Understanding the driving mechanism of phytoplankton dynamics is key to forecasting future changes in the ocean. Here, we report an apparent “trapezoidal” relationship between chlorophyll concentrations (Chl) and surface photosynthetically available radiation (PAR(0)) at the center of the South Pacific Gyre (cSPG) based on 18 years of MODIS Aqua measurements. A comparison of Chl with a photoacclimation model revealed that photoacclimation alone could not explain the temporal dynamics of Chl. Instead, the Chl dynamics were explained by a combination of photoacclimation, nutrient limitation, and the grazing pressure of zooplankton at different times throughout the year. An annual “trapezoidal” spiral relationship between Chl and PAR(0) suggested that the steady state of phytoplankton populations at the cSPG could be influenced by the alternation of co-regulation mechanisms during a year. Because this same pattern occurs in other subtropical gyres, this understanding of the underlying mechanisms not only facilitates simulating and forecasting phytoplankton dynamics but also provides a new perspective on how multiple stressors may impact phytoplankton communities in a warmer climate.

中文翻译：

---

南太平洋环流中心太阳辐射与叶绿素浓度之间的“梯形”关系


了解浮游植物动力学的驱动机制是预测未来海洋变化的关键。在此，我们根据 18 年的 MODIS Aqua 测量报告，南太平洋环流 (cSPG) 中心的叶绿素浓度 (Chl) 与表面光合有效辐射 (PAR(0)) 之间存在明显的“梯形”关系。叶绿素与光驯化模型的比较表明，光驯化本身无法解释叶绿素的时间动态。相反，叶绿素动态是由光驯化、营养限制和一年中不同时间浮游动物的放牧压力共同解释的。 Chl 和 PAR(0) 之间的年度“梯形”螺旋关系表明，cSPG 浮游植物种群的稳态可能受到一年内共同调节机制交替的影响。由于同样的模式也发生在其他亚热带环流中，因此对潜在机制的了解不仅有助于模拟和预测浮游植物动态，而且还提供了关于多种压力源如何影响温暖气候下的浮游植物群落的新视角。