ProductivityProductivity

What do “producers” produce?What do “producers” produce?– Energy-rich organic compounds from inorganic Energy-rich organic compounds from inorganic

materials through photo- and chemosynthesismaterials through photo- and chemosynthesis These energy rich compounds can be used These energy rich compounds can be used

in producing more of themselves either in producing more of themselves either through through growthgrowth or or reproductionreproduction

ProductionProduction = the incorporation of energy = the incorporation of energy and materials into the bodies of organismsand materials into the bodies of organisms

BiomassBiomass ““mass of mass of organicorganic material in organisms or material in organisms or

ecosystems” (IB definition)ecosystems” (IB definition) Measured after removal of water since Measured after removal of water since

water is not organic, contains no useable water is not organic, contains no useable energy and varies over time in organismsenergy and varies over time in organisms

Inorganic material is usually insignificant in Inorganic material is usually insignificant in terms of massterms of mass

Usually expressed per unit areaUsually expressed per unit area Standing cropStanding crop = ecosystem biomass = ecosystem biomass

Primary producersPrimary producers

Often just called producers although using Often just called producers although using the definition of ‘the definition of ‘productionproduction’ all organisms ’ all organisms are producersare producers

Support all other organisms in a food webSupport all other organisms in a food web

Fix carbon through photosynthesis or Fix carbon through photosynthesis or chemosynthesis to produce BIOMASSchemosynthesis to produce BIOMASS

Primary productivityPrimary productivity ““the quantity of organic material produced, the quantity of organic material produced,

or solar energy fixed, by photosynthesis in or solar energy fixed, by photosynthesis in green plants per unit time” (IB definition)green plants per unit time” (IB definition)

Incomplete definitionIncomplete definition– ChemosynthesisChemosynthesis– Non-green plant autotrophsNon-green plant autotrophs

Rate at which autotrophs synthesize new Rate at which autotrophs synthesize new biomassbiomass

Gross Primary Productivity Gross Primary Productivity (GPP)(GPP)

Total amount of organic material fixed by Total amount of organic material fixed by autotrophsautotrophs

Result of photosynthesis (or chemosynthesis)Result of photosynthesis (or chemosynthesis) COCO22 + H + H220 + light energy 0 + light energy glucose + O glucose + O22

Net Primary ProductivityNet Primary Productivity(NPP)(NPP)

Rate of production of biomass potentially Rate of production of biomass potentially available to consumers (herbivores)available to consumers (herbivores)

Not all of the total productivity (energy) Not all of the total productivity (energy) goes into making biomass (growth and goes into making biomass (growth and reproduction)reproduction)

Some productivity is used in the Some productivity is used in the autotroph’s own life processes (respiration) autotroph’s own life processes (respiration) and this energy is ultimately lost as heatand this energy is ultimately lost as heat

Succession…As a community goes through succession, GPP & NPP change. Early stages have low GPP but high NPP (attracts others!)

Then, the GPP increases steadily, until climax is reached– then GPP =NPP

Plagioclimax is when humans intentionally interrupts succession before climax. (agriculture)

Primary ConsumersPrimary ConsumersNPP = GPP - respirationNPP = GPP - respiration

GPP less the biomass or energy used by GPP less the biomass or energy used by autotrophs in respirationautotrophs in respiration

Respiration:Respiration:– Glucose + OGlucose + O22 CO CO22 + H + H22O +ATP (energy)O +ATP (energy)

When energy is released from ATP it is lost When energy is released from ATP it is lost as heat (chemical as heat (chemical heat) heat)

Productivity is expressed as:Productivity is expressed as:

Energy per unit area per unit timeEnergy per unit area per unit timee.g. J/me.g. J/m22/yr/yr

OROR

Biomass added per unit area per unit timeBiomass added per unit area per unit timee.g. g/me.g. g/m22/yr/yr

Measuring primary productivityMeasuring primary productivity1.1. Harvest methodHarvest method - measure biomass change - measure biomass change

over time and express as biomass per unit over time and express as biomass per unit area per unit timearea per unit time

• Destructive!Destructive!

