SFS Annual Meeting

Sharmin Siddiqui (Co-Presenter/Co-Author)
University of Florida, sharsid94@ufl.edu;

Thiago Couto (Co-Presenter/Co-Author)
Florida International University, tbelisar@fiu.edu;

Xavier Zapata-Rios (Co-Presenter/Co-Author)
Escuela Politécnica Nacional, xavier.zapata@epn.edu.ec;

Elizabeth P Anderson (Co-Presenter/Co-Author)
Florida International University, epanders@fiu.edu;

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;

Claire Beveridge (Primary Presenter/Author)
Florida International University, cbeverid@fiu.edu;

Abstract: As dam construction booms in the Andean headwaters of the Amazon River, the fragmentation of Andean-Amazon streams poses increasing threats to downstream social and ecological systems. These rich systems highly depend on Andean freshwater exports and the sediment and nutrients they carry. In the face of these threats, freshwater conservation planning and management is challenging due in part to the lack of a consistent baseline (i.e., pre-dam) Andes-Amazon hydrologic budget that is reliable and functional for water managers. Responding to this practical need, we present a comprehensive baseline Andes-Amazon hydrologic budget deduced from observed and modeled streamflow data. The budget is resolved for multiple sub-basin levels and contains metrics that support planning and management (e.g., flood frequency). We also highlight the influence of glaciers and páramos on streamflow, which have minimal influence on the total discharge of the Amazon River but are important buffers to Amazon headwaters flows during dry periods. The hydrologic budget will be made available as a geodatabase and is consistent with other products (e.g., sediment budget) being developed with an interdisciplinary working group to support basin-wide freshwater conservation efforts.

Kris Taniguchi-Quan (Primary Presenter/Author)
Southern California Coastal Water Research Project, kristinetq@sccwrp.org;

Katherine Irving (Co-Presenter/Co-Author)
Southern California Coastal Water Research Project, katiei@sccwrp.org;

Eric Stein (Co-Presenter/Co-Author)
Southern California Coastal Water Research Project, erics@sccwrp.org;

Rich Wildman (Co-Presenter/Co-Author)
Geosyntec Consultants, rwildman@geosyntec.com;

Aaron Poresky (Co-Presenter/Co-Author)
Geosyntec Consultants, aporesky@geosyntec.com;

Amanda Aprahamian (Co-Presenter/Co-Author)
County of Orange - OC Public Works, Amanda.Aprahamian@ocpw.ocgov.com;

Cindy Rivers (Co-Presenter/Co-Author)
County of Orange - OC Public Works, cindy.rivers@ocpw.ocgov.com;

Grant Sharp (Co-Presenter/Co-Author)
County of Orange - OC Public Works, Grant.Sharp@ocpw.ocgov.com;

Abstract: Flow alteration is a pervasive issue across highly urbanized watersheds that can impact the physical and biological condition of streams. However, prioritizing where to focus flow management actions can be a challenge when alteration is widespread across broad spatial scales and multiple aspects of the flow regime. A functional flows approach focuses on identifying and managing for discrete aspects of the annual hydrograph that are associated with ecological, geomorphic, or biogeochemical processes in order to preserve the key hydrologic signals upon which native biological communities depend on. Using a functional flows approach, we developed a decision support process that uses a combination of hydrologic models and established ecological thresholds based on bioassessment indices to help managers optimize where to prioritize watershed restoration and flow management efforts. A series of adaptable decisions are explored in the context of watershed prioritization including how many and which flow components constitute alteration, the frequency and degree of alteration that are biologically-important, and the spatial patterns of alteration. We illustrate the utility of this approach on prioritizing subbasins for flow management in a highly urbanized watershed in southern California.

Stephanie Carlson (Co-Presenter/Co-Author)
Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, U.S., smcarlson@berkeley.edu;

James Hobbs (Co-Presenter/Co-Author)
California Department of Fish and Wildlife, james.hobbs@wildlife.ca.gov;

Albert Ruhi (Co-Presenter/Co-Author)
Department of Environmental Science, Policy, and Management, University of California, Berkeley, albert.ruhi@berkeley.edu;

Denise Colombano (Primary Presenter/Author)
University of California Berkeley, denise.colombano@berkeley.edu;

