The effect of a strong hurricane on carbon export from the largest contiguous mangrove forest in North America

Mangroves, one of the most productive ecosystems on Earth, are an important link between land and ocean and are crucial for moderating carbon fluxes to the ocean in the tropics and sub-tropics. Besides their vulnerability to sea-level rise and other human-induced changes, they are regularly exposed to hurricanes. Here we studied the impact of Hurricane Irma on dissolved organic and inorganic carbon (DOC and DIC) fluxes in the mangrove estuary of Shark River in the Everglades National Park, the largest mangrove estuary in North America. We found that both DIC and DOC fluxes decreased severely directly after Irma made landfall as a Category 4 hurricane. The DIC flux recovered quickly, while the DOC flux remained lower up to two months after Irma. Besides the change in absolute numbers, we found that the contribution of estuarine (i.e., mangrove root respiration and calcite dissolution) vs non-estuarine (i.e., from upstream of the estuary) sources to DIC decreased considerably at the site closer to the ocean after the hurricane. Although both DIC and DOC fluxes were still lower up to two years after Irma, the high inter- and intra-variability of both fluxes made it difficult to draw solid, long-term conclusions.