CO₂ efflux from mangrove tree trunks represents an important yet understudied component of carbon cycling in tidal forests. An assessment of trunk emissions was conducted for Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa across contrasting salinity conditions on the Ajuruteua Peninsula, Brazilian Amazon coast. Measurements of CO₂ efflux, trunk temperature, bark thickness, and diameter allowed evaluation of the environmental and anatomical controls on respiratory fluxes. Results revealed marked interspecific variation in emission rates, strongly influenced by trunk temperature and tree size, while bark thickness acted as a physical constraint on diffusion. Although salinity showed no consistent linear relationship with trunk efflux, emissions were generally higher at intermediate salinity, suggesting a threshold response along the tidal gradient. Extrapolation to the forest scale highlights the relevance of trunk respiration to blue carbon budgets. These findings reinforce the need to integrate stem efflux processes into mangrove carbon-flux assessments, particularly under changing climatic and hydrological regimes.