ENVIRONMENTAL SYSTEMS AND SOCIETIES Productivity analysis with exercises, for second year of Highscools

1. An owner of a shop takes $1,000,000 in sales
each day.
He pays out the following:
Wages: 50,000
Rent: 100,000
Utilities: 25,000
Stock: 100,000
Tax: 15,000
Misc: 10,000
How much money does he make per day?

2. Gross:
$100,000,000
Net:
$ 700,000

3. Productivity
 What do “producers” produce?
– 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

4. Productivity
 Recap photosynthesis and respiration.
 Define Productivity, Producer and Biomass.
 Define Gross and Net Primary Productivity.

5. Primary producers
 Often just called producers although using
the definition of ‘production’ all organisms
are producers
 Support all other organisms in a food web
 Fix carbon through photosynthesis or
chemosynthesis to produce BIOMASS

6. Biomass
 “mass of organic material in organisms or
ecosystems” (IB definition)
 Measured after removal of water since
water is not organic, contains no useable
energy and varies over time in organisms
 Inorganic material is usually insignificant in
terms of mass
 Usually expressed per unit area
 Standing crop = ecosystem biomass

7. Primary productivity
 “the quantity of organic material produced,
or solar energy fixed, by photosynthesis in
green plants per unit time” (IB definition)
 Incomplete definition
– Chemosynthesis
– Non-green plant autotrophs
 Rate at which autotrophs synthesize new
biomass

8. Gross Primary Productivity
(GPP)
 Total amount of organic material fixed by
autotrophs
 Result of photosynthesis (or chemosynthesis)
 CO2 + H20 + light energy  glucose + O2

9. 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

10. NPP = GPP - respiration
 GPP less the biomass or energy used by
autotrophs in respiration
 Respiration:
– Glucose + O2  CO2 + H2O +ATP (energy)
 When energy is released from ATP it is lost
as heat (chemical  heat)

11. Productivity is expressed as:
 Energy per unit area per unit time
e.g. J/m2/yr
OR
 Biomass added per unit area per unit time
e.g. g/m2/yr

12. Task
Complete the questions on page 43 of the
textbook.

13. Measuring primary productivity
1. Harvest method - measure biomass change
over time and express as biomass per unit
area per unit time
• Destructive!
2. 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

14. 3. Oxygen production - Measure O2
production and consumption
• light and dark bottle experiments
• Light bottle: photosynthesis and respiration
• Dark bottle: respiration only
• Measure O2 production in both to determine
GPP (photosynthesis) and NPP (GPP-R)
4. Radioisotope method - use 14C tracer in
photosynthesis
• Incubate producers with a known quantity of 14C
(often as bicarbonate)
• Measure amount of radioactive glucose
produced

15. 5. Chlorophyll measurement - assumes a
correlation between amount of chlorophyll
and rate of photosynthesis
• Satellite imagery to show global productivity
• http://oceancolor.gsfc.nasa.gov/cgi/level3_rolling.pl
• http://earthobservatory.nasa.gov/Newsroom/NPP/Images/npp_2
0012002_sm.mpg
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.

16. What are the factors that affect
primary productivity?
1. Solar radiation: quality (type) of light
• quantity of light  productivity (to a point
when too much light will inhibit
photosynthesis)
2. Temperature: temp.  productivity
(to a point when high temperatures can
denature enzymes)
3. CO2:  CO2  productivity
(since CO2 is an input)
4. H2O: H2O  productivity
(again since H2O is an input)

17. More factors…
5. Nutrients: nutrients  productivity
(any food, chemical element or
compound required by an organism to
live, grow and reproduce, e.g. iron,
magnesium, calcium, nitrate, phosphate,
silicate)
6. Herbivory: grazing of autotrophs by
herbivores can  productivity (e.g. sea
urchins ing productivity of kelp forest
habitat)

18. 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
 And with increasing atmospheric CO2 there
is increasing global productivity

19. Which biomes are most
productive?
 What’s a biome?
 Biome: collection of ecosystems with
similar climatic conditions (IB)
 e.g. tundra, open ocean, tropical rainforest
 Biomes do differ in their productivity as
well as their contribution to global
productivity
 Figure 54.3 Campbell

20. Biome productivity
 Productivity is greatest at low latitudes
where temperatures are high throughout the
year, light input is high and precipitation is
also high
 Moving towards the poles, both temperature
and light decrease so productivity decreases
 Arctic and Antarctic regions have low
temperatures, permanently frozen ground,
periods of perpetual darkness and low
precipitation  low productivity

21. More biome productivity
 Deserts - low precipitation results in low
productivity even though temperatures are
high and light is abundant
 Coastal ocean zones are particularly
productive due to upwelling of nutrients
from deep sea and input of nutrients from
land
 Despite high temperatures and abundant
light tropical oceans are not very
productive due to low nutrients
 The open ocean is also nutrient limited

22. Satellite images of productivity
 http://www.nasa.gov/centers/goddard/mp
g/97462main_npp_20012002_sm.mpg
 http://seawifs.gsfc.nasa.gov/cgi/level3_ro
lling.pl

23. Only 5-10% of light energy
available is fixed into biomass
 Much solar radiation is lost through
reflection and absorption by the atmosphere
 Still more solar radiation is reflected back to
space by oceans, deserts and ice caps
 Not all wavelengths of light are appropriate
for photosynthesis

24. There are further losses as energy
is passed along food chain
 Some herbivores destroy plant matter
without eating it e.g. elephant trampling
(messy eaters)
 Some materials are indigestible
 Use much of the energy to fuel their own
metabolism
 Therefore only about 10% of what is
obtained by eating is stored in consumers
biomass and available to next trophic level

25. This decrease in energy is repeated
 Same losses occur as herbivores are eaten
by carnivores and again as those carnivores
are eaten by other carnivores
 ** Limits the length of food chains**
 Eventually almost all of the energy entering
an ecosystem is lost as heat (unidirectional
flow of energy) and is re-radiated to space
 The proportion of energy fixed in
photosynthesis that reaches the end of a
food chain is very small due to large losses
at each stage

26. Pyramids
 Graphical models of quantitative
differences among trophic levels of an
ecosystem
 Can present data of numbers, biomass or
productivity

28. Primary productivity
 “the quantity of organic material produced,
or solar energy fixed, by photosynthesis in
green plants per unit time” (IB definition)
 Incomplete definition
– Chemosynthesis
– Non-green plant autotrophs
 Rate at which autotrophs synthesize new
biomass

29. Gross Primary Productivity
(GPP)
 Total amount of organic material fixed by
autotrophs
 Result of photosynthesis (or chemosynthesis)
 CO2 + H20 + light energy  glucose + O2

30. 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

31. NPP = GPP - respiration
 GPP less the biomass or energy used by
autotrophs in respiration
 Respiration:
– Glucose + O2  CO2 + H2O +ATP (energy)
 When energy is released from ATP it is lost
as heat (chemical  heat)

32. Secondary Productivity
 “biomass gained by heterotrophic
organisms through feeding and absorption;
measured in units of mass or energy per unit
area per unit time” (IB definition)
 “rate at which an ecosystem’s consumers
convert the chemical energy of what they
eat into their own biomass”
 “rate of production of biomass by
heterotrophs”
 Also known as “assimilation”

33. Gross Secondary Productivity
 Remember that consumers are inefficient
and cannot digest all the organic
compounds they eat (e.g. cellulose)
 Therefore since not all the food eaten is
assimilated:
 GSP = Food eaten - fecal losses

34. Net Secondary Productivity
 In addition some energy is used in
respiration…
 NSP = GSP - respiration
 Or measure increase in biomass over time