Baseline temperature amplifies warming-induced shifts in sediment metal(loid) lability across element-specific response regimes.

Climate warming is expected to reshape sediment-associated metal behavior, yet whether warming responses of sediment metal(loid) lability are systematically regulated by baseline thermal conditions remains unresolved. Here, we combined diffusive gradients in thin films (DGT) measurements with controlled sediment incubations across 0-40 °C to quantify temperature-dependent lability responses of multiple metal(loid)s in coastal sediments. Distinct element-specific response regimes emerged. Redox-sensitive elements (Mn, V, and As) exhibited nonlinear increases in DGT-labile concentrations with warming, cobalt showed transitional non-monotonic behavior, whereas most particle-associated metal(loid)s displayed monotonic declines. These contrasting responses indicate that warming does not uniformly enhance sediment metal(loid) lability but reorganizes reactive metal behavior in patterns consistent with element-specific differences in solid-phase resupply and retention. Despite divergent element-specific trends, identical warming perturbations consistently induced larger relative lability changes at lower baseline temperatures. Model-based sensitivity analysis further showed that proportional warming responses were amplified under cold baseline conditions, identifying baseline temperature as a first-order regulator of sediment metal(loid) responsiveness to warming. This baseline-temperature control implies that climate warming may redistribute sediment contaminant sensitivity across thermal regimes, with cold coastal sediments exhibiting disproportionate geochemical responses. Our results provide a process-based framework linking warming, element-specific resupply kinetics, and sediment metal(loid) lability, and highlight baseline temperature as a critical but previously underrecognized control on contaminant dynamics at the sediment-water interface.