Meeting Abstract
2,4-dichlorophenoxyacetic acid (2,4-D) is contained in many systemic herbicides used worldwide for selective weed control of invasive plants in agriculture and aquatic ecosystems. The US Environmental Protection Agency (EPA) permits aquatic 2,4-D amine applications up to 2ppm for whole-lake treatments with a follow-up treatment 21 d after initial application. For multiple native WI fish species, we exposed early life stages (embryos and/or larvae) and juvenile fish to environmentally relevant concentrations of 2,4-D (0-2ppm) as the active ingredient alone and as the commercial formulations that are applied in the field. Survival was depressed by 2,4-D exposure for at least one early life stage in 78% of species tested (n=9); there were no impacts on juvenile fish survival in 5 species tested. In functional studies, 2,4-D interacted with neurobehavioral and endocrinological physiological systems. For example, in larval zebrafish, exposure to a 2,4-D commercial formulation reduced neural activity within the optic tectum and decreased prey capture ability, and this essential survival behavior was also depressed in larval yellow perch (Perca flavescens). In one type of endocrine study with juvenile fathead minnows (Pimephales promelas) raised in 0.05 ppm 2,4-D, whole-body cortisol rise following a stress challenge (momentary removal from water) was reduced >50%. These multiple lines of evidence underscore previously unappreciated risks associated with current 2,4-D application practices. Although designed to act against plant biochemical/physiological systems as a cell growth deregulator, 2,4-D joins other major herbicides such as atrazine and glyphosate as having surprising, significant non-target effects on function and survival of aquatic vertebrates. Work supported by the WI Dept. Natural Resources.
