Recent studies have challenged the validity of the Redfield ratio. It is proposed that physical and biogeochemical processes govern the geographical variations in carbon : nitrogen : phosphorus (C : N : P) ratios. However, this proposal remains to be examined through concurrent observations of C : N : P ratios with physical and biogeochemical processes in various marine reservoirs. Here, we sampled the Arabian Sea for its C, N, and P content in organic and inorganic pools during the winter monsoon. We analyzed the role of convective mixing, eddies, and N2 fixation to explain the variation in observed elemental ratios. Convective mixing injected the cold water and enhanced the supply of N and P nutrients in the top layer (surface to 50–75 m) of the northern Arabian Sea. This led to a decrease in the N : P and C : P ratios in the particulate organic matter in the northern region, but C : N : P increased equatorward, averaging 245 : 32 : 1 in the top layer of the Arabian Sea. The variation in the elemental ratios in the top layer is best explained by the changes in water temperature. N2 fixation contributed negligibly to the N : P ratio of the export flux. The substantial decrease in N : P ratios of nutrients in the subsurface waters is most likely caused by the denitrifying conditions in the Arabian Sea. As the processes of convective mixing and eddies are are prevalent oceanic processes, our observations underpin that the interplay of these processes leads to changes in the elemental ratios globally.

中文翻译：

---

冬季对流混合调节海洋 C : N : P 比率


最近的研究对雷德菲尔德比率的有效性提出了质疑。有人提出，物理和生物地球化学过程控制着碳：氮：磷（C：N：P）比率的地理变化。然而，这一建议仍有待通过对各种海洋水库中的物理和生物地球化学过程的 C:N:P 比率的同时观测进行检验。在这里，我们在冬季季风期间对阿拉伯海的有机和无机池中的 C、N 和 P 含量进行了采样。我们分析了对流混合、涡流和氮气固定的作用，以解释观察到的元素比率的变化。对流混合注入了冷水，增强了阿拉伯海北部顶层（表面至 50-75 m）的 N 和 P 养分供应。这导致北部地区颗粒有机物中的N:P和C:P比率下降，但C:N:P向赤道方向增加，在阿拉伯海顶层平均为245:32:1。顶层元素比例的变化最好通过水温的变化来解释。 N2 固定对输出通量的 N:P 比率的贡献可以忽略不计。地下水中营养物质氮磷比的大幅下降很可能是由阿拉伯海的反硝化条件造成的。由于对流混合和涡流过程是普遍存在的海洋过程，我们的观察结果表明这些过程的相互作用导致全球元素比例的变化。