Effect of release® herbicide on mortality, avoidance response, and growth of amphibian larvae in two forest wetlands

Abstract

Effects of Release herbicide (triclopyr butoxyethyl ester, [TBEE]) on mortality, avoidance response, and growth of larval amphibians (Rana clamitans, Rana pipiens) were investigated using in situ enclosures deployed in two forest wetlands in northern Ontario, Canada. Release was applied at nominal concentrations ranging from 0.26 to 7.68 mg TBEE acid equivalents (AE)/L. No significant deleterious effects of this herbicide on larval growth were detected. However, concentration-dependent mortality and abnormal avoidance response were observed. Most mortality occurred within 96 h following treatment. Median lethal concentration (LC50) values for each species and experimental site ranged from 2.79 to 3.29 mg AE/L, while median effective concentration (EC50) values (abnormal avoidance response) ranged from 1.67 to 3.84 mg AE/L. The LC10 and EC10 endpoints approximated aqueous concentrations (0.59 mg AE/L) expected under direct aerial overspray scenarios, indicating a potential risk of impacts for a small proportion of native amphibian larvae. However, given the low frequency and limited use of this herbicide formulation in Canadian forestry, these risks are considered negligible. Changes in usage patterns would require concurrent chemical and biological monitoring of operational spray programs to accurately quantify the probability and magnitude of real-world exposures and to relate these exposure levels to concentration-response relationships including those described in this study.

Effects of chemical management for invasive plants on the performance ofLithobates pipienstadpoles

“…The aqueous half-life of triclopyr is estimated at 0.5 to 7.5 d [47]. Concentrations of triclopyr in aquatic environments have been recorded at 0.25 to 7.86 mg/L, with a maximum expected environmental concentration of 2.7 mg/L [46][47][48][49][50][51]. Experiments examining median lethal concentration values on fish suggest that lethal concentrations may be >200 mg/L [45,52].…”

Toxic, cytotoxic, and genotoxic effects of a glyphosate formulation (Roundup®SL–Cosmoflux®411F) in the direct‐developing frogEleutherodactylus johnstonei

“…Studies conducted in natural habitat enclosures have generated contradictory results. VisionV R formulation conferred negligible adverse effects on sensitive larval life stages of native amphibian species in northern Ontario, Canada Wojtaszek et al, 2004]. However, RoundupV R formulation resulted in a 70% decline in species richness of tadpoles in an experimental reservoir in Pennsylvania, USA [Relyea, 2005b], with increased effects under conditions of competitive stress [Relyea, 2004[Relyea, , 2009Jones et al, 2011].…”

Multiple stressor effects of herbicide, pH, and food on wetland zooplankton and a larval amphibian

“…This study was conducted to examine the effects of Release® in combination with two important environmental variables, pH and food availability, on wetland zooplankton and amphibians. It is part of a multiple-tiered research program for investigating the effects of herbicides used in forestry management (Thompson, 2004;Edginton et al, 2003;Chen et al, 2004;Edginton et al, 2004;Thompson et al, 2004;Wojtaszek et al, 2004;Wojtaszek et al, 2005). Zooplankton and amphibians are ubiquitous in freshwater environments and known to be particularly sensitive indicators of stress (Schindler, 1987;Murphy et al, 2000).…”

“…They also increase yields of spruce/fir stands and pine plantations, and are used to clear utility right-of-ways and eliminate invasive species. In surface waters, TBEE has a half-life of 3-8 days (Kreutzweiser et al, 1995;Wojtaszek et al, 2005) and is rapidly absorbed by biota, sediments and allochthonous materials (Solomon et al, 1988;Barron et al, 1990;Kreutzweiser et al, 1995;.…”

“…In these tests, exposure concentrations were held relatively constant. However, in natural surface waters the more toxic ester form of triclopyr dissipates rapidly with time to 50% dissipation ranging from < 1 day up to 8 days depending on numerous factors influencing the primary dissipation mechanisms of photolysis, hydrolysis and microbial degradation (Solomon et al, 1988;Kreutzweiser et al, 1995;Wojtaszek et al, 2005).…”