Molecular-level composition of dissolved organic matter in distinct trophic states in Chinese lakes: Implications for eutrophic lake management and the global carbon cycle

•DOM changes along trophic gradient lakes were characterized by optical properties and FT-ICR MS.•More S-containing and polycyclic aromatic materials were observed in eutrophic lakes.•More aliphatic compounds were detected in eutrophic lakes.•Eutrophication modifies the structure of DOM into more complex materials.•CDOM could serve as a potential predictor of lake eutrophication.