Fig. 2
From: Recycled iron fuels new production in the eastern equatorial Pacific Ocean
Observed and potential nitrate consumption. a Nitrate consumption estimates from 2003 to 2007 (colored bars) compared with potential nitrate consumption calculated for Scenarios 1–4 (open bars). Nitrate consumption estimates in a are from spring (pink), fall (blue), winter (purple), and error bars are ±1 μmol kg−1 based on source water variability (sampling date at bottom; values in Tables 1 and 2). White columns represent nitrate consumption predicted based on the following scenarios. "Observed" uses iron supply and diatom Fe:C requirements that match local observations12, 22. Scenario 1 uses local observations, but with a doubled dust-borne iron supply and an order of magnitude higher solubility of dust-borne iron. Scenario 2 assumes all particulate iron is bioavailable. Scenarios 3.1 and 3.2 use dissolved iron concentrations from 200 m and EUC measurements 3300 km west, respectively. Scenario 4 uses the lowest reported diatom Fe:C requirement of 2 μmol mol−1 7. Error bars (1 standard deviation) allow for potential C:N variability of ±2 (global community value71) even though phytoplankton community C:N ratio in the eastern equatorial Pacific is much smaller (±0.310). b A sensitivity analysis of potential nitrate consumption based on available iron concentrations and physiological iron requirements. White numbers in b indicate the Scenarios from a, none of which can explain the observed range in nitrate consumption of 6.1 and 12.7 μmol kg−1 (bold contours)