2.2. COCO22 assimilation assimilation - measure CO - measure CO22 uptake in uptake in

photosynthesis and release by respirationphotosynthesis and release by respiration• Assume any COAssume any CO22 removed is incorporated into removed is incorporated into

organic material by photosynthesisorganic material by photosynthesis• Use dark bottle to measure respiration in Use dark bottle to measure respiration in

absence of photosynthesis to get GPPabsence of photosynthesis to get GPP

• COCO2 2 is difficult to measure in aquatic systemsis difficult to measure in aquatic systems

3.3. Oxygen productionOxygen production - Measure O - Measure O22 production and consumptionproduction and consumption

• light and dark bottle experimentslight and dark bottle experiments• Light bottle: photosynthesis and respiration Light bottle: photosynthesis and respiration • Dark bottle: respiration onlyDark bottle: respiration only• Measure OMeasure O22 production in both to determine production in both to determine

GPP (photosynthesis) and NPP (GPP-R)GPP (photosynthesis) and NPP (GPP-R)

4.4. Radioisotope methodRadioisotope method - use - use 1414C tracer in C tracer in photosynthesisphotosynthesis

• Incubate producers with a known quantity of Incubate producers with a known quantity of 1414C C (often as bicarbonate)(often as bicarbonate)

• Measure amount of radioactive glucose Measure amount of radioactive glucose producedproduced

5.5. Chlorophyll measurementChlorophyll measurement - assumes a - assumes a correlation between amount of chlorophyll correlation between amount of chlorophyll and rate of photosynthesisand rate of photosynthesis

• Satellite imagery to show global productivitySatellite imagery to show global productivity• http://oceancolor.gsfc.nasa.gov/cgi/level3_rolling.pl

• http://earthobservatory.nasa.gov/Newsroom/NPP/Images/npp_20012002_sm.mpg

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

What are the factors that affect What are the factors that affect primary productivity?primary productivity?

1.1. Solar radiationSolar radiation: : quality (type) of lightquality (type) of light• quantity of light quantity of light productivity (to a point productivity (to a point

when too much light will inhibit when too much light will inhibit photosynthesis)photosynthesis)

2.2. TemperatureTemperature: : temp. temp. productivity productivity (to a point when high temperatures can (to a point when high temperatures can denature enzymes)denature enzymes)

3.3. COCO22: : CO CO22 productivity productivity (since CO(since CO22 is an input) is an input)

4.4. HH22OO:: H H22O O productivity (again productivity (again since Hsince H22O is an input)O is an input)

More factors…More factors…

5.5. NutrientsNutrients: : nutrients nutrients productivity productivity (any food, chemical element or compound (any food, chemical element or compound required by an organism to live, grow and required by an organism to live, grow and reproduce, e.g. iron, magnesium, calcium, reproduce, e.g. iron, magnesium, calcium, nitrate, phosphate, silicate)nitrate, phosphate, silicate)

6.6. HerbivoryHerbivory: grazing of autotrophs by : grazing of autotrophs by herbivores can herbivores can productivity (e.g. sea productivity (e.g. sea urchins urchins ing productivity of kelp forest ing productivity of kelp forest habitat)habitat)

Therefore…Therefore… The The leastleast productive ecosystems are those productive ecosystems are those

with limited heat and light energy, limited with limited heat and light energy, limited water and limited nutrientswater and limited nutrients

The The mostmost productive ecosystems are those productive ecosystems are those with high temperatures, lots of water, light with high temperatures, lots of water, light and nutrientsand nutrients

And with increasing atmospheric COAnd with increasing atmospheric CO22 there there

is increasing global productivityis increasing global productivity

(Discussion only)Which biomes (Discussion only)Which biomes are most productive?are most productive?

What’s a biome?What’s a biome? BiomeBiome: collection of ecosystems with : collection of ecosystems with

similar climatic conditions (IB)similar climatic conditions (IB) e.g. tundra, open ocean, tropical rainforeste.g. tundra, open ocean, tropical rainforest Biomes do differ in their productivity as Biomes do differ in their productivity as

well as their contribution to global well as their contribution to global productivityproductivity

Figure 54.3 CampbellFigure 54.3 Campbell

Biome productivityBiome productivity Productivity is greatest at Productivity is greatest at low latitudeslow latitudes

where temperatures are high throughout the where temperatures are high throughout the year, light input is high and precipitation is year, light input is high and precipitation is also highalso high

Moving towards the poles, both temperature Moving towards the poles, both temperature and light decrease so productivity decreasesand light decrease so productivity decreases