Abstract: In the San Francisco Estuary, the relative magnitude of marine vs. freshwater influences on ecosystem dynamics varies with hydroclimate patterns. Quantitatively scaling species-level responses to community-level stability remains a challenge due to variation in estuarine monitoring methodology. We applied a state-space approach to model juvenile fish community dynamics and the influence of hydroclimatic fluctuations and trends to answer the following questions: How does juvenile fish abundance vary along the estuarine gradient over time? How do watershed hydrology and ocean conditions explain interannual variation in species abundance? We examined 20 common age-0 fishes sampled at 35 core stations from 1980 to 2019. Overall, mean annual river flows best explained community-wide abundance fluctuations. Notably, anadromous species responded similarly, with significant positive responses to flow (‘freshening’) in the lower estuary, whereas marine-dependent species displayed the opposite pattern, with significant negative responses to flow (‘salinity intrusion’) in the upper estuary. Here we explore the life-history mechanisms that may confer response diversity--and thus temporal stability--at the community level. This work may advance the notion that directional trends, fluctuations, and extremes in hydroclimate will continue to reshape estuarine fish communities in the future.

Nuria Bonada (Co-Presenter/Co-Author)
University of Barcelona, bonada@ub.edu;

Miguel Cañedo-Argüelles (Co-Presenter/Co-Author)
University of Barcelona, mcanedo.fem@gmail.com;

José Mª Fernández-Calero (Primary Presenter/Author)
University of Barcelona, josefernandezcalero@ub.edu;

Abstract: According to the metacommunity theory, environmental filtering should prevail over spatial factors at small spatial scales due to low dispersal limitations. However, Mediterranean streams have wide hydrological changes that affect network connectivity and aquatic metacommunities. For example, in Mediterranean stream networks, sites that are close in space can be fairly isolated from each other due to seasonal drying. Here we studied 25 sites belonging to 7 pristine and small stream networks in northeast of Spain. We hypothesized that hydrological connectivity could play a significant role in explaining metacommunity assembly at very low spatial scales, especially for obligate aquatic taxa. We focused on aquatic macroinvertebrates due to their abundance, diversity and wide range of dispersal strategies. We measured flow permanence using data-loggers and local habitat variables, and calculated hydrological connectivity using network analysis. In this talk we will present our preliminary results and discuss the importance of hydrological connectivity for regional biodiversity in stream networks with recurrent drying.

Katherine Irving (Primary Presenter/Author)
Southern California Coastal Water Research Project, katiei@sccwrp.org;

Kris Taniguchi-Quan (Co-Presenter/Co-Author)
Southern California Coastal Water Research Project, kristinetq@sccwrp.org;

Ryan Peek (Co-Presenter/Co-Author)
University of California, Davis, rapeek@ucdavis.edu;

Eric Stein (Co-Presenter/Co-Author)
Southern California Coastal Water Research Project, erics@sccwrp.org;

Abstract: Flow alteration is a pervasive source of habitat alteration that is of management concern worldwide. A key challenge in managing flow alteration is determining the level and pattern of alteration that is associated with impairment of biological communities. Bioassessment tools based on primary producers and consumers have been developed as useful indicators of stream health and for developing flow management targets. However, several decisions must be made to allow these tools to inform flow target development. Specifically, determining an index value threshold, and a threshold of probability that predicts the likelihood of achieving “healthy” biology, influence confidence in usability and implementation of the resulting tool. Using a functional flow approach that relates ecologically important aspects of flow regime to biological community response, we performed a flow-ecology analysis using regional bioassessment data, through which we determined biological alteration and flow targets for a highly urbanized watershed. We applied and compared combinations of alternative thresholds to assess the sensitivity of flow target outcome and uncertainty. We will present the outcomes of this analysis and discuss the implications of the threshold decisions made.

Brian Gill (Primary Presenter/Author)
School of Natural Resources and the Environment, The University of Arizona, briangill@email.arizona.edu;

Anthony Sanabria (Co-Presenter/Co-Author)
University of California, Berkeley, asanabria@oakland.edu;

Miranda Gonzales (Co-Presenter/Co-Author)
University of California, Berkeley, mgon23@berkeley.edu;

Stephanie Carlson (Co-Presenter/Co-Author)
Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, U.S., smcarlson@berkeley.edu;

Michael Bogan (Co-Presenter/Co-Author)
School of Natural Resources and the Environment, The University of Arizona, mbogan@email.arizona.edu;

