Vertical distribution of microbial communities in the Zmajevo oko (Rogoznica lake) during stratified and mixed conditions

Pjevec, Petra; Korlević, Marino; Bura-Nakić, Elvira; Orlić, Sandi Vertical distribution of microbial communities in the Zmajevo oko (Rogoznica lake) during stratified and mixed conditions. In: 14th International Symposium on Microbial Ecology, The Power of the Small, The Book of Abstracts. .

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Abstract

Zmajevo oko is a natural, saline carst lake on the Eastern Adriatic coast. Its protected location between high limestone cliffs, the relatively small freshwater input and the peculiar geochemical setting lead to the occurrence of seasonal stratification, accompanied by sulfidic and anoxic events. During such events, highly elevated sulfide concentrations and the formation of colloidal elemental sulfur, indicated by a milky turbidity, have been observed. The formation of S0 was related to the presence of a dense population of Chromatium like purple sulfur bacteria (PSB) on the sulfide/oxygen chemocline. The influence of sulfide and sulfur on microbial communities above and below this chemocline is still unknown.In this study, we used culture independent methods (comparative 16S rRNA gene analysis and Catalyzed Reporter Deposition - Fluorescencein situhybridization) to determine the microbial community composition and its vertical distribution during and after stratification events.Zmajevo oko represent a very highly productive chemotrophic system. The total number of bacteria in the investigated period was between 3x 106 and 1 x 107. The surface layers of Zmajevo oko have shown to be dominantly populated by marine pelagic organisms, belonging to the Alpha- and Gammaproteobacteria and Bacteroidetes, as well as by oxygenic phototrophes, during both stratified and mixed conditions. Surprisingly, only few PSB related 16S rRNA gene sequences were retrieved from the chemochilne layers. Instead, the chemochline occurring at a depth of ~9 m during stratified periods is strongly dominated by green sulfur bacteria (GSB) sequences, affiliating with Chlorobium sp. Deltaproteobacteria, most likely triving on the reduction of S0 produced by the GSB layer, seem to dominate anoxic layers below the chemochline. When the water column is mixed, the GSB and Deltaproteobacteria populations seem to lose size and importance, and a community resembling those in lower depths replaces it. Still, aerobic organisms known to be involved in reduced sulfur compound oxidation, such as Epsilonproteobacteria and Gammaprotoebacteria from the SUP05 cluster have been detected in all clone libraries, indicating that sulfide oxidation is a relevant energy source for the microbial community regardless of stratification.

Item Type:	Conference or workshop item published in conference proceedings (UNSPECIFIED)
Uncontrolled Keywords:	bacterial diversity; stratification; Rogoznica lake
Subjects:	NATURAL SCIENCES > Biology NATURAL SCIENCES > Interdisciplinary Natural Sciences > Marine Science
Divisions:	Center for Marine Research
Projects:	Project title Project leader Project code Project type Priroda organske tvari, interakcije s mikrokonstituentima i površinama u okolišu [179942] Irena Ciglenečki-Jušić 098-0982934-2717 MZOS Struktura i fiziologija mikrobnih zajednica frontalnih zona sjevernog Jadrana [83206] Mirjana Najdek-Dragić 098-0982705-2729 MZOS
Depositing User:	Marino Korlević
Date Deposited:	20 Nov 2013 09:32
URI:	http://fulir.irb.hr/id/eprint/989

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