6/05/2017  |   14:15 - 14:30   |  302B

Carbon Sources in Riverine Food Webs: New Evidence from Amino Acid Isotope Techniques A nearly 40 yr debate on the origins of carbon supporting animal production in lotic systems has spawned numerous conceptual theories. Testing theories has been hampered by lack of adequate analytical methods to distinguish in consumer tissue between ultimate autochthonous and allochthonous carbon. The newest technique in amino acid, compound specific, stable isotope analysis (AA-CSIA), however, enables investigators to link consumers to food sources by tracing essential amino acids from producers to consumers. We used AA-CSIA to evaluate nutrient sources for 5 invertivorous and 6 piscivorous species in 2 hydrogeomorphically contrasting large rivers: the anastomosing Upper Mississippi River (UMR) and the mostly constricted lower Ohio River (LOR). Our results demonstrate that on average algae contributed 58.5% (LOR) to 75.6% (UMR) of fish diets. The next highest estimated contributions of food sources were from C3 terrestrial plants (21.1 and 11.5% for the LOR and UMR, respectively). Moreover, results from 11 individually examined species consistently demonstrated the importance of algae for most fish species in these trophic guilds. Differences among rivers in relative food source availability resulting from contrasting hydrogeomorphic complexity may account for relative proportions of amino acids derived from algae.

Rachel Bowes (Primary Presenter/Author), University of Kansas, Kansas Biological Survey, rebowes@ku.edu;


James H. Thorp ( Co-Presenter/Co-Author), University of Kansas/Kansas Biological Survey, thorp@ku.edu;


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6/05/2017  |   14:30 - 14:45   |  302B

PHOSPHORUS RETENTION AND RELEASE BY RESERVOIRS OF A EUTROPHIC RIVER Reservoirs can be either net sinks or sources of phosphorus (P) in river systems. We examined summer P balances in two reservoirs, Morrow Lake and Lake Allegan, on the Kalamazoo River in Michigan (USA). These run-of-river reservoirs are amenable to mass balances because they have single inflows and essentially no other P inputs. During the summer, Morrow Lake fluctuated between being a net source of P (8 of 16 years) and a net sink (8 of 16 years), and was a source of P when mean water residence time exceeded ~3.5 days. Lake Allegan was a source of P during the summer and, for one year when samples were collected all year, a sink during the winter; P inflow was similar to outflow on an annual basis. During the summer, nitrogen may have limited algal growth, thereby reducing P uptake and further contributing to net P release. The effects of these reservoirs on P transport are controlled by water residence time and the balance between sedimentation of particulate P and sediment P release, with the latter important at low flows and warm temperatures.

Sarah S. Roley (Primary Presenter/Author), Michigan State University, roleysar@msu.edu;


Stephen K. Hamilton ( Co-Presenter/Co-Author), Michigan State University & Cary Institute of Ecosystem Studies, hamilton@kbs.msu.edu;


Dustin Kincaid ( Co-Presenter/Co-Author), W.K. Kellogg Biological Station and Department of Integrative Biology, Michigan State University, kincai32@msu.edu;


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6/05/2017  |   14:45 - 15:00   |  302B

THE IMPORTANCE OF BIOTIC INTERACTIONS IN SHAPING LARGE RIVER ASSEMBLAGES: ZOOPLANKTON RESPONSES TO THE ARRIVAL AND SUBSEQUENT CONTROL AND REDUCTION OF ASIAN CARP Zooplankton are a critical structural and functional component of riverine communities and food webs. While obligate and facultative planktivores are common components of riverine assemblages, the arrival and rapid expansion of invasive and planktivorous Asian carps has resulted in an extremely large shift in both the species, size, and amount of plankton in the Illinois River and other tributaries of the Mississippi basin. The potential negative ramifications of further spread to other basins like those of the Great Lakes is so great that a wide variety of intensive control efforts, including removal via commercial fishing, have been instituted. In addition to reducing the potential for further spread, there is a hope that the impacts on the river ecosystem can also be reversed. We will present results of the first 5 years of Asian carp removals on native plankton and planktivorous fish: rotifers respond positively and more quickly the macro-zooplankton and while in general planktivore condition (Bigmouth Buffalo and Gizzard shad) is still lower than pre-Asian carp, there is evidence that accelerating removal efforts can have a positive effect.

