Evaluation of Juvenile Freshwater Mussel Sensitivity to Multiple Forms of Florpyrauxifen-Benzyl
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Evaluation of Juvenile Freshwater Mussel Sensitivity to Multiple Forms of Florpyrauxifen-Benzyl Sean B. Buczek1 · Jennifer M. Archambault1 · W. Gregory Cope1 · Mark A. Heilman2 Received: 9 April 2020 / Accepted: 13 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract ProcellaCOR® (active ingredient [ai], florpyrauxifen-benzyl) is an aquatic herbicide registered for use in 2018 for managing invasive and nuisance macrophyte species. Registration studies evaluating its acute toxicity revealed a favorable environmental profile; however, prior to this study, no information existed on the toxicity of florpyrauxifen-benzyl to native freshwater mussels (Family Unionidae), one of the most sensitive and imperiled faunal groups globally. We followed standard acute (96 h) toxicity test guidelines and exposed juvenile Fatmucket (Lampsilis siliquoidea) and Eastern Lampmussel (Lampsilis radiata) to the following formulations or compounds: ProcellaCOR SC and EC formulations, technical grade active ingredient (TGAI, florpyrauxifen-benzyl), and an analytical-grade sample of the weaker florpyrauxifen acid (FA). In all tests, the estimated median lethal concentrations to produce 50% mortality (LC50) were greater than the highest concentration tested of each formulation or compound. The no observable adverse effect concentrations (NOAEC, based on analytical recoveries measured at the highest concentration tested where no toxicity was observed) were TGAI = 26 µg/L, FA = 100,000 µg/L, rocellaCOR® EC = 585 µg ai/L and the NOAEC values for the registered commercial ProcellaCOR® SC = 193 µg ai/L P formulation products (ProcellaCOR® SC and ProcellaCOR® EC) were orders of magnitude greater (3.9× and 11.7×, respectively) than the maximum application rate (50 µg/L). Our results show that the herbicide formulations and compounds tested were not acutely toxic to juveniles of these two species of freshwater mussels, indicating minimal risk of short-term exposure from florpyrauxifen-benzyl applications in the environment for aquatic weed control. However, potential chronic or sublethal effects remain uncharacterized and warrant additional investigation. Keywords Unionid · Toxicity · Herbicide · Florpyrauxifen-benzyl · ProcellaCOR® · Rinskor™ Nuisance and noxious aquatic vegetation is an increasing problem in natural resource conservation and management. Generally, aquatic plants are important components of aquatic ecosystems and provide many beneficial ecosystem services, including nutrient cycling, increased biodiversity, and improved water quality (Barko and James 1998; Srivastava et al. 2008; Thomaz and Cunha 2010). However, as a result of invasive species introductions and/or system nutrient imbalances, aquatic vegetation can also cause a host of negative ecosystem consequences (Chamier et al. 2012; Santos et al. 2011; Kuehne et al. 2016). Mitigating the impacts * Sean B. Buczek [email protected] 1
Department of Applied Ecology, North Carolina State University, Campus Box 7617, Raleigh, NC 2
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