engleski

Sun is shining, salinity is rising, are microbes responding?

The freshwater availability in the Mediterranean region is declining due to the intense water exploitations and the climate change progression. The intensified stress on coastal lake systems induces changes in microbial communities responsible for prevalent biogeochemical cycles, potentially leading to irreversible lake states. Salinization is one of the main concerns affecting coastal freshwater systems. Lake Vrana is a shallow coastal lake connected to the Adriatic Sea through the karstified ridge. This lake is known to experience occasional salinity intrusions that induce structural changes in the previously autochthone fauna. We hypothesized that the imbalance of precipitation-evaporation rates would lead to the salinity intrusion and cause different seasonal changes in the particle-associated and free-living prokaryote structures. Using the 16S rDNA high-throughput sequencing of particle- associated and free-living prokaryotes, we performed a year-long study to capture the spatio- temporal changes of microbial communities in response to salinization and drought. Seasonality played a critical role in microbial community formation with clear patterns of the most abundant taxa in both fractions, while salinization induced halophilic bacteria in the dry summer period. The co-occurrence analysis of free-living and particle-associated taxa revealed two divided clusters dependent on the salinity preference. These results demonstrate that seasonal salinization has a significant role in shaping the prokaryote community of a shallow lake, which leads to the increase of opportunistic halotolerant species whose occurrence could have the potential to act as salinization indicators. Our findings contribute to the growing studies that emerged as a need for mitigating changes in scarce Mediterranean freshwater resources.

Salinization ; Halotolerant taxa ; Coastal lake ; Climate change ; Microbial community

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