Passage V

Nutrients in seawater are removed by phytoplankton and other marine organisms. Figure 1 shows the concentrations of 3 nutrients—nitrate (NO₃^—), dissolved inorganic phosphorus (DIP), and silicic acid(H₄SiO₄)—at various depths in the Atlantic, Pacific, and Indian Oceans. Table 1 shows the average concentrations and the estimated residence times (how long an ion or molecule of a nutrient remains in the ocean) for the 3 nutrients in deep (> 3 km) Atlantic and Pacific waters. Figure 2 shows how the NO₃^— concentration in Pacific surface waters (< 0.3 km depth) varies with latitude.

Figure 1 adapted from J. Andrews, P. Brimblecombe, T. Jickells, and P. Liss, An Introduction to Environmental Chemistry. @1996 by Blackwell Science Ltd.

Figure 2 adapted from James Murray et al., "Physical and Biological Controls on Carbon Cycling in the Equatorial Pacific." @1994 by the American Association for the Advancement of Sclence.