Models of oxic respiration, denitrification and sulfate reduction in zones of coastal upwelling
Models of oxic respiration, denitrification and sulfate reduction in zones of coastal upwelling
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DOI：
10.1016/j.gca.2006.07.023
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发表时间：
2006-12-01
影响因子：
5
通讯作者：
Canfield, D. E.
中科院分区：
文献类型：
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作者：
Canfield, D. E.
沿海上升流区支撑着海洋中一些最高的初级生产力。这种有机物的沉降和随后的分解会促进氧气消耗。在东部热带北太平洋、南太平洋和阿拉伯海，形成大片缺氧水域，其中通过反硝化和厌氧氨氧化产生的大量 N-2 约占海洋领域固定氮总损失的 1/3。奇怪的是，尽管这些水域进行了广泛的反硝化，但完全去除硝酸盐和硫酸盐还原的情况却极其罕见。这里构建了一个简单的盒子模型来重现沿海上升流区域碳、氧和养分循环的动态。该模型由五个盒子构成，盒子之间的水通过垂直和水平混合和平流进行交换。这些主要的物理驱动因素控制着系统的动态。该模型表明，在没有固氮作用的情况下，沿海上升流系统中的缺氧水域不会变得不含硝酸盐。这是因为硝酸盐是控制初级生产的限制性养分，如果硝酸盐浓度太低，初级生产率就会下降，从而降低通过 N2 生产去除硝酸盐的速率。然而，通过固氮，硝酸盐可能会完全耗尽，硫酸盐也会随之减少。这种情况在沿海上升流区域极为罕见，可能是因为固氮细菌在高营养、浑浊的水域中无法繁衍生息，而这些区域通常是这样的。最后，这里预测，无论 N2 的产生是由厌氧氨氧化（anammox）还是典型的异养反硝化主导，上升流系统的化学反应都会以类似的方式发展。 (c) 2006 Elsevier Inc. 保留所有权利。
Coastal upwelling zones support some of the highest rates of primary production in the oceans. The settling and subsequent decomposition of this organic matter promotes oxygen depletion. In the Eastern tropical North and South Pacific and the Arabian Sea, large tracts of anoxic water develop, where intensive N-2 production through denitrification and anammox accounts for about 1/3 of the total loss of fixed nitrogen in the marine realm. It is curious that despite extensive denitrification in these waters, complete nitrate removal and the onset of sulfate reduction is extremely rare. A simple box model is constructed here to reproduce the dynamics of carbon, oxygen and nutrient cycling in coastal upwelling zones. The model is constructed with five boxes, where water is exchanged between the boxes by vertical and horizontal mixing and advection. These primary physical drivers control the dynamics of the system. The model demonstrates that in the absence of nitrogen fixation, the anoxic waters in a coastal upwelling system will not become nitrate free. This is because nitrate is the limiting nutrient controlling primary production, and if nitrate concentration becomes too low, primary production rate drops and this reduces rates of nitrate removal through N2 production. With nitrogen fixation, however, complete nitrate depletion can occur and sulfate reduction will ensue. This situation is extremely rare in coastal upwelling zones, probably because nitrogen-fixing bacteria do not prosper in the high nutrient, turbid waters as typically in these areas. Finally, it is predicted here that the chemistry of the upwelling system will develop in a similar matter regardless whether N2 production is dominated by anaerobic ammonium oxidation (anammox) or canonical heterotrophic denitrification. (c) 2006 Elsevier Inc. All rights reserved.