Lamont-Doherty Earth Observatory, Columbia University, New York, NY, USA.
American Museum of Natural History, New York, NY, USA.
Sci Rep. 2021 Aug 10;11(1):16200. doi: 10.1038/s41598-021-95676-2.
Small pigmented eukaryotes (⩽ 5 µm) are an important, but overlooked component of global marine phytoplankton. The Amazon River plume delivers nutrients into the oligotrophic western tropical North Atlantic, shades the deeper waters, and drives the structure of microphytoplankton (> 20 µm) communities. For small pigmented eukaryotes, however, diversity and distribution in the region remain unknown, despite their significant contribution to open ocean primary production and other biogeochemical processes. To investigate how habitats created by the Amazon river plume shape small pigmented eukaryote communities, we used high-throughput sequencing of the 18S ribosomal RNA genes from up to five distinct small pigmented eukaryote cell populations, identified and sorted by flow cytometry. Small pigmented eukaryotes dominated small phytoplankton biomass across all habitat types, but the population abundances varied among stations resulting in a random distribution. Small pigmented eukaryote communities were consistently dominated by Chloropicophyceae (0.8-2 µm) and Bacillariophyceae (0.8-3.5 µm), accompanied by MOCH-5 at the surface or by Dinophyceae at the chlorophyll maximum. Taxonomic composition only displayed differences in the old plume core and at one of the plume margin stations. Such results reflect the dynamic interactions of the plume and offshore oceanic waters and suggest that the resident small pigmented eukaryote diversity was not strongly affected by habitat types at this time of the year.
小型有色真核生物（⩽5 µm）是全球海洋浮游植物的一个重要但被忽视的组成部分。亚马逊河羽流将营养物质输送到贫营养的西热带北大西洋，为深层水域遮荫，并驱动着微浮游植物（>20 µm）群落的结构。然而，对于小型有色真核生物，尽管它们对开阔海域初级生产力和其他生物地球化学过程有重要贡献，但该地区的多样性和分布仍不清楚。为了研究亚马逊河羽流所创造的生境如何塑造小型有色真核生物群落，我们使用高通量测序技术对通过流式细胞术鉴定和分选的多达五个不同的小型有色真核细胞群体的 18S 核糖体 RNA 基因进行了测序。小型有色真核生物在所有生境类型中都主导着小型浮游植物生物量，但由于各站位的种群丰度不同，导致其呈随机分布。小型有色真核生物群落始终由绿藻门（0.8-2 µm）和硅藻门（0.8-3.5 µm）主导，同时在表层有 MOCH-5，在叶绿素最大值处有甲藻。分类组成仅在老羽流核心和羽流边缘的一个站位中存在差异。这些结果反映了羽流和外海海水的动态相互作用，并表明此时此地的居留小型有色真核生物多样性并未受到生境类型的强烈影响。
