371
Primary Production in the Oceans
1. There is insufficient sensitivity (~3 mg C m –2 h –1 ) in low- productivity oligotrophic waters.
2. It cannot be used in polluted waters because the oxidation of organic pollutants
can result in the loss of O 2 .
3. Results will be low when lipids or proteins are photosynthesized products
(e.g., diatoms).
4. Bacteria adsorbed to the bottle wall can cause problems.
5. The growth may be affected by confinement in the bottles.
Bender and coworkers (1987) have developed a method to measure gross primary production using the stable isotope 18 O. The sample is artificially enriched with 18 O in H 2 O,
and the 18 O in O 2 is produced by the reaction
H 2
18 O + CO 2 → CH 2 O + 18 O 16 O
(9.10)
The rate of O 2 production is measured using a mass spectrophotometer. The fractionation
of oxygen isotopes during photosynthesis does not affect the measurement significantly.
The δ(O 18 / 16 O) = [(O 18 / 16 O sample / O 18 / 16 O standard ) – 1]10 3 is raised by 2000 to 3000. The changes
caused by respiration affect the rate to a much smaller degree than the 14 C method. This
method measures the gross production; the 14 C method measures the difference between
Table 9.2
Methods Used to Determine Primary Productivity
In Vitro
Component
Timescale
14 C assimilation
P T = P N
Hours to 1 day
O 2 evolution
P T
Hours to 1 day
15 NO 3 assimilation
P NEW
Hours to 1 day a
15 NH 4
P T
Hours to 1 day a
18 O 2 evolution
P NEW = P C
Hours to 1 day b
Physical transport
Sediment traps
P NEW = P C
Days to months
Bulk properties
NO 3 flux to photic zone
P NEW
Hours to days
O 2 utilization
P NEW
Seasonal to annual
Net O 2 accumulation
P NEW
Seasonal to annual
238 U/ 234Th
P NEW
Days to year c
3 H/ 3 He
P NEW
Seasonal to annual d
Upper and lower limits
Photons absorbed
P T
Instantaneous to annual
Depletion of winter NO 3
P NEW
Seasonal
Remote sensing
P T , P NEW
Days to annual
Note: P T , total primary production (P NEW + P R ); P NEW , new production; P N , net primary production; P R , regenerative production;
P C , community production.
a Altabet, M., and Deuser, W., Nature, 315 (1985).
b Bender, M., et al., Limnol. Oceangr., 32, 1085 (1987).
c Coale, K., and Bruland, K., Limnol. Oceangr., 32, 189 (1987).
d Jenkins, W., Nature, 300, 246 (1982).
Primary Production in the Oceans
1. There is insufficient sensitivity (~3 mg C m –2 h –1 ) in low- productivity oligotrophic waters.
2. It cannot be used in polluted waters because the oxidation of organic pollutants
can result in the loss of O 2 .
3. Results will be low when lipids or proteins are photosynthesized products
(e.g., diatoms).
4. Bacteria adsorbed to the bottle wall can cause problems.
5. The growth may be affected by confinement in the bottles.
Bender and coworkers (1987) have developed a method to measure gross primary production using the stable isotope 18 O. The sample is artificially enriched with 18 O in H 2 O,
and the 18 O in O 2 is produced by the reaction
H 2
18 O + CO 2 → CH 2 O + 18 O 16 O
(9.10)
The rate of O 2 production is measured using a mass spectrophotometer. The fractionation
of oxygen isotopes during photosynthesis does not affect the measurement significantly.
The δ(O 18 / 16 O) = [(O 18 / 16 O sample / O 18 / 16 O standard ) – 1]10 3 is raised by 2000 to 3000. The changes
caused by respiration affect the rate to a much smaller degree than the 14 C method. This
method measures the gross production; the 14 C method measures the difference between
Table 9.2
Methods Used to Determine Primary Productivity
In Vitro
Component
Timescale
14 C assimilation
P T = P N
Hours to 1 day
O 2 evolution
P T
Hours to 1 day
15 NO 3 assimilation
P NEW
Hours to 1 day a
15 NH 4
P T
Hours to 1 day a
18 O 2 evolution
P NEW = P C
Hours to 1 day b
Physical transport
Sediment traps
P NEW = P C
Days to months
Bulk properties
NO 3 flux to photic zone
P NEW
Hours to days
O 2 utilization
P NEW
Seasonal to annual
Net O 2 accumulation
P NEW
Seasonal to annual
238 U/ 234Th
P NEW
Days to year c
3 H/ 3 He
P NEW
Seasonal to annual d
Upper and lower limits
Photons absorbed
P T
Instantaneous to annual
Depletion of winter NO 3
P NEW
Seasonal
Remote sensing
P T , P NEW
Days to annual
Note: P T , total primary production (P NEW + P R ); P NEW , new production; P N , net primary production; P R , regenerative production;
P C , community production.
a Altabet, M., and Deuser, W., Nature, 315 (1985).
b Bender, M., et al., Limnol. Oceangr., 32, 1085 (1987).
c Coale, K., and Bruland, K., Limnol. Oceangr., 32, 189 (1987).
d Jenkins, W., Nature, 300, 246 (1982).