Monday, May 18, 2015
15:30 - 17:00

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15:30 - 15:45: / 102DE PRIMARY PRODUCTIVITY REDUCES METHYLMERCURY BIOACCUMULATION IN EXPERIMENTAL STREAM FOOD WEBS

5/18/2015  |   15:30 - 15:45   |  102DE

PRIMARY PRODUCTIVITY REDUCES METHYLMERCURY BIOACCUMULATION IN EXPERIMENTAL STREAM FOOD WEBS Competing hypotheses posit that increasing primary productivity should result in either greater or lesser contaminant accumulation in stream food webs. We conducted an experiment to evaluate primary productivity effects on MeHg accumulation in stream consumers. We varied light for sixteen artificial streams creating a productivity gradient (oxygen production = 0.048 – 0.71 mg oxygen/L/d) among streams. Two-level food webs were established consisting of phytoplankton/filtering clam, periphyton/grazing snail, and leaves/shredding amphipod (Hyalella azteca). Methylmercury removal from the water column increased significantly with productivity. Phytoplankton and periphyton biomass increased significantly across the productivity gradient, but MeHg concentrations per unit chlorophyll-a declined. Methylmercury in clams and snails also declined with productivity, and consumer concentrations were strongly correlated with primary producer concentrations. Heterotroph biomass on leaves, MeHg in leaves, and MeHg in Hyalella were unrelated to stream productivity. Our results support the hypothesis that contaminant accumulation declines with stream primary production via the mechanism of bloom dilution (MeHg burden per cell decreases in algal blooms), extending patterns of contaminant accumulation documented in lakes to lotic systems.

David Walters (POC,Primary Presenter), United States Geological Survey, waltersd@usgs.gov;
Dr. David Walters is a Supervisory Research Ecologist at the Columbia Environmental Research Center. David has been a research ecologist with the USGS since 2008. Prior to that, he was an ecologist for the U.S. EPA, National Exposure Research Laboratory for 6 years. He is a freshwater ecologist with broad training in stream ecology, human impacts on aquatic ecosystems, and ecotoxicology. His current research topics include food webs and contaminant flux, aquatic-riparian linkages, stream fish ecology, land use and climate change, and invasive species.

David Raikow (Co-Presenter/Co-Author), National Park Service, david_raikow@nps.gov;


Chad Hammerschmidt (Co-Presenter/Co-Author), Wright State University, chad.hammerschmidt@wright.edu;


Molly Mehling (Co-Presenter/Co-Author), Chatham University, mmehling@chatham.edu;


Amanda kovach (Co-Presenter/Co-Author), GEI Consultants, akgevertz@gmail.com;


James Oris (Co-Presenter/Co-Author), Miami University, orisjt@miamioh.edu;


15:45 - 16:00: / 102DE OBSERVATIONS ON VARIABILITY IN SELENIUM BIOACCUMULATION RATES AND IMPLEMENTATION OF TISSUE CRITERIA

5/18/2015  |   15:45 - 16:00   |  102DE

OBSERVATIONS ON VARIABILITY IN SELENIUM BIOACCUMULATION RATES AND IMPLEMENTATION OF TISSUE CRITERIA Chronic tissue criteria for selenium are under consideration nationally and being developed in West Virginia. Implementation of tissue criteria raises many questions with regard to monitoring and attainment of the chronic criterion such as when sampling should occur, which sexes should be included in the monitoring, number of fish included, and whether samples should be composited. Bioaccumulation varies within different ranges of water column concentrations which may affect variability and thus monitoring strategy. To provide insights into these questions, fish were collected monthly for a year at three sample sites with varying concentrations in the mining region of West Virginia. Significant differences between male and female selenium concentrations were only found in the spring season. This season is unfavorable for monitoring due to spawning season however it also corresponds to the highest selenium concentrations for both male and female fish. Fall and winter had the significantly lower selenium concentrations in fish tissue with spring concentrations being intermediate. Sample sizes necessary to approximate the distribution of larger datasets will be presented along with comparisons of composite and individual sampling.

Mindy Yeager-Armstead Ph.D. (Co-Presenter/Co-Author), Marshall University, m.armstead@marshall.edu;


Mandee Wilson M.S. (Primary Presenter/Author), Marshall University, m.wilson@marshall.edu;


Lorin Kinney M.S. (Co-Presenter/Co-Author), Marshall University, keller39@live.marshall.edu;


16:00 - 16:15: / 102DE EXPERIMENTAL MIXING OF A NORTH-TEMPERATE LAKE: EXAMINATION OF VARIABILITY IN SPATIAL AUTOCORRELATION IN FISH AND ZOOPLANKTON POPULATIONS

