The Shark and Harney Rivers, located on the southwest coast of Florida, USA, originate in the freshwater, karstic marshes of the Everglades and flow through the largest contiguous mangrove forest in North America. In November 2010 and 2011, dissolved carbon source-sink dynamics were examined in these rivers during SF 6 tracer release experiments. Approximately 80 % of the total dissolved carbon flux from all sources (i.e., freshwater wetlands, mangrove, carbonate dissolution, and marine input) out of the Shark and Harney Rivers during these experiments was as inorganic carbon, either via air-water CO 2 exchange or longitudinal flux of inorganic carbon to the coastal ocean. Of the total mangrove-derived dissolved inorganic carbon (DIC) exported from the forests into these rivers, between 42 and 48 % was emitted to the atmosphere, with the remaining discharged to the coastal ocean. Dissolved organic carbon (DOC) represented ca. 10 % of the total mangrove-derived dissolved carbon export from the forests. The sum of mangrove-derived DIC and DOC export to these rivers was estimated to be at least 18.9 to 24.5 mmol m −2 d −1 , a rate lower than other independent estimates from Shark River and from other mangrove forests. Results from these experiments also suggest that in this region, mangrove contribution to the estuarine flux of dissolved carbon to the ocean is less than 10 %.