The bioavailability and component characteristics of the aging dissolved organic matter (DOM) from the macroalgae Ulva prolifera in seawater

Xinyu Li; Cui Zeng; Xiurong Han; Xiulin Wang; Keqiang Li

doi:10.1016/j.marenvres.2025.106946

The bioavailability and component characteristics of the aging dissolved organic matter (DOM) from the macroalgae Ulva prolifera in seawater

Mar Environ Res. 2025 Jan 3:204:106946. doi: 10.1016/j.marenvres.2025.106946. Online ahead of print.

Authors

Xinyu Li¹, Cui Zeng¹, Xiurong Han², Xiulin Wang¹, Keqiang Li³

Affiliations

¹ Key Laboratory of Marine Chemistry Theory and Technology, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ministry of Education, Ocean University of China, Qingdao, 266100, China; College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, 2066061, China.
² College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, 2066061, China. Electronic address: [email protected].
³ Key Laboratory of Marine Chemistry Theory and Technology, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ministry of Education, Ocean University of China, Qingdao, 266100, China; College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, 2066061, China. Electronic address: [email protected].

PMID: 39756245
DOI: 10.1016/j.marenvres.2025.106946

Abstract

The world's largest green tide, caused by Ulva prolifera, in the Yellow Sea negatively affects the social and economic development of China's coastal region. The dissolved organic matter (DOM) released from U. prolifera is a potential threat to the offshore ecological health. The bioavailability and component characteristics of the DOM from U. prolifera vary at different aging stages in marine environments and are poorly understood. Here, a 1-year incubation experiment was conducted to understand this phenomenon. The bioavailable DOM (BDOM) mainly comprised the labile bioavailable DOM (LBDOM), which accounts for 58.7% (in dissolved organic nitrogen (DON)%) in the aging stages of 0-12 days. LBDOM mainly comprised three-dimensional fluorescent tyrosine B and tryptophan T components. The semi-labile bioavailable DOM (SLBDOM) accounted for 29.2% in the aging stages of 12-80 days, which mainly comprised fulvic acid C1 and A components. Both LBDOM and SLBDOM mainly contained amine groups in their structures. Conversely, the refractory bioavailable DOM (RBDOM) accounted for only 6.50% in the aging stages of 80-365 days. RBDOM mainly comprised a humin-like acid C2 component, whereas refractory dissolved organic matter (RDOM) mainly comprised humin-like acid C2, E, and fulvic acid A components, and the structures of both mainly included functional groups, such as hydroxyl, carboxyl, alkynyl, and aromatic rings. The hydrophobic component and dissolved organic carbon (DOC) proportion increased with the aging of DOM in seawater. Thus, the aging of DOM in seawater represents the processes of aromatization, hydrophobization, and humification, wherein the SUVA₂₅₄, SUVA₂₆₀, and humification index (HIX) increased by 55.7, 42.9, and 133.0%, respectively. The results of our study contribute to a deeper understanding of the ecological effects of DOM released during the extinction process of U. prolifera in the ocean.

Keywords: Aging; Bioavailability; Component characterization; Dissolved organic matter (DOM); Ulva prolifera.