NIETO, V.*; MCCLARY, JR., M.; Fairleigh Dickinson University; Fairleigh Dickinson University: Toxicity test of Roundup on the fiddler crab Uca pugnax (Smith) and the ribbed mussel Geukensia demissa (Dillwyn)

The aquatic herbicide Rodeo is used to kill weeds and marsh grasses such as the invasive common reed Phragmites australis and the cord grass Spartina alterniflora. Since there are many different species of animals living in areas where it is applied, Roundup, a Rodeo analog that is readily obtainable, was tested to determine its effects on the ribbed mussel, Geukensia demissa, and the fiddler crab, Uca pugnax. The mean number of mussels that survived in 0.3125, 0.625, 1.25, 2.5, 5, and 10% Roundup after 3-5 days was 0. The mean number of crabs that survived in 5 and 10% Roundup after 3-5 days was significantly different from the control. In another experiment that tested crab feeding, 10^-1 M glucose induced the highest number of feeding motions. To determine if Roundup had an effect on the number of crab feeding motions at this glucose concentration, triplicate finger bowls were filled with seawater, 10^-1 M glucose, and 10^-1 M glucose with 5% Roundup. The decrease in feeding in the 5% Roundup mixture was not significantly different from 10^-1 M glucose and the control. The experiments showed that mussels were more sensitive to Roundup than crabs. Roundup should only be used at the lowest doses possible (<0.3125%), especially if mussels inhabit or can inhabit areas where Roundup is applied.