Illumina MiSeq Analysis and Comparison of Freshwater Microalgal Communities on Ulleungdo and Dokdo Islands

Abstract

Ulleungdo and Dokdo are volcanic islands with an oceanic climate located off the eastern coast of South Korea. In the present study, we used barcoded Illumina MiSeq to analyze eukaryotic microalgal genera collected from Seonginbong, the highest peak on Ulleungdo, and from groundwater sites on Dongdo and Seodo Islands, which are part of Dokdo. Species richness was significantly greater in the Seonginbong samples than in the Dongdo and Seodo samples, with 834 operational taxonomic units (OTUs) identified from Seonginbong compared with 203 OTUs and 182 OTUs from Dongdo and Seodo, respectively. Taxonomic composition analysis was also used to identify the dominant microalgal phyla at each of the three sites, with Chlorophyta (green algae) the most abundant phyla on Seonginbong and Dongdo, and Bacillariophyta (diatoms) the most abundant on Seodo. These findings suggest that differences in the abundances of Chlorophyta and Bacillariophyta species in the Seonginbong, Dongdo, and Seodo samples are due to variations in species richness and freshwater resources at each sampling location. To the best of our knowledge, this is the first report to detail freshwater microalgal communities on Ulleungdo and Dokdo. As such, the number of species identified in the Seonginbong, Dongdo, and Seodo samples might be an indicator of the ecological differences among these sites and varying characteristics of their microbial communities. Information regarding the microalgal communities also provides a basis for understanding the ecological interactions between microalgae species and other eukaryotic microorganisms.

Environmental Factors Associated with the Eukaryotic Microbial Community and Microalgal Groups in the Mountain Marshes of South Korea

“…Most microalgae in aquatic environments with water flow are attached to surfaces ( Benito 2020 ; Plante et al 2021). Typically, attached algae are dominated by diatoms, including Bacillariophyta and some green algae, including Chlorophyta ( Yun et al 2019 ; Benito 2020 ; Plante et al 2021). Therefore, in an environment with water flow, the floating algae are relatively less abundant ( Yun et al 2019 ; Prazukin et al 2020 ).…”

“…Microbial community analysis. Illumina MiSeq analyses of the microbial communities were performed by the Macrogen (Macrogen, Seoul, South Korea, https://dna.macrogen.com/kor/), as described previously (Yun et al 2019 (Vo and Jedlicka 2014). The 18S V4 primer set was used to amplify the 18S rRNA regions (Stoeck et al 2010).…”

“…Taxonomic identification and phylogenetic analysis. The raw sequencing data were demultiplexed using the index sequence, and a FASTQ file was generated for each sample (Yun et al 2019). The adapter sequence was removed using SeqPurge, and the sequencing error correction was performed on the overlapping areas of the Microbial communities in mountain marshes 2 217 correct reads (Sturm et al 2016).…”

“…Microbial community analysis. Illumina MiSeq analyses of the microbial communities were performed by the Macrogen (Macrogen, Seoul, South Korea, https://dna.macrogen.com/kor/ ), as described previously ( Yun et al 2019 ). DNA for Illumina MiSeq sequencing was extracted from the samples according to the manufacturer’s protocol of the PowerSoil® DNA Isolation Kit (Cat.…”

“…Typically, attached algae are dominated by diatoms, including Bacillariophyta and some green algae, including Chlorophyta (Yun et al 2019;Benito 2020;Plante et al 2021). Therefore, in an environment with water flow, the floating algae are relatively less abundant (Yun et al 2019;Prazukin et al 2020). In an aquatic environment where water flow is weak, floating algae dominate, with its species' composition often determined by environmental factors (Mashwani 2020).…”