Research Product

Toxicities of 2 industrial chemicals (4-nitrophenol and 2,4-dinitrophenol) and 2 organophosphate insecticides (terbufos and trichlorfon) to juvenile grass shrimp (Palaemonetes spp.) and sheepshead minnows (Cyprinodon variegatus) were determined by static, 96-h toxicity tests in a factorial design with 12 combinations of salinity and temperature (15, 20, 25, 30 ppt x 17, 22, 27°C). Concentrations of the toxicants, including bioconcentration, were determined as appropriate by gas or liquid chromatography and the use of 14C-labeled compounds. The 96-h LC50s for 4-nitrophenol ranged from 12 to 31 mg/L and for 2,4-dinitrophenol from 13 to 50 mg/L. Toxicity decreased as salinity increased for 2,4-dinitrophenol and sheepshead minnows, but toxicity to grass shrimp increased as salinity increased. Toxicity decreased with increased temperature for grass shrimp exposed to 2,4-dinitrophenol and sheepshead minnows exposed to 4-nitrophenol, and no change was observed for grass shrimp exposed to 4-nitrophenol. Bioconcentration increased as concentration increased. The 96-h LC50s for terbufos ranged from 3.4 to 6.6 µg/L and for trichlorfon, from 6.3 to 19,300 µg/L. Terbufos and trichlorfon toxicity to grass shrimp and sheepshead minnows increased with increased temperature. Bioconcentration factors for terbufos were greater in sheepshead minnows than grass shrimp, but were reversed for trichlorfon.