Physical impacts of diluted bitumen (dilbit) and the application of surface washing agents (SWAs) in freshwater have not been characterized for aquatic invertebrates. These compounds are known to reduce surface tension in feather and fur microstructures of birds and mammals, and are thus likely to affect the buoyancy of surface‐dwelling aquatic insects. We evaluated impacts of fresh dilbit and a SWA on water striders (Metrobates sp.), which are surface‐dwelling organisms that rely on fine‐hair microstructures to remain buoyant. We report nominal sheen thickness values that cause 50% immobility in 48 h as determined from exposure studies in outdoor tanks. A comparison of our data with those from historic oil spill volumes in Canada and the United States in the past 12 yr indicates that our reported nominal sheen thicknesses could have been reached or exceeded in 99% of historic spills when scaled to a small reference lake. The addition of Corexit EC9580A, a SWA approved for marine use in Canada, led to 100% immobility in striders within minutes, both in combination with oil and alone. Our study reveals an acute sensitivity to Corexit EC9580A and dilbit by surface‐dwelling insects and may be driven by disruption of mechanisms of buoyancy. We highlight a need to evaluate physical impacts, typically excluded from standard toxicity testing, within the context of spill impact mitigation assessments. Environ Toxicol Chem 2021;40:1298–1307. © 2020 SETAC

中文翻译：

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低能淡水环境中的地表栖息水生昆虫受到溢油和用于溢油响应的表面清洗剂 Corexit EC9580A 的高度影响

稀释沥青 (dilbit) 的物理影响和淡水中表面清洁剂 (SWA) 的应用尚未对水生无脊椎动物进行表征。已知这些化合物可以降低鸟类和哺乳动物的羽毛和毛皮微结构的表面张力，因此可能会影响表面栖息的水生昆虫的浮力。我们评估了新鲜稀释剂和 SWA 对水黾的影响（Metrobatessp.)，它们是依靠细毛微结构保持浮力的表面栖息生物。我们报告了根据室外水箱中的暴露研究确定的在 48 小时内导致 50% 不动的标称光泽厚度值。将我们的数据与过去 12 年加拿大和美国的历史漏油量数据进行比较表明，当缩放到一个小型参考湖时，99% 的历史漏油可能已经达到或超过了我们报告的标称光泽厚度。添加 Corexit EC9580A（一种获准在加拿大用于海上使用的 SWA）后，无论是与油相结合还是单独使用，都可以在几分钟内使 striders 100% 不动。我们的研究揭示了对 Corexit EC9580A 和地表昆虫稀释剂的急性敏感性，这可能是由于浮力机制的破坏所致。环境毒物化学2021；40:1298–1307。© 2020 SETAC