| Chlorophyll a was an important component of algal cells,the chlorophyll a concentration was evaluated as a predictor of phytoplankton biomass.According to the continuous monitoring data of water quality and the analysis of meteorological data of seven monitoring sections in the estuaries of South Taihu Lake from 2008 to 2014,the spatio-temporal distribution characteristics of chlorophyll a concentration in the South Taihu Lake and the correlation analysis between the chlorophyll a,meteorological factors and major environmental factors were investigated.The influencing factors of chlorophyll a concentration in different time and space were discovered by using stepwise regression analysis.The results are summarized as following:(1)During 2008-2014,the average chlorophyll a concentration in the estuaries of South Taihu Lake was 11.61-16.82 ?g/L,an obvious "W" trend of peak valley alternation.It changed obviously with seasons,which were generally high in summer and autumn,but was low in winter and spring.The average chlorophyll a concentration at southwest of Taihu Lake(Jiapu,Hexi,Xintang and Yangjiapu)was higher than that at south of Taihu Lake(Xiaomeikou,Xingang and Daqian).(2)The chlorophyll a concentration was positively correlated with mean temperature,maximum temperature,minimum temperature and sunshine hours.The correlation coefficients between chlorophyll a and meteorological factors were 0.242-0.488.(3)The spatial-temporal characteristics of the main environmental factors in the seven monitoring sections of in the estuaries of South Taihu Lake were obvious during 2008-2014.The average annual water temperature was 17.1 to 18.2 ?.The highest water temperature was 27.7 ? in summer,and the lowest was 6.2 ? in winter.The annual average p H value was from 7.75 to 7.91,which belonged to weak alkaline water.The annual average dissolved oxygen was 8.02 to 8.25 mg/L,which was highest in winter and lowest in summer.The annual average p H value and dissolved oxygen in the south of Taihu Lake(xiaomeikou,Xingang and Daqian)were higher than those in the south of Taihu Lake(Jiapu,Hexi,Xintang and Yangjiapu).The annual average value of ammonia nitrogen concentration was 0.315 to 0.482 mg/L,total phosphorus concentration was 0.121 to 0.132 mg/L.The annual average value of total nitrogen content was 1.94 to 2.29 mg/L.The annual average value of permanganate index is 4.43 to 4.84.The concentration of ammonia nitrogen and total nitrogen has decreased significantly,the water quality has improved,phosphorus was the limiting factor for the growth of cyanobacterial.The annual average of ammonia nitrogen,total phosphorus,total nitrogen and permanganate index in the south of Taihu Lake were lower than those in the south of Taihu Lake(Jiapu,Hexi,Xintang and Yangjiapu).(4)Significantly positive correlations were found between chlorophyll a concentration and water temperature,total phosphorus and permanganate index.Significantly positive correlations were found between chlorophyll a concentration and dissolved oxygen,total nitrogen,total nitrogen/total phosphorus and ammonia.The correlation coefficients between chlorophyll a and environmental factors were 0.016-0.389.The correlation coefficients were low,which indicated that the change of chlorophyll a concentration in the estuaries of South Taihu Lake was affected by many factors.(5)Stepwise regression analysis showed that the time impact factors of chlorophyll a were water temperature,permanganate index,ammonia nitrogen,total nitrogen/total phosphorus,dissolved oxygen,total nitrogen,p H and total phosphorus.The spatial impact factors were water temperature,permanganate index,dissolved oxygen,p H,total nitrogen/total phosphorus,ammonia nitrogen and total phosphorus.Spatial-temporal impact factors of chlorophyll a were different from part to part.The main impact factors were water temperature,permanganate index,dissolved oxygen,total phosphorus and total nitrogen. |
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