John Wiley & Sons, Ltd.

Soil organic matter content effects on dermal pesticide bioconcentration in American toads (Bufo americanus)

Pesticides have been implicated as a major factor in global amphibian declines and may pose great risk to terrestrial phase amphibians moving to and from breeding ponds on agricultural landscapes. Dermal uptake from soil is known to occur in amphibians, but predicting pesticide availability and bioconcentration across soil types is not well understood. This study was designed to compare uptake of five current‐use pesticides (imidacloprid, atrazine, triadimefon, fipronil, pendimethalin) in American toads (Bufo americanus) from exposure on soils with significant organic matter (OM) content differences (14.1% = high OM and 3.1% = low OM). We placed toads on high or low OM soil after applying individual current use pesticides on the soil surface for an 8‐hour exposure duration. Whole body tissue homogenates and soils were extracted and analyzed using LC‐MS to determine pesticide tissue and soil concentration, as well as bioconcentration factor in toads. Tissue concentrations were greater on the low OM soil than the high OM soil across all pesticides (average ± SE; 1.23ppm ± 0.35 and 0.78ppm ± 0.23, respectively), and bioconcentration was significantly higher for toads on the low OM soil (ANCOVA p = 0.002). Soil organic matter is known to play a significant role in mobility of pesticides and bioavailability to living organisms. Agricultural soils typically have relatively lower organic matter content and serve as a functional habitat for amphibians. The potential for pesticide accumulation in amphibians moving throughout agricultural landscapes may be greater and should be considered in conservation and policy efforts. This article is protected by copyright. All rights reserved

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