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| Titel |
Satellite views of the seasonal and interannual variability of phytoplankton blooms in the eastern China seas over the past 14 yr (1998-2011) |
| VerfasserIn |
X. He, Y. Bai, D. Pan, C.-T. A. Chen, Q. Cheng, D. Wang, F. Gong |
| 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. 7 ; Nr. 10, no. 7 (2013-07-15), S.4721-4739 |
| Datensatznummer |
250018340
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| Publikation (Nr.) |
 copernicus.org/bg-10-4721-2013.pdf |
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| Zusammenfassung |
| The eastern China seas are some of the largest marginal seas in the world,
where high primary productivity and phytoplankton blooms are often observed.
However, little is known about their systematic variation of phytoplankton
blooms on large spatial and long temporal scales due to the difficulty of
monitoring bloom events by field measurement. In this study, we investigated
the seasonal and interannual variability and long-term changes in
phytoplankton blooms in the eastern China seas using a 14 yr (1998–2011) time
series of satellite ocean colour data. To ensure a proper satellite dataset to
figure out the bloom events, we validated and corrected the satellite-derived
chlorophyll concentration (chl a) using extensive in situ datasets from two
large cruises. The correlation coefficients between the satellite retrieval
data and the in situ chl a on the logarithmic scale were 0.85 and 0.72 for
the SeaWiFS and Aqua/MODIS data, respectively. Although satellites generally
overestimate the chl a, especially in highly turbid waters, both the in
situ and satellite data show that the overestimation of satellite-derived
chl a has an upper limit value (10 μg L−1), which can be
used as a threshold for the identification of phytoplankton blooms to avoid
the false blooms resulting from turbid waters. Taking
10 μg L−1 as the threshold, we present the spatial-temporal
variability of phytoplankton blooms in the eastern China seas over the past
14 yr. Most blooms occur in the Changjiang Estuary and along the coasts of
Zhejiang, with a maximal frequency of 20% (about 73 days per year). The
coasts of the northern Yellow Sea and the Bohai Sea also have high-frequency
blooms (up to 20%). The blooms show significant seasonal variation, with
most occurring in spring (April–June) and summer (July–September). The
study also revealed a doubling in bloom intensity in the Yellow Sea and Bohai
Sea during the past 14 yr. The nutrient supply in the eastern China seas
might be a major controlling factor in bloom variation. The time series in
situ nutrient datasets show that both the nitrate and phosphate
concentrations increased more than twofold between 1998 and 2005 in the
Yellow Sea. This might be the reason for the doubling of the bloom intensity
index in the Yellow Sea and Bohai Sea. In contrast, there has been no
significant long-term increase or decrease in the Changjiang Estuary, which
might be regulated by the Changjiang River discharge. These results offer a
foundation for the study of the influence of phytoplankton blooms on the
carbon flux estimation and biogeochemical processes in the eastern China
seas. |
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