ABSTRACT: The water column of marine Rogoznica Lake (Croatia) is stratified throughout the year. However, on rare occasions, the lake exhibits complete mixing, primarily driven by meteorological conditions. On such occasions, anoxic, sulfide-rich bottom water mixes with the oxic surface layer, triggering both the oxidation of sulfide predominantly to colloidal sulfur and the establishment of euxinic conditions throughout the water column. We investigated prokaryotic communities during euxinic holomictic conditions. High-throughput sequencing of the 16S rRNA gene showed that these sulfur-driven communities were dominated by Planctomycetales, chemolithotrophic Epsilonbactereota (mainly Arcobacteraceae) and Gammaproteobacteria (Thioglobaceae), followed by Alpha- (Rhodobacteraceae) and Deltaproteobacteria (Desulfobulbaceae and Desulfobacteraceae). The majority of archaeal sequences belonged to Nanoarchaeota, all of which were designated as Woesearchaeia. This class has not been recorded in other meromictic lakes. Both bacterial and archaeal 16S rRNA gene abundance did not vary significantly across the vertical profile of the lake, as shown by quantitative PCR. However, hierarchical clustering showed a significant difference between the microbial assemblage structure in stratified periods and during a holomictic event. Besides the structure, this stressful event had a manifold effect on bacterial and archaeal assemblages by decreasing their diversity and abundance when compared to the usual stratified conditions.

中文翻译：

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含汞的整体条件对海洋淡水湖原核组合的影响

摘要：Rogoznica湖（克罗地亚）的水柱全年都分层。然而，在极少数情况下，该湖展现出完全的混合，主要是受气象条件的驱动。在这种情况下，富氧的，富含硫化物的底部水与含氧表面层混合，既触发了硫化物主要氧化为胶态硫的氧化，又在整个水柱中建立了富营养的条件。我们调查了在富营养的整体条件下的原核生物群落。高通量16S rRNA基因测序表明，这些硫驱动的社区是由主导Planctomycetales，化能无机营养Epsilonbactereota（主要是Arcobacteraceae）和γ-变形菌（Thioglobaceae），其次是阿尔法- （Rhodobacteraceae）和δ-变形菌（Desulfobulbaceae和Desulfobacteraceae）。大多数古细菌序列属于Nanoarchaeota，所有这些序列都指定为Woesearchaeia。尚未在其他大洋湖泊中记录到此类。如定量PCR所示，细菌和古细菌16S rRNA基因的丰度在整个湖的垂直剖面上都没有显着变化。然而，分层聚类表明在分层期间和整体事件期间微生物组合结构之间存在显着差异。除了结构之外，与通常的分层条件相比，这种压力事件通过降低细菌和古细菌的多样性和丰度，对细菌和古细菌的组合具有多种作用。