Communities of algae in North Carolina streams and their seasonal relations

The material presented summarizes the results of a four-year study of the algae in the streams of North Carolina - one of the southeastern United States. Many small streams and eleven rivers in the Coastal Plain, Piedmont and Mountain areas were sampled at random and in some cases in a systematic manner. Important habitat factors were measured and numbers of plankton organisms in several rivers determined. The communities characteristic of the major types of streams are described, together with seasonal changes which occur. It is pointed out that there is considerable variation in the species composition of communities in the smaller streams, but that the plankton communities of rivers are very similar. Diatoms (Bacillariophyceae) were found to be important in most communities with Chlorophyceae second in importance. The importance of a current to the lotic aufwuchs communities of rapids is described, and also the effects of temperature, light and mineral content of water on the major communities.