Aragonite saturation state in a continental shelf (Gulf of Cádiz, SW Iberian Peninsula): Evidences of acidification in the coastal area

The spatiotemporal variability of aragonite saturation state (ΩAr) has been studied in the eastern shelf Gulf Cádiz (GoC) (SW Iberian Peninsula). study was carried out during years 2014 and 2016 aboard twelve oceanographic cruises, along three or five transects, located between Cape Trafalgar Guadiana River. GoC exhibited oversaturated calcium carbonate with ΩAr mean values 2.68 ± 0.30 surface 2.05 0.15 deep waters. pH, total alkalinity (TA), concentration (Ca 2+ ) showed a high within mixed layer (SML, z < 100 m). Biological activity seemed to be main process determine SML, revealing greater importance than temperature, mixing air-sea processes. buffer factors CO 2 system have estimated SML waters, they are related biological temperature changes. A decrease pH this depth observed, due increase respiratory In waters (z > m), TA Ca presented conservative behaviour distribution different water masses GoC. vertical variation also depends on degree mineralization these masses, obtaining maximum Subtropical North Atlantic Central Water (100–200 minimum Subpolar (about 400 intermediate associated presence Mediterranean (>500 Results significative acidification coastal areas, for those depths lower m from 2006 2016, −0.0089 −0.0552 yr −1 , respectively. • Hydrodinamical conditions spatial processes control changes SML. lowest NACW P . decreased areas 2016.