EFFECTS OF SHORT-TERM PULSES OF ATRAZINE ON ATTACHED ALGAL COMMUNITIES IN A SMALL STREAM

The impact of short-term atrazine exposures on attached algal community composition and standing crop was investigated during the summer in a small, spring-fed stream in western Nebraska. Replicate trays of clay tiles were anchored to the stream bed, allowed to colonize for two weeks, then enclosed in situ with plexiglass boxes and exposed to a pulse of atrazine at 0, 2, 30, or 100 μg/L for 24 hr. A second 24-hr atrazine pulse was applied two weeks later. Atrazine did not have a significant effect on cell densities of the dominant algae or the ash-free dry weight biomass of the periphyton community. The absence of observed treatment effects was likely due to the low but realstic levels of atrazine used and the transient nature of the application. Sediment deposition had a much greater influence on the attached algal community than short-term pulses of the herbicide. © 1990 Springer-Verlag New York Inc.