Responses of fish exposed to a C9--11 linear alcohol ethoxylate nonionic surfactant in stream mesocosms

Abstract

Bluegill sunfish (Lepomis macrochirus) and fathead minnow (Pimephales promelas) responses to a nonionic linear alcohol ethoxylate (LAE) surfactant were examined in 10-day laboratory and 30-day outdoor stream mesocosm experiments. Larval fathead minnow survival was determined in a 10-day laboratory study with nominal concentrations of 0, 1.0, 3.0, 7.0, 13.0 and 25.0 mg LAE l−1. Bluegill sunfish survival and growth and fathead minnow survival, reproduction and behaviour were evaluated in replicated stream mesocosms with mean measured concentrations of 0, 0.73, 2.04, 4.35, 5.7 and 11.24 mg LAE l−1. The 10-day laboratory No Observed Effect Concentration (NOEC) for larval fathead minnow survival was 1.0 mg l−1. The 30-day stream NOEC for bluegill sunfish survival and growth was 5.7 mg l−1. In the stream mesocosms, NOECs for adult fathead minnow survival, reproduction and behaviour were 2.04 mg l−1, 0.73 mg l−1 and 0.73 mg l−1, respectively. Surviving fathead minnows that had ceased reproduction following exposure to LAE in the streams re-established normal reproduction during a post- treatment observation period in the laboratory. Laboratory studies in conjunction with the stream mesocosm study yielded complementary results which provided a detailed assessment of threshold responses of fish to LAE