Department of Molecular Biology and Biotechnology, Faculty of Biology and Geology, Babeş-Bolyai University, 5-7 Clinicilor Str., 400006, Cluj-Napoca, Romania.
National Institute of Research and Development for Biological Sciences, Institute of Biological Research, 48 Republicii Str., 400015, Cluj-Napoca, Romania.
Environ Microbiol. 2021 Jul;23(7):3523-3540. doi: 10.1111/1462-2920.14909. Epub 2020 Jan 29.
Ursu Lake is located in the Middle Miocene salt deposit of Central Romania. It is stratified, and the water column has three distinct water masses: an upper freshwater-to-moderately saline stratum (0-3 m), an intermediate stratum exhibiting a steep halocline (3-3.5 m), and a lower hypersaline stratum (4 m and below) that is euxinic (i.e. anoxic and sulphidic). Recent studies have characterized the lake's microbial taxonomy and given rise to intriguing ecological questions. Here, we explore whether the communities are dynamic or stable in relation to taxonomic composition, geochemistry, biophysics, and ecophysiological functions during the annual cycle. We found: (i) seasonally fluctuating, light-dependent communities in the upper layer (≥0.987-0.990 water-activity), a stable but phylogenetically diverse population of heterotrophs in the hypersaline stratum (water activities down to 0.762) and a persistent plate of green sulphur bacteria that connects these two (0.958-0.956 water activity) at 3-3.5 to 4 m; (ii) communities that might be involved in carbon- and sulphur-cycling between and within the lake's three main water masses; (iii) uncultured lineages including Acetothermia (OP1), Cloacimonetes (WWE1), Marinimicrobia (SAR406), Omnitrophicaeota (OP3), Parcubacteria (OD1) and other Candidate Phyla Radiation bacteria, and SR1 in the hypersaline stratum (likely involved in the anaerobic steps of carbon- and sulphur-cycling); and (iv) that species richness and habitat stability are associated with high redox-potentials. Ursu Lake has a unique and complex ecology, at the same time exhibiting dynamic fluctuations and stability, and can be used as a modern analogue for ancient euxinic water bodies and comparator system for other stratified hypersaline systems.
乌尔苏湖位于罗马尼亚中部的中新世盐矿床中。它是分层的，水柱中有三个不同的水团：一个上部淡水到中度咸水层（0-3 m），一个中间层，其表现出陡峭的盐度跃变层（3-3.5 m），和一个下部过盐水层（4 m 及以下），该层为缺氧和硫化物。最近的研究已经描述了该湖的微生物分类学，并提出了一些有趣的生态问题。在这里，我们探讨了在年度周期中，群落是否与分类组成、地球化学、生物物理学和生理生态功能相关，是动态的还是稳定的。我们发现：（i）上层（≥0.987-0.990 水活度）季节性波动、光依赖性群落，过盐水层（水活度低至 0.762）中稳定但系统发育多样的异养种群，以及连接这两个水层的持久的绿硫细菌板块（0.958-0.956 水活度），位于 3-3.5 至 4 m 处；（ii）可能涉及湖泊三个主要水团之间和内部的碳和硫循环的群落；（iii）未培养的谱系，包括 Acetothermia（OP1）、Cloacimonetes（WWE1）、Marinimicrobia（SAR406）、Omnitrophicaeota（OP3）、Parcubacteria（OD1）和其他候选门辐射细菌，以及过盐水层中的 SR1（可能参与碳和硫循环的厌氧步骤）；（iv）物种丰富度和栖息地稳定性与高氧化还原电位相关。乌尔苏湖具有独特而复杂的生态系统，同时表现出动态波动和稳定性，可以作为古代缺氧水体的现代类似物，并作为其他分层过盐水系统的比较系统。
