This resource contains the results of a nutrient uptake incubation experiment conducted at a mountain and urban site on the Logan River in northern Utah. The experiments were performed with biofilms grown for 14-15 days on nutrient diffusing substrates (NDS), 1-oz plastic cups filled with agar and capped with a fritted glass disc. We performed the nutrient uptake experiment by incubating biofilm-colonized discs in clear plastic jars filled with stream water spiked with nitrogen (N) and phosphorus (P) at a series of concentrations. The CSV file "nutrient uptake treatments" lists the treatments used in the nutrient uptake experiment at each site. Biofilms were incubated in situ for 2 hours at midday. Samples for dissolved nutrient analysis were collected from the nutrient treatment solutions used to fill the jars and from each jar at the end of the incubation. The dissolved oxygen concentration in each jar was measured at the start and end of the incubation. We calculated nutrient uptake rates as the rate of loss in water nutrients and net primary production as the change in dissolved oxygen concentration. We measured biofilm biomass as chlorophyll a. The CSV file “nutrient uptake results” contains summary statistics (mean, standard deviation, count) of nutrient uptake rates, net primary production rates, and chlorophyll a concentrations in nutrient uptake treatments at each site. The Word document “nutrient uptake analytical methods” contains the analytical methods used to measure nutrient concentrations.

We also examined biofilm nutrient limitation at each site using NDS. We constructed nutrient limitation NDS by filling 1-oz plastic cups with agar amended with either no nutrients (control), 0.5 M NH4-N (N), 0.5 M PO4-P (P), or 0.5 M NH4-N + 0.5 M PO4-P (N+P). NDS were then capped with a fritted glass disc and placed in the stream at each site during the same period that NDS for the nutrient uptake experiment were deployed. Biofilm biomass was measured as chlorophyll a and ash-free dry mass. The CSV file “nutrient limitation results” contains summary statistics of chlorophyll a concentration and ash-free dry mass in each nutrient treatment at each site. The Word document “nutrient uptake analytical methods” contains the analytical methods used to measure chlorophyll and ash-free dry mass.