Definitions of relevant Efficiency and Stress Factors

A general efficiency function and related stressfactors are defined from energy flow conciderations. The efficiency funcion, or index, is related to maximum energy utilization, and stress is defines as total derivatives of the efficieny function. The efficiency funtion can be expressed, for an awqatic ecosystem, in terms of inciedent radiation, total production, total growth and the outflow at the highets trophical level. It i shown that the efficiency in principle can be measuerd for a lake from oxygen balance and hydlogical conciderations. Changes in the efficiency are intiamately connected with the activity at the primary level, which contributes most of the biomass and tehe production in the system. Pertubations on oher levels effects the total system more indirectly than directly and this is the reason for using total rather than partial derivates int the stress defnitions. The beaviour of the efficient function is demonstrated for a three levele Lotka-Volterra-type model with competion.