In this exercise, students set up bottle enrichments for phototrophic microbes using river sediment and then, using representative controls, they view and describe wet mounts of representative oxygenic algae and cyanobacteria and anoxygenic purple bacteria. Following 2 to 3 weeks of 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 textbook, they classify enriched phototrophs using pigment absorption data, cell shape and organization, and growth conditions such as the presence or absence of sulfur.