Center for Ecological Research, Kyoto University, Shiga 520-2113, Japan.
Water Res. 2022 Aug 15;222:118868. doi: 10.1016/j.watres.2022.118868. Epub 2022 Jul 14.
Clarifying the pattern of relative nitrogen (N)-to-phosphorus (P) requirements for phytoplankton growth is of great significance for eutrophication mitigation and aquatic system management. The relative N-to-P requirement for phytoplankton growth is considered an essential trait determining species dominance within ecosystems and explaining phytoplankton response to nutrient availability. These requirements vary with environmental trophic status, though this variation remains unclear. Here, we evaluated the relative N-to-P requirements under different absolute nutrient levels using previous and current experimental data on eight phytoplankton species (three studied by us and five extrapolated from previous studies). Results showed that relative N-to-P requirements for phytoplankton growth decreased as absolute nutrient levels increased. Thus, N may be crucial for enhancing phytoplankton growth under low nutrient conditions, whereas P may be the primary limiting factor of phytoplankton growth under sufficient nutrient conditions. This result applies to single species as well as species assemblages, which are independent of species shifts occurring along water N:P gradients. The response observed in our large trophic status gradient may help elucidate the relative importance of N and P reductions in mitigating the impact of eutrophication on ecosystems.
阐明浮游植物生长的相对氮（N）-磷（P）需求模式对于减轻富营养化和水生系统管理具有重要意义。浮游植物生长的相对 N-P 需求被认为是决定生态系统中物种优势的重要特征，并解释了浮游植物对养分供应的响应。这些需求随环境营养状态而变化，但这种变化尚不清楚。在这里，我们使用以前和当前关于八种浮游植物物种（我们研究的三种和以前研究中推断的五种）的实验数据，评估了不同绝对养分水平下的相对 N-P 需求。结果表明，浮游植物生长的相对 N-P 需求随着绝对养分水平的增加而降低。因此，在低养分条件下，N 可能对增强浮游植物生长至关重要，而在充足养分条件下，P 可能是浮游植物生长的主要限制因素。这一结果适用于单一物种以及物种组合，而与沿水 N：P 梯度发生的物种变化无关。我们在大营养状态梯度中观察到的响应可能有助于阐明减少 N 和 P 在减轻富营养化对生态系统的影响方面的相对重要性。
