Salt marsh hydrology: Implications for biogeochemical fluxes to the atmosphere and estuaries

TLDR: A comprehensive water balance study in a New England salt marsh reveals that evapotranspiration and infiltration during tidal inundation and precipitation are the dominant hydrological processes in the sediment on a marsh-wide scale as mentioned in this paper.

Abstract: Rates of gas emissions and solute fluxes from salt marsh sediments are influenced by sediment hydrology. A comprehensive water balance study in a New England salt marsh reveals that evapotranspiration and infiltration during tidal inundation and precipitation are the dominant hydrological processes in the sediment on a marsh-wide scale. Water loss by drainage through the sediment into tidal creeks is effectively limited to within 10 m to 15 m of the creek bank; however, drainage is responsible for 40% of the water loss within 10 m of the creek during nonflooding, neap tide periods. The rate and extent of advective transport by pore water drainage is controlled by the topography of the marsh surface. Tidal fluctuations in creek level drive larger, oscillating water fluxes across the creek bank, which results in a dispersive transport of the solutes in the sediment, but these fluxes are attenuated in the first meter. Convexities in the marsh surface, for example, the crests of the creek banks, are the location of maximum water loss by drainage and probably the highest degree of desaturation and aeration, which can, in turn, increase gas emissions locally. The spring-neap tide cycle modulates wetting and drying of the sediment and, by inference, gas emissions in the interior of the marsh. The limited extent of solute transport by drainage implies that an as yet undescribed mechanism is responsible for controlling the concentration of conservative solutes in salt marshes.