WATER TENSION AND THE GREAT LAKES COMPACT Annin, Peter Ballroom ABC Monday, 18 May, 2015 09:15 - 10:00 This presentation delves into the long history of political maneuvers and water diversion schemes that have proposed sending Great Lakes water everywhere from Akron to Arizona. Through the prism of the past, this talk analyzes the future of Great Lakes water diversion management, which is now controlled by the Great Lakes Compact, a legal document released by the Council of Great Lakes Governors in December 2005. The Compact, which prohibits most Great Lakes water diversions, with limited exceptions, was adopted by the eight state legislatures in the Great Lakes region as well as the U.S. Congress before eventually being signed by the president in 2008. A similar agreement relating to Canadian water diversions was adopted by the province of Ontario in 2007 and Quebec in 2009. This presentation analyzes several noteworthy Great Lakes diversions that already exist, and sheds light on potential water diversions of the future, including the water diversion application submitted by Waukesha, Wisconsin in 2010. A decision on the Waukesha water diversion application is expected in late 2015 or early 2016. ALIEN ECOGEOMORPHOLOGY: IMPACTS OF AN INVADING ECOSYSTEM ENGINEER ON RIVER SEDIMENT DYNAMICS AND TROPHIC INTERACTIONS Rice, Stephen; Mathers, Kate; Johnson, Matthew; Wood, Paul; Reeds, Jake; Longstaff, Holly; Extence, Chris 101CD Monday, 18 May, 2015 10:30 - 10:45 Animals that dig burrows in river banks and beds are uncommon in the UK. The invasion of signal crayfish (Pacifastacus leniusculus), a prolific ecosystem engineer, has changed that, with implications for geomorphology, sediment dynamics and benthic ecology that benefit the invader. Burrowing directly introduces sediment to rivers and accelerates bank collapse, making substrates finer and increasing the quantity of sediment available for transport. In addition, energy expenditure by signals can mobilise sediment under incompetent hydraulic conditions. Field measurements in central England reveal suspended sediment fluxes that are partly driven by diel and seasonal variations in crayfish activity, with up to 50% of cumulative sediment load attributable to signals during summer low flows. These geomorphological impacts amplify the direct, ecological impacts of crayfish on benthic communities. For example, ex-situ experiments show that by limiting access to hyporheic refugia sedimentation constrains the avoidance (burrowing) behaviour of Gammarus pulex, increasing predation by signals. Alongside other ecogeomorphological interactions, crayfish-induced sedimentation may, therefore, extend the widely noted predatory effect of P. leniusculus on sessile taxa by rendering labile, burrowing macroinvertebrates relatively more vulnerable to predation. FURTHER DOWN THE RIVER : A NOVEL, SPECTROPHOTOMETRIC, IN-SITU TECHNOLOGY IMPROVING SPATIAL AND TEMPORAL DATA RESOLUTION TO ADDRESS HETEROGENEITY IN AQAUTIC SYSTEMS. Maxwell, Bryan 103C Monday, 18 May, 2015 10:30 - 10:45 Evaluating ecosystems requires understanding of the heterogeneity of such systems. Aquatic systems exhibit variability over space and time; seasonal and daily fluxes induce transient biogeochemical conditions, and spatial differences give rise to hot spots of activity. Biological activity of riverine and lacustrine environments can be assessed by observing nutrient uptake and transformation. Recent advances in field spectrophotometers were combined with inexpensive technology to produce an automated, programmable system capable of high frequency data at the space/time scale. The system utilizes multiple intake ports and is designed for use in field mesocosm studies to provide increased number of replicates and high confidence of results. Preliminary data shows high reliability in measuring nitrate, TN, COD, DOC, sulfate, and several metals. Tracking of additional parameters can be performed using simple PLSR methods. Present research with the developed system includes quantifying nitrogen uptake rates in a pre-restoration stream using in-situ, mesocosm drums. Findings include high data resolution showing seasonal change and spatial variability along the reach in N-uptake rates. FRESHWATER FUTURES: ECOSYSTEM SERVICES, MULTIDISCIPLINARY APPROACHES, AND HOW FUTURE STREAM ECOLOGISTS CAN HELP SAVE THE WORLD Dodds, Walter 101A Monday, 18 May, 2015 10:30 - 10:45 Freshwater is an essential resource for humanity and provides key habitat for much threatened biodiversity. The services that freshwater ecosystems provide humans are very diverse ranging from water quantity and quality, to biodiversity and cultural and recreational values. People also influence freshwater systems in a wide variety of ways. Stream ecologists