On the GO-SHIP cruises, temperature and salinity were recorded at various depths and stations using a Conductivity Temperature Depth (CTD) instrument (54). Nutrients were sampled from seawater collected by a Niskin bottle rosette fitted onto the CTD (55). Nutrient concentrations were photometrically determined from the collected seawater via continuous flow analysis. Nitrate was determined by first reducing nitrate to nitrite in a copperized cadmium column. A sulfanilamide solution and N-Napthylethylene-diamine were introduced to produce a red azo dye (55, 56). To determine phosphate, molybdic acid was introduced to form phosphomolybdic acid.