| Due to the joint action of multiple factors such as the construction and operation of large-scale water conservancy projects in the upper reaches,climate change and human activities,the connection degree of river and lake water systems on both sides of the Yangtze River has been seriously affected,resulting in the gradual reduction of river and lake biodiversity,Therefore,it is very important to study the regulation and restoration measures of hydrological connectivity and biodiversity,11 research points were selected in baidang Lake Basin of Tongjiang lake.The hydrological connectivity evaluation index system was constructed through the comprehensive index method,the hydrological connectivity index in different water periods was calculated,the structural characteristics of plankton community were explored,and the relationship between hydrological connectivity and plankton community was analyzed.The results show that:(1)the water cultural connectivity of baidang lake is good as a whole and fluctuates within the year,which is manifested in wet season(IC = 0.3007)> normal season(IC= 0.2887)> dry season(IC = 0.2881);(2)The plankton community structure in baidang Lake Basin has obvious characteristics of seasonal change.There are 13 dominant species of phytoplankton,3 species of Cyanophyta,5 species of diatom,4 species of Chlorophyta and 1 species of Cryptophyta.The normal water level biomass is higher than that of high water level and low water level,and the abundance of high water area is higher than that of usual water level and low water level.The biomass and density of phytoplankton are low and widely distributed in the low water period,and there are golden algae populations.The watershed is mainly green algae diatom cyanobacteria;The dominant species of zooplankton are mainly polyarthra trigla,Keratella.Cochlearis Gosse,Brachionus budapestiensis,Asplanchna SP and nauplius.Rotifers and cladocerans are mainly distributed in baidang Lake Basin;(3)The plankton diversity index of baidang Lake Basin shows obvious spatial variation characteristics.Among them,the highest values of Shannon Wiener index and Margalef index are mainly distributed in the tributary Luochang river section,the lowest value is in the tributary Yangshi river section,and the highest value of Pielou index is mainly distributed in the inlet of baidang Lake and the upper reaches of Luochang river;(4)The correlation analysis between hydrological connectivity index and plankton community characteristics shows that the hydrological connectivity index has a very significant positive correlation with phytoplankton density and Shannon Wiener index,a significant negative correlation with phytoplankton biomass,and a significant correlation with Pielou index and Margalef index;The hydrological connectivity index has a significant positive correlation with the abundance of zooplankton,a very significant positive correlation with Shannon Wiener index,and a significant negative correlation with Pielou index.On this basis,a hydrological connectivity regulation scheme for the stability of plankton community in the water system of baidang lake is proposed,which provides scientific theoretical support for the improvement of hydrological connectivity in Tongling section of the Yangtze River,and scientific data support for the restoration of ecological function improvement and biodiversity maintenance of Baidang Lake Basin. |
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