Unravelling saltmarsh organic carbon sources: biomarker-isotopic integration for credible blue carbon accounting

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S0341816226005540?via%3Dihub

Authors: Jinge Zhou, Hua He, Han Chen, Jingfan Zhang, Zhe Lu et al.

26 June 2026

Highlights

•Integrates n-alkanes and amino sugars to quantify five organic carbon sources.

•Reveals that local halophytes contribute 37.7–58.6% of saltmarsh sedimentary carbon.

•Provides a verifiable framework for blue carbon credit certification and allocation.

•Informs wetland restoration strategies to prioritize autochthonous plant productivity.

Abstract

Saltmarshes are vital coastal blue carbon (C) ecosystems (BCEs) that store large amounts of organic C (OC) in sediments. This OC originates from both local (autochthonous) and external (allochthonous) marine or terrestrial sources. Accurately quantifying these OC sources is crucial for effectively allocating blue C credits. In this study, we investigated the sources of sedimentary organic carbon (SOC) in two representative Chinese saltmarshes, each characterized by distinct vegetation communities (Spartina alterniflora, Suaeda salsa, and Phragmites australis). By integrating n-alkane signatures (plant sources) and amino sugars (microbial necromass) with δ13C-N/C analysis, we quantify five distinct OC sources: autochthonous plant-derived halophytes OC, allochthonous terrestrial xylophyta OC, and allochthonous marine algae OC, as well as microbial-derived fungal necromass C, and bacterial necromass C. The analysis revealed that plant residues predominate in the SOC, contributing over 75%. Notably, autochthonous untransformed plant-derived OC consistently constituted the highest proportion, ranging from 36.9% to 58.2%. Furthermore, soil texture and nutrient composition were key factors regulating plant- and microbial-derived OC, with distinct pathways mediating these effects. Isotopic validation confirmed biomarker reliability. Our results provide a methodological basis for improving source-resolved blue carbon accounting in saltmarshes, although broader application requires local endmember calibration and consideration of uncertainty.

Source: ScienceDirect