Unifying characteristics of the ecology of running Waters.

http://en.wikipedia.org/wiki/Lotic_system_ecology

The following unifying characteristics make the ecology of running waters unique from that of other aquatic habitats.

• Flow is unidirectional.
• There is a state of continuous physical change.
• There is a high degree of spatial and temporal heterogeneity at all scales (microhabitats).
• Variability between lotic systems is quite high.
• The biota is specialized to live with flow conditions.