Harmful algal blooms (HABs) are common in many eutrophic lakes and frequently associated with nutrient excesses, warm waters, and calm conditions. While HABs can also occur in oligotrophic waterbodies, bloom‐stimulating factors remain elusive for these ecosystems. Here, using a high‐frequency sensor platform supported by hydrodynamic modeling, we document a clearly linked sequence of three hydrodynamic events that immediately preceded each HAB event on Skaneateles Lake, NY during 2018. HABs were first preceded by interactions between internal waves in the thermal structure of the lake with the northern slope of the lakebed. These interactions disturbed sediments resulting in upwelling of nutrient‐rich sediment and possibly cyanobacterial cells into the lower water column. Next, moderate winds stimulated Langmuir circulation which facilitated the transport of material from the lower water column to well‐lit surface waters. Finally, the sequence culminated with a calm wind period, which is often classically associated with surface HAB formation. While individual steps in this sequence occurred independently and repeatedly throughout the year, the complete sequence occurred only eight times, immediately preceding each of the eight documented HABs. We empirically derive thresholds for and timing of the sequence to independently predict HAB occurrence and elevated cyanobacteria levels in the lake. The discovery of this specific and repeated event sequence and the identified thresholds provides the potential for forecasting of HABs days in advance. Ongoing climate change impacts, including increasing water column thermal stratification and changing wind speeds may alter the frequency, timing, and duration of this sequence and consequent HAB formation.

中文翻译：

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一系列天气驱动的水动力事件刺激了寡营养湖泊上有害藻华的形成


有害藻华 (HAB) 在许多富营养化湖泊中很常见，通常与营养过剩、温暖的水域和平静的环境有关。虽然有害藻华也可能出现在寡营养水体中，但这些生态系统中水华刺激因素仍然难以捉摸。在这里，我们使用由水动力模型支持的高频传感器平台，记录了 2018 年纽约州 Skaneateles 湖每次 HAB 事件之前的三个水动力事件的清晰关联的序列。HAB 首先是热气流中内波之间的相互作用。湖床北坡的湖泊结构。这些相互作用扰乱了沉积物，导致营养丰富的沉积物和可能的蓝藻细胞上涌到较低的水体中。接下来，温和的风刺激了朗缪尔环流，有利于物质从较低的水体输送到光线充足的地表水域。最后，这一序列以平静的风期达到高潮，这通常与表面 HAB 的形成有关。虽然该序列中的各个步骤在一年中独立且重复地发生，但完整的序列仅发生八次，紧接在八个记录的 HAB 之前。我们根据经验得出序列的阈值和时间，以独立预测 HAB 的发生和湖中蓝藻水平的升高。这种特定且重复的事件序列的发现以及确定的阈值为提前几天预测 HAB 提供了可能性。持续的气候变化影响，包括水柱热分层的增加和风速的变化，可能会改变该序列的频率、时间和持续时间以及随后的 HAB 形成。