5/22/2016  |   10:30 - 10:45   |  313

WHAT PHYSIOLOGICAL RESEARCH ON ION TRANSPORT SUGGESTS ABOUT THE POTENTIAL TOXICITY OF SULFATE Bioassays have purported to measure sulfate (SO₄^2-) toxicity in freshwater animals. Some studies have related this toxicity to hardness. However, considering ion transport physiology, attributing this toxicity to SO₄^2- is questionable. SO₄^2- is relatively impermeant to external epithelial membranes. SO₄^2- transporters occur in the renal system and are involved in reabsorption and maintenance of greater serum SO₄^2-. In these bioassays, Na₂SO₄ is used to increase SO₄^2- concentrations, so Na⁺ and SO₄^2- are increased but not other ions. Research with euryhaline crabs suggests similar toxic effects are related to a decreased water K⁺:Na⁺ concentration ratio, affecting ionic balance in intra- and extra-cellular fluids. Increased Na⁺ may also alter acid-base regulation, because the Na⁺ gradient decreases but not Cl^-. Hardness is known to decrease the toxicity of divalent metals, because metal ions and Ca²⁺ compete for Ca²⁺ transporters. Consequently, increased Ca²⁺ inhibits metal uptake. No similar mechanism can explain a hypothesized relationship between hardness and SO₄^2- toxicity. The views expressed are those of the author and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency.

Michael Griffith (Primary Presenter/Author), U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement and Modeling, Cincinnati, OH 45268, griffith.michael@epa.gov;


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5/22/2016  |   10:45 - 11:00   |  313

ENVIRONMENTAL FACTORS ASSOCIATED WITH BENTHIC COMMUNITY DEGRADATION ALONG A GRADIENT OF CONTAMINATION IN ACID MINE DRAINAGE-EXPOSED LAKES The Lake Dasserat system in western Quebec exhibits a marked spatial gradient of pH and metal concentrations in water and sediment after over 70 years exposure to drainage from an abandoned Cu-Zn mine site. In a recovery from impacts study, benthic macroinvertebrate communities in sediment from across the gradient were assessed in relation to distance to the inflow from the mine site, water quality, and sediment conditions. Total benthos and taxon richness increased, and community composition changed, with distance to the inflow from the mine. Low dissolved oxygen in overlying water accounted for exceptions to the pattern. Community impoverishment was associated with low pH, high conductivity, and high sediment organic content (likely sourced from the mine site), and depth, which was inversely related to dissolved oxygen level. Among 35 metals and metalloids, Tl, Pt, Cu, Sr, Pb, Zn, Sb and Fe were the most associated with community impoverishment. Although these contaminants were too correlated to indicate potential causal relationships of individual metals based on spatial pattern, maximum Cu and Zn concentrations were markedly elevated above sediment quality guidelines.

Lee Grapentine (Primary Presenter/Author), Environment and Climate Change Canada, Lee.Grapentine@canada.ca;


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5/22/2016  |   11:00 - 11:15   |  313

STREAM BENTHIC AND ALGAL COMMUNITY RESPONSES TO HEAVY METALS: AN EVALUATION OF ENDPOINT SENSITIVITY Benthic macroinvertebrate community responses to heavy metals are often used to assess and predict ecological impairment, yet evaluation of aquatic insect adults and algal community responses have received less attention. I evaluated several macroinvertebrate and algal endpoints by exposing communities to mixtures of Cu and Zn for 14 d using stream mesocosms. I compared two stream communities in Colorado, the Arkansas River (AR) and the North Fork Clear Creek (NFCC). Measured responses included the number of emerging adults, algal community composition and biomass, community metabolism, and benthic community composition. Results show significant differences in larval and adult responses within the same taxonomic groups, particularly among midges (Chironomidae) and mayflies (Ephemeroptera); however, algal biomass and community metabolism displayed greater overall sensitivity to metals exposure. The relative sensitivity of the endpoints was also different among AR and NFCC, likely because of differences in their benthic composition and exposure histories. These results highlight the need to comprehensively assess exposure effects beyond larval macroinvertebrate life stages using endpoints that may respond differently, while acknowledging context-dependent responses resulting from different stream assemblages.

Christopher Kotalik (Primary Presenter/Author), United States Geological Survey, ckotalik@usgs.gov;


William Clements ( Co-Presenter/Co-Author), Colorado State University, William.Clements@colostate.edu ;


Pete Cadmus ( Co-Presenter/Co-Author), Colorado Parks and Wildlife, pete.cadmus@state.co.us;


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5/22/2016  |   11:15 - 11:30   |  313

ARSENIC DYNAMICS AT THE BASE OF AQUATIC FOOD WEBS Arsenic is a widespread environmental contaminant in freshwater ecosystems. The behavior of arsenic in freshwater food webs is complex with both geochemical and biological processes influencing chemical speciation and bioavailability. We used a radiotracer approach to quantify 73-As bioconcentration into periphyton. Exposed in a single 8-day arsenate pulse, periphyton concentrated As 3000-9000 -fold higher than the dissolved concentrations. Arsenate uptake rates into periphyton were also found to be pH dependent. Because many trace elements bioconcentrate in periphyton and can be transferred trophically, we used 73-As labeled periphyton as a food source for benthic invertebrate grazers. The mayfly Neocloeon triangulifer was raised on labeled periphyton from hatchling to adulthood. As concentrations in mature larvae were quite low, and no label was detected in adults. We estimated the dietary assimilation efficiency of As from periphyton to be 22.2±8.5% while aqueous uptake rates were too low to be quantified. Dietary assimilation efficiencies ranged from 28% to 75% across 4 other benthic grazers. These assimilation efficiencies are low to modest relative to other trace elements. Arsenic speciation work in periphyton will also be presented.

