Effects of temperature and salinity on Menidia beryllina embryos exposed to terbufos

Abstract

Embryos of the inland silverside Menidia beryllina were exposed to the organophosphorus pesticide terbufos at 9 combinations of temperature (20, 25 and 30C) and salinity (5, 12.5 and 20%.). Nominal exposure concentrations were 12.5, 25, 50 and 100 pg terbufos 1-' with an acetone and seawater control for each temperature/salinity combination. Test durations were temperature dependent and ranged from 5 to 14 d. Endpoints were embryo survival, hatching and percentage of larvae with normal vertebrae. Embryo survival was significantly ( a = 0.05) lower in tests conducted at 20C for all salinities. Salinity affected survival only at combinations of 20%0 and 100 ~g terbufos I-' Both temperature and salinity affected the percentage hatch, wlth the lowest hatching occurring in tests at 20 "C and in tests conducted at 20 L. The percentage of larvae with normal vertebrae was significantly (a = 0.05) reduced from controls at terbufos concentrations of 25 (7 to 32 %), 50 (44 to 62 %) and 100 pg 1-' (58 to 73 %) for the 3 temperatures tested, whereas salinity showed no significant effect. Anomalies in the development of vertebrae occurred across all temperature and salinity combinations, and were observed at concentrations as low as 12.5 pg terbufos 1-'