Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30, Gothenburg, Sweden.
Department of Ecology, Environment and Plant Sciences, Stockholm University, Svante Arrhenius Väg 21A, SE-10691, Stockholm, Sweden.
Nat Commun. 2018 Aug 3;9(1):3046. doi: 10.1038/s41467-018-05149-w.
Chain-forming diatoms are key CO-fixing organisms in the ocean. Under turbulent conditions they form fast-sinking aggregates that are exported from the upper sunlit ocean to the ocean interior. A decade-old paradigm states that primary production in chain-forming diatoms is stimulated by turbulence. Yet, direct measurements of cell-specific primary production in individual field populations of chain-forming diatoms are poorly documented. Here we measured cell-specific carbon, nitrate and ammonium assimilation in two field populations of chain-forming diatoms (Skeletonema and Chaetoceros) at low-nutrient concentrations under still conditions and turbulent shear using secondary ion mass spectrometry combined with stable isotopic tracers and compared our data with those predicted by mass transfer theory. Turbulent shear significantly increases cell-specific C assimilation compared to still conditions in the cells/chains that also form fast-sinking, aggregates rich in carbon and ammonium. Thus, turbulence simultaneously stimulates small-scale biological CO assimilation and large-scale biogeochemical C and N cycles in the ocean.
链状硅藻是海洋中固定 CO2 的关键生物。在动荡的条件下，它们会形成快速下沉的聚集体，从阳光充足的上层海洋中被输送到海洋内部。一个十年前的范式指出，链状硅藻的初级生产力受到动荡的刺激。然而，对于链状硅藻的现场种群的细胞特异性初级生产力的直接测量，文献记录很少。在这里，我们使用二次离子质谱联用稳定同位素示踪剂，在低营养浓度下的静止和动荡剪切条件下，测量了两种链状硅藻（Skeletonema 和 Chaetoceros）的细胞特异性碳、硝酸盐和铵盐的同化作用，并将我们的数据与质量传递理论的预测进行了比较。与静止条件相比，动荡剪切显著增加了细胞/链中的细胞特异性 C 同化作用，这些细胞/链也形成了富含碳和铵的快速下沉聚集体。因此，动荡同时刺激了海洋中小尺度的生物 CO 同化作用和大尺度的生物地球化学 C 和 N 循环。