Abstract: In streams, drying events influence the structure of aquatic communities. As species cope with flow intermittency, proximity to perennial refuges elsewhere in the stream network may also be important in determining local community structure. To examine how intermittency and distance to refuges affect stream biota, we monitored streamflow and surveyed aquatic macroinvertebrates and vertebrates across two years in 11 coastal stream reaches at Pine Gulch in Point Reyes National Seashore and 16 inland stream reaches at Chalone Creek in Pinnacles National Park, California. We determined the number of days flowing prior to sampling, the percentage of days per year with flow, and the number of times per year each reach dried. We also measured the distance of each intermittent reach to perennial refuges. We identified 299 macroinvertebrate and 10 vertebrate taxa across the two basins. Reaches in Pine Gulch basin had higher species richness but lower densities than those in Chalone Creek. Perennial and intermittent reaches had distinct faunas, and increased intermittency and distance to refuges were negatively associated with taxon richness and density. Given these results, increased drought intensity in the region may lead to decreased aquatic biodiversity.

Annika Walters (Co-Presenter/Co-Author)
USGS Wyoming Coop Fish and Wildlife Unit, annika.walters@uwyo.edu;

Frank Rahel (Co-Presenter/Co-Author)
University of Wyoming, frahel@uwyo.edu;

Lindsay Patterson (Co-Presenter/Co-Author)
Wyoming Department of Environmental Quality, lindsay.patterson@wyo.gov;

Ashleigh Pilkerton (Primary Presenter/Author)
Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, apilkert@uwyo.edu;

Abstract: Accumulation of sediment behind dams poses a critical challenge worldwide as it can prevent effective dam operation, compromise structural integrity, and increase maintenance costs. Sediment releases are a potential mitigation strategy but can harm downstream fisheries and aquatic life. Due to the potential for sediment to cause environmental degradation and impact surface water designated uses, many states have developed surface water quality criteria targeting sediment. However, the criteria often do not reflect the requirements of the biological communities they are meant to protect and may not sync with important biological processes. We evaluated the relationships between water column and river substrate approaches that measure sediment releases below Willwood Dam, WY, and their relevance to fisheries. Using multiple regression techniques, we developed a preliminary set of models for predicting river substrate metrics (hyporheic dissolved oxygen levels and fine sediment deposition rates) in salmonid spawning habitat from commonly measured watercolumn metrics. Preliminary models will be refined and updated to longitudinally predict downstream effects and quantify spatial variation. This research will better our understanding of metrics for monitoring sediment releases from dams and mitigating downstream impacts on fisheries, biological systems and fluvial processes.

Gea van der Lee (Primary Presenter/Author)
Wageningen Environmental Research, gea.vanderlee@wur.nl;

Michiel Kraak (Co-Presenter/Co-Author)
Institute of Biodiversity and Ecosystem Dynamics, M.H.S.Kraak@uva.nl;

Ralf C.M. Verdonschot (Co-Presenter/Co-Author)
Wageningen Environmental Research, ralf.verdonschot@wur.nl;

Piet F.M. Verdonschot (Co-Presenter/Co-Author)
University of Amsterdam / Wageningen Environmental Research , piet.verdonschot@wur.nl;

Abstract: Running water species have evolved traits that enable them to survive, exploit and even depend on the spatial and temporal variability of natural flow regimes. Human impacts have, however, altered these natural flow regimes. Disturbances outside the predictable flow regime to which stream organisms were originally adapted, can therefore reduce population densities. We hypothesized that a specific hydrologic disturbance leads to different ecological responses depending on the life stage of the exposed organism, as each life stage has different sensitivities to each specific stressor. To test this hypothesis, a two-year field study was performed in which we measured the discharge dynamics and population development of the caddisfly Agapetus fuscipes in four lowland streams. A stage-structured population model was used to test the impact of peak discharge on the different life stages. We showed that high discharge peaks during the early life stage of this caddisfly species can be fatal. To determine the impact of hydrologic changes on invertebrate population densities, it is thus crucial to study the appropriate temporal scales of the disturbances in relation to the critical periods in the life cycle of the exposed species.

