SFS Annual Meeting

5/22/2019  |   09:00 - 09:15   |  250 AB

CLIMATE CHANGE IN HIGH-GRADIENT MOUNTAIN STREAMS: SEARCHING FOR REFUGIA IN A HETEROGENEOUS LANDSCAPE High-gradient mountain streams have steep ecological turnover in the longitudinal dimension. Research on climate-change effects has emphasized upstream shifts in ecological pattern and process, with the highest reaches typically assumed to be the most vulnerable (the 'summit trap' idea). However, complex topography and hydrological source heterogeneity in mountain stream networks typically makes lotic habitat more mosaic-like than gradient-like. For example, locally cold habitat patches occur in ice-fed headwaters and in mainstems at ice-fed tributary confluences. Increasingly, conservation strategies are emphasizing adaptation to inevitable change, including identification and protection of climate refugia (localities that are relatively buffered from changes in regional climate). The mosaicism inherent to mountain stream networks suggests the possibility for climate refugia in localities with hydrological and/or geomorphological characteristics that confer resistance to long-term climate change. This session will consider cross-disciplinary perspectives from hydrology, geomorphology, and population, community, and ecosystem ecology to begin to synthesize our understanding of potential climate refugia in high-mountain stream networks across the globe. We will also discuss a strategy for long-term monitoring of key ecological responses in mountain streams, data from which can be used to test hypotheses about climate-change refugia.

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

Scott Hotaling (Co-Presenter/Co-Author), Washington State University, scott.hotaling@uky.edu;


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5/22/2019  |   09:15 - 09:30   |  250 AB

ICY SEEPS MAY ACT AS A REFUGE FOR ALPINE STREAM INVERTEBRATES: EVIDENCE FROM THE CENTRAL ROCKY MOUNTAINS Air temperatures are warming fastest in high elevation ecosystems such as alpine zone. As a result, the hydrology of mountain tops is changing causing glaciers to melt and the loss of ice-fed streams. We investigated the invertebrate assemblages of alpine streams that differed in hydrologic source. We were particularly interested in icy seep streams that originated from subterranean ice (e.g., rock glaciers). Icy seeps may remain longer than other hydrologic sources because the debris over the subterranean ice insulates from warming air temperatures. We investigated the degree to which icy seeps may be a refuge for cold-adapted alpine invertebrates. We measured habitat characteristics and collected invertebrates from seven icy seeps, four surface glacier-fed and six snowmelt-fed streams in 2016 and 2017. Glacier-fed and icy seep streams had the coldest water temperatures. Icy seeps had the highest chlorophyll a (21.6 µg/m2), an indicator of algal biomass. The biomass of invertebrates was highest in snowmelt-fed streams (923 mg/m2), lowest in surface glacier-fed streams (317 mg/m2) and icy seeps spanned the gap between them. Icy seeps are diverse streams that may provide a cold-water refuge for alpine assemblages.

Lusha Tronstad (Primary Presenter/Author), University of Wyoming, Wyoming Natural Diversity Database, tronstad@uwyo.edu;


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5/22/2019  |   09:45 - 10:00   |  250 AB

HYDROCLIMATIC DROUGHT EFFECTS ON PHYSICAL HABITAT FEATURES OF HEADWATER STREAMS IN THE SIERRA NEVADA OF CALIFORNIA Hydroclimatic change in mountainous regions exhibits extremes of flow regime from winter floods produced by atmospheric river storms to prolonged and severe drought conditions. In the Sierra Nevada of California we selected 24 headwater streams to monitor over a period of 8 years that provided opportune conditions to examine these extremes. Twelve third-order catchments each with nested tributaries covered a varied geography of clines in elevation (1200-3600 m), aspect (N-S), and geology (volcanic, granitic). Stage and temperature sensors showed that even during low drought flows water temperatures were stable or even cooled somewhat in some of the smaller streams. Increased dissolved minerals suggest that groundwater inflow buffers against drought in some streams while others become intermittent. As drought persists, lotic habitat disappears as riffles contract, while algae and organic matter accumulate, and rocky substrates become more embedded. Geography of benthic invertebrate communities indicate distinct differences between volcanic northern and granitic southern streams. Drought depletes diversity but communities are more stable in high flows. The results highlight the mixed resistance and vulnerabilities of high mountain headwater stream habitats to the effects of prolonged drought as forecast for this and other regions.

