This datset contains operational taxonomic units for epilithon eukaryotes (water samples): Approximate location of sampling sites was determined from maps to provide good spatial coverage of the Wold River through to the Tamar River. Exact sites were determined in the field, considering accessibility and other logistics. The exact location of each sample site was determined using a Garmin GPS12. Three stones were taken from each of the 20 locations and epilithon removed from a defined...