Predictable and efficient carbon sequestration in the North Pacific Ocean supported by symbiotic nitrogen fixation
Predictable and efficient carbon sequestration in the North Pacific Ocean supported by symbiotic nitrogen fixation
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DOI：
10.1073/pnas.1120312109
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发表时间：
2012-02-07
影响因子：
11.1
通讯作者：
Mahaffey, Claire
中科院分区：
文献类型：
--
作者：
Karl, David M.;Church, Matthew J.;Mahaffey, Claire
大气层和深海的二氧化碳储存库通过物理、化学和生物过程联系在一起。最后一个包括光合作用、颗粒沉降和有机物的再矿化，统称为“生物碳泵”。“在此，我们提出了一个13年（1992-2004年）的沉积物捕获实验的结果，该实验在永久贫营养的北太平洋副热带环流中进行，记录了一个大的，快速的，可预测的夏季（7月15日至8月15日）颗粒物输出到深海（4,000米）的脉冲。夏季输出脉冲（SEP）期间颗粒物的峰值日通量平均为408，283，24.1，1.1和67.5 μ mol.m（-2）.d（-1），分别为总碳，有机碳，氮，磷（PP），和生物硅。SEP约为平均冬季颗粒通量的三倍，并且由于向下运输期间的低矿化导致总碳/PP和有机碳/PP颗粒化学计量比升高（分别为371：1和250：1），因此燃料更有效地固碳。我们的长期观察表明，季节性变化的微生物组合，即夏季增加共生固氮蓝藻与硅藻的生物量和生产力，是突出的SEP的主要原因。经常性SEP是神秘的，因为它是集中在时间，尽管没有任何明显的可预测的刺激或栖息地条件。我们推测，白天长度（光周期）的变化可能是一个重要的环境线索，启动聚合和随后的出口的有机物到深海。
The atmospheric and deep sea reservoirs of carbon dioxide are linked via physical, chemical, and biological processes. The last of these include photosynthesis, particle settling, and organic matter remineralization, and are collectively termed the "biological carbon pump." Herein, we present results from a 13-y (1992-2004) sediment trap experiment conducted in the permanently oligotrophic North Pacific Subtropical Gyre that document a large, rapid, and predictable summertime (July 15-August 15) pulse in particulate matter export to the deep sea (4,000 m). Peak daily fluxes of particulate matter during the summer export pulse (SEP) average 408, 283, 24.1, 1.1, and 67.5 mu mol.m(-2).d(-1) for total carbon, organic carbon, nitrogen, phosphorus (PP), and biogenic silica, respectively. The SEP is approximately threefold greater than mean wintertime particle fluxes and fuels more efficient carbon sequestration because of low remineralization during downward transit that leads to elevated total carbon/PP and organic carbon/PP particle stoichiometry (371:1 and 250:1, respectively). Our long-term observations suggest that seasonal changes in the microbial assemblage, namely, summertime increases in the biomass and productivity of symbiotic nitrogen-fixing cyanobacteria in association with diatoms, are the main cause of the prominent SEP. The recurrent SEP is enigmatic because it is focused in time despite the absence of any obvious predictable stimulus or habitat condition. We hypothesize that changes in day length (photoperiodism) may be an important environmental cue to initiate aggregation and subsequent export of organic matter to the deep sea.