PESTICIDE USAGE ON THE SOUTHERN HIGH PLAINS AND ACUTE TOXICITY OF FOUR CHEMICALS TO THE FAIRY SHRIMP THAMNOCEPHALUS PLATYURUS (CRUSTACEA: ANOSTRACA)

摘要

Extensive pesticide use on crops grown on the Southern High Plains (SHP) represents a considerable anthropogenic stressor to ephemeral aquatic ecosystems. These short-lived aquatic ecosystems, known in the southwest as playas, are epicenters of biodiversity on the High Plains. Cotton is the major agricultural crop grown on the SHP, accounting for over half of all cotton produced in Texas. Currently there are 67 different chemicals used to control cotton pests, and when other crops such as grain sorghum are included the number approaches 100. Thamnocephalus platyurus is a fairy shrimp indigenous to the Southern High Plains that is also available commercially. In addition it is used as an invertebrate model for water quality and toxicity testing. Acute toxicity of four agricultural pesticides widely used on the SHP (Methyl Parathion 4E, Tempo® SC Ultra [active ingredient cyfluthrin], Roundup® [glyphosate], and Karmex® DF [diuron]) was determined using laboratory-derived T. platyurus. Twenty-four hour old nauplii experienced mortality (48 hour LC50) at concentrations ranging from 10.99 μg/L for Tempo® SC Ultra and 1.248 mg/L for Roundup®. These results suggest that the current pesticide application rates have the potential to endanger the native playa invertebrate T. platyurus.