Description: The accumulation of anthropogenic CO2 in the oceans is altering seawater carbonate chemistry. Investigation and monitoring of the carbonate parameters is therefore necessary to understand potential impacts on ocean ecosystems. Total alkalinity (AT) and dissolved inorganic carbon (CT) were sampled across the Rockall Trough in Feb 2009 (CE0903) and Feb 2010 (CE10002) as part of a baseline study of inorganic carbon chemistry in Irish shelf waters. The results have been compared with data from WOCE surveys A01E (Sept 1991), A01 (Dec 1994), AR24 (Nov 1996) and A24 (June 1997). The 2009 and 2010 datasets provide a snapshot of the biogeochemical parameters which can act as a baseline of inorganic carbon and acidity levels in surface waters of the Rockall Trough in late winter for future comparison since previous surveys in the area have been affected by biological activity. The dataset also offers the possibility to compare decadal changes in subsurface waters. The temporal evolution of anthropogenic carbon (Delta C-ant) between the 1990s and 2010 was evaluated using two separate methods; (i) a comparison of the concentrations of C-T between surveys, after correcting it for remineralisation of organic material and formation and dissolution of calcium carbonate (Delta CT-abio) and (ii) an extended Multiple Linear Regression was used to calculate the Delta C-ant (Delta C-ant(eMLR)). There was an increase in Delta CT-abio and Delta C-ant(eMLR) of 18 +/- 4 mu mol kg(-1) and 19 +/- 4 mu mol kg(-1), respectively, in the subsurface waters between 1991 and 2010, equivalent to a decrease of 0.040 +/- 0.003 pH units over the 19 year period. There was an increase in both Delta CT-abio and Delta C(ant)e(mLR) of 8 +/- 4 mu mol kg(-1) in Labrador Sea Water (LSW) in the Trough between 1991 and 2010, and LSW has acidified by 0.029 +/- 0.002 pH units over the same time period. A reduction in calcite and aragonite saturation states was observed, which may have implications for calcifying organisms in the region

Description: Four contrasting coastal systems in Ireland, each with shellfish production activities, were studied to provide a first evaluation of the spatial and seasonal influences on the local carbonate system. The study sites included; (1) a coastal system with sandstone bedrock and minimal freshwater sources, (2) an estuarine system with a catchment limestone bedrock, (3) an estuarine system with a catchment granite bedrock, and (4) a karst groundwater-fed estuary. The type of bedrock was the dominant control on regional carbonate chemistry, where the calcium carbonate catchment bedrock was a strong source of both dissolved inorganic carbon and total alkalinity input in the two limestone regions, which are supersaturated with respect to atmospheric CO2 throughout the year. Primary production played an important role in the non-limestone regions, where both systems were CO2-undersaturated during productive months. Minimum aragonite saturation () was observed at all sites during winter when productivity is lowest; surface winter is 〈1.5 close to the mussel farms in Kinvara Bay and Bantry Bay. was recalculated to account for the higher calcium concentrations in the River Suir from limestone dissolution, which increases by 0.5 in the mid estuary and 〉2 in the inner estuary. The substrate-to-inhibitor ratio (SIR), an alternative indicator of ecosystem vulnerability to acidification, was positively correlated to in all systems, however with more variability in the two limestone regions. Results highlight challenges of assessing local ecosystem vulnerability to future acidification and the importance of understanding the local spatio-temporal biogeochemistry.