Biology Department, University of New Brunswick, Saint John, New Brunswick, Canada.
Environ Toxicol Chem. 2012 Oct;31(10):2375-83. doi: 10.1002/etc.1956. Epub 2012 Aug 16.
Herbicides are commonly used in agriculture and silviculture to reduce interspecific competition among plants and thereby enhance crop growth, quality, and volume. Internationally, glyphosate-based herbicides are the most widely used herbicides in both of these sectors. Laboratory and mesocosm studies have demonstrated that some formulations are toxic to amphibian larvae below concentrations that approximate predicted maximal or "worst-case" exposure scenarios. However, field studies have not found evidence of toxicity at these concentrations. The authors conducted a replicated field experiment involving 10 naturalized wetlands split in half with an impermeable plastic barrier to assess the direct toxicity of a glyphosate formulation commonly used in silviculture (VisionMAX™). The herbicide formulation was applied directly to the surface of one side of each wetland at one of two target aqueous exposure rates (high = 2,880, low = 550 µg acid equivalents [a.e.]/L), and the other side was left as an untreated control. The survival and growth of green frog larvae (Lithobates clamitans) were assessed for two years following herbicide treatment. The herbicide did not have a negative impact on survival or growth of L. clamitans larvae at either treatment level. In fact, mean larval abundance was typically greater in the treated sides than in control sides within the year of herbicide application. These results indicate that typical silviculture use of VisionMAX poses negligible risk to larval amphibians, likely because the combined effects of sorption and degradation in natural wetlands limit the exposure magnitude and duration.
除草剂通常被用于农业和林业中，以减少植物间的种间竞争，从而促进作物生长、提高作物质量和增加作物产量。在国际上，草甘膦类除草剂在这两个领域的应用最为广泛。实验室和中观生态系统研究表明，一些制剂对两栖动物幼虫具有毒性，其浓度低于接近预测最大或“最坏情况”暴露情景的浓度。然而，田间研究并未在这些浓度下发现毒性的证据。作者进行了一项重复的野外实验，涉及 10 个自然湿地，用不可渗透的塑料屏障将其对半分开，以评估一种常用于林业的草甘膦制剂（VisionMAXTM）的直接毒性。将除草剂制剂直接施用于每个湿地一侧的表面，施用量为两种目标水暴露率之一（高=2880，低=550µg 酸当量[a.e.]/L），另一侧则作为未处理的对照。在施药后两年内评估了绿蛙（Lithobates clamitans）幼虫的存活和生长情况。在两种处理水平下，除草剂均未对 L. clamitans 幼虫的存活或生长产生负面影响。事实上，在施药当年，处理侧的幼虫丰度通常高于对照侧。这些结果表明，林业中典型的 VisionMAX 使用对幼体两栖动物造成的风险很小，这可能是因为自然湿地中吸附和降解的综合作用限制了暴露的程度和持续时间。
