Dynamic of aragonite saturation horizon in waters of Baja California, Mexico

The status of the ocean acidification can be estimated by hydrographic calibrated data with carbon system variables. Recently empirical models for the coast of southern California and northern Baja California were developed. These models can be applied mainly in places where hydrographic data exist but also with measurements of the carbon system available for calibrations. The aim of this study was to analyze the hydrographic data of a transect in front of Ensenada’s coast, corresponding to the line 100 of IMECOCAL’s program during the period 1998-2014. Such data was used to apply an empirical model to estimate the aragonite saturation state (Ωa) in order to identify oceanographic conditions that could influence the variability of the depth of saturation horizon that might be in the last 17 years in habitats of shellfish and oyster production areas adjacent to the coast of Ensenada. It was found that the temperature, salinity, oxygen, pH, dissolved inorganic carbon and Ωa showed a seasonal variation with different oceanographic scenarios: (a) during spring-summer the California Current flow to the Ecuador and upwelling events are presented; (b) in autumn-winter the influence the Southern California Bight Eddy can transport water from the subarctic to Ecuador in the oceanic portion of the transect and towards the pole at the coastal side. These oceanographic characteristics encourage that coastal stations present seasonal variability, reflected in the depth of the horizon Ωa shallower (~ 66m + 21m) in spring and deeper into the winter (~ 122m + 35). It has been reported that the upwelling off the coast of BC transport water from a depth between 80 and 90m in spring and summer; therefore under saturated water (Ωa <1) may be transported to the platform upwelling off the coast of BC