Kyle Leathers (Primary Presenter/Author)
University of California Berkeley, kyle_leathers@berkeley.edu;

Guillermo de Mendoza (Co-Presenter/Co-Author)
Institute of Geography, Faculty of Oceanography and Geography, University of Gdansk, gdemendoza.eco@gmail.com;

David B. Herbst (Co-Presenter/Co-Author)
Institute of Marine Sciences, University of California Santa Cruz, and Sierra Nevada Aquatic Research Laboratory, University of California Santa Barbara, herbst@lifesci.ucsb.edu;

Gabriella Doerschlag (Co-Presenter/Co-Author)
University of California Berkeley, gdoerschlag@berkeley.edu;

Albert Ruhi (Co-Presenter/Co-Author)
Department of Environmental Science, Policy, and Management, University of California, Berkeley, albert.ruhi@berkeley.edu;

Abstract: Climate change may advance median snowmelt runoff in the Sierra Nevada up to two months by 2080. Although past studies support that extended low flows may affect macroinvertebrate composition and abundance, ramifications to food-webs remain largely unknown. Our project experimentally addressed how extended low flows, as a result of earlier snowmelt, may impact mountain stream food webs. We used nine large, flow-through channels at the Sierra Nevada Aquatic Research Lab (SNARL) in California and simulated three flow regimes: current conditions and low-flow duration increased by three and six weeks. We measured primary production and sampled benthic and emergent macroinvertebrates every three weeks. Early low flows increased daily maximum temperatures and diel fluctuations. Early low flow treatments increased algal respiration, but net primary production remained unaffected. The community composition of emerging insects and increased abundance of Chironominae were affected by low flow timing. Preliminary benthic macroinvertebrate results support that flatworms increased in abundance in response to early low flow. Nesting Brewers Blackbirds increased predation time of benthic macroinvertebrates during early low flow by 7-fold. Our results suggest that advanced low flows may have far-reaching effects on aquatic food webs.

Guillermo de Mendoza (Co-Presenter/Co-Author)
Institute of Geography, Faculty of Oceanography and Geography, University of Gdansk, gdemendoza.eco@gmail.com;

Romain Sarremejane (Co-Presenter/Co-Author)
Nottingham Trent University, romain.sarremejane@gmail.com;

Albert Ruhi (Co-Presenter/Co-Author)
Department of Environmental Science, Policy, and Management, University of California, Berkeley, albert.ruhi@berkeley.edu;

Robert Fournier (Primary Presenter/Author)
University of California, Berkeley, robertfournier@berkeley.edu;

Abstract: Biota in intermittent streams respond to seasonal drying via a wide range of resistance and resilience strategies. Despite early attempts to quantify the relative influence of different recolonization pathways in streams (storage effects, aerial dispersal, and upstream/downstream aquatic dispersal; Williams and Hynes 1976), the importance of spatial context remains untested. Here, we designed a replicated dispersal experiment along an intermittent stream to examine how habitat connectivity (i.e., distance from an upstream perennial reach) affected the importance of invertebrate recolonization pathways upon rewetting. To this end, we built mesh traps that prevented recolonization via all pathways except for one, and placed them at the end of the dry phase in Chalone Creek, Pinnacles National Park. Drift samples were collected daily after flow resumption, and the resulting benthic communities were compared—across trap types, and over space. Preliminary results highlight the importance of storage effects (i.e., persistence in the hyporheic). This study will help quantify the relative importance of resistance and resilience mechanisms in sustaining macroinvertebrate populations. As climate-driven droughts impact flow intermittency globally, a greater understanding of how organisms persist through drying events is key to strengthen conservation efforts.

Geoffrey Poole (Primary Presenter/Author)
Montana State University, Montana Institute on Ecosystems, gpoole@montana.edu ;

Elizabeth Mohr (Co-Presenter/Co-Author)
Montana State University, elizabethjmohr@gmail.com;

Katie Fogg (Co-Presenter/Co-Author)
Montana State University, s.katie.fogg@gmail.com;

Scott O'Daniel (Co-Presenter/Co-Author)
Confederated Umatilla Tribes, scottodaniel@ctuir.org;

Hayley Oakland (Co-Presenter/Co-Author)
Montana State University, hayleyoakland@montana.edu;

Ann Marie Reinhold (Co-Presenter/Co-Author)
Montana State University, Montana Institute on Ecosystems, reinhold@montana.edu;

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

James Stegen (Co-Presenter/Co-Author)
Pacific Northwest National Laboratory, james.stegen@pnnl.gov;

Abstract: Water exchange between a stream channel and hyporheic zone carries solutes from the channel to the benthic and hyporheic biotic communities that drive biogeochemical cycling in streams. Daily variation in river stage associated with hydropower dams creates a cyclical pattern of hydrologic gradients between the river and hyporheic zone. These gradients alternately drive water into and drain water from hyporheic storage, modifying the hyporheic hydrologic residence time distribution (RTD). However, such cyclical patterns of transient water storage-and-release do not replace normative patterns of hyporheic exchange, which often follow a power law RTD. We created a scalable model of transient (non-steady state) hyporheic exchange, storage, and nutrient uptake that simulates a power law RTD that is modified by pulses of water entering and exiting the hyporheic zone as a function of river regulation. Results suggest that the response of stream solute concentrations to flow regulation depends on the relationship between solute uptake kinetics and residence time in the hyporheic zone.

