Laboratory of Photosynthesis, Institute of Microbiology, ASCR (Academy of Sciences of the Czech Republic), Opatovický mlýn, Třeboň, Czech Republic.
PLoS One. 2013;8(3):e58137. doi: 10.1371/journal.pone.0058137. Epub 2013 Mar 13.
Marine phytoplankton account for about 50% of all global net primary productivity (NPP). Active fluorometry, mainly Fast Repetition Rate fluorometry (FRRf), has been advocated as means of providing high resolution estimates of NPP. However, not measuring CO2-fixation directly, FRRf instead provides photosynthetic quantum efficiency estimates from which electron transfer rates (ETR) and ultimately CO2-fixation rates can be derived. Consequently, conversions of ETRs to CO2-fixation requires knowledge of the electron requirement for carbon fixation (Φe,C, ETR/CO2 uptake rate) and its dependence on environmental gradients. Such knowledge is critical for large scale implementation of active fluorescence to better characterise CO2-uptake. Here we examine the variability of experimentally determined Φe,C values in relation to key environmental variables with the aim of developing new working algorithms for the calculation of Φe,C from environmental variables. Coincident FRRf and (14)C-uptake and environmental data from 14 studies covering 12 marine regions were analysed via a meta-analytical, non-parametric, multivariate approach. Combining all studies, Φe,C varied between 1.15 and 54.2 mol e(-) (mol C)(-1) with a mean of 10.9 ± 6.91 mol e(-) mol C)(-1). Although variability of Φe,C was related to environmental gradients at global scales, region-specific analyses provided far improved predictive capability. However, use of regional Φ e,C algorithms requires objective means of defining regions of interest, which remains challenging. Considering individual studies and specific small-scale regions, temperature, nutrient and light availability were correlated with Φ e,C albeit to varying degrees and depending on the study/region and the composition of the extant phytoplankton community. At the level of large biogeographic regions and distinct water masses, Φ e,C was related to nutrient availability, chlorophyll, as well as temperature and/or salinity in most regions, while light availability was also important in Baltic Sea and shelf waters. The novel Φ e,C algorithms provide a major step forward for widespread fluorometry-based NPP estimates and highlight the need for further studying the natural variability of Φe,C to verify and develop algorithms with improved accuracy.
海洋浮游植物约占全球总初级生产力（NPP）的 50%。活性荧光法，主要是快速重复率荧光法（FRRf），已被提倡作为提供 NPP 高分辨率估算的手段。然而，FRRf 并不直接测量 CO2 固定，而是从光合量子效率估算中得出电子转移率（ETR），并最终推导出 CO2 固定率。因此，将 ETR 转换为 CO2 固定需要了解碳固定的电子需求（Φe，C，ETR/CO2 摄取率）及其对环境梯度的依赖性。这种知识对于大规模实施活性荧光以更好地表征 CO2 吸收至关重要。在这里，我们研究了实验确定的 Φe，C 值与关键环境变量的变化关系，目的是从环境变量中开发新的工作算法来计算 Φe，C。通过元分析、非参数、多变量方法分析了来自 12 个海洋区域的 14 项研究的 FRRf 和（14）C 摄取和环境数据。结合所有研究，Φe，C 在 1.15 和 54.2 mol e(-)（mol C）(-1)之间变化，平均值为 10.9 ± 6.91 mol e(-) mol C）(-1)。尽管在全球范围内，Φe，C 的变异性与环境梯度有关，但区域分析提供了更好的预测能力。然而，使用区域 Φe，C 算法需要客观的方法来定义感兴趣的区域，这仍然具有挑战性。考虑到个别研究和特定的小区域，温度、营养和光照可用性与 Φe，C 相关，尽管程度不同，并且取决于研究/区域和现存浮游植物群落的组成。在大生物地理区域和明显水团的水平上，在大多数区域中，Φe，C 与营养可用性、叶绿素以及温度和/或盐度有关，而在波罗的海和大陆架水域，光照可用性也很重要。新的 Φe，C 算法为广泛的荧光法 NPP 估算提供了重要的一步，并强调需要进一步研究 Φe，C 的自然变异性，以验证和开发具有更高准确性的算法。
