Maniscalco Michael A, Brzezinski Mark A, Lampe Robert H, Cohen Natalie R, McNair Heather M, Ellis Kelsey A, Brown Matthew, Till Claire P, Twining Benjamin S, Bruland Kenneth W, Marchetti Adrian, Thamatrakoln Kimberlee
Marine Science Institute and The Department of Ecology Evolution and Marine Biology, University of California, Santa Barbara, CA, USA.
Integrative Oceanography Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.
ISME Commun. 2022 Jul 9;2(1):57. doi: 10.1038/s43705-022-00136-1.
In the California Current Ecosystem, upwelled water low in dissolved iron (Fe) can limit phytoplankton growth, altering the elemental stoichiometry of the particulate matter and dissolved macronutrients. Iron-limited diatoms can increase biogenic silica (bSi) content >2-fold relative to that of particulate organic carbon (C) and nitrogen (N), which has implications for carbon export efficiency given the ballasted nature of the silica-based diatom cell wall. Understanding the molecular and physiological drivers of this altered cellular stoichiometry would foster a predictive understanding of how low Fe affects diatom carbon export. In an artificial upwelling experiment, water from 96 m depth was incubated shipboard and left untreated or amended with dissolved Fe or the Fe-binding siderophore desferrioxamine-B (+DFB) to induce Fe-limitation. After 120 h, diatoms dominated the communities in all treatments and displayed hallmark signatures of Fe-limitation in the +DFB treatment, including elevated particulate Si:C and Si:N ratios. Single-cell, taxon-resolved measurements revealed no increase in bSi content during Fe-limitation despite higher transcript abundance of silicon transporters and silicanin-1. Based on these findings we posit that the observed increase in bSi relative to C and N was primarily due to reductions in C fixation and N assimilation, driven by lower transcript expression of key Fe-dependent genes.
在加利福尼亚洋流生态系统中，溶解铁（Fe）含量低的上升流海水会限制浮游植物的生长，改变颗粒物和溶解的大量营养素的元素化学计量。与颗粒有机碳（C）和氮（N）相比，铁限制的硅藻可使生物源二氧化硅（bSi）含量增加2倍以上，鉴于基于二氧化硅的硅藻细胞壁具有压载性质，这对碳输出效率有影响。了解这种细胞化学计量变化的分子和生理驱动因素，将有助于对低铁如何影响硅藻碳输出形成预测性的理解。在一项人工上升流实验中，将来自96米深度的海水在船上进行培养，不进行处理或添加溶解铁或铁结合铁载体去铁胺-B（+DFB）以诱导铁限制。120小时后，硅藻在所有处理的群落中占主导地位，并且在+DFB处理中表现出铁限制的标志性特征，包括颗粒Si:C和Si:N比率升高。单细胞、分类群解析测量结果显示，尽管硅转运蛋白和硅蛋白-1的转录本丰度较高，但在铁限制期间bSi含量并未增加。基于这些发现，我们认为观察到的bSi相对于C和N的增加主要是由于关键铁依赖基因的转录表达降低导致的碳固定和氮同化减少。
