5/18/2015  |   13:30 - 13:45   |  102B

EPITHELIAL ION TRANSPORTERS: A PHYSIOLOGICAL MODEL FOR ION EFFECTS ON FRESHWATER ANIMALS Ions in freshwater animals are regulated in part by uptake from water through ionocytes on the gills or other epithelia. A literature review suggests two mechanisms for adverse effects to freshwater animals by ionoregulation. First, elevated water concentrations of other ions that can pass through specific ion transporters competitively inhibit uptake of the primary ion. Divalent metals cross epithelia via Ca²⁺-transporters. Competitive inhibition of uptake occurs between these metals and Ca²⁺ and is the mechanistic basis of metal toxicity. Second, increased water concentrations of an ion can reduce its trans-epithelial concentration gradient inhibiting ion exchange. H⁺ and HCO₃^- are hydrolyzed from CO₂ and exchanged for Na⁺ and Cl^-, respectively. Elevated water H⁺ levels inhibit Na⁺ uptake in exchange for intracellular H⁺ resulting in internal Na⁺ depletion and toxicity. Similarly, elevated water HCO₃^- may inhibit Cl^- uptake in exchange for intracellular HCO₃^- resulting in Cl^- depletion. Understanding of these mechanisms underlies ion toxicity models. The views expressed in this abstract 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;

5/18/2015  |   13:45 - 14:00   |  102B

ALKYL POLYGLUCOSIDE-CONTAINING COMPOUND ALTERS PLANKTON COMMUNITY COMPOSITION IN BLACKWATER POND MESOCOSMS Synthetic surfactants in detergents and cleaners commonly contaminate freshwater systems. Therefore developing low-toxicity alternatives, such as alkyl polyglucosides (APGs), is important. Although APGs degrade rapidly and reduce chemical exposure time, biodegradation consumes oxygen. Blackwater systems in the southeastern U.S. frequently experience low dissolved oxygen (DO) conditions, making them particularly sensitive to adverse effects from oxygen-demanding chemicals. We hypothesized that APG-containing products adversely affect plankton communities via direct toxicity to algae and zooplankton, as well as through reduced water quality and food availability to zooplankton. Floating mesocosms (440 L) were deployed in a blackwater pond in Georgia, USA and dosed with 0, 0.01, 2.5, 5, or 10 mg L^-1 APG. DO concentration, phytoplankton abundance (as chlorophyll a), and zooplankton community composition were determined weekly for one month. Despite reductions in DO (4.4-12.4%) and chlorophyll a (24.6-81.1%) with increasing APG concentration, changes in the zooplankton community were likely due to APG toxicity. The decrease in zooplankton abundance was due to loss of copepods that shifted the community toward domination by cladocerans, suggesting differential sensitivity among zooplankton to APG under environmentally relevant conditions.

Steven Riera (Primary Presenter/Author), Georgia Southern University, sr01009@georgiasouthern.edu;


Risa A. Cohen (Co-Presenter/Co-Author), Georgia Southern University, rcohen@georgiasouthern.edu;

5/18/2015  |   14:00 - 14:15   |  102B

EFFECTS OF ROTENONE CONCENTRATIONS ON ZOOPLANKTON AND BENTHIC MACROINVERTEBRATES IN ALPINE LAKES AND STREAMS The piscicide rotenone is ubiquitously used in the restoration of native trout. However, studies of the impacts to non-target organisms have largely produced inconclusive results because of poor study design, failure to measure rotenone concentrations, and possible differential responses across taxa and habitats. We implemented a before-after-control-impact study design to quantify the effects of rotenone on non-target organisms in an alpine environment. We assessed the effects of rotenone on zooplankton in five lakes and benthic macroinvertebrates in six streams one week pre-treatment and one week, one month, and one year post-treatment for two years of rotenone treatments. Reponses of zooplankton and benthic macroinvertebrates differed among years, sites, and community metrics, with responses ranging from no response to 50% reductions in richness and 90% reductions in density persisting for at least one month post-treatment. Differences in rotenone concentrations and persistence explained up to 76% of the variability in richness but <15% of the variability in densities for both zooplankton and macroinvertebrates. Future research should further examine physical habitat influences on rotenone persistence and differential life history responses to rotenone treatments.

