The elemental stoichiometry of particulate organic carbon (C), nitrogen (N), and phosphorus (P) connects the C fluxes of biological production to the availability of the limiting nutrients in the ocean. It also influences the marine food-web by modulating zooplankton’s feeding behavior and organic matter decomposition by bacteria. Despite its importance, there is a general paucity of information on how the global C:N:P ratio evolves seasonally and interannually, and large parts of the global ocean remain devoid of observational data. Here, we present a new method combining satellite ocean-color data with a cellular-trait-based model to characterize the spatio-temporal variability of the phytoplankton stoichiometry in the surface mixed layer of the ocean. This new method is demonstrated specifically for the C:P ratio. The approach was applied to phytoplankton growth rates and chlorophyll-to-carbon ratios derived from MODIS-Aqua and maps of temperature-dependent nutrient limitation to generate global and seasonal maps of upper-ocean phytoplankton C:P. Taking it a step further, we determined the C:P of the bulk particulate organic matter, using MODIS-Aqua estimates of particulate organic carbon and phytoplankton biomass. Our results are within 95% confidence interval of available data for both horizontal distributions and time series, indicating our new method’s viability in accurately quantifying seasonally resolved global ocean bulk C:P. We anticipate the new hyperspectral capabilities of the NASA PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) mission will facilitate the determination of phytoplankton stoichiometry for different size classes and further enhance the predictability of marine-ecosystem stoichiometry from space.

中文翻译：

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从卫星遥感确定上层海洋生态系统化学计量的时空变异性

颗粒有机碳 (C)、氮 (N) 和磷 (P) 的元素化学计量将生物生产的 C 通量与海洋中有限营养物质的可用性联系起来。它还通过调节浮游动物的摄食行为和细菌对有机物的分解来影响海洋食物网。尽管它很重要，但关于全球 C:N:P 比率如何季节性和年际演变的信息普遍缺乏，而且全球海洋的大部分地区仍然缺乏观测数据。在这里，我们提出了一种将卫星海洋颜色数据与基于细胞特征的模型相结合的新方法，以表征海洋表面混合层中浮游植物化学计量的时空变异性。这种新方法专门针对 C:P 比率进行了演示。该方法应用于浮游植物增长率和源自 MODIS-Aqua 的叶绿素碳比和温度依赖性养分限制图，以生成上层海洋浮游植物 C:P 的全球和季节性图。更进一步，我们使用 MODIS-Aqua 对颗粒有机碳和浮游植物生物量的估计，确定了大量颗粒有机物质的 C:P。我们的结果在水平分布和时间序列的可用数据的 95% 置信区间内，表明我们的新方法在准确量化季节性解析的全球海洋散装 C:P 方面的可行性。我们预计 NASA PACE（浮游生物、气溶胶、云、