Research On Temporal And Spatial Variation Characteristics Of Algal Blooms In Chaohu Lake Based On Multi-source Remote Sensing Data

With the rapid increasement in population and the expansion of urbanization,the pollutant load capacity of inland lakes has gradually decreased,and the self-recovery function has gradually weakened as the discharge of domestic and industrial wastewater has accumulated.Eutrophication directly leads to the emergence of cyanobacteria blooms,which in turn affects the normal production and life of human beings.Cyanobacteria blooms are often distributed in a large region of lakes,while traditional methods have certain limitations.The rise of satellite remote sensing technology is able to monitor cyanobacteria blooms with large-scale,continuous and dynamic observations,which plays a critical role in monitoring and early warning of cyanobacteria blooms in inland lakes.However,most of the remote sensing extraction of cyanobacteria blooms in water bodies often used a single sensor at present,but the single sensor observation has low spatial resolution or long time return period,which cannot effectively meet the requirements of high temporal and spatial resolution monitoring in inland rivers and lakes.Furthermore,the applicability of extraction method from the single optical remote sensing sensor cannot be selected,while a suitable method is more effective for extracting cyanobacteria blooms based on various remote sensing sensors.In this paper,multi-source satellite remote sensing data are jointly used to monitor the characteristics of cyanobacteria bloom changes in Lake Chaohu by the normalized vegetation index(NDVI),planktonic algae index(FAI)and the chlorophyll reflection peak intensity index(?_chl),respectively according to the characteristics of each sensor.The driving mechanism of cyanobacteria blooms in Lake Chaohu are investigated from combining environmental and meteorological factors as well as the influence of various factors on the distribution and changes of cyanobacteria blooms.The main results are obtained as following:(1)The cyanobacteria blooms in Chaohu Lake are obtained based on FAI,NDVI,and?_chlmethods from Terra/Aqua MODIS,Landsat 8 OLI,and Sentinel-2A/B MSI remote sensing data,respectively and the accuracy is 96.1%,95.6%and 93.8%,respectively.FAI is effective to remove the influence of cloud shadows on the distribution of cyanobacteria blooms,while NDVI and?_chlcan effectively avoid misidentification of water bodies in Chaohu Lake's algae mixed area.(2)The outbreak period of cyanobacteria blooms in Chaohu Lake is from May to November,and the frequency of blooms is the highest in June,July and August.The distribution of cyanobacteria blooms in Chaohu Lake is obvious.The frequency of the annual cyanobacteria blooms accounts for 98.9%in the west,while the frequency of water blooms is38.9%in the eastern half of the lake.(3)The cyanobacteria blooms are rapidly multiplying and breeding anytime and anywhere under suitable weather conditions with the accumulation and storage of nutrients such as nitrogen and phosphorus in the lake.High temperature and rainfall promote the occurrence of cyanobacteria blooms,and the number and area of blooms in summer have increased significantly.The wind affects the growth and drift of cyanobacteria blooms in Lake Chaohu,changes the area and spatial distribution of cyanobacteria blooms,and affects the relative change of the intra-day area of cyanobacteria blooms by 24.61%.