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| Titel |
Solubilization of particles in sediment traps: revising the stoichiometry of mixed layer export |
| VerfasserIn |
A. N. Antia |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 2, no. 2 ; Nr. 2, no. 2 (2005-08-04), S.189-204 |
| Datensatznummer |
250000492
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| Publikation (Nr.) |
 copernicus.org/bg-2-189-2005.pdf |
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| Zusammenfassung |
| Sinking particles, once caught in sediment trap jars, release dissolved
elements into the surrounding medium through leaching from their pore
fluids, chemical dissolution and the activity of free exoenzymes. This
results in an increase in dissolved elements in the trap jar supernatant.
Elemental fluxes as traditionally measured by sediment traps underestimate
total export when this particle-associated dissolved flux is not considered.
The errors introduced are variable and alter both the absolute levels of
flux as well as the stoichiometry of export. These errors have been
quantified and corrections applied for samples from sediment traps in
the North Atlantic based on measurements of excess dissolved carbon,
nitrogen, phosphorus, silica and calcium in the supernatant of the
collection cups. At the base of the winter mixed layer, on average 90±6%
of phosphorus fluxes are found as excess phosphate whereas for
carbon and nitrogen dissolved concentrations account for 30 (±8)% and
47(±11)% of total fluxes respectively. Excess dissolved silica is on average
61 (±17)% of total biogenic silica flux. Little (<10%) of calcium is
solubilized. The proportion of dissolved to total flux decreases with trap
deployment depth. Calculations of the C:N:P ratios for particles only are
well above the Redfield ratios of 106:16:1 (Redfield et al., 1963), although
the mid-water dissolved N:P and N:Si values as well as the C:N:P ratios of
remineralisation along isopycnals conform to the Redfield ratios at this
site. Accounting for dissolved fluxes of all these elements brings the
stoichiometry of export in agreement with the Redfield Ratio and with other
geochemical estimates of winter mixed layer export. A factor of 3 to 4
higher ratios of organic: inorganic carbon export also implies that the net
atmospheric CO2 sequestration by the biological pump is about 50%
higher at this site when the dissolved elemental fluxes are considered.
Solubilization is thus a process that should be accounted for in protocols
used to measure vertical fluxes with sediment traps. |
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