This resource contains the results of a diphenhydramine dose-response experiment conducted on stream biofilms at a site on the Logan River in northern Utah. We grew stream biofilms on inorganic (fritted glass disc) and organic (cellulose sponge) substrates in the river for 20 days. The biofilm-colonized substrates were then placed as caps on contaminant exposure substrates (CES), 1-oz plastic cups filled with agar amended with diphenhydramine at a series of concentrations (control, 0.5 mM, 0.75 mM, 1.25m M, 2.5 mM, 15 mM). CES were then deployed in the river for 20 days.

At the end of the CES deployment, the biofilm-colonized substrates were used to perform a series of in-stream incubations. We measured respiration and productivity using a modified light-dark bottle incubation method and nitrogen fixation rates using an acetylene reduction assay. We measured biofilm biomass (chlorophyll a, ash-free dry mass) and calculated Autotrophic Index values (calculated as chlorophyll a concentration divided by ash-free dry mass). The CSV file “biomass_function_diphenhydramine” contains summary statistics (mean, standard deviation, count) of respiration rates, gross primary production rates, nitrogen fixation rates, chlorophyll a concentrations, ash-free dry mass, and Autotrophic Index values of biofilms on each diphenhydramine treatment and substrate type. The Word document “methods_diphenhydramine” describes the analytical methods used to measure chlorophyll and ash-free dry mass.

We characterized light availability and nutrient concentrations at the study site. The Word document “methods_diphenhydramine” describes the methods used to measure site characteristics and the analytical methods used to measure nutrient concentrations. The CSV file “site_characteristics_diphenhydramine” contains percent canopy openness, transmitted PAR, transmitted solar shortwave radiation, total nitrogen, total phosphorus, ammonium, nitrate, soluble reactive phosphorus, dissolved total iron, and dissolved ferrous iron concentrations.