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| Titel |
Scaling of growth rate and mortality with size and its consequence on size spectra of natural microphytoplankton assemblages in the East China Sea |
| VerfasserIn |
F. H. Chang, E. C. Marquis, C. W. Chang, G. C. Gong, C. H. Hsieh |
| 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. 8 ; Nr. 10, no. 8 (2013-08-05), S.5267-5280 |
| Datensatznummer |
250085284
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| Publikation (Nr.) |
 copernicus.org/bg-10-5267-2013.pdf |
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| Zusammenfassung |
| Allometric scaling of body size versus growth rate and mortality has been
suggested to be a universal macroecological pattern, as described by the
metabolic theory of ecology (MTE). However, whether such scaling generally
holds in natural assemblages remains debated. Here, we test the hypothesis
that the size-specific growth rate and grazing mortality scale with the body
size with an exponent of −1/4 after temperature correction, as MTE
predicts. To do so, we couple a dilution experiment with the FlowCAM imaging
system to obtain size-specific growth rates and grazing mortality of natural
microphytoplankton assemblages in the East China Sea. This novel approach
allows us to achieve highly resolved size-specific measurements that would be
very difficult to obtain in traditional size-fractionated measurements using
filters. Our results do not support the MTE prediction. On average, the
size-specific growth rates and grazing mortality scale almost isometrically
with body size (with scaling exponent ∼0.1). However, this finding
contains high uncertainty, as the size-scaling exponent varies substantially
among assemblages. The fact that size-scaling exponent varies among
assemblages prompts us to further investigate how the variation of
size-specific growth rate and grazing mortality can interact to determine the
microphytoplankton size structure, described by normalized biomass size
spectrum (NBSS), among assemblages. We test whether the variation of
microphytoplankton NBSS slopes is determined by (1) differential grazing
mortality of small versus large individuals, (2) differential growth rate of
small versus large individuals, or (3) combinations of these scenarios. Our
results indicate that the ratio of the grazing mortality of the large size
category to that of the small size category best explains the variation of
NBSS slopes across environments, suggesting that higher grazing mortality of
large microphytoplankton may release the small phytoplankton from grazing,
which in turn leads to a steeper NBSS slope. This study contributes to
understanding the relative importance of bottom-up versus top-down control in
shaping microphytoplankton size structure. |
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