Environmental Factors Associated with the Eukaryotic Microbial Diversity of Ulleungdo Volcanic Island in South Korea

Abstract: Ulleungdo is a volcanic island with an oceanic climate seasonally affected by warm and cold currents. The freshwater ecosystems of Ulleungdo Island act as an ecological indicator that reveals changes caused by various environmental factors. This study applied Illumina MiSeq to analyze microalgal groups within the eukaryotic microbial community and determine regional differences in microalgal groups inhabiting Ulleungdo Island. Also, we compared the Illumina MiSeq analysis with the culture-based analysis results. The 18S rRNA regions were amplified using an 18S V4 primer set to analyze eukaryotic microbial and microalgal communities. As a result, Basidiomycota (fungi) was the predominant eukaryotic microbial group. The proportion of Chlorophyta (green algae) in the microalgal group was higher than that of Bacillariophyta (diatoms). The microalgal species detected included two diatoms (Achnanthidium minutissimum and Nitzschia palea) and three green algae (Dictyosphaerium spp., Tetradesmus obliquus, and Desmodesmus spp.). Additionally, the composition and species diversity of eukaryotic microbial communities changed according to the environmental factors of each stream or groundwater source. Illumina MiSeq analysis is a powerful tool for overcoming the limitations of culture-based analyses. Therefore, our research provided an enhanced ecological understanding of environmental factors associated with microalgal groups within the eukaryotic microbial community of Ulleungdo Island.