Within each transect, algal mats were visually identified as either orange, red, black, or green. Algal and moss samples were collected using a cork borer or a known area of substrate was scraped. Samples were stored in bottles until taken back to the lab for processing. Samples were filtered onto GF/C glass fiber filters. They were then extracted in buffered acetone and analyzed spectrophotometrically using the trichromatic method. Concentrations are reported in units of ug/cm2 for each pigment quantified (chlorophylls a, b, c, carotenoids, and phaeophyton). Carbon, hydrogen and nitrogen samples were air-dried (approximately 60 degrees C), then a weighed amount of algae was taken from the filter and analyzed on a Carlo Erba NA1500NCS element analyzer.