In fluctuating lake ecosystems, the severity of anthropogenic disturbance is often difficult to assess because the magnitude of natural dynamics rivals or surpasses that of ecosystem alteration due to human impact. Consequently, it is also difficult to evaluate the resilience of these ecosystems' plant and animal communities to that impact. Unfortunately, lake ecosystem response to natural cycles of lake‐level and salinity fluctuation at multi‐annual time scales is poorly understood, due to complex relationships between hydrological dynamics and the local availability or distribution of ecological niches. We present a 1650‐yr‐long paleoecological record from Lake Naivasha in Kenya (East Africa) which traces community assembly and turnover in two prominent groups of benthic invertebrates (chironomids and ostracods) in response to a climate‐driven sequence of 10 major lake‐level fluctuations. Over this time period, lake depth (inferred from sedimentology) fluctuated between ~3 and >35 m, and salinity (inferred from fossil diatom assemblages) varied between ~100 and ~23,500 µS/cm. Prior to ~780 yr ago, the unique community response to salinity was stronger than to lake depth. Around that time the lake transitioned to a more open hydrology, relatively stable freshwater conditions and greater prevalence of macrophyte‐associated benthic habitat, so that community response to variations in lake depth (and surface area) became stronger. Notably, major community restructuring in the course of this transition was not synchronous between the two groups, because it depended on the proliferation of key freshwater species in each group. Our results imply that (1) climate‐sensitive lake ecosystems are more likely controlled by salinity change if both its amplitude and frequency are large enough to induce ecological species sorting; (2) community response to such salinity changes may be predictable, and likely to show coherence across different groups of aquatic biota; and (3) the timing of major community restructuring strongly depends on the ecology of key species, and whether the species sorting is driven by salinity change itself or indirectly by the salinity‐dependent availability of ecological niches.

中文翻译：

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在1650年的湖泊沉积气候变化记录中的底栖动物群落更新

在动荡的湖泊生态系统中，人为干扰的严重性通常难以评估，因为自然动态的强度可抵制或超过由于人类影响而引起的生态系统变化。因此，也很难评估这些生态系统的动植物群落对这种影响的适应力。不幸的是，由于水文动力学与生态位的局部可用性或分布之间的复杂关系，人们对湖泊生态系统在多年时间尺度上对湖水位和盐度波动的自然循环的响应知之甚少。我们提供了肯尼亚（东非）奈瓦沙湖1650年以来的古生态记录，记录了响应于气候驱动的10个主要湖泊序列的两个主要底栖无脊椎动物（棘足纲和成骨纲）群的群落集聚和周转。电平波动。在这段时间内，湖泊深度（由沉积学推断）在约3至> 35 m之间波动，盐度（由化石硅藻组合推断）在〜100至〜23,500 µS / cm之间变化。在大约780年之前，社区对盐度的独特反应要强于对湖泊深度的反应。大约在那个时候，该湖过渡到一个更加开放的水文系统，相对稳定的淡水条件以及与大型植物相关的底栖生境的流行，因此社区对湖深（和表面积）变化的反应变得更加强烈。值得注意的是 在这一过渡过程中，主要群体的改组在两个群体之间是不同步的，因为这取决于每个群体中主要淡水物种的扩散。我们的结果表明：（1）如果盐度变化的幅度和频率都足够大以致引起生态物种的分选，那么对气候敏感的湖泊生态系统更有可能受到盐度变化的控制；（2）社区对这种盐度变化的反应可能是可预测的，并且可能在不同种类的水生生物群之间表现出一致性。（3）主要群落结构重组的时机在很大程度上取决于关键物种的生态，物种的选择是由盐度本身改变还是由盐度依赖的生态位的可用性间接改变。