Contribution of riverine dissolved organic carbon to organic carbon decomposition in the Ariake Sea, Japan, a coastal area suffering from summer hypoxia
Contribution of riverine dissolved organic carbon to organic carbon decomposition in the Ariake Sea, Japan, a coastal area suffering from summer hypoxia
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DOI：
10.1007/s00027-022-00920-0
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发表时间：
2022-11
期刊：
影响因子：
2.4
通讯作者：
H. Takasu;T. Okamura;Tomohiro Komorita;Tomohiro Shiragaki;K. Uchino
中科院分区：
文献类型：
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作者：
H. Takasu;T. Okamura;Tomohiro Komorita;Tomohiro Shiragaki;K. Uchino
溶解有机碳（DOC）占河流有机碳入海通量的近一半。尽管河流DOC参与了许多重要的生态系统功能，但来自河流的DOC输入过多可能导致海岸系统缺氧。此外，许多方面的贡献河流DOC缺氧是未知的。有机质中天然碳稳定同位素比值（δ 13 C）可用于确定近岸海洋有机碳的来源。在这项研究中，我们分析了DOC的浓度和δ 13 C值的北方有明海，日本，其中缺氧水在夏季发展的底层。此外，我们比较了培养实验开始和结束时DOC的δ 13 C值，以确定河流DOC分解对缺氧的贡献。研究结果表明，夏季有明海西北部底层DOC浓度受浮游植物和河水的共同影响，其中浮游植物的影响可能更大。尽管如此，我们也发现主要的贡献（~ 49.7%）DOC分解总有机碳分解在一些站。DOC的初始δ 13 C值为-24.0 ‰ ~-22.2 ‰，培养后有3个培养瓶的DOCδ 13 C值增加（从+0.3 ‰增加到+0.8 ‰）。这可能是由于贫13 C有机质的选择性分解所致。这些瓶子中的分解DOC必须主要来自陆源。这一结果表明，河流DOC分解有助于缺氧的形成在北方有明海底层。
Dissolved organic carbon (DOC) comprises nearly half of the riverine organic carbon flux into oceans. Although riverine DOC is involved in numerous important ecosystem functions, excessive labile DOC inputs from rivers may contribute to hypoxia in coastal systems. Furthermore, many aspects of the contribution of riverine DOC to hypoxia are unknown. The natural carbon stable isotope ratio (δ13C) in organic matter can be used to identify sources of organic carbon in coastal oceans. In this study, we analyzed the concentrations andδ13C values of DOC in the bottom layer of the northern Ariake Sea, Japan, in which hypoxic water develops during summer. Additionally, we compared theδ13C values of DOC at the beginning and end of an incubation experiment to determine the contribution of riverine DOC decomposition to hypoxia. The results of this study indicate that the bottom DOC concentration is influenced by both phytoplankton and river water, with the former likely having a stronger impact in the northwestern Ariake Sea in summer. Nevertheless, we also found major contributions (~ 49.7%) of DOC decomposition to total organic carbon decomposition at some stations. The initialδ13C value of DOC ranged from − 24.0 to − 22.2‰, and the DOCδ13C increased (from + 0.3 to + 0.8‰) in three of the five incubation bottles after incubation. This might be caused by selective decomposition of13C-depleted organic matter. The decomposed DOC in those bottles must be mainly derived from terrestrial sources. This result implies that riverine DOC decomposition contributes to hypoxia formation in the bottom layer of the northern Ariake Sea.