Export of terrigenous dissolved organic matter in a broad continental shelf
Export of terrigenous dissolved organic matter in a broad continental shelf
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DOI：
10.1002/lno.10528
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发表时间：
2017-07-01
影响因子：
4.5
通讯作者：
Dittmar, Thorsten
中科院分区：
文献类型：
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作者：
Medeiros, Patricia M.;Babcock-Adams, Lydia;Dittmar, Thorsten
陆源溶解有机物(DOM)从河流向海洋的输出在碳循环中起着重要作用。2014年对6个研究航次的观测被用来描述南大西洋浅海和宽阔陆架陆源DOM的季节演变。虽然具有强烈陆源分子、光学和同位素特征的DOM在年初仅限于沿海带，但具有陆源DOM的羽流在晚春进一步延伸到陆架断裂。这一陆源DOM的离岸输送与地表Ekman层的风驱动平流是一致的。在大约1个月的时间尺度上，可追踪的河流DOM化合物大多对生物降解和光降解具有抵抗力，它们在春季河流流量高峰后在陆架上的相对丰度的下降与由于风驱动混合引起的海水夹带对河流羽流的稀释是一致的。光学吸光度测量和超高分辨质谱学数据的比较表明，在275-295 nm范围内，可以使用发色DOM的光谱斜率系数来估计SAB中具有河流特征的DOM池的比例。这一发现为以高空间分辨率观测SAB陆架上河流DOM的分布和利用遥感方法提供了可能性，这是量化陆架-斜坡交换和陆源DOM在陆架海中命运的关键一步。
Export of terrigenous dissolved organic matter (DOM) from rivers to the ocean plays an important role in the carbon cycle. Observations from six research cruises in 2014 were used to characterize the seasonal evolution of terrigenous DOM in the shallow and broad South Atlantic Bight (SAB) shelf. While DOM with a strong terrigenous molecular, optical and isotopic signature was restricted to a coastal band early in the year, a plume with terrigenous DOM extended further to the shelf break in late spring. The offshore transport of this terrigenous DOM was consistent with wind-driven advection in a surface Ekman layer. On time scales spanning about 1 month, the traceable riverine DOM compounds were mostly resistant to bio- and photo-degradation, and the decrease in their relative abundance over the shelf following peak river discharge during spring was consistent with dilution of the river plume due to entrainment of oceanic water associated with wind-driven mixing. Comparisons between optical absorbance measurements and ultrahigh resolution mass spectrometry data revealed that the fraction of the DOM pool with a riverine signature in the SAB can be estimated using the spectral slope coefficient of chromophoric DOM in the 275-295 nm range. This finding opens up the possibility of observing the distribution of riverine DOM on the SAB shelf in high spatial resolution and by using remote sensing methods, a crucial step for quantifying shelf-slope exchange and the fate of terrigenous DOM in shelf seas.