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| Titel |
The fate of riverine nutrients on Arctic shelves |
| VerfasserIn |
V. Fouest, M. Babin, J.-É. Tremblay |
| 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 ; 10, no. 6 ; Nr. 10, no. 6 (2013-06-04), S.3661-3677 |
| Datensatznummer |
250018276
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| Publikation (Nr.) |
 copernicus.org/bg-10-3661-2013.pdf |
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| Zusammenfassung |
| Present and future levels of primary production (PP) in the Arctic Ocean
(AO) depend on nutrient inputs to the photic zone via vertical mixing,
upwelling and external sources. In this regard, the importance of horizontal
river supply relative to oceanic processes is poorly constrained at the
pan-Arctic scale. We compiled extensive historical (1954–2012) data on
discharge and nutrient concentrations to estimate fluxes of nitrate, soluble
reactive phosphate (SRP), silicate, dissolved organic carbon (DOC),
dissolved organic nitrogen (DON), particulate organic nitrogen (PON) and particulate organic carbon (POC) from 9 large
Arctic rivers and assess their potential impact on the biogeochemistry of
shelf waters. Several key points can be emphasized from this analysis. The
contribution of riverine nitrate to new PP (PPnew) is very small at the
regional scale (< 1% to 6.7%) and negligible at the pan-Arctic
scale (< 0.83%), in agreement with recent studies. By consuming
all this nitrate, oceanic phytoplankton would be able to use only 14.3%
and 8.7–24.5% of the river supply of silicate at the pan-Arctic and
regional scales, respectively. Corresponding figures for SRP are 28.9%
and 18.6–46%. On the Beaufort and Bering shelves, riverine SRP cannot
fulfil phytoplankton requirements. On a seasonal basis, the removal of
riverine nitrate, silicate and SRP would be the highest in spring and not in
summer when AO shelf waters are nitrogen-limited. Riverine DON is
potentially an important nitrogen source for the planktonic ecosystem in
summer, when ammonium supplied through the photoammonification of refractory
DON (3.9 × 109 mol N) may exceed the combined riverine supply of
nitrate and ammonium (3.4 × 109 mol N). Nevertheless, overall nitrogen
limitation of AO phytoplankton is expected to persist even when projected
increases of riverine DON and nitrate supply are taken into account. This
analysis underscores the need to better contrast oceanic nutrient supply
processes with the composition and fate of changing riverine nutrient
deliveries in future scenarios of plankton community structure, function and
production in the coastal AO. |
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