2004. ESTUARIES 27(2) In press.

Changes in Saltmarsh Surface Elevation Due to Variability in Evapotranspiration and Tidal Flooding


   Abstract -- We examine the potential for diurnal variation in elevation of saltmarsh surfaces as a source of error in long-term experiments; errors particularly critical in high precision studies that employ the surface elevation table (SET) as a means to monitor elevations. The field study was carried out along the New Brunswick coast of the Bay of Fundy in high and low zones at three marshes with different tidal ranges. We employed a total of 16 benchmark pipes and controlled for daily variability in evapotranspiration (ET), as well as timing of tidal flooding, two factors that affect soil water storage, and consequently soil volume. In six of nine trials we detected significant elevation change over periods as short as five days. Marsh-wide averages ranged from 1.2 to 3.0 mm, greater than the yearly increase in relative sea level in many regions. Wood Point marsh had the highest tidal range, but lowest soil organic matter content, thus its soils had the lowest compressibility and showed little sensitivity to ET during two of three trials. Despite this, the average change in elevation in Wood Point high marsh stations was 4.0 mm during the last trial. Greater differences later in the growing season (while temperature changes were minor) at Wood Point and another site suggest that plant transpiration drove changes in water storage at those sites. However, significantly greater differences in elevation with lower plant cover in the third marsh suggests that evaporation drove changes in water storage there. We conclude that surface elevation change due to ET should be of greatest concern to SET users in temperate regions where there are large changes in plant biomass and variable temperatures. Variation due to plant transpiration could be reduced if yearly monitoring is scheduled before the start of the growing season.

2003. Estuarine Research Federation.