The impact of typhoons on the biogeochemistry of dissolved organic matter in eutrophic bays in northwestern South China Sea

• Published in: Acta oceanologica Sinica Vol. 43; no. 6; pp. 15 - 31
• Main Authors: Lu, Xuan, Lao, Qibin, Chen, Fajin, Jin, Guangzhe, Chen, Chunqing, Zhu, Qingmei
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.06.2024; Springer Nature B.V
• Subjects: Bays; Biogeochemistry; Carbon sources; Climatology; Decomposition; Dissolved organic matter; Earth and Environmental Science; Earth Sciences; Ecology; Engineering Fluid Dynamics; Environmental Chemistry; Estuaries; Eutrophic rivers; Eutrophication; Hurricanes; Marine & Freshwater Sciences; Marine Chemistry; Microorganisms; Nutrients; Oceanography; Particulate matter; Particulate organic matter; Seawater; Suspended particulate matter; Typhoons; South China Sea; dissolved organic matter; typhoon; decomposition; northwestern South China Sea; optical analyses
• ISSN: 0253-505X; 1869-1099
• DOI: 10.1007/s13131-023-2283-6

Highly productive estuaries facilitate intense decomposition of dissolved organic matter (DOM) as a carbon source. However, the specific impacts of typhoons on DOM decomposition in eutrophic bays remain unclear. To address this issue, we investigated the spectral characteristics of DOM before and after Typhoon Ewiniar in Zhanjiang Bay, a eutrophic semi-enclosed bay in the northwestern South China Sea. The results revealed that intense microbial decomposition of DOM occurred during the pre-typhoon period because high nutrient inputs facilitated the mobilization of DOM in the bay. However, the intrusion of external seawater induced by the typhoon diluted the nutrient levels in Zhanjiang Bay, reducing the impact of microbial decomposition on DOM during the post-typhoon period. Nevertheless, the net addition of DOM occurred in Zhanjiang Bay during the post-typhoon period, possibly because of the decomposition of particulate organic matter (POM) and desorption of particulate matter. In addition, an increase in apparent oxygen utilization, a decrease in DO saturation and the reduced level of Chl a indicated that organic matter (OM) decomposition was enhanced and OM decomposition shifted to POM decomposition in Zhanjiang Bay after the typhoon. Overall, our study highlighted the shift in the intense OM decomposition from DOM to POM decomposition before and after typhoons in eutrophic bays, providing new insights into the response of typhoons to biogeochemistry.