AUTHOR=Fichot Cédric G. , Benner Ronald , Kaiser Karl , Shen Yuan , Amon Rainer M. W. , Ogawa Hiroshi , Lu Chia-Jung TITLE=Predicting Dissolved Lignin Phenol Concentrations in the Coastal Ocean from Chromophoric Dissolved Organic Matter (CDOM) Absorption Coefficients JOURNAL=Frontiers in Marine Science VOLUME=3 YEAR=2016 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2016.00007 DOI=10.3389/fmars.2016.00007 ISSN=2296-7745 ABSTRACT=

Dissolved lignin is a well-established biomarker of terrigenous dissolved organic matter (DOM) in the ocean, and a chromophoric component of DOM. Although evidence suggests there is a strong linkage between lignin concentrations and chromophoric dissolved organic matter (CDOM) absorption coefficients in coastal waters, the characteristics of this linkage and the existence of a relationship that is applicable across coastal oceans remain unclear. Here, 421 paired measurements of dissolved lignin concentrations (sum of nine lignin phenols) and CDOM absorption coefficients [ag(λ)] were used to examine their relationship along the river-ocean continuum (0–37 salinity) and across contrasting coastal oceans (sub-tropical, temperate, high-latitude). Overall, lignin concentrations spanned four orders of magnitude and revealed a strong, non-linear relationship with ag(λ). The characteristics of the relationship (shape, wavelength dependency, lignin-composition dependency) and evidence from degradation indicators were all consistent with lignin being an important driver of CDOM variability in coastal oceans, and suggested physical mixing and long-term photodegradation were important in shaping the relationship. These observations were used to develop two simple empirical models for estimating lignin concentrations from ag(λ) with a ±20% error relative to measured values. The models are expected to be applicable in most coastal oceans influenced by terrigenous inputs.