This study investigates the diversity, abundance, and activity of marine diazotrophs in the South Pacific. Samples were collected onboard R/V Kilo Moana in March–April 2007 from Coral Sea, Australia (155°E, 15°S), moving southeast (to 160°E, 30°S), then returning back to New Caledonian and Fijian waters, reaching 170°W, 15°S. Samples were taken from 23 stations over 34 days. The nifH gene was targeted to determine qualitative and quantitative information about the nitrogen fixing community present. For this, water was filtered at sea to collect DNA and then frozen and shipped to the lab for further analysis.