Supplement 1. The data sets analyzed in this paper.

File List Data_files.zip -- zip file containing the four tab-separated ASCII data files listed below. Primary_dataset.txt -- the complete data set used in analyses and presented in Table 1 and Fig. 2 of the article. Ordination_data.txt -- data used to ordinate the 473 streams in Fig. 1. Species_densities.txt -- a site × species matrix of periphyton densities on sampling tiles (precursor to estimating rates of biomass accrual). Species_productivities.txt -- a site × species matrix of periphyton productivities (rate of biomass accrual) on the sampling tiles.<br> Description The file Data_files.zip contains four tab-separated ASCII data files. Each of these four files is described in detail below: File 1 = Primary_dataset.txt -- the summarized dataset used in analyses and presented in Table 1 and Fig. 2. Variables by column are: 1 = U.S. Geological Survey (USGS) stream gauging station. 2 = Description of gauging station location. 3 = USGS Hydrologic Unit Code (HUC). 4 = Latitude of gauging station (degrees). 5 = Longitude of gauging station (degrees). 6 = The Environmental Protection Agency's Type III ecoregion (see reference to Omerik and Griffith 1991 in paper). These denote different shaded areas in Fig. 1B of our paper. 7 = Categorical grouping of naturally occurring stream "clusters" where one or more streams in each study group were located within a 48-km radius in the same ecoregion. These denote polygons in Fig. 1B of our paper. 8 = The coefficient of variation of mean daily stream discharge (Q) from 1 October 1989 to 30 September 1999. 9 = The temporal predictability of mean daily discharge, calculated as Colwell's index (see reference to Colwell 1974 in paper) 10 = The coefficient of variation of mean monthly stream discharge (Q) from 1 October 1989 to 30 September 1999. 11 = The temporal predictability of mean monthly discharge, calculated as Colwell's index (see reference to Colwell 1974 in paper) 12 = The mean number of floods per year, with a flood defined as any Q exceeding the 1.67 year recurrence interval. 13 = The temporal predictability of floods, calculated as Colwell's index (see reference to Colwell 1974 in paper) 14 = Factor scores from PC1 used to ordinate streams in Fig. 1A. 15 = Factor scores from PC2 used to ordinate streams in Fig. 1A. 16 = The study group is the stream disturbance category determined from the ordination of streams by PC1 and PC2 (see Fig. 1A). LD stands for relatively low disturbance streams while HD stands for relatively high disturbance streams. 17 = Day of water year on which periphyton were collected from sampling tiles. Note that the USGS water year begins on 1-October. 18 = The number of days that tiles were incubated in the stream prior to sampling. 19 = Periphyton species richness on sampling tiles, which includes all taxa of Bacillariophyceae, Cyanobacteria, Chlorophyceae, Euglenophyceae, and Pyrrophyta. 20 = Net production of periphyton, taken to be the rate of biomass accumulation on the sampling tiles (micrograms cm²/d) . 21 = The expected productivity of the periphyton assemblage (micrograms cm²/d) determined from the median regional productivity of each taxon (see Eq. 2 in text). 22 = Percent canopy cover above each sampling tile meaured with a densiometer and spatially averaged for the six tiles taken from the stream. 23 = Width of the wetted stream channel (in meters). 24 = Conductivity (microS/cm) of a single stream water sample measured with an Orion QuikChek probe. 25 = Stream drainage area (km²), as reported on the USGS NWISWeb. 26 = Mean invertebrate herbivore biomass (g/m²) in three replicate 900-cm² Surber samples taken from the same stream riffles in which periphyton sampling tiles were placed. 27 = Watershed export of Total Nitrogen (kg/d) predicted for the hydrologic unit code (HUC) based on the SPARROW modeling program of the USGS (see references to Alexander et al. 1998 and 2004 in text). 28 = Watershed export of Total Phosphorus (kg/d) predicted for the hydrologic unit code (HUC) based on the SPARROW modeling program of the USGS (see references to Alexander et al. 1998 and 2004 in text). 29 = pH of a single stream water sample 30 = Mean water depth (cm) measured directly above the replicate sampling tiles. 31 = Stream water temperature, in degrees Celsius 32 = Water velocity (m/s) measured 3–5 mm above each sampling tile using a Valeport 8005/801 electromagnetic probe. Velocity is the mean of a 25-s time series with data spatially averaged across the replicate tiles collected. 33 = Turbulence, taken to be the standard deviation of velocity for the 25-sec time series. Cells with missing values are delimited by "." To verify that the file has downloaded properly, column sums and the number of cells with "." can be compared to the following: -- TABLE: Please see in attached file. -- n/a = not applicable, column is text. File 2 = Ordination_data.txt -- contains data used to ordinate the 473 streams displayed in Fig. 1. Variables by column are: 1 = U.S. Geological Survey (USGS) stream gauging station. 2 = Description of gauging station location. 3 = Latitude of gauging station (degrees). 4 = Longitude of gauging station (degrees). 5 = The coefficient of variation of mean daily stream discharge (Q) from 1 October 1989 to 30 September 1999. 6 = The temporal predictability of mean daily discharge, calculated as Colwell's index (see reference to Colwell 1974 in paper) 7 = The coefficient of variation of mean monthly stream discharge (Q) from 1 October 1989 to 30 September 1999. 8 = The temporal predictability of mean monthly discharge, calculated as Colwell's index (see reference to Colwell 1974 in paper) 9 = The mean number of floods per year, with a flood defined as any Q exceeding the 1.67 year recurrence interval. 10 = The temporal predictability of floods, calculated as Colwell's index (see reference to Colwell 1974 in paper) 11 = Factor scores from PC1 used to ordinate streams in Fig. 1A. 12 = Factor scores from PC2 used to ordinate streams in Fig. 1A. To verify that the file has downloaded properly, column sums can be compared to the following: -- TABLE: Please see in attached file. -- n/a = not applicable, column is text. File 3 = Species_densities.txt -- a site (rows) by species (columns) matrix of periphyton densities on the sampling tiles (number of individual cells per square cm). Each column has the species ID as the header, with that ID followed by a D = diatom (Bacillariophyceae), CY = Cyanobacteria, CH = Chlorophyceae , EU = Euglenophyceae, or PY = Pyrrophyta. Cells with a "." indicate the taxon was not found on sampling tiles placed in that site. To verify that the file has downloaded properly, column sums and the number of cells with "." can be compared to the following: -- TABLE: Please see in attached file. -- n/a = not applicable, column is text. File 4 = Species_productivities.txt -- a site (rows) by species (columns) matrix of periphyton productivities on the sampling tiles (micrograms of biomass accrual cm²/ d). Each column has the species ID as the header, with that ID followed by a D = diatom (Bacillariophyceae), CY = Cyanobacteria, CH = Chlorophyceae , EU = Euglenophyceae, or PY = Pyrrophyta. ...