Physiological differences between treatments.

Final Chl a∶ POC ratios (µg∶µg) and photophysiological parameters (apparent maximum quantum yield of PSII Fv/Fm, proportion of non-photochemical quenching, NPQ, functional absorption cross section of PSII (σPSII [Å2 quanta−1]), and relative electron transport rates from PSII, rETR) of the final communities grown under different CO2 and Fe levels (n = 3; mean ±1 s.d.). Fe-depleted (−Fe) and Fe-enriched (+Fe) conditions were achieved by the addition of 10 nmol kg−1 DFB and 1 nmol kg−1 FeCl3, respectively. Bold p values indicate statistically significant differences between treatments (p<0.05; 2-way ANOVA).