Basic Functional Differences Between Streams and Lakes

Differences between lake and stream dynamics are largely the result of differences in the location of energy fixation and the water residence time. Streams are primarily heterotrophic systems with energy fixed in the terrestrial environment rather than the stream itself and they are much more dependent on their watershed. Energy fixation and decomposition are spatially separated from each other. Although lakes are also dependent on their watersheds largely as the source of nutrients, most of the activity occurs in the water. In a lake, energy fixation and utilization of that energy by other organisms are not as spatially separated. Organisms in lakes and streams also tend to differ, due to the fact that stream organisms experience flowing water currents. The majority of primary producers and consumers in streams are benthic organisms that spend much of their time closely associated with the substrate. Because many lakes stratify, and have bottom waters that are limited in light and nutrients, the main challenge for organisms in many lakes is to remain suspended in the water column.