Wang Chao, Jiang Kuan, Wang Xin, Huang Peng, Liu Pengfei, Chen Fajin, Jin Guangzhe
College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang, China; Key Laboratory of Water Environment Simulation and Pollution Control, Ministry of Ecology and Environment of the People's Republic of China, China; Laboratory for Coastal Ocean Variation and Disaster Prediction, College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang, China; Key Laboratory of Climate, Resources and Environment in Continental Shelf Sea and Deep Sea of Department of Education of Guangdong Province, Guangdong Ocean University, Zhanjiang, China; College of Chemistry and Environmental Science, Guangdong Ocean University, Zhanjiang, China.
College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang, China; College of Chemistry and Environmental Science, Guangdong Ocean University, Zhanjiang, China.
Mar Environ Res. 2025 Sep;210:107340. doi: 10.1016/j.marenvres.2025.107340. Epub 2025 Jul 3.
Accurately estimating coastal carbon budgets requires a comprehensive understanding of dissolved organic matter (DOM) inputs from both groundwater discharge and river runoff, particularly in small, human-impacted tropical watersheds. This study provides a representative watershed surrounding Zhanjiang Bay in the northern South China Sea to broaden current knowledge in this field. By characterizing the spatiotemporal dynamics of water quality parameters, dissolved organic carbon (DOC), and both chromophoric and fluorescent DOM (CDOM and FDOM), we identified key patterns in DOM composition, sources, fluxes, and human-induced shifts. DOM in groundwater and river water around Zhanjiang Bay exhibited pronounced spatial heterogeneity but limited seasonal variation. Principal component and Cluster analyses identified three distinct groups. Cluster 1 represents shallow, oxygen-rich groundwater systems from cultivated land and artificial surfaces, with low DOM and microbially processed features. Cluster 2 comprises low-oxygen groundwater from grassland and wetland areas, marked by elevated DOC and humic-like FDOM, reflecting stronger terrestrial and anthropogenic inputs. Cluster 3 includes three rivers from urbanized catchments, enriched in DOC and protein-like FDOM from both anthropogenic and biological sources. Despite comparable water volumes, groundwater contributed less labile DOM flux than rivers. Riverine DOM showed a shift toward DOC-rich but CDOM-poor signature under human influence, deviating from natural tropical patterns and becoming similar to those of anthropogenically impacted rivers in northern China, indicating reduced stability and long-term carbon storage potential in marginal seas.
准确估算沿海碳收支需要全面了解来自地下水排放和河流径流的溶解有机物（DOM）输入，特别是在受人类影响的小型热带流域。本研究提供了中国南海北部湛江湾周边一个具有代表性的流域，以拓宽该领域的现有知识。通过表征水质参数、溶解有机碳（DOC）以及发色和荧光DOM（CDOM和FDOM）的时空动态，我们确定了DOM组成、来源、通量和人为引起的变化的关键模式。湛江湾周边地下水和河水中的DOM表现出明显的空间异质性，但季节变化有限。主成分分析和聚类分析确定了三个不同的组。第1组代表来自耕地和人工表面的浅层、富氧地下水系统，DOM含量低且具有微生物处理特征。第2组包括来自草地和湿地地区的低氧地下水，其特征是DOC和类腐殖质FDOM含量升高，反映了更强的陆地和人为输入。第3组包括来自城市化集水区的三条河流，富含来自人为和生物来源的DOC和类蛋白质FDOM。尽管水量相当，但地下水贡献的不稳定DOM通量比河流少。在人类影响下，河流DOM呈现出向富含DOC但贫CDOM特征的转变，偏离了自然热带模式，变得与中国北方受人为影响的河流相似，这表明边缘海的稳定性和长期碳储存潜力降低。
