engleski

Life under euxinia: Potential role of active prokaryotes in elemental cycling in marine meromictic Rogoznica Lake (Eastern Adriatic coast)

As they resemble the conditions on ancient Earth, meromictic lakes represent interesting habitats to study microbial processes, and in the same time can serve to predict and understand future phenomena, given that occurrence of hypoxic/anoxic environments is increasing. In the present study, we explored active bacterial and archaeal community in the chemocline, monimolimnion and sediment of marine meromictic Rogoznica Lake (Croatia). We employed high-throughput 16S rRNA gene sequencing of cDNA along with quantitive PCR assays targeting phylogenetic markers to describe the ecophysiological interactions underpinning the biogeochemistry and elemental cycling of C, S and N in the Lake. The results revealed clear vertical structure of the microbial community with Gammaproteobacteria dominating the chemocline, Deltaproteobacteria dominating the monimolimnion and significantly higher archaeal abundance in the sediment. However, seasonal changes in the community structure were not pronounced. Quantitative PCR confirmed that bacterial and archaeal abundance remained stable, with no significant changes over the sampling seasons. Diversity in Rogoznica Lake was found to be very low, further implying that biogeochemical cycling of C, S and N is distributed among limited number of taxa with no evidences of potential nitrifiers and denitrifiers and a very weak potential for methane oxidation and anammox reaction. The extreme euxinic chemistry in the Lake severely curtails the ecological and metabolic diversity which relies on dominant taxa, some of which could be easily lost as a result of oscillation in environmental conditions and climate change.

Hypoxic/anoxic marine environments ; microbial communities ; biogeochemical cycling

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