Primary Productivity – the production of energy by autotrophs, usually measured as biomass per unit time.

Secondary Productivity – the biomass gained by heterotrophs as they feed. Usually measured as biomass per unit time.

Gross Productivity (GP) – total gain in energy or biomass per unit time.

Gross Primary Productivity (GPP) – gained through photosynthesis by producers.

Gross Secondary Productivity (GSP) – gained through absorption by consumers.

Net Productivity (NP) – the gain in energy or biomass remaining after the deduction of losses from respiration (R). This is the biomass available to subsequent consumers.

Net Primary Productivity (NPP) – the gain by producers in energy or biomass minus respiratory losses (R).

Net Secondary Productivity (NSP) – the gain in energy or biomass by consumers minus respiratory losses (R).