Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Department of Earth Science, University of Southern California, Los Angeles, CA, USA.
Nat Microbiol. 2021 Feb;6(2):173-186. doi: 10.1038/s41564-020-00814-7. Epub 2021 Jan 4.
Marine microeukaryotes play a fundamental role in biogeochemical cycling through the transfer of energy to higher trophic levels and vertical carbon transport. Despite their global importance, microeukaryote physiology, nutrient metabolism and contributions to carbon cycling across offshore ecosystems are poorly characterized. Here, we observed the prevalence of dinoflagellates along a 4,600-km meridional transect extending across the central Pacific Ocean, where oligotrophic gyres meet equatorial upwelling waters rich in macronutrients yet low in dissolved iron. A combined multi-omics and geochemical analysis provided a window into dinoflagellate metabolism across the transect, indicating a continuous taxonomic dinoflagellate community that shifted its functional transcriptome and proteome as it extended from the euphotic to the mesopelagic zone. In euphotic waters, multi-omics data suggested that a combination of trophic modes were utilized, while mesopelagic metabolism was marked by cytoskeletal investments and nutrient recycling. Rearrangement in nutrient metabolism was evident in response to variable nitrogen and iron regimes across the gradient, with no associated change in community assemblage. Total dinoflagellate proteins scaled with particulate carbon export, with both elevated in equatorial waters, suggesting a link between dinoflagellate abundance and total carbon flux. Dinoflagellates employ numerous metabolic strategies that enable broad occupation of central Pacific ecosystems and play a dual role in carbon transformation through both photosynthetic fixation in the euphotic zone and remineralization in the mesopelagic zone.
海洋微型真核生物通过将能量传递给更高营养级和垂直碳运输，在生物地球化学循环中发挥着基础性作用。尽管它们具有全球性的重要性，但微型真核生物的生理学、营养代谢以及对近海生态系统碳循环的贡献仍未得到充分认识。在这里，我们沿着一条 4600 公里的南北向剖面观察到了甲藻的流行，这条剖面延伸穿过中太平洋，那里的贫营养旋流与富含大量营养但溶解铁含量低的赤道上升流相遇。综合多组学和地球化学分析为跨剖面的甲藻代谢提供了一个窗口，表明甲藻的连续分类群群落随着从真光层向中层带的延伸，其功能转录组和蛋白质组发生了变化。在真光层水域，多组学数据表明，多种营养模式被同时利用，而中层带的代谢则以细胞骨架投资和营养物质再循环为特征。在整个梯度中，氮和铁的变化对营养物质代谢的重新排列是明显的，而群落组合没有变化。总甲藻蛋白与颗粒碳输出呈正相关，在赤道水域两者都升高，这表明甲藻丰度与总碳通量之间存在联系。甲藻采用了多种代谢策略，使其能够广泛占领中太平洋生态系统，并通过在真光层进行光合作用固定和在中层带进行再矿化来发挥碳转化的双重作用。
