Artificial reefs promote coastal carbon stabilization potential through hydrological condition and microbial pathways

Artificial reefs (ARs) reshape near-bed hydrodynamics and benthic microbial functions, yet links to coastal carbon stabilization remain insufficiently resolved. Here, we combined hydrodynamic modeling with sediment geochemistry, fluorescence spectroscopy, and metagenomics across contrasting AR habitats in the northern Yellow Sea. Structurally complex ARs enhanced upwelling and wake turbulence and were associated with finer sediments and higher sediment total organic carbon (TOC). Path modeling showed that hydrodynamic indices, hydrographic state variables, and microbial functional gene profiles jointly explained spatial variations in sediment TOC and humic-like fluorescent. During a 42-day dark incubation, protein-like fluorescent dissolved organic matter (FDOM) fractions declined while the humic-like component (C2) increased, indicating net enrichment of humic-like byproducts during microbial reworking of labile DOC. Microbial succession included increased relative abundance of ammonia oxidizing archaea (e.g., Crenarchaeota, Nitrososphaeria), and the SAR202 clade, accompanied by higher functional potentials related to aromatic-compound transformation and nitrogen redox pathways. Collectively, these results support a framework in which AR-induced hydrodynamic modulation couples with nitrogen-redox linked microbial functions, promoting carbon stabilization potential reflected by humic-like DOM enrichment and benthic carbon storage proxies.