3D intrusions transport active surface microbial assemblages to the dark ocean

• 成果类型: Article
• 署名作者: Freilich, Mara A.; Poirier, Camille; Dever, Mathieu; Alou-Font, Eva; Allen, John; Cabornero, Andrea; Sudek, Lisa; Choi, Chang Jae; Ruiz, Simon; Pascual, Ananda; Farrar, J. Thomas; Johnston, T. M. Shaun; D'Asaro, Eric A.; Worden, Alexandra Z.; Mahadevan, Amala
• 署名单位: University of California System; University of California San Diego; Scripps Institution of Oceanography; Brown University; Brown University; Helmholtz Association; GEOMAR Helmholtz Center for Ocean Research Kiel; Woods Hole Oceanographic Institution; University of California System; University of California Santa Cruz; Consejo Superior de Investigaciones Cientificas (CSIC); ATTITUS Educacao; University of Washington; University of Washington Seattle; Marine Biological Laboratory - Woods Hole
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14194
• DOI: 10.1073/pnas.2319937121
• 发表日期: 2024-05-07
• 关键词: almeria-oran front; eddy-driven subduction; carbon export; time-series; mesoscale subduction; community structure; organic-carbon; phytoplankton; biomass; prochlorococcus

摘要

Subtropical oceans contribute significantly to global primary production, but the fate of the picophytoplankton that dominate in these low - nutrient regions is poorly understood. Working in the subtropical Mediterranean, we demonstrate that subduction of water at ocean fronts generates 3D intrusions with uncharacteristically high carbon, chlorophyll, and oxygen that extend below the sunlit photic zone into the dark ocean. These contain fresh picophytoplankton assemblages that resemble the photic - zone regions where the water originated. Intrusions propagate depth - dependent seasonal variations in microbial assemblages into the ocean interior. Strikingly, the intrusions included dominant biomass contributions from nonphotosynthetic bacteria and enrichment of enigmatic heterotrophic bacterial lineages. Thus, the intrusions not only deliver material that differs in composition and nutritional character from sinking detrital particles, but also drive shifts in bacterial community composition, organic matter processing, and interactions between surface and deep communities. Modeling efforts paired with global observations demonstrate that subduction can flux similar magnitudes of particulate organic carbon as sinking export, but is not accounted for in current export estimates and carbon cycle models. Intrusions formed by subduction are a particularly important mechanism for enhancing connectivity between surface and upper mesopelagic ecosystems in stratified subtropical ocean environments that are expanding due to the warming climate.