1. Productivity Review and Calculations

2. Recap of Definitions! Key termDefinition ProductivityThe total gain in energy of the producers. Primary ProductivityThe total gain in energy/biomass per unit area per unit time. Secondary Productivity Production per unit area per unit time Gross Productivity (GP)The gain in energy/biomass per unit area per unit time remaining after allowing for respiration losses which is passed onto the herbivores. Gross Primary Productivity (GPP) The rate at which energy/biomass is formed through photosynthesis Net Productivity (NP)The gain in energy/biomass per unit time remaining after allowing for respiration (R) loses. Net Primary Productivity (NPP) The rate at which primary material is synthesised into animal tissue per unit area in a given time.

3.  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 Important Calculations

4.  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 10 6 and the gross primary productivity = 2.8 x 10 4 ?  What is the GPP of an ecosystem if the NPP is 1660 kJm -2 yr -1 and the energy lost during respiration is 573 kJm -2 yr -1 ?  What is the NPP if the GPP is 2700 kJm -2 yr -1 and the energy used in respiration is 1850 kJm -2 yr -1 ? Calculating Productivity Values

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

6. Energy Flow Diagrams Information from energy flow diagrams can be used to calculate ecological efficiencies Photosynthetic Efficiency = Net production ÷ Light Energy Absorbed 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: Energy flow diagrams illustrate energy flow through communities and include values for respiratory losses and energy flow through the decomposers

7. 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 Use information from the energy flow diagram to:

8. Gross Primary Production is the total energy fixed by photoautotrophs during photosynthesis Net Primary Production is the energy stored as biomass (gross production – energy lost as heat in respiration) Photosynthetic Efficiency = 3.7 x 10 4 ------------ x 100 172 x 10 4 = 2.15%

10. GPP = 24 x10 6 kJ m -2 year -1 Photosynthetic efficiency = 1.3% NPP = 800 kJ m -2 year -1 NPP = 200 kJ m -2 year -1 NPP = 69.7 x 10 3 kJ m -2 year -1 114 x 10 3 kJ m -2 year -1