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| Effects of flood regulation on phytoplankton community structure in the Xiangxi River, a tributary of the Three Gorges Reservoir |
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Abstract Flood control is an important function for Three Gorges Reservoir (TGR). In July 2013 there was 3 flood peaks in TGR and flood regulation was used to block the deluge and reduce the impact on the middle and lower reaches of the Yangtze River. An in situ investigation was conducted to screen the effects of flood regulation on phytoplankton community structure in the Xiangxi River. During the course of flood regulation, the water level in Xiangxi River ranged from 145.63m to 148.36m, the change of the average velocity in the estuary was higher than that in the midstream. There was a significant difference in average velocity between the estuary and midstream (P<0.05). Before the flood regulation, the dominant algal taxa were cyanophyta and bacillariophyta, cyanophyta had a higher proportion in both sampling sites. During the flood regulation period, hydrodynamic characteristics and algal community structure were significantly changed, Shannon-Weaver index decreased. After the flood regulation, diatoms were dominant in the midstream, while the proportion of cyanophyta increased gradually in the estuary. The flood regulation changed the environmental conditions. Hydrological and hydrodynamic characteristics in backwater caused by flooding regulation has been changed markedly, which influenced water quality of tributaries; consequently, followed by rapid changes in phytoplankton community. Results indicated the fluctuation of water level caused by flood regulation destroyed the habitat of algae strongly, and then leads to the changes of community structure. It could be deduced that such flood regulation would be helpful to inhibit and delay the formation of algal bloom in the tributaries of Three Gorges Reservoir.
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Received: 16 October 2013
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