Vertical and horizontal distribution of fluorescent dissolved organic matter in the Southern Ocean
Vertical and horizontal distribution of fluorescent dissolved organic matter in the Southern Ocean
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DOI：
10.1016/j.marchem.2007.05.004
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发表时间：
2007-08
期刊：
影响因子：
3
通讯作者：
Y. Yamashita;A. Tsukasaki;Tamihito Nishida;E. Tanoue
中科院分区：
文献类型：
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作者：
Y. Yamashita;A. Tsukasaki;Tamihito Nishida;E. Tanoue
利用320 nm激发光和420 nm发射光的荧光强度测定了南大洋亚热带、亚热带、极地锋区和南极区2个断面上9个站位的溶解有机物（FDOM）的垂直和水平分布。荧光强度的所有垂直分布图都表明，表层沃茨的水平最低，在中层沃茨（约2000米）随着深度的增加而增加，然后从那里到底部停留在一个相对较窄的范围内。FDOM的垂直分布与营养盐相似，但对溶解氧不利。在低于最低温度的地下水的水柱中（分温沃茨）和其他海区冬季混合层以下的荧光强度，确定了整个研究区的荧光强度与营养盐浓度和表观氧利用率（AOU）的关系，并发现荧光强度和营养浓度之间存在显著的线性相关性（磷酸盐和硝酸盐+亚硝酸盐分别为r= 0.70和0.71）和AOU（r=0.91）。从荧光强度与AOU的相关系数来看，南大洋中的FDOM是由有机质的生物氧化作用原位形成的。在中等深度的沃茨，营养物的再生/氧气的消耗/FDOM的形成是活跃的。然而，荧光强度与营养盐和AOU之间的相关性在中层水团，亚南极模式水（SAMW）和南极中层水（AAIW）是不同的，这表明负责FDOM形成的有机质的来源是不同的。SAMW中相当数量的FDOM被认为是由DOM的矿化作用以及沉降颗粒有机物产生的，而DOM对AAIW中FDOM的形成不太负责。
The vertical and horizontal distribution of fluorescent dissolved organic matter (FDOM), determined by fluorescence intensity at 320 nm excitation and 420 nm emission, were clarified in nine stations on two transects at the Southern Ocean, including a subtropical, subantarctic, polar frontal and Antarctic zone. All vertical profiles of fluorescence intensity showed that levels were lowest in the surface waters, increased with increasing the depth in mid-depth waters (∼2000 m), and then stayed within a relatively narrow range from there to the bottom. Such vertical profiles of FDOM were similar to those of nutrients, but were adverse to dissolved oxygen. In water columns below the temperature-minimum subsurface water (dichothermal waters) in the Antarctic zone and below the winter mixed layer in the other zones, we determined the relationships of fluorescence intensity to concentrations of nutrients and apparent oxygen utilization (AOU) over the entire area of the present study, and found significant linear correlations between the levels of fluorescence intensity and nutrient concentrations (r= 0.70 and 0.71 for phosphate and nitrate+nitrite, respectively) and AOU (r=0.91). From the strong correlation coefficient between fluorescence intensity and AOU, we concluded that FDOM in the Southern Ocean is formed in situ via the biological oxidation of organic matter. The regeneration of the nutrients/consumption of the oxygen/formation of FDOM was active in mid-depth waters. However, the correlations between fluorescence intensities and nutrients and AOU were different in the mid-depth water masses, Subantarctic Mode Water (SAMW), and Antarctic Intermediate Water (AAIW), indicating that the sources of organic matter responsible for FDOM formation were different. A considerable amount of FDOM in the SAMW is thought to be produced by the remineralization of DOM in addition to sinking particulate organic matter, while DOM is less responsible for FDOM formation in the AAIW.