Anna Freixa (Primary Presenter/Author)
Catalan Institute for Water Research (ICRA), Girona, Spain, afreixa@icra.cat;

Juan David González-Trujillo (Co-Presenter/Co-Author)
The National Museum of Natural Sciences, Madrid, Spain, jdgonzalezt@unal.edu.co;

Carles Borrego (Co-Presenter/Co-Author)
Catalan Institute for Water Research (ICRA), Girona, Spain, cborrego@icra.cat;

Sergi Sabater (Co-Presenter/Co-Author)
Catalan Institute for Water Research (ICRA), Girona, Spain, ssabater@icra.cat;

Abstract: Bacterial assemblages colonizing river sediments can result from the species selection (or sorting) by the local environmental conditions, or from dispersal processes. The relative importance of these two processes may differ according to the hydrological variability in time and space, and this is particularly large in intermittent streams. We investigated river bacterial assemblages by sampling sediments from different riverine habitats in two sites (permanent vs. intermittent) and four hydrological periods (encompassing the expansion, contraction, and desiccation phases). Samples included sediments from the aquatic streambed and terrestrial floodplain habitats. Results reveal that river intermittency is reducing the temporal variability of bacterial assemblages among habitat types. Such outcome suggests that water scarcity is a selective force that favours few but tolerant dominant bacterial taxa. These tolerant taxa may also outcompete other species by the effect of priority effects. Our findings indicate that the large differences in bacterial assemblages from the intermittent site were imposed by the hydrological variability and emphasized the relevance of local processes as structuring factors. Our results highlight the complexity of temporal and spatial distribution of bacterial community assemblages occurring in temporary river networks.

Hiromi Uno (Primary Presenter/Author)
Center for Ecological Research, Kyoto University, hiromiuno1@gmail.com;

Mizushi Yokoi (Co-Presenter/Co-Author)
Center for Ecological Research, Kyoto University, yokoi.mizushi@ecology.kyoto-u.ac.jp;

Keitaro Fukushima (Co-Presenter/Co-Author)
Center for Ecological Research, Kyoto University, ktaro.f@gmail.com;

Yoichiro Kanno (Co-Presenter/Co-Author)
Colorado State University; Department of Fish, Wildlife, and Conservation Biology, Yoichiro.Kanno@colostate.edu;

Osamu Kishida (Co-Presenter/Co-Author)
Hokkaido University, kishida@fsc.hokudai.ac.jp;

Shunsuke Utsumi (Co-Presenter/Co-Author)
Hokkaido University, utsumi@fsc.hokudai.ac.jp;

Abstract: Diverse aquatic communities occur in floodplains, which harbor habitats with varying degrees of hydrological connectivity to the mainstream channel. In this study, we test a hypothesis that four faunal groups (plankton, benthos, fish, and amphibian) respond uniquely to hydrological sequences during a post-flood period, and as a whole form diverse aquatic communities along the hydrological connectivity gradient. To examine the processes that aquatic communities are shaped in each waterbody, we conducted repeated surveys over the flood recession period and broad spatial survey after the cessation of flood. Each faunal group responded differently to the hydrological dynamics over the flood recession period to explain the patterns of habitat segregation in a floodplain. Plankton was reduced by the flow at flood peak. Salmonid fishes were more abundant in waterbodies which were hydrologically connected to the mainstream at flood peak. The amphibian eggs were laid in waterbodies that had still-water at their breeding timing. The benthic composition was influenced by the existence of the flow at the time of sampling. Overall, aquatic biota shifted from isolated ponds to more connected waterbodies to the river, a mechanism supporting diverse aquatic communities in a floodplain.

