Action Principles as Determinants of Ecosystem Structure: The Autonomous Lake as a Reference System

Abstract

Action in theoretical physics is an abstract quantity describing the overall 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 universal, ecosystems must be structured on interaction between this principle of least action and an overriding Principle of Most Action. Most action implies energy acquisition, concentration, and conservation. In an autonomous ecosystem a trophic hierarchy is formed in which, for stability, the action increases at each hierarchical level. We predicted that energy density (in joules per gram), being one of the components of most action, must increase at each level along the food chain. This prediction was tested in Keyhole Lake, a small Arctic lake in the Canadian Northwest Territories, and found to be substantiated. The major non—conformity with the hypothesis was found in the zooplankton, which at all times showed the highest energy density. We concluded that the plankton forms an essentially separate compartment of the ecosystem. Total biomass energy in each hierarchal level confirmed the existence of an energy pyramid, in which the relationship between levels exhibited the characteristics of an inverse cooling curve. An autonomous lake, such as Keyhole Lake, may be regarded as the nearest approach in the natural world to a reference system, against which other systems may be evaluated.