Long-term trends in freshwater bacterial community composition (BCC) and dynamics are not yet well characterized, particularly in large lake ecosystems. We addressed this gap by temporally (15 months) and spatially (6 sampling locations) characterizing BCC variation in lakes Erie and St. Clair; two connected ecosystems in the Laurentian Great Lakes. We found a spatial variation of the BCC between the two lakes and among the sampling locations (significant changes in the relative abundance of 16% of the identified OTUs at the sampling location level). We observed five distinct temporal clusters (UPGMA broad-scale temporal variation) corresponding to seasonal variation over the 15 months of sampling. Temporal variation among months was high, with significant variation in the relative abundance of 69% of the OTUs. We identified significant differences in taxonomic composition between summer months of 2016 and 2017, with a corresponding significant reduction in the diversity of BCC in summer 2017. As bacteria play a key role in biogeochemical cycling, and hence in healthy ecosystem function our study defines the scope for temporal and spatial variation in large lake ecosystems. Our data also show that freshwater BCC could serve as an effective proxy and monitoring tool to access large lake health.

中文翻译：

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Laurentian大伊利湖和圣克莱尔湖大型淡水生态系统海岸线细菌群落的时空动态

淡水细菌群落组成 (BCC) 和动态的长期趋势尚未得到很好的表征，特别是在大型湖泊生态系统中。我们通过时间（15 个月）和空间（6 个采样位置）表征伊利湖和圣克莱尔湖的 BCC 变化来解决这一差距；Laurentian Great Lakes 中两个相互连接的生态系统。我们发现两个湖泊之间和采样位置之间的 BCC 存在空间变化（在采样位置级别，16% 的已识别 OTU 的相对丰度发生显着变化）。我们观察到五个不同的时间簇（UPGMA 大尺度时间变化），对应于 15 个月的采样期间的季节性变化。月份之间的时间变化很大，69% 的 OTU 的相对丰度存在显着变化。我们发现 2016 年和 2017 年夏季之间的分类组成存在显着差异，2017 年夏季 BCC 的多样性相应显着减少。由于细菌在生物地球化学循环中发挥关键作用，因此在健康的生态系统功能中，我们的研究定义了范围用于大型湖泊生态系统的时空变化。我们的数据还表明，淡水 BCC 可以作为获取大型湖泊健康状况的有效代理和监测工具。