Browsing by Author "Olker, Jennifer"

Now showing 1 - 4 of 4
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    Effects of atrazine and climate change on amphibian larval development and growth
    (2014-04) Olker, Jennifer
    The distribution and population persistence of many North American amphibians depends on environmental factors at multiple spatial scales. Anthropogenic and naturally occurring stressors, including contaminants, predators, and pond-drying, have been shown to affect amphibian growth, development, and health. The herbicide atrazine (2-chloro-4-ethylamino-6-isoproyl-amino-s-triazine) is a widely used pesticide in the U.S., and in some amphibians has been shown to reduce size and health at metamorphosis and alter gonadal function, presumably through endocrine disruption. Environmental changes predicted by climate models could exacerbate these impacts, as well as directly affect amphibian development and population persistence through accelerated pond-drying and habitat loss or modification. Objectives of this project were to: 1) Quantify developmental responses to the combined effects of atrazine exposure and accelerated pond-drying rates; and 2) Quantify potential effects of these and other environmental stressors on amphibian occurrence and health. Growth, development, and physiological state (skeletal/eye malformations and gonadal development) were assessed in northern leopard frog (Rana pipiens) and wood frog (Rana sylvatica) in experimental exposures and field surveys in the U.S. Prairie Pothole Region across a range of environmentally relevant atrazine concentrations (0.1, 20, and 200 μg/L) and in combination with climate change and other environmental factors suspected to affect amphibian larval development. Atrazine exposure during larval development decreased survival and had sub-lethal impacts on growth and development, which could negatively impact populations by reducing annual recruitment and survival of juveniles. Presence, abundance, and severity of testicular oocytes (TOs) did not appear to be related to atrazine exposure in experimental or field specimens; however, TO prevalence differed greatly between species (>40% in R. pipiens and <5% in R. sylvatica). These results suggest that TOs are not likely due solely to endocrine disruption by atrazine and more research is needed to understand reproductive or population-level impacts of TOs. Amphibian metrics (presence, breeding, skeletal malformations, and TOs) responded differently to environmental variables from wetland, local, and landscape scales, and amphibian breeding (presence or success) was identified as a better indicator of environmental condition than species presence, calling, or TOs.
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    Minnesota lake water quality on-line database and visualization tools for exploratory trend analyses
    (University of Minnesota Duluth, 2009-08-31) Axler, Richard P; Will, Norman; Ruzycki, Elaine; Henneck, Jerald; Olker, Jennifer; Swintek, Joe
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    Minnesota’s Lake Superior Coastal Program: Evaluating Vital, Small Forested Wetlands
    (University of Minnesota Duluth, 2015) Olker, Jennifer; Hueffmeier, Ryan; Johnson, Lucinda B
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    St. Louis River Watershed Streams & Lakes: Water Quality/Biological Monitoring
    (University of Minnesota Duluth, 2011-06-29) Axler, Richard P; Breneman, Dan; Brady, Valerie; Johnson, Lucinda B; Ruzycki, Elaine; Henneck, Jerald; Olker, Jennifer; Host, George E; Brown, Terry; Bartsch, Will
    This provisional report is an addendum to the Surface Water Assessment Final Report entitled Surface Water Assessment St. Louis River Watershed: Streams and Lakes: Water quality/biological monitoring submitted to the MPCA electronically on June 29, 2011. That final report summarizes the water quality, habitat, macroinvertebrate, and fish data previously submitted to MPCA as the major part of this SWA project. This provisional report represents a detailed summary of the statistical analyses that the Natural Resources Research Institute (NRRI) at the University of Minnesota-Duluth is conducting using the data collected from this project together with previous and ongoing landscape stressor analyses conducted by NRRI via other funding sources over the past several years.