In this exercise, students set up bottle enrichments for phototrophic microbes using river sediment and then, using representative controls, they then view and describe wet mounts of representative oxygenic algae and cyanobacteria, and anoxygenic purple bacteria. Following 2-3 weeks incubation, students characterize pigmented enrichments using basic microscopy and pigment extraction and analysis, the latter of which requires a spectrophotometer. Using provided tables and their text, they classify enriched phototrophs using pigment absorption data, cell shape/organization, and growth conditions such as the presence/absence of sulfur.