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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 (EC50s ranged 197.6 – 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. This data file includes counts and identifications of aquatic insect larvae collected from mesocosms at the end of the experiment. Included is an identifier for each mesocosm, size class of each individual insects, data on quality control, and finally estimates of biomass for each taxa.

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Name	Format	Description	Link
	55	The metadata original format	https://data.usgs.gov/datacatalog/metadata/USGS.5797d1f6e4b0589fa1c61b26.xml
	55	Landing page for access to the data	http://dx.doi.org/10.5066/F7SX6BBZ

Aquatic insect community data and taxa list for larvae collected from mesocosms exposed to bifenthrin

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