Contribution of the degradation of different hygrophytes to chromophoric dissolved organic matter during the inundation period

Hygrophytes play a key role in maintaining the structure and function of wetland and lake ecosystems. A large number of hygrophytes are submerged and decompose during the flooding period in wetlands and lakes and then release dissolved organic matter (DOM). However, few studies have explored changes in DOM composition and concentration caused by hygrophyte decomposition during the inundation period. A 66-day degradation experiment was conducted using three typical wetland plant species, i.e., Carex cinerascens , Artemisia selengensis , and Phalaris arundinacea , to analyze the optical characteristics of their biodegradation products . The concentration of dissolved organic carbon (DOC) significantly increased with A. selengensis and C. cinerascens decomposition. Plant decomposition significantly decreased the absorption ratio at 250 nm to 365 nm ( a 250 / a 365 ). Furthermore, the humification index (HIX) significantly increased with C. cinerascens and P. arundinacea decomposition. The high biological index (BIX) was likely caused by the rapid decomposition of autochthonous components. We identified two humic-like substances (components 1 and 2) and two protein-like substances (components 3 and 4) during the degradation processes. The fluorescence intensities (F max ) of protein-like substances in the A. selengensis treatment and C. cinerascens / P. arundinacea treatments were significantly different . A time effect was observed for variations in DOC, BIX, and component 3, and an interactive effect of time with plant species was observed for variations in DOC, HIX, and humic-like substances. These results provide insight into the optical characteristics and composition of DOM released by hygrophytes. Our findings have important implications for the effect of hygrophyte decomposition on DOM composition and water quality in wetlands and lakes.