ACTION PRINCIPLES AS DETERMINANTS OF ECOSYSTEM STRUCTURE - THE AUTONOMOUS LAKE AS A REFERENCE SYSTEM

Action in theoretical physics is an abstract quantity describing the o verall motion of a system; action has the dimensions of energy x time (in joule-seconds). The Principle of Least Action states that physical systems follow that path for which the action has the least value. By analogy, we hypothesize that, if the principle of least action is uni versal, ecosystems must be structured on interaction between this prin ciple of least action and an overriding Principle of Most Action. Most action implies energy acquisition, concentration, and conservation. I n an autonomous ecosystem a trophic hierarchy is formed in which, for stability, the action increases at each hierarchical level. We predict ed that energy density (in joules per gram), being one of the componen ts of most action, must increase at each level along the food chain. T his prediction was tested in Keyhole Lake, a small Arctic lake in the Canadian Northwest Territories, and found to be substantiated. The maj or non-conformity with the hypothesis was found in the zooplankton, wh ich at ail times showed the highest energy density. We concluded that the plankton forms an essentially separate compartment of the ecosyste m. Total biomass energy in each hierarchical level confirmed the exist ence of an energy pyramid, in which the relationship between levels ex hibited the characteristics of an inverse cooling curve. An autonomous lake, such as Keyhole Lake, may be regarded as the nearest approach i n the natural world to a reference system, against which other systems may be evaluated.