全球边缘海浮游植物趋势变化异同性研究

The nonlinear responses of phytoplankton to physical environment factors can enlarge the weak environmental disturbance, which makes phytoplankton a good indicator for the response of ocean to climate change. Previous studies have shown that global phytoplankton had a descending trend under climate warming overall. However, based on the results from our previous studies and analysis of recent literatures, we suppose that the changing trend of phytoplankton in marginal sea may have different from it of open ocean, or even opposition. Moreover, the change trend of each phytoplankton group also may have different from it of the bulk phytoplankton, and significant difference may exist among marginal seas. Current, the long-term changes of phytoplankton in global scale and its response to the coupled variations of ecological environment factors are still unknown under the background of climate change. Therefore, this project will construct a 20yrs time-series database of phytoplankton and its environment factors using the multiple satellite data, and analyze the temporal variability of the phytoplankton and its geographic variability from the view of long-term change. Then, the project will identify the coupled controls by the variations of multiple environment factors, and reveal the response of phytoplankton in marginal seas to climate oscillations. This project has not only important scientific significance, but also face to the demand of the country. Currently, China has fulfilled the monitoring of ecological environment of global terrestrial plants under the framework of the Global Earth Observation System of Systems (GEOSS), but it is still blank for the monitoring of marine ecological environment in global scale. Thus, the outcomes of this project will contribute to the establishment of the GEOSS by China directly.

浮游植物变化能放大微弱的物理环境扰动，是表征气候变化对海洋影响的良好指标。现有研究表明，气候变暖下全球浮游植物总体呈下降趋势。然而，申请者根据前期工作及最新国际现状分析，认为边缘海浮游植物趋势变化可能与大洋不同，甚至反相，且不同浮游植物群落的趋势变化亦可能与总生物量不同，各边缘海系统间存在显著差异。目前，对于边缘海浮游植物的趋势变化及其对多环境因子耦合变化的响应，仍缺乏全球尺度的系统认识。为此，项目拟构建全球边缘海浮游植物及生态环境因子的20年序列遥感数据集，从趋势变化协同性的角度，阐明各边缘海浮游植物的趋势变化和区域差异，厘清多因子变化的耦合调控机制，揭示边缘海浮游植物对短期气候振荡的响应。项目不仅具有重要科学意义，且面向国家需求。当前我国在全球综合地球观测系统(GEOSS)框架下进行了植被等陆地生态环境的全球遥感监测，但尚未实现海洋生态环境全球监测，项目可直接服务于我国GEOSS建设。

项目针对全球尺度边缘海浮游植物变化缺乏系统性认识的问题，利用多源、长时序卫星遥感数据，从趋势变化协同性的角度，系统研究全球各边缘海系统浮游植物的变动和区域差异，厘清多因子变化的耦合调控机制，并揭示边缘海浮游植物对全球变化的响应。项目研究提出了针对全球边缘海浮游植物研究的边界划分方法，以及基于距平的多星融合方法，构建了适用于趋势性判断的全球边缘海浮游植物及生态环境因子的长时间序列遥感数据集。. 项目研究获得了全球所有边缘海浮游植物的变化趋势认识，在此基础上，根据海域特点，归纳分析了三大类海区（即封闭/半封闭与河流影响边缘海、极地与高纬边缘海以及上升流与边界流影响边缘海）浮游植物变化特征及其影响机制。研究表明，近20年全球边缘海浮游植物叶绿素浓度总体呈上升趋势，这与寡营养的开阔大洋变化趋势相反；其中30个边缘海发生了显著的叶绿素增加，没有任何区域出现显著的下降信号。全球边缘海叶绿素浓度平均上升速率为0.65%/年，某些边缘海可达3%/年~4%/年。封闭/半封闭与河流影响边缘海的叶绿素浓度平均上升速率分别为0.55%/年和0.80%/年。极地边缘海叶绿素浓度平均上升速率为0.71%/年；七个高纬边缘海区中，有五个呈现了显著的叶绿素浓度上升趋势；在极地和高纬边缘海，光合有效辐射增强与水温上升对浮游植物生长具有促进作用。上升流边缘海区域叶绿素浓度的变化幅度相对较小，整体平均上升速率为0.44%/年；边界流影响边缘海区域为整体上升速率最大，平均上升速率为0.86%/年。. 总结来说，项目研究系统阐明了全球45个边缘海浮游植物的近20年变化趋势，在本研究基础上，可进一步评估边缘海浮游植物变化对全球碳循环影响，服务碳中和战略。项目共资助发表了28篇学术论文，出版专著1部，相关成果获浙江省科学技术奖一等奖和海洋科学技术奖一等奖。