With the ongoing differential disruption of the biogeochemical cycles of major elements that are essential for all life (carbon, nitrogen, and phosphorus), organisms are increasingly faced with a heterogenous supply of these elements in nature. Given that photosynthetic primary producers form the base of aquatic food webs, impacts of changed elemental supply on these organisms are particularly important. One way that phytoplankton cope with the differential availability of nutrients is through physiological changes, resulting in plasticity in macromolecular and elemental biomass composition. Here, we assessed how the green alga Chlamydomonas reinhardtii adjusts its macromolecular (e.g., carbohydrates, lipids, and proteins) and elemental (C, N, and P) biomass pools in response to changes in growth rate and the modification of resources (nutrients and light). We observed that Chlamydomonas exhibits considerable plasticity in elemental composition (e.g., molar ratios ranging from 124 to 971 for C:P, 4.5 to 25.9 for C:N, and 15.1 to 61.2 for N:P) under all tested conditions, pointing to the adaptive potential of Chlamydomonas in a changing environment. Exposure to low light modified the elemental and macromolecular composition of cells differently than limitation by nutrients. These observed differences, with potential consequences for higher trophic levels, included smaller cells, shifts in C:N and C:P ratios (due to proportionally greater N and P contents), and differential allocation of C among macromolecular pools (proportionally more lipids than carbohydrates) with different energetic value. However, substantial pools of N and P remained unaccounted for, especially at fast growth, indicating accumulation of N and P in forms we did not measure.

中文翻译：

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莱茵衣藻（绿藻）的元素和大分子可塑性对资源限制和增长率的响应

随着所有生命所必需的主要元素（碳、氮和磷）的生物地球化学循环的持续差异性破坏，生物体越来越面临着自然界中这些元素的异质供应。鉴于光合初级生产者构成水生食物网的基础，元素供应变化对这些生物体的影响尤为重要。浮游植物应对营养物质可用性差异的一种方式是通过生理变化，从而导致大分子和元素生物量组成的可塑性。在这里，我们评估了绿藻莱茵衣藻如何调整其大分子（例如碳水化合物、脂质和蛋白质）和元素（C、N 和 P）生物量库，以响应生长速率的变化和资源（营养物质和营养物质）的变化。光）。我们观察到，在所有测试条件下，衣藻在元素组成方面表现出相当大的可塑性（例如，C:P 的摩尔比范围为 124 至 971，C:N 的摩尔比范围为 4.5 至 25.9，N:P 的摩尔比范围为 15.1 至 61.2），这表明衣藻在不断变化的环境中的适应潜力。暴露于弱光下对细胞元素和大分子组成的改变与营养物质的限制不同。这些观察到的差异对更高的营养水平具有潜在的影响，包括更小的细胞、C:N 和 C:P 比率的变化（由于 N 和 P 含量成比例地增加）以及 C 在大分子池中的差异分配（脂质比碳水化合物）具有不同的能量值。然而，大量的氮和磷仍然下落不明，特别是在快速生长时，表明氮和磷以我们未测量的形式积累。