Effects of rotenone on aquatic invertebrate communities in prairie wetlands

Abstract

We assessed the effects of rotenone on aquatic invertebrate communities by comparing four prairie wetlands treated with rotenone to four control sites. Data collected one week before and three weeks after treatment in the fall of 1998 were paired to assess short-term effects, while data collected in spring 1998 and spring 1999 were paired to assess longer-term effects and recovery rates. Data were collected on 14 taxa of benthic invertebrates collected in Ekman grab samples, and 23 taxa of planktonic-nektonic invertebrates collected in water-column samples. Each data set was analyzed separately with redundancy analysis to assess effects in the two habitats sampled. Significant short-term effects were detected on invertebrates in the water column and abundance of several taxonomic groups declined sharply after treatment. The greatest declines were observed in zooplankton abundance; effects on macroinvertebrates were much less pronounced. Suppression of water-column taxa was short-lived, as significant effects were no longer evident during May 1999. In contrast, no significant short-term effect was evident in the benthic taxa. Our results indicate that fall applications of rotenone may briefly suppress plankton communities, but effects are short-lived. From a fisheries management perspective, fall applications may minimize effects on invertebrate communities and facilitate rapid recovery.