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General Session 4: Marine environment, ecosystem & sustainability |
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Alkaline phosphatase activity and phytoplankton phosphorus stress in the continental marginal sea with large river plume
GS4-42
Yu Mo* , Guangxi Colleges and Universities Key Laboratory of Utilization of Microbial and Botanical Resources ,Guangxi University for Nationalities, Nanning, Guangxi, China
Yuyuan Xie, Key Laboratory of Coastal and Wetland Ecosystems, Ministry of Education, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Lizhen Lin, Key Laboratory of Coastal and Wetland Ecosystems, Ministry of Education, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Bangqin Huang, Key Laboratory of Coastal and Wetland Ecosystems, Ministry of Education, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Presenter Email: myumore@foxmail.com
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| Phosphate is known to be a limiting nutrient for phytoplankton bloom in the East China Sea, however, little study was carried out how phosphorus stress/limitation of phytoplankton on spatial-temporal and bulk-species scales. Here we report phytoplankton phosphorus stress using alkaline phosphatase activity (APA) assay, four cruises covering seasonal and spatial variations were conducted during 2009-2011, bulk and cell-specific alkaline phosphatase activity were measured in the East China Sea (ECS). The results indicated that APA showed spatial distribution in spring and summer. In spring, bulk APA ranged from 0.84~80.60 nmol h-1 L-1, ELF labeling ratios of dinoflagellates were positively correlated to salinity (p<0.01), showing an increasing trend in offshore direction. Prorocentrum donghaiense was insensitive to ELF labeling (average 23% ), which bloomed in coastal area in spring. In summer, bulk APA ranged from 0.52~559.05 nmol h-1 L-1, a decreasing trend was presented with the highest value in coastal diluted water. Bulk APA during autumn was supported by the high percentage (57%) of soluble APA contributing to total APA accompanied by the low ELF labeling of dominant phytoplankton species/genera, with values fluctuating around 20%. Pm was significantly higher during winter (mean 7.5¡À1.7 mg C h-1 ¦Ìg Chl a-1) than any other seasons (p<0.01), and was lowest during summer (mean 2.1¡À1.8 mg C h-1 ¦Ìg Chl a-1) (p<0.01). Pm in low range (0.2-3.8 mgC h-1 ¦ÌgChl a-) and high range (6.6-12 mgC h-1 ¦ÌgChl a-1) was accompanied by low bulk APA below 40 nmol h-1 L-1. In the range of 3.8-6.6 mgC h-1 ¦ÌgChl a-1 was accompanied by high and low bulk APA. Based on the results of the bulk, fractioned and cell-specific APA, and regression analyses of bulk APA and Pm, it indicated that phytoplankton suffered from P stress during spring, while P stress was intense and even changed into P limitation in summer, P stress of phytoplankton was relieved in autumn and vanished in winter in the ECS.
Key words: Alkaline phosphatase, Phosphorus stress, Phytoplankton, the light-saturated photosynthetic rate, Seasonal variations, East China Sea
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