5/23/2016  |   13:30 - 13:45   |  308

THE EFFECTS OF DROUGHT AND STREAM DRYING ON AQUATIC INVERTEBRATES AT POINT REYES NATIONAL SEASHORE Drought affects streams by decreasing water flow and surface area. As a result, some streams lose surface flow during the summer ('intermittent' streams), while others flow year-round ('perennial' streams). For the last four years, California has been in a record-breaking drought, which may result in some perennial streams shifting to intermittent states. Our objective is to understand how stream drying influences the species richness and density of aquatic invertebrates in the Pine Gulch Watershed at Point Reyes National Seashore. From February to March 2015, we collected invertebrate samples from 5 perennial and 5 intermittent sites. We used flow sensors to monitor flow status at intermittent sites. Our data showed similar species richness but different density between perennial sites and intermittent sites, and that longer flow duration at intermittent sites correlated with increased density and species richness. The lack of species richness differences between intermittent and perennial sites may be due to close proximity of perennial refuges. If California’s drought continues, perennial refuges may get further apart and we expect to see biodiversity losses as streams transition from perennial to intermittent.

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


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


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


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5/23/2016  |   13:45 - 14:00   |  308

HYDROLOGIC VARIATION AND AQUATIC MACROINVERTEBRATE COMMUNITITES IN INTERMITTENT STREAMS OF NORTH-CENTRAL OHIO Aquatic macroinvertebrates are important components of stream food webs where streamflow is the master variable driving community dynamics. Field mapping is often employed to assess spatiotemporal patterns of river drying, but this approach is time consuming and often does not capture important hydrological characteristics important for structuring macroinvertebrate communities. Electrical resistivity (ER) sensors have enabled continuous monitoring of streamflow of intermittent streams. Here we explore these different methods and their ability to describe variation in macroinvertebrate community structure in 10 intermittent streams in Ohio. We collected macroinvertebrates, deployed ER sensors (6/stream), and made weekly visits to map wet/dry conditions. Stream mapping and ER sensor data well described the variation in macroinvertebrate community structure across the study sites. Eleven linear regression models described significant variation in community metrics (R2 0.35-0.56). The most consistent predictors of macroinvertebrate metrics was the temporal variation streamflow measured by ER sensors and the proportion of stream channel that dried. ER sensors provide an important complement to on-the-ground measures of hydrology, and that both measures can enhance our understanding of macroinvertebrate community dynamics in intermittent streams.

Katie Costigan (Primary Presenter/Author), University of Louisiana Lafayette, costigan@louisiana.edu;


Charles Goss ( Co-Presenter/Co-Author), Ohio State University , goss.44@osu.edu;


Kristin Jaeger ( Co-Presenter/Co-Author), Ohio State University , jaeger.48@osu.edu;


P. Charles Goebel ( Co-Presenter/Co-Author), Ohio State University , goebel.11@osu.edu;


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5/23/2016  |   14:00 - 14:15   |  308

INFLUENCE OF FLOW REGIME, GEOMORPHOLOGY, AND HABITAT ON CRAYFISH ASSEMBLAGES OF THE OZARK HIGHLANDS Crayfish are ecological dominants in many streams due to their multifaceted role as predators, prey, ecosystem engineers, and bioprocessors. Several crayfish species are imperiled and highly endemic. While the seasonal drying of intermittent streams in the Ozarks is a natural process, the pressures of human water use coupled with global climate change may induce additional stress on the region’s sensitive aquatic biota in the future. Our objectives were to 1) determine crayfish occupancy and species densities in two hydrologic regimes (Groundwater Flashy and Intermittent Flashy) and 2) assess the relationship between hydrologic regime, crayfish occupancy, species density, and habitat. Crayfish were sampled from 10 Intermittent Flashy and 10 Groundwater Flashy streams and environmental variables were measured. As determined by occupancy models in Program PRESENCE, species occupancy varied among flow regimes. Crayfish density differed between two years (p = 0.005) but did not differ among flow regimes. MANOVA results indicated all environmental variables differed by both hydrologic regime and year. Information gained from flow-crayfish ecology relationships may guide future conservation decisions of imperiled crayfish in the Ozark Highlands.

