Plants and animals of running waters

Quite an opposite relationship is true between the running water and animals. While the aquatic animals usually have no significant effect on the properties of the stream, the problems caused by running water are resolved by several marked adaptations differentiating them from the fauna of stagnant waters [4, 12]. The most important methods of adaptation are as follows  

In slower flows (fluviatile) the bottom is often soft and unsteady, and consists mostly of gravel, sand or mud. The least suitable base is sand 

The animal communities on a gravel bed are also not rich in variety. Among the insects, some larvae of epliemers can be found here, as well as those of dragon-flies and others. In sections with larger stones and clean water it is sometimes possible to find — now rather rare — Margaritana margaritifera L. 

A muddy bottom predominates on the slow sections of streams enabling sedimentation of fine particles. Communities in the mud with a high content of organic matter are more numerous as regards population, but on the other hand, in the muds poorer in organic matters more species occur 

On the surface of slow streams small animals live, whose community forms the so-called pleuston. The most numerous are those from the Gerris genus (G. paladum, G. odontogaster, G. lacustris). 

---