Sources and transport of dissolved and particulate organic carbon in the Mississippi River estuary and adjacent coastal waters of the northern Gulf of Mexico
Sources and transport of dissolved and particulate organic carbon in the Mississippi River estuary and adjacent coastal waters of the northern Gulf of Mexico
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DOI：
10.1016/j.marchem.2004.02.014
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发表时间：
2004-10
期刊：
影响因子：
3
通讯作者：
Xuchen Wang;Robert F. Chen;G. Gardner
中科院分区：
文献类型：
--
作者：
Xuchen Wang;Robert F. Chen;G. Gardner
在2000年6月的低流量季节和2001年4月的高流量季节，对从密西西比河下游和Atchafalaya河以及邻近的墨西哥湾北方沿海沃茨采集的样品进行了溶解有机碳（DOC）、DOC和颗粒有机碳（POC）的稳定碳同位素（δ 13 C）组成以及POC的元素C/N比的测定。这些同位素和C/N的结果结合DOC测量被用来评估的来源和运输的陆地有机物从密西西比河和Atchafalaya河的沿海地区在北方墨西哥湾。两条河流携带的POC（−23.8‰ ~ −26.8‰）和DOC（−25.0‰ ~ −29.0‰）的δ 13 C值均比近海沃茨样品的δ 13 C值亏损。表层沃茨中POC和DOC的δ 13 C分布具有明显的季节变化。淡水排放和水平混合对陆源POC和DOC的分布和输送起着重要作用。结果表明，在混合过程中，特别是在中盐度范围内，POC和DOC均表现出非保守性行为。基于简单的双端元混合模型，将测量的DOC-δ 13 C与计算的保守同位素混合曲线进行比较，表明在中高盐度沃茨水中存在显着的原位产生的海洋来源的DOC，这与我们的原位结果一致。叶绿素a测量。DOC-δ 13 C数据表明，陆源DOC的去除主要发生在高盐度（>25）的沃茨中。我们的研究表明，中高盐度（10-30）范围内的有机碳的传输和循环在密西西比河河口的最动态区。同位素和元素组成的变化沿着与DOC和POC浓度的变化表明，本地生产，细菌利用，和光氧化都可以发挥重要作用，在墨西哥湾北方和这些个别过程的调节和去除陆地DOC是必要的进一步研究。
Dissolved organic carbon (DOC), stable carbon isotopic (δ13C) compositions of DOC and particulate organic carbon (POC), and elemental C/N ratios of POC were measured for samples collected from the lower Mississippi and Atchafalaya rivers and adjacent coastal waters in the northern Gulf of Mexico during the low flow season in June 2000 and high flow season in April 2001. These isotopic and C/N results combined with DOC measurements were used to assess the sources and transport of terrestrial organic matter from the Mississippi and Atchafalaya rivers to the coastal region in the northern Gulf of Mexico. δ13C values of both POC (−23.8‰ to −26.8‰) and DOC (−25.0‰ to −29.0‰) carried by the two rivers were more depleted than the values measured for the samples collected in the offshore waters. Strong seasonal variations in δ13C distributions were observed for both POC and DOC in the surface waters of the region. Fresh water discharge and horizontal mixing played important roles in the distribution and transport of terrestrial POC and DOC offshore. Our results indicate that both POC and DOC exhibited non-conservative behavior during the mixing especially in the mid-salinity range. Based on a simple two end-member mixing model, the comparison of the measured DOC-δ13C with the calculated conservative isotopic mixing curve indicated that there was a significant in situ production of marine-derived DOC in the mid- to high-salinity waters consistent with our in situ chlorophyll-a measurements. Our DOC-δ13C data suggest that a removal of terrestrial DOC mainly occurred in the high-salinity (>25) waters during the mixing. Our study indicates that the mid- to high- (10–30) salinity range was the most dynamic zone for organic carbon transport and cycling in the Mississippi River estuary. Variability in isotopic and elemental compositions along with variability in DOC and POC concentrations suggest that autochthonous production, bacterial utilization, and photo-oxidation could all play important roles in regulating and removing terrestrial DOC in the northern Gulf of Mexico and further study of these individual processes is warranted.