Of the 3 boreal summers covered by the EGEE oceanographic cruises between 2005 and 2007, equatorial upwelling was strongest along 10oW in June 2005 and weakest in June 2006. In response to the shoaling pycnocline, cold nutrient-rich waters upwelled to the euphotic layer and significantly influenced the biological productivity of the region in June 2005. Using profiles for temperature, salinity and dissolved oxygen (at the latitude of Equatorial Under-Current (EUC) velocity core) and chlorophyll fluorescence profile (at the latitude of maximum occurrences within the EUC latitude bands), the hypothesis of the EUC contributing to the equatorial fertility process along 10oW was captured. While nitrate was limiting to phytoplankton growth in June 2006 and June 2007, phosphate stress was observed in June 2005.
