Water mass-driven multiple ecological effects determine the biodiversity and community assembly of microbial flagellates in subtropic-tropic marginal seas of China

Micromonas, a small pigmented flagellate, predominates the nanoflagellate and photosynthetic picoeukaryote communities in the northern South China Sea

“…Moreover, we found a range of 2.72%–75.30% (average of 17.41% for nearshore and 34.58% for offshore) for the proportion of Micromona in PNF sub‐community and a range of 2.12%–22.95% (average of 9.72% for nearshore and 12.16% for offshore) for the proportion of Micromona in total NFs community in this study. This result was comparable with a study about the community composition of microbial flagellates in subtropic–tropic marginal seas of China, which found an average relative abundance of up to 15.04% of Micromona in NFs community in the Minzhe coastal waters (Guo et al, 2023 ). Overall, our results revealed that Micromonas was distributed ubiquitously and contributed significantly to the PPE and NFs assemblages in the northern SCS.…”

“…Results of VPA further revealed the important role of the biotic interactions on the distribution of Micromonas, because the significant explaining environmental variables displayed to be bacteria and PNF, which tend to be the prey and potential predator of Micromonas, respectively (Figure 6). This was consistent with a study in a coastal current in subtropical North Pacific Ocean in summer that observed significant positive correlations among Micromonas, PNFs and bacterioplankton (Guo et al, 2023).…”

“…community in this study. This result was comparable with a study about the community composition of microbial flagellates in subtropic-tropic marginal seas of China, which found an average relative abundance of up to 15.04% of Micromona in NFs community in the Minzhe coastal waters (Guo et al, 2023). Overall, our results revealed that Micromonas was distributed ubiquitously and contributed significantly to the PPE and NFs assemblages in the northern SCS.…”

“…In addition, the significant contribution of the spatial factors to Micromonas assemblage was also found (Figure 6 ; Table 1 ; Table S5 ), indicating the potential impact of dispersal limitation on Micromonas at the large spatial scale in this study. Reports have indicated that microorganisms were not actively and freely dispersed (Hanson et al, 2012 ) and their movements were promoted or restricted by complex water currents depending on their direction, speed, interconnection with other water masses or other hydrological properties (Guo et al, 2023 ), thus the spatial factors also exhibited an important role in shaping the spatial distribution pattern of the microbial community (Hanson et al, 2012 ; Martiny et al, 2006 ). In this study, the vertical distribution pattern is the main characteristic probably due to the water stratification and complex water currents interconnection in summer in the studied area (Hong et al, 2011 ; Jan et al, 2010 ; Li et al, 2014 ).…”

“…Photosynthetic picoeukaryotes (PPE), with cell sizes less than 3 μm and slightly larger than cyanobacteria, have been observed to typically dominate 60%–80% algal biomass and primary production globally (Massana, 2011 ), appearing as the important contributors to picoplankton community with high diversity and cell‐specific production rates in the oceans (Rii et al, 2016 ; Vaulot et al, 2008 ). So far, with the rapid development of DNA sequencing technology and in particular, the application of high‐throughput sequencing (HTS) combined with metabarcoding approaches, studies suggested that the high diversity of NFs and PPEs belonging to several divisions in terms of taxonomy (Guo et al, 2023 ; Moon‐van der Staay et al, 2001 ). This warrants further studies to explore the hidden world of these communities, especially the distribution of the dominant organisms and their significance to the microbial food web, and thus the entire ecosystem (Giner et al, 2016 ; Zhu et al, 2005 ).…”