Pore water exchange?driven inorganic carbon export from intertidal salt marshes

Respiration in intertidal salt marshes generates dissolved inorganic carbon (DIC) that is exported to the coastal ocean by tidal exchange with marsh platform. Understanding link between physical drivers of water and chemical flux a key constraining wetland contributions regional budgets. The spatial temporal (seasonal, annual) variability pore DIC export was assessed from microtidal (Sage Lot Pond, Massachusetts). Spatial constrained 224Ra : 228Th disequilibria across two hydrologic units within sediments. Disequilibrium more soluble its sediment-bound parent reveals significant upper 5 cm surface (0–36 L m?2 d?1) most intense low elevation zones, driven overtopping. Surficial sediment transport ranges 0.0 0.7 g C d?1. sub-surface horizon intersected mean tide disproportionately impacted pumping (20–80 supplied seasonal 1.7–5.4 Export exceeded 10 d?1 for another unit, demonstrating fluxes can vary substantially under similar conditions same estuary. Seasonal annual exchange, time-series radium isotopes, part sea level. Rising levels will further inundate high which may lead greater export.