Geographical constraints on chemodiversity of sediment dissolved organic matter in China's coastal wetlands

Dissolved organic matter (DOM) plays an important role in wetland carbon cycle; however, the geographical pattern of DOM chemodiversity and controlling factors are not very clear for coastal wetland sediments, especially at large spatial scale. To this end, twenty China's coastal wetlands were surveyed on a national scale for their sediment DOM and related environmental parameters, and the DOM molecular compositions were resolved by Fourier transform ion cyclotron resonance mass spectrometry and relevant bioinformatics. The chemodiversity of a total of 14, 343 DOM molecular formulas showed a clear geographical pattern: a decrease with an increase in latitude. The moisture and organic matter contents of sediments were key factors controlling DOM chemodiversity and decreased with the increasing latitude. In addition, the sediment with higher DOM molecular chemodiversity contained more unsaturated compounds, and lignin-like and tannins increased with the decreasing latitude. This study highlights the molecular characteristics of sediment DOM in China's coastal wetlands and helps to deepen the geographical knowledge of coastal wetland DOM.