Although climate change has shifted the phenological timing of plankton in lakes, few studies have explicitly addressed the relative contributions of climate change and other factors, including planktivory and nutrient availability. The spring clear‐water phase is a period of marked reduction in algal biomass and increased water transparency observed in many lakes. Here, we quantified the phenological patterns in the start date, maximum date, duration, and magnitude of the clear‐water phase over 38 yr in Lakes Mendota and Monona, and examined the effects of water temperature, total phosphorus, and food web structure (proportion of large‐bodied Daphnia pulicaria and density of invasive Bythotrephes) and interactions between temperature and other predictors on these clear‐water phase metrics. We found that climate and food web structure affected the clear‐water phase, but the effects differed among the metrics. Higher water temperature led to earlier clear‐water phase start dates and maximum dates in both lakes. The proportion of D. pulicaria affected all clear‐water phase metrics in both lakes. When D. pulicaria proportion was higher, the clear‐water phase occurred earlier, lasted longer, and the water was clearer. Moreover, high Bythotrephes density delayed clear‐water phase start dates (both lakes), and decreased clear‐water phase duration (Lake Mendota) in the following year. These results suggest that variation in food web structure changes the full phenological dynamics of the clear‐water phase, while variation in climate condition affects clear‐water phase timing only. Our findings highlight the importance of large‐bodied grazers for managing water quality under climate change.

中文翻译：

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气候和食物网对两个北温带富营养化湖泊春季清水阶段的影响

尽管气候变化改变了湖泊中浮游生物的物候时机，但很少有研究明确指出气候变化和其他因素（包括浮游生物和养分的可获得性）的相对贡献。在许多湖泊中，春季清水阶段是藻类生物量显着减少和水透明度增加的时期。在这里，我们量化了门多塔湖和莫诺纳湖38年以上清水阶段的开始日期，最大日期，持续时间和强度的物候模式，并研究了水温，总磷和食物网结构的影响（大型水蚤的比例和侵袭性双生菌的密度）以及这些清水相指标上温度与其他预测因子之间的相互作用。我们发现，气候和食物网结构影响了清水阶段，但各指标之间的影响有所不同。较高的水温导致两个湖泊的清水阶段开始日期和最大日期更早。D. pulicaria的比例影响了两个湖泊中所有的清水阶段指标。当D. pulicaria比例较高时，清水阶段出现较早，持续时间更长，水更清澈。而且，高比佛陀密度延迟了清水相的开始日期（两个湖泊），并在第二年减少了清水相的持续时间（门多塔湖）。这些结果表明，食物网结构的变化改变了清水相的全部物候动态，而气候条件的变化仅影响清水相的时间。我们的研究结果突出了大型放牧者在气候变化下管理水质的重要性。