Different tolerances and responses to low temperature and darkness between waterbloom forming cyanobacterium <Emphasis Type="Italic">Microcystis</Emphasis> and a green alga <Emphasis Type="Italic">Scenedesmus</Emphasis> |
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Authors: | Zhongxing Wu Lirong Song Renhui Li |
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Institution: | (1) Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, P.R. China |
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Abstract: | The dynamics of planktonic cyanobacteria in eutrophicated freshwaters play an important role in formation of annual summer
blooms, yet overwintering mechanisms of these water bloom forming cyanobacteria remain unknown. The responses to darkness
and low temperature of three strains (unicellular Microcystis aeruginosa FACHB-905, colonial M. aeruginosa FACHB-938, and a green alga Scenedesmus
quadricauda FACHB-45) were investigated in the present study. After a 30-day incubation under darkness and low temperature, cell morphology,
cell numbers, chlorophyll a, photosynthetic activity (ETRmax and I
k), and malodialdehyde (MDA) content exhibited significant changes in Scenedesmus. In contrast, Microcystis aeruginosa cells did not change markedly in morphology, chlorophyll a, photosynthetic activity, and MDA content. The stress caused by low temperature and darkness resulted in an increase of the
antioxidative enzyme-catalase (CAT) in all three strains. When the three strains re-grew under routine cultivated condition
subjected to darkness and low temperature, specific growth rate of Scenedesmus was lower than that of Microcystis. Flow cytometry (FCM) examination indicated that two distinct types of metabolic response to darkness and low temperature
existed in the three strains. The results from the present study reveal that the cyanobacterium Microcystis, especially colonial Microcystis, has greater endurance and adaptation ability to the stress of darkness and low temperature than the green alga Scenedesmus.
Handling editor: D. Hamilton |
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Keywords: | Darkness Low temperature Response Tolerance Microcystis Scenedesmus |
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