EcosystemsEcosystems

Primary ProductivityPrimary Productivity

Roles of Species in EcosystemsRoles of Species in Ecosystems

Primary ProductivityPrimary Productivity• The fabrication of carbon The fabrication of carbon

compounds through compounds through photosynthesis or photosynthesis or chemosynthesis by bacteria, chemosynthesis by bacteria, protists, and plants.protists, and plants.

• Such organisms contribute the Such organisms contribute the sugars, lipids, and other building sugars, lipids, and other building blocks for all other consumers in blocks for all other consumers in the trophic levels.the trophic levels.

• Primary productivity determines Primary productivity determines the amount of energy available the amount of energy available in an ecosystem.in an ecosystem.

Productivity of Producers: Productivity of Producers: The Rate Is CrucialThe Rate Is Crucial

• Gross primary Gross primary production (GPP) production (GPP) – Rate at which an Rate at which an

ecosystemecosystem’’s s producers producers convert solar convert solar energy into energy into chemical energy chemical energy as biomass.as biomass.

Figure 3-20Figure 3-20

Primary ProductivityPrimary Productivity• Gross Primary Productivity Gross Primary Productivity

(GPP)(GPP)• Rate at which producers Rate at which producers

can convert solar energy can convert solar energy into biomass.into biomass.

• Net Primary Productivity Net Primary Productivity (NPP)(NPP)• Rate at which producers Rate at which producers

make and store make and store photosynthetic products, photosynthetic products, but also takes into but also takes into account the needs of the account the needs of the organism to use the organism to use the products for their own products for their own energy requirementsenergy requirements

Primary ProductivityPrimary Productivity• The general formula for The general formula for

calculating the available biomass calculating the available biomass in the form of high energy in the form of high energy organic compounds is:organic compounds is:

GPP – respiration rate = NPPGPP – respiration rate = NPP

• These values are often given in These values are often given in mg/L/day or may be expressed mg/L/day or may be expressed in energy units, such as kCal or in energy units, such as kCal or kJ per daykJ per day

• Average net primary Average net primary productivity is kcal/mproductivity is kcal/m22/yr is /yr is sometimes referred to as sometimes referred to as natural capital.natural capital.

Primary Primary ProductivityProductivity

• Various ecosystems and Various ecosystems and biomes show different biomes show different rates of GPP and NPPrates of GPP and NPP

• TerrestrialTerrestrial• Tropical rain forest, Tropical rain forest,

swamps, marshesswamps, marshes• AquaticAquatic

• Salt marshes Salt marshes (nutrients)(nutrients)

Primary ProductivityPrimary Productivity• Ocean productivity is the greatest overallOcean productivity is the greatest overall

• Marine phytoplankton are efficient at Marine phytoplankton are efficient at various depths because of their different various depths because of their different light-absorbing pigments and the vast light-absorbing pigments and the vast number of these producers worldwidenumber of these producers worldwide

What are nature’s three most productive and What are nature’s three most productive and three least productive systems?three least productive systems?

Trophic Level

Energy Consumed

Waste Energy

GPP NPP

Producer 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) 200c) 1,600 d) 2,000e) 10,000

Primary ProductivityPrimary Productivity

Primary ProductivityPrimary Productivity

Trophic levelEnergy Available (kcal/m2/yr)

Producers 9000Primary Consumers (herbivores) 1500Secondary Consumers (carnivores) 120Tertiary Consumers (top carnivores) 12

Energy flow for Green Springs (kcal/m2/yr).

Based on the table above, calculate the efficiency of energy transfer (in percent) from:

a) Producers to primary consumersb) Primary consumers to secondary consumersc) Secondary consumers to tertiary consumers