Fig. 2: Phytoplankton physiological responses to the Pacific nutrient limitation transition.
From: Persistent equatorial Pacific iron limitation under ENSO forcing
a,b, Fv/Fm (a) and σPSII (b). Light blue shading around the line in a indicates the sensitivity of Fv/Fm to the applied blank (mean ± standard deviation; n = 16 observations of separate filtrates). Yellow lines and shading indicate sunlight (relative). Daytime Fv/Fm decreases result from the well-known process of non-photochemical quenching14,15. Circled numbers represent major sampling sites. c, Schematic of the photosynthetic membrane with Fe requirements, highlighting changes in component pool sizes and pigment proteins under the two nutrient limitation regimes (Isi-PPC, Fe-stress-induced pigment protein complex; PQ, plastoquinone)30,31,32. Cyt, cytochrome; Fl, flavodoxin; Pcy, plastocyanin. Red arrows indicate relative fluorescence yields of the different components. d, Measured abundances of proteins associated with PSII and PSI. nESC, normalized exclusive spectral counts (for which counts have been normalized to the maximum value at each of the five sites). e–g, Controls on night-time Fv/Fm reductions. Data are from a diel cycle highlighted in a and b.
