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

Abstract

The effects of Vision (glyphosate, 356 mg acid equivalents (a.e.)/L) on mortality, avoidance response, and growth of larval amphibians (Rana clamitans and Rana pipiens) were investigated using in situ enclosures deployed in two forest wetlands of northern Ontario, Canada. In addition to untreated controls, Vision was applied to yield initial concentrations ranging from 0.29 to 14.3 mg a.e./L (0.94-46.1 mg/L of Vision). Resultant 96-h median lethal concentration (LC50) values ranged from 2.70 to 11.5 mg a.e./L (8.71-37.1 mg/L of Vision) depending on the species or site involved. Substantial mortality and incidences of abnormal avoidance response occurred only at concentrations exceeding the expected environmental concentrations (EEC) (1.43 mg a.e./L, or 4.61 mg/L of Vision) as calculated by Canadian regulatory authorities. The concentration dependence of larval growth rate and maximum size varied depending on site and species. Mean growth rates and maximum sizes exposed to 1.43 mg a.e./L (EEC) treatments were the same or greater than controls. Experimental site and biotic/abiotic factors therein, such as pH and suspended sediments, substantially affected the expression of Vision herbicide toxicity in the amphibian larvae tested. Overall, results suggest that the silvicultural use of Vision herbicide in accordance with the product label and standard Canadian environmental regulations should have negligible adverse effects on sensitive larval life stages of native amphibians.

Acute toxicity and sublethal effects of the mixture glyphosate (Roundup® Active) and Cosmo-Flux®411F to anuran embryos and tadpoles of four Colombian species

“…Toxicity of frog embryos and tadpoles was less in the microcosms than in laboratory tests. The reason for this may be attributed to the presence of sediments and organic matter which rapidly adsorb the glyphosate (Relyea, 2004;Tsui & Chu, 2004;Wojtaszek et al, 2004) and surfactants such as POEA (Wang et al, 2005). In addition, residues of glyphosate decline rapidly within 24h after application (Trumbo, 2005).…”

“…The life cycle and physiological characteristics of amphibians make them particularly susceptible to all environmental stressors (Cowman & Mazanti, 2000). Glyphosate formulations have been considered to induce genotoxic, morphological, biochemical, and physiological effects to anurans (Clements, Ralph, & Petras, 1997;Lajmanovich, Lorenzatti, Maitre, Enrique, & Peltzer, 2003;Cauble & Wagner, 2005;Bernal, Solomon, & Carrasquilla, 2009a;Mann, Hyne, Choung, & Wilson, 2009;Lenkowski, Sanchez-Bravo, & Mclaughlin, 2010;Williams & Semlitsch, 2010;Lajmanovich, Attademo, Peltzer, Junges, & Cabagna, 2011;Relyea, 2012), although low toxicity has been reported under realistic field conditions (Howe et al, 2004;Wojtaszek, Staznik, Chartrand, Stephenson, & Thompson, 2004;Bernal, Solomon, & Carrasquilla, 2009b). Other studies have concluded that the glyphosate and its formulated products represent moderate (Giesy, Dobson, & Solomon, 2000;Sparling, Linder, Bishop, & Krest, 2010) or negligible risk to aquatic organisms (World Health Organization International Program on Chemical Safety, 1994; Giesy et al, 2000;Solomon & Thompson, 2003).…”

Competitive stress can make the herbicide Roundup® more deadly to larval amphibians

“…Among the many abiotic stressors that could interact with glyphosate, only pH has been manipulated. In these studies, glyphosate with POEA became substantially more lethal to larval amphibians at higher pH [15,16,18]. Among the many biotic stressors, one study has manipulated the stress of predation risk and found that glyphosate with POEA became more lethal in the presence of chemical cues emitted by predators [6].…”

The Risks Associated with Glyphosate-Based Herbicide Use in Planted Forests

“…Coincident biomonitoring showed no significant toxic effects on two species of sensitive amphibian larvae caged within the multiple wetlands under study. Furthermore, in situ enclosure field studies in either ponds in northern Ontario or in small wetlands in New Brunswick Canada, showed no significant effects on amphibian survival, growth or development when directly exposed to formulated glyphosate-based herbicides even at the maximum permissible label rates [77,78,90,91]. These results were similar to a field study in Oregon USA, assessing the effects of clear-cutting and clear-cutting followed by glyphosate application where no herbicide effects were observed for six species of amphibians [92].…”

“…The high adsorption capacity of sediment for glyphosate has frequently resulted in higher peak concentrations in sediments compared with water (Table 3), that persisted for longer periods of time, even when the active ingredient was present in only small quantities in the water column (Table 3). It is likely that this process is a primary pathway for removal of glyphosate from the water column in forested freshwater environments [52,56,73,77,78].…”