Index >> Microbial Ecology of Different Ecosystems>> Structure of the Lotic Habitat

The significant phytoplankton populations that usually exist contribute to a higher rate of primary productivity than that found in fast-moving streams. The level of productivity is dependent upon water temperature and the amount of nutrient input received from the surrounding environment, and therefore subject to seasonal variation. The diversity of consumer organisms varies according to the physical conditions and vegetation. Planktonic populations are relatively high, although not as dense as those found in lakes. In fast-moving streams, there is very little primary production in the open-water habitat, due to the velocity and turbulence of the current. Populations of consumer organisms (mainly particulate feeders) are low. Riffle areas provide valuable habitat for juvenile trout and salmon. Pools are important resting areas for several fish species, including Atlantic salmon. The quality of these areas can be adversely affected when shade trees are removed from the banks.