Allyson Yarra (Primary Presenter/Author), University of Arkansas, ayarra@email.uark.edu;


Daniel Magoulick ( Co-Presenter/Co-Author), Arkansas Cooperative Fish and Wildlife Research Unit, University of Arkansas, danmag@uark.edu;


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5/23/2016  |   14:15 - 14:30   |  308

MACROINVERTEBRATE SEEDBANK RESISTANCE AND RESILIENCE IN RESPONSE TO SEVERE SUPRA-SEASONAL DROUGHT The aquatic macroinvertebrate ‘seedbank’ comprises the eggs, juveniles and adults that persist in temporary stream sediments after water loss, promoting community persistence during dry phases. However, how seedbank assemblages in temperate-zone streams will respond to drought-related increases in dry-phase extent and duration is unknown. We rehydrated ‘dry’ sediments from the ephemeral headwaters and intermittent downstream reaches of an English stream during a supra-seasonal drought. Ephemeral headwater assemblages, which had experienced an exceptionally long dry phase, mainly comprised Chironomidae, Oligochaeta and Sphaeriidae. Several taxa previously recorded in non-drought years (notably Gammarus pulex and Planariidae) were absent, indicating local elimination from the seedbank. Seedbanks in intermittent downstream reaches experienced shorter dry phases and comprised more diverse assemblages. Post-drought sampling revealed variable recolonization of the ephemeral headwaters, with G. pulex recorded <4 months after flow returned, while Planariidae remained absent >12 months later. Our results highlight small-scale spatial variability in seedbank assemblages, with localized refuges characterized by greater seedbank persistence during dry phases. Seedbank inhabitants that survive in these refuges enhance community resilience after flow returns, in particular promoting recolonization by mobile taxa.

Rachel McNeish (Primary Presenter/Author), California State University Bakersfield, rachel.e.mcneish@gmail.com;


Paul J. Wood ( Co-Presenter/Co-Author), Loughborough University, P.J.Wood@lboro.ac.uk;


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5/23/2016  |   14:30 - 14:45   |  308

DESICCATION-RESISTANCE AS A PROMOTER FOR INVERTEBRATE COMMUNITY RESILIENCE IN TEMPORARY TROPICAL FRESHWATERS: THE INFLUENCE OF ENVIRONMENTAL HARSHNESS Desiccation-resistance forms (DRF) are evolutionary adaptations to flow intermittence and are supposed to promote community resilience and species coexistence through ‘storage effects’. However, the role of environmental variations on the production of DRFs is still poorly understood in freshwaters. In particular, environmental harshness may influence the contribution of DRF to community resilience due to selection pressure on regional species pools. In this study, we addressed the significance of DRF in promoting the resilience of aquatic invertebrate communities in freshwater ecosystems across a gradient of environmental harshness. We quantified the contribution of DRF to community resilience in 9 intermittent streams and 6 temporary wetlands from 3 Bolivian ecoregions displaying contrasted environmental harshness. We first predicted the contribution of DRF to increase with environmental harshness in both stream and wetland, due to drastic selection of the regional species pool,, We further predicted the contribution of DRF to be overall higher in wetlands than in rivers, due to lower connectivity for the former. Preliminary results suggest that the contribution of DRF to community resilience in non-perennial freshwaters may depend greatly on environmental variations.

Thibault Datry (Primary Presenter/Author), INRAE, France, Thibault.datry@inrae.fr;


Edgar Goitia ( Co-Presenter/Co-Author), Universidad Mayor de San Simón, Cochabamba, Bolivia, e.goita@umss.bo;


Jose Zubieta ( Co-Presenter/Co-Author), IRD, ULRA, Cochabamba, Bolivia, pp_zubiet@yahoo.com;


Ross Vander Vorste ( Co-Presenter/Co-Author), IRSTEA/Virginia Tech , ross.vandervorste@vt.edu;


Nabor Moya ( Co-Presenter/Co-Author), UNIBOL, Chimore, Bolivia, nabor.moya@gmail.com;


Thierry Oberdorff ( Co-Presenter/Co-Author), IRD, thierry.oberdorff@ird.fr;


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5/23/2016  |   14:45 - 15:00   |  308

STORAGE EFFECTS IN INTERMITTENT RIVER ECOLOGY: IMPLICATIONS FOR COEXISTENCE, BIOTIC INTERACTIONS AND COLONIZATION DYNAMICS The idea that storage zones can influence important community processes such as coexistence, biotic interactions and colonization dynamics in temporally varying environments has received growing theoretical and empirical support in ecology (e.g. storage effects (SE)). SE occur when persistent life-history strategies buffer population or community dynamics to environmental variation and can be dominant processes that maintain biodiversity. However, stream ecologists have not thoroughly explored SE, especially in hydrologically variable intermittent rivers, despite evidence that the use of the hyporheic zone and/or the production of desiccation-resistance forms during dry phases could promote species coexistence and influence biotic interactions and colonization dynamics. We provide examples of how community processes in intermittent rivers could be influenced through SE, develop a conceptual framework to test hypotheses needed to support SE theory and discuss applied aspects in river management. We emphasize that the potential importance of SE in intermittent rivers justifies preserving and protecting vertical connectivity and dry riverbeds from human activities such as gravel extraction, water abstraction and 4x4 recreation which could negatively affect the long-term persistence of communities in intermittent rivers.

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


Thibault Datry ( Co-Presenter/Co-Author), INRAE, France, Thibault.datry@inrae.fr;


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