Phytoplankton Photochemical Budgets: Translating Optical Measurements to Productivity

利用质谱、可变荧光和光吸收对浮游植物光合作用的详细测量已经检测到光饱和条件下的显著能量损失过程。生产力的能量损失被初步确定为围绕光系统II的循环电子流。这一现象改变了碳同化、氧释放和光系统II的量子产率之间的关系，使得基于荧光的初级生产力（碳基）估计不准确。这项研究将描述特定的环境条件（波动的光照和营养物质的可用性），预计会影响这一过程的表达。实验将使用O-18质谱、C-14碳酸氢盐同化、可变荧光和光吸收测量对六种分类学上不同的微藻物种进行，以测量a）通过光系统II的总电子流，B）真实的总氧释放，c）光依赖性氧吸收，和d）碳同化。这些数据将用于划分光吸收，光化学活性，非循环电子传输和电子传输到碳生产之间的能量流，从而确定传统方法所隐藏的能量耗散过程的大小和环境控制。该项目对使用生物海洋学中使用的生物光学和荧光方法远程和实地评估初级生产力具有重要意义。

Detailed measurements of phytoplankton photosynthesis using mass spectrometry, variable fluorescence, and light absorption have detected a significant energy loss process under light saturation conditions. The energy loss to productivity is tentatively identified as cyclic electron flow around photosystem II. This phenomenon alters the relationship between the quantum yields of carbon assimilation, oxygen evolution, and photosystem II, making fluorescence-based estimates of primary productivity (carbon-based) inaccurate. The research willcharacterize specific environmental conditions (fluctuating light and nutrient availability) that are expected to affect the expression of this process. Experiments will be conducted on six taxonomically diverse microalgal species using O-18 mass spectrometry, C-14 bicarbonate assimilation, variable fluorescence, and light absorption measurements to measure a) total electron flow through photosystem II, b) true gross oxygen evolution, c) light dependent oxygenuptake, and d) carbon assimilation. These data will be used to partition the energy flow between light absorption, photochemical activity, non-cyclic electron transport, and electron transport to carbon production, thereby identifying the magnitude and environmental control of energy dissipation processes that are hidden from conventional methods. The project has a significant bearing on the use of bio-optical and fluorescence methods used in Biological Oceanography to assess primary productivity remotely and in situ.