富营养化浅水湖泊浮游植物初级生产力生物光学模型及遥感估算

Phytoplankton primary productivity (PP) is the basis of the structure and function of lake ecosystem food web, which drives biogeochemical cycles of major biogenic elements such as carbon, nitrogen and phosphorus, and the evolution of lake ecosystem. PP also determines the assessment of lake potential fisheries production. Traditionally, lake PP has been measured from ships, but the duration and cost of the shipboard measurements severely restrict their geographic and temporal coverage. Fortunately, for more than a decade, PP bio-optical remote sensing estimation model based on phytoplankton photosynthesis process provides much more reliable quantification of spatial and temporal variability in PP than would be possible by interpolating among the sporadic in situ measurements. Based on the indoor control experiment, the field in situ observation and radiative transfer numerical simulation in Lake Taihu, the goals of this project are to: (1) develop the coupling model between photosynthetic rate and water temperature, light intensity, chlorophyll a concentration and phytoplankton specific absorption coefficient; (2) calibrate and validate the sem-analytical models of chlorophyll a, total suspended matter concentrations and euphotic depth; (3) correct and validate bio-optical remote sensing estimation model of PP; and (4) calculate phytoplankton PP using the valid MODIS data from 2003 to 2015 and expound the temporal-spatial pattern and the response mechanism of phytoplankton PP to ecological factors.

浮游植物初级生产力是湖泊生态系统食物网结构与功能的基础环节, 是碳、氮、磷等生源要素生物地球化学循环，湖泊生态系统的演变,以及湖泊潜在渔业生产量评估的关键表征量。以往初级生产力都是基于船载单点现场测定，耗时耗力，时空尺度上也都是"离散"的。近年来基于浮游植物光合作用过程的初级生产力生物光学遥感反演模型被广泛应用于不同时空尺度初级生产力估算，提供了更准确的初级生产力时空分布。本项目以富营养化浅水湖泊太湖为研究对象，通过室内控制实验、野外原位实验和辐射传输数值模拟，建立浮游植物光合速率与温度、光强、叶绿素a、比吸收系数之间耦合关系模型；构建叶绿素a、悬浮物浓度以及真光层深度半分析反演模型；修正和校验浮游植物初级生产力生物光学遥感反演模型；基于2003-2015年有效MODIS数据和改进后的初级生产力生物光学模型计算浮游植物初级生产力, 阐释初级生产力时空分布格局、与生态因子相互关系及变化规律。

浮游植物初级生产力是湖泊生态系统食物网结构与功能的基础环节, 是碳、氮、磷等生源要素生物地球化学循环，湖泊生态系统的演变,以及湖泊潜在渔业生产量评估的关键表征量。项目通过野外原位观测和室内受控实验，研究了典型浮游植物吸收、比吸收系数等光学特性的光谱特征、季节差异，揭示了温度、细胞粒径和浮游植物色素对浮游植物吸收、比吸收和光合效率的作用机制，为垂向归纳模型（VGPM模型）参数区域化提供了理论支撑；揭示了中国东部地区太阳辐射长时间序列变化特征、季节差异及影响因素；验证和校验了MODIS数据反演太湖水体温度模型和方法，阐明了太湖水温时空变化特征、长期变化趋势及其环境效应；分析了浑浊水体短波红外大气校正方法在太湖的适用性并利用实测遥感反射率数据进行检验，构建了基于邻近植被暗目标的太湖水体MODIS数据大气校正方法并应用于太湖叶绿素a和漫射衰减系数的遥感反演；构建和校验了太湖叶绿素a浓度和漫射衰减系数遥感估算模型，探讨其时空格局及影响因素；通过实测的浮游植物初级生产力校验和验证了遥感反演浮游植物初级生产力的精度和可行性，基于太阳辐射、水温、叶绿素a和漫射衰减系数的计算和遥感反演，利用VGPM模型计算得到2003-2013年逐日浮游植物初级生产力，探讨其时空格局和演化机理。