Climate‐driven decreases in ice‐cover duration have the potential to impact lake ecosystems, yet we have only partial understanding of the effects of winter conditions on physical, chemical, and biological properties of lakes. We used 39 years of monitoring data to examine under‐ice changes in nutrients, oxygen, and phytoplankton in a shallow drinking‐water reservoir. Two phases of winter were identified. Early winter was characterized by declining oxygen. In this phase, there were increases in specific conductance and concentrations of ammonium (‐N) and soluble reactive phosphorus (SRP). In the month prior to ice off these trends reversed themselves and phytoplankton began to increase. Specific conductance declined as meltwater entered the lake. Nutrients (SRP and ‐N) declined, concurrent with increases in chlorophyll a and oxygen during late winter. This work demonstrates that chemical and biotic changes through winter are highly time dependent and differ between early and late winter phases. The late winter phase is often unstudied because of unsafe ice conditions, but here, the “spring” bloom commonly occurs in late winter under ice. The phases of winter, which are likely driven by changes in light, must be considered as we work to understand how diverse lakes will respond to declining periods of ice cover, and what drives differences in the spring ecology of diverse ice‐covered lakes.

中文翻译：

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冬季分两个阶段：冬季浅层水库的长期研究

由气候驱动的覆冰持续时间的减少可能会影响湖泊生态系统，但我们对冬季条件对湖泊的物理，化学和生物特性的影响只有部分了解。我们使用了39年的监测数据，来研究浅层饮用水水库中冰层下养分，氧气和浮游植物的变化。确定了冬季的两个阶段。初冬以氧气下降为特征。在此阶段，铵（-N）和可溶性反应性磷（SRP）的比电导和浓度都有所增加。在结冰之前的一个月中，这些趋势逆转了自己，浮游植物开始增加。当融水进入湖泊时，电导率下降。营养物质（SRP和‐N）下降，同时在冬季后期叶绿素a和氧气增加。这项工作表明，整个冬季的化学和生物变化与时间高度相关，并且在冬季的早期和晚期之间存在差异。由于不安全的冰雪条件，通常无法研究冬末阶段，但是在这里，“春季”开花通常发生在冰末的冬末。在我们努力了解多样化的湖泊将如何应对冰盖减少的时期以及导致不同的冰雪覆盖的湖泊的春季生态变化的因素时，必须考虑可能由光的变化驱动的冬季。