Microscale dynamics promote segregated denitrification in diatom aggregates sinking slowly in bulk oxygenated seawater
Microscale dynamics promote segregated denitrification in diatom aggregates sinking slowly in bulk oxygenated seawater
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DOI：
10.1038/s43247-023-00935-x
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发表时间：
2023-07-28
影响因子：
7.9
通讯作者：
Babbin，Andrew R.
中科院分区：
文献类型：
--
作者：
Ciccarese，Davide;Tantawi，Omar;Babbin，Andrew R.
下沉的海洋颗粒驱动生物泵，自然地从大气中封存碳。尽管尺寸很小，但颗粒的分隔性质促进了细菌定殖者的强烈局部代谢活动。然而，促进反硝化作用发生的机制仍有待确定，反硝化作用是一种在氧气受到限制时发生的新陈代谢。在这里，我们通过实验证明，由海洋硅藻（全球碳出口的重要初级生产者）组成的缓慢下沉的聚集体即使在通常被认为排除厌氧代谢的大量含氧水中也支持主动反硝化。反硝化发生在分布在整个颗粒和颗粒边界微米范围内的缺氧微位点，荧光报告细菌显示，由于硝酸盐和亚硝酸盐的分离异化还原，亚硝酸盐可以释放到水柱中。通过检查完整和破碎的硅藻作为有机来源，我们发现缓慢渗漏的细胞促进更多细菌生长，使颗粒具有较低的氧气，并且通常支持更大的反硝化作用。
Sinking marine particles drive the biological pump that naturally sequesters carbon from the atmosphere. Despite their small size, the compartmentalized nature of particles promotes intense localized metabolic activity by their bacterial colonizers. Yet the mechanisms promoting the onset of denitrification, a metabolism that arises once oxygen is limiting, remain to be established. Here we show experimentally that slow sinking aggregates composed of marine diatoms—important primary producers for global carbon export—support active denitrification even among bulk oxygenated water typically thought to exclude anaerobic metabolisms. Denitrification occurs at anoxic microsites distributed throughout a particle and within microns of a particle’s boundary, and fluorescence-reporting bacteria show nitrite can be released into the water column due to segregated dissimilatory reduction of nitrate and nitrite. Examining intact and broken diatoms as organic sources, we show slowly leaking cells promote more bacterial growth, allow particles to have lower oxygen, and generally support greater denitrification.