter/Co-Author), Environment Canada & Canadian Rivers Institute, Department of Biology, University of New Brunwsick, P.O. Box 4400, Fredericton, NB, E3B 5A3, jculp@unb.ca;