Liefer Justin D, Garg Aneri, Fyfe Matthew H, Irwin Andrew J, Benner Ina, Brown Christopher M, Follows Michael J, Omta Anne Willem, Finkel Zoe V
Department of Geography and Environment, Mount Allison University, Sackville, NB, Canada.
Department of Mathematics and Computer Science, Mount Allison University, Sackville, NB, Canada.
Front Microbiol. 2019 Apr 17;10:763. doi: 10.3389/fmicb.2019.00763. eCollection 2019.
Biogeochemical cycles in the ocean are strongly affected by the elemental stoichiometry (C:N:P) of phytoplankton, which largely reflects their macromolecular content. A greater understanding of how this macromolecular content varies among phytoplankton taxa and with resource limitation may strengthen physiological and biogeochemical modeling efforts. We determined the macromolecular basis (protein, carbohydrate, lipid, nucleic acids, pigments) of C:N:P in diatoms and prasinophytes, two globally important phytoplankton taxa, in response to N starvation. Despite their differing cell sizes and evolutionary histories, the relative decline in protein during N starvation was similar in all four species studied and largely determined variations in N content. The accumulation of carbohydrate and lipid dominated the increase in C content and C:N in all species during N starvation, but these processes differed greatly between diatoms and prasinophytes. Diatoms displayed far greater accumulation of carbohydrate with N starvation, possibly due to their greater cell size and storage capacity, resulting in larger increases in C content and C:N. In contrast, the prasinophytes had smaller increases in C and C:N that were largely driven by lipid accumulation. Variation in C:P and N:P was species-specific and mainly determined by residual P pools, which likely represent intracellular storage of inorganic P and accounted for the majority of cellular P in all species throughout N starvation. Our findings indicate that carbohydrate and lipid accumulation may play a key role in determining the environmental and taxonomic variability in phytoplankton C:N. This quantitative assessment of macromolecular and elemental content spanning several marine phytoplankton species can be used to develop physiological models for ecological and biogeochemical applications.
海洋中的生物地球化学循环受到浮游植物元素化学计量比（碳：氮：磷）的强烈影响，这在很大程度上反映了它们的大分子含量。更深入了解这种大分子含量在浮游植物分类群之间以及随资源限制如何变化，可能会加强生理和生物地球化学建模工作。我们确定了硅藻和绿藻这两个全球重要的浮游植物分类群中碳：氮：磷的大分子基础（蛋白质、碳水化合物、脂质、核酸、色素），以响应氮饥饿。尽管它们的细胞大小和进化历史不同，但在所研究的所有四个物种中，氮饥饿期间蛋白质的相对下降是相似的，并且在很大程度上决定了氮含量的变化。在氮饥饿期间，碳水化合物和脂质的积累主导了所有物种中碳含量和碳：氮的增加，但这些过程在硅藻和绿藻之间有很大差异。硅藻在氮饥饿时碳水化合物的积累要多得多，这可能是由于它们更大的细胞大小和储存能力，导致碳含量和碳：氮有更大的增加。相比之下，绿藻中碳和碳：氮的增加较小，主要由脂质积累驱动。碳：磷和氮：磷的变化具有物种特异性，主要由残余磷库决定，残余磷库可能代表无机磷的细胞内储存，并在整个氮饥饿期间占所有物种细胞磷的大部分。我们的研究结果表明，碳水化合物和脂质积累可能在决定浮游植物碳：氮的环境和分类变异性方面发挥关键作用。这种对几种海洋浮游植物物种的大分子和元素含量的定量评估可用于开发用于生态和生物地球化学应用的生理模型。
