Epilithic diatoms as indicators of stream condition in arid lotic ecosystems of the american southwest.

The objective of this study has been to investigate whether epilithic diatoms could be used as a tool for assessing the condition of small to medium sized Arizona streams. Eighty-four perennial streams throughout the state were sampled during spring months of 1993, 1994 and 1995. One hundred and ninety-five samples were collected from 115 sites for water chemistry, epilithic diatoms, and stream characteristics. Exploratory analysis techniques were employed to determine if unique diatoms assemblages could be associated with any physical stream characteristics or water chemistry constituents. Multivariate and univariate analysis techniques failed to uncover any relationships between diatom species and environmental variables. Samples were dominated by species having ubiquitous distributions and wide environmental tolerance.hydrology collectio