Jennifer Courtwright (Primary Presenter/Author), Utah State University National Aquatic Monitoring Center, jennifer.courtwright@usu.edu;


Scott Miller (Co-Presenter/Co-Author), BLM/USU National Aquatic Monitoring Center, Department of Watershed Sciences, Utah State University, scott.miller@usu.edu;


Chris Plunkett (Co-Presenter/Co-Author), US Forest Service, Ashley National Forest, cplunkett@fs.fed.us;

5/18/2015  |   14:15 - 14:30   |  102B

SALT IN OUR STREAMS: EVEN SMALL SODIUM ADDITIONS HAVE NEGATIVE EFFECTS ON DETRITIVORES Freshwater ecosystems are threatened by rising ion concentrations from agriculture, urbanization and resource extraction. Large, pulsed NaCl additions can increase the mortality of aquatic biota like detritivores, but the effects of chronic low-level additions are less understood. Small ionic increases may alleviate sodium limitation or osmoregulatory stress, thereby increasing microbial respiration and macroinvertebrate consumption, growth, and assimilation efficiency. We tested these predictions in freshwater microcosms containing either just sweetgum leaves with associated microbes or leaves, microbes, and an isopod (Lirceus sp.). Microcosms had one of three NaCl treatments: low (3mgL^-1Na; ambient), medium (14mgL^-1Na), or high (140mgL^-1Na). After 6 weeks, microbial respiration averaged 15% lower in medium and 29% lower in high than low treatments. Lirceus ate 71% more leaves in high than medium treatments, and assimilation efficiency was similar among treatments, averaging 75%. However, Lirceus growth was consistent between medium and high treatments. These results suggest Lirceus respiration increased from osmoregulatory stress in high NaCl treatments. Reduced growth from chronic low-level NaCl additions could lower detritivore fecundity and inhibit emergence, thereby altering stream community structure and function and reducing decomposition.

Meredith Tyree (Primary Presenter/Author), Institute of Arctic and Alpine Research, University of Colorado Boulder, meredithtyree@gmail.com;


Natalie Clay (Co-Presenter/Co-Author), Louisiana Tech University, nclay@latech.edu;


Sally Entrekin (Co-Presenter/Co-Author), Virginia Tech, sallye@vt.edu;

5/18/2015  |   14:30 - 14:45   |  102B

QUANTIFICATION OF MICROCYSTIN AMONG VARIOUS FISH SPECIES ACROSS MICHIGAN: A STUDY FOCUSED ON SAFE FISH CONSUMPTION The frequency and intensity of cyanobacterial blooms are increasing, resulting in an increase in cyanotoxins such as microcystin (Huisman et al., 2005). Microcystin is harmful if ingested and increasing levels of the toxin are a cause for concern from a human health perspective (Ibelings and Chorus, 2007). Microcystin exposure through water consumption is closely monitored in areas of concern; however, consumption of microcystin through fish is not generally regulated. A total of 141 fish of varying species were collected by the Department of Environmental Quality from four different lake basins in Michigan. Fish muscle tissue was tested for microcystin using Enzyme Linked Immunosorbent Assay. A subset of samples were additionally run using liquid chromatography mass spectrometry. Microcystin concentrations ranged from less than 2625 pg/g to 21814.82 pg/g dry weight, varying both between species and across locations. Detectable levels of microcystin were found at all locations. Channel catfish (Ictalurus punctatus), northern pike (Esox Lucius), and common carp (Cyprinus carpio) were found to have the highest concentrations of microcystin. These results highlight the need for regular monitoring of fish across Michigan.

Heather Snyder (Primary Presenter/Author), Grand Valley State University , snyderhe@mail.gvsu.edu;


Megan Woller-Skar (Co-Presenter/Co-Author), Grand Valley State University, wollerm@gvsu.edu;


Gregory Boyer (Co-Presenter/Co-Author), State University of New York College of Environmental Science and Forestry, glboyer@esf.edu;

5/18/2015  |   14:45 - 15:00   |  102B

DO FRESHWATER MUSSELS AFFECT MERCURY CONTAMINATION OF AQUATIC FOOD WEBS? Freshwater mussels are an important part of many freshwater ecosystems throughout North America. Mussels drive many significant ecosystem processes in lakes and rivers that link the water column and sediments, such as the conversion of mercury (Hg) found in sediments into highly toxic methylmercury (MeHg) that is released into the water column and subsequently aquatic food webs. Because of mussels’ important role in driving ecosystem function, we hypothesized that they regulate the production and/or release of MeHg. We tested this hypothesis with a field survey and a mesocosm study. We sampled fish and habitat parameters at sites with and without mussels and measured Hg contamination. We found no difference in Hg contamination of fish between mussel positive and negative sites. The follow-up mesocosm study used eight replicates of none, low (4), medium (10), and high (16) mussel density treatments. We collected emergent insects and snails for Hg analysis as well as abiotic parameters. Analysis of the samples is currently ongoing.

Brent Tweedy (Primary Presenter/Author), University of Oklahoma, brent.tweedy@ou.edu;


Caryn C. Vaughn (Co-Presenter/Co-Author), University of Oklahoma, cvaughn@ou.edu;