An assessment of the ecological effects of a C9--11 linear alcohol ethoxylate surfactant in stream mesocosm experiments

The responses of stream mesocosm communities to a linear alcohol ethoxylate (LAE) surfactant were studied to (i) assess the relationship between laboratory and field-scale tests; (ii) develop NOECs for responding taxa; and (iii) provide data to develop an aquatic risk assessment for alcohol ethoxylates. The LAE was a mixture of C9--11 linear alcohols with an average of six ethylene oxide (EO) units per mole of alcohol. Twelve stream mesocosms were used to test the effects of five concentrations of the LAE on periphyton, aquatic macrophytes, invertebrates and fish during a 30-day exposure. Vascular plants were unaffected at 11.4 mg L−1, the highest surfactant concentration tested, but various periphyton parameters were altered at lower concentrations. The effects on periphyton were attributed to grazing by resident invertebrates. Invertebrate densities were affected at LAE concentrations above 2.0 mg L−1. Fathead minnows were particularly sensitive to LAE with a NOEC of 0.73 mg L−1 for egg production and larval survival. Bluegill were less sensitive than fathead minnows, with a NOEC for survival and growth of 5.7 mg L−1. The stream mesocosm results for fish and invertebrates were similar to those obtained using laboratory single-species tests