Review of the migration and transformation of reservoir mineral-associated organic carbon (MAOC)

Mineral-associated organic carbon (MAOC) plays an important role in reservoir carbon cycling and carbon sink function. This review synthesizes recent advances in the migration and transformation of MAOC in reservoirs from two complementary perspectives: migration, involving adsorption–desorption, hydrodynamic transport, flocculation, sedimentation, and water–sediment regulation; and transformation, involving microbial processing, redox regulation, and long-term burial. It clarifies the pathways of MAOC input, transport, release, decomposition, and preservation and summarizes the coupled influences of hydrological conditions, sediment properties, physicochemical environments, biological activity, and reservoir operation on MAOC dynamics. Available evidence indicates that reservoir MAOC dynamics are jointly regulated by particle-size sorting, organo–mineral interactions, oxygen and redox conditions, microbial activity, and anthropogenic regulation, which together determine whether MAOC is stabilized and buried or remobilized and transformed. Differences in MAOC migration and transformation between reservoirs and rivers are also discussed. Current research remains limited by insufficient mechanistic coupling, inadequate dynamic quantification, and limited cross-scale integration. Future studies should strengthen long-term observations, controlled experiments, and coupled water-sediment-carbon modeling to improve the assessment and prediction of reservoir carbon sink functions under changing environmental conditions.