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| Titel |
Global analysis of seasonality in the shell flux of extant planktonic Foraminifera |
| VerfasserIn |
L. Jonkers, M. Kucera |
| 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 ; 12, no. 7 ; Nr. 12, no. 7 (2015-04-15), S.2207-2226 |
| Datensatznummer |
250117897
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| Publikation (Nr.) |
 copernicus.org/bg-12-2207-2015.pdf |
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| Zusammenfassung |
| Shell fluxes of planktonic Foraminifera species vary intra-annually in a
pattern that appears to follow the seasonal cycle. However, the variation in
the timing and prominence of seasonal flux maxima in space and among species
remains poorly constrained. Thus, although changing seasonality may result in
a flux-weighted temperature offset of more than 5° C within a
species, this effect is often ignored in the interpretation of
Foraminifera-based paleoceanographic records. To address this issue we present an analysis of
the intra-annual pattern of shell flux variability in 37 globally distributed
time series. The existence of a seasonal component in flux variability was
objectively characterised using periodic regression. This analysis yielded
estimates of the number, timing and prominence of seasonal flux maxima. Over
80% of the flux series across all species showed a statistically
significant periodic component, indicating that a considerable part of the
intra-annual flux variability is predictable. Temperature appears to be a
powerful predictor of flux seasonality, but its effect differs among species.
Three different modes of seasonality are distinguishable. Tropical and
subtropical species (Globigerinoides ruber (white and pink varieties),
Neogloboquadrina dutertrei, Globigerinoides sacculifer, Orbulina universa,
Globigerinella siphonifera, Pulleniatina obliquiloculata, Globorotalia menardii, Globoturborotalita rubescens, Globoturborotalita tenella and Globigerinoides conglobatus) appear to have a less predictable flux
pattern, with random peak timing in warm waters. In colder waters,
seasonality is more prevalent: peak fluxes occur shortly after summer
temperature maxima and peak prominence increases. This tendency is stronger
in species with a narrower temperature range, implying that warm-adapted
species find it increasingly difficult to reproduce outside their optimum
temperature range and that, with decreasing mean temperature, their flux is
progressively more focussed in the warm season. The second group includes the
temperate to cold-water species Globigerina bulloides,
Globigerinita glutinata, Turborotalita quinqueloba, Neogloboquadrina incompta, Neogloboquadrina pachyderma,
Globorotalia scitula, Globigerinella calida, Globigerina falconensis, Globorotalia theyeri
and Globigerinita uvula. These species show a highly predictable seasonal
pattern, with one to two peaks a year, which occur earlier in warmer waters.
Peak prominence in this group is independent of temperature. The
earlier-when-warmer pattern in this group is related to the timing of
productivity maxima. Finally, the deep-dwelling Globorotalia truncatulinoides
and Globorotalia inflata show a regular and pronounced peak in winter and
spring. The remarkably low flux outside the main pulse may indicate a long
reproductive cycle of these species. Overall, our analysis indicates that the
seasonality of planktonic Foraminifera shell flux is predictable and reveals
the existence of distinct modes of phenology among species. We evaluate the
effect of changing seasonality on paleoceanographic reconstructions and find
that, irrespective of the seasonality mode, the actual magnitude of
environmental change will be underestimated. The observed constraints on flux
seasonality can serve as the basis for predictive modelling of flux pattern.
As long as the diversity of species seasonality is accounted for in such
models, the results can be used to improve reconstructions of the magnitude
of environmental change in paleoceanographic records. |
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