David B. Herbst (Primary Presenter/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;


R. Bruce Medhurst (Co-Presenter/Co-Author), Sierra Nevada Aquatic Research Laboratory, ebbnflow@yahoo.com;


Aleksandra Karapetrova (Co-Presenter/Co-Author), Sierra Nevada Aquatic Research Laboratory, aleksandra.karapetrova@gmail.com;


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5/22/2019  |   10:00 - 10:15   |  250 AB

DECLINE IN HABITAT SUITABILITY LIMITS EFFICACY OF STREAM REFUGIA UNDER CLIMATE CHANGE Climate change vulnerability depends on organisms dispersing across landscapes rapidly enough to keep pace with suitable temperatures. Freshwater faunas are vulnerable because dispersal is constrained within stream networks, but bifurcating topology may provide slow-velocity dispersal pathways via cold tributaries. We assessed whether 233 fish species can keep pace with shifting isotherms in the southern Appalachian Mountains, USA. We combined multi-model ensembles to project isotherm shift velocities and species’ occurrences across 50,384 stream reaches with species-specific dispersal velocities to forecast which species are vulnerable and where. For low and high greenhouse gas emissions scenarios, we estimate isotherms will shift along mainstem pathways at median rates of 1.18 and 2.35 km·decade-1, respectively, versus only 0.27 and 0.53 km·decade-1 for tributaries. Dispersal velocities of small species occupying low-gradient streams are most likely to fall short of shifting isotherms. Although slow-velocity tributaries reduce the number of species experiencing dispersal deficits by 5.3% and 92.4%, persistence in tributaries will be countered by a mean 10.9% reduction in habitat suitability (versus 1.9% for mainstems). This reveals tradeoffs shaping the efficacy of thermal refugia, highlighting the importance of climate change abatement to curtail biodiversity loss in streams.

Matthew Troia (Primary Presenter/Author), University of Texas San Antonio, troiamj@gmail.com;


Anna Kaz (Co-Presenter/Co-Author), University of Tennessee, akaz@vols.utk.edu;


Cameron Niemeyer (Co-Presenter/Co-Author), University of Tennessee, jniemeye@vols.utk.edu;


Xingli Giam (Co-Presenter/Co-Author), University of Tennessee, xgiam@utk.edu;


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5/22/2019  |   10:15 - 10:30   |  250 AB

GLACIERIZED CATCHMENTS IN THE TROPICAL ANDES: POSSIBLE IMPLICATIONS OF CLIMATE CHANGE Stream networks in snow-capped mountains are highly heterogeneous landscapes with streams from different sources (glacier, groundwater, rain) mixing and producing a complex mosaic of environmental and hydrologic conditions. Climate change is expected to alter current dynamics in these systems, especially in response to glacier retreat and consequent reduction in the amount of meltwater reaching the streams. Our group has been studying the ecology of a high altitude glacierized catchment in the Ecuadorian Andes for more than ten years, and has found significant results regarding hydrologic and environmental conditions and benthic community structure and function in glacier-fed, spring and groundwater-fed streams and their confluences. Here we report these results, highlight recent progress, discuss the impact of climate change, and speculate on possible future refugia that could persist under future climatic conditions.

Patricio Andino (Co-Presenter/Co-Author), Laboratorio de Limnología, Museo QCAZ-I, Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, puchitricio@gmail.com ;


Sophie Cauvy-Fraunié (Co-Presenter/Co-Author), IRSTEA Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture, sophie.cauvy@gmail.com;


Olivier Dangles (Co-Presenter/Co-Author), Institut de Recherche pour le Développement (IRD), Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul Valéry Montpellier, EPHE, IRD, Montpellier, France., olivier.dangles@ird.fr;


Rodrigo Espinosa (Co-Presenter/Co-Author), Laboratorio de Limnología, Museo QCAZ-I, Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, reespinosaro80@gmail.com;


Dean Jacobsen (Co-Presenter/Co-Author), Freshwater Biological Laboratory, University of Copenhagen, Denmark, djacobsen@bio.ku.dk;


Verónica Crespo-Pérez (Primary Presenter/Author), Laboratorio de Limnología, Museo QCAZ-I, Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, mvcrespo@puce.edu.ec;


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