SFS Annual Meeting

5/21/2018  |   14:00 - 14:15   |  420 A

EPILITHIC BIOMASS ABUNDANCE AND COMPOSITION: INFLUENCES ON ALLOCHTHONOUS AND AUTOCHTHONOUS NITROGEN SOURCES Excessive nutrient inputs can cause algal and cyanobacterial blooms in river systems. Elevated concentrations of phosphorus (P) and nitrogen (N) in the Upper Clark Fork River (UCFR) of MT promote extensive mid-summer blooms of green algae (i.e. Cladophora), with some evidence of late-summer cyanobacteria proliferation. In addition to nutrient loading, the UCFR suffers from major metal contamination. Algal form and abundance may play a critical role in metal movement through the food web. Research addressing N availability, the relative abundance of N-fixing cyanobacteria and Cladophora in the periphyton community, and their interactions was addressed to determine the implications of nutrient enrichment. Summer-long assessment of N- fixation rates revealed fluxes ranging from 0.7 to 45.4 ugNm-2h-1 while biofilm abundance varied by almost 80-fold (0.456 to 36.1 g AFDM/m2) over six weeks of sampling. Comparisons with nitrate uptake rates during changing periphyton composition were used to determine the role of allochthonous and autochthonous N sources on epilithic biomass abundance and composition.

Marc Peipoch (Co-Presenter/Co-Author), Stroud Water Research Center, mpeipoch@stroudcenter.org;


H. Maurice Valett (Co-Presenter/Co-Author), University of Montana, Division of Biological Sciences, maury.valett@umontana.edu;


Kim Bray (Primary Presenter/Author), University of Montana, bray.k.kim@gmail.com;


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5/21/2018  |   14:15 - 14:30   |  420 A

TROUT RECOVERY IN A RESTORED RIVER: COMBINING METAL BURDEN AND STABLE ISOTOPE APPROACHES Coincident patterns of trout abundance and severity of metal-contamination along the Upper Clark Fork River (UCFR) in Montana, USA, have generated concern among restoration practitioners and questioned the underlying causes of longitudinal decreases in fish density. Approximately 200-300 trout/km are present in highly polluted headwaters of the river while only 20-30 trout/km are routinely captured in the least contaminated sections of the UCFR. In this study, nuisance algal growth and warm temperatures during base flow conditions are evaluated as additional factors hindering full recovery of trout populations. Historical records of benthic algae and invertebrate densities follow similar trends, but longitudinal changes in filamentous algae (50-150 g AFDM/m2) suggest different patterns in primary productivity with influence on invertebrate community composition. Recent modelling efforts combining metal body burdens (Cu, As, Zn, Pb, Cd), 13C and 15N signatures, and fish gut content analysis are employed to assess trophic structure in the UCFR under varying conditions of water temperature and algal production. Preliminary results show longer food chain length during summer algal blooms emphasizing the need to address trophic interaction between trout and prey populations in the context of algal influences on metal contaminants

Kimberly Bray (Co-Presenter/Co-Author), University of Montana, kimberly.bray@umconnect.umt.edu;


H. Maurice Valett (Co-Presenter/Co-Author), University of Montana, Division of Biological Sciences, maury.valett@umontana.edu;


Marc Peipoch (Primary Presenter/Author), Stroud Water Research Center, mpeipoch@stroudcenter.org;


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5/21/2018  |   14:30 - 14:45   |  420 A

INTERACTIONS AMONG HABITAT COMPLEXITY, MACROINVERTEBRATES, AND TROPHIC DYNAMICS DOWNSTREAM OF A LARGE-RIVER DAM: IMPLICATIONS FOR FOOD WEB STABILITY The construction of dams represents one of the most pervasive influences on large-river ecosystems, and is commonly cited as a major factor contributing to the decline of native species. While natural resource agencies have spent millions of dollars to restore physical habitat attributes and flow regimes associated with dams, few efforts have considered how these abiotic alterations reverberate through the food web and influence trophic interactions. To address this disconnect, we combined multiple estimates of habitat complexity (e.g., benthic substrate heterogeneity, percentage of off-channel habitats and in-stream islands, temperature and flow regimes), benthic macroinvertebrate community structure and production, and fish diets along a longitudinal gradient of dam alteration in the regulated Missouri River in Montana, USA. Our results indicate a trend of increasing habitat complexity, more diverse macroinvertebrate communities, larger diet breadths of sturgeon (Scaphirhynchus spp.) species, and decreasing diet overlap between sympatric shovelnose sturgeon (Scaphirhynchus platorynchus) and pallid sturgeon (Scaphirhynchus albus) with increasing distance from the dam. These findings highlight the potential for large-river dams to alter stabilizing food-web characteristics, which must be considered for effective natural resource management of these highly modified systems in the future.

