Since the beginning of the Anthropocene, lacustrine biodiversity has been influenced by climate change and human activities. These factors advance the spread of harmful cyanobacteria in lakes around the world, which affects water quality and impairs the aquatic food chain. In this study, we assessed changes in cyanobacterial community dynamics via sedimentary DNA (sedaDNA) from well-dated lake sediments of Lake Tiefer See, which is part of the Klocksin Lake Chain spanning the last 350 years. Our diversity and community analysis revealed that cyanobacterial communities form clusters according to the presence or absence of varves. Based on distance-based redundancy and variation partitioning analyses (dbRDA and VPA) we identified that intensified lake circulation inferred from vegetation openness reconstructions, δ¹³C data (a proxy for varve preservation) and total nitrogen content were abiotic factors that significantly explained the variation in the reconstructed cyanobacterial community from Lake Tiefer See sediments. Operational taxonomic units (OTUs) assigned to Microcystis sp. and Aphanizomenon sp. were identified as potential eutrophication-driven taxa of growing importance since circa common era (ca. CE) 1920 till present. This result is corroborated by a cyanobacteria lipid biomarker analysis. Furthermore, we suggest that stronger lake circulation as indicated by non-varved sediments favoured the deposition of the non-photosynthetic cyanobacteria sister clade Sericytochromatia, whereas lake bottom anoxia as indicated by subrecent- and recent varves favoured the Melainabacteria in sediments. Our findings highlight the potential of high-resolution amplicon sequencing in investigating the dynamics of past cyanobacterial communities in lake sediments and show that lake circulation, anoxic conditions, and human-induced eutrophication are main factors explaining variations in the cyanobacteria community in Lake Tiefer See during the last 350 years.

自人类世开始，湖泊生物多样性就受到气候变化和人类活动的影响。这些因素会促进有害蓝藻在世界各地湖泊中的传播，从而影响水质并损害水生食物链。在这项研究中，我们通过来自 Tiefer See 湖（过去 350 年来 Klocksin 湖链的一部分）的陈旧湖泊沉积物的沉积 DNA (sedaDNA) 评估了蓝藻群落动态的变化。我们的多样性和群落分析表明，蓝藻群落根据斑的存在与否形成集群。基于基于距离的冗余和变异分区分析（dbRDA 和 VPA），我们确定了从植被开放度重建推断的强化湖泊循环，δ ¹³C 数据（代表 varve 保存）和总氮含量是非生物因素，可以显着解释 Tiefer See 湖沉积物中重建的蓝藻群落的变化。分配给微囊藻属的操作分类单元 (OTU) 。和Aphanizomenonsp. 被确定为潜在的富营养化驱动的分类群，从大约 1920 年左右开始，其重要性日益增加。这一结果得到了蓝藻脂质生物标志物分析的证实。此外，我们建议，如非斑纹沉积物所表明的更强的湖泊循环有利于非光合蓝藻姐妹进化枝 Sericytochromatia 的沉积，而近代和最近的斑纹所表明的湖底缺氧有利于沉积物中的黑色细菌。我们的研究结果突出了高分辨率扩增子测序在调查湖泊沉积物中过去蓝藻群落动态方面的潜力，并表明湖泊循环、缺氧条件、