Volume 52, Number 1, May 2005:
Stream Ecology

Text-only version


ISSUE HOME PAGE

ABOUT THIS ISSUE
- about KSN
- about the author

IN THIS ISSUE
- introduction
- stream communities
- physical characteristics of streams
- biological features of streams
- common groups of stream organisms

Stream Ecology
by Carl Prophet

STREAM COMMUNITIES

Ecologists use the term community to designate a group of different types of organisms associated in a certain physical setting. A pond, a forest, or a decaying log is each an example of a community. Each of these examples of a community is distinguished by its physical environment and by the types of organisms which live and interact there. As one can note from these examples, the size (area or volume) of a community can be either comparatively large or small. Technically, the ecological concept of community is a bit more complex than just described, but the basic idea is clear.

Ecologists whose main interest is focused on aquatic systems divide aquatic communities into two basic categories, lotic and lentic. Although other distinctions between them can be made the simplest way to think of these two terms is that one describes standing water and the other flowing water. A lake is an example of a lentic community. The water is retained for a time within a basin and there is little visible movement of the water other than surface waves or ripples. A stream is a lotic community. The water flows down a channel from a higher to a lower elevation. The water moving past a given point along an unobstructed stream channel continues moving downstream and never circulates past that point again.

Streams come in all sizes and types. In Kansas, when first given an officially recognized name it was customary to designate large streams as rivers and their tributaries as creeks. All would agree that major streams are properly designated as rivers, but in different parts of the United States other terms such as brook or run may be applied to the name of a small stream rather than creek.

Photo caption: Dendritic pattern of watershed streams.