The nitrogen isotope biogeochemistry of sinking particles from the margin of the Eastern North Pacific
The nitrogen isotope biogeochemistry of sinking particles from the margin of the Eastern North Pacific
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DOI：
10.1016/s0967-0637(98)00084-3
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发表时间：
1999-04-01
影响因子：
2.4
通讯作者：
Francois, R
中科院分区：
文献类型：
--
作者：
Altabet, MA;Pilskaln, C;Francois, R
在北太平洋东部沿着边缘的三个区域：蒙特利湾，圣佩德罗盆地，和加州湾（卡门和瓜伊马斯盆地）的时间序列沉积物捕获样品，溶解NO3-和表层沉积物的氮同位素组成进行了测定。复杂的物理制度存在于所有三个领域，每个季节性的沿海涌升流的影响。然而，沉积物捕获材料显然记录了新的氮源的同位素组成，因为平均三角洲（15）N一般是无法区分的三角洲（15）N值为地下NO3-。表层沉积物也与沉积物圈闭的平均三角洲（15）N值非常相似，在千分之一以内。这种陷阱材料和沉积物之间的三角洲（15）N的差异远小于以前观察到的深海差异为千分之四。更好的有机质保存在我们的边缘网站是一个可能的解释，这可能是由于低的底部O-2浓度或较高的有机质输入到沉积物。所有站点的亚真光层NO3-（千分之8-10）的三角洲（15）N显著高于海洋平均值（千分之4.5-5）。这种同位素富集是亚氧地下沃茨（加州湾）或受反硝化作用影响的水（蒙特雷湾和圣佩德罗盆地）向北迁移的结果。因此，我们的研究结果表明，downcore三角洲（15）N数据，根据站点的位置，将记录反硝化作用的强度和运输的同位素签名沿着加州的边缘。三角洲（15）N的沉积物捕集器的时间变化确实出现响应的上升流或对流注入NO3-的表面沃茨作为同位素分馏浮游植物吸收过程中的结果。总的来说，虽然，NO3-注入，三角洲（15）N，和通量之间的耦合是松散的比以前观察到的开放的海洋，最有可能的结果较小的时间/空间尺度的事件。III在加州湾，冬季对流混合/上升流确实产生了明显的Delta（15）N最小值，与粒子通量最大值同时发生。当这些冬季三角洲（15）N最小值未能发生在厄尔尼诺条件下，年际变化是明显的。南方涛动指数（SOI）距平与年平均三角洲（15）N之间存在正相关关系。一种解释是水文变化改变了透光带NO3-的三角洲（15）N。(C)1999 Elsevier Science Ltd.保留所有权利。
The nitrogen isotopic composition of time-series sediment trap samples, dissolved NO3- and surficial sediments was determined in three regions along the margin of the eastern North Pacific: Monterey Bay, San Pedro Basin, and the Gulf of California (Carmen and Guaymas Basins). Complex physical regimes are present in all three areas, and each is influenced seasonally by coastal upwelling. Nevertheless, sediment trap material evidently records the isotopic composition of new nitrogen sources, since average delta(15)N is generally indistinguishable from delta(15)N values for subsurface NO3-. Surficial sediments are also very similar to the average delta(15)N value of the sediment traps, being within 1 parts per thousand. This difference in delta(15)N between trap material and sediment is much less than the previously observed 4 parts per thousand, difference for the deep sea. Better organic matter preservation at our margin sites is a likely explanation, which may be due to either low bottom O-2 concentrations or higher organic matter input to the sediments. All sites have delta(15)N for sub-euphotic zone NO3- (8-10 parts per thousand) substantially elevated from the oceanic average (4.5-5 parts per thousand). This isotopic enrichment is a result of denitrification in suboxic subsurface waters (Gulf of California) or northward transport of denitrification influenced water (Monterey Bay and San Pedro Basin). Our results therefore suggest that downcore delta(15)N data, depending on site location, would record the intensity of denitrification and the transport of its isotopic signature along the California margin. Temporal variations in delta(15)N for the sediment traps do appear to respond to upwelling or convective injections of NO3- to surface waters as a result of isotopic fractionation during phytoplankton uptake. Overall, though, the coupling between NO3- injection, delta(15)N, and flux is looser than previously observed for the open-ocean, most likely the result of the smaller time/space scales of the events. III the Gulf of California, wintertime convective mixing/upwelling does produce distinct delta(15)N minima co-occurring with particle flux maxima. Interannual variations are apparent in this region when these wintertime delta(15)N minima fail to occur during El Nino conditions. There appears to be a positive relationship between the Southern Oscillation Index (SOI) anomaly and annual average delta(15)N. One explanation calls for hydrographic changes altering the delta(15)N of subeuphotic zone NO3-. (C) 1999 Elsevier Science Ltd. All rights reserved.