Aragonite saturation, dissolved inorganic carbon and pH variability in Marietas Islands, a fringing reef in the Mexican Pacific

Mariana Cupul1, Jose Martin Martin Hernandez-Ayon2, Orion Norzagaray3, Amilcar Levi Cupul-Magaña Sr.4 and Paola Rodríguez-Troncoso4, (1)Autonomous University of Baja California, Instituto de Investigaciones Oceanologicas, Ensenada, BJ, Mexico, (2)Autonomous University of Baja California UABC, Instituto de Investigaciones Oceanológicas, Ensenada, Mexico, (3)Universidad Autonoma de Baja California UABC, Instituto de Investigaciones Oceanológicas, Ensenada, BJ, Mexico, (4)Universidad de Guadalajara, Laboratorio de Ecología Marina, Puerto Vallarta, JA, Mexico
The aim of this work was to study for the first time, the seasonal variability of seawater CO2 system along a year by dissolved inorganic carbon (DIC), pHsws and total alkalinity (TA) measurements in two sites at the Islas Marietas National Park (IMNP). Two oceanographic conditions were found at the site: 1) a period with the presence of Tropical Surface Water (TSW), was characterized by high temperature (30°C) and low DIC levels (< 2000 µmol kg-1), also high pHsws (~8.1) and aragonite saturation ΩAr (~3.2) values, associated with the wet season. Otherwise, in the dry season, with the presence of evaporated TSW high DIC levels (>2050 µmol kg-1), low pHsws (~7.93) and ΩAr (~2.7) values were observed. On the other hand, satellite images of sea surface temperature showed the influence of upwelling events at the site between January and May, which explains the lowest pHsws (~7.7) and ΩAr (~1.9) values and highest DIC (2145 µmol kg-1) levels observed during the sampling period. Our results highlighted that fringing corals in Marietas, are acclimated to live under wide ranges of temperature (~14ºC), pHsws (0.3) and ΩAr (2.1) units throughout the year, which does not compromise their grown or development.