Photosynthetic activity of bloom-forming cyanobacteria in winter and their relationship with light intensity
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Some species of cyano-bacteria could establish dominance in cold seasons, but their photosynthetic parameters were rarely investigated in previous studies. Thus, photosynthetic properties of bloom-forming cyano-bacteria (mainly Anabaena flos-aquae) were investigated in a large shallow lake (Chaohu Lake, China) on January 12, 2013. Chlorophyll fluorescence parameter (F/Fm’) was measured by a pulse amplitude modulation fluoro-meter (Phyto-PAM) in order to estimate algal photosynthetic activity. In situ measurement showed that there was no obvious relationship between F/Fm’ and light intensity at 10:30, while F/Fm’ changed with irradiation at 12:30 and 14:30. However, this change disappeared after dark adaptation for three hours. In the experiment, when samples from different depths were exposed to the same solar radiation, there was no variation in F/Fm’ of samples from different depths at 10:30, 12:30, and 14:30. These results showed that bloom-forming cyano-bacteria maintain feeble photosynthetic activity under low light intensity in winter, while they were exposed to sufficient light intensity, and seasonal changes may be triggered and grow gradually with elevated light intensity. Phyto-PAM measurement helps us to better understand over-wintering cyano-bacteria and recruitment process in the cold seasons.
Fresenius Environmental Bulletin
Environmental Sciences not elsewhere classified