| Summary: | Progress Code: completed Carbonate chemistry data for the antFOCE seawater samples. The download file contains an Excel spreadsheet with a number of worksheets detailing the samples collected from O'Brien Bay, Casey Station. The dataset includes information on oxygen levels, pH levels, temperature and salinity levels, as well as the concentrations of various elements (dissolved inorganic carbon, phosphate, nitrate, nitrite, silicate). Free-ocean CO2 enrichment (FOCE) experiments have been deployed in marine ecosystems to manipulate carbonate system conditions to those predicted in future oceans. We investigated whether the pH/carbonate chemistry of extremely cold polar waters can be manipulated in an ecologically relevant way, to represent conditions under future atmospheric CO2 levels, in an in-situ FOCE experiment in Antarctica. We examined spatial and temporal variation in local ambient carbonate chemistry at hourly intervals at two sites between December and February and compared these with experimental conditions. We successfully maintained a mean pH offset in acidified benthic chambers of -0.38 (plus or minus 0.07) from ambient for approximately 8 weeks. Local diel and seasonal fluctuations in ambient pH were duplicated in the FOCE system. Large temporal variability in acidified chambers resulted from system stoppages. The mean pH, Ωarag and fCO2 values in the acidified chambers were 7.688 plus or minus 0.079, 0.62 plus or minus 0.13 and 912 plus or minus 150 micro-atm respectively. Variation in ambient pH appeared to be mainly driven by salinity and biological production and ranged from 8.019 to 8.192 with significant spatio-temporal variation. This experiment demonstrates the utility of FOCE systems to create conditions expected in future oceans that represent ecologically relevant variation, even under polar conditions.
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