Jacob Hosen (Primary Presenter/Author)
Purdue University, jhosen@purdue.edu;

Joanna Blaszczak (Co-Presenter/Co-Author)
University of Nevada, Reno, jblaszczak@unr.edu;

Matthew Cohen (Co-Presenter/Co-Author)
University of Florida, mjc@ufl.edu;

Robert Hensley (Co-Presenter/Co-Author)
Battelle, National Ecological Observatory Network , hensley@battelleecology.org;

Kelly Hondula (Co-Presenter/Co-Author)
National Environmental Observation Network, khondula@sesync.org;

William H McDowell (Co-Presenter/Co-Author)
University of New Hampshire, bill.mcdowell@unh.edu;

Jody Potter (Co-Presenter/Co-Author)
University of New Hampshire, jody.potter@unh.edu;

Peter Raymond (Co-Presenter/Co-Author)
Yale University, peter.raymond@yale.edu;

Kevin Ryan (Co-Presenter/Co-Author)
Northeastern University, ryan.kevi@northeastern.edu;

Bryan Yoon (Co-Presenter/Co-Author)
Northeastern University, b.yoon@northeastern.edu;

Abstract: High frequency spectroscopy measurements in freshwaters hold promise for estimating organic matter processing rates in situ. However, difficulties correcting and interpreting spectroscopy data have limited application of this tool. We leveraged a network spanning the United States—including National Ecological Observatory Network (NEON) sites—of in situ sensors measuring ultraviolet-visible (UV-Vis) absorbance (collected with SUNA sondes) to interpret freshwater optical spectroscopy time series. We predicted that diel changes to high frequency UV-Vis absorbance spectra can be used to measure transformation and production of DOM. For example, we expected that streams with high aromatic DOM levels and low canopy cover would exhibit changes to UV-Vis absorbance spectra around solar noon indicative of DOM photo-oxidation. Where water clarity was high (low turbidity and aromatic DOM) and canopy cover was low, we predicted certain fractions of DOM would increase throughout the day, indicative of photosynthetic DOM production. After applying a revised temperature correction to UV-Vis and fDOM time series, we found that diel signals were correlated to insolation, turbidity, canopy cover, and fDOM levels. Using this analysis, we estimate that photosynthesis exceeds photo-oxidation in most lakes, streams, and rivers studied.

Ute Risse-Buhl (Primary Presenter/Author)
RPTU, Ecology Department, ute.risse-buhl@rhrk.uni-kl.de;

Shai Arnon (Co-Presenter/Co-Author)
Ben-Gurion University of the Negev, sarnon@bgu.ac.il;

Edo Bar-Zeev (Co-Presenter/Co-Author)
Ben-Gurion University of the Negev, Israel, edobarzeev@gmail.com;

Anna Oprei (Co-Presenter/Co-Author)
Technical University of Brandenburg Cottbus-Senftenberg, Germany, anna.oprei@b-tu.de;

Aaron Packman (Co-Presenter/Co-Author)
Northwestern University, a-packman@northwestern.edu;

Ignacio Peralta-Maravar (Co-Presenter/Co-Author)
University of Roehampton, UK, Nacho.Peralta@roehampton.ac.uk;

Anne Robertson (Co-Presenter/Co-Author)
Roehampton University, A.Robertson@roehampton.ac.uk;

Yoni Teitelbaum (Co-Presenter/Co-Author)
University of the Negev, Israel, ytbaum@gmail.com;

Michael Mutz (Co-Presenter/Co-Author)
Department of Freshwater Conservation, BTU-Cottbus Senftenberg, m.mutz@b-tu.de;

Abstract: Streams and river beds are metabolic hotspots contributing significantly to global biogeochemical fluxes. Streambed morphodynamics is well recognized where sediment grains either move (migrating phase) or rest (resting phase). The frequency and the duration of these two alternating phases depend on the flow conditions and sediment grain size. The common perspective in stream ecology is binary and focuses on stable bed morphology that is infrequently disturbed by streambed migration during relatively short flood events. However, finer sediment fractions that make up large proportion to majority of sediment in some stream types migrate more frequently. Here, we extend the overly simplistic binary view by relating the frequency and duration of alternating resting and migrating phases to the temporal scale of biological processes. We expect sediment migration to act as a filter to the community depending on the temporal scale of sediment migration. The proposed concept enables to further the understanding of ecological and biogeochemical processes in streambeds with frequently rolling and saltating bedload as well as in sand-bed streams with migrating bedforms. We expect the spatiotemporal mosaic of migrating and resting streambed patches to shape processes at reach scale.

