Epilithic algal density and biovolume datasets at species and genus taxonomic levels and environmental variables. This dataset is associated with the following publication: Fritz, K., R. Kashuba, G. Pond, J. Christensen, S. Decelles, B. Johnson, and D. Walters. Identifying algal indicators for streamflow duration assessment methods in forested headwater streams. ECOLOGICAL INDICATORS. Elsevier Science Ltd, New York, NY, USA, 189: 115080, (2026).