Open ocean carbonate chemistry is altered by the dissolution of atmospheric CO2 in seawater. Up to 40% of anthropogenic CO2 emissions have been dissolved in the surface ocean, driving changes in the marine carbonate system and promoting ocean acidification. In the open ocean Total Alkalinity (TA) shows strong correlation with salinity and temperature due to the conservative nature of its constituents there. However, in coastal areas the interaction with the continent makes these relations much more complex. Freshwater inputs can provide an additional source of TA and Dissolved Inorganic Carbon (DIC) to the coast or lower them through dilution. The aim of this study is to understand the impact of land-ocean interactions over the coastal carbonate system and therefore, over local ocean acidification processes. The Marine Institute has provided a large dataset with several surveys along the Irish coastline, from 2009 to 2018, measuring TA, DIC and nutrients (nitrate NO3−, nitrite NO2−, phosphate PO43− and silicate SiO4−). In order to understand whether the watershed geology or the land-usage can influence the coastal chemistry, the original dataset was at first reduced to have a set of variables comparable in different locations. Principal Component Analysis (PCA) was then performed. Contrasting continental influence over the coastal carbonate system was observed, which was related to the geology of the catchment area. Elucidating how land-ocean interactions affect the coastal carbonate system would help to understand coastal resilience to ocean acidification and thus support better management of coastal resources.