Non-Redfield C : N Ratio of Transparent Exopolymeric Particles in the Northwestern Mediterranean Sea

The stoichiometric model of Redfield, which describes the elemental composition of marine organic matter, is generally used to link the production of new organic matter to the uptake of nitrate. The Redfield C : N molar ratio of 6.6 is a well-established value for particulate organic matter produced...

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Bibliographic Details
Published in:Limnology and oceanography 2001-11, Vol.46 (7), p.1831-1836
Main Authors: Mari, Xavier, Beauvais, Sophie, Lemée, Rodolphe, Pedrotti, Maria Luiza
Format: Article
Language:English
Subjects:
Bacteria
Carbon
Earth sciences
Earth, ocean, space
Ecology, environment
Ecosystems
Exact sciences and technology
External geophysics
Geochemistry
Life Sciences
Marine
Marine and continental quaternary
Mineralogy
Nitrates
Nitrogen
Oceans
Particulate matter
Physical and chemical properties of sea water
Physics of the oceans
Phytoplankton
Sea water
Seas
Silicates
Summer
Surficial geology
Water geochemistry
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Summary:The stoichiometric model of Redfield, which describes the elemental composition of marine organic matter, is generally used to link the production of new organic matter to the uptake of nitrate. The Redfield C : N molar ratio of 6.6 is a well-established value for particulate organic matter produced in surface waters. Yet recent studies have shown that the inorganic C : N uptake ratio during nitrate-limiting conditions is > 14. This non-Redfield behavior during the production of new organic matter suggests that a large standing stock of organic matter, rich in carbon, should accumulate in the euphotic zone from the spring bloom to late summer. This hypothetical pool of carbon-rich organic matter and the pool of transparent exopolymeric particles (TEP) exhibit similar seasonal distributions, which suggests that TEP may indeed be this carbon-rich pool. For this scheme to work, TEP should have a high C : N ratio. TEP distribution from an open-ocean site in the northwestern Mediterranean Sea (DYFAMED) was monitored, and TEP C : N ratio was measured from TEP produced in the laboratory by bubbling dissolved organic matter collected in the field. We found that the TEP pool increases during the summer season and that the C : N ratio of TEP produced from naturally occurring dissolved organic matter, is well in excess of the Redfield ratio with an overall average C : N molar ratio of ~20. As a result, the production of TEP could be the main pathway of carbon overconsumption required of oligotrophic, nitrate-limiting waters, and, thus, TEP may represent an important intermediary pool in the ocean carbon cycle.
ISSN:0024-3590
1539-607X
1939-5590
1539-6088
DOI:10.4319/lo.2001.46.7.1831