Department of Geography and Environmental Science & School of Agriculture, Policy and Development, University of Reading, Whiteknights, Reading, RG6 6AB, UK.
ISME J. 2018 Jun;12(6):1457-1472. doi: 10.1038/s41396-018-0054-8. Epub 2018 Feb 12.
Energy value of phytoplankton regulates the growth of higher trophic species, affecting the tropic balance and sustainability of marine food webs. Therefore, developing our capability to estimate and monitor, on a global scale, the concentrations of macromolecules that determine phytoplankton energy value, would be invaluable. Reported here are the first estimates of carbohydrate, protein, lipid, and overall energy value of phytoplankton in the world oceans, using ocean-colour data from satellites. The estimates are based on a novel bio-optical method that utilises satellite-derived bio-optical fingerprints of living phytoplankton combined with allometric relationships between phytoplankton cells and cellular macromolecular contents. The annually averaged phytoplankton energy value, per cubic metre of sub-surface ocean, varied from less than 0.1 kJ in subtropical gyres, to 0.5-1.0 kJ in parts of the equatorial, northern and southern latitudes, and rising to >10 kJ in certain coastal and optically complex waters. The annually averaged global stocks of carbohydrate, protein and lipid were 0.044, 0.17 and 0.108 gigatonnes, respectively, with monthly stocks highest in September and lowest in June, over 1997-2013. The fractional contributions of phytoplankton size classes e.g., picoplankton, nanoplankton and microplankton to surface concentrations and global stocks of macromolecules varied considerably across marine biomes classified as Longhurst provinces. Among these provinces, the highest annually averaged surface concentrations of carbohydrate, protein, and lipid were in North-East Atlantic Coastal Shelves, whereas, the lowest concentration of carbohydrate or lipid were in North Atlantic Tropical Gyral, and that of protein was in North Pacific Subtropical Gyre West. The regional accuracy of the estimates and their sensitivity to satellite inputs are quantified from the bio-optical model, which show promise for possible operational monitoring of phytoplankton energy value from satellite ocean colour. Adequate in situ measurements of macromolecules and improved retrievals of inherent optical properties from high-resolution satellite images, would be required to validate these estimates at local sites, and to further improve their accuracy in the world oceans.
浮游植物的能量值调节着更高营养级物种的生长，影响着海洋食物网的营养平衡和可持续性。因此，开发一种在全球范围内估计和监测决定浮游植物能量值的宏量分子浓度的能力将是非常宝贵的。本文报告了利用卫星海洋颜色数据首次对全球海洋浮游植物的碳水化合物、蛋白质、脂质和总能量值的估算。这些估算基于一种新的生物光学方法，该方法利用了卫星衍生的活浮游植物生物光学指纹图谱和浮游植物细胞与细胞宏量分子含量之间的比例关系。每年每立方米次表层海洋的浮游植物能量值从亚热带环流中的小于 0.1 千焦变化到赤道、北部和南部纬度部分的 0.5-1.0 千焦，并在某些沿海和光复杂水域上升到>10 千焦。每年每立方米次表层海洋的碳水化合物、蛋白质和脂质的全球储量分别为 0.044、0.17 和 0.108 千兆吨，在 1997-2013 年间，每月储量最高在 9 月，最低在 6 月。浮游植物大小类别的分数贡献，例如微微型浮游生物、纳米浮游生物和微型浮游生物，对海洋生物群系（分类为 Longhurst 省份）表面浓度和全球宏量分子储量的变化有很大影响。在这些省份中，碳水化合物、蛋白质和脂质的年平均表面浓度最高的是东北大西洋沿海大陆架，而在北大西洋热带环流中的碳水化合物或脂质浓度最低，在北太平洋亚热带环流西部的蛋白质浓度最低。生物光学模型量化了这些估算的区域准确性及其对卫星输入的敏感性，这表明从卫星海洋颜色监测浮游植物能量值具有潜在的操作可行性。需要对宏量分子进行充分的现场测量，并从高分辨率卫星图像中改进固有光学性质的反演，以便在当地站点验证这些估算，并进一步提高其在世界海洋中的准确性。
