Identification Of Antarctic Freshwater Diatom Species Using Microscopic And Molecular Techniques

Abstract

Because of the great morphological similarity of some diatom species, eDNA method has been the method that was particularly intended to be used in this study. DNAs were successfully isolated from all of the samples. However, the RuBisCO large subunit (rbcL) gene part that is specific to diatoms could be reproduced in polymerase chain reacton (PCR) only in 2020 Horseshoe Island samples. The DNA damage in 2017 and 2019 samples pointed out rapid damage of diatom DNA and highligths the importance of addition of nuclease blockers for right storage conditions of the samples. However, the amount of diatom DNA in the 2020 samples were not in the required amounts necessary for the new generation sequencing (NGS) method. Between the two microscope methods, SEM gave more successful results for morphological species determination compared to light microscope since it allowed higher resolution images that was necessary for detailed viewing of diatom structures. On the other hand, the light microscope offered a longer time and detailed study on the samples. All the images were then combined with SEM images and a common species designation was made. In conclusion, freshwater diatom species in fourteen Antarctic lakes in King George and Horseshoe Island were determined. This study also provided a basis for new studies in the future, and by knowing the diatom species distributions in Antarctic lakes, metabolic models can be used to understand the possible species-specific response to climate change in Antarctica.