Geographical distribution and driving force of micro-eukaryotes in the seamount sediments along the island arc of the Yap and Mariana trenches

Abstract

The specific topographic characteristics and complex hydrodynamics of seamounts could directly or indirectly affect the distribution and trophic status of microbes. However, little is known about the distribution patterns and associated driving forces of micro-eukaryotes in the deep seamounts. Micro-eukaryotes in the seamount sediments along the island arc of the Yap and Mariana trenches were investigated using high-throughput sequencing and quantitative PCR based on the 18S rRNA gene. Micro-eukaryotic communities from seamounts were clustered together and distinct from those of the depression, which showed comparatively lower diversity, gene abundance, endemic species, and higher proportions of decomposers and parasites. This clear geographical distribution pattern was mainly shaped by the deterministic process, especially environmental (61.63%) and biotic (mainly the unexplained 30.05%) factors, potentially reflecting the seamount effect along the horizontal dimension very likely caused by enclosed circulation cells. Varied community connectivity existed along the summit, flank, and base of different seamounts, and this seamount effect along the vertical dimension might be attributed to the upwelling/downwelling water flows. Prevalence of parasitism and predation for the trophic relationships among micro-eukaryotes would be helpful for adaptation, diversification, and maintaining the ecological balance in this extreme biosphere. This study provides insights into the ecological patterns, assembling processes, and species interactions underlying the dynamics of micro-eukaryotic communities across a series of seamounts with a comparison of the depression and would expand our understanding of seamount effects on the deep-sea ecosystems. IMPORTANCE A distinct distribution pattern was shaped by a deterministic process. Enhanced vertical connectivity expanded the previous understanding of seamount effects. Parasitism and predation were prevalent in the seamounts.