Toxicity of the aquatic herbicide, reward®, to the northwestern salamander
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Diquat dibromide (DB) is the active ingredient in several herbicide products used around the world for industrial and recreational control of terrestrial and aquatic pest plants. This study aimed to assess the adverse effects of the commercial formulation of the aquatic herbicide, Reward®, on the Pacific Northwest amphibian species, the northwestern salamander (Ambystoma gracile). Larvae were exposed to the Reward® herbicide in a 96-h acute bioassay (0.37–151.7 mg/L DB) and a continuous 21-day exposure (0.37–94.7 mg/L DB). The 96-h LC50 was 71.5 mg/L and the 21-day LC50 was 1.56 mg/L. Collectively, the results of this study demonstrate that early life stage A. gracile larvae appear largely insensitive to acute Reward® exposures compared to early life stage fish. However, A. gracile larvae are considerably more sensitive during sub-chronic exposure (21 days) with lethal and sub-lethal effects on growth occurring in the 1–2 mg/L range, which more closely resembles the larval fish lethal sensitivity to this active ingredient. This is the first study examining the toxicity of the aquatic herbicide formulation Reward® on A. gracile under acute and sub-chronic exposure scenarios.
KeywordsToxicology Aquatic herbicide Ecology Diquat dibromide Northwestern salamander Amphibians
We are grateful to Dr. Chris Kennedy and Dr. David Huebert for their input on this manuscript.
This work was funded by the National Contaminants Advisory Committee under the Department of Fisheries and Oceans Canada.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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