Reversal of the net dinitrogen gas flux in coastal marine sediments
Reversal of the net dinitrogen gas flux in coastal marine sediments
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DOI：
10.1038/nature05963
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发表时间：
2007-07-12
期刊：
影响因子：
64.8
通讯作者：
Granger, S. L.
中科院分区：
文献类型：
--
作者：
Fulweiler, R. W.;Nixon, S. W.;Granger, S. L.
近几十年来，从陆地和大气到河口和沿海海洋的氮通量大幅增加。观察到的氮负荷增加是由人口增长、城市化、不断扩大的给水和下水道基础设施、化石燃料燃烧和合成化肥消费造成的(1，2)。大多数氮通过河口和大陆架沉积物中的反硝化作用去除，导致养殖富营养化和公海氮污染减少(3，4)。然而，固氮在潮下异养海洋系统中被认为是可以忽略的过程(5)。在这里，我们报道了来自美国纳拉甘西特湾的沉积物岩心数据，这些数据表明，异养海洋沉积物可以从净汇转变为净氮源。中层和岩心培养实验，以及一组年平均叶绿素生产量的历史数据集(6，7)，支持这样的观点，即气候引起的初级生产量的减少导致向底栖生物沉积的有机质减少，并观察到沉积物净氮通量发生逆转。我们的结果表明，一些河口可能不再从水柱中去除氮。相反，氮可以出口到大陆架和开阔的海洋，并可能将人为氮负荷的影响转移到紧邻沿海地区之外。
The flux of nitrogen from land and atmosphere to estuaries and the coastal ocean has increased substantially in recent decades. The observed increase in nitrogen loading is caused by population growth, urbanization, expanding water and sewer infrastructure, fossil fuel combustion and synthetic fertilizer consumption(1,2). Most of the nitrogen is removed by denitrification in the sediments of estuaries and the continental shelf, leading to a reduction in both cultural eutrophication and nitrogen pollution of the open ocean(3,4). Nitrogen fixation, however, is thought to be a negligible process in sub-tidal heterotrophic marine systems(5). Here we report sediment core data from Narragansett Bay, USA, which demonstrate that heterotrophic marine sediments can switch from being a net sink to being a net source of nitrogen. Mesocosm and core incubation experiments, together with a historic data set of mean annual chlorophyll production(6,7), support the idea that a climate-induced decrease in primary production has led to a decrease in organic matter deposition to the benthos and the observed reversal of the net sediment nitrogen flux. Our results suggest that some estuaries may no longer remove nitrogen from the water column. Instead, nitrogen could be exported to the continental shelf and the open ocean and could shift the effect of anthropogenic nitrogen loading beyond the immediate coastal zone.