Inherent optical properties of typical cyanobacteria in eutrophic lakes

Abstract

固有光学特性是水体光学特性的重要内容，掌握富营养化湖泊水体内典型水华蓝藻的固有光学特性，是开展不同水华蓝藻遥感识别的理论基础.利用AC-S吸收衰减仪、BB9后向散射仪，通过实验室纯藻培养，研究微囊藻（Microcystis）、鱼腥藻（Dolichospermum）和束丝藻（Aphanizomenon）3种典型水华蓝藻的固有光学特性，并探讨色素浓度、色素占比以及藻类等效粒径对不同水华蓝藻固有光学特性的影响.结果表明，3种典型水华蓝藻的吸收光谱曲线均具有440、620和675 nm吸收峰，微囊藻620和675 nm的比吸收系数最大，鱼腥藻440 nm处的比吸收系数最大；束丝藻单位色素浓度的散射和后向散射能力最高，鱼腥藻次之，微囊藻最低；固有光学特性影响因子分析表明，色素浓度和藻蓝素占比是影响3种水华蓝藻固有光学特性的主要因素.3种蓝藻的吸收系数、散射系数以及鱼腥藻、束丝藻的后向散射系数均随着色素浓度（叶绿素a或藻蓝素）的增加而增大；当蓝藻中藻蓝素占比增加时，3种蓝藻的单位色素浓度的后向散射系数逐渐下降；而藻细胞粒径与固有光学特性之间并未表现出很好的相关性.因此，3种水华蓝藻单位色素浓度的固有光学特性将为典型水华蓝藻的遥感识别提供重要的理论基础和数据支持.;Inherent optical properties are the important content of the optical properties of the water body. The inherent optical of cyanobacteria provides theoretical basis for remote sensing-based monitoring on cyanobacteria bloom. In this paper, inherent optical properties including absorbing, scattering and backscattering properties were measured for three typical cyanobacteria species in eutrophic lakes of China, cultured by AC-S and BB9 in the laboratory:Microcystis, Dolichospermum and Aphanizomenon. Pigment-specific absorbing, scattering and backscattering coefficients were utilized to represent absorbing and scattering ability. The results showed that all of the three cyanobacteria had the similar absorbing spectrum with the absorbing peaks at 440, 620 and 675 nm. Microcystis showed the highest specific-absorbing coefficient at 620 and 676 nm, while Dolichospermum had the specific-absorbing peak at 440 nm. Aphanizomenon had the strongest scattering and backscattering ability, and Microcystis had the weakest scattering and backscattering ability. The main factors affecting absorbing and scattering properties were the pigment concentration (chlorophyll-a or phycocyanin) and the ratio of phycocyanin and pigment concentration (chlorophyll-a and phycocyanin). The absorbing spectrum and scattering spectrum of these three cyanobacterial rose as the pigment concentration increased. But the specific-backscattering coefficient got down with the increasing ratio of phycocyanin and pigment concentration. It also showed that for these three cyanobacteria there were no obvious correlations between the cyanobacteria particle size and their inherent optical properties.