5/18/2015  |   16:00 - 16:15   |  102DE

EXPERIMENTAL MIXING OF A NORTH-TEMPERATE LAKE: EXAMINATION OF VARIABILITY IN SPATIAL AUTOCORRELATION IN FISH AND ZOOPLANKTON POPULATIONS Thermal stratification and twice-yearly mixing of freshwater lakes structure physical habitats, affect the rate of chemical and biological processes, influence phenology and distribution of aquatic animals, and drive predator-prey interactions. Because of the far-reaching and complex nature of thermal stratification, whole-ecosystem manipulations are essential to understanding abiotic and biotic interactions that regulate aquatic ecology. The Crystal Lake Mixing Project (Vilas County, WI) has successfully mixed an entire lake, creating an environment to study effects of destratification on spatial distributions of fish and zooplankton before (2010-2011), during (2012-2013), and after (2014) mixing. This manipulation may aid in understanding processes that structure spatial heterogeneity that may in turn drive distributions of fish and zooplankton, and also yield insight on the more general question of how patterns of biotic aggregations respond to disturbance regimes. We will examine changes in spatial autocorrelation of fish and zooplankton using cokriging and variograms to test hypotheses that bottom up or top down mechanisms drive spatial patterns in predator and prey distributions from 2010-2014, and whether mixing alters patterns observed during the pre-manipulation phase of the experiment.

Emily Heald (Primary Presenter/Author), University of Minnesota Duluth, heald007@umn.edu;


Zach J. Lawson (Co-Presenter/Co-Author), Wisconsin Department of Natural Resources, zlawson@wisc.edu;


Thomas R. Hrabik (Co-Presenter/Co-Author), University of Minnesota Duluth, thrabik@d.umn.edu;


Jake M. Vander Zanden (Co-Presenter/Co-Author), University of Wisconsin Madison, Center for Limnology, mjvanderzand@wisc.edu;


Stephen R. Carpenter (Co-Presenter/Co-Author), University of Wisconsin Madison, Center for Limnology, srcarpen@wisc.edu;
Stephen Russell (Steve) Carpenter is a leader of whole-ecosystem experiments and adaptive ecosystem management focused on freshwaters. Topics include trophic cascades and their effects on production and nutrient cycling, contaminant cycles, freshwater fisheries, eutrophication, nonpoint pollution, ecological economics of freshwater, and resilience of ecosystems and social-ecological systems. Carpenter serves as the Director of the Center for Limnology at the University of Wisconsin-Madison, where he is the Stephen Alfred Forbes Professor of Zoology. He is a member of the U.S. National Academy of Sciences, a Fellow of the American Academy of Arts and Sciences, and a foreign member of the Royal Swedish Academy of Sciences. Carpenter is the 2011 laureate of the Stockholm Water Prize. Other notable awards include a Pew Fellowship in Conservation and Environment, the G. Evelyn Hutchinson Medal of the American Society of Limnology and Oceanography, the Robert H. MacArthur Award from the Ecological Society of America, the Excellence in Ecology Prize from the Ecology Institute, and the Naumann-Thienemann medal of the International Society for Limnology. Carpenter is Chair of the Science Committee for the Program on Ecosystem Change and Society of the International Council of Science. He is co-Editor in Chief of Ecosystems, and a member of governing boards for the Beijer Institute of Ecological Economics and the South American Institute for Resilience and Sustainability Studies. Carpenter is a fellow of the Ecological Society of America, and founding member and Fellow of the Resilience Alliance. From 2000-2005 he served as co-chair of the Scenarios Working Group of the Millennium Ecosystem Assessment. He led the North Temperate Lakes Long-Term Ecological Research program at U.W.-Madison from 1999-2009. He is a former President of the Ecological Society of America. Carpenter has published 5 books and more than 300 scientific papers, book chapters, reviewed reports and commentaries. He received a B.A. from Amherst College (1974), M.S. from University of Wisconsin-Madison (1976), and Ph.D. from U.W. Madison (1979). From 1979-1989 he served as Assistant and then Associate Professor at the University of Notre Dame. He joined the U.W.-Madison faculty in 1989. A full biographical sketch, publication list and contact information are posted on http://limnology.wisc.edu/personnel/carpenter/.

16:15 - 16:30: / 102DE WHY IS PHYTOPLANKTON PRODUCTION AND ZOOPLANKTON BIOMASS LOWER IN HUMIC LAKES?

5/18/2015  |   16:15 - 16:30   |  102DE

WHY IS PHYTOPLANKTON PRODUCTION AND ZOOPLANKTON BIOMASS LOWER IN HUMIC LAKES? Small oligotrophic humic lakes are the most numerous type of lake in the boreal zone and will become more abundant as a consequence of climate change. Consequently, it is important to assess why oligotrophic humic lakes have lower primary and secondary production than their clear water counterparts. To determine why humic lakes are less productive than clear water lakes, we compared food quantity and quality measures in four humic and four clear water lakes over a growing season. Food quantity was twice as high in clear water compared to humic lakes, although food quality was higher in humic lakes. Reduced light, light:nutrient supply ratios and lower temperatures were the primary factors limiting phytoplankton production and phytoplankton taxon richness in humic lakes. Zooplankton biomass and taxon richness were positively related to temperature, total nitrogen and phytoplankton production and richness, rather than measures of food quality. Overall, light availability was the most important determinant of phytoplankton production and species diversity, which resulted in differences in zooplankton biomass and species diversity between boreal humic and clear water oligotrophic lakes.

