Coupled C, N, P, and O Biogeochemical Cycling at the Land-Ocean Interface

This chapter deals with the dynamics of the coupled biogeochemical cycles of carbon, nitrogen, phosphorus, and oxygen at the land-ocean interface and within the global coastal ocean. Future land-use changes will lead to increasing riverine fluxes of C, N, and P to the coastal ocean, augmented by atmospheric nitrogen loading of coastal environments. The excess nutrients will stimulate primary production and respiration/decomposition of this organic carbon and that brought in by rivers will lead to changes in the trophic status of coastal marine environments and to more environments exhibiting hypoxic and anoxic conditions. The coastal ocean is currently a net source of CO₂ to the atmosphere but soon will switch to a sink. This switch coupled with increasing atmospheric deposition of N will lead to further acidification of coastal ocean waters. There is little doubt that unless C, N, and P anthropogenic fluxes from land are better managed in the future, proximal coastal ocean environments, including the estuarine and reef systems that are critical to fisheries, will be especially vulnerable to changes in their ecosystem dynamics.