1. Photosynthesis - Inputs
carbon dioxide,
water,
chlorophyll
certain visible wavelengths of light
TO PRODUCE –
organic matter
oxygen

2. Photosynthesis – energy transformation
transformation of light energy
into the chemical energy of organic matter

3. Respiration - Inputs organic matter oxygen TO PRODUCE Carbon dioxide
Water
WITHOUT Oxygen
carbon dioxide
other waste products are formed

4. Respiration - Outputs
Energy is released in a form available for use by living organisms,
but is ultimately lost as heat.

5. Primary Productivity What do “producers” gain?
Energy-rich organic compounds from inorganic materials through photo- and chemosynthesis
These energy rich compounds can be used in producing more of themselves either through growth or reproduction
Production = the incorporation of energy and materials into the bodies of organisms

6. primary productivity
“the quantity of organic material produced, or solar energy fixed, by photosynthesis in green plants per unit time” (IB definition)
Rate at which autotrophs synthesize new biomass

7. gross primary productivity (GPP)
Total amount of organic material fixed by autotrophs
Result of photosynthesis (or chemosynthesis)
CO2 + H20 + light energy  glucose + O2

8. net primary productivity (NPP)
Rate of production of biomass potentially available to consumers (herbivores)
Not all of the total productivity (energy) goes into making biomass (growth and reproduction)
Some productivity is used in the autotroph’s own life processes (respiration) and this energy is ultimately lost as heat
So, NPP = GPP - R

9. Calculating/Measuring Primary Productivity
Productivity Review
Calculating/Measuring Primary Productivity

10. The Formula NPP = GPP – respiration
Gain in energy or biomass per unit time AFTER respiratory losses
GPP less the biomass or energy used by autotrophs in respiration
Expressed as
Energy per unit area per unit time e.g. J/m2/yr
Biomass added per unit area per unit time e.g. g/m2/yr

11. Light-Dark Bottle Technique
Measure O2 production in light and dark bottles
Light bottle: photosynthesis and respiration
Dark bottle: respiration only
Determine
GPP = Light - Dark
NPP = Light - Initial
Respiration= Initial – Dark

12. Measuring Primary Productivity
Harvest method - measure biomass change over time and express as biomass per unit area per unit time Destructive!
CO2 assimilation - measure CO2 uptake in photosynthesis and release by respiration
Assume any CO2 removed is incorporated into organic material by photosynthesis
Use dark bottle to measure respiration in absence of photosynthesis to get GPP
CO2 is difficult to measure in aquatic systems

13. Factors that Affect Primary Productivity
Solar radiation: quality (type) of light ­quantity of light ­ productivity (to a point when too much light will inhibit photosynthesis)
Temperature: ­temp. Þ­ productivity (to a point when high temperatures can denature enzymes)
CO2: ­ CO2 ­ productivity (since CO2 is an input)
H2O:­ H2O ­ productivity (again since H2O is an input)

14. Therefore…
The least productive ecosystems are those with limited heat and light energy, limited water and limited nutrients
The most productive ecosystems are those with high temperatures, lots of water, light and nutrients