Nitrogen Fixation in the Marine Environment

Tremendous progress has been made in the past several decades in the realm of marine nitrogen (N2) fixation. The spectrum of organisms recognized to contribute to N2 fixation in the sea has been greatly expanded, and there has been a virtual revolution 

The development of a convenient field assay for N2 fixation in the late 1960s (Stewart et al, 1967 Hardy et al, 1968) which was rapidly adapted for marine studies (see Capone 1983, 1993), led to a flurry of field efforts in a range of open ocean and shallow water and benthic marine environments. We wiU first summarize some of the recent advances and insights relative to N2 fixation in benthic marine environments, move on to the water column, summarize the controls on N2 fixation and comment on the broader, biogeochemical impacts of N2 fixation. 

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Capone, D. G., and Carpenter, E. J. (1982a). Nitrogen fixation in the marine environment. Science. 217, 1140-1142. 

Nitrogen fixation in the marine environment occurs in benthic (sediments and microbial mats) and pelagic environments, and in salt marsh soils (see Carpenter and Capone, Chapter 4, this volume). Since very diverse microorganisms that span the Bacteria and Archaea domains of life can fix nitrogen, it is often difficult to ascertain which organisms are responsible for observed nitrogen fixation rates. Our discussion of the application of molecular approaches to the study of marine nitrogen fixation is brief because it has been reviewed extensively elsewhere (Carpenter and Capone, Chapter 4, this volume Foster and O MuUan Chapter 27, this volume Scanlan and Post, Chapter 24, this volume Paerl and Zehr, 2000 Zehr and Ward, 2002 Zehr et al., 2003). 

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