The net primary productivity ($NPP$) of producers represents the chemical energy store in biomass available for consumer growth and saprobiontic decomposition.

The efficiency of energy transfer between trophic levels is typically low because a large proportion of the chemical energy is lost as heat during respiration.

Ecosystems function as thermodynamically closed systems, meaning that while chemical nutrients are cycled, energy cannot cross the system boundary to enter or exit.

Saprobionts are essential for ecosystem functioning because they recycle chemical elements, such as nitrogen and phosphorus, back into the abiotic environment.