Influence of Daytime Tide Events on CO2 Exchange between Salt Marsh and Atmosphere

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. The ecosystem is very dynamic, which responds to changing environmental conditions such as sea-level rise, tidal range and coastal engineering. In order to understand the role of this ecosystem in the carbon cycle and its changes as a result of rapid climate change and human disturbance, we need a baseline record particularly on CO₂ exchange between this ecosystem and atmosphere. The goal of this study is to determine the effects of daytime tide events on the exchange of CO₂ in salt marsh ecosystem dominated by Spartina alterniflora using eddy-covariance method. The study was conducted at Sapelo Island, GA. Two eddy covariance systems were set up in July 2013 to capture 10 hz data of CO₂. Three layers of signal processing and data quality screening were applied to the dataset and 30-min fluxes of CO₂ were calculated. Tide ratio (ratio of tide height to plant height; tide ratio ≥ 1, plant is completely submerged; tide ratio = 0, plant is totally exposed to the air) was established to determine the effect of both tide and plant heights on CO₂ exchange. During daytime high tide events, a reduction of CO₂ exchange was observed. The conditions with high tide ratio had smaller CO₂ exchange when compared to conditions with low tide ratio.