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| Titel |
Influence of the Changjiang River on the light absorption properties of phytoplankton from the East China Sea |
| VerfasserIn |
S. Q. Wang, J. Ishizaka, H. Yamaguchi, S. C. Tripathy, M. Hayashi, Y. J. Xu, Y. Mino, T. Matsuno, Y. Watanabe, S. J. Yoo |
| 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. 7 ; Nr. 11, no. 7 (2014-04-03), S.1759-1773 |
| Datensatznummer |
250117340
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| Publikation (Nr.) |
 copernicus.org/bg-11-1759-2014.pdf |
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| Zusammenfassung |
| Phytoplankton light absorption properties were investigated at the surface
and subsurface chlorophyll a maximum (SCM) layer in the East China Sea
(ECS), a marginal sea which is strongly influenced by the Changjiang
discharge in summer. Results from ECS were compared with those from the
Tsushima Strait (TS) where the influence of Changjiang discharge is less. The
probable controlling factors, packaging effect (cell size) and pigment
composition of total chlorophyll a (Tchl a)-specific absorption
coefficient (aph*(λ)) were examined by the
corresponding measurements of pigments identified by high-performance liquid
chromatography. We observed distinct phytoplankton size structure and thereby
absorption properties between ECS and TS. At the surface, mixed populations
of micro-, nano- and pico-phytoplankton were recorded in ECS while
pico-phytoplankton dominated in TS, generating a lower average
aph*(λ) in ECS than in TS. Within SCM, average
aph*(λ) was higher in ECS than in TS because of the
dominance of nano- and micro-phytoplankton in ECS and TS, respectively. By
pooling surface and SCM samples, we found regular trends in phytoplankton
size-fraction versus Tchl a; and correlations between aph*(λ) and Tchl a consistent with previous observations for the
global ocean in TS but not in ECS. In ECS phytoplankton size-fraction was not
correlated with Tchl a, which consequently caused poor relationships
between aph*(λ) and Tchl a. The abnormal values
mainly originated from the surface low-salinity waters and SCM waters beneath
them. At high Tchl a, aph*(λ) of these samples was
substantially higher compared to the values in TS and from the global
regressions, which was attributable to the lower micro-phytoplankton
fraction, and higher nano- and/or pico-phytoplankton fractions in ECS. These
observations indicated that the distinct light absorption properties of
phytoplankton in ECS were possibly influenced by the Changjiang discharge.
Our findings imply that general bio-optical algorithms proposed based on the
correlations between aph*(λ) and Tchl a or the
patterns in size-fraction versus Tchl a are not applicable in ECS, and need
to be carefully considered when using these general algorithms in
river-influenced regions. |
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