Widespread iron limitation of phytoplankton in the South Pacific Ocean

Diet fluorescence patterns were discovered in phytoplankton sampled over 70 00 kilometers of the South Pacific Ocean that appear indicative of iron-lim iting growth conditions. These patterns were rapidly Lost after in situ iro n enrichment and were not observed during a 15,000-kilometer transect in th e Atlantic Ocean where iron concentrations are relatively high. Laboratory studies of marine Synechococcus sp, indicated that the patterns in the Sout h Pacific are a unique manifestation of iron limitation on the fluorescence signature of state transitions. Results suggest that primary productivity is iron limited not only throughout the equatorial Pacific but also over mu ch of the vast South Pacific gyre.