Net Primary Productivity Calculator
NPP from GPP and respiration, or GPP, NPP and R from light and dark bottle oxygen data.
NPP = GPP − R. In the light/dark bottle method: NPP = light − initial, R = initial − dark, and GPP = light − dark (all in mg O₂/L). Multiply O₂ by 12/32 (0.375) to convert to mg of carbon fixed.
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How to use it
- Choose GPP and respiration, or the light and dark bottle method.
- Enter the values (dissolved oxygen in mg/L for bottles, and the incubation time).
- Read NPP, GPP and respiration, and the carbon equivalent.
What you enter
- GPP and respiration, or initial, light and dark bottle oxygen
- Incubation time
What you get
- NPP
- GPP
- Respiration
- Carbon fixed
Formula
NPP = GPP − R | Light/dark bottle: NPP = LB − IB, R = IB − DB, GPP = LB − DB | C = O₂ × 12/32
Worked example
Input: Initial 8.0, light 9.6, dark 7.1 mg O₂/L, 4 h
Result: NPP 1.6, R 0.9, GPP 2.5 mg O₂/L
Per hour: NPP 0.4 mg O₂/L, or 0.15 mg C/L fixed.
Questions
How do you calculate net primary productivity?
Subtract the energy or carbon used in plant respiration from gross primary productivity: NPP = GPP − R.
How does the light and dark bottle method work?
Oxygen rises in the light bottle from photosynthesis minus respiration (NPP) and falls in the dark bottle from respiration only (R). Their difference is GPP.
How do I convert oxygen to carbon?
With a photosynthetic quotient of 1, each mg O₂ released matches 12/32 = 0.375 mg of carbon fixed.
Which ecosystems have the highest NPP?
Tropical rainforests, swamps and marshes, and coral reefs, around 2,000–2,500 g/m²/yr of dry matter; open ocean and deserts are among the lowest per area.
Limitations
- Assumes respiration is the same in light and dark and a photosynthetic quotient of 1.
References
- Lieth H, Whittaker RH, eds. (1975). Springer-Verlag.
- Wetzel RG, Likens GE (2000), 3rd ed. Springer, chapter 13.
Related reading
More Ecology
All free tools · By Dr. Zubair Khalid, DVM, MS, PhD.