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Productivity Review and Calculations

Productivity Review and Calculations. Recap of Definitions!. Important Calculations. How do we calculate GPP? GPP = NPP + R How do we calculate NPP? NPP = GPP – R How do we calculate GSP: GSP = food eaten – faecal losses Or… NSP + R How do we calculate NSP N SP = GSP – R.

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Productivity Review and Calculations

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  1. Productivity Review and Calculations

  2. Recap of Definitions!

  3. Important Calculations • How do we calculate GPP? GPP = NPP + R • How do we calculate NPP? NPP = GPP – R • How do we calculate GSP: GSP = food eaten – faecal losses Or… NSP + R • How do we calculate NSP NSP = GSP – R

  4. Calculating Productivity Values • Some easy ones to start you off! • What is the % energy from sunlight that is fixed as GPP if the total energy from the sun in 3 x 106 and the gross primary productivity = 2.8 x 104? • What is the GPP of an ecosystem if the NPP is 1660 kJm-2yr-1 and the energy lost during respiration is 573 kJm-2yr-1? • What is the NPP if the GPP is 2700 kJm-2yr-1 and the energy used in respiration is 1850 kJm-2yr-1?

  5. Calculating Productivity Values Now for some slightly harder ones!

  6. Energy Flow Diagrams Energy flow diagrams illustrate energy flow through communities and include values for respiratory losses and energy flow through the decomposers Information from energy flow diagrams can be used to calculate ecological efficiencies Ecological Efficiency is the net production of new biomass at each trophic level as a percentage of the total energy flowing through that trophic level Therefore, for photoautotrophs, photosynthetic efficiency is determined as: Photosynthetic Efficiency = Net production ÷ Light Energy Absorbed

  7. Use information from the energy flow diagram to: • Explain the meaning of the term Gross Primary Production • Explain the meaning of the term Net Primary Production • Calculate the Photosynthetic Efficiency of the phytoplankton

  8. Gross Primary Production is the total energy fixed by photoautotrophs during photosynthesis Photosynthetic Efficiency = 3.7 x 104 ------------ x 100 172 x 104 = 2.15% Net Primary Production is the energy stored as biomass (gross production – energy lost as heat in respiration)

  9. NPP = 800 kJ m-2year-1 Photosynthetic efficiency = 1.3% GPP = 24 x106 kJ m-2year-1 NPP = 200 kJ m-2year-1 NPP = 69.7 x 103 kJ m-2year-1 114 x 103 kJ m-2year-1

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