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| Titel |
A coupled physical-biological model of the Northern Gulf of Mexico shelf: model description, validation and analysis of phytoplankton variability |
| VerfasserIn |
K. Fennel, R. Hetland, Y. Feng, S. DiMarco |
| 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 ; 8, no. 7 ; Nr. 8, no. 7 (2011-07-13), S.1881-1899 |
| Datensatznummer |
250006049
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| Publikation (Nr.) |
 copernicus.org/bg-8-1881-2011.pdf |
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| Zusammenfassung |
| The Texas-Louisiana shelf in the Northern Gulf of Mexico receives
large inputs of nutrients and freshwater from the
Mississippi/Atchafalaya River system. The nutrients stimulate high
rates of primary production in the river plume, which contributes to
the development of a large and recurring hypoxic area in summer, but the
mechanistic links between hypoxia and river discharge of freshwater
and nutrients are complex as the accumulation and vertical export of
organic matter, the establishment and maintenance of vertical
stratification, and the microbial degradation of organic matter are
controlled by a non-linear interplay of factors.
Unraveling these interactions will have to rely on a combination of observations and models. Here we
present results
from a realistic, 3-dimensional, physical-biological model with focus
on a quantification of nutrient-stimulated phytoplankton growth, its variability and the fate of this organic matter.
We demonstrate that the model realistically
reproduces many features of observed nitrate and phytoplankton
dynamics including observed property distributions and rates. We then
contrast the environmental factors and phytoplankton source and sink
terms characteristic of three model subregions that represent an
ecological gradient from eutrophic to oligotrophic conditions. We
analyze specifically the reasons behind the counterintuitive
observation that primary production in the light-limited plume region
near the Mississippi River delta is positively correlated with river
nutrient input, and find that, while primary production and
phytoplankton biomass are positively correlated with nutrient load,
phytoplankton growth rate is not. This suggests that accumulation of
biomass in this region is not primarily controlled bottom up by
nutrient-stimulation, but top down by systematic differences in the
loss processes. |
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