The photosynthetic model marine diatom Phaeodactylum tricornutum was cultured under conditions varying nitrogen content and availability, or varying iron concentrations over diel cycles to elicit shifts in the proteome and phosphoproteome. For the nitrogen experiments, cells were grown to mid-exponential phase on ammonium (880 uM), collected by centrifugation and resuspended in N-free media for 2 hrs, and spiked with nitrate (150 uM) for 90 min. Cells were again collected by centrifugation, washed in N-free media, and resuspended in experimental treatments with no nitrogen (N-) and a nitrogen source (300 uM) provided as ammonium, nitrite, or nitrate. Each experimental treatment was sampled after 15 min, 45 min, and 18 hr. For iron experiments, steady-state axenic cultures were maintained under a diel cycle of 12h light: 12h darkness and at three different concentrations of Fe' (Fe' is the sum of all Fe species not complexed to EDTA): a low concentration (20 pM Fe'), intermediate concentration (40 pM Fe') and at Fe-replete levels (400 pM Fe'). Samples were taken every four hours.