Table 2 Potential nitrate consumption was calculated for a range of iron concentrations and Fe:C physiological requirements

From: Recycled iron fuels new production in the eastern equatorial Pacific Ocean

 

Available iron (nmol kg−1)

Fe:C physiological requirements (μmol mol−1)

Potential nitrate consumption (μmol kg−1)

Note

Reference(s)

Observed

0.09

12.3

1.10

Observations from 0° N, 110° W

Twining et al.22; Kaupp et al.12

1

0.36

12.3

4.39

Double-dust flux and 10 times iron solubility

Winckler et al.57

2

0.31

12.3

3.80

All particulate iron is bioavailable

Gordon et al.30

3.1

0.35

12.3

4.30

Dissolved iron concentrations from 200 m at 110° W

Kaupp et al.12

3.2

0.54

12.3

6.63

Dissolved iron from 0° N, 140° W at 120 m

Kaupp et al.12

4

0.09

2.0

6.79

Very low Fe:C physiological requirements

King et al.33

  1. These nitrate consumption estimates were converted to Fe:N assuming Redfield C:N of 106:16 (see text for more details). “Observed” uses observed values at 0° N, 110° W12, 22. Scenario 1 doubles the dust-borne iron supply (equal to last glacial maximum values57) with an order of magnitude higher iron solubility (60%). Scenario 2 assumes all eastern equatorial Pacific euphotic zone particulate iron is bioavailable (observations from ref. 30) and Scenarios 3.1 and 3.2 assume higher dissolved iron concentrations. Scenario 4 uses the lowest reported Fe:C of 2 μmol:mol33. Note that the annual range in observed nitrate consumption is 6.1–12.7 μmol kg−1, but the highest calculated value is only 6.79.
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