TEMPERATURE-NITRATE RELATIONSHIPS IN THE CENTRAL AND EASTERN TROPICALPACIFIC

The relationship between temperature and nitrate in the upper 200 m of the central and eastern tropical Pacific was investigated using regre ssion techniques, and the slope of this relationship was compared alon g spatial and temporal dimensions. In the open-ocean waters of the eas tern and central Pacific, variation in the slope of the temperature-ni trate (TN) relationship was primarily north-south, with the steepness of the slope decreasing to the south. In the more coastal waters of th e southeastern Pacific, however, the slope showed strong gradients in the east-west direction, with the slope steepening from west to east. Seasonal trends in the slope of the TN relationship were examined alon g the equator. During March-May the relatively flat slope of the TN re lationship that is found year-round in the central Pacific is found to extend further east, associated with the intensification and shoaling of the Equatorial Undercurrent during this same period. Regressions p redicting nitrate from temperature were tested on new data and errors of prediction were low for open-ocean locations (1.4 mu M); however, e rrors increased (to 3.2-4.3 mu M) With proximity to coastal waters, re flecting the increasing and variable contribution of nitrate uptake by phytoplankton.