Composition of streambed substrata was computed from the number of transect measurements for a given substratum type relative to the total number of measurements. Percentage coverage of biofilm and filamentous green algae along the reach was calculated from the number of transect measurements for a given patch relative to the total number of measurements. On each transect we also collected 3 samples of biofilm and filamentous green algae (i.e., n=18 for the entire reach) from a known area for chlorophyll a and biomass measurements. These samples were kept frozen until analysis.