A Review of Climate-Modulated Redistribution of Trace Elements in the Black Sea: A Framework for Monitoring and Risk Assessment in Semi-Enclosed Seas

Climate change is modifying the physical structure and biogeochemical functioning of stratified marine systems, with important consequences for trace element (TE) transport, speciation, and exposure. The Black Sea provides a structurally amplified case because restricted exchange, persistent stratification, a basin-scale redoxcline, and extensive shelf-sediment reservoirs intensify climate–contaminant interactions. This review synthesizes mechanistic evidence to develop a climate-informed interpretive framework for TE redistribution under non-stationary environmental forcing. We examine how warming, deoxygenation, hydrological variability, sediment resuspension, acidification, and episodic events alter TE partitioning across dissolved, particulate, sedimentary, and biotic compartments. The synthesis identifies six major redistribution pathways involving surface-layer retention, river plume and suspended particulate transport, shelf-sediment remobilization, redoxcline dynamics, acidification–ligand effects, and event-driven exposure pulses. Together, these processes show that TE patterns increasingly reflect state-dependent internal redistribution rather than external loading alone. To address this shift, we propose a monitoring and risk-interpretation framework that links climate-sensitive state variables to redistribution pathways, integrates multiple matrices, and supports adaptive assessment through trigger-based monitoring escalation. The Black Sea is treated as a structurally amplified reference system for examining climate-sensitive redistribution pathways in stratified basins, although their expression and relative importance remain dependent on basin-specific structural controls.