한국 제주해협에서 해양 미소 진핵생물의 계절적 동태와 다양성

Abstract

Marine protists are ubiquitous and play fundamental roles in microbial food-webs and global biogeochemical cycling. We investigated the diversity and spatiotemporal distribution of marine microbial eukaryotes using 18S rRNA V9 metabarcoding in the Jeju Strait of Korea in March, June, September, and November 2017. A total of 1,424,655 sequences and 2,481 OTUs were obtained from 147 samples. Interestingly, parasitic protist sequences represented over 20% of total 18S rDNA sequences. The relative abundances of parasite sequences were relatively higher in June and November (on average 31.8% and 38.7%, respectively) than in March and September (on average 28.1% and 31.5%, respectively). The largest proportions among the parasite sequences were occupied by Syndiniales groups I and II in all samples. The relative proportions of Syndiniales groups I and II showed a marked different pattern in distribution. While the relative abundances of Syndiniales group I were higher in surface water samples than in deep waters, those of Syndiniales group II tended to greatly increase with depth. Syndiniales group II Clade 10+11 appeared mostly in the mid water layers, whereas Syndiniales group II clade 6 and 7 occurred in the bottom water layers. A co-occurrence analysis revealed strong positive associations between Syndiniales group II and Ciliophora, Syndiniales group II and Dinophyceae in September and strong positive associations between Syndiniales group II clades 6 and 7 and Radiolarian Spumellarida, suggesting a host and parasite relationship. The strong negative relationship also revealed between Syndinials group II and Dinophysae, due to contrasting differences in their appearance depth according to halocline in September. The dominant proportions of parasite sequences in microbial eukaryotes communities indicate that they are one of the important components as well as play potentially important roles in the microbial food webs in the highly dynamic coastal system.