Ecosystem Productivity

Assessment Statements

• 2.5.2: Describe photosynthesis and respiration in 2.5.2: Describe photosynthesis and respiration in terms of inputs, outputs and energy terms of inputs, outputs and energy transformations.transformations.

• 2.5.5: Define the terms gross productivity, net 2.5.5: Define the terms gross productivity, net productivity, primary productivity, and secondary productivity, primary productivity, and secondary productivityproductivity

• 2.5.6: Define the terms and calculate the values 2.5.6: Define the terms and calculate the values of gross primary productivity (GPP) and net of gross primary productivity (GPP) and net primary productivity (NPP) from given data.primary productivity (NPP) from given data.

• 2.5.7: Define the terms and calculate the values 2.5.7: Define the terms and calculate the values of gross secondary productivity (GSP) and net of gross secondary productivity (GSP) and net secondary productivity (NSP) from given data.secondary productivity (NSP) from given data.

Key terms

• Gross productivity (GP)Gross productivity (GP)• Gross Primary Productivity (GPP)Gross Primary Productivity (GPP)• Gross Secondary Productivity (GSP)Gross Secondary Productivity (GSP)• Net productivityNet productivity• Net Primary Productivity (NPP)Net Primary Productivity (NPP)• Net Secondary Productivity (NSP)Net Secondary Productivity (NSP)• Primary productivityPrimary productivity• Secondary productivitySecondary productivity

Figure 10.1 Photoautotrophs

Photosynthesis in Plants

• Chloroplasts are the location of photosynthesis Chloroplasts are the location of photosynthesis in plantsin plants

• In all green parts of plants – leaves, stems,…In all green parts of plants – leaves, stems,…

• Green color from Green color from chlorophyllchlorophyll (photosynthetic (photosynthetic pigment)pigment)

• Found in cells of Found in cells of mesophyllmesophyll – interior tissue of – interior tissue of leavesleaves

• Gases exchanges through the Gases exchanges through the stomatastomata

• Water enters through Water enters through xylemxylem of roots of roots

Figure 10.2 Focusing in on the location of photosynthesis in a plant

Energy Processes

• Photosynthesis (Green Plants)Photosynthesis (Green Plants)

sunlight +water + carbon dioxide sunlight +water + carbon dioxide oxygen + oxygen + sugarssugars

• Respiration (All living things)Respiration (All living things)

oxygen + sugars oxygen + sugars ATP +water + carbon dioxide ATP +water + carbon dioxide

• ATP is molecular energy storageATP is molecular energy storage

Producers

• Make their own food - photoautotrophs, Make their own food - photoautotrophs, chemoautotrophschemoautotrophs

• Convert inorganic materials into organic Convert inorganic materials into organic compoundscompounds

• Transform energy into a form usable by Transform energy into a form usable by living organismsliving organisms

Photosynthesis

• Inputs – sunlight, carbon dioxide, waterInputs – sunlight, carbon dioxide, water

• Outputs – sugars, oxygenOutputs – sugars, oxygen

• Transformations – radiant energy into Transformations – radiant energy into chemical energy, inorganic carbon into chemical energy, inorganic carbon into organic carbonorganic carbon

Respiration

• Inputs - sugars, oxygenInputs - sugars, oxygen

• Outputs - ATP, carbon dioxide, waterOutputs - ATP, carbon dioxide, water

• Transformations – chemical energy in Transformations – chemical energy in carbon compounds into chemical energy carbon compounds into chemical energy as ATP, organic carbon compounds into as ATP, organic carbon compounds into inorganic carbon compoundsinorganic carbon compounds

Definitions

1.1. gross productivity – total biomass producedgross productivity – total biomass produced2.2. net productivity – total biomass produced net productivity – total biomass produced

minus amount used by organismminus amount used by organism3.3. primary productivity – productivity at 1primary productivity – productivity at 1stst

trophic leveltrophic level4.4. secondary productivity – productivity at secondary productivity – productivity at

higher trophic levelhigher trophic level5.5. gross primary productivity – rate at which gross primary productivity – rate at which

producers use photosynthesis to make more producers use photosynthesis to make more biomassbiomass

6.6. net primary productivity – rate at which net primary productivity – rate at which energy for use by consumers is stored in new energy for use by consumers is stored in new biomassbiomass

Distribution of World Productivity

Gross Productivity

• Varies across the surface of the earthVaries across the surface of the earth• Generally greatest productivityGenerally greatest productivity

• In shallow waters near continentsIn shallow waters near continents• Along coral reefs – abundant light, heat, nutrientsAlong coral reefs – abundant light, heat, nutrients• Where upwelling currents bring nitrogen & Where upwelling currents bring nitrogen &

phosphorous to the surfacephosphorous to the surface

• Generally lowest Generally lowest • In deserts & arid regions with lack of water but In deserts & arid regions with lack of water but

high temperatureshigh temperatures• Open ocean lacking nutrients and sun only near Open ocean lacking nutrients and sun only near

the surfacethe surface

Ocean Area vs Productivity

Effects of Depth

Net Productivity

• Some of GPP used to stay alive, grow and Some of GPP used to stay alive, grow and reproducereproduce

• NPP is what’s leftNPP is what’s left

• Most NPPMost NPP• Estuaries, swamps, tropical rainforestsEstuaries, swamps, tropical rainforests

• Least NPPLeast NPP• Open ocean, tundra, desertOpen ocean, tundra, desert

• Open ocean has low NPP but its large area gives it Open ocean has low NPP but its large area gives it more NPP total than anywhere elsemore NPP total than anywhere else

Agricultural Land

• Highly modified, maintained ecosystemsHighly modified, maintained ecosystems

• Goal is increasing NPP and biomass of Goal is increasing NPP and biomass of crop plantscrop plants