Ann Marie Reinhold (Primary Presenter/Author)
Montana State University, Montana Institute on Ecosystems, reinhold@montana.edu;

Stephanie Ewing (Co-Presenter/Co-Author)
Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, USA, stephanie.ewing@montana.edu;

Robert Payn (Co-Presenter/Co-Author)
Montana State University, Montana Institute on Ecosystems, rpayn@montana.edu;

Geoffrey Poole (Co-Presenter/Co-Author)
Montana State University, Montana Institute on Ecosystems, gpoole@montana.edu ;

Maury Valett (Co-Presenter/Co-Author)
University of Montana, Maury.Valett@mso.umt.edu;

Abstract: We explore the conceptual model that geomorphic process domains function as hydro-biogeochemical bioreactors, consisting of a non-reactive flow compartment and a reactive-storage compartment. We simulated the reactive transport of a generic solute in a suite of streams, calculating Damköhler numbers for the reactive-storage compartment (hyporheic zone) and whole reactor (stream reach integrating the non-reactive channel compartment and hyporheic zone). We approximated hyporheic hydraulics with power-law residence-time distributions and assumed advective transport of solutes to hyporheic zones. We systematically varied the reaction-rate constant of the solute, hyporheic-zone size, and shape of the hyporheic residence-time distribution, holding the following constant: stream-channel geometry, surface-water discharge, and solute loading. Hyporheic Damköhler numbers were positively related to longer average residence times and the reaction-rate constant. However, effective Damköhler numbers for stream reaches were positively related to hyporheic-zone size and shorter average residence times. We explored scenarios that demonstrate how the amount of water flowing through the hyporheic zone can be more important than the hyporheic Damköhler number in determining the Damköhler number of the reach. Our approach shows promise for scaling hyporheic biogeochemical observations to predict whole-system solute dynamics.

Suzanne Kelson (Primary Presenter/Author)
University of Nevada, Reno, skelson@unr.edu;

Timothy Caldwell (Co-Presenter/Co-Author)
McBain Associates, Tim@mcbainassociates.com;

Sudeep Chandra (Co-Presenter/Co-Author)
Global Water Center and Biology Department, University of Nevada, Reno, sudeep@unr.edu;

Scott McBain (Co-Presenter/Co-Author)
McBain Associates, scott@mcbainassociates.com ;

Natalie Stauffer-Olsen (Co-Presenter/Co-Author)
Trout Unlimited, Natalie.Stauffer-Olsen@tu.org;

Rene Henery (Co-Presenter/Co-Author)
Trout Unlimited, Rene.Henery@tu.org;

Tara McKinnon (Co-Presenter/Co-Author)
University of Nevada, Reno, taramckinnon@unr.edu;

Abstract: Given the extensive hydrologic alteration of streams globally, there is a need for a mechanistic understanding of how stream flows influence productivity waves through food webs. Here, we quantify food web productivity during the spring-summer snowmelt recession limb to improve instream flow recommendations in a heavily diverted watershed (> 90% of flow is diverted in the summer), the Upper Shasta River, California, USA. We tracked productivity of benthic biofilms, standing crop of benthic macroinvertebrates, and rates of drifting macroinvertebrates above and below the water diversion. We found that below the diversion, productivity of biofilms and benthic macroinvertebrates remained high despite flow reductions, but food availability to trout (Oncorhynchus mykiss) was reduced as fewer invertebrates drifted in stagnant waters. We observed that the loss of drift forced trout to switch from energetically favorable drift feeding behavior to energetically expensive benthic/search feeding behavior 1 month earlier in the summer below the diversion than above. We are implementing bioenergetics models to quantify trout energetic condition under impaired food availability and hydraulic conditions across different stream flows. This modeling will support instream flow recommendations that synthesize ecologic and hydrologic conditions for fish.

Dave Lytle (Primary Presenter/Author)
Oregon State University, lytleda@oregonstate.edu;

Abstract: River communities of plants, invertebrates, and fish are in a constant state of flux, with local extinctions and range expansions occurring over ecological timescales. These non-equilibrium dynamics are driven by the rivers themselves, which impose flow and disturbance regimes that fluctuate on daily, annual, or longer timescales. While population models (matrix models, logistic growth projections, Lotka-Volterra equations) can describe population trajectories and species interactions in these dynamic ecosystems, model analysis often involves asymptotic analysis, or taking the limit of population dynamics over long timescales -- a method that may not be appropriate for river communities that aren’t in equilibrium. An alternative approach is to measure the transient dynamics of populations over piecewise timeframes of interest. While asymptotic analysis sometimes predicts eventual extirpation of less-competitive species, and thus community simplification, transient analysis shows that these species can co-occur over meaningful timescales (10’s to 100’s of generations or longer). The concepts are illustrated with empirical examples that explore plant, invertebrate, and fish populations that inhabit desert rivers prone to flood and drought events as well as non-stationary shifts in flow regime due to climate change.

