title: Bifenthrin Causes Trophic Cascade and Altered Insect Emergence in Mesocosms: Implications for Small Streams.
abstract: Direct and indirect ecological effects of the widely used insecticide bifenthrin on stream ecosystems are largely unknown. To investigate such effects, a manipulative experiment was conducted in stream mesocosms that were colonized by aquatic insect communities and exposed to bifenthrin-contaminated sediment; implications for natural streams were interpreted through comparison of mesocosm results to a survey of 100 Midwestern streams, USA. In the mesocosm experiment, direct effects of bifenthrin exposure included reduced larval macroinvertebrate abundance, richness, and biomass at concentrations (EC50's ranged from 197.6 to 233.5 ng bifenthrin/g organic carbon) previously thought safe for aquatic life. Indirect effects included a trophic cascade in which periphyton abundance increased after macroinvertebrate scrapers decreased. Adult emergence dynamics and corresponding terrestrial subsidies were altered at all bifenthrin concentrations tested. Extrapolating these results to the Midwestern stream assessment suggests pervasive ecological effects, with altered emergence dynamics likely in 40% of streams and a trophic cascade in 7% of streams. This study provides new evidence that a common pyrethroid might alter aquatic and terrestrial ecosystem function at the regional scale.
authors.affiliation: U.S. Geological Survey , Fort Collins Science Center, 2150 Centre Avenue, Bldg. C, Fort Collins, Colorado 80526, United States.
authors.forename: Holly A
authors.initials: HA
authors.lastname: Rogers
authors.affiliation: U.S. Geological Survey , Fort Collins Science Center, 2150 Centre Avenue, Bldg. C, Fort Collins, Colorado 80526, United States.|U.S. Geological Survey , Colorado Water Science Center, Lakewood, Colorado 80225, United States.
authors.forename: Travis S
authors.initials: TS
authors.lastname: Schmidt
authors.affiliation: U.S. Geological Survey , Fort Collins Science Center, 2150 Centre Avenue, Bldg. C, Fort Collins, Colorado 80526, United States.|Department of Fish, Wildlife, and Conservation Biology, Colorado State University , Fort Collins, Colorado 80523, United States.
authors.forename: Brittanie L
authors.initials: BL
authors.lastname: Dabney
authors.affiliation: U.S. Geological Survey , California Water Science Center, Sacramento, California 95819, United States.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Hladik
authors.affiliation: U.S. Geological Survey , Texas Water Science Center, Austin, Texas 78754, United States.
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Mahler
authors.affiliation: U.S. Geological Survey , Texas Water Science Center, Austin, Texas 78754, United States.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Van Metre
mesh_terms: D000818:Animals; D018533:Biomass; D017753:Ecosystem; D007313:Insecta; D011722:Pyrethrins / Q000633:toxicity*; D045483:Rivers
chemical_list: D011722:Pyrethrins; C099952:bifenthrin