ABSTRACT: Marine microbial eukaryotes play crucial roles in water-column ecosystems; however, there are regional gaps in the investigation of natural microbial eukaryote communities, and uncertainties concerning their distribution persevere. This study combined 18S rRNA metabarcoding, biomass measurements and statistical analyses of multiple environmental variables to examine the distribution of planktonic microbial eukaryotes at different sites and water layers in the ultra-oligotrophic Eastern Mediterranean Sea (Western Levantine Basin). Our results showed that microbial eukaryotic communities were structured by depth. In surface waters, different sites shared high percentages of molecular operational taxonomic units (MOTUs), but this was not the case for deep-sea communities (≥1000 m). Plankton biomass was significantly different among sites, implying that communities of a similar composition may not support the same activity or population size. The deep-sea communities showed high percentages of unassigned MOTUs, highlighting the sparsity of the existing information on deep-sea plankton eukaryotes. Water temperature and dissolved organic matter significantly affected community distribution. Micro-eukaryotic distribution was additionally affected by the nitrogen to phosphorus ratio and viral abundance, while nano- and pico-communities were affected by zooplankton. The present study explores microbial plankton eukaryotes in their natural oligotrophic environment and highlights that, even within restricted oceanic areas, marine plankton may follow distribution patterns that are largely controlled by environmental variables.

中文翻译：

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超营养化东地中海真核微生物浮游生物的组成和分布模式

摘要：海洋微生物真核生物在水柱生态系统中起着至关重要的作用。然而，在研究天然微生物真核生物群落方面存在地区差距，并且关于其持久分布的不确定性。这项研究结合了18S rRNA元条形码，生物量测量和多个环境变量的统计分析，以检查超营养化东地中海（西黎凡特盆地）不同地点和水层的浮游微生物真核生物的分布。我们的结果表明，微生物的真核生物群落是由深度构成的。在地表水中，不同的地点共享较高百分比的分子操作分类单位（MOTU），但对于深海群落（≥1000m）则不是这样。地点之间的浮游生物量显着不同，暗示组成相似的社区可能不支持相同的活动或人口规模。深海社区显示出未分配MOTU的百分比很高，突显了有关深海浮游生物真核生物的现有信息的稀疏性。水温和溶解有机物显着影响社区分布。氮磷比和病毒丰度还影响微真核生物的分布，而浮游动物则影响纳米和微微社区。本研究探索了天然浮游生物环境中的微生物浮游生物真核生物，并着重指出，即使在有限的海洋区域内，海洋浮游生物也可能遵循受环境变量控制的分布模式。