Carbon–Nitrogen–Phosphorus Fluxes in the Coastal Zone: The LOICZ Approach to Global Assessment

Abstract

One of the major questions within the Land–Ocean Interaction in the Coastal Zone (LOICZ) Core Project is to evaluate the role of the coastal ocean in global carbon–nitrogen–phosphorus cycles. Carbon is generally considered to be the “major currency” within the International Geosphere-Biosphere Programme (IGBP), and the nitrogen and phosphorus cycles are intimately linked to carbon. Various authors (e.g., Smith and Mackenzie 1987; Smith and Hollibaugh1993; Sarmiento and Sundquist 1992) have argued that the ocean is net heterotrophic, and Smith and Hollibaugh (1993) have made the case that most of this net heterotrophy probably occurs in the coastal ocean. Evidence suggests that human activity can shift (indeed, is shifting) the trophic status of the coastal ocean toward increasing net heterotrophy (e.g., Rabouille et al. 2001). At the same time, other authors (Kemp et al. 1997) have argued that some parts of the coastal zone are presently clearly net autotrophic, arguing that this could represent a shift historically as a result of growing coastal eutrophication. Obviously, addressing this question becomes a major piece in the puzzle of evaluating the role of oceanic biological reactions in the global carbon cycle.