Porewater exchange is usually the least quantified process in delivering dissolved material from wetlands to coastal waters, although it has been recognized as an important pathway for the transport of carbon, nutrients and trace metals to the ocean. Here, surface water fluxes of dissolved manganese (Mn), iron (Fe), dissolved organic/inorganic carbon (DOC/DIC), total dissolved nitrogen (TDN) and phosphorous (TDP) were estimated from a temperate mangrove wetland (Kooragang Island, Newcastle, NSW, Australia). Radon, a natural groundwater tracer was used to construct a mass balance model to quantify porewater exchange rates and evaluate the porewater-derived material contribution to the overall wetland Surface water export. A 25-h time series dataset depicted a clear peak of Mn, Fe, TDN, DOC and radon during ebb tides which related to porewater discharge. Porewater exchange rates were estimated to be 14.0 ± 6.3 cm/d, mainly driven by tidal pumping, and facilitated by a large number of crab burrows at the site. Results showed that the wetland was a source of Mn, Fe, TDN and DOC to the adjacent river system and a sink for TDP and DIC. Surface water Mn, Fe, TDN and DOC exports were 4 ± 1, 150 ± 57, 21 ± 5 and 107 ± 29 mmol/m2 wetland/d, respectively. Porewater-derived Mn, Fe, TDN and DOC accounting for ~ 95, 100, 89 and 54% of the wetland surface water exports demonstrating the important role of porewater exchange in driving dissolved material export from the mangrove wetland. Additionally, mangrove porewater delivered at least 2 orders of magnitude greater TDN and DOC to the coastal ocean compared to the much larger river system. Our study indicates that temperate mangrove wetlands can be a major source of dissolved material to coastal waters and that mangrove porewater exchange should be accounted for in coastal trace metal, carbon and nutrient budgets.