Articles | Volume 14, issue 9
Research article
17 May 2017
Research article |  | 17 May 2017

Dissolved carbon biogeochemistry and export in mangrove-dominated rivers of the Florida Everglades

David T. Ho, Sara Ferrón, Victor C. Engel, William T. Anderson, Peter K. Swart, René M. Price, and Leticia Barbero

Abstract. 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 was examined in these rivers during SF6 tracer release experiments. Approximately 80 % of the total dissolved carbon flux out of the Shark and Harney rivers during these experiments was in the form of inorganic carbon, either via air–water CO2 exchange or longitudinal flux of dissolved inorganic carbon (DIC) to the coastal ocean. Between 42 and 48 % of the total mangrove-derived DIC flux into the rivers was emitted to the atmosphere, with the remaining being discharged to the coastal ocean. Dissolved organic carbon (DOC) represented ca. 10 % of the total mangrove-derived dissolved carbon flux from the forests to the rivers. The sum of mangrove-derived DIC and DOC export from the forest 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 Shark and Harney rivers, mangrove contribution to the estuarine flux of dissolved carbon to the ocean is less than 10 %.

Short summary
Mangroves take up more carbon (C) than any other ecosystems, but > 50 % of this C is missing. The forest loses organic C to the surrounding waters, which might be rapidly transformed into inorganic C. Previous studies focused on organic C could have missed this important sink. We examined the sources and sinks of dissolved C in two mangrove estuaries, and confirmed that ca. 90 % of the total dissolved mangrove-derived C flux flowing out of the estuaries was inorganic C.
Final-revised paper