1. Primary Productivity: Dissolved Oxygen “DO”
AP Biology Lab 12

2. What you need to know!
Dissolved oxygen availability under varying conditions
Ideal conditions for maximum dissolved oxygen
How to measure primary productivity by analyzing varying dissolved oxygen levels

3. Primary Productivity Rate organic at which organic mats are stored
Mats: Carbon based organic compounds
Only done by photosynthesis (PS) and chemosynthesis
H2O + CO2  O2 + sugar
We can measure: loss of CO2 OR gain of O2
1 mL O2 produced = .536 mg C transformed into organic compounds

4. Oxygen in Aquatic Environments
O2 must be dissolved to be available to aquatic organisms
O2 in the air 20%
O2 in the water 5-10% (depending on the type of water)

5. DO levels change in various:
Temperature
Salinity pH
Pollution
Also creates an imbalance within the food chain
Example: algae bloom

6. DO is highest in: Low temperature Low salinity (fresh water)
Low elevation
No pollution
Highest DOs are in clean freshwater lakes at low altitudes

7. Freshwater DO Nomogram

8. DO, PS, and CR
The productivity of living processes such as photosynthesis (PS) and cellular respiration (CR) impact DO concentrations
CR uses O2
PS makes O2

9. Productivity Test
Use live water samples (ponds/rivers/ocean) containing algae, and other PS and aerobic bacteria
Incubate samples in varying levels of light intensity from 100% to 0%
Measure O2 using various measuring devices: spectrometer, colorimetric scale, etc.

10. Results: Respiration 0% light intensity yields:
No O2 produced by photosynthesis
O2 consumed by cellular respiration
Net loss of O2

11. Results: Net 100% light intensity yields:
O2 produced by photosynthesis
O2 consumed by cellular respiration
Net gain of O2 because PS is faster than CR

12. Results: Gross
To calculate the Primary Productivity (total amount of O2 produced) you take the amount of net O2 gained and add the amount of O2 lost during respiration

13. Virtual Lab