Structural characteristics of algal communities in thermally altered artificial streams

Algal community structure on natural substrates of thermally altered artificial streams was studied for one year. The streams were fed by a natural blackwater stream near Aiken, South Carolina. Temperature-related shifts in the abundance of major species were demonstrated. Red algae were absent from a stream heated 12·5°C above ambient, but remained abundant in streams heated 7·5°C or less. Water temperatures above 30°C produced blue-green algal dominance and eliminated several indigenous species. Substrate specificity was exhibited by all major taxa. Several taxa were abundant only on the bottom sediments and some showed a distinct affinity for either sand or silt, the principal bottom types.