Photosynthesis versus irradiance (P-E) parameters at day 4 of the incubation experiments are shown for incubations of Fe additions (dark bars) and unamended controls (white bars). Maximum photosynthesis rates (P^*_max) are shown for surface (S) and deeper subsurface (D) incubations from Stations 5, 13 and 35 (A) and for different levels of incident irradiance (1%, black; 10%, grey; 50%, light grey) for Stations 57 and 66 (B). Initial slope of the P-E curve (α^*) is shown for the surface and subsurface depths (C) and levels of incident irradiance (D), as is photoacclimation parameter (E_k) (E & F).