Andrew Casper (Primary Presenter/Author), Illinois Natural History Survey, afcasper@illinois.edu;


Alison Anderson ( Co-Presenter/Co-Author), Illinois Natural History Survey, Illinois River Biological Station, amander@illinois.edu;


Brian Zalay ( Co-Presenter/Co-Author), Illinois Natural History Survey, Illinois River Biological Station, bzalay2@illinois.edu;


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6/05/2017  |   15:00 - 15:15   |  302B

BIOPHYSICAL CONTROLS ON TERRESTRIAL-AQUATIC LINKAGES: TRANSFER AND RETENTION OF LEAF LITTER IN A LARGE RIVER Terrestrial leaf litter inputs are valuable sources of energy in lotic ecosystems. While these linkages are well understood in small streams, many contemporary models consider allochtonous leaf litter to be of little importance in large rivers due to riparian-stream spatial separation and low in-stream retention. However, these models tend to overlook the influence of biophysical processes on litter transport and in-stream retention, ultimately enhancing large river terrestrial-aquatic linkages. Using a large river (5th order) in Southern Alberta, we designed a series of experiments and models to evaluate the effects of biophysical processes in the transport and retention of leaf litter. First, we modeled leaf litter transport for three dominant taxa of Populus spp. using varying wind conditions and riparian forest canopy characteristics. Secondly, we tested the effects of flow on litter retention using an in-stream leaf release experiment. Our results indicate that local wind speed, riparian vegetation structure, and flow characteristics strongly govern the availability of leaf litter subsidies to aquatic ecosystems. Thus, spatio-temporal variability of biophysical conditions should be considered when evaluating terrestrial-aquatic linkages in larger rivers.

Trent Hoover ( Co-Presenter/Co-Author), University of Lethbridge, trent.hoover@uleth.ca;


Samuel Woodman ( Co-Presenter/Co-Author), University of Lethbridge, samuel.woodman@uleth.ca;


Stewart Rood ( Co-Presenter/Co-Author), University of Lethbridge, rood@uleth.ca;


David Tavernini (Primary Presenter/Author), University of British Columbia, taverninid@gmail.com;


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6/05/2017  |   15:15 - 15:30   |  302B

INFLUENCES OF DOWNRIVER CONNECTIVITY AND SITE CONDITIONS ON RICHNESS PATTERNS OF GREAT-RIVER FISHES WITHIN FREE-FLOWING TRIBUTARY NETWORKS Large tributaries are increasingly recognized as sources of supplemental habitat for fish species in mainstems of major river basins (Great-River Specialists [GRS]). Besides coarse relationships between richness and river size, little is known about the influences of connectivity and local habitat on distributional patterns within tributary networks. In 2016 we surveyed 22 sites throughout two 7th-order tributaries (Grand and Meramec rivers) of the Missouri and Mississippi rivers in Missouri. Fluvial distance to tributary mouth and multivariate dissimilarity between local and mainstem conditions served as indices for connectivity and longitudinal environmental gradients, respectively. We collected 29 of the potential 39 (74%) GRS in each region. Richness of GRS increased with river size within both systems (p < 0.05). Connectivity in the Grand River and environmental gradients within both rivers did not explain significant residual variation resulting from models between river size and richness; however, connectivity explained 55% of residual variation within the Meramec River. Results demonstrate varied mechanisms mediating the extent of tributary use by GRS and highlight the importance of regional connectivity for complementing known richness-river size relationships.

Corey Dunn (Primary Presenter/Author), Missouri Cooperative Fish and Wildlife Research Unit; University of Missouri-Columbia, cgd7n7@mizzou.edu;


Craig Paukert ( Co-Presenter/Co-Author), United States Geological Survey; Missouri Cooperative Fish and Wildlife Research Unit; University of Missouri-Columbia, paukertc@missouri.edu;


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6/05/2017  |   15:30 - 15:45   |  302B

IN RIVERS SEDIMENT SURFACE AREA IS GREATER IN THE WATER COLUMN THAN THE BENTHOS Ecosystem processes for large rivers are often scaled up based on measurements from small streams. However, there are fundamental differences in the properties of rivers and streams. For example, along a river continuum the water column may become the locus of activity for certain processes compared to the benthos. Beginning with the physical template, we quantified the ratio of sediment surface area in the water column versus the benthos (R_SA) with a simple model based on hydrogeomorphic principles. We used suspended sediment, discharge, and channel dimensions data from 10 major rivers as model input. We show that R_SA increased as a power function of watershed area and varied over six orders of magnitude (10^-4 to 10²; R_SA > 1 indicates greater sediment surface area in the water column than benthos). At median discharge, R_SA was eventually greater than 1 in all ten rivers; this location occurred in 6^th order rivers on average.

John Gardner (Primary Presenter/Author), Duke University, john.r.gardner@duke.edu;


Martin Doyle ( Co-Presenter/Co-Author), Duke University, martin.doyle@duke.edu;


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