Lingering Carbon Cycle Effects of Hurricane Matthew in North Carolina's Coastal Waters

In 2016, Hurricane Matthew accounted for 25% of the annual riverine C loading to the Neuse River Estuary-Pamlico Sound, in eastern North Carolina. Unlike inland watersheds, dissolved organic carbon (DOC) was the dominant component of C flux from this coastal watershed and stable carbon isotope and chromophoric dissolved organic matter evidence indicated the estuary and sound were dominated by wetland-derived terrigenous organic matter sources for several months following the storm. Persistence of wetland-derived DOC enabled its degradation to carbon dioxide (CO2), which was supported by sea-to-air CO2 fluxes measured in the sound weeks after the storm. Under future increasingly extreme weather events such as Hurricane Matthew, and most recently Hurricane Florence (September 2018), degradation of terrestrial DOC in floodwaters could increase flux of CO2 from estuaries and coastal waters to the atmosphere. Plain Language Summary Recent hurricanes along the Southeastern and Gulf coasts of the United States have received much attention, because these extreme events have led to immense societal and economic impacts. Wetlands in coastal watersheds store large amounts of organic matter and upon flooding during extreme weather events are poised to release this material into adjacent rivers and estuaries where its decomposition can generate carbon dioxide. Alteration of carbon balances in these events can shift impacted coastal ecosystems from states of carbon sinks to carbon sources for periods of weeks to months. Understanding the balance between these states is important to our understanding of how, and how long, regional carbon cycling is impacted after such extreme weather events. A biweekly record of dissolved and particulate organic matter quantity and quality from a coastal watershed in North Carolina in the 3months following Hurricane Matthew in 2016 illustrated a major input of wetland carbon to coastal waters caused by this storm and its substantial lingering effect on coastal carbon cycling.