A stream, in simple terms, is a natural body of flowing water. Despite this simple definition, streams are complex ecosystems in which biological, chemical, or physical changes may affect other characteristics. A stream begins at its headwaters and gathers water from runoff, rain, snowmelt, or from underground springs. Streams hold great importance regardless of size or flow. They provide water supplies, a variety of aesthetic values, and are also important wildlife habitats.
Plants provide the base of the food chain in streams.
Field and Laboratory Methods for Macroinvertebrate and Habitat Assessment of Low Gradient, Nontidal Streams. Mayflies and stonefly nymphs as well as bacteria and fungi directly use the fallen plant litter. Branches and leaves become dead plant matter and are eaten by aquatic organisms. The joining of two first order streams creates a second order stream . In turn, the joining of two second order streams create a third order stream.