(ARMI) changing a filter in an air sampler that is used to measure agricultural chemicals that drift into Yosemite NP, California. Photo by: J. Fellers.
Declines in amphibian populations have occurred not only on areas clearly impacted by human activities such as urbanization, but also on protected lands intended to buffer amphibians and other wildlife from anthropogenic disturbances. Some stressors are not stopped by preserve boundaries and can affect wildlife populations 10's or 100's of kilometers from their source or point of use. For example, pesticides, fertilizers, or supplements given to livestock can be transported from the terrestrial setting where they are applied, to aquatic environments via precipitation, run-off, erosion, wind, and misuse. Conversely, some contaminants such as mercury or selenium occur naturally, but can be concentrated, or disturbed and released into the environment by human activities. Amphibian populations can be exposed to multiple stressors simultaneously, producing novel conditions with unknown outcomes.
ARMI scientists conduct research to identify stressors and evaluate their impacts on amphibian individuals and populations.
ARMI Products on Stressors
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Indicators of the Statuses of Amphibian Populations and Their Potential for Exposure to Atrazine in Four Midwestern U.S. Conservation Areas
Authors: Sadinski W, Roth M, Hayes T, Jones P, Gallant A | Date: 2014-09-12 | Outlet: PLoS ONE 9(9): e107018. doi:10.1371/journal.pone.0107018 | Format: .PDF
Extensive corn production in the midwestern United States has physically eliminated or fragmented vast areas of historical amphibian habitat. Midwestern corn farmers also apply large quantities of fertilizers and herbicides, which can cause direct and indirect effects on amphibians. Limited field research regarding the statuses of midwestern amphibian populations near areas of corn production has left resource managers, conservation planners, and other stakeholders needing more information to improve conservation strategies and management plans. We repeatedly sampled amphibians in wetlands in four conservation areas along a gradient of proximity to corn production in Illinois, Iowa, Minnesota, and Wisconsin from 2002 to 2005 and estimated site occupancy. We measured frequencies of gross physical deformities in recent metamorphs and triazine concentrations in the water at breeding sites. We also measured trematode infection rates in kidneys of recently metamorphosed Lithobates pipiens collected from nine wetlands in 2003 and 2004. We detected all possible amphibian species in each study area. The amount of nearby row crops was limited in importance as a covariate for estimating site occupancy. We observed deformities in <5% of metamorphs sampled and proportions were not associated with triazine concentrations. Trematode infections were high in metamorphs from all sites we sampled, but not associated with site triazine concentrations, except perhaps for a subset of sites sampled in both years. We detected triazines more often and in higher concentrations in breeding wetlands closer to corn production. Triazine concentrations increased in floodplain wetlands as water levels rose after rainfall and were similar among lotic and lentic sites. Overall, our results suggest amphibian populations were not faring differently among these four conservation areas, regardless of their proximity to corn production, and that the ecological dynamics of atrazine exposure were complex.
Detecting Emergence, Growth, and Senescence of Wetland Vegetation with Polarimetric Synthetic Aperture Radar (SAR) Data.
Authors: Gallant AL, Kaya SG, White L, Brisco B, Roth MF, Sadinski W, Rover J | Date: 2014-03-24 | Outlet: Water. 2014; 6(3):694-722 | Format: .PDF
Wetlands provide ecosystem goods and services vitally important to humans. Land managers and policymakers working to conserve wetlands require regularly updated information on the statuses of wetlands across the landscape. However, wetlands are challenging to map remotely with high accuracy and consistency. We investigated the use of multitemporal polarimetric synthetic aperture radar (SAR) data acquired with Canada’s Radarsat-2 system to track within-season changes in wetland vegetation and surface water. We speculated, a priori, how temporal and morphological traits of different types of wetland vegetation should respond over a growing season with respect to four energy-scattering mechanisms. We used ground-based monitoring data and other ancillary information to assess the limits and consistency of the SAR data for tracking seasonal changes in wetlands. We found the traits of different types of vertical emergent wetland vegetation were detected well with the SAR data and corresponded with our anticipated backscatter responses. We also found using data from Landsat’s optical/infrared sensors in conjunction with SAR data helped remove confusion of wetland features with upland grasslands. These results suggest SAR data can provide useful monitoring information on the statuses of wetlands over time.
Pesticide concentrations in frog tissue and wetland habitats in a landscape dominated by
Authors: Smalling KL, Reeves R, Muths E, Vandever M, Battaglin WA, Hladik ML, Pierce CL | Date: 2014 | Outlet: Science of the Total Environment | Format: .PDF
Among the multiple stressors potentially affecting the presence of amphibians across agricultural landscapes, habitat loss and exposure to pesticides are likely primary factors contributing to amphibian decline. Conservation efforts have attempted to restore wetlands lost through landscape modifications with the aim of reducing contaminant loads in surface waters and providing quality habitat to wildlife. However, the benefits of this increased wetland area, perhaps especially for amphibians, may be negated if habitat quality is insufficient to support persistent populations. We examined the presence of pesticides and nutrients in water and sediment as indicators of habitat quality and assessed the accumulation of pesticides in tissue of two native amphibian species Pseudacris maculata (chorus frogs) and Lithobates pipiens (leopard frogs) at six wetlands (3 restored and 3 reference) in Iowa, USA. Restored wetlands are positioned on the landscape to receive subsurface tile drainage water while reference wetlands receive water from overland run-off and shallow groundwater sources. Concentrations of the pesticides frequently detected in water and sediment samples were not different between wetland types. The herbicide atrazine was detected in 100% of the water samples and in some instances at concentrations high enough to potentially cause reproductive effects in leopard frogs. Nutrient concentrations were higher in the restored wetlands but lower than concentrations thought to cause lethality in frogs. Seventeen pesticides were detected in tissue samples with concentrations ranging from 0.08
to 1,500 µg/kg wet weight. No significant differences in pesticide concentrations were observed between species, although concentrations tended to be higher in leopard frogs compared to chorus frogs, possibly because of differences in life histories. Our results provide information on habitat quality in restored wetlands that will assist state and federal agencies, landowners, and resource managers in identifying and implementing conservation and management actions for these and similar wetlands in agriculturally dominated landscapes.