in particular have a holistic view based on the reality of streams being driven by their watersheds. This view demands a multidisciplinary approach if we are to conserve and protect freshwaters. In the anthropocene we are under unique conditions driven by global change. In this context, societal factors interface with physical, chemical, geomorphologic, hydrologic, organismic, population, community, ecosystem, landscape and macroscale features of freshwaters. We have unprecedented tools to study freshwaters (advance analytical, molecular, big data approaches) at just the time when decisive action by humanity is required to preserve these systems. Future stream ecologists can thus make the world a better place by helping us toward a predictive understanding of streams and rivers, and the lakes, wetlands, groundwater and marine habitats they link to. FRESHWATER MUSSELS INCREASE SEDIMENT DENITRIFICATION IN AN URBAN RIVER Hoellein, Timothy; Zarnoch, Chester; Bruesewitz, Denise 102C Monday, 18 May, 2015 10:30 - 10:45 Freshwater mussel (Unionidae) beds are biogeochemical ‘hotspots’ in lotic ecosystems. Other bivalves with dense colonies (e.g., zebra mussels, Asian clam, oysters) enhance conditions required for denitrification, or the anaerobic reduction of nitrate to nitrogen gas, a loss of nitrogen (N) from the aquatic environment. Unionid’s role in denitrification is unknown. In summer 2014, we measured density, assimilation, and sediment N cycling effects of Lasmigona complanata (white heelsplitter) and Pyganodon gradis (giant floater) in the DuPage River’s East Branch near Chicago, Illinois, USA. We completed streamside measurements of feeding and biodeposition, and flow-through mesocosms with 15N tracers (as ammonium and nitrate separately) with live mussels in the laboratory. Both taxa significantly increased nitrate uptake and denitrification relative to sediment alone. Feeding rates were similar between mussel species, however, N biodeposition was greater in L. complanata. We calculated the economic value of mussel-mediated denitrification as an ecosystem service using well-established methods for oysters. Overall, freshwater mussels enhanced denitrification despite eutrophic conditions, and their contribution to N removal as an ecosystem service may represent an underutilized conservation tool for this widely imperiled taxon. IMPROVED METHODS FOR WEIGHTING SPECIES DISTRIBUTION MODELS TO IMPROVE ENSEMBLE MODEL PREDICTIONS Wenger, Seth; Som, Nicholas 101B Monday, 18 May, 2015 10:30 - 10:45 It has become increasingly common to make species distribution predictions and forecasts from ensembles of multiple models. Methods for weighting competing models have lagged, however, and the prevailing approaches are either to weight models equally or to use simple decay functions. We present a general approach to model weighting that more accurately preserves the relative differences in performance of alternative models. It involves (1) creating numerous bootstrapped datasets from the original dataset; (2) running each model on each dataset; and (3) recording the proportion of times each model is selected as “best” for a dataset using a given performance criterion. This proportion is the model weight. We illustrate the approach with a set of species distribution models built from large trout dataset. The R functions to implement the method are freely available and will soon be adapted into a formal package. SPATIAL SCALE VARIATION IN TOP-DOWN EFFECTS Garcia, Erica; Lacksen, Katherine; McMaster, Damien ; King, Alison; Douglas, Michael 102DE Monday, 18 May, 2015 10:30 - 10:45 Most experiments examining top-down (consumer) control in stream ecosystems have focussed on only a single spatial scale, frequently < 1 m². The strength of top-down control is known to be context dependent and may vary with spatial scale. We conducted a 40 day consumer manipulation experiment (i.e. fish and shrimp removal) at the patch scale (1 m² exclusion cages) and at the reach scale (whole-reach exclusions ~20 m length), with the aim of examining top-down effects at multiple scales within three streams in the wet/dry tropics of northern Australia. At the reach scale strong top-down effects on benthic algal biomass and macroinvertebrate density were observed, with evidence of a trophic cascade. However, at the patch scale there was no evidence of top-down effects. Our findings suggest that whilst most top-down experiments are conducted at small spatial scales they may yield misleading results if interpolated to larger scales. REGULATION AND RESULTS: BIOTIC AND ABIOTIC CHANGES TO NORTHEASTERN LAKES FOLLOWING TIGHTENING OF AIR EMISSIONS RULES McDowell, William G.; Webster, Katherine; Nelson, Sarah; McDowell, William H.; Haney, James 102B Monday,