부산 용호만에서 기생성 와편모류 신디니움목의 다양성과 계절적 동태

Abstract

Marine Alveolate groups including the parasitoid Syndiniales, are widely distributed with greate genetic diversity and abundance in the oceans. They infect and potentially control diverse hosts populations including dinoflagellates, ciliates, radiolarians, fish eggs, fish larvae, and crustaceans. By killing or reducing their hosts, Syndiniales may play a key role in maintaining ecosystem diversity. Despite the role, syndinean parasites remain enigmatic, particularly with respect to their temporal dynamics and parasite-host interactions. Here we employed 18S rRNA metabarcoding to analyze the genetic diversity and seasonal dynamics of Syndinales and network analyses were performed to reveal the interactions between syndinean parasites and hosts dynamics. Surface water samples were weekly collected from May 2018 to April 2019. Samples at three different depths (surface, chlorophyll maximum, and bottom layers) were weekly collected from August to October 2019 in Yongho Bay of Busan, Korea. A total of 749,734 sequences and 3,241 OTUs were obtained from seasonal and depth samples. Among them, Syndiniales groups formed 8% in total sequences. In particular, they are genetically diverse, accounting for 17% of total OTUs. The groups exhibited higher relative abundance from October to December (5 to 18%) than other months (0.3% to 11%) and highest relative abundance reads (4~32%) in bottom layer then other depth (0.7~17%). In particular, Syndiniales Group I and II showed higher relative abundance and OTU richness than other Alveolate groups. Co-occurrence and network analyses showed 789 nodes and 311,656 edges. Among them, Syndiniales OTUs accounted for 6% nodes and 32% edges, suggesting that they had a lot of associations with other protist OTUs. Syndiniales Group I had significant positive associations with Spumellarida, Dinophyceae, and Bacillariophyta. Syndiniales Group II had significant positive associations with Spumellarida, Bacillariophyta, MAST and Dinophyceae. The proportions, diversity and interactions of syndiniales sequences in microbial eukaryotes communities indicate that they are the important group as well as play potentially key roles in the microbial food webs in Korean coastal water.