ArcticArctic and and AntarcticAntarctic regions have low regions have low temperatures, permanently frozen ground, temperatures, permanently frozen ground, periods of perpetual darkness and low periods of perpetual darkness and low precipitation precipitation low productivity low productivity

More biome productivityMore biome productivity DesertsDeserts - low precipitation results in low - low precipitation results in low

productivity even though temperatures are productivity even though temperatures are high and light is abundanthigh and light is abundant

Coastal ocean zonesCoastal ocean zones are particularly are particularly productive due to upwelling of nutrients productive due to upwelling of nutrients from deep sea and input of nutrients from from deep sea and input of nutrients from landland

Despite high temperatures and abundant Despite high temperatures and abundant light light tropical oceanstropical oceans are not very are not very productive due to low nutrientsproductive due to low nutrients

TheThe open ocean open ocean is also nutrient limited is also nutrient limited

Satellite images of productivitySatellite images of productivity

http://www.nasa.gov/centers/goddard/mpg/97462main_npp_20012002_sm.mpg

http://seawifs.gsfc.nasa.gov/cgi/level3_rolling.pl

Only 5-10% of light energy Only 5-10% of light energy available is fixed into biomassavailable is fixed into biomass

Much solar radiation is lost through Much solar radiation is lost through reflection and absorption by the atmospherereflection and absorption by the atmosphere

Still more solar radiation is reflected back Still more solar radiation is reflected back to space by oceans, deserts and ice capsto space by oceans, deserts and ice caps

Not all wavelengths of light are appropriate Not all wavelengths of light are appropriate for photosynthesisfor photosynthesis

There are further losses as energy There are further losses as energy is passed along food chainis passed along food chain

Some herbivores destroy plant matter Some herbivores destroy plant matter without eating it e.g. elephant trampling without eating it e.g. elephant trampling (messy eaters)(messy eaters)

Some materials are indigestibleSome materials are indigestible Use much of the energy to fuel their own Use much of the energy to fuel their own

metabolismmetabolism

Therefore only about 10% of what is Therefore only about 10% of what is obtained by eating is stored in consumers obtained by eating is stored in consumers biomass and available to next trophic levelbiomass and available to next trophic level

This decrease in energy is repeatedThis decrease in energy is repeated Same losses occur as herbivores are eaten Same losses occur as herbivores are eaten

by carnivores and again as those carnivores by carnivores and again as those carnivores are eaten by other carnivoresare eaten by other carnivores

** Limits the length of food chains**** Limits the length of food chains** Eventually almost all of the energy entering Eventually almost all of the energy entering

an ecosystem is lost as heat (unidirectional an ecosystem is lost as heat (unidirectional flow of energy) and is re-radiated to spaceflow of energy) and is re-radiated to space

The proportion of energy fixed in The proportion of energy fixed in photosynthesis that reaches the end of a photosynthesis that reaches the end of a food chain is very small due to large losses food chain is very small due to large losses at each stageat each stage

PyramidsPyramids

Graphical models of quantitative Graphical models of quantitative differences among trophic levels of an differences among trophic levels of an ecosystemecosystem

Can present data of numbers, biomass or Can present data of numbers, biomass or productivityproductivity

Secondary ProductivitySecondary Productivity

““biomass gained by heterotrophic biomass gained by heterotrophic organisms through feeding and absorption; organisms through feeding and absorption; measured in units of mass or energy per measured in units of mass or energy per unit area per unit time” (IB definition)unit area per unit time” (IB definition)

““rate at which an ecosystem’s consumers rate at which an ecosystem’s consumers convert the chemical energy of what they convert the chemical energy of what they eat into their own biomass”eat into their own biomass”

““rate of production of biomass by rate of production of biomass by heterotrophs”heterotrophs”

Also known as “Also known as “assimilationassimilation””

Gross Secondary ProductivityGross Secondary Productivity

Remember that consumers are inefficient Remember that consumers are inefficient and cannot digest all the organic and cannot digest all the organic compounds they eat (e.g. cellulose)compounds they eat (e.g. cellulose)

Therefore since not all the food eaten is Therefore since not all the food eaten is assimilated:assimilated:

GSP = Food eaten - fecal lossesGSP = Food eaten - fecal losses

Net Secondary ProductivityNet Secondary Productivity

In addition some energy is used in In addition some energy is used in respiration…respiration…

NSP = GSP - respirationNSP = GSP - respiration

Or measure increase in biomass over timeOr measure increase in biomass over time