Dynamika sezonowych zmian bioróżnorodności bakterii w jeziorach przymorsskich: łebsko i sarbsko

The Polish shore of the Baltic Sea is rich in brackish lakes of estuarine character. One of them are lakes of the Gardnieńsko-Łebska Lowland. Each of these reservoirs has its own hydrological and ecological specificity, which results in the fact that knowledge about these dynamic water ecosystems is incomplete and requires further researches. The aim of this work was to study seasonal changes in bacterial diversity in coastal brackish lakes: Sarbsko and Łebsko. Biodiversity was studied for salinity gradient, as well as physicochemical and biological changes (caused by seasons and depth of the reservoir from which the test material was taken). To monitor the genotypic variation of individual microorganisms and estimate biodiversity of the bacterial community in the settlement and to estimate the geno-type complexity of the samples PCR-DGGE method (polymerase chain reaction, combined with denaturing gradient gel electrophoresis) was used. The molecular marker used in the studies was a fragment of the 16S rRNA gene. The effects of the experiment were documented in the form of photos in the ultraviolet light of the PCR-DGGE products, on the basis of which densitometric analysis was performed, Dice similarity coefficient and Shannon biodiversity index was calculated, and dendrograms were created based on the nearest neighbor algorithm. The research showed that the biodiversity of the community during the experiment was not constant and ranged from relatively poor to average geno-typically rich. The lowest values of the Shannon index were observed in the summer, which was related to salinity fluctuations and high temperature. In the summer, a decrease in the similarity of Dice in the Łebsko lake was also observed. Such a situation did not take place in Sarbsko. The project showed that Sarbsko has a more stable bacterial diversity, which is indicated by smaller fluctuations in the Shannon biodiversity index. It was observed that bacteria genotypic structure has changed slightly in seasonal cycle in tha Sarbsko lake, as dendrograms show. Temperature through the seasons also influence the bacterial biodiversity. What is more relation between biodiversity and oxygen concentration had been noticed. During the experiment there were no changes in pH level and this parameter has not got influence on bacteria.