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| Titel |
Response of ocean phytoplankton community structure to climate change over the 21st century: partitioning the effects of nutrients, temperature and light |
| VerfasserIn |
I. Marinov, S. C. Doney, I. D. Lima |
| 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 ; 7, no. 12 ; Nr. 7, no. 12 (2010-12-02), S.3941-3959 |
| Datensatznummer |
250005101
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| Publikation (Nr.) |
 copernicus.org/bg-7-3941-2010.pdf |
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| Zusammenfassung |
| The response of ocean phytoplankton community structure to climate change
depends, among other factors, upon species competition for nutrients and
light, as well as the increase in surface ocean temperature. We propose an
analytical framework linking changes in nutrients, temperature and light
with changes in phytoplankton growth rates, and we assess our theoretical
considerations against model projections (1980–2100) from a global Earth
System model. Our proposed "critical nutrient hypothesis" stipulates the
existence of a critical nutrient threshold below (above) which a nutrient
change will affect small phytoplankton biomass more (less) than diatom
biomass, i.e. the phytoplankton with lower half-saturation coefficient K are
influenced more strongly in low nutrient environments. This nutrient
threshold broadly corresponds to 45° S and 45° N, poleward of which
high vertical mixing and inefficient biology maintain higher surface
nutrient concentrations and equatorward of which reduced vertical mixing and
more efficient biology maintain lower surface nutrients. In the
45° S–45° N low nutrient region, decreases in limiting nutrients –
associated with increased stratification under climate change – are
predicted analytically to decrease more strongly the specific growth of
small phytoplankton than the growth of diatoms. In high latitudes, the
impact of nutrient decrease on phytoplankton biomass is more significant for
diatoms than small phytoplankton, and contributes to diatom declines in the
northern marginal sea ice and subpolar biomes. In the context of our model,
climate driven increases in surface temperature and changes in light are
predicted to have a stronger impact on small phytoplankton than on diatom
biomass in all ocean domains. Our analytical predictions explain reasonably
well the shifts in community structure under a modeled climate-warming
scenario. Climate driven changes in nutrients, temperature and light have
regionally varying and sometimes counterbalancing impacts on phytoplankton
biomass and structure, with nutrients and temperature dominant in the
45° S–45° N band and light-temperature effects dominant in the
marginal sea-ice and subpolar regions. As predicted, decreases in nutrients
inside the 45° S–45° N "critical nutrient" band result in diatom
biomass decreasing more than small phytoplankton biomass. Further
stratification from global warming could result in geographical shifts in
the "critical nutrient" threshold and additional changes in ecology. |
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