<scp>CDOM</scp> spectral slope (<scp><i>S</i></scp>_275–295) as tracers of water masses, <scp>CDOM</scp> heterogeneity, and <scp>Δ¹⁴C‐DOC</scp> in an oligotrophic marginal sea

The absorption spectral slope, S275–295, is an optical metric frequently employed for characterizing chromophoric dissolved organic matter (CDOM). We collected CDOM (aCDOM) and fluorescence spectra from the oligotrophic offshore South China Sea to identify major determinant of S275–295 explore potential as physical biogeochemical tracers. linearly decreased with increasing humic-like fluorescent DOM, revealing latter primary control on S275–295. variability consistently declined surface deep water, making a indicator molecular heterogeneity. vs. aCDOM plot was found be useful tool water masses. 14C content carbon (Δ14C-DOC) shows strong correlation demonstrating proxy 14C-age DOM. A provisional equation, ln(−Δ14C-DOC) = (−0.85 ± 0.06) × ln(S275–295) + (8.78 0.19), proposed estimate Δ14C-DOC global oceans.