most open ocean environments, new sources of nitrogen required to balance the net losses from the
euphotic zone are restricted to upward diffusion or
mixing of NO 3
À from deep water and to local fixation of N 2 gas. In a balanced steady state, the importation rate of new sources of bioavailable
nitrogen will constrain the export of nitrogen (including fisheries production and harvesting). If all
other required nutrients are available, export-rich
ecosystems are those characterized by high bioavailable nitrogen loading such as coastal and open
ocean upwelling regions. These are also the major
regions of fish production in the sea.
See also
Atmospheric Input of Pollutants. Nitrogen Isotopes
in the Ocean. Phosphorus Cycle.
Further Reading
Carpenter EJ and Capone DG (eds.) (1983) Nitrogen in the
Marine Environment. New York: Academic Press.
Conkright ME, O’Brien TD, Levitus S, et al. (1998)
NOAA Atlas NESDIS 37, WORLD OCEAN ATLAS
1998, vol. II: Nutrients and Chlorophyll of the Pacific
Ocean. Washington, DC: US Department of Commerce.
Harvey HW (1966) The Chemistry and Fertility of Sea
Waters. London: Cambridge University Press.
Kirchman DL (ed.) (2000) Microbial Ecology of the
Oceans. New York: Wiley-Liss.
Rogers JE and Whitman WB (eds.) (1991) Microbial
Production and Consumption of Greenhouse Gases:
Methane, Nitrogen Oxides, and Halomethanes.
Washington, DC: American Society for Microbiology.
Schlesinger WH (1997) Biogeochemistry: An Analysis of
Global Change. San Diego: Academic Press.
Wada E and Hattori A (1991) Nitrogen in the Sea: Forms,
Abundances, and Rate Processes. Boca Raton, FL: CRC
Press.
Gas
exchange
Atmosphere
N fixation
2
N 2
PRIMARY
PRODUCERS
CONSUMERS
NO 3
−
NH 4
+
DON
Recycling
Euphotic
zone
NO 3
−
NH 4
+
Diffusion
and
advection
Export
DON
and
PON
Ammonification
Nitrification
Aphotic
zone
DON
and
PON
Nitracline
Export
N 2
Figure 7 Schematic representation of the major pools and transformations/fluxes of nitrogen in a typical open ocean ecosystem.
New sources of bioavailable N (NO 3
À and N 2 in this presentation) continuously resupply nitrogen that is lost via DON and PON export.
These interactions and ocean processes form the conceptual framework for the ‘new’ versus ‘regenerated’ paradigm of nitrogen
dynamics in the sea that was originally proposed by R. Dugdale and J. Goering.
548 NITROGEN CYCLE
euphotic zone are restricted to upward diffusion or
mixing of NO 3
À from deep water and to local fixation of N 2 gas. In a balanced steady state, the importation rate of new sources of bioavailable
nitrogen will constrain the export of nitrogen (including fisheries production and harvesting). If all
other required nutrients are available, export-rich
ecosystems are those characterized by high bioavailable nitrogen loading such as coastal and open
ocean upwelling regions. These are also the major
regions of fish production in the sea.
See also
Atmospheric Input of Pollutants. Nitrogen Isotopes
in the Ocean. Phosphorus Cycle.
Further Reading
Carpenter EJ and Capone DG (eds.) (1983) Nitrogen in the
Marine Environment. New York: Academic Press.
Conkright ME, O’Brien TD, Levitus S, et al. (1998)
NOAA Atlas NESDIS 37, WORLD OCEAN ATLAS
1998, vol. II: Nutrients and Chlorophyll of the Pacific
Ocean. Washington, DC: US Department of Commerce.
Harvey HW (1966) The Chemistry and Fertility of Sea
Waters. London: Cambridge University Press.
Kirchman DL (ed.) (2000) Microbial Ecology of the
Oceans. New York: Wiley-Liss.
Rogers JE and Whitman WB (eds.) (1991) Microbial
Production and Consumption of Greenhouse Gases:
Methane, Nitrogen Oxides, and Halomethanes.
Washington, DC: American Society for Microbiology.
Schlesinger WH (1997) Biogeochemistry: An Analysis of
Global Change. San Diego: Academic Press.
Wada E and Hattori A (1991) Nitrogen in the Sea: Forms,
Abundances, and Rate Processes. Boca Raton, FL: CRC
Press.
Gas
exchange
Atmosphere
N fixation
2
N 2
PRIMARY
PRODUCERS
CONSUMERS
NO 3
−
NH 4
+
DON
Recycling
Euphotic
zone
NO 3
−
NH 4
+
Diffusion
and
advection
Export
DON
and
PON
Ammonification
Nitrification
Aphotic
zone
DON
and
PON
Nitracline
Export
N 2
Figure 7 Schematic representation of the major pools and transformations/fluxes of nitrogen in a typical open ocean ecosystem.
New sources of bioavailable N (NO 3
À and N 2 in this presentation) continuously resupply nitrogen that is lost via DON and PON export.
These interactions and ocean processes form the conceptual framework for the ‘new’ versus ‘regenerated’ paradigm of nitrogen
dynamics in the sea that was originally proposed by R. Dugdale and J. Goering.
548 NITROGEN CYCLE