Nitrogen isotope dynamics of the Cariaco Basin, Venezuela
Nitrogen isotope dynamics of the Cariaco Basin, Venezuela
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DOI：
10.1029/2003gb002185
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发表时间：
2004-09
影响因子：
5.2
通讯作者：
R. Thunell;D. Sigman;F. Muller‐Karger;Y. Astor;R. Varela
中科院分区：
文献类型：
--
作者：
R. Thunell;D. Sigman;F. Muller‐Karger;Y. Astor;R. Varela
我们报告15 N/14 N测量水柱硝酸盐和铵，下沉颗粒，并从Cariaco盆地，缺氧的海洋盆地委内瑞拉海岸的沉积物。发生在盆地中的水柱反硝化作用只有一个非常小的同位素印记在盆地中的硝酸盐，因为硝酸盐的消耗几乎是完整的积极反硝化水附近的好氧/缺氧界面（275米）。由于没有大的反硝化作用信号，浅层温跃层硝酸盐的δ 15 N为1.35 ‰，显著低于深海硝酸盐的平均δ 15 N（5‰）。这可能是由于硝化作用的新固定的N，无论是发生在盆地内或开放的大西洋沃茨流入Cariaco的窗台。在最深的陷阱（1250米）的下沉通量的15 N/14 N是类似的温跃层硝酸盐，如预期的硝酸盐在表层的完全消耗。此外，海底沉积物的15 N/14 N与下沉通量相似，这在高输出产量、低O2和有机质保存良好的环境中很常见。因此，现代Cariaco盆地记录的15 N/14 N的温跃层硝酸盐，这反过来，可能会记录输入新固定的N到上层海洋，无论是本地或更多的区域起源。
We report 15N/14N measurements of water column nitrate and ammonium, sinking particles, and sediments from the Cariaco Basin, an anoxic marine basin off the coast of Venezuela. Water column denitrification occurring in the basin has only a very small isotopic imprint on nitrate in the basin because nitrate consumption is nearly complete in the actively denitrifying water near the oxic/anoxic interface (∼275 m). Being free of a large denitrification signal, the δ15N of shallow thermocline nitrate is ∼3.5‰, significantly lower than the mean deep ocean nitrate δ15N of 5‰. This may be due to the nitrification of newly fixed N, whether it occurs within the basin or in open Atlantic waters that flow into the Cariaco over the sill. The 15N/14N of the sinking flux in the deepest trap (∼1250 m) is similar to that of thermocline nitrate, as expected given the complete consumption of nitrate in the surface layer. Moreover, the 15N/14N of the seafloor sediment is similar to that of the sinking flux, as is common in environments of high export production, low O2, and good organic matter preservation. Thus the modern Cariaco Basin records the 15N/14N of the thermocline nitrate, which, in turn, may record the input of newly fixed N to the upper ocean, be it local or more regional in origin.