Cyanobacterial blooms are one of the most significant threats to global water security and freshwater biodiversity. Interactions among multiple stressors, including habitat degradation, species invasions, increased nutrient runoff, and climate change, are key drivers. However, assessing the role of anthropogenic activity on the onset of cyanobacterial blooms and exploring response variation amongst lakes of varying size and depth is usually limited by lack of historical records. In the present study we applied molecular, paleolimnological (trace metal, Itrax-µ-XRF and hyperspectral scanning, chronology), paleobotanical (pollen) and historical data to reconstruct cyanobacterial abundance and community composition and anthropogenic impacts in two dune lakes over a period of up to 1200 years. Metabarcoding and droplet digital PCR results showed very low levels of picocyanobacteria present in the lakes prior to about CE 1854 (1839–1870 CE) in the smaller shallow Lake Alice and CE 1970 (1963–1875 CE) in the larger deeper Lake Wiritoa. Hereafter bloom-forming cyanobacteria were detected and increased notably in abundance post CE 1984 (1982–1985 CE) in Lake Alice and CE 1997 (1990–2007 CE) in Lake Wiritoa. Currently, the magnitude of blooms is more pronounced in Lake Wiritoa, potentially attributable to hypoxia-induced release of phosphorus from sediment, introducing an additional source of nutrients. Generalized linear modelling was used to investigate the contribution of nutrients (proxy = bacterial functions), temperature, redox conditions (Mn:Fe), and erosion (Ti:Inc) in driving the abundance of cyanobacteria (ddPCR). In Lake Alice nutrients and erosion had a statistically significant effect, while in Lake Wiritoa nutrients and redox conditions were significant.

蓝藻水华是对全球水安全和淡水生物多样性最严重的威胁之一。多种压力因素之间的相互作用，包括栖息地退化、物种入侵、养分径流增加和气候变化，是关键驱动因素。然而，评估人类活动对蓝藻水华爆发的作用以及探索不同大小和深度的湖泊之间的响应变化通常因缺乏历史记录而受到限制。在本研究中，我们应用分子、古湖泊学（痕量金属、Itrax-μ-XRF 和高光谱扫描、年代学）、古植物学（花粉）和历史数据来重建两个沙丘湖在一段时间内的蓝藻丰度和群落组成以及人为影响。长达1200年。元条形码和液滴数字 PCR 结果显示，大约公元 1854 年（公元 1839-1870 年）之前较小的浅水爱丽丝湖和公元 1970 年（公元 1963-1875 年）较大较深的维里托亚湖中的湖泊中存在非常低水平的微微蓝细菌。此后，在公元1984年（公元1982-1985年）和公元1997年（公元1990-2007年）在维里托亚湖中检测到形成水华的蓝藻，并且数量显着增加。目前，维里托亚湖水华的严重程度更为明显，这可能是由于缺氧导致沉积物中磷的释放，从而引入了额外的营养来源。使用广义线性模型研究营养物（代理=细菌功能）、温度、氧化还原条件（Mn:Fe）和侵蚀（Ti:Inc）对蓝藻丰度（ddPCR）的影响。在爱丽丝湖中，营养物和侵蚀具有统计上显着的影响，而在维里托亚湖中，营养物和氧化还原条件则具有显着影响。