Determining ecological interactions of key dinoflagellate species using intensive metabarcoding approach in a semi-closed coastal ecosystem of South Korea

Abstract

Marine phytoplankton communities are pivotal in biogeochemical cycles and impact global climate change. However, the dynamics of the dinoflagellate community, their co-occurrence relationship with other eukaryotic plankton communities, and environmental factors remain poorly understood. In this study, we aimed to analyze the temporal changes in the eukaryotic plankton community using 18S rDNA metabarcoding approach. We performed intensive monitoring for 439 days at interval of three days during the period from November 2018 to June 2020 (n=260) in Jangmok Bay Time-series Monitoring Site in South Korea. Minute variations were assessed in the amplicon sequence variants (ASVs). Among 16,224 ASVs obtained, dinoflagellates were the most abundant in the plankton community (38% of total relative abundance). The dinoflagellate community was divided into 21 groups via cluster analysis, which showed an annually similar distribution of low-temperature periods. Additionally, we selected 11 taxa that had occurrence mean of >1% of the total dinoflagellate abundance, accounting for 93% of the total dinoflagellate community: namely Heterocapsa rotundata, Gymnodinium sp., Akashiwo sanguinea, Amoebophrya sp., Euduboscquella sp., Spiniferites ramosus, Dissodinium pseudolunula, Sinophysis sp., Karlodinium veneficum, and Katodinium glaucum. The key dinoflagellate species were well represented at temporally variable levels over an entire year. Heterocapsa rotundata was not significantly affected by water temperature, whereas its dynamics were largely influenced by strong predation pressure, competition, and/or the supplementation of food sources. The growth of Akashiwo sanguinea has been associated with dissolved inorganic phosphorus concentrations in environmental factors, while Euduboscquella sp. showed a significant relationship with Dissodinium pseudolunula and Katodinium glaucum, largely representing a positive association that implies possible parasitism mechanisms. This study demonstrated interactions between key dinoflagellate species and the environments, as well as parasites, predators, and competitors and feeders.