During the 20th century, many lakes in the Northern Hemisphere were affected by increasing human population and urbanization along their shorelines and catchment, resulting in aquatic eutrophication. Ecosystem monitoring commenced only after the changes became apparent, precluding any examination of timing and dynamics of initial community change in the past and comparison of pre- and postimpact communities. Peri-Alpine Lake Constance (Germany) underwent a mid-century period of eutrophication followed by re-oligotrophication since the 1980s and is now experiencing warm temperatures. We extended the period for which monitoring data of indicator organisms exist by analysing historical environmental DNA (eDNA) from a sediment core dating back some 110 years. Using three metabarcoding markers—for microbial eukaryotes, diatoms and cyanobacteria—we revealed two major breakpoints of community change, in the 1930s and the mid-1990s. In our core, the latest response was exhibited by diatoms, which are classically used as palaeo-bioindicators for the trophic state of lakes. Following re-oligotrophication, overall diversity values reverted to similar ones of the early 20th century, but multivariate analysis indicated that the present community is substantially dissimilar. Community changes of all three groups were strongly correlated to phosphorus concentration changes, whereas significant relationships to temperature were only observed when we did not account for temporal autocorrelation. Our results indicate that each microbial group analysed exhibited a unique response, highlighting the particular strength of multimarker analysis of eDNA, which is not limited to organisms with visible remains and can therefore discover yet unknown responses and abiotic–biotic relationships.

中文翻译：

---

沉积物核心环境DNA多标记分析重建康斯坦茨湖历史浮游植物群落的人为影响

在 20 世纪，北半球的许多湖泊受到人口增加和海岸线和集水区城市化的影响，导致水体富营养化。生态系统监测仅在变化变得明显后才开始，排除了对过去初始社区变化的时间和动态以及影响前后社区的比较的任何检查。高山附近的康斯坦茨湖（德国）经历了本世纪中叶的富营养化，然后是自 1980 年代以来的再贫营养化，现在正在经历温暖的气温。我们通过分析可追溯到大约 110 年前的沉积岩芯的历史环境 DNA (eDNA)，延长了指示生物监测数据的存在期限。使用三个元条形码标记——对于微生物真核生物，硅藻和蓝藻——我们揭示了 1930 年代和 1990 年代中期群落变化的两个主要断点。在我们的核心中，硅藻表现出最新的反应，硅藻通常用作湖泊营养状态的古生物指标。在重新贫营养化之后，整体多样性值恢复到 20 世纪初的相似值，但多变量分析表明，目前的群落有很大不同。所有三组的群落变化都与磷浓度变化密切相关，而仅当我们没有考虑时间自相关时才观察到与温度的显着关系。我们的结果表明，分析的每个微生物组都表现出独特的反应，突出了 eDNA 多标记分析的特殊优势，