Journal d'océanographie et de recherche marine
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Variability and Transport of Inorganic Carbon Dioxide in a Tropical Estuary

Ramos e Silva CA, Davalos PB, Silva MP, Miranda LB, Calado L

Marine ecosystems are a known net source of greenhouse gases emissions. On the other hand, the geochemical fluxes, particularly from the developing countries estuarine areas, are poorly evaluated. In the present study, temporal and longitudinal water samplings were taken hourly and seasonally during full semidiurnal tidal-cycles, along the Caravelas estuary, located in northeast region of Brazil. It was analyzed the pH, total alkalinity, aragonite saturation state, calcite saturation state, dissolved inorganic carbon, aqueous CO₂ and partial pressure of CO₂ found in estuarine waters. Results showed that the total alkalinity values decreased from the estuary mouth up-river during the dry season, which reflects the low buffering capacity of river water. The estuarine total alkalinity and dissolved inorganic carbon fluxes were significantly higher in the dry season during the spring tide. The spring and neap tides were typically oversaturated with CO₂ in both the dry and rainy seasons. The highest average values were found in the dry season for both the neap and spring tides, while the CO₂ air-water flux values throughout the dry and rainy seasons, retained a positive variation range. Finally, the annual surface water flux of dissolved inorganic carbon revealed to be positive suggesting dissolved inorganic carbon exportation to coastal water.