• Add in water (irrigation), nutrients Add in water (irrigation), nutrients (fertilizer)(fertilizer)

• Nitrogen and phosphorous are most often Nitrogen and phosphorous are most often limiting to crop growthlimiting to crop growth

• Despite modification NPP in agricultural Despite modification NPP in agricultural land is less than many other ecosystemsland is less than many other ecosystems

Productivity Calculations

• Total Primary ProductionTotal Primary Production = Gross Primary = Gross Primary Production (GPP) Production (GPP) Amount of light energy Amount of light energy converted into chemical energy by converted into chemical energy by photosynthesis per unit timephotosynthesis per unit time

• Joules / MeterJoules / Meter22 / year / year

• Net Primary ProductionNet Primary Production GPP – R, or GPP – some GPP – R, or GPP – some energy used for cell respiration in the primary energy used for cell respiration in the primary producers (R = respiratory loss)producers (R = respiratory loss)

• Represents the energy storage available for the Represents the energy storage available for the whole community of consumerswhole community of consumers

• Standing crop = Total living material at a trophic Standing crop = Total living material at a trophic levellevel

More Productivity Calculations

Producers:Producers:• NPP = GPP – RNPP = GPP – R

Consumers:Consumers:• GSP = Food eaten – fecal lossesGSP = Food eaten – fecal losses• NSP = change in mass over timeNSP = change in mass over time• NSP = GSP – RNSP = GSP – R

Measuring Primary Production

• Measure aspects of photosynthesisMeasure aspects of photosynthesis• In closed container measure OIn closed container measure O22 production, production,

COCO22 uptake over time uptake over time• Must measure starting amount in environment Must measure starting amount in environment

then amount added by producersthen amount added by producers• Use dissolved oxygen probe or carbon dioxide Use dissolved oxygen probe or carbon dioxide

sensorsensor• Measure indirectly as biomass of plant material Measure indirectly as biomass of plant material

produced over time (only accurate over long produced over time (only accurate over long timer periods) timer periods) this gives this gives NPPNPP

Light and Dark Bottle Method – for Aquatic Primary Production

• Changes in dissolved oxygen used to Changes in dissolved oxygen used to measure GPP and NPPmeasure GPP and NPP

• Measures respiration and photosynthesisMeasures respiration and photosynthesis

• Measure oxygen change in light and Measure oxygen change in light and opaque bottlesopaque bottles

• Incubation period should range from 30 Incubation period should range from 30 minutes to 24 hoursminutes to 24 hours

• Use B.O.D. bottles Use B.O.D. bottles

• Take two sets of samples measure the Take two sets of samples measure the initial oxygen content in each (initial oxygen content in each (II))

• Light (Light (LL) and Dark () and Dark (DD) bottles are ) bottles are incubated in sunlight for desired time incubated in sunlight for desired time periodperiod

• NPP = L – INPP = L – I

• GPP = L – DGPP = L – D

• R = D – IR = D – I

Light and Dark Bottle Method – for Aquatic Primary Production

Sample Data

Method evaluation

• Tough in unproductive waters or for short Tough in unproductive waters or for short incubation timesincubation times

• Accuracy in these cases can be increased Accuracy in these cases can be increased by using radioactive isotopes C14 of by using radioactive isotopes C14 of carboncarbon

• Radioactivity measured with scintillation Radioactivity measured with scintillation countercounter

Can use satellite imaging: Nutrient rich waters of the North Atlantic

Measuring Secondary Productivity

• Gross Secondary ProductionGross Secondary Production• Measure the mass of food intake (Measure the mass of food intake (II) by an organism (best if ) by an organism (best if

controlled diet in lab)controlled diet in lab)• Measure mass of waste Measure mass of waste (W)(W) (excrement, shedding, etc.) (excrement, shedding, etc.)

producedproduced• GSP = I – WGSP = I – W

• Net Secondary ProductionNet Secondary Production• Measure organism’s starting mass (Measure organism’s starting mass (SS) and ending mass () and ending mass (EE) )

for experiment durationfor experiment duration• NSP = E-SNSP = E-S

Method evaluation

• GSP method difficult in natural conditionsGSP method difficult in natural conditions

• Even in lab hard to get exact masses for Even in lab hard to get exact masses for wastewaste

• NSP method hard to document mass NSP method hard to document mass change in organism unless it is over a change in organism unless it is over a long time periodlong time period

What types of things effect productivity?

• What can we measure for an experiment?What can we measure for an experiment?• Effects of light exposure – strength, time, color, Effects of light exposure – strength, time, color,

……• Effects of temperatureEffects of temperature• Differences between types of plantsDifferences between types of plants• Differences between types of producersDifferences between types of producers• Effects of nutrient additionsEffects of nutrient additions• Effects of salinityEffects of salinity

Other parameters to change

• Terrestrial vs. aquaticTerrestrial vs. aquatic

• Oxygen, carbon dioxideOxygen, carbon dioxide

• BiomassBiomass

• B.O.D. bottlesB.O.D. bottles

GPP estimates

Problems

Dissolved Oxygen (mmol/L) in water samples from Lake Ashby

Transparent Bottle Opaque Bottle

Initial, 6 a.m. 0.288 0.288

Final, 9 a.m. 0.292 0.282

Difference +0.004 -0.006

1. Write the equation for and calculate the GPP2. Write the equation for and calculate the NPP3. Write the equation for and calculate the Respiration

Problems

1.1. The GPP of the producers in the area, The GPP of the producers in the area, large rainforest trees, is 0.0050 large rainforest trees, is 0.0050 g/cmg/cm22/day and 25% of this productivity /day and 25% of this productivity is consumed in respiration. Calculate is consumed in respiration. Calculate the NPP.the NPP.