Rapidly Flowing Waters - Biota of Rivers

In the rapidly flowing section of the river, the water current is the dominant feature. Everything that is not attached or weighed is swept away, including organisms and sediments alike. The substratum tends to be either gravel or rock whose fragments are smoothed and rounded by the water. The habitat itself is diverse, as different microhabitats occur here -

1. On the surface of rock fragments
2. Between rock fragments and
3. Beneath rock fragments.

The differences in these microhabitats are due to the differences in the force of water currents occurring in each of them. As a result each microhabitat houses different types of organisms.