title: Vertical physico-chemical gradients with distinct microbial communities in the hypersaline and heliothermal Lake Ursu (Sovata, Romania).
abstract: The effect of vertical physico-chemical stratification on the planktonic microbial community composition of the deep, hypersaline and heliothermal Lake Ursu (Sovata, Romania) was examined in this study. On site and laboratory measurements were performed to determine the physical and chemical variables of the lake water, and culture-based and cultivation-independent techniques were applied to identify the members of microbial communities. The surface of the lake was characterized by a low salinity water layer while the deepest region was extremely saline (up to 300 g/L salinity). Many parameters (e.g. photosynthetically active radiation, dissolved oxygen concentration, pH, redox potential) changed dramatically from 2 to 4 m below the water surface in conjunction with the increasing salinity values. The water temperature reached a maximum at this depth. At around 3 m depth, there was a water layer with high (bacterio) chlorophyll content dominated by Prosthecochloris vibrioformis, a phototrophic green sulfur bacterium. Characteristic microbial communities with various prokaryotic taxa were identified along the different environmental parameters present in the different water layers. Some of these bacteria were known to be heterotrophic and therefore may be involved in the decomposition of lake organic material (e.g. Halomonas, Idiomarina and Pseudoalteromonas) while others in the transformation of sulfur compounds (e.g. Prosthecochloris). Eukaryotic microorganisms identified by molecular methods in the lake water belonged to genera of green algae (Mantionella and Picochlorum), and were restricted mainly to the upper layers.
authors: Department of Bioengineering, Sapientia Hungarian University of Transylvania, Piaţa Libertăţii 1, 530104, Miercurea Ciuc, Romania.
authors: István
authors: I
authors: Máthé
authors: Andrea K
authors: AK
authors: Borsodi
authors: Erika M
authors: EM
authors: Tóth
authors: Tamás
authors: T
authors: Felföldi
authors: Laura
authors: L
authors: Jurecska
authors: Gergely
authors: G
authors: Krett
authors: Zsolt
authors: Z
authors: Kelemen
authors: Erzsébet
authors: E
authors: Elekes
authors: Katalin
authors: K
authors: Barkács
authors: Károly
authors: K
authors: Márialigeti
mesh_terms: D060106:Lakes / Q000737:chemistry / Q000382:microbiology*; D064307:Microbiota; D012383:Romania; D054712:Salinity; D055049:Salt Tolerance