Influence of Tidal Inundation on CO₂ Exchange between Salt Marshes and the Atmosphere

Abstract. Salt marshes are among the most productive and dynamic ecosystems on Earth and globally sequester an average of 210 g C m⁻² yr⁻¹. To understand the role of this ecosystem in the carbon cycle and its changes as a result of rapid climate change and human disturbance, a baseline record particularly on carbon dioxide (CO₂) exchange between this ecosystem and atmosphere needs to be established. The goal of this study is to determine the effects tide events on the exchange of CO₂ in a salt marsh ecosystem dominated by Spartina alterniflora using the eddy-covariance method near Sapelo Island, GA. Two eddy-covariance systems were set up in July 2013 to capture 10 Hz data of CO₂. Results show that during daytime high tide events, a reduction of CO₂ exchange was observed. The conditions with a high tide to vegetation ratio had smaller CO₂ exchange when compared to conditions with a low tide ratio. Total daytime monthly reduction of CO₂ exchange for August 2014 was 15 %. A greater total reduction of CO₂ exchange of 40 % was recorded for high tide events with tide ratio of 0.75–1.0. In comparison of the effect of neap tide and spring tide on CO₂ exchange, neap tide days showed a greater CO₂ exchange as compared to spring tide days for May and October 2014, respectively. The inclusion of such results has implications to quantify the carbon budget and its changes as sea level rises.