The document is investigating the possibility that antibodies to proteins repressed by a specific nutrient can be used as probes to indicate which nutrient limits photosynthetic carbon fixation in the ocean. The diatom Phaeodactylum tricornutum Bohlin and the chlorophyte Dunaliella tertiolecta Butcher were grown in batch cultures in artificial seawater and f/2 nutrient lacking either phosphorus, iron, or nitrogen. Chlorosis was inducted by nutrient limitation in both species with the exception of phsophorus-limited D. tertiolecta. The synthesis and appearance of specific proteins were followed by labeling with (14)C-bicarbonate.