A study of absorption characteristics of chromophoric dissolved organic matter and particles in Lake Taihu,China |
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| Authors: | Yunlin Zhang Bing Zhang Xin Wang Junsheng Li Sheng Feng Qiaohua Zhao Mingliang Liu Boqiang Qin |
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| Institution: | (1) State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, P.R. China;(2) State Key Laboratory of Remote Sensing Science, Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University, Beijing, 100101, P.R. China;(3) Department of Environment Science and Engineering, Nanjing University of Information and Technology, Nanjing, 210044, P.R. China;(4) Graduate School of Chinese Academy of Sciences, Beijing, 100039, P.R. China |
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| Abstract: | Absorptions by non-phytoplankton particles and phytoplankton, and chromophoric dissolved organic matter (CDOM) were measured
at 50 sites in large, shallow, Lake Taihu in winter and summer 2006 to study their seasonal and spatial variations, and their
relative contributions to total absorption. The CDOM absorption was significantly higher in winter than in summer, due to
degradation and release of fixed carbon in phytoplankton and submerged aquatic vegetation (SAV). The hyperbolic model was
used to model the spectral absorption of CDOM, and the mean spectral slope of 6.38 nm−1 was obtained. At most sites, the spectral absorption of non-phytoplankton particles was similar to that of the total particles,
demonstrating that the absorption of the total particles is dominated by the absorption of non-phytoplankton particles. In
summer, phytoplankton absorption increased markedly, due to frequent algal blooms especially in Meiliang Bay. In winter, the
significant increase in non-phytoplankton particle absorption resulted from the increase of inorganic particulate matter caused
by sediment resuspension. Strong linear relationships were found between a
d(440) and total suspended matter (TSM), organic suspended matter (OSM), and inorganic suspended matter (ISM). Strong linear
relationships were also found between a
ph(440), a
ph(675) and chlorophyll a (Chl-a) concentration. The total relative contributions of non-phytoplankton particles over the range of photosynthetically active
radiation (PAR) (400–700 nm) were 48.4 and 79.9% in summer and winter respectively. Non-phytoplankton particle absorption
dominated the total absorption, especially in winter, in Lake Taihu, due to frequent sediment resuspension in the large shallow
lake as a result of strong windy conditions. The results indicate that strong absorption by CDOM and non-phytoplankton particles
at the blue wavelength has an impact on the spectral availability, and acts as a selection factor for the composition of the
phytoplankton community, with cyanobacteria being the dominate species in Lake Taihu.
Handling editor: L. Naselli-Flores |
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| Keywords: | Absorption coefficient Chromophoric dissolved organic matter Lake Taihu non-phytoplankton particle Phytoplankton |
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