The influence of lake restoration efforts on lake bottom-water conditions and varve preservation is not well known. We studied varved sediments deposited during the last 80 years along a water-depth transect in the Enonsaari Deep, a deep-water area of the southernmost Enonselkä Basin, Lake Vesijärvi, southern Finland. For the last few decades, the Enonselkä Basin has been subject to ongoing restoration efforts. Varve, elemental, and diatom analyses were undertaken to explore how these actions and other human activities affected varve preservation in the Enonsaari Deep. In contrast to most varved Finnish lakes, whose water columns have a natural tendency to stratify, and possess varve records that span thousands of years, varve formation and preservation in Lake Vesijärvi was triggered by relatively recent anthropogenic stressors. The multi-core varve analysis revealed that sediment in the Enonsaari Deep was initially non-varved, but became fully varved in the late 1930s, a time of increasing anthropogenic influence on the lake. The largest spatial extent of varves occurred in the 1970s, which was followed by a period of less distinguishable varves, which coincided with diversion of sewage from the lake. Varve preservation weakened during subsequent decades and was terminated completely by lake aeration in the 2010s. Despite improvements in water quality, hypolimnetic oxygen depletion and varve preservation persisted beyond the reduction in sewage loading, initial aeration, and biomanipulation. These restoration efforts, however, along with other human actions such as harbor construction and dredging, did influence varve characteristics. Varves were also influenced by diatom responses to anthropogenic forcing, because diatoms form a substantial part of the varve structure. Of all the restoration efforts, a second episode of aeration seems to have had the single most dramatic impact on profundal conditions in the basin, resulting in replacement of a sediment accumulation zone by a transport or erosional zone in the Enonsaari Deep. We conclude that human activities in a lake and its catchment can alter lake hypolimnetic conditions, leading to shifts in lake bottom dynamics and changes in varve preservation.

湖泊修复工作对湖底水条件和海藻保存的影响尚不清楚。我们研究了在过去 80 年中沿着 Enonsaari Deep（芬兰南部 Vesijärvi 湖最南端 Enonselkä 盆地的深水区）的水深横断面沉积的沉积物。在过去的几十年里，Enonselkä 盆地一直在进行持续的修复工作。进行了 Varve、元素和硅藻分析，以探索这些行为和其他人类活动如何影响 Enonsaari Deep 中的 varve 保存。与大多数有水体的芬兰湖泊相比，它们的水柱具有自然分层趋势，并且拥有跨越数千年的变体记录，相比之下，Vesijärvi 湖的变体形成和保存是由相对较新的人为压力源触发的。多核阀门分析表明，Enonsaari Deep的沉积物最初是无阀门的，但在1930年代后期，即人为因素对湖泊的影响不断增加的时期，该沉积物变成了完全阀门。1970 年代出现了斑叶藻的最大空间范围，随后是一段不太明显的斑叶藻，恰逢污水从湖中分流。Varve 的保存在随后的几十年中减弱，并在 2010 年代因湖泊曝气而完全终止。尽管水质有所改善，但在污水负荷、初始曝气和生物操纵的减少之外，水下氧气消耗和藻类保存仍然存在。然而，这些修复工作，以及港口建设和疏浚等其他人类行为，确实影响了 varve 的特征。硅藻对人为强迫的反应也影响了天牛，因为硅藻构成了脉管结构的重要组成部分。在所有恢复工作中，第二次曝气似乎对盆地的深部条件产生了最显着的影响，导致沉积物堆积区被埃农萨里深水区的运输或侵蚀区取代。我们得出的结论是，人类在湖泊及其集水区的活动会改变湖泊的低水位条件，从而导致湖底动态的变化和海藻保存的变化。导致沉积物堆积区被 Enonsaari Deep 中的输送带或侵蚀带取代。我们得出的结论是，人类在湖泊及其集水区的活动会改变湖泊的低水位条件，从而导致湖底动态的变化和海藻保存的变化。导致沉积物堆积区被 Enonsaari Deep 中的输送带或侵蚀带取代。我们得出的结论是，人类在湖泊及其集水区的活动会改变湖泊的低水位条件，从而导致湖底动态的变化和海藻保存的变化。