ABSTRACT
The concepts of autonomy and, thus, self-regulation are dependent on scales in time and space. Consider the example of pelagic ecosystems. One can talk about pelagic ecosystems as units of self-regulation when the deep water body is sufficiently large for the interactions (material exchanges) within this habitat to dominate over those which operate across habitat boundaries, especially with respect to the littoral zone and the sediments. The difference between small ponds and large systems such as Lake Baikal may be greater than the difference between Lake Baikal and some marine system. Considerations of scale are of vital importance in determining the characteristics of lacustrine habitats and their relationships (e.g. volume/surface area, water retention time, epilimnion depth/total depth determine the influence of sediments and nutrient gradients).
