Subchronic sensitivity of one-, four-, and seven-day-old fathead minnow (Pimephales promelas) larvae to five toxicants

Abstract

The fathead minnow (Pimephales promelas) larval survival and growth test was used to evaluate the relative sensitivity of 1-, 4-, and 7-d-old larvae to five contaminants, KCl, NaCl, 1-octanol, carbaryl, and benzaldehyde. The no observable effect concentration (NOEC) for survival of the two inorganic compounds, KCl and NaCl, was not affected by age of the larvae. The subchronic valve (SCV) for NaCl was always determined by survival. Hypothesis testing of biomass always gave the same NOEC for the three age groups for each of the two inorganic compounds, and a minimum significant difference (MSD) was always calculable. The effect of 1-octanol on growth was more sensitive than the effect on survival in eight of the nine toxicity tests. Within a set of 1-, 4-, and 7-d-old larvae tests the SCV varied only twofold; however, between sets of tests the variation was fourfold. The SCV of carbaryl was determined by the effect on growth in five of six tests. Except for one test the SCV varied only twofold. The 1-d larvae were more sensitive to benzaldehyde than 1- and 7-d larvae in two sets of tests. The SCV was determined on the basis of survival for 1-d-old larvae and on themore » basis of growth for 4- and 7-d-old larvae.« less