河口盐沼水体溶解态有机质的动态变化特征及降解转化机理——以上海崇明东滩盐沼湿地为例

doi:10.3969/j.issn.1000-5641.2025.02.006

摘要/Abstract

摘要：

作为海岸带生态系统的重要组成, 河口盐沼拥有巨大的碳储量, 是全球蓝碳碳汇的主要贡献者. 盐沼水体中溶解态有机质 (Dissolved Organic Matter, DOM) 的含量和光谱特性在潮汐交换和季节更替等不同因素的作用下呈现高动态变化. 聚焦受长江影响下的上海崇明东滩盐沼湿地, 通过在不同季节开展一个完整潮汐周期内的高频采样, 以盐沼水体中的DOM为研究对象, 刻画了盐沼水体的DOM含量 (以DOM中的碳元素含量表示, 即溶解态有机碳 (Dissolved Organic Carbon, DOC) 浓度) 和光谱特性 (以DOM中有色溶解有机物 (Chromophoric DOM, CDOM) 的光吸收特性表示) 在潮汐周期和季节尺度中的动态变化. 结果表明, 在潮汐周期尺度上, 相较于涨潮时的水体, 落潮时的盐沼水体具有较高的DOC浓度、较强的紫外吸收 (${a_{{\rm{CDOM}}}} $(350)和${a_{{\rm{CDOM}}}^*} $(350))、较高的芳香度 (Specific Ultraviolet Absorbance, SUVA₂₅₄) 以及较低的光谱斜率 (S_275-295). 在季节尺度上, 相较于冬季和春季, 夏季和秋季落潮时的盐沼水体具有较高的DOC浓度、较强的紫外吸收、较高的芳香度以及较低的光谱斜率. 夏季盐沼水体的培养实验结果表明, 在5 d的培养周期内, 光化学降解是移除盐沼水体中CDOM的主要因素, 而微生物作用则显著影响了水体中DOM的整体含量. 研究结果有助于增进对河口盐沼通过侧向输送过程输出溶解态有机质的动态变化及其降解转化机理的理解.

关键词: 河口盐沼, 溶解有机碳, 有色溶解有机物, 潮汐交换, 生物地球化学循环

Abstract:

Estuarine wetlands are important components of coastal ecosystems that contribute tremendously to global blue carbon sinks. The amount and quality of dissolved organic matter (DOM) vary significantly with tidal exchange and seasonal cycles. Focusing on the Chongming Dongtan salt marshes in Shanghai under the influence of the Yangtze River, we conducted high-frequency sampling across a complete tidal cycle in each season and characterized the dynamics of the quantity (expressed by the C content in DOM, i.e., the concentration of dissolved organic carbon (DOC)) and spectral characteristics (expressed by the light absorption characteristics of chromophoric DOM (CDOM)) of DOM across tidal and seasonal scales. The results indicated that on the tidal scale, waters leaving the marshes during the ebbing tide were rich in DOC, strong in optical absorbance (${a_{{\rm{CDOM}}}} $(350) and ${a_{{\rm{CDOM}}}^*} $(350)), with high aromaticity (specific ultraviolet absorbance, SUVA₂₅₄) and low spectral slope (S_275-295), compared to water entering the marshes during the flooding tide. On a seasonal scale, waters in the ebbing tide during summer and fall had elevated DOC concentrations, high absorption and aromaticity, and correspondingly lower spectral slopes relative to waters collected in winter and spring. The results of on-site incubation experiments demonstrated that photochemical degradation was the major process that removed the colored fraction from the DOM pool, whereas microbial processing played an important role in affecting the bulk DOM. This study helps improve our understanding of the dynamics of marsh DOM and the mechanisms of its degradation processes associated with lateral transport from estuarine marshes to adjacent estuaries.

Key words: estuary salt marshes, dissolved organic carbon, chromophoric dissolved organic matter, tidal exchange, biogeochemical cycle

中图分类号:

P748

李润, 陈洁南, 陈灏, 曹芳. 河口盐沼水体溶解态有机质的动态变化特征及降解转化机理——以上海崇明东滩盐沼湿地为例[J]. 华东师范大学学报（自然科学版）, 2025, 2025(2): 55-67.

Run LI, Jienan CHEN, Hao CHEN, Fang CAO. Dynamic characteristics and degradation transformation mechanism of dissolved organic matter in estuarine wetlands: A case study of Chongming Dongtan salt marsh wetland in Shanghai[J]. J* E* C* N* U* N* S*, 2025, 2025(2): 55-67.

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季节	采样时间	潮汐状况	潮差/m	样品数量/个
季节	采样时间	潮汐状况	潮差/m	CDOM	DOC
早春	2023年2月10—11日	小潮	1.49	25	25
夏季	2022年6月13—14日	大潮	2.32	17	17
秋季	2022年9月16—17日	小潮	1.57	25	25
冬季	2021年12月18—19日	大潮	1.21	25	25
合计				92	92

培养实验	${a_{{\rm{CDOM}}}} $(350)/m^–1	c_DOC/(mg·L^–1)	S_275-295/nm^–1	${a_{{\rm{CDOM}}}^*} $(350)/(m²·g^–1)
培养前 (t = 0)	8.37	6.78	0.016	1.23
光化学降解 (A组)	6.23 ± 0.02	6.04 ± 0.16	0.017 ± 0.0001	1.03 ± 0.03
微生物降解 (B组)	7.77 ± 0.14	6.02 ± 0.11	0.016 ± 0.00004	1.29 ± 0.02
光化学 + 微生物降解 (C组)	6.10 ± 0.13	6.07 ± 0.07	0.018 ± 0.0003	1.01 ± 0.02
对照组 (避光 + 去除微生物影响, D组)	7.81 ± 0.07	6.25 ± 0.10	0.016 ± 0.0001	1.25 ± 0.01

研究区域	c_DOC/(mg·L^–1)	S_275-295/nm^–1	SUVA₂₅₄/(L·mg^–1·m^–1)	参考文献
美国Kirkpatrick盐沼湿地	春季: 2.9 ~ 7.1; 夏季: 4.4 ~ 713.5; 秋季: 3.4 ~ 711.2	N/A	N/A	[21]
美国北卡罗来纳州东部盐沼湿地	5月: 9.6 ± 2.6; 7月: 11.7 ± 2.8; 8月: 10.0 ± 2.4; 10月: 10.4 ± 2.1	N/A	N/A	[19]
新英格兰尼庞西特盐沼湿地	春季: 3.6 ± 1.44; 夏季: 4.56 ± 0.84; 秋季: 4.68 ± 0.96; 冬季: 3.12 ± 2.88	N/A	N/A	[56]
崇明西沙盐沼湿地	春季: 2.23; 夏季: 4.10; 秋季: 2.70; 冬季: 1.78 夏季强降雨后 LT: 6.87 夏季洪水事件后: 2.97	夏季 LT: 0.0169 ± 0.0002	夏季 LT: 5.31 ± 0.06	[55]
上海九段沙盐沼湿地	春季: 2.06 ± 0.77; 夏季: 2.81 ± 0.98; 秋季: 2.70 ± 0.85; 冬季: 1.67 ± 0.94	夏季 LT: 0.0167 ± 0.0002	夏季 LT: 6.85 ± 0.11	[55]
崇明东滩盐沼湿地	春季: 2.64 ± 0.83; 夏季: 3.04 ± 1.26; 秋季: 2.50 ± 0.84; 冬季: 2.39 ± 0.33	夏季 LT: 0.0169 ± 0.0007	夏季 LT: 5.37 ± 0.12	本研究

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