Kevin Soto (Primary Presenter/Author)
Interamerican University of Puerto Rico, Arecibo Campus, nivek0100@gmail.com;

Abstract: Loss of habitat connectivity possess a major threat for aquatic migratory species. Worldwide man-made dams are structures with high potential to negatively impact migratory species by disrupting habitat connectivity. In addition to dams, in the tropic’s droughts can have strong negative effects on aquatic communities due to habitat loss or connectivity in the upper parts of the drainage basin. We selected freshwater amphidromous shrimps since in Puerto Rico they are the dominant consumers on mountainous streams. a) To understand the effects of dams on freshwater shrimps we did a literature review focused on Puerto Rico and other tropical countries. b) To determine the effects of drought on shrimps we analyzed weekly rainfall and shrimp data from the Luquillo LTER, from shrimps sampled at Quebrada Prieta from 1993 to 2016. Dams primarily affected migratory species by disrupting stream connectivity and producing a “bottleneck” effect. Dams without spillway inhibited shrimp migration. Shrimp densities and pools had a strong association. Droughts did not have lasting effects influence on shrimp abundance and species richness at pools studied at 400 m asl. Future directions are to understand how abundance and assembly changed within drought years.

Andrew Blinn (Primary Presenter/Author)
Kent State University, ablinn2@kent.edu;

Zia Ul Hassan (Co-Presenter/Co-Author)
Kent State University, zhassan1@kent.edu;

Aditi Bhaskar (Co-Presenter/Co-Author)
Colorado State University, aditi.bhaskar@colostate.edu;

Anne Jefferson (Co-Presenter/Co-Author)
Kent State University, ajeffer9@kent.edu;

David Costello (Co-Presenter/Co-Author)
Kent State University, dcostel3@kent.edu;

Abstract: Indices of stormwater management effectiveness focus on the effect actions have on the hydrologic regimes and levels of erosion mitigation in the watershed. To understand the broader implications stormwater management can have on water quality and ecosystem health, we are studying how hydrologic regimes in urban streams are linked to metrics of ecosystem function. High-frequency data from sensors placed in-stream and remote satellite data of solar irradiance were collected over a two-year study period in three streams near Cleveland, Ohio. Daily rates of gross primary production (GPP),ecosystem respiration (ER), and gas exchange velocity were estimated through inverse Bayesian modeling of dissolved oxygen dynamics. Estimates of GPP and ER provide point-comparisons of stream ecosystem function before and after storm events, and were used to quantify the resistance of production and respiration to elevated discharge. Initial results show ER to be less responsive (i.e., more resistant) to high flow than GPP, resulting in well-lit streams rarely or never experiencing days of net-autotrophic function following elevated stormflow. Disruptive stormflow events had a return frequency that was shorter than recovery intervals of GPP which indicated cumulative degradation of ecosystem function over time.

Gabriele Consoli (Primary Presenter/Author)
Swiss Federal Institute of Aquatic Science and Technology, EAWAG ; Aquatic Ecology dpt., gabriele.consoli@eawag.ch;

Christopher Robinson (Co-Presenter/Co-Author)
Swiss Federal Institute of Aquatic Science and Technology, EAWAG ; Aquatic Ecology dpt., Christopher.robinson@eawag.ch;

Abstract: The long-term experimental flood program on the River Spöl had substantial ecological effects on instream ecosystems, by reintroducing seasonal disturbance in a flow-regulated river. Macroinvertebrate assemblages responded over time with marked shifts in composition. Densities of the dominant (comprising 90% of the assemblage before the flood program) Gammarus fossarum declined, and taxa resilient to flow disturbance (some mayflies and stoneflies) increased in number and density. We tested whether the repeated flow-pulse disturbances selected demographic traits of populations through sequential episodes of high mortality and recovery using the amphipod as a case-study example. We expected that the physical filtering during floods, and changes in resources and habitat availability, altered the population size structure of G. fossarum, thereby redistributing macroinvertebrate size structure in the river. We applied high-throughput image analysis of G. fossarum over 20 years in the Spol to examine if the observed temporal changes in abundance were reflected in changes in size-class distribution. We relate our findings of flood-induced environmental changes to disturbance effects on population resistance and resilience. We expect the results will generate insights into the eco-evolutionary selection of experimental floods on organisms and mechanisms influencing community assembly.