Photoinhibition of colonial and unicellular Microcystis cells in a summer bloom in Lake Taihu |
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Authors: | Xiaodong Wu Fanxiang Kong Min Zhang |
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Affiliation: | (1) Asian International Rivers Center, Yunnan University, No. 2 North Road of Green Lake, Kunming, 650091, People’s Republic of China;(2) State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 Beijing East Road, Nanjing, 210008, People’s Republic of China |
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Abstract: | To evaluate the photoinhibition of colonial and unicellular cells of Microcystis aeruginosa under natural conditions, the maximum and effective quantum yields of photosystem II were measured from variable chlorophyll a fluorescence in samples from Lake Taihu during a summer bloom from June 19 to 21, 2006. Diurnal changes in the photoinhibition of Microcystis cells incubated immediately below the surface in clear bottles for 30 min and in situ samples under natural conditions were measured. At solar noon during the three days, the mean values of maximum quantum yield (F v/F m) and effective quantum yield (ΔF/F m′) for unicellular cells (F v/F m = 0.15, ΔF/F m′ = 0.10) were lower than those for colonial cells (F v/F m = 0.25, ΔF/F m′ = 0.15). For in situ samples, the values of F v/F m and ΔF/F m′ for colonial cells at solar noon on the three days (F v/F m 0.30, 0.25, 0.29; ΔF/F m′ 0.24, 0.21, 0.22) were also higher than those of unicellular cells (F v/F m 0.26, 0.18, 0.25; ΔF/F m′ 0.15, 0.11, 0.14). The results indicate that colony formation has a protective effect on Microcystis cells by reducing the occurrence of photoinhibition under high light intensities. |
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