BETWEEN-YEAR VARIATION OF PERIPHYTON COMMUNITY STRUCTURE IN 2 APPALACHIAN HEADWATER STREAMS

We used unglazed quarry tiles to survey periphyton community structure in two small Appalachian mountain streams from January through April in 1990, 1991, and 1992. Mean periphyton cell densities were greatest in 1990 (maximum of 1.3 x 10(8) cells cm-2), the year with the fewest periods of high discharge; cell densities were lowest in 1998 (maximum of 5.9 x 10(5) cells cm-2), the year characterized by the most period s of high discharge, and intermediate in 1992 (maximum of 2.1 x 10(6) cells cm-2). Mean cell densities of the dominant alga, the cyanophyte Chamaesiphon sp., followed this pattern, but some taxa of diatoms did not.