Seasonal, Diurnal, and Tidal Variations of Dissolved Inorganic Carbon and pCO2 in Surface Waters of a Temperate Coastal Lagoon (Arcachon, SW France)

Type Article
Date 2023-01
Language English
Author(s) Polsenaere PierreORCID1, 2, Delille Bruno3, Poirier Dominique1, Charbonnier Céline1, Deborde JonathanORCID1, 2, Mouret Aurélia1, 4, Abril Gwenaël1, 5, 6
Affiliation(s) 1 : Laboratoire Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), CNRS-UMR 5805, Université de Bordeaux, Bordeaux, France
2 : IFREMER, Littoral, Laboratoire Environnement et Ressources des Pertuis Charentais (LER-PC), BP133, 17390, La Tremblade, France
3 : Département d’Astrophysique, Géophysique Et Océanographie, Unité Océanographie Chimique, Université de Liège, Allée du 6 Août, 17-Bât. B5 4000, Liège, Belgium
4 : UMR 6112 LPG-BIAF Recent and Fossil Bio-Indicators, Angers University, 2 Bd Lavoisier, F-49045, Angers, France
5 : Laboratoire de Biologie des Organismes et Écosystèmes Aquatiques (BOREA), UMR CNRS 8067, Muséum National d’Histoire Naturelle, 61 rue Buffon, 75231, Paris cedex 05, France
6 : Programa de Biologia Marinha e Ambientes Costeiros, Universidade Federal Fluminense, Outeiro São João Batista s/n, 24020015, Niterói, RJ, Brazil
Source Estuaries And Coasts (1559-2723) (Springer Science and Business Media LLC), 2023-01 , Vol. 46 , N. 1 , P. 128-148
DOI 10.1007/s12237-022-01121-6
Keyword(s) Coastal zone, Dissolved inorganic carbon, Water pCO(2), Water-air CO2 fluxes, Tidal, diurnal, seasonal variations, Physical, biological, chemical processes

We report on diurnal, tidal, and seasonal variations of dissolved inorganic carbon (DIC), water partial pressure of CO2 (pCO2), and associated water–air CO2 fluxes in a tidal creek of a temperate coastal lagoon with 70% of intertidal flats, during eight tidal/diurnal cycles and two consecutive years covering all seasons. Surface waters of the lagoon were always slightly oversaturated in CO2 with respect to the atmosphere with an average pCO2 value of 496 ± 36 ppmv. Seasonally, subsurface water pCO2 values were controlled by both temperature and biological/tidal advection effects that compensated each other and resulted in weak annual variations. High-resolution temporal pCO2 records reveal that the highest fluctuations (192 ppmv) occurred at the tidal/diurnal scale as a result of biological activity, advection from the tidal flat, and porewater pumping that all contributed to water pCO2 and carbonate chemistry variations. Total alkalinity (TA) versus salinity plots suggest a net production of alkalinity in the lagoon attributed to benthic carbonate dissolution and/or anaerobic degradation of organic matter. We specifically highlighted that for the same salinity range, during flooding, daytime pCO2 were generally lower than nighttime pCO2 values because of photosynthesis, whereas during ebbing, daytime pCO2 were higher than nighttime pCO2 values because of heating. Waters in the lagoon were a relatively weak CO2 source to the atmosphere over the year compared to other estuarine and lagoon waters elsewhere, and to sediment-air fluxes measured simultaneously by atmospheric Eddy Covariance (EC) in the Arcachon lagoon. Because of low values and small variations of the air-sea pCO2 gradient, the variability of fluxes calculated using the piston velocity parameterization was greatly controlled by the wind speed at the diurnal and, to a lesser extent, seasonal time scales. During the emersion, the comparison of these pCO2 data in the tidal creek with EC fluxes measured 1.8 km away on the tidal flat suggests high heterogeneity in air-sea CO2 fluxes, both spatially and at short time scales according to the inundation cycle and the wind speed. In addition to tidal pumping when the flat becomes emerged, our data suggest that lateral water movement during the emersion of the flat generates strong spatial heterogeneity in water–air CO2 flux.

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Polsenaere Pierre, Delille Bruno, Poirier Dominique, Charbonnier Céline, Deborde Jonathan, Mouret Aurélia, Abril Gwenaël (2023). Seasonal, Diurnal, and Tidal Variations of Dissolved Inorganic Carbon and pCO2 in Surface Waters of a Temperate Coastal Lagoon (Arcachon, SW France). Estuaries And Coasts, 46(1), 128-148. Publisher's official version : , Open Access version :