1. A deep chlorophyll maximum (DCM) is often seen in stratified freshwater bodies at the interface between an anaerobic layer and an oxic layer. A DCM of the green sulfur bacterium Chlorobium phaeobacteroides was previously reported as a dense population in the oxygen devoid layer of a monomictic stratified lake, Lake Kinneret, Israel.
2. In this multidisciplinary study, we examined the vertical distribution and diversity of the DCM photosynthetic community and characterised it spectrally and genetically, over two consecutive years.
3. Pigment composition, together with 16S rDNA sequencing data unveil the presence of more than a single Chlorobium species as dominant members of the DCM community. Altogether, five different Chlorobia genotypes were identified, four of which occurred in both of the studied years. Phylogenetic analysis suggests that the dominant genotype is closely related to C. phaeobacteroides, implying that it contributes the majority of the bacteriochlorophyll‐e found in the DCM of the lake.
4. Hierarchical clustering analysis demonstrates that dissolved oxygen concentration is a strong predictor for the distribution of all Chlorobia genotypes found in Lake Kinneret. Furthermore, this analysis suggests that competition probably exists between the various Chlorobia genotypes and proposes that a C. phaeobacteroides‐related amplicon sequence variant is better equipped to cope with the conditions prevailing in Lake Kinneret metalimnion.
5. Chlorobia genotypes composing the DCM appear at a similar relative abundance in two consecutive years, even though timing and intensity of the DCM were different. This stable structure of the Chlorobia community observed here may represent a general theme in other stratified freshwater bodies harbouring Chlorobia.

中文翻译：

---

重访Kinneret湖的金属定性叶绿素最大值

1. 在分层的淡水体中，厌氧层和有氧层之间的界面经常会出现深层的叶绿素最大值（DCM）。先前报道绿色硫细菌Phlobacterium pheobacteroides的DCM在以色列单种分层湖中的缺氧层中为致密种群。
2. 在这项多学科研究中，我们连续两年检查了DCM光合群落的垂直分布和多样性，并在光谱和遗传上对其进行了表征。
3. 颜料成分以及16S rDNA测序数据揭示出，作为DCM群落的主要成员，存在着不止一种Chlorobium物种。总共鉴定出五种不同的蓝藻基因型，其中两种在两种研究年份中都发生过。系统发育分析表明，占主导地位的基因型密切相关C. phaeobacteroides，这意味着它有助于广大bacteriochlorophyll-的Ë在湖的DCM找到。
4. 层次聚类分析表明，溶解氧浓度是在Kinneret湖中发现的所有蓝藻基因型分布的有力预测指标。此外，该分析表明，各种绿藻基因型之间可能存在竞争，并提出与嗜盐杆菌相关的扩增子序列变异体能够更好地应对金奈雷特湖中的金属条件。
5. 即使DCM的时间和强度不同，但构成DCM的绿藻基因型在连续两年中仍以相似的相对丰度出现。此处观察到的绿藻群落的这种稳定结构可能代表着其他带有绿藻的分层淡水体的一般主题。