Ecosystems
Primary Productivity
Roles of Species in Ecosystems
Primary Productivity
• The fabrication of carbon
•
•
compounds through
photosynthesis or
chemosynthesis by bacteria,
protists, and plants.
Such organisms contribute the
sugars, lipids, and other building
blocks for all other consumers in
the trophic levels.
Primary productivity determines
the amount of energy available
in an ecosystem.
Productivity of Producers:
The Rate Is Crucial
• Gross primary
production (GPP)
– Rate at which an
ecosystem’s
producers
convert solar
energy into
chemical energy
as biomass.
Figure 3-20
Primary Productivity
• Gross Primary Productivity
•
(GPP)
• Rate at which producers
can convert solar energy
into biomass.
Net Primary Productivity
(NPP)
• Rate at which producers
make and store
photosynthetic products,
but also takes into
account the needs of the
organism to use the
products for their own
energy requirements
Primary Productivity
• The general formula for
calculating the available biomass
in the form of high energy
organic compounds is:
GPP – respiration rate = NPP
• These values are often given in
•
mg/L/day or may be expressed
in energy units, such as kCal or
kJ per day
Average net primary productivity
is kcal/m2/yr is sometimes
referred to as natural capital.
Primary
Productivity
• Various ecosystems and
biomes show different
rates of GPP and NPP
• Terrestrial
• Tropical rain forest,
swamps, marshes
• Aquatic
• Salt marshes
(nutrients)
Primary Productivity
• Ocean productivity is the greatest overall
• Marine phytoplankton are efficient at
various depths because of their different
light-absorbing pigments and the vast
number of these producers worldwide
What are nature’s three most productive and
three least productive systems?
Primary Productivity
Trophic
Level
Energy
Waste
Consumed Energy
Producer
GPP
NPP
1,500,000
10,000
8,000
1o
Consumer
2000
1600
200
80
2o
Consumer
160
100
40
10
In the community described in the table
above, which of the following represents
the respiratory energy (kcal/m2/year) used
by autotrophic organisms?
a) 10
b) 200
c) 1,600
d) 2,000
e) 10,000
Primary Productivity
Energy flow for Green Springs (kcal/m2/yr).
Trophic level
Producers
Primary Consumers
(herbivores)
Secondary Consumers
(carnivores)
Tertiary Consumers
(top carnivores)
Energy Available
(kcal/m2/yr)
9000
1500
120
12
Based on the table above, calculate the efficiency of energy
transfer (in percent) from:
a) Producers to primary consumers
b) Primary consumers to secondary consumers
c) Secondary consumers to tertiary consumers