The electrode (A157, Schott Instruments, Mainz, Germany) was three-point calibrated with NBS certified standard buffers and the measurement uncertainty was 0.03 pH units. TA was determined by potentiometric titration (Dickson 1981; TitroLine alpha plus, Schott Instruments). Measurements were accuracy-corrected with certified reference materials (CRMs) supplied by A. Dickson (Scripps Institution of Oceanography, USA). Calculation of the carbonate system was performed using CO2sys (Pierrot et al. 2006). Input parameters Selleck AZD6244 were pHNBS and TA, as well as temperature (15 °C), salinity (32.4), and pressure (1 dbar, according

to 1 m depth; Hoppe et al. 2012). For all calculations, phosphate and silicate concentrations were assumed to be 7 and 17 μmol kg−1, respectively, based on assessments of the media. Equilibrium constants for carbonic acid, K1 and K2 given

by Mehrbach et al. (1973) and refit by Dickson and Millero (1987) were used. For the dissociation of sulfuric acid, the constants reported by Dickson (1990) were employed. Table 1 Carbonate chemistry selleck chemical of the pCO2 acclimations at the time of harvesting and in cell-free media (reference); Attained pCO2, DIC, HCO3 −, CO3 2−, and Ωcalcite are calculated based on measured pHNBS and TA using CO2sys (Pierrot et al. 2006) Strain, ploidy Treatment pCO2 (μatm) Attained pCO2 (μatm) pHNBS TA (μmol kg−1) DIC (μmol kg−1) CO2 (μmol kg−1) HCO3 − (μmol kg−1) CO3 2− (μmol kg−1) Ωcalcite RCC 1216, 2N Low, 380 353 ± 8 8.19 ± 0.02 2,259 ± 19 2,023 ± 15 13 ± 0 1,857 ± 13 161 ± 3 3.9 ± 0.1 High, 950 847 ± 55 7.86 ± 0.04 2,278 ± 20 2,156 ± 2 32 ± 2 2,060 ± 28 84 ± 4 2.0 ± 0.1 RCC 1217, 1N Low, 380 345 ± 4 8.23 ± 0.00 2,317 ± 12 2,068 ± 10 13 ± 0 1,885 ± 10 170 ± 1 4.1 ± 0.0 High, 950 837 ± 25 7.89 ± 0.01 2,317 ± 3 2,210 ± 5 32 ± 1 2,092 ± 5 86 ± 3 2.1 ± 0.1 Cell-free medium Low, 380 405 ± 3 8.17 ± 0.00 2,304 ± 5 2,092 ± 5 15 ± 0 1,926 ± 5 151 ± 1 3.7 ± 0.0 High, 950 997 ± 17 7.82 ± 0.01 2,305 ± 7 2,214 ± 12

38 ± 1 2,128 ± 11 75 ± 1 1.8 ± 0.0 Results are reported for 15 °C (n ≥ 3; ± SD) Cell buy Paclitaxel growth was assessed by daily cell counting with a Multisizer III hemocytometer (Beckman-Coulter, Fullerton, CA, USA) and the specific growth rates (μ) were calculated from daily increments (cf., Rokitta and Rost 2012). For the determination of total particulate carbon (TPC), POC and particulate organic nitrogen (PON), cell suspensions were vacuum-filtered (-200 mbar relative to atmosphere) onto pre-combusted (12 h, 500 °C) GF/F filters (1.2 μm; Whatman, Maidstone, UK), which were dried at 65 °C and analyzed with a EuroVector CHNS-O elemental analyzer (EuroEA, Milano, Italy). Before quantification of POC, filters were HCl-soaked (200 μL, 0.2 M) and dried to remove calcite. PIC was assessed as the difference between TPC and POC. By multiplying the POC and PIC cell quotas with μ, the respective production rates were derived (cf., Rokitta and Rost 2012).