表征赤潮水体太阳激发的叶绿素荧光高度的波段优化——归一化荧光高度法

采用现场实测和室内培养两种方式测定了甲藻、赤潮异弯藻、叉角藻、海洋蓝绿藻等赤潮和新月菱形藻、叉鞭金藻、塔胞藻、扁藻和小球藻等非赤潮藻类光谱曲线.采用度量太阳激发的叶绿素荧光峰高度的归一化荧光高度法,建立了不同藻类归一化荧光高度与叶绿素浓度的关系.荧光高度计算方法是将红光波段的反射率最大值(R_maxred)和R₆₈₅分别归一化到560 nm处的R₅₆₀和560 nm附近整个光谱曲线的最大值R_{560 max}上或675 nm处的R₆₇₅和675 nm附近的最小值R_675mini上.结果表明,不同藻类的R_maxred/R₅₆₀max和R_maxred/R_675mini与叶绿素a的相关系数分别比R₆₈₅/R₅₆₀和R₆₈₅/R₆₇₅与叶绿素的相关系数高,但在海洋现场测量中由于近岸二类水体其他水色组分以及大气校正误差的影响,R_maxred/R_675mini和R₆₈₅/R₆₇₅更适合于实测的叶绿素浓度估算.采用三种统计回归方程建立了不同藻类归一化荧光高度与叶绿素浓度关系,除个别藻种外,大部分的相关系数在0.9以上,其中FLH=a+(Chla)b回归方程得到的相关系数优于其他两种方法,相关系数大于0.93,这表明藻类水体的荧光特性和叶绿素浓度之间的普遍关系是非线性的.

The optimized spectral bands ratio for the relation of sun-induced chlorophyll fluorescence height with high chlorophyll a concentration of algal bloom waters

To investigate the relation of sun-induced fluorescence peak near 700 nm to chlorophyll a concentration,data set of the reflectance spectra of red tide species such as Gymnodinium spp.,Heterosigma akashiwo,Ceratium furca and other algae such as Nitzschia closterium,Dicrateria zhanjiangensis Hu.Platymonas sp.,Chlorococcum sp.,Platymonas helgolandica var tsingtaoensis,Chlorella sp.getting from in situ and culture was measured.Because the magnitude and position of different algae's fluorescence peak vary with the increasing of chlorophyll a concentration.Reflectance at maximum red and 685 nm of spectrum was normalized to R_(560,max),R_(675,mini) and R_(560),R_(675)separately.The results show that along with algae's variation,R_(red,max)/R_(560,max) and R_(red,max)/R_(675,mini)have better correlations with chlorophyll a concentration than R_(685)/R_(560) and R_(685)/R_(675),however,with the consideration of complex components of Case 2 water and atmosphere correction error,R_(red,max)/R_(675,mini) and R_(685)/R_(675) are more suitable for retrieval of chlorophyll a concentration in coastal water.Simultaneously three regression equations were put into use with all the regression coefficients more than 0.9 except Heterosigma akashiwo.The R coefficient of regression equation of FLH=a+(Chl a)~(b) is better than the others' with R more than 0.93,which shows that the relationship between fluorescence characteristics of algae's water and chlorophyll a concentration is nonlinear.