Carolyn Faithfull (Primary Presenter/Author), Umeå University, carolyn.faithfull@emg.umu.se;


Ann-Kristin Bergström (Co-Presenter/Co-Author), Umeå University, ann-kristin.bergstrom@emg.umu.se;


Anne Deininger (Co-Presenter/Co-Author), Umeå University, anne.deininger@emg.umu.se;


16:30 - 16:45: / 102DE UNDERSTANDING POTENTIAL CHANGES IN TROPHIC RELATIONSHIPS USING STABLE ISOTOPES RATIOS FOLLOWING EXTREME RESERVIOR DRAWDOWN

5/18/2015  |   16:30 - 16:45   |  102DE

UNDERSTANDING POTENTIAL CHANGES IN TROPHIC RELATIONSHIPS USING STABLE ISOTOPES RATIOS FOLLOWING EXTREME RESERVIOR DRAWDOWN Highly variable and complex food web responses may result from extreme drawdowns of reservoirs. We examined trophic relationships in two reservoirs in the Oregon Cascades with similar community compositions following an extreme drawdown of one reservoir to brief lotic conditions. We hypothesized that in-reservoir food webs and their productivity would show cascading trophic effects following exports of nutrients and taxa downstream; we sampled physical, chemical and biological conditions during summer and fall and analyzed stable isotope ratios of nitrogen, carbon, and sulfur for the food webs. We found a lower maximum nitrogen isotopic ratio in the treatment reservoir, suggesting a shorter food web length that coincided with lower light transmission and a shallower thermocline. Whereas fishes known to be planktivorous had similar isotopic ratios, suspected piscivores were different between the two reservoirs. Our findings could be consistent with either top down or bottom up influences. The extreme drawdown exports many fishes downstream, reducing abundance within the reservoir. Under such conditions, generalist predators may be switching their diets from piscivory to the remaining and more abundant prey (e.g. zooplankton).

Christina A. Murphy (Primary Presenter/Author), U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME, christina.murphy@maine.edu;
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Ivan Arismendi (Co-Presenter/Co-Author), Oregon State University, Department of Fisheries & Wildlife, ivan.arismendi@oregonstate.edu;


Sherri Johnson (Co-Presenter/Co-Author), U.S. Forest Service, Pacific Northwest Research Station, sherrijohnson@fs.fed.us;


16:45 - 17:00: / 102DE THE IMPACTS OF REDUCED STREAM FLOW ON FOOD WEBS IN STREAMS ON THE ISLAND OF HAWAII

5/18/2015  |   16:45 - 17:00   |  102DE

THE IMPACTS OF REDUCED STREAM FLOW ON FOOD WEBS IN STREAMS ON THE ISLAND OF HAWAII Stream flow in Hawaii and throughout the tropics is currently threatened by reduced precipitation due to climate change. However, little is known of how aquatic macroinvertebrates are responding to these changes. Decreased stream flow can reduce body condition and reproductive output of native ‘opae shrimp (Atyoida bisulcata) in streams on Hawaii Island, but the underlying mechanisms leading to these changes have yet to be identified. I am comparing the diets of three different aquatic macroinvertebrates in five streams along a rainfall gradient (3000-7000 mm/year) on the North Hilo Coast of Hawai’i Island. Stable isotope signatures (?13C and ?15N) from consumers and dominant food resources are used to solve mixing models that are used to compare consumer diets between streams. Carbon/nitrogen (C:N) ratios of the food resources are weighted with their individual annual biomasses (g/m2) and then averaged to demonstrate if and how relative abundances and quality of food resources differ across the stream flow gradient, and whether the diets of the consumers reflect a response to these potential differences.

Michael Riney (Primary Presenter/Author), USDA Forest Service and The University of Hawaii at Hilo, mriney@hawaii.edu;


Charlie Yak (Co-Presenter/Co-Author), University of Papua New Guinea, aleifreddie@gmail.com;


Rebecca Ostertag (Co-Presenter/Co-Author), The University of Hawaii at Hilo, ostertag@hawaii.edu;


Ralph Tingley (Co-Presenter/Co-Author), Missouri Cooperative Fish and Wildlife Research Unit, tingleyr@msu.edu;


Therese C. Frauendorf (Co-Presenter/Co-Author), University of Victoria, tfrauend@uvic.ca;