Integrative Oceanography Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.
Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
ISME J. 2019 Dec;13(12):2984-2997. doi: 10.1038/s41396-019-0489-6. Epub 2019 Aug 22.
Despite generally low primary productivity and diatom abundances in oligotrophic subtropical gyres, the North Atlantic Subtropical Gyre (NASG) exhibits significant diatom-driven carbon export on an annual basis. Subsurface pulses of nutrients likely fuel brief episodes of diatom growth, but the exact mechanisms utilized by diatoms in response to these nutrient injections remain understudied within near-natural settings. Here we simulated delivery of subsurface nutrients and compare the response among eukaryotic phytoplankton using a combination of physiological techniques and metatranscriptomics. We show that eukaryotic phytoplankton groups exhibit differing levels of transcriptional responsiveness and expression of orthologous genes in response to release from nutrient limitation. In particular, strategies for use of newly delivered nutrients are distinct among phytoplankton groups. Diatoms channel new nitrate to growth-related strategies while physiological measurements and gene expression patterns of other groups suggest alternative strategies. The gene expression patterns displayed here provide insights into the cellular mechanisms that underlie diatom subsistence during chronic nitrogen-depleted conditions and growth upon nutrient delivery that can enhance carbon export from the surface ocean.
尽管贫营养亚热带 Gyre 中的初级生产力和硅藻丰度通常较低，但北大西洋亚热带 Gyre（NASG）在每年都会表现出显著的硅藻驱动的碳输出。底层营养物质的脉冲可能为硅藻的短暂生长提供动力，但硅藻在应对这些营养物质注入时所利用的确切机制在近自然环境中仍研究不足。在这里，我们使用生理技术和宏转录组学相结合的方法模拟了底层营养物质的输送，并比较了真核浮游植物的反应。我们发现，真核浮游植物群体在响应营养限制释放时，表现出不同程度的转录反应性和同源基因的表达。特别是，浮游植物群体之间利用新输送的营养物质的策略是不同的。硅藻将新的硝酸盐输送到与生长相关的策略，而其他群体的生理测量和基因表达模式表明存在替代策略。这里显示的基因表达模式为硅藻在慢性氮缺乏条件下生存和在营养物质输送时生长的细胞机制提供了深入了解，这可以增强从表层海洋中输出的碳。
