Biogeochemical responses to a tropical storm in an eroding estuary of the Mississippi river delta plain

Abstract

The impact of abrupt hydrological changes due to extreme weather events on estuarine carbon cycling and transport remains poorly understood. This study investigates the changes in sources and transport of dissolved (DOC) and particulate organic carbon (POC) along the land‐estuary‐ocean continuum of the Barataria Basin estuary system, located south of Louisiana after hurricane Francine. Pre‐ and post‐storm samplings were carried out for POC, DOC, dissolved inorganic carbon (DIC) and colored dissolved organic matter (CDOM) to assess the impact of storm on estuarine carbon dynamics. DOC ranged from 2.2 to 13.3 and 4.6 to 12.0 mg/L while POC ranged from 1.5 to 4.6 and 3.4 to 7.1 mg/L during pre‐ and post‐storm periods, respectively. Lower humification index (HIX) and aCDOM ₃₅₀ suggest a transition from older, more degraded DOM to fresher, newer, more labile DOM after storm. Primary production and respiration rates both increased in the bay after the storm. The change in δ ¹³ C of sediment organic carbon showed increased terrestrial organic matter input and ⁷ Be approach indicated recent sediment deposition in the basin. COAWST, a computer simulation model was implemented to compute the change in discharge rates due to storm which coupled with DOC and POC analysis indicate that 60.7 and 76.4 tons of additional POC and DOC were exported from this relatively small estuary within 5 d after landfall of hurricane Francine. This study highlights the impact of storms on carbon transport in eroding deltaic estuaries, emphasizing the need to incorporate storm‐driven carbon fluxes into regional and global carbon budgets.