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| Titel |
Drivers of trophic amplification of ocean productivity trends in a changing climate |
| VerfasserIn |
C. A. Stock, J. P. Dunne, J. G. John |
| 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 ; 11, no. 24 ; Nr. 11, no. 24 (2014-12-16), S.7125-7135 |
| Datensatznummer |
250117739
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| Publikation (Nr.) |
 copernicus.org/bg-11-7125-2014.pdf |
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| Zusammenfassung |
| Pronounced projected 21st century trends in regional oceanic net primary
production (NPP) raise the prospect of significant redistributions of marine
resources. Recent results further suggest that NPP changes may be amplified
at higher trophic levels. Here, we elucidate the role of planktonic food web
dynamics in driving projected changes in mesozooplankton production (MESOZP)
found to be, on average, twice as large as projected changes in NPP by the
latter half of the 21st century under a high emissions scenario in the
Geophysical Fluid Dynamics Laboratory's ESM2M–COBALT (Carbon, Ocean Biogeochemistry and Lower Trophics) earth system model.
Globally, MESOZP was projected to decline by 7.9% but regional MESOZP
changes sometimes exceeded 50%. Changes in three planktonic food web
properties – zooplankton growth efficiency (ZGE), the trophic level of
mesozooplankton (MESOTL), and the fraction of NPP consumed by zooplankton
(zooplankton–phytoplankton coupling, ZPC), explain the projected
amplification. Zooplankton growth efficiencies (ZGE) changed with NPP,
amplifying both NPP increases and decreases. Negative amplification (i.e.,
exacerbation) of projected subtropical NPP declines via this mechanism was
particularly strong since consumers in the subtropics have limited surplus
energy above basal metabolic costs. Increased mesozooplankton trophic level
(MESOTL) resulted from projected declines in large phytoplankton production.
This further amplified negative subtropical NPP declines but was secondary
to ZGE and, at higher latitudes, was often offset by increased ZPC. Marked
ZPC increases were projected for high-latitude regions experiencing shoaling
of deep winter mixing or decreased winter sea ice – both tending to increase
winter zooplankton biomass and enhance grazer control of spring blooms.
Increased ZPC amplified projected NPP increases in the Arctic and damped
projected NPP declines in the northwestern Atlantic and Southern Ocean.
Improved understanding of the physical and biological interactions governing
ZGE, MESOTL and ZPC is needed to further refine estimates of climate-driven
productivity changes across trophic levels. |
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