FROM INDIVIDUAL PLANKTON CELLS TO PELAGIC MARINE ECOSYSTEMS
AND TO GLOBAL BIOGEOCHEMICAL CYCLES 1
L. Legendre 2 and J. Le Fevre 3
2Departement de biologie,
Universite Laval,
Quebec, Quebec, Canada, GIK 7P4
3Laboratoire d' Oceanographie Biologique,
Universite de Bretagne Occidentale,
29287 Brest Cedex, France
ABSTRACT
It is often assumed that the biological CO2 pump in the oceans is essentially driven by the upward flux of No..·,
so that the potential export of biogenic carbon from the upper ocean is stoichiometrically equivalent to N-derived
phytoplankton new production. The steady-state/stoichiometry model does not consider that ecosystem dynamics
have a significant influence on the export or sequestration of biogenic carbon. Contrary to this assumption, there
are several cases where ecosystems do have a significant effect on the export and sequestration of biogenic
carbon. These include the fixation of nitrogen gas in the upper layer of the ocean (phytoplankton and coral reefs),
the export of carbon by organisms with high carbon content (thecate dinoflagellates, coccolithophores,
foraminifers, pteropods), the production of long-lived dissolved organic matter, and the fact that the pathways
of export may differ in length and complexity. This is considered within the context of a general typology of
pelagic marine ecosystems, based on the various possible combinations linking standing stock to production of
phytoplankton: (1) production and standing stock dominated by large cells (e.g. upwelling, ice-edge and episodic
blooms); (2) production by small and large cells, standing stock dominated by large cells (e.g. exceptional
blooms); (3) production and standing stock of small and large cells (e.g. spring bloom in the North Atlantic);
(4) production by small and large cells, standing stock dominated by small cells (e.g. Alaskan Gyre in the North
Pacific); (5) production and standing stock dominated by small cells (e.g. oligotrophic ocean). These five types
of ecosystems correspond to different modes of phytoplankton production (as controlled by hydrodynamics) and
different structures (as reflected in the standing stocks), which influence the pathways of carbon export and
sequestration as well as the renewable marine resources.
INTRODUCTION
One of the most pressing issues presently confronting the scientific community, worldwide,
is the possible rapid global warming of the Earth. The recent anthropogenic increase in
atmospheric carbon dioxide may be responsible for about half this global warming
, Contribution to the programme of GIROQ (Groupe interuniversitaire de recherches oceanographiques du
Quebec) and Unite de recherche D13630, Centre National de la Recherche Scientifique (France)
NATO AS! Series. Vol. G 27
Particle Analysis in Oceanography
Edited by S. Demers
© Springer-Verlag Berlin Heidelberg 1991
AND TO GLOBAL BIOGEOCHEMICAL CYCLES 1
L. Legendre 2 and J. Le Fevre 3
2Departement de biologie,
Universite Laval,
Quebec, Quebec, Canada, GIK 7P4
3Laboratoire d' Oceanographie Biologique,
Universite de Bretagne Occidentale,
29287 Brest Cedex, France
ABSTRACT
It is often assumed that the biological CO2 pump in the oceans is essentially driven by the upward flux of No..·,
so that the potential export of biogenic carbon from the upper ocean is stoichiometrically equivalent to N-derived
phytoplankton new production. The steady-state/stoichiometry model does not consider that ecosystem dynamics
have a significant influence on the export or sequestration of biogenic carbon. Contrary to this assumption, there
are several cases where ecosystems do have a significant effect on the export and sequestration of biogenic
carbon. These include the fixation of nitrogen gas in the upper layer of the ocean (phytoplankton and coral reefs),
the export of carbon by organisms with high carbon content (thecate dinoflagellates, coccolithophores,
foraminifers, pteropods), the production of long-lived dissolved organic matter, and the fact that the pathways
of export may differ in length and complexity. This is considered within the context of a general typology of
pelagic marine ecosystems, based on the various possible combinations linking standing stock to production of
phytoplankton: (1) production and standing stock dominated by large cells (e.g. upwelling, ice-edge and episodic
blooms); (2) production by small and large cells, standing stock dominated by large cells (e.g. exceptional
blooms); (3) production and standing stock of small and large cells (e.g. spring bloom in the North Atlantic);
(4) production by small and large cells, standing stock dominated by small cells (e.g. Alaskan Gyre in the North
Pacific); (5) production and standing stock dominated by small cells (e.g. oligotrophic ocean). These five types
of ecosystems correspond to different modes of phytoplankton production (as controlled by hydrodynamics) and
different structures (as reflected in the standing stocks), which influence the pathways of carbon export and
sequestration as well as the renewable marine resources.
INTRODUCTION
One of the most pressing issues presently confronting the scientific community, worldwide,
is the possible rapid global warming of the Earth. The recent anthropogenic increase in
atmospheric carbon dioxide may be responsible for about half this global warming
, Contribution to the programme of GIROQ (Groupe interuniversitaire de recherches oceanographiques du
Quebec) and Unite de recherche D13630, Centre National de la Recherche Scientifique (France)
NATO AS! Series. Vol. G 27
Particle Analysis in Oceanography
Edited by S. Demers
© Springer-Verlag Berlin Heidelberg 1991