We investigated Arctic lake phytoplankton response along vertical gradients in the water column during seasonal succession from ice‐covered to open‐water conditions. Two oligotrophic lakes in West Greenland with different dissolved organic carbon (DOC) concentrations were selected. We assessed which factors: (1) promote under‐ice growth of phytoplankton, and (2) trigger shifts in the community structure. Our results suggest that DOC is an important driver of the seasonal distribution of phytoplankton biomass—high DOC exacerbates light limitation under ice resulting in low phytoplankton biomass, but supports phytoplankton growth during the open‐water period when photolytic and biological degradation of organic matter contributes to the pool of available nutrients. Under‐ice phytoplankton biomass in a clear, low DOC lake was as high as during the open‐water period, suggesting the importance of under‐ice processes for lake metabolic balance, also evidenced by persistent oxic conditions in the hypolimnion. Species composition was dynamic, reflecting rapidly changing conditions over the course of the season. Our data suggest that phytoplankton under ice provides seed populations for early spring blooms and that the largest shifts in species composition occur later during the summer, likely as a result of nutrient depletion and intensified grazing pressure. Early spring temperatures in West Greenland have risen rapidly in recent decades, triggering shifts in the timing of lake ice‐out and the onset of stratification; therefore, it is important to understand phytoplankton seasonal dynamics to disentangle the effects of climate‐driven shifts on aquatic biota.

中文翻译：

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在两个不同DOC的北极湖冰和初夏浮游植物动力学下

我们调查了从覆冰到开阔水域的季节演替过程中，北极湖沿水柱垂直梯度的浮游植物响应。选择了西格陵兰的两个贫营养湖，它们具有不同的溶解有机碳（DOC）浓度。我们评估了哪些因素：（1）促进浮游植物的冰下生长，以及（2）引发群落结构的转变。我们的结果表明，DOC是浮游植物生物量季节性分布的重要驱动力-高DOC加剧了冰下的光限制，导致浮游植物生物量较低，但在开放水域（光解和有机物的生物降解有助于增加浮游植物的生长）时，它支持浮游植物的生长。可用养分池。冰层下浮游生物的生物量清晰，DOC低的湖泊与开放水域的湖泊一样高，这表明冰下过程对于湖泊代谢平衡的重要性，这也由次层水体中的持续有氧条件证明。物种组成是动态的，反映了整个季节中条件的快速变化。我们的数据表明，冰层下的浮游植物为早春开花提供了种子种群，物种组成的最大变化发生在夏季的晚些时候，这可能是营养物质的消耗和放牧压力的增加所致。近几十年来，西格陵兰岛的早春温度迅速上升，引发了湖泊结冰时间和分层现象的转变。所以，