Toxic Effects of the Herbicide Roundup® Regular on Pacific Northwestern Amphibians

It has been implied that the application of pesticides is involved in the world-wide decline of biodiversity, but little is known about the influence of these chemicals on key predators of temporary wetlands. The direct impacts were examined of a frequently applied glyphosate-based herbicide on larval Aeshna cyanea (Müller, 1764; Odonata, Insecta) and adult male Lissotriton vulgaris (Linnaeus, 1758; Caudata, Amphibia), 2 top predators of Central European ephemeral ponds. The effects of herbicide exposure were measured on survival, behavior, body mass change, and predatory activity in an outdoor mesocosm experiment lasting for 17 d. No significant effects of exposure were observed in either predator species. The results suggest that the herbicide has no immediate effect on the predators studied at environmentally relevant concentrations and that these predators can also fulfill their top-down regulatory role in contaminated ecosystems.

Section: Resultscontrasting

confidence: 96%

No observable effect of a glyphosate‐based herbicide on two top predators of temporal water bodies

Ujszegi

Gál

Mikó

et al. 2014

“…Some glyphosate‐based herbicides are classed as slightly toxic to practically nontoxic (e.g., Roundup Biactive) . Conversely, other glyphosate‐based herbicides (e.g., Roundup Original) have been found to be moderately toxic (1 mg/L < LC50 < 10 mg/L) or even highly toxic (0.1 mg/L < LC50 < 1 mg/L) to tadpoles . Categories are those defined by the USEPA.…”

Section: Resultsmentioning

confidence: 99%

Questions concerning the potential impact of glyphosate‐based herbicides on amphibians

Wagner

Reichenbecher

Teichmann

et al. 2013

142

107

Use of glyphosate-based herbicides is increasing worldwide. The authors review the available data related to potential impacts of these herbicides on amphibians and conduct a qualitative meta-analysis. Because little is known about environmental concentrations of glyphosate in amphibian habitats and virtually nothing is known about environmental concentrations of the substances added to the herbicide formulations that mainly contribute to adverse effects, glyphosate levels can only be seen as approximations for contamination with glyphosate-based herbicides. The impact on amphibians depends on the herbicide formulation, with different sensitivity of taxa and life stages. Effects on development of larvae apparently are the most sensitive endpoints to study. As with other contaminants, costressors mainly increase adverse effects. If and how glyphosate-based herbicides and other pesticides contribute to amphibian decline is not answerable yet due to missing data on how natural populations are affected. Amphibian risk assessment can only be conducted casespecifically, with consideration of the particular herbicide formulation. The authors recommend better monitoring of both amphibian populations and contamination of habitats with glyphosate-based herbicides, not just glyphosate, and suggest including amphibians in standardized test batteries to study at least dermal administration.

“…This creates uncertainty for land managers who desire to implement its use for habitat restoration in wetlands. In several herbicide studies, the surfactant in the terrestrial formulation is more toxic than the active ingredient [25][26][27]. Although these data are compelling evidence to support concerns associated with the use of more toxic tank mixes in terrestrial habitats where amphibians occur, they are more difficult to interpret in relation to aquatic herbicide tank mixes used in wetland restoration.…”

Section: Discussionmentioning

confidence: 99%

Effects of the herbicide imazapyr on juvenile Oregon spotted frogs

Yahnke¹,

Grue²,

Hayes³

et al. 2012

Abstract-Conflict between native amphibians and aquatic weed management in the Pacific Northwest is rarely recognized because most native stillwater-breeding amphibian species move upland during summer, when herbicide application to control weeds in aquatic habitats typically occurs. However, aquatic weed management may pose a risk for aquatic species present in wetlands through the summer, such as the Oregon spotted frog (OSF, Rana pretiosa), a state endangered species in Washington. Acute toxicity of herbicides used to control aquatic weeds tends to be low, but the direct effects of herbicide tank mixes on OSFs have remained unexamined. We exposed juvenile OSFs to tank mixes of the herbicide imazapyr, a surfactant, and a marker dye in a 96-h static-renewal test. The tank mix was chosen because of its low toxicity to fish and its effectiveness in aquatic weed control. Concentrations were those associated with low-volume (3.5 L/ha) and high-volume (7.0 L/ha) applications of imazapyr and a clean-water control. Following exposure, frogs were reared for two months in clean water to identify potential latent effects on growth. Endpoints evaluated included feeding behavior, growth, and body and liver condition indices. We recorded no mortalities and found no significant differences for any end point between the herbicide-exposed and clean-water control frogs. The results suggest that imazapyr use in wetland restoration poses a low risk of direct toxic effects on juvenile OSFs. Environ. Toxicol. Chem. 2013;32:228-235. # 2012 SETAC