Total dissolved iron (dFe) concentrations and carbonate chemistry determined at the end of the experiment in the culture medium (filtered seawater without cells) and the <i>P</i>. <i>subcurvata</i> incubations of the four treatments (<i>+Fe 190</i>, <i>Control 190</i>, <i>+Fe 290</i> and <i>Control 290</i>).

The pCO2 was calculated from measured dissolved inorganic carbon (DIC) and total alkalinity (TA). For the culture medium, dFe, TA, DIC and pCO2 values represent the range of duplicate abiotic controls. TA, DIC and pCO2 values of the P. subcurvata incubations represent the means ± SD (n = 3). Differences between the individual treatments of the P. subcurvata incubations were determined with post hoc tests, where significant statistical (p < 0.05) differences are denoted by different letters.