325 / 2024-09-14 10:42:13

Molecular-level insights into dissolved organic matter during Ulva prolifera degradation and its regulation on the environmental behaviour of the organic pollutant tributyl phosphate

green tide,Organophosphate flame retardants,Dissolved organic matter,environmental behavior,FT-ICR MS

Macroalgal blooms have frequently occurred in coastal waters, and a large amount of algogenic dissolved organic matter (DOM) is input into seawater as macroalgae degraded. It undergoes continuous changes under microbial degradation; however, the impact of microbially-modified marine DOM on the environmental behaviour of organic pollutants remains underexplored. This study focused on Ulva prolifera, the dominant species in green tides, and investigated the molecular diversity of DOM from U. prolifera degradation over a 100-day period and the role of DOM at different time points in the adsorption of organophosphate flame retardants onto goethite. Our findings revealed that dissolved organic carbon (DOC) in seawater increased sharply during the first two weeks, followed by a rapid decline, and eventually reached a stable level within 100 days. Multi-spectrum and fourier transform ion cyclotron resonance mass spectrum (FT- CR-MS) revealed a gradual decrease in DOM bioavailability, an increase in humification and aromatization, and significant transformation of protein components. Microbial abundance aligned with DOC trends, and 16S rRNA results revealed significant shifts in the microbial community during DOM transformation. A strong correlation between fluorescent DOM groups and microbial diversity was observed, and co-occurrence network analysis further identified Alteromonas and Vibrio as major contributors to DOM chemical diversity. The introduction of U. prolifera DOM reduced available surface sites on goethite, inhibiting the adsorption rate of tributyl phosphate (TnBP) in batch sorption experiments. However, this competitive sorption effect was mitigated by co-sorption, as DOM could bind with TnBP, explaining the observed increase in adsorption capacity. Redundancy analysis and verification tests suggested protein-like DOM components play a crucial role in sorption, and microbial transformation of DOM-proteins could diminish this effect. These findings underscore the importance of microalgal DOM in influencing the environmental behaviour of organic pollutants.