Spatio-temporal distribution of cyanobacteria blooms based on satellite imageries in Lake Taihu, China

Of all the cloudless 340 satellite imageries 11 were shot by Landsat MSS/TM/ETM sensor since 1979, 216 by EOS MODIS sensor since 2002, 10 by CEBERS CCD sensor since 2005 and 3 by IRS P6 LISS-3 sensor in 2007. On the basis of the spectral analysis, an applicable model was developed to extract the cyanobacteria bloom information from multi-source remote sensing images. And then, the model was used to acquire cyanobacteria bloom-covered area and its spatial distribution. The result showed that the initial time of cyanobacteria bloom was moved from June or July to March or April at present, three-four months advanced than the normal. The statistics showed that the cyanobacteria bloom occurs most frequently in June or July and the second was in October or November. Additionally, the duration of cyanobacteria bloom is becoming longer and longer and almost over time of March to December at present. The most intensity of cyanobacteria bloom occurred in September and the second was in June. The north of Lake Taihu, including Meiliang Bay and Zhushan Bay, was the initial location of cyanobacteria bloom and also the heavy disaster area, where the cyanobacteria bloom occurred every year since its first time. However, cyanobacteria bloom also occurred along the south bank of Lake Taihu almost every year since 2001, where the cyanobacteria bloom-covered area was becoming larger and larger and the duration time was becoming longer and longer, and which was becoming the earliest location of cyanobacteria bloom. It was noticeable that the cyanobacteria bloom was pervading gradually from the north, the west and the south to the center since 2003, and it sometimes covered almost the whole non-vegetation area. Additionally, there were cyanobacteria blooms occurring at Gonghu Bay since 2005, and it occurred more frequently in 2007.