A FLOW-THROUGH LABORATORY MICROCOSM SUITABLE FOR ASSESSING EFFECTS OFSURFACTANTS ON NATURAL PERIPHYTON

A flow-through laboratory microcosm using a proportional dilutor syste m was developed to assess effects of toxicants on algal periphyton com munities. Periphyton was colonized on clay tile substrata in the field (Little Miami River, Ohio) and transferred to the laboratory for 28-d ay long-term exposures to copper and,two anionic surfactants, dodecyl (C-12) alkyl sulfate (AS), and C-14.5 alkyl ethoxylate sulfate (AES). Five exposures of increasing test chemical concentration plus a contro l treatment were replicated three times and sampled weekly. Periphyton communities grew well under laboratory conditions, were compositional ly stable, and fairly complex. Typical community richness ranged from 16 to 22 taxa per sampled substrate. Measurement end points were chose n to assess community and population level responses that were both ec ologically relevant and acceptable for interpretation by environmental regulatory authorities. Algal communities were sensitive to copper ex posure and exhibited a community-level no observed effect concentratio n (NOEC) of 9.5 mu g/L consistent with predictions by single-species s tudies. AS and AES exposures resulted in algal community-level NOECs o f >553 and >608 mu g/L, respectively, which were consistent with singl e-species toxicity data. Measured end points had coefficients of varia tion consistently below 20%, indicating their high degree of reproduci bility. The test system is a viable option to classical algal single-s pecies studies useful in determining responses of algal periphyton to xenobiotic chemical exposures. (C) 1996 by John Wiley & Sons, Inc.