Eric Scholl (Primary Presenter/Author), U.S. Geological Survey, escholl@usgs.gov;


Addie Dutton (Co-Presenter/Co-Author), Montana Cooperative Fishery Research Unit, Montana State University , adeline.dutton@msu.montana.edu;


Wyatt Cross (Co-Presenter/Co-Author), Montana State University, wyatt.cross@montana.edu ;


Christopher Guy (Co-Presenter/Co-Author), U.S. Geological Survey, Montana Cooperative Fishery Research Unit, Montana State University, cguy@montana.edu;


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5/21/2018  |   14:45 - 15:00   |  420 A

MANAGEMENT AND LIMNOLOGY INTERACT TO DRIVE WATER TEMPERATURE PATTERNS IN AN IMPOUNDED MIDDLE ROCKIES RIVER SYSTEM Impoundments influence water temperature in their outflowing waters, potentially altering species dispersal, community structure, and ecological productivity. This study aims to improve understanding of the interaction between reservoir management and tailwater temperatures. We examined summertime temperature patterns in a mid-size irrigation storage reservoir, Island Park Reservoir (IPR) and its tailwater, the Henry’s Fork of the Snake River, in East Idaho. Seventeen years of climatic, hydrologic, and management-related variables were examined to identify predictors of interannual variation in mean tailwater temperatures. Temperatures were best predicted by reservoir draft. Every 1x10^6 cubic meters of water passed through IPR dam resulted in a 0.016°C increase in water temperature in the tailwater. Examination of two years of weekly in-reservoir thermal profiles provided a potential mechanistic explanation; high reservoir draft eliminates cool hypolimnetic water in the reservoir, allowing warm epilimnetic water into the tailwater, increasing tailwater temperature. Reservoir draft is controlled by downstream irrigation water rights holders. Thus, irrigation, which can depend on a variety of climate and weather-related factors occurring far from our study system, can influence river water temperature patterns, a key variable controlling ecological processes.

John McLaren (Primary Presenter/Author), Utah State University, jacksmclaren@gmail.com;


Todd V. Royer (Co-Presenter/Co-Author), Indiana University Bloomington, troyer@iu.edu;


Rob Van Kirk (Co-Presenter/Co-Author), Henry's Fork Foundation, rob@henrysfork.org;


Melissa Muradian (Co-Presenter/Co-Author), Henry's Fork Foundation, melissa@henrysfork.org;


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5/21/2018  |   15:00 - 15:15   |  420 A

METABOLIC REGIMES OF THE SUSQUEHANNA RIVER: CONTROLS ON VARIABILITY AT DIFFERENT TEMPORAL SCALES We explored metabolic regimes of two 7th order rivers, West and North Branches of the Susquehanna River (WBSR, NBSR) in central Pennsylvania using data collected over eight years. Inverse modeling was used to select daily rates of gross primary production (GPP), respiration (ER), and reaeration (K) that produced the best statistical fit between modeled and measured diel oxygen data. Our data yielded over 2000 metabolism days for each river, which enabled us to analyze annual metabolic regimes for both rivers. Harmonic series showed periodicity in GPP over 730 days, 121 days, and 81 days in WBSR and over 365 days, 91 days, and 66 days in NBSR. ER showed aseasonal periodicity in both rivers. Periodicity in metabolism at different time scales was related to short-term hydrologic disturbances, seasonal patterns in hydrology, temperature, and light availability, and interannual hydrologic differences (i.e. wet years vs. dry years). Overall, net ecosystem production (NEP) was positive in WBSR but negative in NBSR. Despite being similar in size, these rivers might be acting differently with respect to atmospheric CO₂ and could represent the metabolic transition from net autotrophic to net heterotrophic river reaches.

Matthew McTammany (Primary Presenter/Author), Bucknell University, mmctamma@bucknell.edu;


Katharine Faulkner (Co-Presenter/Co-Author), Bucknell University, krf007@bucknell.edu;


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