16 The Role of Iron as a Limiting Nutrient for Marine " Plankton Processes

Our understanding of elemental cycling in the ocean, its mechanisms and implications for ecology and climate, has undergone revolutionary change since the previous SCOPE volume was published in 1983 (Bolin and Cook 1983). The most notable of the advances in ocean biogeochemistry concern the role of the oceans in the global carbon cycle (Hanson, Ducklow, and Field 2000) and recognition of iron as a key nutrient limiting ocean photosynthesis, carbon storage, and glacial-interglacial variations in atmospheric carbon dioxide concentrations. De Baar (1994) elegantly and comprehensively reviewed iron limitation up to the advent of the in situ iron fertilization studies of the past decade (see below). In this chapter we outline biological control of the ocean carbon cycle, focusing on the role of iron and its interactions with carbon, nitrogen, and phosphorus.