Primary%20Productivity

1
Primary Productivity

• Importance
• Gross and Net productivity
• How could it be measured

2
Photosynthesis the source of food

• Photosynthesis (building up by light) is a
  complex biochemical process carried out by
  aquatic and terrestrial chlorophyll-bearing
  plants.
• The equation for photosynthesis is written as
  follows
•         light energy 6CO2
  6H2O   C6H12O6 6O2        
  chlorophyll

3
Photosynthesis and Primary productivity

• Photosynthesis provides the basis for life for
  most organisms on the Earth
• Photosynthetic organisms take CO2 and H2O and
  convert it into carbohydrates (for their own use)
  and O2 (exported into the environment, becoming a
  part of the oxygen cycle).
• Animals then use the oxygen and carbohydrates
  produced by the photosynthetic organisms as their
  source of energy.  

4
DETERMINING PRIMARY PRODUCTIVITYTHE LIGHT
BOTTLE-DARK BOTTLE METHOD

• The light bottle-dark bottle method can be used
  to estimate the rate of photosynthesis, the
  amount of carbon synthesized, and the amount of
  caloric energy stored in the carbon compounds
  that are formed.

5
What does this method measure?

• This method compares the oxygen changes that
  occur in plankton communities contained in light
  bottles with those occurring in dark bottles
  during a specified period of time.

6
How does the method work?

• Respiration rate Photosynthesis
• 
  and
• Respiration
• Dark bottle Light
  bottle

7
What happens in the light bottle

• In the light bottle, oxygen is being produced
  during photosynthesis by the phytoplankton in the
  water and oxygen is being consumed by plant and
  animal respiration.

8
What happens in the dark bottle

• In the dark bottle, only respiration is occurring
  because there is no light present for
  photosynthesis to occur.

9
Then, how do you estimate primary productivity?

• Gross primary productivity total amount of
  matter synthesized by producers in a given amount
  of time
• Net primary productivity amount of matter
  synthesized in a given amount of time minus
  respiratory losses in the same amount of time

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Formulas ???

• Respiration rate Initial DO Dark bottle
  DO
• (community respiration CR)
• Net primary productivity Light bottle DO
  Initial
• (NP)
  DO
• Gross primary productivity CR - NP
• (GP)

11
But, what are the limitations of this method as
a tool to measure Primary Productivity?
12
Answer

• Container where the water sample is collected
  (plastic, glass)
• Is the rate of respiration the same in each of
  the two bottles??? not true, it depends
• Is the rate of production in a close container
  equal to that in the natural environment???
• Do you find the same amount of plankton in both
  bottles???