Chemical Oceanography: The chemistry of the ocean is closely tied to ocean circulation, climate, the plants and animals that live in the ocean, and the exchange of material with the atmosphere, cryosphere, continents, and mantle. The ocean is unique in that it contains - in greater or lesser quantities - nearly every element in the periodic table. Much of chemical oceanography describes the cycling of these elements both within the ocean and with the other spheres of the Earth system. These cycles are usually characterised as quantitative fluxes between constituent reservoirs defined within the ocean system and as residence times within the ocean. Of particular global and climatic significance are the cycles of the biologically active elements such as carbon, nitrogen, and phosphorus as well as those of some important trace elements such as iron.