In a biogeochemical cycle, chemical elements are shuttled between oxidized and reduced forms in a series of steps that may be biotically or abiotically mediated. The availability of electron acceptors and donors is strongly affected with environmental conditions. Environmental perturbations are influenced by climate changes, which impact is expected to increase the future perturbations and consequently changes in ecosystem structure and functioning, i.e. redox regime shifts in microbiologically mediated biogeochemical cycles.<br/>In our work biogeochemical cycle of sulfur (S) was studied in Rogoznica Lake, an example of unique euxinic marine lake on the eastern Adriatic coast (Croatia). The Lake is strongly stratified during the season into upper oxic and anoxic deeper water layers, with the mixolimnion that  varies seasonally in depth and thickness due to influence of meteorological conditions. It can be considered as a system with both meromictic and anoxic holomictic conditions, which alternate seasonally and highly affect the lake's geomicrobiology. Euxinic water layer (mM sulfide concentrations) and laminated sediment are enriched with trace metals that accumulate in sulfidic environment (Fe, Mo). Microbial diversity in Rogoznica Lake is very low, implying that biogeochemical cycling of S is distributed among limited number of taxa. The Lake's extreme environment which recently has been recognized to suffer from extreme weather events, severely curtails the ecological and metabolic diversity relying on dominant taxa, some of which could be easily lost as a result of environmental perturbations.<br/>

Redox regime shifts in euxinic marine environment (Rogoznica Lake, eastern Adriatic coast)

255th National Meeting (2018)

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