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

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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.