The Quantification of Tissue Residues of Glyphosate and Aminomethyl Pohsphonic Acid (AMPA) in Clams and Oysters Associated with the Application of Rodeo to Control Smoth Cordgrass (Spartina Alterniflora)

To determine whether an increase in application rates of Rodeo (aerial 18.8 ai/har; ground 8% v/v) on Spartina alterniflora beds in Willapa, WA would reult in tissue concentrations of glyphosate in shellfish that exceed the established tolerance of 3 ppm wet weight edible tissue, oyster (Crassostrea gigas) and clams (Tapes philippinarum) were exposed to glyphosate via a layer of spiked sediment (6 ppm glyphosate)and two simulated tidal inundations of spiked seawater once per week for 4 weeks. In the first tidal inundation oysters and clams were exposed to 2 ppm glyphosate in seawater diluted to 0.10 ppm; in the second, 0.10 ppm. Clean seawater was provided during simulated tidal inundations the remaining 6 days per week. Tissue and sediment samples were collected the day before and 24 h after each exposure to contaminated seawater. Concentrations of glphosate and AMPA did not exceed 0.4 ppm in the tissue samples.