Source partitioning of oxygen‐consuming organic matter in the hypoxic zone of the Chesapeake Bay
Source partitioning of oxygen‐consuming organic matter in the hypoxic zone of the Chesapeake Bay
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DOI：
10.1002/lno.11419
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发表时间：
2020-03
影响因子：
4.5
通讯作者：
Jianzhong Su;W. Cai;J. Brodeur;N. Hussain;Baoshan Chen;J. Testa;K. M. Scaboo;D. Jaisi;Qiang Li;M. Dai;J. Cornwell
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文献类型：
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作者：
Jianzhong Su;W. Cai;J. Brodeur;N. Hussain;Baoshan Chen;J. Testa;K. M. Scaboo;D. Jaisi;Qiang Li;M. Dai;J. Cornwell
我们于2016年6月调查了切萨皮克湾主航道沿着的碳酸盐系统，以阐明碳酸盐动力学和耗氧有机物的相关来源。使用两个端元混合计算，化学代理，和化学计量，我们表明，在初夏，溶解无机碳（DIC）的动态控制好氧呼吸的水柱（43%），硫酸盐还原在沉积物（39%），大气中的CO2入侵（13%），和CaCO 3溶解（5%）。DIC浓度及其稳定同位素的质量平衡表明，耗氧有机物的表观δ 13 C为−19.4 ± 0.3‰。颗粒有机物的整体组成也反映出藻类物质占主导地位（C/N = ~ 6，δ 13 C> −25‰）。因此，我们得出结论，原地有机质的分解（即，富营养化刺激的初级生产）是消耗氧气的主要过程，而外来有机物（陆地来源）对2016年6月缺氧区的氧气消耗贡献较小。这些发现在切萨皮克湾与另一个缺氧河口生态系统，在中国珠江口，外来有机物的显着贡献耗氧量。这两个系统之间的差异，在水文，有机质的数量和质量，和物理特性进行了讨论，以产生新的见解缺氧的形成和维持。在这两个系统中，本地有机质占主导地位的氧耗，表明营养管理和削减是有用的行动，以控制和缓解缺氧的发生，生态系统的恢复。
We surveyed the carbonate system along the main channel of the Chesapeake Bay in June 2016 to elucidate carbonate dynamics and the associated sources of oxygen‐consuming organic matter. Using a two endmember mixing calculation, chemical proxies, and stoichiometry, we demonstrated that in early summer, dissolved inorganic carbon (DIC) dynamics were controlled by aerobic respiration in the water column (43%), sulfate reduction in the sediment (39%), atmospheric CO2 invasion (13%), and CaCO3 dissolution (5%). A mass balance of the DIC concentration and its stable isotope suggested that the apparent δ13C of oxygen‐consuming organic matter was −19.4 ± 0.3‰. The bulk composition of particulate organic matter also reflected a dominance of algal material (C/N = ~ 6, δ13C > −25‰). Therefore, we concluded that the decomposition of autochthonous organic matter (i.e., eutrophication‐stimulated primary production) was the dominant process consuming oxygen, while allochthonous organic matter (terrestrially derived) made minor contributions to oxygen consumption in the hypoxic zone in June 2016. These findings in the Chesapeake Bay contrast with another hypoxic estuarine ecosystem, the Pearl River Estuary in China where allochthonous organic matter contributed significantly to oxygen consumption. The differences between these two systems in terms of hydrology, quantity and quality of organic matter, and physical characteristics are discussed to yield new insights on the formation and maintenance of hypoxia. In both systems, autochthonous organic matter dominates oxygen depletion, indicating that nutrient management and reduction are useful actions to control and mitigate the occurrence of hypoxia for the restoration of ecosystem.