Dissolved Oxygen

1
Dissolved Oxygen
0

• Lab 12

2
12a
0

• 12a Measure dissolved oxygen content as a
  function of temperature.
• Use water at 0-5, 20, 30 degrees
• Using the nomogram to measure saturation. (p
  139 in lab manual)

3
12b How does the amount of light affect
productivity?
0

• Model depth in a lake with screens
• 100- 0 screens
• 65 - 1 screen
• 25 - 3 screens
• 10 - 5 screens
• 2 - 8 screens

4
12b. Primary Productivity The rate at which
organic materials are stored6CO2 6H2O ?
C6H12O6 6O2
0

• Can determine by measuring oxygen.
• 1 ml of O2 .536 mg of C assimilated
• To convert ppm O2 mg O2/L
• mg O2/L x 0.698 ml O2/L
• ml O2/L x 0.536 mg carbon fixed/L

5
12 B
0

• Fill 7 water sampling bottles
• I Initial
• D Dark
• 100, 65, 25, 10, 2 with screens
• 0 1 3 5 8

6
Initial
0

• The DO value when you begin your test.

DO 6
7
Dark
0

• Respiration Only
• How much O2 you started with how much is used
  up (say in 24 hours).
• Initial -Dark

How much do you think we have left?
DO 4
6-42 mg O2 /L
8
Net Primary Productivity
0

• Orgs make O2
• Orgs use O2
• How much is left over?
• Light- Initial

I made 7 mg O2/L today!!!
9 - 6 3 mg O2/L
Yeah, well I used up 4!
DO 9
9
Gross Primary Productivity
0

• Total O2 made
• Net and the respiration
• (Light initial) (Initial dark)
• This is
• Net Resp
• (9-6) (6-4)
• 3 2 5 mg O2/ L
• OrLight-Dark
• 9-45

10
0
DO
Time

• L-I Net Productivity (In the light bottles,
  photosynthesis and respiration are occurring. How
  much change from the starting point-initial? )
• I-D Respiration (The difference between the O2
  in the bottle you started with-Initial- and the
  bottle in the dark.)
• L-D Gross Productivity ( The difference between
  the light bottle and the dark bottle represents
  the total, or gross, productivity.)

11
0
light DO mg/L Gross Net Gross Carbon Fixed Net Carbon fixed
Initial 6.30 --- --- ml C/M3 ---
Dark 4.10 --- --- ---
100 7.95 L-D L-I
65 7.85
25 7.30
10 6.55
2 5.6
mg O2/L x 0.698 xml O2/L ml O2/L x 0.536 mg
C/L 1000 x mg C/L mg C/M3
12
0
light DO mg/L Gross Net Carbon fixed in mgC/m3
Initial 6.30 --- --- ---
Dark 4.10 --- --- ---
100 7.95 3.85 1.65 1440
65 7.85 3.75 1.55 1402
25 7.30 3.20 1.00 1197
10 6.55 2.45 0.25 938
2 5.6 1.50 -0.70 561