David Buchwalter (Primary Presenter/Author), North Carolina State University, david_buchwalter@ncsu.edu;


Adeline Lopez ( Co-Presenter/Co-Author), North Carolina State University, arharri9@ncsu.edu;


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5/22/2016  |   11:30 - 11:45   |  313

BIOFILM ROLE IN AN ARSENIC-POLLUTED RIVER In the arsenic biogeochemical cycle, microorganisms may affect arsenic toxicity by changing its speciation. Gold mining activities in fluvial systems may cause arsenic pollution, as in Anllóns River (Galicia, NW Spain), where high concentrations in surface sediments (up to 270mg/kg) were found. A 51 days-long biofilm-translocation experiment was done in the Anllóns River, moving from a less to a more polluted site, to explore the effect of epilithic biofilm on arsenic retention and speciation in the water-sediment interface. Eutrophic conditions were detected at both sites. Translocated biofilms accumulated more arsenic and their growth was reduced to half that observed in not-translocated. Methylated As-species (DMAV) were found in intracellular biofilm compartment, what may suggest a detoxification process by biofilm (methylation). Detection of DMAV in water may indicate that biofilm contributes to arsenic speciation in the interface water-epilithic biofilm. Moreover, arsenate (AsV) reduction by biofilm may be confirmed by the high amount of arsenite (AsIII) detected in its extracellular compartment. Our study provides new arguments for the understanding of the key role of microorganisms in the arsenic biogeochemical cycle in freshwater environments.

Laura Barral-Fraga (Primary Presenter/Author), Institute of Aquatic Ecology, Department of Environmental Sciences, University of Girona, Spain, laura.barral.fraga@gmail.com;


Diego Prieto ( Co-Presenter/Co-Author), Department of Soil Science and Agricultural Chemistry, Faculty of Pharmacy, Universidade de Santiago de Compostela (Spain), diego.martina@usc.es;


María Teresa Barral ( Co-Presenter/Co-Author), Department of Soil Science and Agricultural Chemistry, Faculty of Pharmacy, Universidade de Santiago de Compostela (Spain), mteresa.barral@usc.es;


Helena Guasch ( Co-Presenter/Co-Author), Center for Advanced Studies of Blanes (CEAB-CSIC), Spain, helena.guasch@ceab.csic.es;


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5/22/2016  |   11:45 - 12:00   |  313

INFLUENCES OF ARSENIC ON FRESHWATER BIOFILMS, FISH AND THEIR NUTRIENT CYCLING INTERACTIONS A simplified fluvial system including fish, periphyton and sediment was used to investigate the fate and effects of an environmentally realistic concentration of arsenic on biofilm, fish and their nutrient cycling interactions. Total dissolved arsenic concentration decreased from 120 µg/L to 28.0±1.5 µg/L during the experiment (60 days), being mostly retained by the sediment and accumulated in the periphytic biofilm. Most P and N was also retained in the epipsammic biofilm. Exposure to this concentration of arsenic under oligotrophic conditions influenced the contribution of biofilms to nutrient cycling, and its ability to oxygenate the aquatic environment. Arsenic effects on superoxide dismutase (SOD) and glutathione reductase (GR) activities in the liver of mosquitofish were ameliorated in the presence of biofilms at the beginning of exposure. By the end of the experiment, catalase activity (CAT) in the liver increased but the arsenic-affected biofilm had no influence over toxicity since it had lost its role in water purification. Our results indicate that the effects of toxicants may be higher than expected if some of the complexity of natural systems is incorporated.

Baigal-Amar Tuulaikhuu (POC,Primary Presenter), 1 Institute of Aquatic Ecology, Department of Environmental Sciences, University of Girona, Spain; 2 Department of Ecology, School of Agroecology, Mongolian University of Life Sciences, baigal.tuulaikhuu@udg.edu;


Anna M. Romaní ( Co-Presenter/Co-Author), Institute of Aquatic Ecology, University of Girona, Campus de Montilivi, 17003 Girona, Spain., anna.romani@udg.edu;


Berta Bonet ( Co-Presenter/Co-Author), University of Girona, berta.bonet@udg.edu;


Laura Barral-Fraga ( Co-Presenter/Co-Author), Institute of Aquatic Ecology, Department of Environmental Sciences, University of Girona, Spain, laura.barral.fraga@gmail.com;


Kit Magellan ( Co-Presenter/Co-Author), Institute of Aquatic Ecology, Department of Environmental Sciences, University of Girona, Spain, kit8x@hotmail.com;


Helena Guasch ( Co-Presenter/Co-Author), Center for Advanced Studies of Blanes (CEAB-CSIC), Spain, helena.guasch@ceab.csic.es;


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