Temporal variability of the carbonate system and air-sea CO2 exchanges in a Mediterranean human-impacted coastal site

Type Article
Date 2020-05
Language English
Author(s) Wimart-Rousseau Cathy1, Lajaunie-Salla Katixa1, Marrec Pierre6, Wagener Thibaut1, Raimbault Patrick1, Lagadec Véronique1, Lafont Michel1, Garcia Nicole1, Diaz Frédéric1, Pinazo Christel1, Yohia Christophe4, Garcia Fabrice1, Xueref-Remy Irène2, Blanc Pierre-Eric3, Armengaud Alexandre5, Lefèvre Dominique1
Affiliation(s) 1 : Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO, UM 110, 13288, Marseille, France
2 : Aix Marseille Univ, Avignon Université, CNRS, IRD, Institut Méditerranéen de Biodiversité et d'Ecologie Marine et Continentale (IMBE), Marseille, France
3 : Observatoire de Haute Provence, OSU Pythéas, France
4 : Aix Marseille Univ., Université de Toulon, CNRS, IRD, OSU Institut Pythéas, 13288, Marseille, France
5 : AtmoSud: Observatoire de la Qualité de l'air en Région Sud Provence Alpes Côte d’Azur, le Noilly Paradis, 146 Rue Paradis, 13294, Marseille, Cedex 06, France
6 : University of Rhode Island, Graduate School of Oceanography, Menden-Deuer Lab, Narragansett, RI, 02882, USA
Source Estuarine Coastal And Shelf Science (0272-7714) (Elsevier BV), 2020-05 , Vol. 236 , P. 106641 (13p.)
DOI 10.1016/j.ecss.2020.106641
WOS© Times Cited 9
Keyword(s) Coastal biogeochemistry, CO2 fluxes, Carbonate system, North Western Mediterranean Sea, Bay of Marseille

The temporal evolution of the carbonate system and air-sea CO2 fluxes are investigated for the first time in the Bay of Marseille (BoM – North Western Mediterranean Sea), a coastal system affected by anthropogenic forcing from the Marseille metropolis. This study presents a two-year time-series (between 2016 and 2018) of fortnightly measurements of AT, CT, pH and derived seawater carbonate parameters at the SOLEMIO station. On this land-ocean boundary area, no linear relationship between AT and salinity in surface water is observed due to sporadic intrusions of freshwater coming from the Rhone River. On an annual scale, the BoM acts as a sink of atmospheric CO2. This result is consistent with previous studies in the Mediterranean Sea. Mean daily air-sea CO2 fluxes range between −0.8 mmol C.m−2.d−1 and -2.2 mmol C.m−2.d−1 during the study period, depending on the atmospheric CO2 sampling site used for the estimates. This study shows that the pCO2 in the surface water is predominantly driven by temperature changes, even if partially counterbalanced by biological activity. Therefore, temperature is the main contributor to the air-sea CO2 exchange variability. Mean daily Net Ecosystem Production (NEP) estimates from CT budget shows an ecosystem in which autotrophic processes are associated with a sink of CO2. Despite some negative NEP values, the observed air-sea CO2 fluxes in the BoM are negative, suggesting that thermodynamic processes are the predominant drivers for these fluxes.

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Wimart-Rousseau Cathy, Lajaunie-Salla Katixa, Marrec Pierre, Wagener Thibaut, Raimbault Patrick, Lagadec Véronique, Lafont Michel, Garcia Nicole, Diaz Frédéric, Pinazo Christel, Yohia Christophe, Garcia Fabrice, Xueref-Remy Irène, Blanc Pierre-Eric, Armengaud Alexandre, Lefèvre Dominique (2020). Temporal variability of the carbonate system and air-sea CO2 exchanges in a Mediterranean human-impacted coastal site. Estuarine Coastal And Shelf Science, 236, 106641 (13p.). Publisher's official version : https://doi.org/10.1016/j.ecss.2020.106641 , Open Access version : https://archimer.ifremer.fr/doc/00609/72120/