1. Zooplankton can spend winter actively under the ice cover of lakes. However, dietary resources under lake ice are both quantitatively and qualitatively limited, and feeding might not be energetically rewarding for most zooplankton species. Many zooplankters are expected to fast throughout the winter, exhausting their previously accumulated fat storage. We hypothesised that only a fraction of the actively overwintering zooplankton contributes to an active food web under lake ice, leading to few trophic linkages within the planktonic community.
2. Zooplankton habitats and feeding were investigated under the ice of Lake Onego. Zooplankton habitats and migrations were studied by coupling zooplankton sampling around the clock to measurements of particle movement using an acoustic Doppler current profiler. Secondly, fatty acid‐specific stable isotope compositions were used to determine whether and which zooplankton fatty acids ultimately came from the assimilation of under‐ice seston.
3. The algal biomass was low under ice and mostly dominated by large diatoms. Copepods dominated the zooplankton community. Species present as late copepodite and adult instars were confined to the deeper layers, while nauplii occupied the surface layer. Diel vertical migration by Cyclops was the most tangible observation of persistent feeding under the ice. Previously accumulated fat storage represented most of zooplankton fatty acids, with few, yet detectable, fatty acids recently acquired by feeding under the ice.
4. Although some zooplankton taxa maintained feeding activity under the ice of Lake Onego, the food source available beneath the ice was not sufficiently rewarding to leave an isotopic imprint upon the dominant fatty acids of bulk zooplankton. The seston fatty acids that were passed on to zooplankton from feeding under ice were not provided by diatoms, although they made up most of the phytoplankton biovolume. Instead, the zooplankton food web was supported by mixotrophic phytoplankton (i.e. cryptophytes and chrysophytes) that represented <5% of the under‐ice biovolume. Consequently, the planktonic food web under the ice of Lake Onego had few trophic linkages, and thereby low connectance.
5. Environmental conditions under the ice of Lake Onego do not depart significantly from those observed in lakes of similar latitudes. Therefore, low connectance food webs could be relatively common under ice for lakes above 60° latitude. Our methodological approach is applicable to other lakes and could thus disclose the variability of under‐ice food webs. This would provide a much more complete picture of annual dynamics of food webs in lakes that ice over.

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禁食或喂食：湖冰下的浮游食物网

1. 浮游动物可以在湖泊的冰盖下积极度过冬季。但是，湖冰下的饮食资源在数量和质量上都受到限制，对于大多数浮游动物而言，觅食可能不会带来积极的回报。预计许多浮游动物会在整个冬季禁食，耗尽其先前积累的脂肪。我们假设，在越冬的浮游动物中，只有一小部分在湖冰下促进了活跃的食物网，从而导致浮游生物体内的营养联系很少。
2. 在Onego湖的冰层下调查了浮游动物的栖息地和摄食。浮游动物的栖息地和迁徙是通过使用声多普勒电流剖面仪将昼夜浮游动物采样与粒子运动的测量耦合来进行的。其次，使用脂肪酸特定的稳定同位素组成来确定浮游动物脂肪酸是否以及最终由浮冰下的同化物吸收。
3. 在冰下，藻类生物量较低，且主要由大型硅藻主导。pe足类在浮游动物群落中占主导地位。以晚足足类和成年幼虫存在的物种被限制在较深的层中，而无节幼体则占据了表层。独眼巨人进行的Diel垂直迁移是冰下持续觅食的最明显观察。以前积累的脂肪储存代表了浮游动物的大部分脂肪酸，而最近在冰下觅食获得的脂肪酸却很少，但可检测到。
4. 尽管一些浮游动物类群在奥尼戈湖的冰下维持着觅食活动，但冰下可用的食物来源却不足以使同位素标记留在浮游动物的主要脂肪酸上。尽管硅藻构成了浮游植物生物量的绝大部分，但它们在冰下摄食后传递给浮游动物的脂肪酸并不由硅藻提供。取而代之的是，浮游动物的食物网是由混合营养型浮游植物（即隐生植物和温藻）支撑的，它们占冰下生物量的<5％。因此，在Onego湖冰层下的浮游食物网几乎没有营养联系，因此连通性很低。
5. 在Onego湖冰层下的环境条件与在类似纬度的湖泊中观察到的环境条件没有明显不同。因此，对于海拔高于60°的湖泊，低连通性食物网在冰下可能相对常见。我们的方法论方法适用于其他湖泊，因此可以揭示冰下食物网的可变性。这样可以更全面地了解冰层湖泊中食物网的年度动态。