Water record of Magallana angulata F0 generation exposed to low pH during laboratory experiments in 2020

The basic observed water characteristics (pH, temperature, salinity and total alkalinity (TA)) and calculated water carbonate chemistry in the hatchery located in Zhanjiang, China (21.07°N, 110.74°E). The two-year-old Portuguese oysters Magallana angulata (also known as Crassostrea angulata) were collected from Wuchuan, China (21.37°N, 110.74°E). To be specific, about 300 adult oysters were transferred into six black fibreglass tanks (500L each) randomly and each culture tank contained about 50 individuals. Six tanks were independent and completely randomized to be separated into two different pH levels: ambient pH 8.0~8.1 as control (named F0_8.1) and pH 7.4 as ocean acidification (OA) treatment (named F0_7.4) for about one month to produce next generation and test for transgenerational effect. Low pH was driven by bubbling of carbon dioxide (CO₂) enriched air mixed with ambient air into filter seawater in the treatment tanks. pH and temperature were monitored daily with pH meter (Mettler Toledo InLab®, Switzerland) calibrated with NBS standards. Salinity was monitored using a dual-scale refractometer (MingRui, China). The seawater was utterly changed every two days and 50 mL seawater was preserved with mercury dichloride (HgCl2) every week for total alkalinity (TA) measurement. The TA was measured using an alkalinity titrator (Mettler Toledo G20S Compact Titrator, Switzerland), and partial pressure of carbon dioxide (pCO₂), carbonate ion (CO₃²⁻), saturation states of calcite and aragonite were calculated by CO2SYS program with equilibrium constants K2 and KSO4 (Millero et al. 2006).