Lec 24 (Primary Production)

Question 1

• What is Primary Production?
• What is the biggest source of primary production?
• How else can primary production occur?

Answer 1

The fixation of energy by autotrophs in an
ecosystem.

Biggest source of primary production is
photosynthesis by plants, phytoplankton, and
cyanobacteria.

Also can occur via chemosynthesis by some
species of bacteria

Question 2

Primary productivity?

Answer 2

-amount of energy fixed by autotrophs over an interval of time (rate!)

-In the case of photosynthesis… Rate at which energy
from the sun used to make sugars by plants

Question 3

-What is this 6CO2 + 6H2O → C6H12O6

Answer 3

-Photosynthesis

Question 4

-What are the Two Measures of Primary Productivity?

Answer 4

Gross Primary Production
(GPP)

Net Primary Production
(NPP)

Question 5

-What is Gross Primary Production

(GPP) and an example?

Answer 5

The total amount of energy fixed
by all the autotrophs in the
ecosystem.

Example:
GPP = Photosynthesis

Question 6

-What is Net Primary Production

(NPP) and an example?

Answer 6

The total amount of energy fixed
by all the autotrophs in the
ecosystem, minus the cost
associated with its fixation.

Example:
NPP = Photosynthesis - Respiration

Question 7

Why do we need to know the difference between GPP and NPP??

Answer 7

NPP is the amount of energy available to consumers in

an ecosystem.

Question 8

How to measure ecosystem-level

primary production?

Answer 8

-Using Remote Sensing

Question 9

-What is remote sensing? How does it work? What does it use?

Answer 9

-Science of acquiring information about the Earth’s surface without being in contact with it

-Sensing and recording
reflected or emitted energy

-To do this, we use cameras and sensors attached to satellites

Question 10

Terrestrial Primary Production is affected by?

Answer 10

Mainly limited by temperature and moisture

Actual Evapotranspiration (AET)

Soil fertility

Question 11

-What is Actual Evapotranspiration (AET)?

Answer 11

The total amount of
water that evaporates
and transpires off a
landscape during a
given time period,
measured in mm water.

• Measure that accounts
for both temperature
and precipitation, as
AET is affected by both.

Question 12

-Talk about Terrestrial Primary Production and

Soil Fertility

Answer 12

• Adding fertilizers can increase primary production of some plants while also decrease primary production of others. This due to different plants occupying different niches thus they have different requirements.
• Soil Fertility is due to factors like nutrient availability of nitrogen, phosphorus, potassium

Question 13

Aquatic Primary Production is affected by?

Answer 13

Mainly limited by nutrient availability.

Freshwater Patterns/Marine Patterns

Question 14

Aquatic Primary Production Freshwater Patterns.

Answer 14

Higher phosphorus concentrations are associated with greater algal biomass

As algal biomass increases so does the rate of primary production

Question 15

Eutrophication?

Answer 15

nutrient enrichment of a water body

through natural processes or pollution, generally causing rapid algal growth and reduce dissolved oxygen levels

Question 16

Net primary production is the highest?

Answer 16

Along coastlines because of coastal upwelling

Question 17

Eutrophication aka nutrient enrichment can cause?

Answer 17

Hypoxia

Question 18

-What is Hypoxia?

Answer 18

Hypoxia: when water oxygen concentration is <2

mg O2 L -1

Question 19

Dead zones?

Answer 19

hypoxic areas in aquatic ecosystems, typically a consequence of pollution, eutrophication,
and high rates of decomposition, that are
essentially devoid of life