Investigation of diatom populations in rhithron and potamon communities in Oak Creek, Arizona

A study on diatom populations using artificial glass substrates was made in Oak Creek, Arizona. A total of 41 diatom species were recorded with quantitative and qualitative changes in diatom populations measured between rhithron and potamon zones. Notably, there was a distinct change from an epilithic cold water flora (e.g. Meridion circulare) in the rhithron zone to an epiphytic warm water flora (Cocconeis spp, Epithemia spp) in the potamon zone. A decrease in diatom diversity was also noted between the rhithron and the potamon zone. Colonization rates in the rhithron zone were greatest at slower current velocities (e.g. 4.5-35.0 cm/sec) for short incubation periods (3 weeks). Nitzschia palea and Gomphonema parvulum were very common in various regions of the stream bed suggesting nutrient-rich conditions.