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 ethox ylate (LAE) surfactant were studied to (i) assess the relationship bet ween laboratory and field-scale tests; (ii) develop NOECs for respondi ng taxa; and (iii) provide data to develop an aquatic risk assessment for alcohol ethoxylates. The LAE was a mixture of C9-11 linear alcohol s with an average of six ethylene oxide (EO) units per mole of alcohol . Twelve stream mesocosms were used to test the effects of five concen trations of the LAE on periphyton, aquatic macrophytes, invertebrates and fish during a 30-day exposure. Vascular plants were unaffected at 11.4 mgL(-1), the highest surfactant concentration tested, but various periphyton parameters were altered at lower concentrations. The effec ts on periphyton were attributed to grazing by resident invertebrates. Invertebrate densities were affected at LAE concentrations above 2.0 mgL(-1). Fathead minnows were particularly sensitive to LAE with a NOE C of 0.73 mgL(-1) for egg production and larval survival. Bluegill wer e less sensitive than fathead minnows, with a NOEC for survival and gr owth of 5.7 mgL(-1). The stream mesocosm results for fish and inverteb rates were similar to those obtained using laboratory single-species t ests.