HR: 0800h
AN: OS51C-0571    [Abstracts]
TI: Indirect Measurements of Air-Water CO₂ Exchanges in a Tropical Coastal Area
AU: * Bonnaud, E
EM: elodie@hawaii.edu
AF: SOEST-Dept of Geochemistry, Univ. of Hawaii 1000, Pope Road, Honolulu, HI 96822 United States
AU: Paquay, F
EM: paquay@hawaii.edu
AF: SOEST-Dept of Geochemistry, Univ. of Hawaii 1000, Pope Road, Honolulu, HI 96822 United States
AU: De Carlo, E
EM: edecarlo@soest.hawaii.edu
AF: SOEST-Dept of Geochemistry, Univ. of Hawaii 1000, Pope Road, Honolulu, HI 96822 United States
AU: Mackenzie, F
EM: fredm@soest.hawaii.edu
AF: SOEST-Dept of Geochemistry, Univ. of Hawaii 1000, Pope Road, Honolulu, HI 96822 United States
AB: Depending on the latitude, coastal ecosystems (including reefs, estuaries, swamps, springs and rivers) behave differently with regard to CO₂ flux between water surface and the atmosphere. Tropical areas are estimated to behave as sources for the atmosphere but are the poorest documented. We carried out a study focussed on such areas between April and July 2005 near the town of Kailua (21°40N-157°70W), Oahu, Hawai'i (USA). pH, total alkalinity, temperature and salinity were monitored at different sites in the water surface layer, to derive information on the carbonate system and estimate the magnitude of the CO₂ exchange at the water/atmosphere interface. The difference between atmospheric and oceanic CO₂ partial pressure (Δ p_{CO_2}=pCO_2-pCO_2atmos) at each monitoring sites was calculated using the carbonate system calculation program designed by C. Frankignoulle (2001). Measurements were made from the estuary to fresh-water springs, but also in a tidal swamp. For all of them positive Δ p_{CO_2} were calculated, indicating that this whole system behaves as a source for the atmosphere in term of CO₂. Δ p_{CO_2} in the estuary and fresh-water rivers ranges between 0 and 5000 μatm as commonly observed in such situations. Very high Δ p_{CO_2} are reported (up to 70000~μatm) in the tidal swamp, featuring important spatial and temporal variability. The eastern and western side of the swamp behave differently, with larger Δ p_{CO_2} in the water from the western (30000 ± 25000~μatm) than the eastern (8000 ± 4000~μatm) side of the swamp. It is hypothesized that such high fluxes of CO₂ result from an interaction between the marine calcerous grounds with water and also from the high rate of organic matter degradation associated with high water temperature. Our observations confirm that intertropical coastal areas generally behave as CO₂ sources for the atmosphere. However, the large variability in the fluxes magnitude deserves to be studied more thoroughly in order to assess the globally integrated role of such areas in the perspective of an increasing CO₂ load in the atmosphere.
DE: 4217 Coastal processes
DE: 4803 Analytical chemistry
DE: 4805 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912)
DE: 4806 Carbon cycling (0428)
DE: 4835 Marine inorganic chemistry (1050)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005