基于海冰介质光谱衰减特性的极地冰藻生物量长期原位测量机理研究

Ice algae biomass is significant to the understanding of the primary production, marine ecosystem, and global carbon cycle, in the polar area. Based on the fact that the spectral attenuation induced by ice algae is closely related to its biomass, this project aims to realize long-term in-situ measurement of the ice algae biomass making use of the spectral attenuation characteristics of the sea ice medium with ice algae embodied inside, by measuring the spectral intensity of solar irradiance at different depth in the sea ice medium. A model for calculating the spectral diffuse attenuation coefficient of the sea ice medium will be established by investigating the relationship between the spectral intensity of solar irradiance and depth. Together with the study of the coupling between the spectral diffuse attenuation coefficient of the sea ice medium and ice algae biomass, an ice algae biomass calculation model will be developed. The long-term in-situ measurement of the solar irradiance profile within the sea ice medium will be accomplished by adopting the fiber spectroscopy technology. To figure out the problem of the significant intensity variation of the solar irradiance at different depth, and the influence of environment temperature and integration time of the spectrometer, a method for accurately measuring the irradiance profile, system correction algorithm and calibration method will be examined. The developed ice algae biomass calculation model will be testified, evaluated and optimized through using the irradiance profile measurement system to measure the spectral distribution within different depths of many artificial ice columns made in the laboratory, each of which has different kind and different concentration of ice algae. This project can provide necessary technical support to the study of the dynamic change in the polar marine ecosystem, global carbon cycle, etc., where long-term time-serial information of the ice algae biomass is required.

冰藻生物量对于极地初级生产力、海洋生态系统、全球碳循环等研究有着重要意义。根据冰藻引起的光谱衰减与其生物量密切相关的特性，本项目拟基于海冰介质（含有冰藻）的光谱衰减特性，通过测量海冰介质内部不同深度太阳辐照度光谱强度，实现冰藻生物量的长期原位测量。通过太阳辐照度光谱强度随深度的变化规律研究，建立海冰介质光谱漫射衰减系数计算模型；结合海冰介质光谱漫射衰减系数与冰藻生物量耦合关系研究，建立冰藻生物量计算模型；基于光纤光谱技术，通过辐照度剖面精确测量方法、系统校正算法和标定方法研究，解决不同深度辐照度强度相差悬殊以及温度和光谱仪积分时间等会对测量产生影响的问题，实现海冰介质内部太阳辐照度剖面的长期原位测量；并采用辐照度剖面测量系统进行实验室冰柱试验，验证评估并优化冰藻生物量计算模型。本项目将为极地海洋生态系统动态变化、全球碳循环等研究所需冰藻生物量长期连续数据提供必要的技术支撑。

冰藻生物量对于极地初级生产力、海洋生态系统、全球碳循环等研究有着重要意义。根据冰藻引起的光谱衰减与其生物量密切相关的特性，本项目基于辐射传输理论和比尔朗伯定律，综合考虑了纯净海冰、冰藻以及有机残渣颗粒物等影响因素，揭示了冰藻生物量与海冰介质光谱漫射衰减系数系数之间的耦合关系，建立了冰藻生物量理论计算模型。基于光纤光谱技术，提出了一种冰内太阳辐照度剖面长期原位测量方法。综合研究了入射光强度、环境温度以及曝光时间变化对光谱仪输出的影响规律。基于此，提出了一种能够使得光谱仪自动适应入射光强度和环境温度变化进行自适应测量的方法。同时提出一种能够校正环境温度和曝光时间变化对光谱仪输出影响的校正算法。结合对比标定方法，能够根据在任意曝光时间（光谱仪线性工作范围内）和温度（-50°~30°C）下的系统输出得到入射到系统的辐照度光谱强度。实验培养了极地环境下三种典型冰藻，并采用它们制作了多个不同浓度梯度的模拟冰柱。研究了冰柱内部辐照度光谱强度随深度的变化关系。并将归一化差异指数法(normalized difference index，NDI)、主成分分析法（principal component analysis，PCA）和归一化差异指数平方法(normalized difference index square，NDI2)应用于数据分析处理和冰藻生物量计算模型的建模和优化。提出了一种较现有方法精度更高的冰藻生物量计算模型。本项目将为极地海洋生态系统动态变化、全球碳循环等研究所需冰藻生物量长期连续数据提供必要的技术支撑。