Ecosystem-atmosphere interactions in a New England salt marsh (PIE LTER)

Analyzing the response of salt marsh vegetation to tidal influences is important to understand if or how they can adapt to changes in sea level. Marshes keep their position to the relative sea level by sediment accretion and accumulation of organic matter. Both processes are dependent on relative elevation and vegetation cover as well as flooding frequency and intensity.

To study marsh metabolism, we chose the non-intrusive eddy covariance method which is supplemented by measurements of lateral C transport. In this on-going study, we are investigating the marsh-atmosphere exchange of carbon dioxide at a Spartina patens high marsh at the Plum Island LTER. The energy balance closure for most tidal cycles is about 80%, but becomes more variable during spring tidal cycles when the high marsh platform is flooded.  During spring tides we also observed a significant impact of tidal flooding on carbon fluxes.  Both daytime carbon uptake and night time respiration were reduced during flooding spring tides.  A similar decrease in fluxes has been described at a S. alterniflora marsh at the Virginia Coastal Reserve LTER at high tide events during midday. Measurements of tidal carbon fluxes will help determine how much of the reduction in atmospheric fluxes is due to metabolic changes and how much is due to the exchange of carbon between the marsh and water.