Effects of the occurrence of green tide (Ulva prolifera blooms) on dissolved organic matters in the Southern Yellow Sea

Through the maritime survey data from multiple cruises in the southern Yellow Sea in 2017, the variations and influencing factors of dissolved organic matter in the process of green tide (Ulva prolifera blooms) were analyzed. The high-value areas of dissolved organic carbon (DOC) were mainly located in the northwestern part of the southern Yellow Sea and that near the northern Jiangsu, indicating that the terrigenous input was one of the main resources of DOC to this area. The EEMs-Parallel factor analysis (EEMs-PARAFAC) method identified four fluorescent dissolved organic matter (FDOM) in the southern Yellow Sea: three terrestrial humic-like (C1, C2, C3) and one protein-like (C4) fluorescent components. The spatial distributions of the four fluorescent components were similar and had a significant negative correlation with salinity. As the green tide outbroke in the southern yellow sea, DOC and FDOM concentrations increased significantly, while dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) concentrations were decreased. With the gradual disappearance of the green tide, the DOC concentration was going down but still slightly higher than that before the outbreak of green tide, instead the fluorescence intensities of C2 and C4 in surface waters were increased by 11.3% and 12.6%, respectively. During this period, DOP, DON and DON/DOC were also increased. The outbreak of the green tide in the South Yellow Sea had significant impacts on the spatiotemporal distribution of dissolved organic matter. © 2020, Editorial Board of China Environmental Science. All right reserved.