Cyanobacteria bloom detection and monitoring from satellite observations in the coastal region of Finland

Abstract

MODIS-Terra和MERIS数据被用于芬兰湾蓝藻水华的监测,并对两者的性能进行了比较.研究结果表明:MODIS-Terra波段设置主要针对一类大洋水体,缺乏预警藻蓝素的有效波段;MERIS传感器设置了620nm和665nm波段,基本对应藻蓝素的吸收峰(630nm)和反射峰(650nm),具有蓝藻水华探测的潜力,但在藻华未成型之前,海岸带水体不同优势藻类具有相似的叶绿素特征,较难辨别蓝藻水华.总的来说,MODIS和MERIS数据比较困难实现蓝藻水华初期预警,但可以有效监测已成型的蓝藻水华.这一方法可以用于中国太湖或者海岸带水体藻华探测和监测研究.;This study investigates and analyses the possibility of cyanobacteria bloom detection as a case study in the Gulf of Finlandand southern Finish lakes. The results show that MODIS data are difficult to be used in cyanobacteria bloom early warning. The mainreason is that MODIS data are more suitable for CASE I waters as there are five bands in the spectral region of 400-550nm. However,for CASE II waters (estuary, coastal, and lakes), the maxima of reflectance spectra are shifting towards longer wavelengths withincreasing turbidity or increasing amount of CDOM. This suggests that the reflectance maximum in coastal waters often occurs in thespectral range of 550-670nm where MODIS data do not have any spectral bands. In contrast, MERIS data have three bands of 560,620, and 665nm at the spectral region of 550-670nm. The two bands at 620nm and 665nm are potentially important bands ofdetecting cyanobacteria bloom of the coastal waters (and/or lakes). The reason is that there are the phycocyanin absorption near630nm and a reflectance peak near 650nm. In fact, MODIS and MERIS data are unlikely applicable to warn potentially cyanobacteriabloom in its early stages, but able to monitor the already formed blooms. This methodology of satellite-based observations can beapplied to detection and monitoring of cyanobacteria bloom in Lake Taihu and coastal regions of China.